PPSP Rui S. Cruz INTERNET-DRAFT IST/INESC-ID/INOV Intended Status: Standards Track Rachel Huang Expires: July 28, 2014 Ning Zong Huawei Mario S. Nunes INESC-ID/INOV Joao P. Taveira IST/INOV January 24, 2014 PPSP Tracker Protocol-Extended Protocol draft-huang-ppsp-extended-tracker-protocol-05 Abstract This document specifies an extended Peer-to-Peer Streaming Protocol - Tracker Protocol, which is a new extension protocol complementing the basic core messages and usages specified in the base tracker protocol for the exchange of meta information between trackers and peers, such as initial offer/request of participation in multimedia content streaming, content information, peer lists and reports of activity and status. It extends the base tracker protocol to include new optional messages providing new usages in the communications between peer and tracker. The extension protocol is retro-compatible with the base tracker protocol. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html Huang, et al. Expires July 28, 2014 [Page 1] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright and License Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. 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. Huang, et al. Expires July 28, 2014 [Page 2] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Extended Tracker Protocol Overview . . . . . . . . . . . . . . 5 4.1. Request-Response Extension . . . . . . . . . . . . . . . . 5 4.2. Protocol-level Extension . . . . . . . . . . . . . . . . . 6 4.3. Usage of Extended Request Messages . . . . . . . . . . . . 6 4.4. Extended Tracker Transaction State Machine . . . . . . . . 7 4.4.1. Normal Operation . . . . . . . . . . . . . . . . . . . 8 4.4.2. Error Conditions . . . . . . . . . . . . . . . . . . . 9 5 Extended Tracker Protocol Specification . . . . . . . . . . . . 9 5.1. Request/Response Syntax and Format . . . . . . . . . . . . 9 5.2. Extended Semantics of PPSPTrackerProtocol Elements . . . . 11 5.3. Extended Request/Response Element in Request Messages . . . 15 5.4. Compatibility with the Base Tracker Protocol . . . . . . . 15 5.5. Negotiation of Chunk Addressing Methods . . . . . . . . . . 15 6. Request/Response Processing . . . . . . . . . . . . . . . . . . 15 6.1. Enhanced CONNECT Request . . . . . . . . . . . . . . . . . 16 6.2. Enhanced FIND Request . . . . . . . . . . . . . . . . . . . 18 6.3. Enhanced STAT_REPORT Request . . . . . . . . . . . . . . . 20 6.4. DISCONNECT Request . . . . . . . . . . . . . . . . . . . . 22 7. Error and Recovery Conditions . . . . . . . . . . . . . . . . . 23 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 23 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 23 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 11 References . . . . . . . . . . . . . . . . . . . . . . . . . . 24 11.1 Normative References . . . . . . . . . . . . . . . . . . . 24 11.2 Informative References . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 Huang, et al. Expires July 28, 2014 [Page 3] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 1. Introduction The PPSP Tracker Protocol is one of the Peer-to-Peer Streaming Protocol which specifies standard format/encoding of information and messages between PPSP peers and PPSP trackers. Based on the requirements defined in [RFC6972], the base tracker protocol specified in [I-D.ietf-ppsp-base-tracker-protocol] has provided the basic core messages to be exchanged between trackers and peers in order to carry out some fundamental operations. They are mandatory messages covering most basic and universal use cases and MUST be implemented in all PPSP-based streaming systems. This document specifies extensions to the base core messages of [I-D.ietf-ppsp-base-tracker-protocol] and new optional request messages providing new usages in some dedicated scenarios. The extensions protocol is retro-compatible with the base tracker protocol. Messages using this specification MUST be safely rejected by trackers not supportting the extensions to avoid affecting interoperability. 2. Terminology 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]. This draft uses terms defined in [RFC6972] and [I-D.ietf-ppsp-base- tracker-protocol]. 3. Motivation There are a number of possible usages and issues which may be useful for discussion and which the base tracker protocol may not be able to deal with. 1. In the base tracker protocol, the disconnection between peer and tracker is achieved by a timeout (of periodic STAT_REPORT messages) which means that trackers lack the ability to timely free up resources. In some cases when the number of connected peers is reaching the maximum capacity of a tracker, resources of the tracker cannot be released immediately, even if some peers leave the swarm. Some P2P applications may require to overcome this shortage of the base tracker protocol. 2. A peer may have the requirement to start streaming the content from some specific point of the content timeline. For example, when the end user watched only part of a content and decided to stop and Huang, et al. Expires July 28, 2014 [Page 4] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 leave, or paused for a long time. When the end user decides to resume the session he/she expects to continue watching the content from the point where he/she interrupted. The peer may then request the tracker to select a subset of peers capable to provide that specific content scope. The above use cases require the base tracker protocol to be extended. 4. Extended Tracker Protocol Overview The extended Tracker Protocol consists of three Request-Response Extensions (to the CONNECT, FIND and STAT_REPORT Request messages of the Base Protocol) and one Protocol-level Extension (a new DISCONNECT Request message). 4.1. Request-Response Extension In this section, the CONNECT, FIND and STAT_REPORT messages specified in the base tracker protocol are extended to meet the needs of use cases listed in section 3. CONNECT: This enhanced CONNECT Request message tends to solve the issue 2 raised in section 3. The extension of the CONNECT Request message includes information of specific content scopes, either media content representations or specific chunks/segments of a media representation in a swarm. The format and detailed processing of enhanced CONNECT Request message is presented in Section 5.1. FIND: The enhanced FIND Request message allows a peer to request the tracker for a subset of peers in a swarm but including specific content scopes, either media content representations or specific chunks/segments of a media representation in a swarm, and may also include an updated network address of the peer. On receiving a FIND message, the tracker selects a subset of peers satisfying the requesting scope. To create the peer list, the tracker may also take peer status, capabilities and peers priority into consideration. Peer priority may be determined by network topology preference, operator policy preference, etc. The format and detailed processing of enhanced CONNECT Request message is presented in Section 5.2. STAT_REPORT: The enhanced STAT_REPORT Request message allows the exchanges of content data information, like chunkmaps, between an active peer and a tracker. The information can be used by a tracker as a qualification to select appropriate subsets of peers in the swarm satisfying Huang, et al. Expires July 28, 2014 [Page 5] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 specific scopes (in terms of content). The format and detailed processing of enhanced CONNECT Request message is presented in Section 5.3. 4.2. Protocol-level Extension A new Request message is introduced in this section to extend those specified in the base tracker protocol [I-D.ietf-ppsp-base-tracker- protocol], to meet the need of issue 1 listed in section 3. DISCONNECT: The DISCONNECT Request message is used when the peer intends to no longer participate in all swarms. When receiving the DISCONNECT Request message from a peer, the tracker deletes the corresponding activity records related to the peer (including its status and all content status for the corresponding swarms). In such a case, the DISCONNECT Request message will have the same effect of timer expiring (STAT_REPORT), but providing a graceful disconnect of that peer from the system. 4.3. Usage of Extended Request Messages An example of usage of the extended request messages is the illustrated in Figure 1. In that figure a peers starts by connecting to the system and joining a specific swarm (swarm_a) in SEED mode. While active, the peer periodically updates the tracker using STAT_REPORT messages. Later, the peer CONNECTs to another swarm (swarm_b) but in LEECH mode, i.e., the end-user intends to watch that new content while still sharing the first one. During the streaming the peer requests an updated list of peers in that new swarm to the tracker. When the end user wants to leave the second content, not having even finished watching, the peer sends CONNECT message with a leave action for the corresponding swarm (swarm_b) but remains sharing the first content (swarm_a). Later the peer DISCONNECTs from the system. When in a next time, the end user wants to continue watching the content he/she previously left unfinished, the peer CONNECTs to the corresponding swarm in LEECH mode but sending the specific content information scope. +--------+ +---------+ | Peer | | Tracker | +--------+ +---------+ | | |--CONNECT(swarm_a;SEED)---------->| Huang, et al. Expires July 28, 2014 [Page 6] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 |<--------------------------OK-----| : : |--STAT_REPORT(activity)---------->| |<--------------------------Ok-----| : : |--CONNECT(swarm_b;LEECH)--------->| |<-----------------OK+PeerList-----| : : |--STAT_REPORT(ChunkMap_b)-------->| |<--------------------------Ok-----| : : |--FIND(swarm_b)------------------>| |<-----------------OK+PeerList-----| : : |--CONNECT(leave swarm_b)--------->| |<--------------------------Ok-----| : : |--STAT_REPORT(activity)---------->| |<--------------------------Ok-----| : : |--DISCONNECT(nil)---------------->| |<---------------------Ok(BYE)-----| : : |-CONNECT(swarm_b;LEECH;ChunkMap)->| |<-----------------OK+PeerList-----| : : Figure 1: Example of a session for a extended PPSP-TP. 4.4. Extended Tracker Transaction State Machine The tracker state machine introduced in the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol] is now updated in this specification to reflect the extensions introduced. An updated "per- Peer-ID" transaction state machine (Figure 2) is described, corresponding to the enhanced functionalities and control steps of the extended tracker protocol. This extended "per-Peer-ID" transaction state machine is compatible with the one specified in the base tracker protocol. Huang, et al. Expires July 28, 2014 [Page 7] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 +-----------+ +-------+ rcv CONNECT (Transient) | TERMINATE | | START | --------------- (1) +-----------+ +-------+ strt init timer rcv STAT_REPORT ^ | rcv FIND | | rcv DISCONNECT | | on registration error | v on action error | +------------+ ---------------- (A) +<-----| PEER | (Transient) stop init timer | | REGISTERED | snd error | +------------+ | | | | process swarm actions | | --------------------- (2) on CONNECT Error (B) | | snd OK (PeerList) on timeout (C) | / stop init timer ---------------- | / strt track timer stop track timer | / clean peer info | | del registration | | snd error (B) | | | | rcv CONNECT(@leave) | | rcv FIND rcv DISCONNECT (nil) | | ----------------- (3) --------------- (5) \ | ---- snd OK (PeerList) snd OK response ---- \ | / \ rst tracker timer / \ \ | | | rcv CONNECT | (4) | | | | | ----------- | v | v v | rcv STAT_REPORT snd OK \ +-------------+ / --------------- (3) rst track timer ----| TRACKING |---- snd OK response +--------------+ rst track timer Figure 2: Extended Per-Peer-ID Transaction State Machine The state diagram in Figure 2 illustrates the complete state changes together with the causing events and resulting actions when implementing the extensions to the base tracker protocol. Note that Specific error conditions are not shown in the state diagram. 4.4.1. Normal Operation On normal operation the extended process consists of the following steps: 1) This step is same step 1) in section 2.4.1 of the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol]. Huang, et al. Expires July 28, 2014 [Page 8] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 2) This step is same step 2) in section 2.4.1 of the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol]. 3) This step is same step 3) in section 2.4.1 of the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol], but with extended scope in the FIND Request message and in the STAT_REPORT Request message. 4) This step is same step 4) in section 2.4.1 of the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol] 5) While TRACKING, a DISCONNECT message received from the peer, or a CONNECT message with the action to leave the last swarm, the tracker stops the "track timer", cleans the information associated with the participation of the Peer-ID in the the swarm(s) joined, responds with a successful condition, deletes the registration of the Peer-ID and transitions to TERMINATED state for that Peer-ID. 4.4.2. Error Conditions Peers MUST NOT generate protocol elements that are invalid. However, several situations of a peer may lead to abnormal conditions in the interaction with the tracker. The situations may be related with peer malfunction or communications errors. The tracker reacts to the abnormal situations depending on its current state related to a Peer ID, as follows: A) At PEER REGISTERED state, if the Peer ID is considered invalid (in the case of a DISCONNECT requests received from an unregistered Peer ID), the tracker responds with either error codes 401 Unauthorized or 403 Forbidden, transitions to TERMINATE state for that Peer ID and the state machine is destroyed. B) This step is the same step B) in section 2.4.2 of the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol. C) This step is the same step c) in section 2.4.2 of the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol. NOTE: These situations may correspond to a malfunction at the peer or to malicious conditions. Therefore, as preventive measure, the tracker proceeds to TERMINATE state for the Peer ID by de- registering the peer and cleaning all peer information. 5 Extended Tracker Protocol Specification 5.1. Request/Response Syntax and Format Huang, et al. Expires July 28, 2014 [Page 9] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 The architecture specified in the base tracker protocol [I-D.ietf- ppsp-base-tracker-protocol] does not suffer any modification in the extended protocol. The syntax is identical with some elements extended to contain new optional attributes: The SwarmID element MAY be present in DISCONNECT requests. The element "ContentGroup" is added to the format of Request. It MAY be present in requests referencing content, i.e., CONNECT and FIND, if the request includes a content scope. The extended semantics of the attributes and elements within a PPSPTrackerProtocol root element is described in section 5.2. Huang, et al. Expires July 28, 2014 [Page 10] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 5.2. Extended Semantics of PPSPTrackerProtocol Elements The extension semantics of PPSPTrackerProtocol is a follows. +----------------------+---------+----------------------------------+ | Element Name or | Use | Description | | Attribute Name | | | +----------------------+---------+----------------------------------+ | PPSPTrackerProtocol | 1 | The root element. | | @version | M | Provides the version of PPSP-TP. | | Request | 0...1 | Provides the request method | | | | and MUST be present in Request. | | Response | 0...1 | Provides the response method | | | | and MUST be present in Response. | | TransactionID | M | Root transaction Identification. | | Result | 0...N | Result of @action MUST be present| | | | in Responses. | | @transactionID | CM | Identifier of the @action. | | PeerID | 0...1 | Peer Identification. | | | | MUST be present in Request. | | SwarmID | 0...N | Swarm Identification. | | | | MUST be present in Requests. | | @action | CM | Must be set to JOIN or LEAVE. | | @peerMode | CM | Mode of Peer participation in | | | | the swarm, "LEECH" or "SEED". | | @transactionID | CM | Identifier for the @action. | | PeerNUM | 0...1 | Maximum peers to be received | | | | with capabilities indicated. | | @abilityNAT | CM | Type of NAT traversal peers, as | | | | "No-NAT","STUN","TURN" or "PROXY"| | @concurrentLinks| CM | Concurrent connectivity level of | | | | peers, "HIGH", "LOW" or "NORMAL" | | @onlineTime | CM | Availability or online duration | | | | of peers, "HIGH" or "NORMAL" | | @uploadBWlevel | CM | Upload bandwidth capability of | | | | peers, "HIGH" or "NORMAL" | | ContentGroup | 0...1 | Information on content (Table 4) | | PeerGroup | 0...1 | Information on peers (Table 3) | | StatisticsGroup | 0...1 | Statistic data (Table 5) | +----------------------+---------+----------------------------------+ | Legend: | | Use for attributes: M=Mandatory, OP=Optional, | | CM=Conditionally Mandatory | | Use for elements: minOccurs...maxOccurs (N=unbounded) | | Elements are represented by their name (case-sensitive) | | Attribute names (case-sensitive) are preceded with an @ | +-------------------------------------------------------------------+ Table 1: Semantics of the Extended PPSPTrackerProtocol. Huang, et al. Expires July 28, 2014 [Page 11] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 The semantics of PeerGroup element is almost identical with that of the base tracker protocol. +----------------------+---------+----------------------------------+ | Element Name or | Use | Description | | Attribute Name | | | +----------------------+---------+----------------------------------+ | PeerGroup | 0...1 | Contains description of peers. | | PeerInfo | 1...N | Provides information on a peer. | | @swarmID | 0...1 | Swarm Identification. | | PeerID | 0...1 | Peer Identification. | | | | MAY be present in responses. | | PeerAddress | 0...N | IP Address information. | | @addrType | M | Type of IP address, which can be | | | | "ipv4" or "ipv6" | | @priority | CM | The priority of this interface. | | | | Used for NAT traversal. | | @type | CM | Describes the address for NAT | | | | traversal, which can be "HOST" | | | | "REFLEXIVE" or "PROXY". | | @connection | OP | Access type ("3G", "ADSL", etc.) | | @asn | OP | Autonomous System number. | | @ip | M | IP address value. | | @port | M | IP service port value. | | @peerProtocol | OP | PPSP Peer Protocol supported. | +----------------------+---------+----------------------------------+ | Legend: | | Use for attributes: M=Mandatory, OP=Optional, | | CM=Conditionally Mandatory | | Use for elements: minOccurs...maxOccurs (N=unbounded) | | Elements are represented by their name (case-sensitive) | | Attribute names (case-sensitive) are preceded with an @ | +-------------------------------------------------------------------+ Table 2: Semantics of PeerGroup. Table 3 describes the semantics of StatisticsGroup element, extended with content information attributes. +----------------------+---------+----------------------------------+ | Element Name or | Use | Description | | Attribute Name | | | +----------------------+---------+----------------------------------+ | StatisticsGroup | 0...1 | Provides statistic data on peer | | | | and content. | | Stat | 1...N | Groups statistics property data. | | @property | M | The property to be reported | | | | property values and elements | | | | in Table 5 of [I-D.ietf-ppsp-base| | | | -tracker-protocol] | Huang, et al. Expires July 28, 2014 [Page 12] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 | ContentGroup | 0...1 | Information on content (Table 4) | +----------------------+---------+----------------------------------+ | Legend: | | Use for attributes: M=Mandatory, OP=Optional, | | CM=Conditionally Mandatory | | Use for elements: minOccurs...maxOccurs (N=unbounded) | | Elements are represented by their name (case-sensitive) | | Attribute names (case-sensitive) are preceded with an @ | +-------------------------------------------------------------------+ Table 3: Semantics of StatisticsGroup. Huang, et al. Expires July 28, 2014 [Page 13] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 ContentGroup is a new element. The semantics of this element is described in Table 4. +----------------------+---------+----------------------------------+ | Element Name or | Use | Description | | Attribute Name | | | +----------------------+---------+----------------------------------+ | ContentGroup | 0...1 | Provides information on content. | | CAM | 1 | Describes the chunk addressing | | | | method of this content. The value| | | | is identical with the value of | | | | Table 6 of [I-D.ietf-ppsp-peer | | | | -protocol] | | Representation | 1...N | Describes a component of content.| | @id | M | Unique identifier for this | | | | Representation. | | SegmentInfo | 1 | Provides segment information. | | @startIndex | M | The index of the first media | | | | segment in the request scope for | | | | this Representation. | | @endIndex | OP | The index of the last media | | | | segment in the request scope for | | | | this Representation. | +----------------------+---------+----------------------------------+ | Legend: | | Use for attributes: M=Mandatory, OP=Optional, | | CM=Conditionally Mandatory | | Use for elements: minOccurs...maxOccurs (N=unbounded) | | Elements are represented by their name (case-sensitive) | | Attribute names (case-sensitive) are preceded with an @ | +-------------------------------------------------------------------+ Table 4: Semantics of ContentGroup The Representation element describes a component of a content identified by its attribute @id in the Media Presentation Description (MPD). This element MAY be present for each component desired in the scope of the FIND or CONNECT requests. The scope of each Representation is indicated by the SegmentInfo element and the attributes @startIndex and, optionally, @endIndex. Huang, et al. Expires July 28, 2014 [Page 14] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 5.3. Extended Request/Response Element in Request Messages Table 5 specifies the valid string representations for the requests extended in this specification to complement those define in the base tracker protocol. These values MUST be treated as case-sensitive. +----------------------+ | Extended XML Request | | Methods String Values| +----------------------+ | DISCONNECT | +----------------------+ Table 5: Extended Valid Strings for Request Element of Requests. The response elements in the extension are identical to those of the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol]. 5.4. Compatibility with the Base Tracker Protocol Trackers are RECOMMENDED to implement extended tracker protocol to be compatible with peers using base tracker protocol or peers using extended tracker protocol. But it is not mandatory. When peers using extended tracker protocol changes content information with a tracker only supporting base tracker protocol, the tracker could directly ignore the content related information, e.g. ContentGroup element and Representation attribute. Peers implementing the extended tracker protocol sending DISCONNECT message to legacy trackers will get respond with 400 (Bad request, with reason-phrase "Unknown Messages"), which indicate the messages could not be recognized by the tracker. In this case, the peers MUST stop interacting with the tracker in extended request messages and use the base tracker protocol instead. 5.5. Negotiation of Chunk Addressing Methods Multiple chunk addressing methods could be used in this document to present content information. But only one of them MUST be used for one swarm when a peer communicating with a tracker. Before peers connect to a tracker, it MUST get the knowledge of the chunk addressing methods supported by the tracker. How to get the information is out of scope of the tracker protocol. It could be some out-of-band methods. For example, the chunk addressing methods supported by the tracker could be obtained from the web portal together with other information of the tracker, e.g. IP address. 6. Request/Response Processing Huang, et al. Expires July 28, 2014 [Page 15] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 6.1. Enhanced CONNECT Request This method is used when a peer wants to join one or multiple swarms. The tracker records the Peer-ID, connect-time, IP addresses and link status. The peer MUST properly form the XML message-body, set the Request method to CONNECT, generate and set the TransactionID, and set the PeerID with the identifier of the peer. The peer SHOULD also include the IP addresses of its network interfaces in the CONNECT message. Extended CONNECT request is retro-compatible with the CONNECT request message defined in the base tracker protocol specification. An example of the message-body of the extended CONNECT Request is the following. CONNECT 656164657220 12345.0 1111 5 Huang, et al. Expires July 28, 2014 [Page 16] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 In this example, the peer wants to participate in swarm 1111 to watch the program as LEECH, and it also wishes to start from a specific point of the content timeline. As such, the CONNECT request message contains a ContentGroup element including the information to restrict the search for peers in the swarm. The extended CONNECT request MAY include a PeerNum element to indicate to the tracker the number of peers to be returned in a list corresponding to the indicated properties, being @abilityNAT for NAT traversal (considering that PPSP-ICE NAT traversal techniques may be used), and optionally @concurrentLinks, @onlineTime and @uploadBWlevel for the preferred capabilities. In case PeerMode is LEECH, the tracker will search and select a proper list of peers satisfying the conditions requested. The peer list MUST contain the Peer-IDs and the corresponding IP addresses. To create the peer list, the tracker may take peer status and network location information into consideration, to express network topology preference or operators' policy preferences, with regard to the possibility of connecting with other IETF efforts such as ALTO [I.D.ietf-alto-protocol]. Thus a PeerGroup MAY also be needed in an extended CONNECT request messages. The response MUST have the same TransactionID value as the request. An example of a Response message for the extended CONNECT Request from a leecher is the following: SUCCESSFUL 12345 656164657220 956264622298 3332001256741 Huang, et al. Expires July 28, 2014 [Page 17] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 6.2. Enhanced FIND Request This method allows peers to request to the tracker, whenever needed, a new peer list for the swarm for specific scope of chunks/segments of a media content representation of that swarm. The peer MUST properly form the XML message-body, set the request method to FIND, set the PeerID with the identifier of the peer, set the SwarmID with the identifier of the swarm the peer is interested in. And optionally, in order to find peer having the specific chunks/segments, the peer may include the ContentGroup element in the JOIN request message to indicate a specific point in the content timeline. This message is mainly used for leechers to update the peer list. It is unnecessary to set the PeerMode element in FIND request messages. The peer MUST generate and set the TransactionID for the request. An example of the message-body of a FIND Request is the following: FIND 656164657221 1111 12345 5 The FIND request MAY include a PeerNum element to indicate to the tracker the number of peers to be returned in a list corresponding to the indicated properties, being @abilityNAT for NAT traversal (considering that PPSP-ICE NAT traversal techniques may be used), and optionally @concurrentLinks, @onlineTime and @uploadBWlevel for the preferred capabilities. In the case of a FIND with a specific scope of a stream content the Huang, et al. Expires July 28, 2014 [Page 18] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 request SHOULD include a ContentGroup to specify the segment range of content Representations. When receiving a well-formed FIND Request the tracker processes the information to check if it is valid. In case of success a response message with a Response value of SUCCESSFUL will be generated and the tracker will include the appropriate list of peers satisfying the conditions requested. The peer list returned MUST contain the Peer- IDs and the corresponding IP Addresses. The tracker may take peer status and network location information into consideration when selecting the peer list to return, to express network topology preferences or Operators' policy preferences, with regard to the possibility of connecting with other IETF efforts such as ALTO [I.D.ietf-alto-protocol]. An example of a Response message for the FIND Request is: SUCCESSFUL 12345 956264622298 3332001256741 The Response MUST include a PeerGroup with PeerInfo data that includes the public IP address of the selected active peers in the swarm. The tracker MAY also include the attribute @asn with network location information of the transport addresses of the peers, corresponding to the Autonomous System Numbers of the access network provider of each peer in the list. The response MAY also include a PeerGroup with PeerInfo data that includes the requesting peer public IP address. If STUN-like function is enabled in the tracker, the PeerAddress includes the Huang, et al. Expires July 28, 2014 [Page 19] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 attribute @type with a value of REFLEXIVE, corresponding to the transport address "candidate" of the peer. An example of a Response message for the FIND Request including the requesting peer public IP address is the following: SUCCESSFUL 12345 656164657221 956264622298 3332001256741 6.3. Enhanced STAT_REPORT Request This message still uses the specifications of the base tracker protocol [I-D.ietf-ppsp-base-tracker-protocol]. The Stat element has been extended with one property, "ContentMap", to allow peers reporting map of chunks they have. The tracker would not have the ability to treat the FIND requests for specific content chunks, unless peers report this kind of information. An example of the message-body of an enhanced STAT_REPORT request is the following: STAT_REPORT 656164657221 Huang, et al. Expires July 28, 2014 [Page 20] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 12345 1111 512 768 1024000 2222 1024 2048 512000 1111 A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... 2222 A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... A/8D/wP/A/8D/wP/A/8D/wP/A/8D/wP/.... If the request is valid the tracker process the received information for future use, and generates a response message with a Response Huang, et al. Expires July 28, 2014 [Page 21] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 value of SUCCESSFUL. The response MUST have the same TransactionID value as the request. An example of a Response message for the START_REPORT Request is the following: SUCCESSFUL 12345 6.4. DISCONNECT Request This method is used when the peer intends to leave the system and no longer participate. The tracker SHOULD delete the corresponding activity records related with the peer in the corresponding swarms (including its status and all content status). The peer MUST properly form the XML message-body, set the Request method to DISCONNECT, set the PeerID with the identifier of the peer, randomly generate and set the TransactionID. An example of the message-body of a DISCONNECT Request for the peer leaving all joined swarms is the following: DISCONNECT 656164657221 12345 An example of a Response message for the DISCONNECT Request is the following: SUCCESSFUL 12345 Huang, et al. Expires July 28, 2014 [Page 22] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 7. Error and Recovery Conditions This document does not introduces any new error and recovery conditions. The implementation of error treatment MUST refer to the base tracker protocol specification [I-D.ietf-ppsp-base-tracker- protocol]. 8. Security Considerations The extended tracker protocol proposed in this document introduces no new security considerations beyond those described in the base tracker protocol specification [I-D.ietf-ppsp-base-tracker-protocol]. 9. IANA Considerations There are presently no IANA considerations with this document. 10. Acknowledgments The authors would like to thank many people for their help and comments, particularly: Zhang Yunfei, Martin Stiemerling, Johan Pouwelse and Arno Bakker. The authors would also like to thank the people participating in the EU FP7 project SARACEN (contract no. ICT-248474) [refs.saracenwebpage] for contributions and feedback to this document. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the SARACEN project or the European Commission. Huang, et al. Expires July 28, 2014 [Page 23] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 11 References 11.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, October 2006. [ISO.8601.2004] International Organization for Standardization, "Data elements and interchange formats - Information interchange - Representation of dates and times", ISO Standard 8601, December 2004. 11.2 Informative References [RFC6972] Zhang, Y. and N. Zong, "Problem Statement and Requirements of the Peer-to-Peer Streaming Protocol (PPSP)", RFC 6972, July 2013.. [I-D.ietf-ppsp-base-tracker-protocol] Cruz, R., Nunes, M., Gu, Y., Xia, J., and J. Taveira, "PPSP Tracker Protocol-Base Protocol (PPSP-TP/1.0)", draft-ietf-ppsp-base-tracker- protocol-02 (work in progress), October 2013. [I.D.ietf-alto-protocol] Alimi, R., Penno, R. and Y. Yang, "ALTO Protocol", draft-ietf-alto-protocol-20, (work in progress), October 2013. [ISO.IEC.23009-1] ISO/IEC, "Information technology -- Dynamic adaptive streaming over HTTP (DASH) -- Part 1: Media presentation description and segment formats", ISO/IEC DIS 23009-1, Aug. 2011. [refs.saracenwebpage] "SARACEN Project Website", http://www.saracen-p2p.eu/. Huang, et al. Expires July 28, 2014 [Page 24] INTERNET DRAFT PPSP-TP/1.1 January 24, 2014 Authors' Addresses Rui Santos Cruz IST/INESC-ID/INOV Phone: +351.939060939 Email: rui.cruz@ieee.org Rachel Huang Huawei Phone: +86-25-56623633 EMail: rachel.huang@huawei.com Ning Zong Huawei Phone: +86-25-56624760 EMail: zongning@huawei.com Mario Serafim Nunes INESC-ID/INOV Rua Alves Redol, n.9 1000-029 LISBOA, Portugal Phone: +351.213100256 Email: mario.nunes@inov.pt Joao P. Taveira IST/INOV Email: joao.silva@inov.pt Huang, et al. Expires July 28, 2014 [Page 25]