Segment Routing with MPLS Data Plane Encapsulation for In-situ OAM Data
draft-gandhi-mpls-ioam-sr-01

MPLS Working Group                                        R. Gandhi, Ed.
Internet-Draft                                                    Z. Ali
Intended status: Standards Track                             C. Filsfils
Expires: June 8, 2020                                       F. Brockners
                                                     Cisco Systems, Inc.
                                                                  B. Wen
                                                                V. Kozak
                                                                 Comcast
                                                        December 6, 2019

          Segment Routing with MPLS Data Plane Encapsulation
                          for In-situ OAM Data 
                      draft-gandhi-mpls-ioam-sr-01

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 using 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

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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
 

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   Provisions Relating to IETF Documents
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Table of Contents

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

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.ippm-ioam-data], and can be used for
   various use-cases for OAM and PM.  The IOAM data fields are further
   updated in [I-D.ippm-direct-export] for direct export use-cases and
 

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   in [I-D.ippm-ioam-flags] for loopback, active measurements, etc.

   Segment Routing (SR) technology leverages the source routing paradigm
   [RFC8660].  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, the SR header is instantiated
   through a label stack.  

   This document defines how IOAM data fields are transported using 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

   PM        Performance Measurement

   POT       Proof-of-Transit

   PSID      Path Segment Identifier

   SR        Segment Routing

   SR-MPLS   Segment Routing with MPLS Data plane

3.  IOAM Data Field Encapsulation in MPLS Header

 

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   The IOAM data fields defined in [I-D.ippm-ioam-data] are used.  IOAM
   data fields are carried in the 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 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                 | 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 Encapsulation in 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        | TC  |1|  TTL          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0|      Flow label                       | Block Number  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+ 
   |  IOAM-Type    | IOAM HDR LEN  |    RESERVED                   |  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  I
   |                                                               |  O
   |                                                               |  A
   ~                 IOAM Option and Data Space                    ~  M
   |                                                               |  |
   |                                                               |  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
   |                                                               |
 

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   |                                                               |
   |                 Payload + Padding (L2/L3/ESP/...)             |
   |                                                               |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 2: IOAM Encapsulation with Flow Label in MPLS Header

   IOAM Indicator Label (IIL) and IOAM and Flow Indicator Label (IFIL)
   used are defined in this document.

   The fields related to the encapsulation of IOAM data fields in the
   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.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.ippm-ioam-data].

3.1.  Indicator Labels

   IOAM Indicator Label (value TBA1 or TBA3) and IOAM and Flow Indicator
   Label (value TBA2 or TBA4) are used to indicate the presence of the
   IOAM data field in the MPLS header.  

   The IOAM and Flow Indicator Label (value TBA2 or TBA4) is used to
   carry a second label underneath with protocol value 0000b, 20-bit
   Flow Label and 8-bit Block Number.  

   o  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].  

   o  The Flow Label identifies the traffic flow that can be used for
      IOAM purpose, monitoring a specific traffic flow for latency.

   o  The Block Number can be used to aggregate the IOAM data collected
      in data plane, e.g. compute measurement metrics for each block of
 

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      a flow.

3.2.  Data Packets with SR-MPLS Header

   An example of data packet carrying the SR-MPLS header with Path
   Segment Identifier (PSID) [I-D.spring-mpls-path-segment] with IOAM
   encapsulation is shown in Figure 3.  The Path Segment Identifier
   allows to identify the associated data traffic path (e.g. SR Policy)
   on the egress node being monitored for IOAM.

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

                Figure 3: Data Packet with SR-MPLS Header

   The data packets with IOAM data fields carry only one Indicator Label
   in the MPLS header.  Any intermediate node that adds additional MPLS
   encapsulation in the MPLS header may further update the IOAM data
   fields in the header without inserting another Indicator Label.

4.  Procedure for Edge-to-Edge IOAM

   The Edge-to-Edge (E2E) IOAM includes IOAM Option-Type as Edge-to-Edge
   Option-Type [I-D.ippm-ioam-data].  This section summarizes the
   procedure for data encapsulation and decapsulation for Edge-to-Edge
   IOAM in 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
 

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      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 E2E OAM use-cases.  

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

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

4.1.  Edge-to-Edge IOAM Indicator Label Allocation

   IOAM Indicator Label (value TBA1) and IOAM and Flow Indicator Label
   (value TBA2) are used to indicate the presence of the E2E IOAM data
   field in the MPLS header.  The E2E 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 [I-D.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
      extension for this is outside the scope of this document.

5.  Procedure for Hop-by-Hop IOAM

   The Hop-by-Hop (HbH) IOAM includes IOAM Option-Types IOAM
   Pre-allocated Trace Option-Type, IOAM Incremental Trace Option-Type
   and IOAM Proof of Transit (POT) Option-Type [I-D.ippm-ioam-data]. 
   This section summarizes the procedure for data encapsulation and
   decapsulation for Hop-by-hop IOAM in 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.
 

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   O. The transit and decapsulating node enabled with IOAM functions
      "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 hop-by-hop OAM use-cases.  

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

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

5.1.  Hop-by-Hop IOAM Indicator Label Allocation

   IOAM Indicator Label (value TBA3) and IOAM and Flow Indicator Label
   (value TBA4) are used to indicate the presence of the HbH IOAM data
   field in the MPLS header.  The HbH 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 TBA3 and TBA4 from the Extended
      Special-Purpose MPLS Values [I-D.mpls-spl-terminology].

   o  Labels allocated by a Controller from the network-wide global
      table.  The Controller provisions the labels on all nodes
      participating in IOAM functions along the data traffic path.

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 now include the Indicator Label.  

   When entropy label [RFC6790] is used for hashing function for ECMP,
   the procedure defined in this document does not alter the hashing
 

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   function.

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.

   The transit node that is not capable of supporting the IOAM functions
   defined in this document, can simply skip the IOAM processing of the
   MPLS header.

8.  IANA Considerations

   IANA maintains the "Special-Purpose Multiprotocol Label Switching
   (MPLS) Label Values" registry (see
   <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 [RFC8660],
   and the security considerations of IOAM in general are discussed in
   [I-D.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
 

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   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.

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

   [RFC8660]  Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", RFC 8660, December 2019.

   [I-D.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.

   [I-D.ippm-direct-export]  Song, H., et al., "In-situ OAM Direct
              Exporting", draft-ioamteam-ippm-ioam-direct-export, work
              in progress.

   [I-D.ippm-ioam-flags]  Mizrahi, T., et al.,  "In-situ OAM Flags",
              draft-ietf-ippm-ioam-flags, 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
 

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              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.

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

   [I-D.spring-mpls-path-segment]  Cheng, W., et al., "Path Segment in
              MPLS Based Segment Routing Network",
              draft-ietf-spring-mpls-path-segment, work in progress.

Contributors

Authors' Addresses

   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

 

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   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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