Jason Gao Internet Draft Software Architect Intended status: Informational January 3, 2018 Expires: July 2018 Flexible Session Protocol draft-gao-flexible-protocol-00 Abstract FSP is a connection-oriented transport layer protocol that provides mobility, multihoming and multipath load balancing support by introducing the concept of 'upper layer thread ID', which was firstly suggested in [Gao2002]. It provides additional transport layer features such as ubiquitous message authentication with optional encryption, zero round-trip connection cloning, transmit transaction and quad-party shared secret installation facility. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. 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Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents Status of this Memo .............................................. 1 Copyright Notice ................................................. 2 Table of Contents ................................................ 2 1. Introduction .................................................. 5 2. Conventions and Definitions.................................... 6 3. Key Mechanisms ................................................ 8 3.1. Underlying Layer Services Required ........................ 8 3.1.1. High Mobility ........................................ 8 3.1.2. Packet Delivery ...................................... 9 3.2. Upper Layer Thread Identifier and Integrity Check Code ..... 9 3.3. Transmit Transaction Facility ............................ 10 3.4. Quad-party Session Key Installation Sub-protocol .......... 10 Gao Expires July 3, 2018 [Page 2] Internet-Draft Flexible Session Protocol January 2018 3.5. Zero round-trip connection cloning ....................... 11 4. Packet Structure ............................................. 12 4.1. FSP over UDP/IPv4 ........................................ 12 4.2. FSP over IPv6 ........................................... 13 4.3. FSP Header and Header Signature .......................... 14 4.4. Operation Code .......................................... 15 4.5. Preliminary FSP Packet ................................... 17 4.5.1. Connect Initialization .............................. 17 4.5.2. Acknowledgment to Connect Initialization ............ 19 4.5.3. Connect Request ..................................... 20 4.6. Normal Fixed Header ...................................... 21 4.7. Sink Parameter .......................................... 23 4.8. Selective Negative Acknowledgment ........................ 25 4.9. RESET ................................................... 26 5. The Finite States ............................................ 27 5.1. NON_EXISTENT ............................................ 27 5.2. LISTENING ............................................... 27 5.3. CONNECT_BOOTSTRAP ........................................ 27 5.4. CHALLENGING ............................................. 28 5.5. CONNECT_AFFIRMING ........................................ 28 5.6. ACTIVE{A.K.A. ESTABLISHED} ............................... 28 5.7. COMMITTING .............................................. 29 5.8. PEER_COMMIT ............................................. 29 5.9. COMMITTING2 ............................................. 29 5.10. COMMITTED .............................................. 30 5.11. CLOSABLE ............................................... 30 5.12. PRE_CLOSED ............................................. 31 5.13. CLOSED ................................................. 31 5.14. CLONING ................................................ 31 5.15. {Cloned} ............................................... 32 6. End-to-End Negotiation ........................................ 32 6.1. Init Check Code, Salt and Cookie ......................... 32 6.2. Connect Initialization ................................... 33 6.3. Response to Connect Initialization ....................... 33 6.4. Week Session Key Exchange: Initiator to Responder ......... 33 6.5. Week Session Key Exchange: Responder to Initiator ......... 34 6.6. Retransmission .......................................... 35 7. Packet Protection Agreement ................................... 35 7.1. CRC64 ................................................... 35 7.2. Payload Encryption and Decryption ........................ 36 7.3. Packet Authentication Only ............................... 37 7.4. Installation of Master Key ............................... 38 7.5. Internal Rekeying ........................................ 39 8. Send and Receive ............................................. 39 8.1. Path selection and Multipath Load Balancing .............. 39 8.2. Start a new Transmit Transaction ......................... 40 8.3. Send pure data packet .................................... 40 Gao Expires July 3, 2018 [Page 3] Internet-Draft Flexible Session Protocol January 2018 8.4. Flow Control ............................................ 40 8.5. SNACK and selective retransmission ....................... 41 8.5.1. Calculation of RTT .................................. 41 8.5.2. Generation and transmission of SNACK ................ 41 8.5.3. Negative acknowledgment of Packets Sent ............. 42 8.5.4. Retransmission ...................................... 43 8.6. Commit a Transmit Transaction ............................ 43 8.7. Respond to Transmit Transaction Commitment ............... 43 8.8. Finalize a Transmit Transaction Commitment ............... 43 9. Graceful Close ............................................... 43 9.1. Initiation of Connection Close ........................... 44 9.2. Acknowledgment of Connection Close ....................... 44 9.3. Finalization of Connection Close ......................... 44 9.4. Retry of Connection Close ................................ 44 10. Mobility Support ............................................ 44 10.1. Heartbeat Signals ....................................... 44 10.2. IP Address Change Detection ............................. 45 10.3. IP Address Change Notification .......................... 46 11. Connection Multiplication .................................... 46 11.1. Request to Multiply Connection .......................... 46 11.2. Response to Connection Multiplication Request............ 47 11.3. Duplicate Detection of Connection Multiplication Request . 48 11.4. Retransmission.......................................... 48 11.5. Key Derivation for clone connection ..................... 48 12. Timeouts and abruptly Shutdown ............................... 49 12.1. Timeouts in End-to-End Negotiation ...................... 49 12.2. Timeouts in Multiply .................................... 50 12.3. Timeout of Transmit Transaction Commitment .............. 50 12.4. Timeout of Graceful Shutdown ............................ 50 12.5. Idle Timeout ........................................... 50 12.6. Session Key Timeout ..................................... 50 12.7. Abrupt Shutdown ......................................... 51 13. Interesting Issues .......................................... 51 13.1. Milk-type Payload and Minimal Delay Service ............. 51 13.2. Resolution of ULTID in DNS .............................. 52 13.3. Integrated Proxy Mode of Host Name Resolution............ 53 13.4. Optimizing FSP towards IPv6 ............................. 54 13.5. More reasons to transit towards IPv6 .................... 54 14. Security Considerations ...................................... 55 14.1. Resistance against Deny of Service Attack ............... 55 14.2. Resistance against Replay Attack ........................ 55 14.3. Resistance against Passive Attacks ...................... 56 14.4. Resistance against Masquerade Attack .................... 56 14.5. Resistance against Active Man-In-The-Middle Attack ....... 56 14.6. Privacy concerns ........................................ 56 15. IANA Considerations.......................................... 56 16. Conclusions ................................................. 56 Gao Expires July 3, 2018 [Page 4] Internet-Draft Flexible Session Protocol January 2018 17. References .................................................. 57 17.1. Normative References .................................... 57 17.2. Informative References .................................. 58 18. Acknowledgments ............................................. 64 Authors' Addresses .............................................. 65 1. Introduction Flexible Session Protocol is a connection-oriented transport layer provides mobility, multihoming and multipath support by introducing the concept of 'upper layer thread ID' (ULTID), which was firstly suggested in [Gao2002]. An integrity check code (ICC) field associated with the ULTID is designed in the FSP header to protect authenticity and optionally privacy of the FSP packet. An FSP packet is assumed to originate from the same source if the ICC value associated with certain destination ULTID passes validation, regardless of the source or destination address in the underlying layer. ICC is either calculated by [CRC64] which protects FSP against unintended modification, or cryptographically calculated with some Authenticated Encryption with Additional Data ([R01]) algorithm (for current version of FSP the algorithm chosen is [AES]-[GCM]) or a cryptographic hash function (for current version of FSP it is BLAKE2 [RFC7693]) that requires a shared secret key. In the former case a weak key meant to obfuscate the CRC64 checksum is agreed by the FSP participants. In the latter case, the shared secret key is assumed to be installed by the upper layer application (ULA). The ULTID is assigned roughly the same semantics with Security Parameter Index (SPI) in MOBIKE [RFC4555]. Either the weak key or the shared secret key is indexed by the source or destination ULTID in the local context of the sender or the receiver, respectively. FSP facilitates secret key installation by introducing the concept of transmit transaction. Mechanism to facilitate transmit transaction also provides the session-connection synchronization service to the upper layer. Gao Expires July 3, 2018 [Page 5] Internet-Draft Flexible Session Protocol January 2018 FSP is a transport layer protocol as specified in [RFC1122], provides services alike TCP [STD5] to ULA, with session layer features as suggested in [OSI/RM], most noticeably session-connection synchronization. It can be argued that FSP makes it much more flexible for the application layer protocols to adopt new key establishment protocol/algorithm while offloading routine authentication and optionally encryption of the data to the underlying layers where it may be much easier to exploit hardware- acceleration. 2. Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying significance described in RFC 2119. Integers, no matter 16-bit, 32-bit or 64-bit, signed or unsigned MUST be conveyed in network byte order. Well-known acronyms that may be applied in forming words are: ID Identifier RTT Round-Trip Time SN Sequence Number o EoT A transmit transaction is said to reach End of Transaction (EoT) if the 'End of Transaction' flag is set in a legitimate PURE_DATA, PERSIST or MULTIPLY packet. We said that the packet terminates the transmit transaction if the EoT flag is set. An out-of-band KEEP_ALIVE or ACK_FLUSH packet whose sequence number equals that of the last received packet and whose EoT flag is set forcefully terminates the transmit transaction even if the EoT flag of the last received packet is unset. Gao Expires July 3, 2018 [Page 6] Internet-Draft Flexible Session Protocol January 2018 An ACK_CONNECT_REQ packet itself marks end of the singular transmit transaction. EOT/Termination of transmit transaction is unilateral. An FSP end node may not send further data if it has initiated EOT of its transmit direction unless the ACK_FLUSH packet in response of the EOT initiative is received. o ICC The Identity Check Code is a 64-bit value that depends on both the aforementioned session key and the FSP packet headers, optionally the payload as well, calculated with the same algorithm in the context of each FSP participant. Only a packet with correct ICC can be accepted by any FSP participant unless even the initial session key had not been established. o Session and Connection A full FSP session consists of one connection that was originally established from scratch and all of its clones. However for this version of FSP session and connection are effectively interchangeable. A connection is identified by the ULTID in the local context of the ULA endpoint. o Session Key The session key is a bit string of at least 128 bits that means to resist against masquerade attack, either initially established during the negotiation phase or installed by the ULA after the FSP connection is set up. Initially CRC64 is exploited to make a checksum that weekly protects the FSP packet against unintentional modification. The checksum is obfuscated with the initial session key. The initial session key is neither generated nor applied cryptographically. After the FSP session is set up the ULA SHOULD establish a shared secret key to encrypt payload and/or authenticate the FSP packet. The installed key would be called the long-term session key. Here long- Gao Expires July 3, 2018 [Page 7] Internet-Draft Flexible Session Protocol January 2018 term means that the key could be used until the packet sequence space is exhausted. The packet sequence space is exhausted if the number of packets that use the same key reaches or exceeds 2,147,483,647(2^31- 1). o Transmit Transaction An FSP packet is the data segment of the underlying IPv6 packet, or the payload of one UDP datagram without segmentation in the underlying IPv4 layer, while a transmit transaction of FSP is a sequence of FSP packets that were sent and marked by ULA as one continuous stream where all packets in the stream must be acknowledged before any further packet is allowed to be sent. A PERSIST or MULTIPLY packet always starts a transmit transaction. An ACK_CONNECT_REQ packet itself makes a singular particular transmit transaction. o ULTID The Upper Layer Thread Identifier. It is a 32-bit word that was allocated by particular end point of an FSP connection and is unique in the local context of the end point. 3. Key Mechanisms 3.1. Underlying Layer Services Required 3.1.1. High Mobility High mobility is meant to refer scenarios such as high-speed train or airplane. FSP solves somewhat coarse-grain or low-speed mobility problem. Fine- grain or high-speed mobility is left to the underlying physical network. Here 'physical network' has semantics specified in [RFC1122]. To make mobility support work effectively it is assumed that one end- node MUST keep its lower layer address reasonably stable while the other end-node SHOULD NOT change its lower layer address too frequently so that the packet to inform the remote end to update the lower layer address association could reach its destination in a satisfying success rate. Gao Expires July 3, 2018 [Page 8] Internet-Draft Flexible Session Protocol January 2018 3.1.2. Packet Delivery FSP requires that the underlying layer provides packet delivery service. In this version of FSP, when FSP is implemented in the IPv4 network, every FSP packet MUST be encapsulated in a UDP datagram. When FSP is implemented over IPv6, the IPv6 address is split into three parts. The leftmost 64-bit long word is the network prefix, which SHOULD be the unique IPv6 prefix assigned to the host [RFC8273] the centermost 32-bit word is the aggregation host id, and the rightmost 32-bit word is the ULTID. The network prefix part acts as the routing locator. The network prefix part of the IPv6 address MAY change when an endpoint is roaming, but the ULTID SHALL be kept stable. The endpoint SHOULD immediately notify its peer when its IPv6 address is changed. The peer SHOULD send packet to the endpoint with the new address. 3.2. Upper Layer Thread Identifier and Integrity Check Code To defend against possible connection redirection or dirty data injection (message insertion, deletion, modification and replaying), each FSP connection prepares a pair of ULTIDs. An ULTID is assigned roughly the same semantics with the Security Parameter Index (SPI) in MOBIKE [RFC4555]. An integrity check code (ICC) field is designed in FSP header to protect authenticity and optionally privacy of the FSP packet. On initiating FSP takes use of [CRC64] to make checksum of the FSP packet to protect it against unintentional modification. The checksum is taken as the ICC. After the ULA has installed a secret key, value of ICC is calculated by firstly getting the secret key associated with the local ULTID, then calculating the tag value with the AES-GCM [GCM] authenticated encryption with additional data algorithm [R01], or calculating the message authentication code with the BLAKE2 algorithm [RFC7693]. An ULTID is effective in the local context of an FSP connection only. The source ULTID and the destination ULTID of an FSP packet usually Gao Expires July 3, 2018 [Page 9] Internet-Draft Flexible Session Protocol January 2018 differ in their values. However, the secret keys indexed in the local contexts of the two end-points must have the same value. 3.3. Transmit Transaction Facility FSP facilitates secret key installation by introducing the concept of transmit transaction. A transmit transaction of FSP is a sequence of FSP packets that were sent and marked by ULA as one continuous stream where all packets in the stream MUST be acknowledged before any further packet is allowed to be sent. A flag called 'End of Transaction' (EoT) is designed in the FSP header. When it is set, it marks that the transmit transaction in the direction from the source of the FSP packet towards the destination of the FSP packet is committed. 3.4. Quad-party Session Key Installation Sub-protocol It assumes that in the scenarios applying FSP it is the ULA to do key establishment and/or end-point authentication while the FSP layer provides authenticated, optionally encrypted data transfer service. Together they establish a secure channel between two application end- points. The ULA installs the new secret key to the FSP layer. The FSP layer SHALL make it sure that the new secret key is taken into effect starting from the very first packet of the transmit transaction that is next to the transmit transaction whose context is where the new secret key is installed. Although transmit transaction is actually uni-directional the secret key is shared bidirectionally in this version of FSP. Protocol for installation of the shared secret key is quad-party in the sense that both the upper layer application and the FSP layer of both the participant nodes MUST agree on the moment of certain state to install the shared secret key. A dedicate application program interface (API) is designed for the ULA to install the secret key established by the ULA participants. Gao Expires July 3, 2018 [Page 10] Internet-Draft Flexible Session Protocol January 2018 By committing a transmit transaction a ULA participant clearly tells the underlying FSP layer that the next packet sent MAY adopt a new secret key. On receiving a packet with the EoT flag set the ULA is informed that the next packet received MAY adopt a new shared secret key. The ULA participant that installs the new secret key firstly MUST be the one that is committing a transmit transaction after it has accepted peer's transmit transaction commitment. After the ULA install a new secret key every packet sent later than the one with the EoT flag set MUST adopt the new secret key. The peer MUST have commit a transmit transaction and it SHALL install the same secret key on receiving the FSP packet with the EoT flag set. The ULA SHOULD have installed the new shared secret key, or install it instantly after accepting the packet with the EoT flag set. If the new secret key has ever been installed the packet received after the one with the EoT flag set MUST adopt the new secret key. In a typical scenario the ULA endpoints first setup the FSP connection where resistance against connection redirection is weakly enforced by CRC64. After the pair of ULA endpoints establish a shared secret key, they install the secret key and commit current transmit transactions. Authenticity of the FSP packets sent later is cryptographically protected by the new secret key and resistance against various attacks is secured. It is arguably much more flexible for the application layer protocols to adopt new key establishment algorithm while offloading routine authentication and optionally encryption of the data to the underlying layers where it may be much easier to exploit hardware- acceleration. 3.5. Zero round-trip connection cloning An FSP connection MAY be multiplied to get a clone or clones of the connection. In this version of FSP a clone connection MAY NOT be cloned further, and only the connection where authenticity of the packets is cryptographically protected may be multiplied. Gao Expires July 3, 2018 [Page 11] Internet-Draft Flexible Session Protocol January 2018 The packet that carries the command to multiply an established FSP connection MUST be sent from a new allocated local ULTID towards the destination ULTID of the cloned connection. It is an out-of-band packet in the context of the cloned connection and it MUST be cryptographically protected by the secret key of the cloned connection. The packet MAY carry payload as it usually does. The receiver of the packet MUST allocate a new local ULTID, accept the optional payload in the new context associated with the new ULTID, derive a new secret key from the secret key of the cloned connection, and responds from the new context. The response MAY carry payload as it usually does. The very first response packet MUST be protected by the new secret key. The sender of the multiply command packet MUST automatically inaugurate the same secret key, derived from the secret key of the same cloned connection. And it MUST treat the response packet as though a transmit transaction have been committed by the responder, i.e. authenticity of the response packet is verified with the new secret key. Thus the new clone connection is established at a new pair of ULTIDs with zero round-trip overhead. This mechanism may be exploited to provide expedited data transfer service or parallel data transfer. 4. Packet Structure 4.1. FSP over UDP/IPv4 In this version of FSP, when FSP is implemented in the IPv4 network, every FSP packet MUST be encapsulated in a UDP datagram. The UDP datagram encapsulated the FSP packet SHALL have checksum disabled. The Source and the destination ULTIDs are put at the leading position of the UDP payload. FSP fixed header, optional extension headers and FSP payload follow the ULTIDs. Gao Expires July 3, 2018 [Page 12] Internet-Draft Flexible Session Protocol January 2018 0 15 16 31 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port | Destination Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Upper Layer Thread ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Upper Layer Thread ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ FSP Fix Header ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Optional FSP Extension Headers ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Optional FSP payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1 FSP over UDP 4.2. FSP over IPv6 When FSP is implemented over IPv6, the ULTID part is embedded in the IPv6 address. FSP fixed header follows the IPv6 header(s). ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ IPv6 Header: ~ 0 15 16 31 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Traffic Class | Flow Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Source Network Prefix + | | + Source Address ----------------------------+ | Source Aggregation Host ID | + ----------------------------+ | Source Upper Layer Thread ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Gao Expires July 3, 2018 [Page 13] Internet-Draft Flexible Session Protocol January 2018 + Destination Network Prefix + | | + Destination Address ---------------------------------+ | Destination Aggregation Host ID | + ---------------------------------+ | Destination Upper Layer Thread ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Optional IPv6 Headers ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ FSP Fix Header ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Optional FSP Extension Headers ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Optional FSP payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2 FSP over IPv6 4.3. FSP Header and Header Signature FSP headers include fixed headers and extension headers. A general fixed header consists of 20-byte operation-code specific fields and a 32-bit FSP Header Signature. An extension header consists an operation-code specific content and a 32-bit FSP Header Signature. The length of the extension header content may be variable, provided that the tail of the full extension header align on 64-bit boundary. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Operation Code Specific Fields ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header Signature | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3 FSP Header Gao Expires July 3, 2018 [Page 14] Internet-Draft Flexible Session Protocol January 2018 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header Stack Pointer | Major | Operation Code| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4 FSP Header Signature o Header Stack Pointer A 16-bit unsigned integer that specifies the offset of the octet that immediately follows the next topmost header, while the first topmost header is the one that has the largest offset. o Major An octet states current FSP major version. For this FSP version it MUST be 0. It is not mandatory for different major versions of FSP to be compatible. o Operation Code An octet that stores the code of the command which indicates the function of the packet. 4.4. Operation Code Operation code is the code of the command which indicates the function of an FSP packet. Synonym Code Meaning INIT_CONNECT 1 Initialize Connection ACK_INIT_CONNECT 2 Acknowledge Initialization of Connection CONNECT_REQUEST 3 Formally Request to Connect ACK_CONNECT_REQ 4 Acknowledge the Connection Request. Gao Expires July 3, 2018 [Page 15] Internet-Draft Flexible Session Protocol January 2018 RESET 5 Reset a connection. Refuse to establish the connection, or abort connection. ACK_START 6 ACKnowledgement to start a connection. It is the acknowledgement to ACK_CONNECT_REQ or MULTIPLY, to confirm that the connection has been established or cloned. It MUST be payloadless, and its EoT flag is always assumed to be set. It MAY carry optional headers. It always consumes a slot of the send sequence space. KEEP_ALIVE 7 Keep the peer alive. It is an out-of-band control packet acting as the heart-beating signal. An out-of-band control packet does not consume send sequence space itself. FSP takes use of the KEEP_ALIVE packet to inform the peer about the change of the source IP addresses. Besides, when the MIND flag is set, the KEEP_ALIVE packet is meant to tell the peer which packets should be retransmitted. If the End of Transaction flag of the KEEP_ ALIVE packet is set it is meant to forcefully commit current transmit transaction of the sender of the KEEP_ALIVE packet. PERSIST 8 Make a connection persistent. It is meant to start a new transmit transaction after a connection migrated to CLOSABLE state. It can also acknowledge ACK_CONNECT_REQ or MULTIPLY. It MUST either carry payload, or get the EoT flag set with or without payload. It always consumes a slot of the send sequence space. PURE_DATA 9 Pure Data. Only carry non-empty payload. ACK_FLUSH 10 ACKnowledge to remote end's commitment (FLUSHing) of transmit transaction. It is an out-of-band control packet like KEEP_ALIVE. It is sent instantly on having every packet of the last transmit transaction received, meant to make acknowledgment to the remote end and let the Gao Expires July 3, 2018 [Page 16] Internet-Draft Flexible Session Protocol January 2018 remote end stop sending heart-beat signals. If the End of Transaction flag of the ACK_FLUSH packet is set it is meant to commit current transmit transaction of the sender of the ACK_FLUSH packet as well. RELEASE 11 Release the connection. RELEASE packet MAY NOT carry payload but it always consumes a slot of the send sequence space. Only when each peer has committed the transmit transaction may a RELEASE packet sent under the request of the ULA. MULTIPLY 12 Multiply the connection. It is sent in the context of the cloned connection and may carry payload and/or optional headers as an out-of- band packet. PEER_SUBNETS 17 Tell the remote end how to address the sender of the packet in the reverse direction. It is the code of the Sink Parameter extension header. SELECTIVE_NACK 18 Tell the remote end to retransmit the packets that were negatively acknowledged. It is the code of the Selective Negative Acknowledgment extension header. 4.5. Preliminary FSP Packet Preliminary FSP packets are the packets exchanged during the preliminary phase of FSP connection establishment when it is impossible to calculate ICC normally. 4.5.1. Connect Initialization Operation Code in this type of packet is INIT_CONNECT. Gao Expires July 3, 2018 [Page 17] Internet-Draft Flexible Session Protocol January 2018 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Timestamp + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Init Check Code + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Salt | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header Signature | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Host Name of the Responder (optional) ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5 Connect Initialization o Timestamp The timestamp is a 64-bit unsigned integer that represents number of microseconds elapsed since 00:00, Jan.1, 1970, Coordinated Universal Time. It may be exploited to synchronize the clocks of the participants and/or estimate delay during data transmission in the network. o Init Check Code A 64-bit random bit string that means to uniquely associated with the connection initiated. o Salt A 32-bit random bit string that may be exploited to make secret key agreement. o Host Name of the Responder The optional payload of the Connect Initialization packet. Gao Expires July 3, 2018 [Page 18] Internet-Draft Flexible Session Protocol January 2018 4.5.2. Acknowledgment to Connect Initialization Operation Code of this type of packet is ACK_INIT_CONNECT. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Cookie + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Init Check Code + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time Delta | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header Signature | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6 Acknowledgment to Connect Initialization o Cookie A 64-bit bit string cryptographically generated by the responder in a represent-transfer state manner. More specifically when the same timestamp, time delta, init check code, salt, source and destination ULTIDs are sent to the responder, the responder MUST be able to generate the identical cookie value. o Init Check Code MUST be identical to the corresponding field in the Connect Initialization packet acknowledged. o Time Delta A 32-bit signed integer which is the difference between the near- end's time and the timestamp value sent in the Connection Initialization packet. The units and the epoch of the near-end's time value and the timestamp value MUST be the same. However, the precision or resolution of the time delta value is chosen arbitrarily by the responder, provided that it is not finer than the timestamp. Gao Expires July 3, 2018 [Page 19] Internet-Draft Flexible Session Protocol January 2018 4.5.3. Connect Request Operation Code of this type of packet is CONNECT_REQUEST. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Time Stamp + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Init Check Code + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Salt | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header Signature | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Initial Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time Delta | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Cookie + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Sink Parameter ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Host Name of the Initiator (optional) ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7 Connect Request 'Sink Parameter' is an extension header. Host Name of the Initiator is optional, it could be exploited by the responder to look up the address of the initiator that may receive packets in the reverse direction. Gao Expires July 3, 2018 [Page 20] Internet-Draft Flexible Session Protocol January 2018 Values of other fields of the packet MUST be identical with the ones in the associated Connect Initialization and Acknowledgment to Connect Initialization packet. 4.6. Normal Fixed Header Operation Code of a normal fixed header may be ACK_CONNECT_REQUEST, PURE_DATA, PERSIST, KEEP_ALIVE, ACK_FLUSH, RELEASE or MULTIPLY. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Expected Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Integrity Check Code + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Advertised Receive Window Size | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header Signature | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ o Sequence Number The assigned sequence number of the packet. An out-of-band packet that has the operation code of KEEP_ALIVE, ACK_FLUSH or MULTIPLY MUST be assigned a sequence number that falls in the receive window as well. Each in-band FSP packet is assigned a 32-bit unsigned integer as the sequence number. Difference of two sequence number is represented by a 32-bit signed integer. If the result of sequence number B subtracting sequence number A is greater than zero, we say that B is greater than A and the packet of the sequence number B is later than the packet of the sequence number A, although the unsigned integer representation of B may be far less that A. Consequently, as the result of A subtracting B is less than zero, we say that A is less than B and the packet of the sequence number A is earlier than the packet of the sequence number A. Gao Expires July 3, 2018 [Page 21] Internet-Draft Flexible Session Protocol January 2018 o Expected Sequence Number The field 'Expected Sequence Number' stores the earliest sequence number of the packets that were not yet received in the receive window of the sender. It is an accumulative acknowledgment. Any packet with the sequence number before the received Expected Sequence Number is supposed to have been received by the remote end. o Integrity Check Code The ICC. o Flags It is bit-field of width 8. From left to right: End of Transaction(EoT): if the EoT flag of a packet is set, it is the last, maybe as well the single packet of the transmit transaction. Minimal-Delay (MIND): if the MIND flag of the Connect Request or Acknowledgment to Connect Request packet is set, the ULA prefers minimal delay and is willing to tolerate packet loss. FSP SHALL drop the packet received earliest when there is no enough receive buffer so that the latest packet received can be saved and the delay to deliver data to ULA is minimized. If the MIND flags has been set the EoT flag is simply ignored. Payload of each FSP packet is delivered to the ULA as an independent message. HMAC: if the HMAC flag of a packet is set the cryptographic hash algorithm SHALL be applied to get the message authentication code of the whole packet. Each FSP version MUST designate one particular cryptographic hash algorithm. Explicit Congestion Notification(ECN): Currently yet to be studied. The remaining 4 bits are reserved. o Advertised Receive Window Size Stores number of the free blocks in the receive buffer of the sender of the packet contains the receive window size field. The advertised receive window size is count from the slot meant to accept the packet Gao Expires July 3, 2018 [Page 22] Internet-Draft Flexible Session Protocol January 2018 with the expected sequence number. The sender must ensure that the difference between the latest sequence number sent out and the largest expected sequence number received does not exceed the value of the latest advertised receive window size received. It is a 20-bit unsigned integer. The unit is buffer block. 4.7. Sink Parameter Operation Code in the Header Signature of this extension header is PEER_SUBNETS. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Addressable Network Prefixes ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Listener ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Host ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Block Size | Advertised Receive Window Size | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header Signature | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8 Sink Parameter o Addressable Network Prefixes Up to 4 64-bit words that specify the network prefixes of the lower layer interfaces that are addressable by the receiver in the reverse direction. In this version of the FSP 'Addressable Network Prefixes' field is of fixed length. The last network prefix which is non-zero is the last resort one. There MUST be at least one non-zero network prefix. If there are more than one non-zero network prefixes those other than the last resort are load-balanced preferred. Gao Expires July 3, 2018 [Page 23] Internet-Draft Flexible Session Protocol January 2018 In an IPv6 network, the addressable network prefix is the leftmost 64 bits of the IPv6 address. The receiver of the Addressable Network Prefixes SHALL send packet in the reverse direction, i.e. to the sender of the field with the destination IPv6 address generated by combining a preferred network prefix with the aggregation host id and the ULTID part of the source address in the IPv6 header of the received packet that eventually carries the Addressable Network Prefixes. Such feature MAY be exploited to handle links with unidirectional connectivity, but it is NOT RECOMMENTED. In an IPv4 network for compatibility with the IPv6 addressed ULA the 64-bit word of the addressable network prefix specified is composed as following Figure: 0 31 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x2002 (IPv6 6to4 prefix) |IPv4 address (lestmost 16 bits)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |IPv4 address(rightmost 16 bits)| UDP port number (16 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9 Addressable Network Prefix of FSP over UDP/IPv4 Sender of the Sink Parameter packet SHOULD be NAT-aware. If it is able to obtain the from the NAT box[todo: definition, phrase RFC1631] via protocol UPnP[RFC6970]SHOULD fill in the IPv4 address and UDP port number fields with the public IP value that were obtained. If it does not have such capability, it SHALL fill in the addressable network prefix with all binary zeroes. o Listener ID The ULTID of the responder that is in LISTENING state. o Host ID Gao Expires July 3, 2018 [Page 24] Internet-Draft Flexible Session Protocol January 2018 The aggregation host id of the sender of the Sink Parameter extension header. It MAY differ with the aggregation host id in the source address of the underlying IPv6 address in the IPv6 network. It SHALL be 0 if it is in the IPv4 network. o Block Size A 8-bit unsigned integer that counts number of 512-octet memory sectors that a block of the receive buffer holds. Size of the buffer block is predetermined by scenarios of applying FSP. o Advertised Receive Window Size In the Sink Parameter this field advertise the initial receive window size of the sender of this extension header. 4.8. Selective Negative Acknowledgment The operation code of this type of extension header is SNACK. The SNACK header contains the descriptor of the receive window gaps: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Gap Width | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Further pairs of (Gap Width, Data Length) ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Out-band Serial Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header Signature | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The descriptor itself is a list of entries. The length of the list can be zero which means that there is no gap in the receive window. If the list is not empty, each entry contains the width of one gap in the receive window and the length of the continuously received data Gao Expires July 3, 2018 [Page 25] Internet-Draft Flexible Session Protocol January 2018 following the gap, respectively. The unit of aforementioned length of gaps or number of packets is buffer block. The SNACK header contains a 32-bit out-band serial number as well. Each time a packet that contains the SNACK header is sent the serial number shall increase by one. It is assumed that in the life of the session no two packets have both the same sequence number and the same SNACK header serial number. 4.9. RESET The 'RESET' packet is a special command packet meant to interrupt connection setup process or disconnect abruptly. Operation Code of the packet is RESET. Structure of a RESET packet in C code snippet with unnamed union applied: struct FSP_RejectConnect { union { timestamp_t timeStamp; struct { uint32_t initial; uint32_t expected; } sn; }; // union { uint64_t integrityCode; uint64_t cookie; uint64_t initCheckCode; }; // uint32_t reasons; // bit field $FSP_HeaderSignature hs; }; Gao Expires July 3, 2018 [Page 26] Internet-Draft Flexible Session Protocol January 2018 When the RESET packet is the response to a Connect Initialization packet both the timeStamp and the initCheckCode fields of the RESET packet MUST be set to the same values as in the Connect Initialization packet. When the RESET packet is the response to a Connect Request packet both the timeStamp and the cookie fields of the RESET packet MUST be set to the same value as in the Connect Request packet. When the RESET packet is the response to a packet with a normal fixed header, the sn.initial, the sn.expected and the integrityCode of the RESET packet MUST be set as to specification of normal fixed header field Sequence Number, Expected Sequence Number and Integrity Check Code, respectively. 5. The Finite States 5.1. NON_EXISTENT ---[API: Listen]-->LISTENING |--[API: Connect]-->CONNECT_BOOTSTRAP-->[Send INIT_CONNECT] |--[API: Multiply]-->CLONING-->[Send MULTIPLY] 5.2. LISTENING ---[API: Reset]-->NON_EXISTENT |<-->[Rcv.INIT_CONNECT]{&& resource available}[Send ACK_INIT_CONNECT] |<-->[Rcv.INIT_CONNECT]{&& resource unavailable}[Send RESET] |<-->[Rcv.CONNECT_REQUEST]{&& duplication detected} [Retransmit ACK_CONNECT_REQ] |--[Rcv.CONNECT_REQUEST]-->[API{new context, Callback}] |-->[{return}Accept] -->{new context}CHALLENGING-->[Send ACK_CONNECT_REQ] |-->[{return}Reject]-->[Send RESET] {abort new context} 5.3. CONNECT_BOOTSTRAP ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |--[Rcv.ACK_INIT_CONNECT]-->CONNECT_AFFIRMING |-->[Send CONNECT_REQUEST] |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |<-->{on retransmit timeout}[Retransmit INIT_CONNECT] Gao Expires July 3, 2018 [Page 27] Internet-Draft Flexible Session Protocol January 2018 |--[Transient State timeout]-->NON_EXISTENT-->[Notify] 5.4. CHALLENGING ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |<-->[API: Send{new data}]{just prebuffer} |--[Rcv.ACK_START]-->CLOSABLE-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.PERSIST] |--{Not EOT}-->COMMITTED-->[Send SNACK]{start keep-alive}[Notify] |--{EOT}-->CLOSABLE-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |--[Transient State timeout]-->NON_EXISTENT-->[Notify] In the CHALLENGING state the keep-alive timer is not started yet. 5.5. CONNECT_AFFIRMING ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |<-->[API: Send{new data}]{just prebuffer} |--[Rcv.ACK_CONNECT_REQ]-->PEER_COMMIT-->[API{callback}] |-->{Return Accept} |-->{Not EOT}-->[Send PERSIST] |-->{EOT}-->COMMITTING2-->[Send PERSIST with the EoT flag set] |-->{Return Reject}-->NON_EXISTENT-->[Send RESET] |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |<-->{on retransmit timeout}[Retransmit CONNECT_REQUEST] |--[Transient State timeout]-->NON_EXISTENT-->[Notify] 5.6. ACTIVE{A.K.A. ESTABLISHED} ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |--[API: Send{transact}]-->COMMITTING-->[Urge Commit] |<-->[API: Send{more data}][Send PURE_DATA] |--[Rcv.PURE_DATA] |--{Not EOT}-->{keep state}[Send SNACK]-->[Notify] |--{EOT} |-->{stop keep-alive}PEER_COMMIT-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.PERSIST] |--{Not EOT}-->{keep state}[Send SNACK early] |--[EOT] |-->{stop keep-alive}PEER_COMMIT-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.EOT] Gao Expires July 3, 2018 [Page 28] Internet-Draft Flexible Session Protocol January 2018 |-->{stop keep-alive}PEER_COMMIT-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.MULTIPLY]{passive cloning} |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |--[Idle timeout]-->NON_EXISTENT-->[Notify] 5.7. COMMITTING ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |--[Rcv.ACK_FLUSH]-->COMMITTED-->[Notify] |--[Rcv.PURE_DATA] |--{Not EOT}-->{keep state}[Send SNACK]-->[Notify] |--{EOT}-->COMMITTING2-->[Send ACK_FLUSH]-->[Notify] |--[Rcv. Out-of-band EOT]-->COMMITTING2-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.MULTIPLY]{passive cloning} |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |--[Short-Idled timeout]-->NON_EXISTENT-->[Notify] Note that we may not transmit further data until former transaction acknowledged. 5.8. PEER_COMMIT ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |--[API: Send{flush}]-->COMMITTING2-->[Urge COMMIT]{enable retry} |<-->[API: Send{more data}][Send PURE_DATA] |<-->[Rcv.PURE_DATA]{just prebuffer} |<-->[Rcv.ACK_START]--[Send ACK_FLUSH] |--[Rcv.PERSIST] |-->{Not EOT}-->ACTIVE-->[Send SNACK] |<-->{EOT}--[Send ACK_FLUSH] |--{Not a new transaction}[End.] |--{A new transaction}--[Notify] |--[Rcv.EOT]-->[Send ACK_FLUSH]-->[Notify]{with duplication suppressed} |--[Rcv.MULTIPLY]{passive cloning} |--[Rcv.RELEASE]-->CLOSED-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |--[Idle timeout]-->NON_EXISTENT-->[Notify] 5.9. COMMITTING2 ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |<-->[Rcv.PURE_DATA]{just prebuffer} Gao Expires July 3, 2018 [Page 29] Internet-Draft Flexible Session Protocol January 2018 |--[Rcv.ACK_FLUSH]-->{stop keep-alive}CLOSABLE-->[Notify] |--[Rcv.PERSIST] |-->{Not EOT}-->COMMITTING-->[Send SNACK] |-->{EOT}-->{keep state}-->[Send ACK_FLUSH] |-->{Not a new transaction}[End.] |-->{A new transaction}-->[Notify] |--[Rcv.EOT]-->[Send ACK_FLUSH]-->[Notify]{with duplication suppressed} |--[Rcv.MULTIPLY]{passive cloning} |--[Rcv.RELEASE]-->CLOSED{stop keep-alive}-->[Send RELEASE]-->[Notify] |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |--[Short-Idled timeout]-->NON_EXISTENT-->[Notify] 5.10. COMMITTED ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |--[API: Send{more data}]-->ACTIVE-->[Send PERSIST] |--[API: Send{flush}]-->COMMITTING-->[Urge COMMIT] |--[Rcv.PURE_DATA] |-->{Not EOT}-->{keep state}[Send SNACK]-->[Notify] |-->{EOT} |-->{stop keep-alive}CLOSABLE-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.PERSIST] |-->{Not EOT}-->{keep state}[Send SNACK] |-->{EOT}-->{stop keep-alive}CLOSABLE-->[Send ACK_FLUSH]-->[Notify] |--[Rcv. Out-of-band EOT] |-->{stop keep-alive}CLOSABLE-->[Send ACK_FLUSH]-->[Notify] |--[Rcv.MULTIPLY]{passive cloning} |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |--[Idle timeout]-->NON_EXISTENT 5.11. CLOSABLE ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |--[API: Send{more data}]-->PEER_COMMIT-->[Send PURE_DATA]{enable retry} |--[API: Send{flush}]-->COMMITTING2-->[Urge COMMIT]{enable retry} |--[API: Shutdown]-->[Send RELEASE]-->PRE_CLOSED-->[Notify] |<-->[Rcv.PURE_DATA]{just prebuffer} |<-->[Rcv.ACK_START]--[Send ACK_FLUSH] |<-->[Rcv.Out-of-band EOT]--[Send ACK_FLUSH] |--[Rcv.PERSIST] |-->{Not EOT}-->COMMITTED-->[Send SNACK] Gao Expires July 3, 2018 [Page 30] Internet-Draft Flexible Session Protocol January 2018 |-->{EOT}-->{keep state}[Send ACK_FLUSH] |-->{Not a new transaction}[End.] |-->{A new transaction}-->[Notify] |--[Rcv.MULTIPLY]{passive cloning} |--[Rcv.RELEASE]-->CLOSED-->[Notify] |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] |--[Idle timeout]-->NON_EXISTENT-->[Notify] 5.12. PRE_CLOSED ---[API: Reset]-->NON_EXISTENT-->[Send RESET] |--[Rcv.RELEASE]-->CLOSED{stop Keep-alive}-->[Send RELEASE]-->[Notify] |--[Retransmission timeout][Retransmit RELEASE] |--[Transient timeout]-->NON_EXISTENT 5.13. CLOSED |--[Timeout of Session Key]-->NON_EXISTENT 5.14. CLONING ---[API: Reset]-->NON_EXISTENT |<-->[API: Send{new data}]{just prebuffer} |<-->[Rcv.PURE_DATA]{just prebuffer} |--[Rcv.ACK_START] |-->{Not ULA-flushing}-->PEER_COMMIT |-->{stop keep-alive}[Send ACK_FLUSH]-->[Notify] |-->{ULA-flushing}-->CLOSABLE |-->{stop keep-alive}[Send ACK_FLUSH]-->[Notify] |--[Rcv.PERSIST] |-->{Not EOT} |-->{Not ULA-flushing}-->ACTIVE |-->[Send SNACK]-->[Notify] |-->{ULA-flushing}-->COMMITTED |-->[Send SNACK]-->[Notify] |-->{EOT} |-->{Not ULA-flushing}-->PEER_COMMIT |-->{stop keep-alive}[Send ACK_FLUSH]-->[Notify] |-->{ULA-flushing}-->CLOSABLE |-->{stop keep-alive}[Send ACK_FLUSH]-->[Notify] |--[Rcv.RESET]-->NON_EXISTENT-->[Notify] Gao Expires July 3, 2018 [Page 31] Internet-Draft Flexible Session Protocol January 2018 |<-->{on retransmit timeout}[Retransmit MULTIPLY] |--[Transient State timeout]-->NON_EXISTENT-->[Notify] 5.15. {Cloned} {ACTIVE, COMMITTING, PEER_COMMIT, COMMITTING2, COMMITTED, CLOSABLE, PRE_CLOSED, CLOSED} |<-->[Rcv.MULTIPLY]{&& collision detected}[Send RESET] |<-->[Rcv.MULTIPLY]{&& duplication detected} [Retransmit]{the head packet of the new connection send queue} |--[Rcv.MULTIPLY]{&& new connection request}-->[API{Callback}] |-->[{Return Accept}]-->{new context}ACTIVE/COMMITTING -->[Send PERSIST]{with/without EOT}{start keep-alive} |-->[{Return}:Reject]-->[Send RESET] {abort creating new context} 6. End-to-End Negotiation End-to-end negotiation is the essential part of FSP connection establishment procedure. It consists of two and a half pairs of packet exchanges for connection initialization, session key establishment and the last confirmation. 6.1. Init Check Code, Salt and Cookie The init check code is an arbitrary 64-bit random number generated by the initiator of a connection. The salt is some 32-bit random number generated by the initiator as well. The cookie is a value computed by the responder with a private secret and an algorithm that is assumed known by the responder only. The algorithm chosen MUST make the cookie value depend on the salt and the responder's ULTID, and the value MUST be independent of any participant's IP address. The computation of the cookie MUST be recoverable in the sense that in some limit time period when the responder's ULTID, the salt and the private secret remain unchanged the cookie generated MUST be unchanged as well. Cookie SHOULD NOT be stored by the responder. Gao Expires July 3, 2018 [Page 32] Internet-Draft Flexible Session Protocol January 2018 6.2. Connect Initialization The initiator sends the INIT_CONNECT packet to the responder: (INIT_CONNECT, Timestamp, Init Check Code, Salt [, Responder's Host Name]) 6.3. Response to Connect Initialization The responder sends acknowledgment to the initiator: Case 1: (ACK_INIT_CONNECT, Cookie, Echo of Initiator's Check Code, Time-delta) Case 2: (RESET, Echo of Timestamp, Echo of Initiator's Check Code, Reason of Failure) In case 1 the responder is ready to accept the connection. It MUST not make state transition on receiving INIT_CONNECT packet. It just generates a cookie which is meant to be echoed back by the initiator. The responder MUST send the ACK_INIT_CONNECT packet with the new allocated local ULTID instead of the original listening ULTID. The initiator should be able to find out the original listening ULTID by searching its own connection context. In case 2 the responder refuses to accept the connection. It SHALL send back a RESET packet with the listening ULTID as the source ULTID. 6.4. Week Session Key Exchange: Initiator to Responder (CONNECT_REQUEST, Timestamp, Initiator's Check Code, Salt, Echo of Cookie, Echo of Time-delta, Initial SN, Initiator's Sink Parameter [, Initiator's Host Name]) The initiator checks that the echo of the initiator's check code in the ACK_INIT_CONNECT packet. If the code is correct, the initiator formally requests to establish the connection by sending the CONECT_REQUEST packet. In the packet the value of the Timestamp, the Initiator's Check Code and the Salt field MUST be the same as in the INIT_CONNECT packet while the value of the Echo of Cookie field and Gao Expires July 3, 2018 [Page 33] Internet-Draft Flexible Session Protocol January 2018 the Echo of Time-delta field MUST be the same as in the ACK_INIT_ CONNECT packet, respectively. The initiator MUST send the packet towards the remote ULTID that the responder has preserved and sent with the ACK_INIT_CONNECT packet. It MUST fill the original listener ID field in the Initiator's Sink Parameter with the right value. The initiator SHALL save the cookie value that the responder has given to make up the session key. The initiator MUST fill the Initial SN field with the sequence number of the packet that will follow CONNECT_REQUEST. The CONNECT_REQUEST packet is payload free and does not consume the sequence space. The following packet can only be PERSIST and it may carry payload. The initiator should retransmit the CONNECT_REQUEST packet if it does not receive the ACK_CONNECT_REQ packet in the limit time (by default 5 seconds). If in a longer time (by default 60 seconds) starting from the first INIT_CONNECT packet was transmitted no legitimate ACK_CONNECT_REQ packet was received the initiator should give up setting up the connection. 6.5. Week Session Key Exchange: Responder to Initiator Case 1: (ACK_CONNECT_REQ, Initial SN, Expected SN, Timestamp, Flags and Receive Window Size, Responder's Sink Parameter[, Payload]) Case 2: (RESET, Echo of Timestamp, Echo of Echo of Cookie, Reason of Failure) The responder responds as in case 1 if the echo of cookie was valid, resources were successfully allocated and the initial context of the connection was setup. Otherwise it should respond as in case 2. The Initial SN in case 1 is the initial sequence number of the responder. The responder should fill in the field with a random 32- bit unsigned integer. Gao Expires July 3, 2018 [Page 34] Internet-Draft Flexible Session Protocol January 2018 As the ACK_CONNECT_REQ packet may carry payload the sequence number of the responder starts from the ACK_CONNECT_REQ packet. The Expected SN MUST equal to the Initial SN specified in the corresponding CONNECT_ REQUEST packet. In the Responder's Sink Parameter the original listener ULTID MUST be set to the right value. 6.6. Retransmission The initiator SHALL retransmit the INIT_CONNECT packet if the corresponding ACK_INIT_CONNECT packet is not received in some limit time (by default 15 seconds). The initiator SHALL retransmit the CONNECT_CONNECT packet if the corresponding ACK_CONNECT_REQ packet is not received in some limit time (by default 15 seconds). The responder SHALL NOT retransmit ACK_INIT_CONNECT or ACK_CONNECT_REQ packet. 7. Packet Protection Agreement In a typical scenario the ULA endpoints first setup the FSP connection where resistance against connection redirection attack is weakly endorsed by CRC64. After the pair of ULA endpoints establish a shared secret key, install the secret key and commit current transmit transactions, authenticity of the FSP packets sent later are cryptographically protected. 7.1. CRC64 After the FSP participants have finished End-to-End negotiation, before the ULAs have installed the shared secret CRC64 is applied to calculate the value of the ICC field. The algorithm: 1. Take pair of the ULDs as the initial value of accumulative CRC64. The pair of the ULDs is composed of the near end's ULTID and the remote end's ULTID, where the former is the leftmost 32 bits and the latter is the rightmost 32 bits of initial value for the send direction, and the order is reversed for the receive direction. Gao Expires July 3, 2018 [Page 35] Internet-Draft Flexible Session Protocol January 2018 2. Accumulate the value of the Init Check Code field, the value of the Cookie field successively by CRC64. 3. Accumulate the combined value of the salt and the timeDelta field, where the former is the leftmost 32 bits and the latter is the rightmost 32 bits by CRC64. 4. Accumulate the value of the Time Stamp field by CRC64. 5. Save the accumulated CRC64 value as the precomputed CRC64 value. 6. When calculate the value ICC of a particular FSP packet, firstly set ICC to the precomputed CRC64 value, then calculate the CRC64 checksum of the whole FSP packet, while ULTIDs are NOT included if the FSP packet is encapsulated in UDP. The result is set as the final value of the ICC field. 7.2. Payload Encryption and Decryption FSP provides per-packet authenticated encryption service. Only one authenticated encryption algorithm is allowed for a determined version of FSP. For this FSP version, the authenticated encryption algorithm selected is GCM-AES, it is applied to protect integrity of the full FSP packets and privacy of the payload. The length of the session key is determined by the ULA. The four inputs to GCM-AES authenticated encryption are: K: the key installed by ULA. IV: the initial vector, 96-bit string consisted of the internal 32- bit salt, the 32-bit sequence number of the packet and the 32-bit expected sequence number field of the packet. The internal 32-bit salt MUST be the XOR result of the leftmost 32-bit word of the internal AES hash sub-key and the leftmost 32-bit word of the original key, or a 32-bit word installed by the ULA. P: the plaintext are the bytes following the fixed header up to the end of the original payload AAD: additional authenticated data, from the source ULTID to the last byte of the fixed header. The source ULTID is stored in the leftmost Gao Expires July 3, 2018 [Page 36] Internet-Draft Flexible Session Protocol January 2018 32-bit of the ICC field while the destination ULTID is stored in the rightmost 32-bit of the ICC field before the ICC value is calculated. The length of the authentication tag MUST be 64 bits for FSP version 0 and 1. The authentication tag is stored in the ICC finally. The inputs to GCM-AES decryption are: K: the key installed by ULA. IV: the initial vector, 96-bit string consisted of the internal 32- bit salt, the 32-bit sequence number of the packet and the 32-bit expected sequence number field of the packet. The internal 32-bit salt MUST be the XOR result of the leftmost two 32-bit words of the hash sub-key. C: the ciphertext are the bytes following the fixed header up to the end of the received payload AAD: additional authenticated data, from the source ULTID to the last byte of the fixed header. The source ULTID is stored in the leftmost 32-bit of the ICC field while the destination ULTID is stored in the rightmost 32-bit of the ICC field before the ICC value is calculated T: The authentication tag, which is fetched from the ICC field received Only when the outputs of GCM-AES decryption tell that the authentication tag passed verification may the receiver deliver the decrypted payload to the ULA. 7.3. Packet Authentication Only If the HMAC flag of a packet is set the pre-designated cryptographic hash function SHALL be applied to get the message authentication code (MAC) of the whole packet. Each FSP version MUST designate one and only one particular cryptographic hash function. The ULA designates the FSP layer to either getting MAC or applying AEAD. Gao Expires July 3, 2018 [Page 37] Internet-Draft Flexible Session Protocol January 2018 For this FSP version, BLAKE2 is designated as the cryptographic hash function. The input key is the secret key that has been installed by the ULA. The input data is the full FSP packet, where the ICC field is pre-filled the pair of the ULDs. As in making CRC64 checksum, the pair of the ULDs is composed of the near end's ULTID and the remote end's ULTID, where the former is the leftmost 32 bits and the latter is the rightmost 32 bits of initial value for the send direction, and the order is reversed for the receive direction. The hash result is truncated to 64 bits to get the final ICC. 7.4. Installation of Master Key Given raw key material ikm, length of the ikm nB in octets, intended master key length lenb in bits, || is octet string concatenation: Key Extract phase, as specified in [RFC5869] Let Km = BLAKE2(zeros || ikm) Here zeros is 32 octets of integer 0, and BLAKE2b algorithm without key is applied. The result Km is the master key. Key Expand phase, as specified in [RFC5869] Let Ks = BLAKE2(Km, info) Here info is concatenation of the arbitrary ASCII string "Establishes an FSP session", which is 26-octet long, 3 octets of integer 0, and 1 octet of integer 1. BLAKE2b algorithm with key is applied. The key applied MUST be the master key Km. The result Ks is the initial session key. The output is a fixed-length AES key together with a 4-octet salt. The salt is meant to be passed to AES-GCM as the initialization vector together with the sequence number and expected sequence number fields in the normal FSP fixed header: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Salt | Gao Expires July 3, 2018 [Page 38] Internet-Draft Flexible Session Protocol January 2018 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Expected Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10 Constitution of Initialization Vector 7.5. Internal Rekeying In this version of FSP it is forced to re-key on sending or receiving every 536870912 (2^29) packets. Let Ks' = BLAKE2(Km, H || info') Where H is the 16-octet internal hash sub-key of AES-GCM of previous session key, info' is concatenation of the arbitrary ASCII string "Sustains an FSP connection", which is 26-octet long, 4 octets of the network order integer batch index. The result Ks' is the new session key, tegother with the new salt meant to be form the IV. The batch index of the initial session key is 1, and it increased by 1 every time before it is to re-key. 8. Send and Receive Hereafter 'FREWS' stands for the Flag and advertised REceive Window Size. It is the 32-bit combined word next to the ICC field in the normal FSP fixed header. 8.1. Path selection and Multipath Load Balancing When FSP is implemented over UDP in the IPv4 network, each endpoint of the FSP connection is bound one and only one IPv4 address as soon as the connection is established. Each endpoint SHALL choose the source IPv4 address of the last packet received as the destination IPv4 address of the packet that it is to send later. By this mean FSP over UDP is NAT-friendly. FSP over UDP does not support multipath load balancing, however. When FSP is implemented over IPv6 as soon as the connection is established the IPv6 address may be changed dynamically, and one more Gao Expires July 3, 2018 [Page 39] Internet-Draft Flexible Session Protocol January 2018 alternate IP address may be added or removed dynamically for individual endpoint as well, provided that ULTID part keeps unchanged while the host IDs part of all IPv6 address of the endpoint are of the same value at any given moment. The sender may choose as the source IP address by selecting any network prefix that it has most-recently sent to its peer in the allowed address list field of the sink paramter header, joining with the host ID in the sink parameter header and the stable ULTID of the sender, and choose as the destination IP address by selecting any network prefix in the allowed address list field of the sink parameter header most-recently received from its peer, joining with the peer's host ID and the peer's ULTID. Thus multiple multihomed paths MAY co-exist between the two FSP endpoints. FSP implementation MUST support multipath load balancing when multiple multihomed paths co-exist. 8.2. Start a new Transmit Transaction The responder starts AND terminates a transmit transaction by send the ACK_CONNECT_REQ packet. The initiator starts a new transmit transaction by sending a PERSIST packet: (PERSIST, SN, ExpectedSN, ICC, FREWS, Payload) Or starts AND terminates a transmit transaction by send the ACK_START packet: (ACK_START, SN, ExpectedSN, ICC, FREWS [, Sink Parameter]) 8.3. Send pure data packet (PURE_DATA, SN, ExpectedSN, ICC, FREWS, Payload) 8.4. Flow Control The participants of an FSP connection negotiate the initial receive window size with the FREWS field in the ACK_CONNECT_REQUEST packet and the first PERSIST packet, respectively. The receive window size SHALL NOT be less than 4 and SHALL be less than 2^24. Gao Expires July 3, 2018 [Page 40] Internet-Draft Flexible Session Protocol January 2018 An FSP participant advertises the receive window size in the FREWS field. An FSP participant SHALL NOT send a packet whose sequence number is later than its peer's ExpectedSN plus its peer's advertised receive window size. 8.5. SNACK and selective retransmission 8.5.1. Calculation of RTT Initial RTT for the Connection Initiator: Equals to the mean of the time elapsed till ACK_ INIT_CONNECT was received since INIT_ CONNECT was sent, and the time elapsed till ACK_CONNECT_REQ was received since CONNECT_ REQUEST was sent. Initial RTT for the Connection Responder: Equals to the time elapsed till the first PERSIST packet was received since ACK_CONNECT_REQ was sent. Initial RTT for the Initiator of Connection Multiplication: Equals to the time elapsed till the first PERSIST packet was received since MULTIPLY was sent. Initial RTT for the Responder of Connection Multiplication: Equals to the most recent RTT of the multiplied connection. Each time a SNACK or an accumulated acknowledgment is received mean round trip time of the packets acknowledged is calculated. Suppose the result is RTT_now, then: RTT_new = (RTT_old + RTT_now) / 2 8.5.2. Generation and transmission of SNACK Whenever the receiver receives a packet it SHALL shift the time to send next heartbeat signal earlier to the time of RTT since current time, if the time to send next heartbeat signal used to be later. If the time is already earlier than the time of RTT since current time, it needs not be shifted. Gao Expires July 3, 2018 [Page 41] Internet-Draft Flexible Session Protocol January 2018 On the time to send the heartbeat signal the FSP node generates the SNACK header, then generate and send a new KEEP_ALIVE or ACK_FLUSH packet to carry the SNACK header. It SHALL send an ACK_FLUSH if it is in PEER_COMMIT, COMMITTING2 or CLOSABLE state, otherwise it SHALL send a KEEP_ALIVE packet. 8.5.3. Negative acknowledgment of Packets Sent Both the ACK_FLUSH and the KEEP_ALIVE packet in FSP carry the SNACK extension header, although number of gap descriptors in the SNACK extension header in the ACK_FLUSH packet MUST be 0. We call them SNACK packets. A SNACK packet P1 is said to be later than P0, if and only if SN of P1 is later than SN of P0, or SN of P1 equals SN of P0 while the out- of-band sequence number of P1 is later than the out-of-band sequence number of P0. If the latest SNACK packet is ACK_FLUSH, all the packets with the sequence number later that the expected field of the packet are assumed to be negatively acknowledged. If the latest SNACK packet is KEEP_ALIVE, the packets with SN in the ranges: [expectedSN, expectedSN + 1st Gap Width), [expectedSN + 1st Gap Width + 1st Data Length, expectedSN + 1st Gap Width + 1st DataLength + 2nd Gap Width), ... [expectedSN + 1st Gap Width + 1st Data Length + ... + (n-1)th Gap Width + (n-1)th Data Length, expectedSN + 1st Gap Width + 1st DataLength + ... + n-th Gap Width), Together with the packets with SN later than expectedSN + 1st Gap Width + 1st DataLength + ... + n-th Gap Width are assumed to be negatively acknowledged Gao Expires July 3, 2018 [Page 42] Internet-Draft Flexible Session Protocol January 2018 When we specify the range, the left square bracket meant to be inclusive, while the right parenthesis meant to be exclusive by convention. 8.5.4. Retransmission Any packet sent 4RTT earlier that is negatively acknowledged MUST be retransmitted instantly. 8.6. Commit a Transmit Transaction A participant of an FSP connection MAY notify its peer that a batch of data transmission is finished by setting the EoT flag of the last packet of the transmit transaction be it PERSIST, PURE_DATA or MULTIPLY, or by setting the EoT flag of an out-of-band KEEP_ALIVE or ACK_FLUSH packet whose sequence number is set to the last sequence number of the packets sent. 8.7. Respond to Transmit Transaction Commitment (ACK_FLUSH, SN, ExpectedSN, ICC, FREWS) The receiver of the packet with EoT flag set SHALL modify the operation code of the decrypted packet with the corresponding sequence number to a pseudo operation code _COMMIT AND set the EoT flag of the _COMMIT packet as well, if the ULA has not fetch the packet yet. No matter whether the packet has already been fetched the FSP layer MUST immediately notify the ULA that a transmit transaction has been committed. The receiver SHALL send the ACK_FLUSH packet as soon as all packets of the transmit transaction has been received. 8.8. Finalize a Transmit Transaction Commitment After receiving the ACK_FLUSH packet the sender of the EoT flag migrates to the COMMITTED or CLOSABLE state from the COMMITTING or COMMITTING2 state, respectively. 9. Graceful Close Shutdown is asymmetric in the sense that one side may unilaterally terminate the session without accept all of its peer's packets. Gao Expires July 3, 2018 [Page 43] Internet-Draft Flexible Session Protocol January 2018 9.1. Initiation of Connection Close (RELEASE, SN, ExpectedSN, ICC, FREWS) Connection close initiation packet can be sent in the PEER_COMMIT, COMMITTING2 or CLOSABLE state only. FSP migrates to the PRE_CLOSED state when Shutdown was called in these states. 9.2. Acknowledgment of Connection Close (RELEASE, SN, ExpectedSN, ICC, FREWS) The RELEASE packet may be accepted in the COMMITTING, COMMITTED, CLOSABLE or PRE_CLOSED state only. 9.3. Finalization of Connection Close Connection close initiated in the CLOSABLE state needs not be acknowledged before the FSP node migrates to the CLOSED state. The FSP node in the PRE_CLOSED state migrates to the CLOSED state after the corresponding RELEASE packet is received. 9.4. Retry of Connection Close The RELEASE packet that was sent in the CLOSABLE state is never retransmitted. Loss of the RELEASE packet would simply let the peer in CLOSABLE state timeout. 10. Mobility Support During communication process the participant whose IP address changed should inform its peer by transmit a packet with the Sink Parameter header and the optional SNACK header so that the peer can retransmit the negatively acknowledged packets. FSP requires that the participants periodically send the heartbeat signals. 10.1. Heartbeat Signals The participant in the ACTIVE, COMMITTING or COMMITTED state MUST send the KEEP_ ALIVE packet as the heart-beat signal periodically to Gao Expires July 3, 2018 [Page 44] Internet-Draft Flexible Session Protocol January 2018 retain the connection and make selective negative acknowledgment to its peer's data transmission: (KEEP_ALIVE, SN, ExpectedSN, ICC, FREWS [, Sink Parameter] [, SNACK]) Heartbeat signal is an out-of-band control packet. It may not carry payload and it always borrows the sequence number of the first packet waiting to be send at the first try. Only the FSP node in the ACTIVE, COMMITTING, PEER_COMMIT or COMMITTING2 state may process the heartbeat signal. In the CONNECT_BOOTSTRAP or CONNECT_CONFIRMING state before the connection is established it is only required to retransmit INITIATE_CONNECT or CONNECT_REQUEST packet. None of them is assumed as the heartbeat signal. If the head packet in the send queue is an unacknowledged COMMIT packet it MUST be retransmitted before sending the KEEP_ALIVE packet. In the ACTIVE state if the head packet in the send queue is an unacknowledged PERSIST packet it MUST be retransmitted instead of the KEEP_ALIVE packet when it is time to transmit the heartbeat signal. There is no heartbeat signal in the CLOSABLE or CLOSED state. 10.2. IP Address Change Detection A participant of FSP connection should set the source address of the packet to transmit or retransmit to new IP address as soon as the near-end IPv4 address or IPv6 network prefix has changed. The ULTID field MUST remain the same. When a packet with a later sequence number is received and the source IP address of the packet is found to be different with the preserved remote-end IP address the receiver should automatically update the preserved remote-end IP address to the source IP address of the packet, unless there is a Sink Parameter header in the packet. Any participant of the communication does not make discrimination of the source or destination IP address of any packet provided that both Gao Expires July 3, 2018 [Page 45] Internet-Draft Flexible Session Protocol January 2018 the source ULTID and the destination ULTID keep unchanged and the ICC field passes verification. If the sequence number of the packet received is not the latest in the receive window the preserved remote-end IP address may not be updated even if the source address of the received packet has changed. 10.3. IP Address Change Notification If there is one participant whose receiving interface is not the same as the transmission interface the participant is called asymmetric- transmission node. Asymmetric-transmission itself is asymmetric in the sense that one participant may be asymmetric-transmission node while its peer is normal node of symmetric transmission. The sender is an asymmetric-transmission node if the ACK_CONNECT_REQ packet or PERSIST packet received has a Sink Parameter header and the source IP address of the packet that the network interface of the receiver reports is not in the allowed IP address list in the Sink Parameter header in the packet during connection negotiation. For a remote-end asymmetric-transmission node, the near-end cannot rely on automatic IP address change detection. Instead IP address change notification mechanism should be utilized: (KEEP_ALIVE, SN, ExpectedSN, ICC, FREWS, Sink Parameter [, SNACK]) Both the host ID and the list of the allowed IP addresses MUST be the new refreshed. 11. Connection Multiplication Connection multiplication is the process of incarnating a new connection context. Only connection that provides reliable byte- stream delivery service may be multiplied. In the future version the clone connection MAY provide different class of service with the initiating connection. 11.1. Request to Multiply Connection (MULTIPLY, SN, Salt, ICC, FREWS [, payload]) Gao Expires July 3, 2018 [Page 46] Internet-Draft Flexible Session Protocol January 2018 The initiator's initial sequence number of the new connection is the sequence number of the packet that piggybacks the connection multiplication header. The ExpectedSN field of the normal packet store a Salt value instead. The FREWS field MUST be processed in the new connection context while the ICC MUST be calculated with the session key of the original connection. The new connection inherits the remaining key life. ULA SHOULD negotiate new session key and/or install new session key as soon as possible. The optional payload of the MULTIPLY packet MUST be processed in the new connection context. The MULTIPLY packet is an out-of-band command packet in the original connection context. 11.2. Response to Connection Multiplication Request Case 1: (ACK_START, SN, ExpectedSN, ICC, FREWS [, Sink Parameter]) Case 2: (PERSIST, SN, ExpectedSN, ICC, FREWS, Payload) Case 3: (RESET, SN, ExpectedSN, ICC, FREWS, Reason of Failure) In all of these cases the ULTID of the remote-end MUST be the value of the initiator's ULTID in the connection multiplication header. In case 1 the responder admits the multiplication request AND commit the transmit transaction, the new connection enters into the PEER_COMMIT or CLOSABLE state immediately, on request of ULA. In case 2 the responder admits the multiplication request and the new connection enters into the ESTABLISHED, PEER_COMMIT, or COMMITTING or CLOSABLE state immediately, depending whether the ULA of the multiplication initiator has requested to commit the transmit transaction immediately and whether the ULA of the multiplication responder has requested to commit the transmit transaction in the reverse direction immediately. Gao Expires July 3, 2018 [Page 47] Internet-Draft Flexible Session Protocol January 2018 In case 3 the responder rejects the multiplication request. To defend against spoofing attack ICC MUST be valid. The value of the SN field MUST equal the value of the 'Expected SN' field of the requesting MULTIPLY packet while the value of ExpectedSN field MUST equal the value of the 'Sequence No' field. The new connection MUST derive new session key from the session key of the original connection where the out-of-band requesting MULTIPLY packet is received immediately. 11.3. Duplicate Detection of Connection Multiplication Request Every time the responder of connection multiplication receives a MULTIPLY packet it MUST check the suggested responder's ULTID and the initiator's ULTID. The responder MUST reject the multiplication request if the suggested responder's ULTID equals the near-end ULTID of some connection and the remote-end ULTID of that connection does not equal the initiator's ULTID. The responder MUST recognize the MULTIPLY packet as a duplicate connection request if some connection matches the request and SHOULD response by retransmitting the head packet of the send queue of the matching connection, be it a PERSIST or an COMMIT packet. A connection matches the MULTIPLY request if and only if the suggested responder's ULTID in the MULTIPLY packet equals the near-end ULTID of the connection and the initiator's ULTID equals the remote-end ULTID of the connection. 11.4. Retransmission The initiating side SHALL retransmit the MULTIPLY packet if the corresponding PERSIST packet is not received in some limit time (by default 15 seconds). 11.5. Key Derivation for clone connection Let K_out = BLAKE2(Km, [d] || Label || 0x00 || Context || L) Where Km is the master key, Gao Expires July 3, 2018 [Page 48] Internet-Draft Flexible Session Protocol January 2018 [d] is one octet of integer Depth. It is alike the KDF counter mode as the NIST SP800-108. For this version of FSP it is the fixed number 1. Label - For this version of FSP it is the fixed ASCII string "Multiply an FSP connection" which is 26-octet long. Context - Concatenation of 4 32-bit word seqI, oobsn, idI and idR Length - An 32-bit network byte-order integer specifying the length (in bits) of the derived keying material K-output seqI is the sequence number of the MULTIPLY packet that is sent by the multiplication initiator, in the sequence space of the original connection. oobsn is the out-of-band serial number of the MULTIPLY packet. Both seqI and seqR MUST in network byte order. idI is the sender side ULTID of the original connection that is to initiate the connection multiplication request. idR is the receiver side ULTID of the original connection that is to accept the connection multiplication request. idI or idR is byte-order neutral. 12. Timeouts and abruptly Shutdown 12.1. Timeouts in End-to-End Negotiation Initially the initiator is in the CONNECT_BOOTSTRAP state. It migrates to the CONNECT_ AFFIRMING state after it received the legitimate ACK_INIT_CONNECT packet. Then it migrates to the PEER_COMMIT or CLOSABLE state after it received the legitimate ACK_CONNECT _REQ packet, depending on the hint of ULA. The responder incarnates a new connection context which is initially in the CHALLENGING state after accepting a legitimate Conect Request packet. Then it migrates to the COMMITTING or CLOSABLE state, depending on the packet received from its peer. If the initiator or the responder is unable to migrate to a new state in some limit time (by default 60 seconds, except in LISTENING state) it aborts the connection by recycling the connection context. Gao Expires July 3, 2018 [Page 49] Internet-Draft Flexible Session Protocol January 2018 12.2. Timeouts in Multiply Initially the initiating side of Connection Multiplication is in the CLONING state. It migrates to the ACTIVE, COMMITTED, PEER_COMMIT or CLOSABLE state after it received the legitimate PERSIST packet. Which state to migrated depends on the EoT flag of the initiating MULTIPLY packet and the responding PERSIST packet. If the initiating side is unable to migrate to a new state in some limit time (by default 60 seconds) it aborts multiplication by recycling the new connection context. 12.3. Timeout of Transmit Transaction Commitment The FSP node MUST abort the connection if the time of no packet having arrived has exceed certain limit in the COMMITTING or COMMITTING2 state. In this FSP version, timeout of transmit transaction commitment is set to 5 minutes. 12.4. Timeout of Graceful Shutdown It simply migrates to the NON_EXISTENT pseudo-state if timeout in the PRE_CLOSED state. In this FSP version, timeout of Graceful Shutdown is set to 1 minute. 12.5. Idle Timeout If one participant has not received any packet is a limit time, it MUST abruptly shutdown. In this FSP version idle timeout is set to 4 hours. 12.6. Session Key Timeout For this FSP version if a secret key is applied for more than 2^30 times the FSP node MUST abruptly shutdown instantly. Gao Expires July 3, 2018 [Page 50] Internet-Draft Flexible Session Protocol January 2018 12.7. Abrupt Shutdown An FSP node abruptly shutdown a session by sending a RESET packet and release all of the resource occupied by the the session immediately. (RESET, SN, ExpectedSN, ICC, Reason of Failure) 13. Interesting Issues o Each physically network interface that has IPv6 address configured SHALL NOT have the network prefix configured longer than 96 bits, no matter that the IPv6 address is assigned by Stateless Address Autoconfiguration ([RFC4862]), stateful Dynamic Host Configuration Protocol for IPv6 ([RFC3315], [RFC3633]) or by some other means. o The ULA is the ultimate IPv6 end-point. o Every network node is effectively a router. Especially when FSP over UDP in the IPv4 network is exploited the two end point host nodes are treated as if they were routers connecting the IPv6 addressed ULAs across the IPv4 network. o Whenever an IPv6 interface is reconfigured, the leftmost 64 bits of any IPv6 address MAY change freely, the centermost 32 bits SHOULD be stable while the rightmost 32 bits MUST keep unmodified. 13.1. Milk-type Payload and Minimal Delay Service An ordinary data flow is wine-type in the sense that the older data are of leftmost value. If it has to, data packet sent latest are dropped first. In the contrary, milk-type payload is that the newer data are more precious and outdated data packet can be discarded. When ULA is willing to accept incomplete message the peer of the underling FSP node should set the MIND flag of every FSP PURE_DATA packet, while set the Traffic Class of the underlying IPv6 packet to some registered value. Gao Expires July 3, 2018 [Page 51] Internet-Draft Flexible Session Protocol January 2018 In the transmission path, any relaying middle box, be it router or switch, should reserve a reasonably short queue for the packet flow of such flow to minimize delay. When the receive buffer overflows the receiver discards the undelivered packet received first to free buffer space for the latest packet received. However it keeps order on delivering the packets to he ULA. ULA may choose to discard packets received earlier than some threshold. Optional forward-error-correction feature should be exploited to enhance reliability of data transfer under MIND mode. 13.2. Resolution of ULTID in DNS There are two patterns of IP address resolution in FSP: the DNS- compatible pattern and the proxy pattern. The former pattern relies on some name service to resolve the IP address of the responder for the initiator before they exchange end-to-end packets. The latter embeds the address resolution information in the connection bootstrap packets and works in the FSP over IPv6 only. In the DNS-compatible pattern, the responder side of the FSP participants registered its address identifier, such as 'domain name' in some name service such as DNS, according to some pre-agreement at first. The initiator resolves the current IP address of the responder by consulting the name service, such as looking after the A or AAAA record of the domain name in DNS. In IPv6 network the rightmost 32 bits of the IPv6 address directly maps to the ULTID so FSP does not need additional multiplexing mechanism such as port number. Here it needs not consult SRV record or look for some entry in some 'services' file. If UDP over IPv4 is exploited as the layer data packet delivery service the port number of the responder is firstly resolved just alike normal network application such as HTTP and is extended to 32- bit ULTID. Here ULTIDs of FSP can be considered as the superset of TCP port numbers. Gao Expires July 3, 2018 [Page 52] Internet-Draft Flexible Session Protocol January 2018 If the string representation of IPv4/IPv6 address is applied directly as the peer's address identifier instead of the domain name there is no need for some real address resolution. But from the API caller's point of view it is a DNS-compatible mode address resolution. 13.3. Integrated Proxy Mode of Host Name Resolution In IPv6 network, if the global unicast IP address of the default gateway is configured, the initiator of the FSP connection MAY the IPv6 address of the default gateway as the destination IP address of the INIT_CONNECT packet. If the global unicast IP address of the default gateway is not configured the default link-local gateway address, FE80::1, is applied instead. The gateway that connects the IPv6 host should be able to resolve the IP address of the responder. If there are multiple IP addresses resolvable the gateway may arbitrarily select one. If the gateway found that the responder is on the same link-local network with the initiator it must change the source and the destination IP addresses of the INIT_CONNECT packet to the link-local IP addresses of the initiator and the responder, respectively, and relay the packet onto the same link-local network. If the gateway found that the responder is not on the same link-local network with the initiator it MUST select one public global unicast IP address resolved for the initiator and one public global unicast IP address resolved for the responder, and correspondingly update the 64-bit network prefix part of the source and the destination IP address field of the underlying IPv6 header of the packet, respectively, and relay the packet to the next gateway/router, or the responder itself. If the gateway is unable to resolve the IP address of the responder, it MUST NOT respond to the INIT_CONNECT packet. The initiator decides whether to apply path selection according to the packet acknowledged. If the 64-bit prefix source address of the acknowledgment packet is already in the allowed address list field of the acknowledgment packet path selection is assumed done. Otherwise Gao Expires July 3, 2018 [Page 53] Internet-Draft Flexible Session Protocol January 2018 path selection is applied to determine the source and destination addresses of the CONNECT_REQUEST packet during end-to-end negotiation. 13.4. Optimizing FSP towards IPv6 There are some interesting points to integrated FSP with IPv6 in besides integrated proxy mode of host name resolution. Originally FSP is optimized towards IPv6 and 64-bit computing. In fact, the upper layer application is assumed to be addressed with IPv6-compatible address even in a pure IPv4 network. To utilize IPv6 address space more efficiently FSP makes some slight tuning of address architecture when working over the IPv6 network. In an IPv6 packet that carries FSP payload each of the source and destination 128-bit IPv6 address is split into three parts: the 64- bit network prefix, the 32-bit aggregation host id and the 32-bit ULTID. When FSP is applied in an IPv6 networks, the lower layer addresses SHALL be IPv6. The rightmost 32 bits of each IPv6 address is designated as the ULTID which MUST keep unchanged across IPv6 address migration or translation. The leftmost 96 bits still holds the routing locator semantics. It can be argued that the routing scalability problem in the IPv6 network is effectively eliminated by such tuning of IPv6. One FSP connection MAY associate with up to 4 lower layer addresses. Besides the IP addresses associated with an FSP connection MAY change after the FSP connection is established. 13.5. More reasons to transit towards IPv6 It may be argued that by implements FSP over IPv6 it provides more reasons to transit towards IPv6: o Infrastructure-independent mobility support To support mobility FSP does not assume any infrastructure prerequisite. However, it may take advantages of physical network mobility support or legacy IP mobility support for IPv4/IPv6 ([RFC3344]/[RFC6275]) to enhance reliability of FSP mobility support. Gao Expires July 3, 2018 [Page 54] Internet-Draft Flexible Session Protocol January 2018 o Elimination of routing scalability issue: FSP over IPv6 assumes that the leftmost 64-bit network prefix is effectively the locator that may be thoroughly optimized for routing efficiency. And thus it may be argued that the routing scalability problem does not exist at all for FSP over such tuned IPv6. o Network-level fault tolerance through inherent multihoming and multipath support o Resist against masquerade attacks o Ubiquitous encryption and/or authentication of data o Performance gains: clone connection makes it easy to avoid head- of-line congestion, while mechanism of transmit transaction may save substantial acknowledgment overheads in the application layer. o Traffic class optimization: FSP support milk-type payload. IPv6 packet of a milk-type FSP payload should take a mark at the IPv6 traffic class field to let the underlying network layer to minimize delay. 14. Security Considerations 14.1. Resistance against Deny of Service Attack FSP is designed to resist against DoS attack by exploiting concept of Cookie. However, resistance against distributed DoS attack relies on external mechanism such as DOTS[DOTS architecture] 14.2. Resistance against Replay Attack In-band sequence number and out-of-band sequence number are exploited to resist against replay attack. repeated header discarded...][as sn, fiber id are randomly choosen! Gao Expires July 3, 2018 [Page 55] Internet-Draft Flexible Session Protocol January 2018 14.3. Resistance against Passive Attacks AEAD MAY be exploited by the ULA to protect it against passive attacks such as eavesdropping, gaining advantage by analyzing the data sent over the line iSCSI implementations MUST provide. MAC only service MAY also be utilized. Together with application layer stream-mode encryption it protects the ULA against passive attacks as well. 14.4. Resistance against Masquerade Attack Both AEAD and MAC only service may be exploited to protect the endpoints against masquerade attack. 14.5. Resistance against Active Man-In-The-Middle Attack The ULA SHALL take account to protect itself against MITM attack when making client authentication and key establishment. 14.6. Privacy concerns It is beneficial for privacy protection that the ULTID of each endpoints of an FSP connection is generated randomly. 15. IANA Considerations A UDP port number should be registered for FSP over UDP/IPv4. A next header selector value (protocol number) should be registered for FSP over IPv6. If Minimal-Delay service is implemented, a dedicate traffic class code value should be registered. 16. Conclusions Flexible Session Protocol is a transport layer protocol as suggested in [RFC1122], with session layer semantic as specified in [OSI/RM]. Alike TCP [STD7], FSP primarily provides reliable byte-stream transfer service. Unlike TCP, the byte-stream may be segmented into almost unlimited number of transmit transaction. Gao Expires July 3, 2018 [Page 56] Internet-Draft Flexible Session Protocol January 2018 FSP provides token management service by cooperating with ULA to manage the shared secret key. The clone connection MAY be utilized to provide expedited data transfer service. The concept of transmit transaction has some semantics of uni- direction adjournment of session. Symmetrical commitment of transmit transaction provides session-connection synchronization. 17. References 17.1. Normative References [STD5] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [STD6] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. [RFC5869] Krawczyk, H. and Eronen, P. "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)", RFC 5869, May 2010. [RFC7693] Saarinen, M-J., Ed. and J-P. Aumasson , "The BLAKE2 Cryptographic Hash and Message Authentication Code (MAC)", RFC 7693, November 2015. Gao Expires July 3, 2018 [Page 57] Internet-Draft Flexible Session Protocol January 2018 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, July 2017. [RFC8273] Brzozowski, J. and Van de Velde, G., "Unique IPv6 Prefix per Host", DOI: 10.17487/RFC8273, December 2017 [AES] NIST, "Advanced Encryption Standard (AES)", November 2001. [CRC64] ECMA, "Data Interchange on 12.7 mm 48-Track Magnetic Tape Cartridges - DLT1 Format Standard, Annex B", ECMA-182, December 1992. [GCM] NIST, "Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC", November 2007. [OSI/RM] ISO and IEC, "Information technology-Open Systems Interconnection - Basic Reference Model: The Basic Model", ISO/IEC 7498-1 Second edition, November 1994. [R01] Rogaway, P., "Authenticated encryption with Associated- Data", ACM Conference on Computer and Communication Security (CCS'02), pp. 98-107, ACM Press, 2002. 17.2. Informative References [STD7] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. [Gao2002] Gao, J., "Fuzzy-layering and its suggestion", IETF Mail Archive, September 2002, https://mailarchive.ietf.org/arch/msg/ietf/u-6i-6f-Etuvh80- SUuRbSCDTwg [Fab1999] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573-1583. Gao Expires July 3, 2018 [Page 58] Internet-Draft Flexible Session Protocol January 2018 [tcpcrypt]Bittau, A., Hamburg, M., Handley, M., Mazieres, D., and D. Boneh, "The case for ubiquitous transport-level encryption", USENIX Security , 2010. [RFC1034] Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES", RFC 1034, November 1987. [RFC1035] Mockapetris, P., "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION", RFC 1035, November 1987. [RFC1644] Braden, R., "T/TCP -- TCP Extensions for Transactions Functional Specification", RFC 1644, July 1994. [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, May 2000. [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains via IPv4 Clouds", RFC 3056, February 2001. [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, September 2001. [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, , July 2003. [RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August 2002. [RFC3596] Thomson, S., Huitema, C., Ksinant V. and M. Souissi, "DNS Extensions to Support IP Version 6", RFC 3596, October 2003. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. [RFC3720] J. Satran, K. Meth, C. Sapuntzakis, M. Chadalapaka and E. Zeidner, "Internet Small Computer Systems Interface (iSCSI)", RFC 3720, April 2004. Gao Expires July 3, 2018 [Page 59] Internet-Draft Flexible Session Protocol January 2018 [RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., Ed., and G. Fairhurst, Ed., "The Lightweight User Datagram Protocol (UDP-Lite)", RFC 3828, July 2004. [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963, January 2005. [RFC3986] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005. [RFC4106] J. Viega and D. McGrew, "The Use of Galois/Counter Mode (GCM) in IPsec Encapsulating Security Payload (ESP)", RFC 4106, June 2005. [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, December 2005. [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005. [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through Network Address Translations (NATs)", RFC 4380, February 2006. [RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple Authentication and Security Layer (SASL)", RFC 4422, June 2006. [RFC4555] Eronen, P., Ed., "IKEv2 Mobility and Multihoming Protocol (MOBIKE)", RFC 4555, June 2006. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. Gao Expires July 3, 2018 [Page 60] Internet-Draft Flexible Session Protocol January 2018 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, September 2007. [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", RFC 4960, September 2007. [RFC5056] Williams, N., "On the Use of Channel Bindings to Secure Channels", RFC 5056, November 2007. [RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M. Kozuka, Stream Control Transmission Protocol (SCTP) Dynamic Address Reconfiguration, RFC 5061, September 2007. [RFC5072] Varada, S., Ed., Haskins, D., and E. Allen, "IP Version 6 over PPP", RFC 5072, September 2007. [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated Encryption", RFC 5116, January 2008. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing Model in Ad Hoc Networks", RFC 5889, September 2010. [RFC5942] Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet Model: The Relationship between Links and Subnet Prefixes", RFC 5942, July 2010. [RFC6177] Narten, T., Huston, G., and L. Roberts, "IPv6 Address Assignment to End Sites", BCP 157, RFC 6177, March 2011. [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility Support in IPv6", RFC 6275, July 2011. [RFC6347] Rescorla, E., and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, January 2012. Gao Expires July 3, 2018 [Page 61] Internet-Draft Flexible Session Protocol January 2018 [RFC6434] Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node Requirements", RFC 6434, December 2011. [RFC6740] Atkinson, RJ and SN Bhatti, "Identifier-Locator Network Protocol (ILNP) Architectural Description", RFC 6740, November 2012. [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, "TCP Extensions for Multipath Operation with Multiple Addresses", RFC 6824, January 2013. [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The Locator/ID Separation Protocol (LISP)", RFC 6830, January 2013. [RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis", RFC 7050, November 2013. [RFC7157] Troan, O., Ed., Miles, D., Matsushima, S., Okimoto, T., and D. Wing, "IPv6 Multihoming without Network Address Translation", RFC 7157, March 2014. [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for Constrained-Node Networks", RFC 7228, May 2014. [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P. and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, October 2014. [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext Transfer Protocol Version 2 (HTTP/2)", RFC 7540, May 2015. [RFC7608] Boucadair, M., Petrescu, A., and F. Baker, "IPv6 Prefix Length Recommendation for Forwarding", BCP 198, RFC 7608, July 2015. [RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy Considerations for IPv6 Address Generation Mechanisms", RFC 7721, March 2016. Gao Expires July 3, 2018 [Page 62] Internet-Draft Flexible Session Protocol January 2018 [RFC7849] Binet, D., Boucadair, M., Vizdal, A., Chen, G., Heatley, N., Chandler, R., Michaud, D., Lopez, D., and W. Haeffner, "An IPv6 Profile for 3GPP Mobile Devices", RFC 7849, May 2016. [RFC8084] Fairhurst, G., "Network Transport Circuit Breakers", BCP 208, RFC 8084, March 2017. [RFC8085] Eggert, L., Fairhurst, G. and G. Shepherd, "UDP Usage Guidelines", BCP 145, RFC 8085, March 2017. [RFC8087] Fairhurst, G. and M. Welzl, "The Benefits of Using Explicit Congestion Notification (ECN)", RFC 8087, March 2017. [RFC8170] D. Thaler, Ed., "Planning for Protocol Adoption and Subsequent Transitions", RFC 8170, May 2017. [HRX08] Ha, S., Rhee, I., and L. Xu, "CUBIC: A New TCP-Friendly High-Speed TCP Variant", ACM SIGOPS Operating System Review, 2008. [NGMN2015]"5G White Paper", NGMN Alliance, February 2015. [I-D.ila-mobility] Mueller, J. and Herbert, T., "Mobility Management Using Identifier Locator Addressing", Internet-Draft draft- mueller-ila-mobility-03, February 2017. [I-D.irtf-t2trg-iot-seccons] Garcia-Morchon, O., Kumar, S. and Sethi, M., "State of the Art and Challenges for the Internet of Things", Internet- Draft draft-irtf-t2trg-iot-seccons-03, May 2017. [I-D.ietf-quic-transport] Gao Expires July 3, 2018 [Page 63] Internet-Draft Flexible Session Protocol January 2018 Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed and Secure Transport", Internet-Draft draft-ietf-quic- transport-03, May 2017. 18. Acknowledgments This document was prepared using 2-Word-v2.0.template.dot. Copyright (c) 2018 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). Gao Expires July 3, 2018 [Page 64] Internet-Draft Flexible Session Protocol January 2018 Authors' Addresses Jason Gao Software Architect Email: jagao@outlook.com Gao Expires July 3, 2018 [Page 65]