



tsvwg                                                           Q. Xiong
Internet-Draft                                                    X. Zhu
Intended status: Informational                           ZTE Corporation
Expires: 26 December 2025                                   24 June 2025


                     Admission Control with Gateway
                 draft-xiong-tsvwg-admission-control-00

Abstract

   This document proposes to enhance the congestion control with the
   admission control mechanism at the gateway to achieve fast feedback
   and per-flow control.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 26 December 2025.

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   provided without warranty as described in the Revised BSD License.






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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
     2.1.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  Admission Control with Gateway  . . . . . . . . . . . . . . .   4
   4.  Admission Control Message Formats . . . . . . . . . . . . . .   5
     4.1.  ICMP Message Format . . . . . . . . . . . . . . . . . . .   5
     4.2.  UDP Message Format  . . . . . . . . . . . . . . . . . . .   5
   5.  Consideration for the Congestion Notification . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Driven by rapid development of big data and AI technologies, the
   performance of data transmission is critical across various
   industries.  The data is transferred via transport layer protocols
   such as Transfer Control Protocol (TCP), Quick UDP Internet
   Connections (QUIC), Remote Direct Memory Access (RDMA) and so on.
   The congestion control algorithms of these protocols are implemented
   by controlling the size of the congestion window and adjusting the
   sending rates upon the network status feedback.  The traditional end-
   to-end congestion control mechanisms will rely on the following
   signals for rate adjustment.

   *  Explicit Congestion Notification (ECN): notify the sender to slow
      down by marking packets in the congestion queue.

   *  Delay and bandwidth measurement (RTP/OWD): estimate the network
      status and bottleneck bandwidth by measuring packet round-trip
      time or one-way delay.

   *  Network telemetry (INT): inserting queuing status in packets to
      provide fine-grained congestion information.













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   When the congestion occurs, the congestion notification will be
   transmitted through the congested link.  The congestion signal path
   is coupled with the data path.  Moreover, it will also delay the
   network feedback due to the long-distance transmission loop,
   resulting in the inability to adjust the transmission rate in a
   timely manner.  It needs to achieve fast feedback nearing the
   senders.  The gateway may be used to get congestion status of the
   network and performs fast feedback and admission control for new
   traffic entering the network from the same gateway.  It will
   significantly mitigate the congested link when the traffic transfers
   to the same destination.

   This document proposes to enhance the congestion control with the
   admission control mechanism at the gateway to achieve fast feedback
   and per-flow control.

2.  Conventions Used in This Document

2.1.  Abbreviations

   RTT: Round-Trip Time

   TCP: Transfer Control Protocol

   RDMA: Remote Direct Memory Access Round-Trip Time

   QUIC: Quick UDP Internet Connections

   ECN: Explicit Congestion Notification

   PFC: Priority-based Flow Control

   RoCEv2: RDMA over Converged Ethernet version 2

2.2.  Requirements Language

   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.










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3.  Admission Control with Gateway

   Multiple source clients may share the same gateway, potentially
   directing significant traffic volume through it.  If these traffic
   targets the same destination server, it may converge onto a single
   physical link.  Upon detecting congestion, the gateway can record the
   states and apply immediate congestion control to any subsequent
   traffic for that server.  Furthermore, the gateway can perform
   admission control, when new traffic arrives, it may reject or pause
   new flows to prevent worsening existing congestion.

                 3-Congestion Notification
        ****************************************************
        *                     *                            *
        *                     *                            *
        *                     *                            *
        V                     V                            *
    +--------+ 1-Traffic A +-------+     +-------+     +---+---+     +-------+
    |Client A|<----------->|Gateway|<--->|Node X |<--->|Node Y |<--->|Server |
    +--------+      +----->+-------+     +-------+     +-------+     +-------+
         4-Traffic B|  ****+                           2-Congestion
    +--------+      |  *                                 Occurs
    |Client B+<-----+  * 5-Admission Control
    +--------+<*********

                         Figure 1: Admission Control at Gateway

   The example of admission control at gateway is shown in Figure 1 and
   the steps are as follows.

   Step 1: the client A sends the traffic to the server along the path
   of network gateway, node X and node Y.

   Step 2: a congestion occurs at the node Y.

   Step 3: the node Y triggers a congestion notification to the gateway
   or the client A, the gateway saves the congestion status.

   Step 4: the client B sends the traffic to the server entering from
   gateway.

   Step 5: the gateway performs the admission control based on the
   congestion information to mitigate the congestion when the traffic is
   sending to the same server.







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4.  Admission Control Message Formats

4.1.  ICMP Message Format

   The admission control message sent from gateway may be a ICMP message
   which is formatted as Figure 2.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Type = TBD1   |  Code = TBD2  |           Checksum            |
      +---------------+---------------+-------------------------------+
      |S|    Flags    |                   Reserved                    |
      +-+-------------+-----------------------------------------------+
      ~                    Source Address                             ~
      ----------------------------------------------------------------+
      ~                    Destination Address                        ~
      ----------------------------------------------------------------+
      ~                    Flow  Identifier                           ~
      ----------------------------------------------------------------+
      |       Pause Unit             |          Reserved              |
      ----------------------------------------------------------------+

              Figure 2: Admission Control Message Format with ICMP

   Type and Code: TBD 1 and TBD2, the fields indicate the admission
   control type and code.

   Source Address (variable): indicates the IPv4 or IPv6 address of the
   sender.

   Destination Address (variable): indicates the IPv4 or IPv6 address of
   the receiver.

   Flow Identifier (variable): it indicates the IP 5 tuples when
   transmitting TCP or QUIC data and it also indicates source QP (Queue
   Pair) and destination QP when transmitting RDMA data.

   Pause Unit (16bits): indicates the quanta time when the sender must
   stop sending the specified traffic after receiving a pause frame.

4.2.  UDP Message Format

   The admission control message sent from gateway may be a UDP message
   which is formatted as Figure 3.






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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        UDP Source Port        |  UDP Destination Port = TBD3  |
      +-------------------------------+-------------------------------+
      |           UDP Length          |          UDP Checksum         |
      +-------------------------------+-------------------------------+
      ~                    Source Address                             ~
      ----------------------------------------------------------------+
      ~                    Destination Address                        ~
      ----------------------------------------------------------------+
      ~                    Flow  Identifier                           ~
      ----------------------------------------------------------------+
      |       Pause Unit             |          Reserved              |
      ----------------------------------------------------------------+

           Figure 3: Admission Control Message Format with UDP

   UDP Header: The UDP header as specified in [RFC768] includes the UDP
   source port, UDP destination port, UDP length, and UDP checksum.

   UDP Destination port: TBD3, indicates a new well-known UDP
   destination port needs to be allocated for this admission control
   message.

   The other fields are the same with section 4.1.

5.  Consideration for the Congestion Notification

   The gateway may collect the congestion information as following:

   *The network may signal congestion by ECN markings, and the receiver
   will pass this information back to the sender in transport-layer
   acknowledgements.  The gateway needs to enable the function of
   notification intercepting to get the information of congestion.

   *The network may implement the classical stepwise back pressure with
   dedicated Ethernet pause frame such as Priority-based Flow Control
   (PFC) frame.  And the congestion status may be stepwise notified from
   congestion point to the gateway.

   *The network may notify the sender with the congestion status
   directly by the messages defined in section 4, or by a dedicated
   congestion notification packet as per
   [I-D.xiao-rtgwg-rocev2-fast-cnp] when RoCv2 implements . The gateway
   needs to enable the function of notification intercepting to get the
   information of congestion.




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   *The network may notify the gateway (as a proxy) with the congestion
   status directly by a dedicated congestion notification packet as per
   [I-D.xiao-rtgwg-proxy-congestion-notification].

6.  Security Considerations

   To be discussed in future versions of this document.

7.  IANA Considerations

   TBD.

8.  Informative References

   [I-D.xiao-rtgwg-proxy-congestion-notification]
              Min, X., "Proxy for Congestion Notification", Work in
              Progress, Internet-Draft, draft-xiao-rtgwg-proxy-
              congestion-notification-00, 16 June 2025,
              <https://datatracker.ietf.org/doc/html/draft-xiao-rtgwg-
              proxy-congestion-notification-00>.

   [I-D.xiao-rtgwg-rocev2-fast-cnp]
              Min, X. and lihesong, "Fast Congestion Notification Packet
              (CNP) in RoCEv2 Networks", Work in Progress, Internet-
              Draft, draft-xiao-rtgwg-rocev2-fast-cnp-03, 9 June 2025,
              <https://datatracker.ietf.org/doc/html/draft-xiao-rtgwg-
              rocev2-fast-cnp-03>.

   [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/rfc/rfc2119>.

   [RFC768]   "*** BROKEN REFERENCE ***".

   [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/rfc/rfc8174>.

Authors' Addresses

   Quan Xiong
   ZTE Corporation
   Email: xiong.quan@zte.com.cn


   Xiangyang Zhu
   ZTE Corporation



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   Email: zhu.xiangyang@zte.com.cn


















































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