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Versions: (draft-cheng-manet-dlep-da-credit-extension) 00 01 02 03 04

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



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   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



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   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.






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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.





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   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.





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   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,




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   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




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   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):





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      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.








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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.




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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.



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   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:











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       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



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   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



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   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:







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        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



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   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



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   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




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   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.



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   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



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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:
















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   +-------------+------------------------------+----------------------+
   | 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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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,
              <https://www.rfc-editor.org/info/rfc8175>.

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.






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   [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,
              <http://ieeexplore.ieee.org/servlet/
              opac?punumber=6991460>.

   [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,
              <https://www.rfc-editor.org/info/rfc2474>.

   [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,
              <https://www.rfc-editor.org/info/rfc2475>.

   [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,
              <https://www.rfc-editor.org/info/rfc8126>.

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



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   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.



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   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.



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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



























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