Alternate marking usage for loss location in per-packet load balancing networks
draft-liu-opsawg-alt-mark-per-packet-00

OPSAWG                                                            K. Liu
Internet-Draft                                                   R. Wang
Intended status: Informational                              China Mobile
Expires: 3 September 2026                                   2 March 2026

 Alternate marking usage for loss location in per-packet load balancing
                                networks
                draft-liu-opsawg-alt-mark-per-packet-00

Abstract

   Many per-packet load balancing schemes have been proposed to mitigate
   network load imbalances.  However, due to the randomness of packet
   paths, loss location is challenging in per-packet load balancing
   networks.  An efficient solution is to leverage the alternate packet
   marking technique.  This draft analyzes the usage and requirements of
   alternate packet marking for packet loss detection and location in
   per-packet load balancing networks.

Status of This Memo

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   This Internet-Draft will expire on 3 September 2026.

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   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Use cases in per-packet load balancing networks . . . . . . .   3
     2.1.  Monitoring all packet loss on switches  . . . . . . . . .   4
     2.2.  Monitoring packet loss of certain services  . . . . . . .   4
     2.3.  Locating packet loss in probing systems . . . . . . . . .   4
     2.4.  Low overhead requirements . . . . . . . . . . . . . . . .   4
     2.5.  Compatibility requirements  . . . . . . . . . . . . . . .   5
   3.  Use cases in packet-spraying networks . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   To mitigate network load imbalance, many per-packet load balancing
   schemes have been proposed.  These schemes spray packets onto
   parallel paths to fundamentally eliminate network load imbalance.
   However, packet spraying brings challenges for loss detection.  In
   flow-based networks, packets with the same 5-tuple traverse the same
   network path.  By collecting loss packets and replaying their
   5-tuples via path tracking tools such as Traceroute or INT, their
   network paths can be easily obtained for loss location.  However, in
   per-packet load balancing networks, packets with the same 5-tuple may
   be randomly routed to different network paths, and the replayed
   packets may take different paths, leading to incorrect path tracking
   and loss location.

   One possible loss location scheme in per-packet load balancing
   networks is to monitor packet loss on switches.  However, traditional
   packet loss monitoring on switches cannot accurately detect all
   packet loss, such as silent packet loss.  To accurately detect all
   packet loss on switches, an efficient method is to leverage the
   alternate packet marking technique.  The core workflow of alternate
   packet marking is as follows: Firstly, packets are periodically and

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   alternately marked at the traffic entry points, such as source
   network interface cards (NICs) or top-of-rack (ToR) switches.
   Secondly, in each period, each switch calculates the difference
   between the ingress and egress packet counts in the previous period.
   At the destination point (the destination ToR switch or NIC), the
   marks on the packets are cleared before delivery to the service
   process.  This draft analyzes the usage and requirements of alternate
   packet marking to detect and locate packet loss in per-packet load
   balancing networks.

1.1.  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.

2.  Use cases in per-packet load balancing networks

                       aa bb aa +----------+  aa bb aa
   A      B      A   +----------| Switch 1 |-----------+
------ ------ ------ |   --->   +----------+    --->   |
aaaaaa bbbbbb aaaaaa |                                 | aaaaaa bbbbbb aaaaaa
     +---------+     | aa bb aa +----------+  aa bb aa |     +---------+
-----|  Entry  |-----+----------| Switch 2 |-----------+-----|   DST   |-----
     +---------+     |   --->   +----------+    --->   |     +---------+
          --->       |                                 |         --->
                     | aa bb aa +----------+  aa bb aa |
                     +----------| Switch x |-----------+
                         --->   +----------+    --->

                               Figure 1

   Figure 1 illustrates the workflow of alternate packet marking and
   loss counting in per-packet load balancing networks.  During period
   A, packets are marked with flag "a" at the entry point.  These marked
   packets are sprayed onto parallel paths, and the switches count all
   ingress and egress packets labeled "a".  During period B, packets are
   marked with flag "b", and the switches count all packets labeled "b".
   Since no packets are labeled "a" in period B, their count remains
   unchanged.  Each switch then calculates the difference between the
   number of ingress and egress packets labeled "a" to determine the
   total packet loss in period A.  In the next period A, the switches
   count packets labeled "a" and calculate the difference of packets
   labeled "b".  This process is repeated in subsequent periods.  The

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   alternate marking ensures that the packet count in the last marking
   period remains unchanged, allowing for an accurate loss counting.
   This method can effectively detect nearly all packet loss in
   switching, including silent loss, which can hardly be detected by
   traditional packet loss monitoring on switches.

2.1.  Monitoring all packet loss on switches

   By marking all packets within the cluster alternately and calculating
   the difference between the number of ingress and egress packets on
   each switch, all packet loss in switching can be accurately detected.
   In addition, this method enables accurate loss rate monitoring for
   each switch, which can be used to identify abnormal switch devices.

2.2.  Monitoring packet loss of certain services

   Services typically have varying degrees of sensitivity to packet
   loss.  Some services, such as distributed storage and distributed
   training, are highly sensitive to packet loss.  For these services,
   it is necessary to detect and locate every packet loss.  Conversely,
   some services, such as audio and video streaming, are less affected
   by packet loss.  For these services, focusing only on severe packet
   loss events is typically sufficient.  By marking packets in loss-
   sensitive services merely, switches can focus on packet loss event
   only in these services.

2.3.  Locating packet loss in probing systems

   Network probing systems typically proactively construct probe packets
   to measure network latency and packet loss rates.  By replaying the
   anomalous probe 5-tuples (timeout or high latency) via path tracking
   tools, such as Traceroute or INT, these systems can further locate
   the anomalous device.  However, in per-packet load balancing
   networks, the replayed probes may take different paths, resulting in
   an incorrect fault location.  With alternate probe packet marking,
   the loss of probe packets can be accurately located.

2.4.  Low overhead requirements

   First, this method requires traffic entry points to identify and mark
   specific packets.  Then, all switches in the cluster must recognize
   marked packets and determine their ingress and egress counts.
   Finally, at the destination point, the marks on the packets must be
   cleared before they are delivered to the service process.  These
   steps introduce additional processing and latency overhead.
   Furthermore, if an extra header is used for packet marking,
   additional bandwidth overhead will be incurred.  Therefore, the
   marking method should have minimal overhead to minimize its impact on

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   network performance.

2.5.  Compatibility requirements

   This method requires all entry/destination points to identify
   specific packets and add/remove packet labels.  In addition, it
   requires all switches in the cluster to identify and count marked
   packets.  Therefore, the scheme should be compatible with most
   existing switches to minimize deployment overhead.

3.  Use cases in packet-spraying networks

   The alternate packet marking method, a typical hybrid performance
   monitoring technology, has been standardized via a series of IETF
   RFCs to enable high-precision packet loss detection and localization.

   [RFC8321] laid the foundation for alternate packet marking.  It
   divides service flows into one-bit-marked, alternating blocks and
   calculates packet loss by counting the differences between adjacent
   measurement points.  [RFC8321] supports passive and hybrid modes, and
   can be applied to IP, MPLS, and Ethernet networks.  However, its poor
   anti-out-of-order performance limits its use in high-precision
   applications.  To address this issue, [RFC9341] obsoleted [RFC8321]
   as an enhanced standard.  The new standard (1) introduces unique
   block IDs to address out-of-order and retransmission interference,
   (2) standardizes latency and jitter measurement with D bits, and (3)
   unifies counting alignment.  [RFC9341] greatly improves the
   measurement accuracy.

   As a supplement to [RFC9341], [RFC9342] supports multicast scenarios
   with multi-receiver synchronization.  [RFC9343] defines IPv6
   encapsulation of alternate marking information that can be inserted
   into the hop-by-hop or destination options header.  Therefore, it can
   be applied to IPv6/SRv6 networks.  In terms of supporting RFCs,
   [RFC7799] classifies measurement methods and provides a basis for
   alternate marking.  [RFC6374] (MPLS OAM) enables alternate marking in
   MPLS networks.  In practice, iFIT builds on [RFC9341] and [RFC9343]
   and is widely used in smart metropolitan area networks and data
   center networks.

4.  IANA Considerations

   There are no IANA consideration introduced by this draft.

5.  Security Considerations

   There are no security issues introduced by this draft.

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6.  References

6.1.  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>.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <https://www.rfc-editor.org/info/rfc6374>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <https://www.rfc-editor.org/info/rfc7799>.

   [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>.

   [RFC8321]  Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
              L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
              "Alternate-Marking Method for Passive and Hybrid
              Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
              January 2018, <https://www.rfc-editor.org/info/rfc8321>.

   [RFC9341]  Fioccola, G., Ed., Cociglio, M., Mirsky, G., Mizrahi, T.,
              and T. Zhou, "Alternate-Marking Method", RFC 9341,
              DOI 10.17487/RFC9341, December 2022,
              <https://www.rfc-editor.org/info/rfc9341>.

   [RFC9342]  Fioccola, G., Ed., Cociglio, M., Sapio, A., Sisto, R., and
              T. Zhou, "Clustered Alternate-Marking Method", RFC 9342,
              DOI 10.17487/RFC9342, December 2022,
              <https://www.rfc-editor.org/info/rfc9342>.

   [RFC9343]  Fioccola, G., Zhou, T., Cociglio, M., Qin, F., and R.
              Pang, "IPv6 Application of the Alternate-Marking Method",
              RFC 9343, DOI 10.17487/RFC9343, December 2022,
              <https://www.rfc-editor.org/info/rfc9343>.

Authors' Addresses

   Kefe Liu
   China Mobile
   China

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   Email: liukefei@chinamobile.com

   Ruixue Wang
   China Mobile
   China
   Email: wangruixue@chinamobile.com

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