In-band Edge-to-Edge Round Trip Time Measurement

Document Type Active Internet-Draft (individual)
Authors Haoyu Song  , Linda Dunbar 
Last updated 2021-05-31
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IPPM                                                             H. Song
Internet-Draft                                                  D. Linda
Intended status: Standards Track                  Futurewei Technologies
Expires: December 2, 2021                                   May 31, 2021

            In-band Edge-to-Edge Round Trip Time Measurement


   This draft describes a lightweight in-band edge-to-edge network round
   trip time measurement architecture and suggests implementations.  By
   augmenting the IOAM E2E option header, the process can be fully done
   in data plane without needing to involve the control plane to
   maintain any states.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.

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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   This Internet-Draft will expire on December 2, 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   ( in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  In-band E2E RTT Measurement Architecture  . . . . . . . . . .   3
   3.  Implementation Considerations . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   In-network service-based traffic engineering or load balancing needs
   to monitor particular flows' edge-to-edge performance, such as round
   trip time (RTT), in the operator's network domain.  The host-based
   ping using ICMPv6 [RFC4443] is of no use because it is usually beyond
   the access of network operators.  The router-based ping, as an active
   measurement approach, cannot reflect the real performance of the
   specific flows under scrutiny.  This is also true for the other
   active measurement approaches such as TWAMP [RFC5357].

   In-situ OAM (IOAM) [I-D.ietf-ippm-ioam-data] supports in-band flow-
   based performance measurement.  However, on the one hand, the IOAM
   trace option is too heavy for the applications which do not care
   about the per-hop performance; on the other hand, the IOAM E2E option
   only supports the one-way measurement.

   Alternate Marking(AM) [RFC8321], mainly designed for one-way
   measurement, can be used to measure the two-way edge-to-edge delay if
   both edges initiate a one-way measurement session.  However, AM's
   measurement interval needs to be large enough to avoid the
   measurement ambiguity, and it requires both edges to conduct the
   measurements and export results to a controller.

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   We need a lightweight in-band flow RTT measurement method.
   "Lightweight" means the extra header overhead is low, and the extra
   network processing overhead is also low.  A network operator should
   be able to pick a flow to monitor and get find-grained per-packet RTT
   measurement for edge to edge.  Moreover, the method should be
   stateless and does not need a control plane to maintain sessions.
   Depending on the application scenario and the network domain scope,
   the edge can extend to the host, the network interface card (NIC), or
   the network switch or router.  To this end, we propose an in-band
   edge-to-edge RTT measurement method and suggest the implementation

   Such measurement only reflects the network delay for a flow but
   excludes the application layer delay incurred by server or client.

2.  In-band E2E RTT Measurement Architecture

   The measurement architecture is shown in Figure 1.  The controller,
   either on a remote machine or on the edge node's control plane,
   configures the ingress edge node to measure some flow's RTT between
   the ingress edge and the egress edge.  The ingress edge node uses ACL
   to filter the flow packets and, at given interval or probability, add
   the timestamp and the other metadata to the selected packets.  The
   egress edge, after capturing the data, either piggyback the data on a
   reverse flow packet, or generate a feedback packet carrying the data
   back to the ingress edge node.  Once the ingress edge node receives
   the feedback data, it sends the data along with the current timestamp
   to the controller.  The controller can then calculate the flow RTT
   and react with followup actions.

   The RTT calculation is done in the slow path, the metadata incurs
   only small and fix header overhead, and the nodes in the domain does
   not do any processing.  All these make the measurement lightweight,
   accurate, and have little impact to the network forwarding

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                   |      |
                   |Ctrl. |
                   |      |
                     |  ^
             Config. |  | Export
                     V  |
     +------+      +----+-+    Forwarding    +------+      +------+
     |      | pkt. |      +-----......------>|      | pkt. |      |
     |Client+----->| Edge |                  | Edge +----->|Server|
     |      |      |      |<----......-------+      |      |      |
     +------+      +------+    Feedback      +------+      +------+

                   |<--  Operator Network Domain -->|

                   Figure 1: In-band E2E RTT Measurement

   To differentiate a feedback packet from an original packet, a flag
   needs to be raised in the feedback.  Optionally, to correlate a
   feedback with its original packet, the original packet can also
   include an identifier (e.g., a sequence number) which the feedback
   packet will carry back as well.  The ingress edge node can use the
   reverse flow ID plus the identifier to pair an original packet with
   its feedback.

   The feedback can also include some other local data at the egress
   edge (e.g., the egress edge node ID or the egress flow statistics)
   other than simply reflecting the original data back.

3.  Implementation Considerations

   One approach to implement the in-band E2E RTT measurement is to use
   the IOAM E2E option augmented with the feedback mechanism.  Current
   IOAM E2E option only sends one-way data from one edge to the other
   edge.  The data fields can include the ingress edge timestamp which
   is exactly what is needed.  Moreover, the data fields can also
   include a packet sequence number used for correlating the feedback
   packet with the original packet.  However, current IOAM E2E option
   lacks a feedback mechanism.  It has no flag field reserved in its
   current option header specification, so it is not easy to indicate
   the feedback packets.

   To enable the two-way measurement behavior, we need to add some
   indicator to the IOAM E2E option header to indicate the request for a
   feedback.  We also need another indicator to tell if the current
   packet is a feedback.

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   To support this, we can either introduce another IOAM two-way E2E
   option while keeping the current IOAM E2E option unchanged, or simply
   modify the current IOAM E2E option header specification to extend its
   usage.  The simplest modification is to reserve a few flag bits and
   among them, two bits are used for the two-way measurement.  One
   possible layout is shown in Figure 2.  Alternatively, the flags can
   take several bits from the Namespace-ID field.

       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
      |        Namespace-ID           | Flags |    IOAM-E2E-Type      |
      |                                                               |
      |       E2E Option data field determined by IOAM-E2E-Type       |
      |                                                               |

                 Figure 2: Modified IOAM E2E Option Header

   The data field can carry the timestamp, the sequence number, of a
   unique packet identifier number.  Other data types can also be
   carried to enrich the feedback information.

   A packet can serve as both a forward packet and a feedback packet
   when both flags are set.  In this case, there are two records for
   each data type in the data field.  The forward packet's data are
   located in front of the feedback packet's data.

4.  Security Considerations

   To prevent the timestamp to be maliciously altered during the packet
   forwarding, the ingress edge can instead keep the timestamp locally
   and only send a packet identifier (e.g., a random data).  When a
   reverse flow packet carrying the same identifier is received, the
   current timestamp along with the saved timestamp are forwarded to the

   The ingress edge node can limit the frequency of measurement to the
   flow packets.  The egress edge node can also rate limit the feedback.
   So the potential DoS attack can be mitigated.

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5.  IANA Considerations

   Depending on the discussion output, either a registry for a new IOAM
   option is required or a modification to the current IOAM E2E option
   specification is needed.

6.  Contributors


7.  Acknowledgments


8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

8.2.  Informative References

              Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
              for In-situ OAM", draft-ietf-ippm-ioam-data-12 (work in
              progress), February 2021.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, DOI 10.17487/RFC5357, October 2008,

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   [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, <>.

Authors' Addresses

   Haoyu Song
   Futurewei Technologies
   Santa Clara


   Linda Dunbar
   Futurewei Technologies


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