Network Working Group B. Cheng Internet-Draft D. Wiggins Intended status: Standards Track Lincoln Laboratory Expires: September 2, 2018 L. Berger LabN Consulting, L.L.C. March 1, 2018 DLEP DiffServ Aware Credit Window Extension draft-ietf-manet-dlep-da-credit-extension-04 Abstract This document defines an extension to the DLEP protocol that enables a DiffServ aware credit-window scheme for destination-specific and shared flow control. The extension is logically composed of two mechanisms. The first provides credit window control, the second identifies how flows are identified and mapped to a credit window. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on September 2, 2018. Copyright Notice Copyright (c) 2018 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 (https://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 Cheng, et al. Expires September 2, 2018 [Page 1] Internet-Draft DLEP DA Credit Extension March 2018 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Extension Overview . . . . . . . . . . . . . . . . . . . . . 4 3. Extension Usage and Identification . . . . . . . . . . . . . 5 4. Credit Window Control . . . . . . . . . . . . . . . . . . . . 5 4.1. Data Plane Considerations . . . . . . . . . . . . . . . . 5 4.2. Extension Messages . . . . . . . . . . . . . . . . . . . 6 4.2.1. Credit Control Message . . . . . . . . . . . . . . . 6 4.2.2. Credit Control Response Message . . . . . . . . . . . 7 4.3. Credit Window Control Data Items . . . . . . . . . . . . 7 4.3.1. Credit Window Initialization . . . . . . . . . . . . 8 4.3.2. Credit Window Associate . . . . . . . . . . . . . . . 10 4.3.3. Credit Window Grant . . . . . . . . . . . . . . . . . 11 4.3.4. Credit Window Status . . . . . . . . . . . . . . . . 12 4.3.5. Credit Window Request . . . . . . . . . . . . . . . . 14 5. Traffic Classification . . . . . . . . . . . . . . . . . . . 15 5.1. Traffic Classification Data Item . . . . . . . . . . . . 15 5.1.1. Traffic Classification Sub Data Item . . . . . . . . 17 5.2. DiffServ Credit Window Traffic Classification Sub Data Item . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 19 7. Management Considerations . . . . . . . . . . . . . . . . . . 19 8. Security Considerations . . . . . . . . . . . . . . . . . . . 20 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 9.1. Extension Type Value . . . . . . . . . . . . . . . . . . 20 9.2. Message Values . . . . . . . . . . . . . . . . . . . . . 20 9.3. Data Item Values . . . . . . . . . . . . . . . . . . . . 21 9.4. DLEP Sub Data Item Registry . . . . . . . . . . . . . . . 21 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 10.1. Normative References . . . . . . . . . . . . . . . . . . 22 10.2. Informative References . . . . . . . . . . . . . . . . . 22 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 23 Appendix B. Notional Support for Ethernet Priority Code Points . 23 B.1. Notional Ethernet Credit Window Traffic Classification Sub Data Item . . . . . . . . . . . . . . . . . . . . . . 24 B.2. Other Considerations . . . . . . . . . . . . . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 1. Introduction The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175]. It provides the exchange of link related control information between DLEP peers. DLEP peers are comprised of a modem and a router. DLEP Cheng, et al. Expires September 2, 2018 [Page 2] Internet-Draft DLEP DA Credit Extension March 2018 defines a base set of mechanisms as well as support for possible extensions. This document defines one such extension. The base DLEP specification does not include any flow control capability. There are various flow control techniques theoretically possible with DLEP. For example, a credit-window scheme for destination-specific flow control which provides aggregate flow control for both modem and routers has been proposed in [I-D.ietf-manet-credit-window]. This document defines a DLEP extension which provides a flow control mechanism for traffic sent from a router to a modem. Flow control is provided using one or more logical "Credit Windows", each of which will typically be supported by an associated virtual or physical queue. Traffic sent by a router will use traffic flow classification information provided by the modem to identify which traffic is associated with each credit window. (For general background on traffic classification see [RFC2475] Section 2.3.) Credit windows may be shared or dedicated on a per flow basis. The extension is structured to allow for reuse of the defined credit window based flow control with different traffic classification techniques. This document defines traffic classification based on DLEP destination and DiffServ [RFC2475] DSCPs (differentiated services codepoints). The defined mechanism allows for credit windows to be shared across traffic sent to multiple DLEP destinations and DSCPs, or used exclusively for traffic sent to a particular destination and/ or DSCP. The extension also supports the "wildcard" matching of any DSCP. Traffic classification information is provided such that it can be readily extended to support non-DSCP related traffic classification techniques, or be used by non-credit window related extensions, such as [I-D.ietf-manet-dlep-pause-extension]. The extension defined in this document is referred to as "DiffServ Aware Credit Window" or, more simply, the "DA Credit" extension. Future extensions are expected to define traffic classification techniques other than DiffServ, e.g., IEEE 802.1 Q priority code points or even 5-tuple IP flows. This document defines a new DLEP Extension Type Value in Section 3 which is used to indicate support for the extension. Two new messages are defined in Section 4.2 and five new DLEP data items in Section 4.3 are defined to support credit window control. A single data item is defined in Section 5.1 to support traffic classification in general, as well as identification of flows based on DSCPs. Cheng, et al. Expires September 2, 2018 [Page 3] Internet-Draft DLEP DA Credit Extension March 2018 1.1. Key Words The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Extension Overview The DA Credit extension can be used to support credit based flow control of traffic sent from a router to a modem. The extension can be used to support DiffServ and per DLEP destination based flow control. Both types of DLEP endpoints, i.e., a router and a modem, negotiate the use of extension during session initialization, see Section 5.2 [RFC8175]. When using this extension, data traffic is allowed to be sent by the router to the modem only when there are credits available. Credits are managed on a per logical "Credit Windows" basis. Each credit window can be thought of as corresponding to a queue within a modem. Modems pass to the router information on their credit windows and identify each via a "Credit Window Identifier", or "CID". In addition to the CID, credit window information includes an initial credit window size, as well as the maximum size of the logical queue associated with each CID. The maximum size is included for informative and potential future uses. Modems provide an initial credit window size at the time of "Credit Window Initialization". Such initialization can take place during session initiation or any point thereafter. It can also take place when rate information changes. Additional "Credit Grants", i.e., increments to Credit Window size, are provided using a Destination Up or the new "Credit Control" Message. A router provides its view of the Credit Window, which is known as "Status", in Destination Up Response and the new "Credit Control Response" Messages. Routers can also request credits using the new "Credit Control" Message. When modems provide credits to a router, they will need to take into account any overhead of their attached transmission technology and map it into the credit semantics defined in this document. In particular, the credit window is defined below to include per frame (packet) MAC headers and this may not match the actual overhead of the modem attached transmission technology. In that case a direct mapping or an approximation will need to be made by the modem to provide appropriate credit values. Cheng, et al. Expires September 2, 2018 [Page 4] Internet-Draft DLEP DA Credit Extension March 2018 As mentioned above, traffic classification supported by this document is performed on a per {destination, DSCP} tuple basis. (Per destination traffic classification is also supported.) This means that, routers need the combination of the DLEP identified destination and one or more DSCPs associated with a CID in order to match traffic they send to specific credit windows. Modems provide the mapping of DSCPs to CIDs in sets, each of which is identified via a "Traffic Classification Identifier" or "TID". When a destination becomes reachable, a modem "Associates" (identifies) the TID to be used for traffic sent by the router to that destination. This use of CIDs, TIDs and association of a TID to a DLEP destination enables a modem to share or dedicate resources as needed to match the specifics of its implementation and its attached transmission technology. 3. Extension Usage and Identification The extension defined in this document is composed of the mechanisms and processing defined in Section 4 and Section 5. To indicate that the DiffServ Aware Credit Window Extension is to be used, an implementation MUST include the DiffServ Aware Credit Window Type Value in the Extensions Supported Data Item. The Extensions Supported Data Item is sent and processed according to [RFC8175]. The DiffServ Aware Credit Window Extension Type Value is TBA1, see Section 9. 4. Credit Window Control This section defines additions to DLEP for the control of credit based flow control. As mentioned above, the definition is made in the context of credit windows which can be thought of as representing different logical queues. Two new messages and five data items are defined to support credit window control. Credit window control also impacts the data plane. 4.1. Data Plane Considerations When the use of the extension defined in this document is agreed upon per standard DLEP processing, see Section 3, a router MUST NOT send data traffic to a modem for forwarding when there are no credits available in the associated Credit Window. This document defines credit windows in octets. A credit window value MUST be larger than the number of octets contained in a packet, including any MAC headers used between the router and the modem, in order for the router to send the packet to a modem for forwarding. The credit window is decremented by the number of sent octets. Cheng, et al. Expires September 2, 2018 [Page 5] Internet-Draft DLEP DA Credit Extension March 2018 A router MUST identify the credit window associated with traffic sent to a modem based on the traffic classification information provided in the data items defined in this document. Note that routers will typically view a DLEP destination as the next hop MAC address. 4.2. Extension Messages Two new messages are defined by this extension: the Credit Control and the Credit Control Response Message. Sending and receiving both message types MUST be supported by any implementation that advertises use of this extension per Section 3. 4.2.1. Credit Control Message Credit Control Messages are sent by modems and routers. Each sender is only permitted to have one message outstanding at one time. That is, a sender (modem or router) MUST NOT send a second (or any subsequent) Credit Control Message until a Credit Control Response Message is received from its peer (router or modem). Credit Control Messages are sent by modems to provide credit window increases. Modems send credit increases when there is transmission or local queue availability that exceeds the credit window value previous provided to the router. Modems will need to balance the load generated by sending and processing frequent credit window increases against a router having data traffic available to send, but no credits available. Credit Control Messages MAY be sent by routers to request credits and provide window status. Routers will need to balance the load generated by sending and processing frequent credit window requests against a having data traffic available to send, but no credits available. The Message Type value in the DLEP Message Header is set to TBA2. A message sent by a modem, MUST contain one or more Credit Window Grant Data Items as defined below in Section 4.3.3. A router receiving this message MUST respond with a Credit Control Response Message. A message sent by a router, MUST contain one or more Credit Window Request Data Items defined below in Section 4.3.5 and SHOULD contain a Credit Window Status Data Item, defined in Section 4.3.4, corresponding to each credit window request. A modem receiving this message MUST respond with a Credit Control Response Message based on the received message and data item and the processing defined below, Cheng, et al. Expires September 2, 2018 [Page 6] Internet-Draft DLEP DA Credit Extension March 2018 which will typically result in credit window increments being provided. Specific processing associated with each Credit Data Item is provided below. 4.2.2. Credit Control Response Message Credit Control Response Messages are sent by routers to report the current Credit Window for a destination. A message sent by a router, MUST contain one or more Credit Window Status Data Items as defined below in Section 4.3.4. Specific receive processing associated with the Credit Window Status Data Item is provided below. Credit Control Response Messages sent by modems MUST contain one or more Credit Window Grant Data Items. A data item for every Credit Window Request data item contained in the corresponding Credit Control Response Message received by the modem MUST be included. Each Credit Grant Data Item MAY provide zero or more additional credits based on the modem's transmission or local queue availability. Specific receive processing associated with each Grant Data Item is provided below. The Message Type value in the DLEP Message Header is set to TBA3. 4.3. Credit Window Control Data Items Five new data items are defined to support credit window control. The Credit Window Initialization Data Item is used by a modem to identify a credit window and set its size. The Credit Window Association Data Item is used by a modem to identify which traffic classification identifiers (flows) should be used when sending traffic to a particular DLEP identified destination. The Credit Window Grant is used by a modem to provide additional credits to a router. The Credit Request is used by a router to request additional credits. The Credit Window Status is used to advertise the sender's view of number of available credits for state synchronization purposes. Any errors or inconsistencies encountered in parsing data items are handled in the same fashion as any other data dtem parsing error encountered in DLEP, see [RFC8175]. In particular, the node parsing the data item MUST terminate the session with a Status Data Item indicating Invalid Data. The defined data items and operations have similar objectives as those found in [I-D.ietf-manet-credit-window]. One notable Cheng, et al. Expires September 2, 2018 [Page 7] Internet-Draft DLEP DA Credit Extension March 2018 difference from this extension is that in this document credits are never provided by the router to the modem. 4.3.1. Credit Window Initialization The Credit Window Initialization Data Item is used by a modem to identify a credit window and set its size. This Data Item SHOULD be included in any Session Initialization Response Message that also contains the DiffServ Aware Credit Window Extension Type Value in the Extensions Supported Data Item. Updates to previously identified credit windows or new credit windows MAY be sent by a modem by including the data item in Session Update Messages. More than one data item MAY be included in a message to provide information on multiple credit windows. The Credit Window Initialization Data Item identifies a credit window using a Credit Window Identifier, or CID. It also provides the size of the identified credit window. Finally, a queue size (in bytes) is provided for informational purposes. Note that to be used, a CID must be associated with in a Traffic Classification Identifier via a Credit Window Association Data Item. The format of the Credit Window Initialization Data Item is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length (16) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Window Identifier (CID)| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Value : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Credit Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Scale | Credit Window Size | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: TBA4 Length: 16 Per [RFC8175] Length is the number of octets in the data item. It MUST be equal to sixteen (16). Credit Window Identifier (CID): Cheng, et al. Expires September 2, 2018 [Page 8] Internet-Draft DLEP DA Credit Extension March 2018 A 16-bit unsigned integer identifying a credit window. The value of 0xFFFF is reserved and MUST not be used in this data item. There is no other restriction on values used by a modem, and there is no requirement for sequential or ordered values. Reserved: MUST be set to zero by the sender (a modem) and ignored by the receiver (a router). Credit Value: A 64-bit unsigned integer representing the credits, in octets, to be applied to the Credit Window. This value includes MAC headers as seen on the link between the modem and router. Scale: An 8-bit unsigned integer indicating the scale used in the Credit Window Size fields. The valid values are: Value Scale ------------ 0 B - Bytes (Octets) 1 KB - Kilobytes (B/1024) 2 MB - Megabytes (KB/1024) 3 GB - Gigabytes (MB/1024) Credit Window Size: A 24-bit unsigned integer representing the maximum size, in the octet scale indicated by the Scale field, of the associated credit window. A router that receives a Credit Window Initialization Data Item MUST locate the credit window that is associated with the CID indicated in each received data item. If no associated credit window is found, the router MUST initialize a new credit window using the values carried in the data item. When an associated credit window is found, the router MUST update the credit window using the values carried in the Data Item. It is worth noting, that such updates can result in a credit window size being reduced, for example, due to a transmission rate change on the modem. Cheng, et al. Expires September 2, 2018 [Page 9] Internet-Draft DLEP DA Credit Extension March 2018 4.3.2. Credit Window Associate The Credit Window Associate Data Item is used by a modem to associate traffic classification information with a destination. The traffic classification information is identified using a TID value that has previously been sent by the modem or is listed in a Traffic Classification Data Item carried in the same message as the data item. A single Credit Window Associate Data Item MUST be included in all Destination Up and Destination Update Messages sent by a modem when the use of the extension defined in this document is agreed upon, see Section 3. Note that a TID will not be used unless it is listed in a Credit Window Associate Data Item. The format of the Credit Window Associate Data Item is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length (2) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Traffic Class. Identifier (TID)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: TBA5 Length: 2 Per [RFC8175] Length is the number of octets in the data item. It MUST be equal to two (2). Traffic Classification Identifier (TID): A 16-bit unsigned integer identifying a traffic classification set that has been identified in a Credit Window Traffic Classification Data Item, see Section 5.1. Unknown TID values SHOULD be reported and result in associated traffic being dropped. A router that receives the Credit Window Associate Data Item MUST locate the traffic classification information indicated by the received TID. If no corresponding information can be located, the data item MUST be treated as an error as described above. Once the traffic classification information is located, it MUST be associated with the destination and the router MUST ensure that any data plane state, see Section 4.1, that is associated with the TID is updated as needed. Cheng, et al. Expires September 2, 2018 [Page 10] Internet-Draft DLEP DA Credit Extension March 2018 4.3.3. Credit Window Grant The Credit Window Grant data item is used by a modem to provide credits to a router. One or more Credit Window Grant Data Items MAY be carried in the DLEP Destination Up, Destination Announce Response, Destination Update, Credit Control Messages, and Credit Control Response Messages. Multiple Credit Window Grant Data Items in a single message are used to indicate different credit values for different credit windows. In all message types, this data item provides an additional number of octets to be added to the indicated credit window. Credit window are identified via using CID values that have been previously been sent by the modem or are listed in a Credit Window Initialization Data Item carried in the same messages as the data item. The format of the Credit Window Grant Data Item is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length (12) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Window Identifier (CID)| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Credits : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Additional Credits | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: TBA6 Length: 12 Per [RFC8175], Length is the number of octets in the data item. It MUST be equal to twelve (12). Credit Window Identifier (CID): A 16-bit unsigned integer identifying a credit window that has been identified in a Credit Window Initialization Data Item, see Section 4.3.1. Unknown CID values SHOULD be reported and ignored. Additional Credit: A 64-bit unsigned integer representing the credits, in octets, to be added to the Credit Window. This value includes MAC headers as seen on the link between the modem and router. A value of zero indicates that no additional credits are being provided. Cheng, et al. Expires September 2, 2018 [Page 11] Internet-Draft DLEP DA Credit Extension March 2018 When receiving this data item, a router MUST identify the credit window indicated by the CID. If the CID is not known to the router, it SHOULD report or log this information and discard the Data Item. It is important to note that while this data item can be received in a destination specific message, credit windows are managed independently from the destination identified in the message carrying this Data Item, and the indicated CID MAY even be disjoint from the identified destination. Once the credit window is identified, the credit window size MUST be increased by the value contained in the Additional Credits field. If the increase results in a window overflow, i.e., the size of the credit window after the increase is smaller than the original credit window size, the Credit Window must be set to its maximum (0xFFFFFFFFFFFFFFFF). No response is sent by the router to a modem after processing a Credit Window Grant Data Item received in a Credit Control Response Message. In other cases, the receiving router MUST send a Credit Window Status data item or items reflecting the resulting Credit Window value of the updated credit window. When the Credit Grant data item is received in a Destination Up Message, the Credit Window Status data item(s) MUST be sent in the corresponding Destination Up Response Message. Otherwise, a Credit Control Message MUST be sent. 4.3.4. Credit Window Status The Credit Window Status data item is used by a router to report the current credit window size to its peer modem. One or more Credit Window Status data items MAY be carried in a Destination Up Response Message or a Credit Control Response Message. As discussed above, the Destination Up Response Message is used when the data item is sent in response to a Destination Up Message, and the Credit Control Response Message is sent in response to a Credit Control Message. Multiple Credit Window Status data items in a single message are used to indicate different sizes of different credit windows. Similar to the Credit Window Grant, credit windows are identified using CID values that have been previously been sent by the modem. The format of the Credit Window Status Data Item is: Cheng, et al. Expires September 2, 2018 [Page 12] Internet-Draft DLEP DA Credit Extension March 2018 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length (12) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Window Identifier (CID)| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Window Size : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Credit Window Size | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: TBA7 Length: 12 Per [RFC8175] Length is the number of octets in the data item. It MUST be equal to twelve (12). Credit Window Identifier (CID): A 16-bit unsigned integer identifying a credit window that has been identified in a Credit Window Initialization Data Item, see Section 4.3.1. Credit Window Size: A 64-bit unsigned integer, indicating the current number of credits, in octets, available for the router to send to the modem. This is referred to as the Modem Receive Window in [I-D.ietf-manet-credit-window]. When receiving this data item, a modem MUST identify the credit window indicated by the CID. If the CID is not known to the modem, it SHOULD report or log this information and discard the data item. As with the Credit Window Grant Data Item, the CID MAY be unrelated to the Destination indicated in the message carrying the data item. Once the credit window is identified, the modem SHOULD check the received Credit Window Size field value against the outstanding credit window's available credits at the time the most Credit Window Initialization or Grant data item associated with the indicated CID was sent. If the values significantly differ, i.e., greater than can be accounted for based on observed data frames, then the modem SHOULD send a Credit Window Initialization Data Item to reset the associated credit window size to the modem's current view of the available credits. As defined above, Credit Window Initialization Data Items are sent in Session Update Messages. When multiple data items need Cheng, et al. Expires September 2, 2018 [Page 13] Internet-Draft DLEP DA Credit Extension March 2018 to be sent, they SHOULD be combined into a single message when possible. Alternatively, and also in cases where there are small differences, the modem MAY adjust the values sent in Credit Window Grant data items to account for the reported Credit Window. 4.3.5. Credit Window Request The Credit Window Request Data Item is used by a router to request additional credits for particular credit windows. Credit Window Request Data Items are carried in Credit Control Messages, and one or more Credit Window Request Data Items MAY be present in a message. Credit windows identified using a CID as defined above in Section 4.3.1. Multiple CIDs MAY be present to allow for the case where the router identifies that credits are needed in multiple credit windows. The special CID value of 0xFFFF is used to indicate that a credit request is being made across all queues. The format of the Credit Window Request Data Item is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Window Identifier (CID)| ... : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : ... | Credit Window Identifier (CID)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: TBA8 Length: Variable Per [RFC8175] Length is the number of octets in the data item, excluding the Type and Length fields. It will equal the number of CID fields carried in the data item times 2 and MUST be at least 2. Credit Window Identifier (CID): One or more 16-bit fields used to indicate a credit window that has been identified in a Credit Window Initialization Data Item, see Section 4.3.1. The special value of 0xFFFFFFFF indicates that the request applies to all CIDs. A modem receiving this data item MUST provide a Credit Increment for the indicated credit windows via Credit Window Grant Data Items Cheng, et al. Expires September 2, 2018 [Page 14] Internet-Draft DLEP DA Credit Extension March 2018 carried in a new Credit Control Message. Multiple values and queue indexes SHOULD be combined into a single Credit Control Message when possible. Unknown CID values SHOULD be reported or logged and then ignored by the modem. 5. Traffic Classification Traffic classification is supported by the Traffic Classification Data Item defined below. The base data item and sub data item structure is intended to be independent of any specific usage of the flow identification provided within the data item. It is designed to be extensible for future traffic classification types. While the structure of the data items is extensible, actual flow information is expected to be used in an extension dependent manner. In the context of the DiffServ Aware Credit Window Extension, the Traffic Classification Data Item is used by a modem to identify groups of DSCPs which are to be mapped to a credit window. A DLEP destination address is also needed to complete the traffic classification information. This address is provided by a modem when it identifies the traffic classification set in a Destination Up Message using the Credit Window Associate Data Item defined above. 5.1. Traffic Classification Data Item This sections defines the Traffic Classification Data Item. This data item is used by a modem to provide a router with traffic classification information. When an extension requires use of this data item the Traffic Classification Data Item SHOULD be included by a modem in any Session Initialization Response Message that also contains the corresponding Extension Type Value in the Extensions Supported Data Item. Updates to previously provided traffic classifications or new traffic classifications MAY be sent by a modem by including the data item in Session Update Messages. More than one data item MAY be included in a message to provide information on multiple traffic classifiers. The set of traffic classification information provided in the data item is identified using a Traffic Classification Identifier, or TID. Addition information, e.g., the list DSCPs associated with a credit window, is provided in a variable series of Queue Parameter sub-data items. The format of the Traffic Classification Data Item is: Cheng, et al. Expires September 2, 2018 [Page 15] Internet-Draft DLEP DA Credit Extension March 2018 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Traffic Class. Identifier (TID)| Num SDIs | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Traffic Classification Sub Data Item 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : ... : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Traffic Classification Sub Data Item n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Data Item Type: TBA9 Length: Variable Per [RFC8175] Length is the number of octets in the data item, excluding the Type and Length fields. Traffic Classification Identifier (TID): A 16-bit unsigned integer identifying a traffic classification set. There is no restriction on values used by a modem, and there is no requirement for sequential or ordered values. Num SDIs: An 8-bit unsigned integer indicating the number of Traffic Classification Sub Data Items included in the data item. A value of zero (0) is allowed and indicates that no traffic should be matched against this TID. Reserved: MUST be set to zero by the sender (a modem) and ignored by the receiver (a router). Traffic Classification Sub Data Item: Zero or more Traffic Classification Sub Data Items of the format defined below MAY be included. The number MUST match the value carried in the Num SDIs field. A router receiving the Traffic Classification Data Item MUST locate the traffic classification information that is associated with the TID indicated in each received data item. If no associated traffic Cheng, et al. Expires September 2, 2018 [Page 16] Internet-Draft DLEP DA Credit Extension March 2018 classification information is found, the router MUST initialize a new information set using the values carried in the data item. When associated traffic classification information is found, the router MUST update the information using the values carried in the Data Item. In both cases, a router MUST also ensure that any data plane state, see Section 4.1, that is associated with the TID is updated as needed. 5.1.1. Traffic Classification Sub Data Item All Traffic Classification Sub Data Items share a common format that is patterned after the standard DLEP data item format, see [RFC8175] Section 11.3. There is no requirement on, or meaning to sub data item ordering. Any errors or inconsistencies encountered in parsing sub data items are handled in the same fashion as any other data item parsing error encountered in DLEP. The format of the Traffic Classification Sub Data Item is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub Data Item Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value... : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Sub Data Item Type: A 16-bit unsigned integer that indicates the type and corresponding format of the data item's Value field. Sub Data Item Types are managed according to the IANA registry described in Section 9.4. Length: Variable Copying [RFC8175], Length a 16-bit unsigned integer that is the number of octets in the sub data item, excluding the Type and Length fields. 5.2. DiffServ Credit Window Traffic Classification Sub Data Item The DiffServ Credit Window Traffic Classification Sub Data Item is used to identify the DSCPs associated with a specific credit window. Credit windows are identified using CID values that have been previously been sent by the modem or are listed in a Credit Window Initialization Data Item carried in the same messages as the sub data item. DSCPs are identified in a list of DiffServ fields. An Cheng, et al. Expires September 2, 2018 [Page 17] Internet-Draft DLEP DA Credit Extension March 2018 implementation that does not support DSCPs, and wants to use credit window flow control for all traffic to a destination or destinations, would indicate with 0 DSCPs. The format of the DiffServ Credit Window Traffic Classification Sub Data Item is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Must be two (2) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Window Identifier (CID)| Num DSCPs | DS Field 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DS Field 2 | ... | DS Field n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Length: Variable Length is the number of octets in the sub data item. It is equal to three (3) plus the value of the Num DSCPs field. Credit Window Identifier (CID): A 16-bit unsigned integer identifying a credit window that has been identified in a Credit Window Initialization Data Item, see Section 4.3.1. Unknown CID values SHOULD be reported and result in associated traffic being dropped. Num DSCPs: An 8-bit unsigned integer indicating the number of DSCPs carried in the sub data item. A zero (0) indicates a (wildcard) match against any DSCP value. DS Field: Each DS Field is an 8-bit whose definition is the same as [RFC2474]. 0 1 2 3 4 5 6 7 +---+---+---+---+---+---+---+---+ | DSCP | CU | +---+---+---+---+---+---+---+---+ DSCP: differentiated services codepoint CU: currently unused, MUST be zero Cheng, et al. Expires September 2, 2018 [Page 18] Internet-Draft DLEP DA Credit Extension March 2018 A router receiving the DiffServ Traffic Classification Sub Data Item MUST validate the information on receipt prior to the information and data plane update described earlier in this section. The credit window associated with the CID indicated in each data item must be located. It is important to note that the CID value may be present in a Credit Window Initialization Data Item carried in the same message as the sub data item. If the CID is not located, then it MUST be treated as an error as described above. When there are no unknown CIDs, the receiver MUST ensure that each DS Field value is listed only once across the whole Traffic Classification Data Item. Note, this check is across the data item and not the individual sub data item. If the same DS Field value is listed more than once within the same Traffic Classification Data Item, the data item MUST be treated as an error as described above. In all cases, the router MUST use validated DSCPs in data plane credit window identification as described in Section 4.1. 6. Compatibility Sessions established with both peers identified as supporting the DiffServ Aware Credit Window Extension Type, see Section 3, MUST NOT use the [I-D.ietf-manet-credit-window] defined Credit data items. If a node supporting the extension defined in this document, receives a [I-D.ietf-manet-credit-window] defined data item, the recipient MUST ignore the received information. 7. Management Considerations This section provides several network management guidelines to implementations supporting the DiffServ Aware Credit Window Extension. The use of the extension defined in this document SHOULD be configurable on both modems and routers. Modems SHOULD support the configuration of DSCP to credit window (queue) mapping. Modems MAY support the configuration of the number of credit windows (queues) to advertise to a router. Routers may have limits on the number of queues that they can support and, perhaps, even limits in supported credit window combinations, e.g., if per destination queues can even be supported at all. When modem-provided credit window information exceeds the capabilities of a router, the router MAY use a subset of the provided credit windows. Cheng, et al. Expires September 2, 2018 [Page 19] Internet-Draft DLEP DA Credit Extension March 2018 Alternatively, a router MAY reset the session and indicate that the extension is not supported. In either case, the mismatch of capabilities SHOULD be reported to the user via normal network management mechanisms, e.g., user interface or error logging. 8. Security Considerations The extension introduces a DiffServ awareness to the mechanisms defined in [I-D.ietf-manet-credit-window]. The extension does not inherently introduce any additional threats above those documented in [RFC8175]. The approach taken to Security in that document and [I-D.ietf-manet-credit-window] apply equally when running the extension defined in this document. 9. IANA Considerations This document requests the assignment of 5 values by IANA. All assignments are to registries defined by [RFC8175]. 9.1. Extension Type Value This document requests 1 new assignment to the DLEP Extensions Registry named "Extension Type Values" in the range with the "Specification Required" policy. The requested value is as follows: +------+------------------------------+ | Code | Description | +------+------------------------------+ | TBA1 | DiffServ Aware Credit Window | +------+------------------------------+ Table 1: Requested Extension Type Value 9.2. Message Values This document requests 2 new assignments to the DLEP Message Registry named "Message Values" in the range with the "Specification Required" policy. The requested values are as follows: +-----------+-------------------------+ | Type Code | Description | +-----------+-------------------------+ | TBA2 | Credit Control | | | | | TBA3 | Credit Control Response | +-----------+-------------------------+ Table 2: Requested Message Values Cheng, et al. Expires September 2, 2018 [Page 20] Internet-Draft DLEP DA Credit Extension March 2018 9.3. Data Item Values This document requests the following new assignments to the DLEP Data Item Registry named "Data Item Type Values" in the range with the "Specification Required" policy. The requested values are as follows: +-----------+------------------------------+ | Type Code | Description | +-----------+------------------------------+ | TBA4 | Credit Window Initialization | | | | | TBA5 | Credit Window Association | | | | | TBA6 | Credit Window Grant | | | | | TBA7 | Credit Window Status | | | | | TBA8 | Credit Window Request | | | | | TBA9 | Traffic Classification | +-----------+------------------------------+ Table 3: Requested Data Item Values 9.4. DLEP Sub Data Item Registry Upon approval of this document, IANA is requested to create a new DLEP registry, named "Sub Data Item Type Values". The registry shall identify the type code value, the Data Item which may use the value, and a description of the value. While the same value may be reused in different data items, this is not recommended at this time. The following table provides initial registry values and the [RFC8126] defined policies that should apply to the registry: Cheng, et al. Expires September 2, 2018 [Page 21] Internet-Draft DLEP DA Credit Extension March 2018 +-------------+------------------------------+----------------------+ | Type Code | Valid Data Items | Description | +-------------+------------------------------+----------------------+ | 0 | N/A | Reserved | | | | | | 1 | N/A | Reserved (for pause | | | | sub-DI) | | | | | | 2 | DiffServ Credit Window | DiffServ Traffic | | | Traffic Classification | Classification | | | | | | 2-65407 | | Specification | | | | Required | | | | | | 65408-65534 | | Private Use | | | | | | 65535 | | Reserved | +-------------+------------------------------+----------------------+ Table 4: Initial Registry Values 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, DOI 10.17487/RFC8175, June 2017, . 10.2. Informative References [I-D.ietf-manet-credit-window] Ratliff, S., "Credit Windowing extension for DLEP", draft- ietf-manet-credit-window-07 (work in progress), November 2016. Cheng, et al. Expires September 2, 2018 [Page 22] Internet-Draft DLEP DA Credit Extension March 2018 [I-D.ietf-manet-dlep-pause-extension] Cheng, B., Wiggins, D., and L. Berger, "DLEP Control Plane Based Pause Extension", draft-ietf-manet-dlep-pause- extension-02 (work in progress), October 2017. [IEEE.802.1Q_2014] IEEE, "IEEE Standard for Local and metropolitan area networks--Bridges and Bridged Networks", IEEE 802.1Q-2014, DOI 10.1109/ieeestd.2014.6991462, December 2014, . [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474, December 1998, . [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . Appendix A. Acknowledgments The sub data item format was inspired by Rick Taylor's "Data Item Containers". He also proposed the separation of credit windows from traffic classification at IETF98. Many useful comments were received from contributors to the MANET working group. Appendix B. Notional Support for Ethernet Priority Code Points This document is intended to allow for use of the credit control mechanisms defined in Section 4 with different flow identification techniques. This section explores the viability of this through the notional definition of credit control with Ethernet Priority Code Points. Ethernet Priority Code Point support is defined as part of the IEEE 802.1Q [IEEE.802.1Q_2014] tag format and includes a 3 bit "PCP" field. The tag format also includes a 12 bit VLAN identifier (VID) field. In theory only one new Traffic Classification Sub Data Item is required to enable support for the traffic classification of a new Cheng, et al. Expires September 2, 2018 [Page 23] Internet-Draft DLEP DA Credit Extension March 2018 flow type. This section defines such a sub data item. This definition is not a full Extension definition, but may serve as the foundation for such in the future; in a new document. B.1. Notional Ethernet Credit Window Traffic Classification Sub Data Item The Ethernet Credit Window Traffic Classification Sub Data Item is used to identify the VLAN and PCPs associated with a specific credit window. Credit windows are identified using CID values that have been previously been sent by the modem or are listed in a Credit Window Initialization Data Item carried in the same messages as the sub data item. PCPs are identified in a list of priority fields. An implementation that does not support PCPs, and wants to use credit window flow control for all traffic to a destination or destinations, would indicate with 0 PCPs. Such an implementation could identify a VLAN to use per destination. The format of the Ethernet Credit Window Traffic Classification Sub Data Item is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBD | Length (8) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credit Window Identifier (CID)|NumPCPs| VLAN Identifier (VID) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Pri. 1| Pri. 2| Pri. 3| Pri. 4| Pri. 5| Pri. 6| Pri. 7| Pri. 8| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Length: Variable Length is the number of octets in the sub data item. It is equal to eight (8). Credit Window Identifier (CID): A 16-bit unsigned integer identifying a credit window that has been identified in a Credit Window Initialization Data Item, see Section 4.3.1. Unknown CID values SHOULD be reported and result in associated traffic being dropped. Num PCPs: A 4-bit unsigned integer indicating the number of PCPs carried in the sub data item. A zero (0) indicates a (wildcard) match against any PCP value. Cheng, et al. Expires September 2, 2018 [Page 24] Internet-Draft DLEP DA Credit Extension March 2018 VLAN identifier (VID): A 12-bit unsigned integer field indicating the VLAN to be used in traffic classification. A value of all ones (0xFFF) indicates a wild card and any VID is to be accepted during traffic classification. Zero (0) and any other value are valid values. Priority: Each Priority Field is an 4-bit whose definition includes the PCP field defined in [IEEE.802.1Q_2014] 0 1 2 3 +---+---+---+---+ | PCP |DEI| +---+---+---+---+ PCP: Priority code point DEI: currently unused, MUST be zero A router receiving the Ethernet Traffic Classification Sub Data Item MUST validate the information on receipt prior to the information and data plane update described earlier in this section. The credit window associated with the CID indicated in each data item must be located. It is important to note that the CID value may be present in a Credit Window Initialization Data Item carried in the same message as the sub data item. If the CID is not located, the it MUST be treated as an error as described above. When there are no unknown CIDs, the receiver MUST ensure that each Priority Field value is listed only once across the whole Traffic Classification Data Item. Note, this check is across the data item and not the individual sub data item. If the same Priority Field value is listed more than once within the same Traffic Classification Data Item, the data item MUST be treated as an error as described above. In all cases, the router MUST use validated PCPs in data plane credit window identification as described in Section 4.1. B.2. Other Considerations A full definition for the support of an Ethernet Credit Window Extensions would need to assign a new Extension Type Value as well as the Ethernet Credit Window Traffic Classification Sub Data Item Value. It would also need to fully document the implications of multiple VLAN support, including configuration implications, e.g., limiting value to 0 to indicate PCP-only usage. Cheng, et al. Expires September 2, 2018 [Page 25] Internet-Draft DLEP DA Credit Extension March 2018 Authors' Addresses Bow-Nan Cheng Lincoln Laboratory Massachusetts Institute of Technology 244 Wood Street Lexington, MA 02421-6426 Email: bcheng@ll.mit.edu David Wiggins Lincoln Laboratory Massachusetts Institute of Technology 244 Wood Street Lexington, MA 02421-6426 Email: David.Wiggins@ll.mit.edu Lou Berger LabN Consulting, L.L.C. Email: lberger@labn.net Cheng, et al. Expires September 2, 2018 [Page 26]