Optional IS-IS Fragment Timestamping
draft-rigatoni-lsr-isis-fragment-timestamping-01

Network Working Group                                      T. Przygienda
Internet-Draft                                                  C. Barth
Intended status: Standards Track                        Juniper Networks
Expires: 8 March 2025                                   4 September 2024

                  Optional IS-IS Fragment Timestamping
            draft-rigatoni-lsr-isis-fragment-timestamping-01

Abstract

   Many applications in today’s networks rely on reliable and timely
   flooding of link-state information, such as, but not limited to
   Traffic Engineered networks.  If such link-state information is
   delayed it can be difficult for those applications to adequately
   fulfill their intended functionality.  This document describes
   extensions to ISIS supporting distribution of fragment origination
   time.  The origination time can be used to aid troubleshooting and/or
   by the applications themselves to improve their behavior.

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 8 March 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Przygienda & Barth        Expires 8 March 2025                  [Page 1]
Internet-Draft    Optional IS-IS Fragment Timestamping    September 2024

   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 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.  Timestamp TLV . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Operational and Deployment Considerations . . . . . . . . . .   4
   4.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   5.  Informative References  . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Many applications in today’s networks rely on reliable and timely
   flooding of link-state information, such as, but not limited to
   Traffic Engineered networks and advanced telemetry solutions.  If
   such information is delayed during flooding it can be difficult for
   those applications to adequately fulfill their intended purpose.
   This document describes extensions to ISIS allowing it to carry the
   origination time on each fragment.  The origination time can be used
   to aid troubleshooting of large domains and/or by the applications
   themselves to improve their behavior.

   As an example, in case of Traffic Engineered Networks synchronization
   of the Traffic Engineering Database (TED) enables the compute nodes
   to adapt to changes in the network state and/or react to network
   events in a timely manner.  Relying on a synchronized TED while the
   flooding information is delayed can easily lead to service
   degradation due to substandard re-optimization of network load.  The
   origination time proposed in this document is meant to be used by the
   compute nodes or by an operator of Traffic Engineered Network to
   measure any delays incurred in TED synchronization.  The awareness of
   delays in the distribution of information can be incorporated further
   into algorithms and network tooling to improve the responsiveness and
   quality of decisions taken.

Przygienda & Barth        Expires 8 March 2025                  [Page 2]
Internet-Draft    Optional IS-IS Fragment Timestamping    September 2024

2.  Timestamp TLV

   This section defines a new, optional TLV that can be present in any
   fragment.  In case of multiple instances of the TLV in a fragment
   only the first occurrence MUST be used.  The semantics of the TLV is
   the point in time the fragment with the current sequence number has
   been generated.  Its absence signifies that such information is not
   available due to host of possible issues, one of them lack of clock
   with synchronization precise enough.

   For practical purposes, although desirable, timestamping the moment a
   fragment is flooded would be preferable but beside practical
   implementation problems this could generate on different interfaces
   the same fragment with different content which breaks one of the
   fundamental tenants of link-state protocols.  However, an
   implementation is free to choose to use, e.g. the moment the fragment
   is queued for flooding first time rather than the time the version is
   generated.

   To save space the timestamp is following semantically NTP seconds
   epoch [RFC5905] with the exception of an extra bit in the seconds
   field to extend the wrap around and carrying only 2^-8 of a second as
   maximum resolution of the timestamp since this is considered
   sufficient for link-state purposes.  The specification follows
   further guidelines of [RFC8877] as far as possible.

      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      |     Length    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Seconds                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |H|     Frac      |    Prec     |
     +-+-+-+-+-+-+-+-+---------------+

                                  Figure 1

   *  Type: TBD1

   *  Length: ...

   *  Seconds: 4 bytes of number of seconds since the NTP [RFC5905]
      epoch.

Przygienda & Barth        Expires 8 March 2025                  [Page 3]
Internet-Draft    Optional IS-IS Fragment Timestamping    September 2024

   *  H(-Bit): 1 bit.  Extra high order bit is used to prevent wrap-
      around in 2036 and pushes it out to 2242.  The offset can be
      constructed in network order `HB` shifted to left without overflow
      by 32 bits and the `Seconds` field OR'ed into the according value.

   *  Fraction: 8-bits of fraction of the second in units of 2^-8 which
      is equivalent to 1/256 of a second or roughly 4 msecs resolution.

   *  Precision: 7 bits indicating the maximum possible slip (either in
      future or past) of the clock used to generate the timestamp
      (depending on the synchronization protocol) as 2^Precision where
      at minimum of the range signifies 2 msec or better precision and
      the maximum of the range amounts to 256 msec precision or less.  A
      node that cannot achieve this minimum precision required SHOULD
      NOT advertise the fragment timestamp.

3.  Operational and Deployment Considerations

   A requirement for the correct interpretation of the additions
   proposed in this document is an infrastructure capable of
   synchronizing time across devices involved so the timestamps at the
   various points of interest become comparable.  This could be
   accomplished by utilizing NTP [RFC5905], Precision Time Protocol
   (PTP) IEEE Std. 1588 [IEEEstd1588] or 802.1AS [IEEEstd8021AS]
   designed for bridged LANs.  The achieved precision is carried in the
   timestamp of the fragment.

   Though the timestamp can be very useful in deriving measurement of
   behavior in a deployed IS-IS network, e.g.  maximum incurred flooding
   delays between any pair of nodes, it should not be used in any
   attempts to modify the behavior of protocol behavior itself such as
   e.g. influencing flooding rates.  A single badly synchronized clock
   could otherwise change the behavior of parts or even the whole
   network in unpredictable or even detrimental way.

4.  Normative References

   [IEEEstd1588]
              IEEE, "IEEE Standard for a Precision Clock Synchronization
              Protocol for Networked Measurement and Control Systems",
              IEEE Standard 1588,
              <https://ieeexplore.ieee.org/document/4579760/>.

Przygienda & Barth        Expires 8 March 2025                  [Page 4]
Internet-Draft    Optional IS-IS Fragment Timestamping    September 2024

   [IEEEstd8021AS]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks - Timing and Synchronization for Time-Sensitive
              Applications in Bridged Local Area Networks",
              IEEE Standard 802.1AS,
              <https://ieeexplore.ieee.org/document/5741898/>.

5.  Informative References

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
              <https://www.rfc-editor.org/info/rfc5905>.

   [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>.

   [RFC8877]  Mizrahi, T., Fabini, J., and A. Morton, "Guidelines for
              Defining Packet Timestamps", RFC 8877,
              DOI 10.17487/RFC8877, September 2020,
              <https://www.rfc-editor.org/info/rfc8877>.

Authors' Addresses

   Tony Przygienda
   Juniper Networks
   Email: prz@juniper.net

   Colby Barth
   Juniper Networks
   Email: cbarth@juniper.net

Przygienda & Barth        Expires 8 March 2025                  [Page 5]