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Versions: 00 01 02 draft-gandhi-mpls-ioam-sr

SPRING Working Group                                      R. Gandhi, Ed.
Internet-Draft                                                    Z. Ali
Intended status: Standards Track                             C. Filsfils
Expires: February 23, 2020                                  F. Brockners
                                                     Cisco Systems, Inc.
                                                                  B. Wen
                                                                V. Kozak
                                                                 Comcast
                                                         August 22, 2019

          Segment Routing with MPLS Data Plane Encapsulation
                          for In-situ OAM Data
                  draft-gandhi-spring-ioam-sr-mpls-02


Abstract

   In-situ Operations, Administration, and Maintenance (IOAM) records
   operational and telemetry information in the data packet while the
   packet traverses a path between two nodes in the network.  Segment
   Routing (SR) technology leverages the source routing paradigm.  This
   document defines how IOAM data fields are transported with the
   Segment Routing with MPLS data plane (SR-MPLS) encapsulation.  The
   procedures defined are also equally applicable to all other MPLS data
   plane encapsulations.

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
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

Copyright Notice

   Copyright (c) 2019 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
   Provisions Relating to IETF Documents



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   (http://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
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   described in the Simplified BSD License.



Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Requirement Language . . . . . . . . . . . . . . . . . . .  3
     2.2.  Abbreviations  . . . . . . . . . . . . . . . . . . . . . .  3
   3.  IOAM Data Field Encapsulation in SR-MPLS Header  . . . . . . .  3
   4.  Procedure for Edge-to-Edge IOAM  . . . . . . . . . . . . . . .  5
     4.1.  Edge-to-Edge IOAM Indicator Labels . . . . . . . . . . . .  6
   5.  Procedure for Hop-by-Hop IOAM  . . . . . . . . . . . . . . . .  7
   6.  Considerations for ECMP  . . . . . . . . . . . . . . . . . . .  7
   7.  Node Capability  . . . . . . . . . . . . . . . . . . . . . . .  7
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   10.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  8
   11.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  8
     11.1.  Normative References  . . . . . . . . . . . . . . . . . .  8
     11.2.  Informative References  . . . . . . . . . . . . . . . . .  9
   Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9



1.  Introduction

   In-situ Operations, Administration, and Maintenance (IOAM) records
   operational and telemetry information within the packet while the
   packet traverses a particular network domain.  The term "in-situ"
   refers to the fact that the IOAM data fields are added to the data
   packets rather than being sent within the probe packets specifically
   dedicated to OAM or Performance Measurement (PM).  The IOAM data
   fields are defined in [I-D.ietf-ippm-ioam-data], and can be used for
   various use-cases for OAM and PM.

   Segment Routing (SR) technology leverages the source routing paradigm
   [I-D.ietf-spring-segment-routing-mpls].  A node steers a packet
   through a controlled set of instructions, called segments, by
   pre-pending the packet with an SR header.  In the MPLS data plane,



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   the SR header is instantiated through a label stack.

   This document defines how IOAM data fields are transported with the
   SR with MPLS data plane (SR-MPLS) encapsulation.  The procedures
   defined are also equally applicable to all other MPLS data plane
   encapsulations.


2.  Conventions

2.1.  Requirement 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 [RFC2119] [RFC8174]
   when, and only when, they appear in all capitals, as shown here.

2.2.  Abbreviations

   Abbreviations used in this document:

   ECMP      Equal Cost Multi-Path

   IOAM      In-situ Operations, Administration, and Maintenance

   MPLS      Multiprotocol Label Switching

   OAM       Operations, Administration, and Maintenance

   PBT       Postcard Based Telemetry

   PM        Performance Measurement

   PoT       Proof-of-Transit

   SR        Segment Routing

   SR-MPLS   Segment Routing with MPLS Data plane


3.  IOAM Data Field Encapsulation in SR-MPLS Header

   SR-MPLS encapsulation is defined in
   [I-D.ietf-spring-segment-routing-mpls].  The IOAM data fields are
   defined in [I-D.ietf-ippm-ioam-data].  IOAM data fields are carried
   in the SR-MPLS header as shown in Figure 1 and Figure 2.  More than
   one trace options can be present in the IOAM data fields.  The
   Indicator Label is added at the bottom of the MPLS label stack (S



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   flag set to 1) to indicate the presence of the IOAM data field(s) in
   the MPLS header.


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  IOAM Indicator Label TBA1            | TC  |1|  TTL          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
   |  IOAM-Type    | IOAM HDR LEN  |    RESERVED                   |  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  I
   |                                                               |  O
   |                                                               |  A
   ~                 IOAM Option and Data Space                    ~  M
   |                                                               |  |
   |                                                               |  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
   |                                                               |
   |                                                               |
   |                 Payload + Padding (L2/L3/ESP/...)             |
   |                                                               |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 1: IOAM data encapsulation in SR-MPLS Header


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  IOAM and Flow Indicator Label TBA2   | TC  |1|  TTL          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0|      Flow label                       |  RESERVED     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
   |  IOAM-Type    | IOAM HDR LEN  |    RESERVED                   |  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  I
   |                                                               |  O
   |                                                               |  A
   ~                 IOAM Option and Data Space                    ~  M
   |                                                               |  |
   |                                                               |  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
   |                                                               |
   |                                                               |
   |                 Payload + Padding (L2/L3/ESP/...)             |
   |                                                               |
   |                                                               |



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   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 2: IOAM data encapsulation with Flow Label in SR-MPLS Header


   Indicator Label and Flow Label as defined in this document.

   The fields related to the encapsulation of IOAM data fields in the
   SR-MPLS header are defined as follows:

    IOAM-Type:  8-bit field defining the IOAM Option type, as defined in
      Section 7.2 of [I-D.ietf-ippm-ioam-data].

    IOAM HDR LEN:  8-bit unsigned integer.  Length of the IOAM HDR in
      4-octet units.

    RESERVED:  8-bit reserved field MUST be set to zero upon
      transmission and ignored upon receipt.

    IOAM Option and Data Space:  IOAM option header and data is present
      as defined by the IOAM-Type field, and is defined in Section 4 of
      [I-D.ietf-ippm-ioam-data].


4.  Procedure for Edge-to-Edge IOAM

   This section summarizes the procedure for data encapsulation and
   decapsulation for IOAM Edge-to-Edge Option Type
   [I-D.ietf-ippm-ioam-data] in SR-MPLS header.

   o  The encapsulating node inserts the IOAM Indicator Label or IOAM
      Flow Indicator Label with Flow Label and one or more IOAM data
      field(s) in the MPLS header.  The procedure to generate the Flow
      Label is outside the scope of this document.

   o  The decapsulating node "forwards and punts the timestamped copy"
      of the data packet including IOAM data fields when the node
      recognizes the IOAM Indicator Label and IOAM Flow Indicator Label.
       The copy of the data packet is punted to the slow path for OAM
      processing and is not necessarily punted to the control-plane.
      The receive timestamp is required by various OAM use-cases.

   o  The decapsulating node processes the IOAM data field(s) using the
      procedures defined in [I-D.ietf-ippm-ioam-data].  An example of
      IOAM processing may be to export the data fields, send data fields
      via Telemetry, etc.




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   o  The decapsulating node also pops the Indicator Label and the IOAM
      data fields from the MPLS header.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Segment List(1)        | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Segment List(n)        | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                PSID                   | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Packet as shown in Figure 1 or Figure 2        |
    .                                                               .
    +---------------------------------------------------------------+

                 Figure 3: Data Packet over SR-MPLS Policy


4.1.  Edge-to-Edge IOAM Indicator Labels

   IOAM Indicator Label (value TBA1) and IOAM and Flow Indicator Label
   (value TBA2) are used to indicate the presence of the IOAM data field
   in the MPLS header.

   The Indicator Label with value TBA2 is used to carry a second label
   underneath with protocol value 0000b and 20-bit Flow Label.  The
   protocol value 0000b allows to avoid incorrect IP header based
   hashing over ECMP paths that uses the value 0x4 (for IPv4) and value
   0x6 (for IPv6) [RFC4928].  The Flow Label identifies the traffic flow
   that can be used for IOAM purpose as well as for hashing over ECMP
   paths.

   The IOAM Indicator Label and IOAM and Flow Indicator Label can be
   allocated using one of the following methods:

   o  Labels assigned by IANA with value TBA1 and TBA2 from the Extended
      Special-Purpose MPLS Values [mpls-spl-terminology].

   o  Labels allocated by a controller from the global table of the
      decapsulating node.  The controller provisions the label on both
      encapsulating and decapsulating nodes.

   o  Labels allocated by the decapsulating node.  The signaling



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      extension for this is outside the scope of this document.


5.  Procedure for Hop-by-Hop IOAM

   The hop-by-hop IOAM includes IOAM-Types IOAM Pre-allocated Trace
   Option Type, IOAM Incremental Trace Option Type and IOAM POT Option
   Type.

   Different Indicator Labels (TBA3 and TBA4) are used for hop-by-hop
   IOAM.

   The details for hop-by-hop IOAM will be added in a future version of
   the document.


6.  Considerations for ECMP

   The encapsulating node needs to make sure the IOAM data field does
   not start with a well known IP protocol value (e.g. 0x4 for IPv4 and
   0x6 for IPv6) as it can alter the hashing function for ECMP that uses
   the IP header.  This can be achieved by using the IOAM and Flow
   Indicator Label (value TBA2 and TBA4) that follows by protocol value
   0000b.  This approach is consistent with the use of utilizing 0000b
   as the first nibble after the MPLS label stack, as described in
   [RFC4928] [RFC4385].

   Note that the hashing function for ECMP that uses the labels from the
   MPLS header may also now include the Indicator Label.

   The entropy label can be used for hashing function for ECMP as
   defined in [RFC6790].


7.  Node Capability

   The decapsulating node that has to pop the Indicator Label, data
   fields, and perform the IOAM function may not be capable of
   supporting it.  The encapsulating node needs to know if the
   decapsulating node can support the IOAM function.  The signaling
   extension for this capability exchange is outside the scope of this
   document.


8.  IANA Considerations

   IANA maintains the "Special-Purpose Multiprotocol Label Switching
   (MPLS) Label Values" registry (see



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   <https://www.iana.org/assignments/mpls-label-values/mpls-label-
   values.xml>).  IANA is requested to allocate IOAM Indicator Label
   value and IOAM and Flow Indicator value from the "Extended
   Special-Purpose MPLS Label Values" registry:

    +-------------+-----------------------------------+---------------+
    | Value       | Description                       | Reference     |
    +-------------+-----------------------------------+---------------+
    | TBA1        | E2E IOAM Indicator Label          | This document |
    +-------------+-----------------------------------+---------------+
    | TBA2        | E2E IOAM and Flow Indicator Label | This document |
    +-------------+-----------------------------------+---------------+
    | TBA3        | HbH IOAM Indicator Label          | This document |
    +-------------+-----------------------------------+---------------+
    | TBA4        | HbH IOAM and Flow Indicator Label | This document |
    +-------------+-----------------------------------+---------------+


9.  Security Considerations

   The security considerations of SR-MPLS are discussed in
   [I-D.ietf-spring-segment-routing-mpls], and the security
   considerations of IOAM in general are discussed in
   [I-D.ietf-ippm-ioam-data].

   IOAM is considered a "per domain" feature, where one or several
   operators decide on leveraging and configuring IOAM according to
   their needs.  Still, operators need to properly secure the IOAM
   domain to avoid malicious configuration and use, which could include
   injecting malicious IOAM packets into a domain.


10.  Acknowledgements

   The authors would like to thank Shwetha Bhandari and Vengada Prasad
   Govindan for the discussions on IOAM.  The authors would also like to
   thank Tarek Saad, Loa Andersson and Cheng Li for providing many
   useful comments.


11.  References

11.1.  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.




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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", RFC 8174, May 2017.

   [I-D.ietf-spring-segment-routing-mpls]  Bashandy, A., Filsfils, C.,
              Previdi, S., Decraene, B., Litkowski, S., and R. Shakir,
              "Segment Routing with MPLS data plane",
              draft-ietf-spring-segment-routing-mpls, work in progress.

   [I-D.ietf-ippm-ioam-data]  Brockners, F., Bhandari, S., Pignataro,
              C., Gredler, H., Leddy, J., Youell, S., Mizrahi, T.,
              Mozes, D., Lapukhov, P., Chang, R., and Bernier, D., "Data
              Fields for In-situ OAM", draft-ietf-ippm-ioam-data, work
              in progress.

11.2.  Informative References

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, February 2006.

   [RFC4928]  Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
              Cost Multipath Treatment in MPLS Networks", BCP 128, RFC
              4928, June 2007.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, November 2012.

   [mpls-spl-terminology]  L. Andersson, et al. "Special Purpose Label
              terminology", draft-ietf-mpls-spl-terminology, work in
              progress.



Contributors

   Sagar Soni
   Cisco Systems, Inc.
   Email: sagsoni@cisco.com


   Patrick Khordoc
   Cisco Systems, Inc.
   Email: pkhordoc@cisco.com


Authors' Addresses




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   Rakesh Gandhi (editor)
   Cisco Systems, Inc.
   Canada

   Email: rgandhi@cisco.com


   Zafar Ali
   Cisco Systems, Inc.

   Email: zali@cisco.com


   Clarence Filsfils
   Cisco Systems, Inc.
   Belgium

   Email: cf@cisco.com


   Frank Brockners
   Cisco Systems, Inc.
   Hansaallee 249, 3rd Floor
   DUESSELDORF, NORDRHEIN-WESTFALEN  40549
   Germany

   Email: fbrockne@cisco.com


   Bin Wen
   Comcast

   Email: Bin_Wen@cable.comcast.com


   Voitek Kozak
   Comcast

   Email: Voitek_Kozak@comcast.com












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