TSVWG                                                              Z. Du
Internet-Draft                                              China Mobile
Intended status: Informational                            8 January 2025
Expires: 12 July 2025


            Out-of-order Insensitive Traffic In the Network
           draft-du-tsvwg-out-of-order-insensitive-traffic-00

Abstract

   This document describes a kind of out-of-order insensitive traffic in
   the transport network, and the related load balancing mechanism for
   it.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on 12 July 2025.

Copyright Notice

   Copyright (c) 2025 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
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   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



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   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Enabling Per-packet LB for Specific Flows . . . . . . . . . .   3
   3.  Considerations About Specific Mark  . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Load balancing (LB) in the network is important, which can make the
   link loads in the network similar so as to avoid potential partial
   congestion in the network.  Two basic load balancing methods
   supported in the packet forwarding equipment are the per-packet LB,
   and the per-flow LB.

   In the per-packet LB mechanism, when a flow comes, the packets of the
   flow will be distributed to the paths with the same cost in a round-
   robin manner.  Hence, the load of the paths will be similar.
   However, the different paths may have different latencies to the
   destination, the packets in the flow will potentially be out-of-order
   when they arrive at the destination.  For some applications, for
   example, the real time audio or video service, it is no recommended
   to use the per-packet LB mechanism.

   In the per-flow LB mechanism, when a packet comes, some information
   in the packet header will be HASHed and the packet will be forwarded
   to a path accordingly if multiple paths with the same cost exist.
   The packets of the same flow will have the same HASH value so that no
   out-of-order will take place at the destination due to the per-flow
   LB.

   In the current network, the network layer (IP layer) is not aware of
   the service requirement of the flow, i.e., it is not aware about
   whether the flow is out-of-order sensitive or insensitive.
   Therefore, in the current transport network, the per-flow LB will be
   enabled by default.





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   However, the result of the per-packet LB will normally be better than
   the per-flow LB.  The result of the per-flow LB will depend on
   whether the sizes of the flows are even.  If there are large flows
   and they are distributed to the same path because they have the same
   HASH value, the network may become partial congested.

   In this situation, we may deploy an scheduler in the network, which
   can be aware of the network traffic status, and make some policy
   decision to do the traffic engineering for the network.  It is a
   little complicated, and can only do the optimization after the
   congestion happens.

   In this document, we propose some mechanisms to enable per-packet LB
   for specific flows, which can be regarded as a kind of precaution
   mechanism.

2.  Enabling Per-packet LB for Specific Flows

   To enable the per-packet LB in the transport network, both the edge
   device and the forwarding device will be involved.  The edge device
   may be the user's terminal or an edge router which can mark the
   packets of the users.  The forwarding device is the device that along
   the path of the packet, which will receive the packets sent out by
   the edge device.

   In the edge device, the specific traffic needs to be marked as out-
   of-order insensitive.  Thus, each packet of the traffic would include
   a specific mark in its packet header when it is sent out by the edge
   device.  By comparison, normal traffic will not be marked with the
   specific mark.

   In the forwarding device, both the per-flow LB and the per-packet LB
   is enabled.  The packets without the specific mark will be treated as
   usual, i.e., load balancing by using the per-flow LB mechanism, and
   the packets with the specific mark will be treated specifically.  For
   example, we can do load balance for the packets by using the per-
   packet LB mechanism.


3.  Considerations About Specific Mark

   In this section, we will describe the considerations about the
   specific mark, which indicates that the packet is out-of-order
   insensitive.







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   In [RFC8622], a lower-effort traffic is proposed with a DSCP
   codepoint as "000001".  The traffic is described as with a priority
   lower than the BE traffic, and a specific lower-than-BE transport
   protocol is developed for it [RFC6817].

   The out-of-order insensitive traffic in this document has a different
   semantic meaning compared to the lower-effort traffic.  Similarly, we
   can occupy a specific DSCP codepoint to mark the out-of-order
   insensitive packets.  In details, the DSCP codepoint will be found in
   the ToS (Type of Service) field of the IPv4 header, or in the TC
   (Traffic Class) field of the IPv6 header.  In this case, the DSCP
   codepoint would indicate both the QoS level and the out-of-order
   insensitive information.

   Alternatively, we can also consider mark the out-of-order insensitive
   packets by using a specific bit in the packet header outside of the
   ToS/TC field.  In this case, the meanings of the DSCP codepoints need
   not to be changed; however, a new place needs to be found to convey
   the specific bit.


4.  IANA Considerations

   TBD.

5.  Security Considerations

   TBD.

6.  Acknowledgements

   TBD.

7.  References

7.1.  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>.

7.2.  Informative References

   [RFC6817]  Shalunov, S., Hazel, G., Iyengar, J., and M. Kuehlewind,
              "Low Extra Delay Background Transport (LEDBAT)", RFC 6817,
              DOI 10.17487/RFC6817, December 2012,
              <https://www.rfc-editor.org/info/rfc6817>.



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   [RFC8622]  Bless, R., "A Lower-Effort Per-Hop Behavior (LE PHB) for
              Differentiated Services", RFC 8622, DOI 10.17487/RFC8622,
              June 2019, <https://www.rfc-editor.org/info/rfc8622>.

Author's Address

   Zongpeng Du
   China Mobile
   No.32 XuanWuMen West Street
   Beijing
   100053
   China
   Email: duzongpeng@foxmail.com






































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