OAM for Service Programming with Segment Routing
draft-ali-spring-sr-service-programming-oam-01

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spring                                                            Z. Ali
Internet-Draft                                               C. Filsfils
Intended status: Standards Track                               N. Nainar
Expires: October 26, 2019                                   C. Pignataro
                                                                 F. Clad
                                                                F. Iqbal
                                                     Cisco Systems, Inc.
                                                                   X. Xu
                                                                 Alibaba
                                                          April 24, 2019

            OAM for Service Programming with Segment Routing
             draft-ali-spring-sr-service-programming-oam-01

Abstract

   This document defines the Operations, Administrations and Maintenance
   (OAM) for service programming in SR-enabled MPLS and IP networks.

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 October 26, 2019.

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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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements notation . . . . . . . . . . . . . . . . . . . .   2
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Document Scope  . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Programmable OAM  . . . . . . . . . . . . . . . . . . . . . .   3
     5.1.  Service Programming OAM Packet Marker . . . . . . . . . .   3
     5.2.  OAM with SR-aware services  . . . . . . . . . . . . . . .   3
     5.3.  OAM with SR-unaware services  . . . . . . . . . . . . . .   4
     5.4.  Controlling OAM packet processing in Services . . . . . .   4
   6.  OAM for Service Programming with SRv6 . . . . . . . . . . . .   4
     6.1.  OAM Tool Kit  . . . . . . . . . . . . . . . . . . . . . .   5
       6.1.1.  OAM Flag Processing . . . . . . . . . . . . . . . . .   5
       6.1.2.  OAM Segment ID  . . . . . . . . . . . . . . . . . . .   5
       6.1.3.  ICMP  . . . . . . . . . . . . . . . . . . . . . . . .   5
       6.1.4.  UDP Probes  . . . . . . . . . . . . . . . . . . . . .   6
       6.1.5.  In-band OAM . . . . . . . . . . . . . . . . . . . . .   6
   7.  OAM for Service Programming with SR-MPLS  . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   7
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [I-D.xuclad-spring-sr-service-programming] defines data plane
   functionality required to implement service segments and achieve
   service programming in SR-enabled MPLS and IP networks, as described
   in the Segment Routing architecture.  This document defines the
   Operations, Administrations and Maintenance (OAM) for service
   programming in SR-enabled MPLS and IP networks.

2.  Requirements notation

   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].

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3.  Terminology

   This document uses the terminologies defined in
   [I-D.ietf-spring-segment-routing],
   [I-D.filsfils-spring-srv6-network-programming]
   [I-D.xuclad-spring-sr-service-programming] and so the readers are
   expected to be familiar with the same.

4.  Document Scope

   The initial focus of this document to define and document the
   machinery required to apply OAM mechanisms on SRv6 based service
   programming.

   Future version of this document will include the required details to
   apply OAM mechanism on other data planes.

5.  Programmable OAM

   Section 4 of [I-D.xuclad-spring-sr-service-programming] introduces
   Service segments and the procedure of service programming when the
   services are SR-aware and SR-unaware.  By integrating the OAM
   functionality in the services, versatile OAM tool kits can be used to
   execute programmable OAM for service programming with Segment
   Routing.

   This section describes the procedure to perform basic OAM mechanisms
   such as path validation and path tracing of Service Programming
   environment in Segment Routing network.

5.1.  Service Programming OAM Packet Marker

   Any services upon receiving OAM packet may apply the service
   treatment if it cannot differentiate the OAM packet from normal data
   packet.  Depending on the service type, service treatment on OAM
   packet may result in dropping the OAM probe packet that may cause
   uncertainty in OAM mechanism.

   To avoid such uncertainty, any node that is originating the OAM probe
   for Service Programming OAM MUST mark the packet as OAM packet so
   that the services can differentiate the OAM packet from data traffic.

5.2.  OAM with SR-aware services

   As defined in section 4.1 of
   [I-D.xuclad-spring-sr-service-programming], an SR-aware service can
   process the SR information in the packet header such as performing
   lookup or executing the next segment etc.  An SR-aware service may

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   need to identify the packet payload and/or interpret SR information
   to apply the right policy to the received packet.  While processing
   SR information in the packet header, it can process the OAM packet
   marker in the SR header to differentiate the OAM packet from normal
   data packet.

   An SR-aware service SHOULD skip applying the service on the OAM
   packet while forwarding the packet to the next segment or IP address.
   As defined in section 9, a local policy may be used to control any
   malicious use of OAM marker.

5.3.  OAM with SR-unaware services

   As defined in section 4.2 of
   [I-D.xuclad-spring-sr-service-programming], an SR-unaware service may
   be a legacy service that is not able to process the SR information in
   the packet header.  SR Proxy, an entity that is external to the
   service is used to handle the SR information processing on behalf of
   the service.  SR Proxy will remove the SR header before forwarding
   the packet to SR-unaware services to avoid any erroneous decision due
   to the presence of SR header that the service cannot recognize.

   While processing SR information in the packet header, SR proxy can
   process the OAM packet marker in the SR header to differentiate the
   OAM packet from normal data packet.  SR Proxy MUST skip forwarding
   the packets with OAM marker to the service while forwarding the
   packet to the next segment or IP address.  As defined in section 9, a
   local policy may be used to control any malicious use of OAM marker.

5.4.  Controlling OAM packet processing in Services

   As mentioned in the above sections, SR-aware service or the SR proxy
   can use the OAM marker to differentiate the OAM packet from data
   packet to skip the service treatment.  Any intentional or
   unintentional use of OAM marker in data traffic may result in
   skipping service treatment for data traffic.  To avoid such
   condition, a local policy will be used in the SR-aware service or SR
   Proxy that SHOULD rate limit or MAY drop the packets received with
   OAM marker.

6.  OAM for Service Programming with SRv6

   [I-D.ietf-6man-segment-routing-header] defines SRH.Flags.O-bit in SRH
   header.  When service programming is implemented with SRv6 dataplane,
   SRH.Flags.O-bit is used as OAM marker.  An IPv6 packet received with
   a local END.OP or END.OTP SID is also considered as an OAM packet.

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   Any node that is originating OAM probe to a service in SRv6 dataplane
   MUST set SRH.Flags.O-bit in the SRH.

6.1.  OAM Tool Kit

   This section describes the availability of different tool kits that
   can be used to perform OAM functionality for Service Programming with
   SRv6 dataplane.

6.1.1.  OAM Flag Processing

   An SR-aware service or SR proxy MUST implement the SRH.Flags.O bit.
   An SR-aware service SHOULD skip applying the service to the packet
   when SRH.Flags.O-bit is set and SHOULD forward the packet based on
   the next header.  SR Service Proxy MUST skip applying the service to
   the packet when SRH.Flags.O-bit is set and SHOULD forward the packet
   based on the next header.

   An SR-aware service and SR proxy may choose to time-stamp and punt
   the packet with SRH.Flags.O-bit set for further processing and this
   is a local implementation matter.

6.1.2.  OAM Segment ID

   Section 3.2 of [[I-D.ali-spring-srv6-oam]] defines OAM segment ID and
   the associated forwarding semantics to implement the punt behavior
   for OAM packets.  Specifically, the draft defines END.OP and END.OTP
   SIDs.  An IPv6 packet received with DA set to a local END.OP or
   END.OTP SID is considered as an OAM packet.

   Any service policy head end MAY include OAM segment ID in the desired
   segment list position of SRH.  The inclusion of OAM SID in SRH can be
   used to control the services that are required to punt the OAM packet
   for processing.

6.1.3.  ICMP

   There is no hardware or software changes required to use ICMP for
   Ping operation.  It can be triggered from the service policy head end
   or from any classical IPv6 nodes by sending ICMPv6 Echo Request.  The
   existing ICMP Ping mechanism works seamlessly in SRv6 dataplane with
   no protocol changes required to the standard ICMPv6 [[RFC4443]],
   [[RFC4884]] or the standard ICMPv4 [[RFC0792]].

   An SR-aware service SHOULD skip the service and forward to next
   segment based on the SR information in the packet header.  An SR
   Service Proxy MUST skip the service and forward to next segment based
   on the SR information in the packet header.

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6.1.3.1.  Pinging Service SID Function

   When a remote node pings a service segment, it MUST set SRH.Flags.O =
   1.  If the target service segment is implemented with USP behavior,
   the ICMP packet can be constructed without adding END.OP or END.OTP
   SIDs defined in [I-D.ali-spring-srv6-oam].  However, if the target
   service SID observes a PSP behavior, the sender needs to insert
   END.OP/ END.OTP SIDs before the target service SID in the segment-
   list.  In either case, the target SR-aware service or SR proxy
   receives the ICMP echo request with either SRH.Flags.O-bit set or
   with the local END.OP or END.OTP SID.  In both cases, the packet is
   punted for slow-path processing and service is skipped.

   The Egress node process the packet as per procedure defined in
   [I-D.ali-spring-srv6-oam].  The Egress checks if the target SID is
   locally programmed or not.

   If the target SID is not locally programmed, the Egress responses
   with the ICMPv6 message (Type: "SRv6 OAM (TBA)", Code: "SID not
   locally implemented (TBA)"); otherwise a success is returned
   [I-D.ali-spring-srv6-oam].

6.1.4.  UDP Probes

   A classic traceroute mechanism relies on UDP probes by sending
   packets with sequentially incrementing the TTL.  More details are
   available in section 4.3.1 of [I-D.ali-spring-srv6-oam].

   An SR-aware service or SR proxy upon receiving the probe with TTL=1,
   may follow the traditional behavior of replying with ICMPv6 Time
   Exceeded Message (Type 3) as defined in [RFC4443] without applying
   the service.

   Use of SRH.Flags.O bit and END.OP/ END.OTP SIDs as OAM marker in the
   UDP probe for trace route is same as discussed for ICMPv6 ping
   discussed in the last section.

6.1.5.  In-band OAM

   To be Updated.

7.  OAM for Service Programming with SR-MPLS

   To be updated.

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8.  IANA Considerations

   None.

9.  Security Considerations

   A local policy may be used to control any malicious use of OAM
   marker.  More details are to be added in a future revision of the
   document.

10.  Acknowledgement

   Authors would like to thank Bruno Decraene for his review and useful
   comments.

11.  Normative References

   [I-D.ali-spring-srv6-oam]
              Ali, Z., Filsfils, C., Kumar, N., Pignataro, C.,
              faiqbal@cisco.com, f., Gandhi, R., Leddy, J., Matsushima,
              S., Raszuk, R., daniel.voyer@bell.ca, d., Dawra, G.,
              Peirens, B., Chen, M., and G. Naik, "Operations,
              Administration, and Maintenance (OAM) in Segment Routing
              Networks with IPv6 Data plane (SRv6)", draft-ali-spring-
              srv6-oam-02 (work in progress), October 2018.

   [I-D.filsfils-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J.,
              daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6
              Network Programming", draft-filsfils-spring-srv6-network-
              programming-07 (work in progress), February 2019.

   [I-D.ietf-6man-segment-routing-header]
              Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and
              d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
              (SRH)", draft-ietf-6man-segment-routing-header-18 (work in
              progress), April 2019.

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing
              Architecture", draft-ietf-spring-segment-routing-15 (work
              in progress), January 2018.

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   [I-D.xuclad-spring-sr-service-programming]
              Clad, F., Xu, X., Filsfils, C., daniel.bernier@bell.ca,
              d., Li, C., Decraene, B., Ma, S., Yadlapalli, C.,
              Henderickx, W., and S. Salsano, "Service Programming with
              Segment Routing", draft-xuclad-spring-sr-service-
              programming-02 (work in progress), April 2019.

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, DOI 10.17487/RFC0792, September 1981,
              <https://www.rfc-editor.org/info/rfc792>.

   [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>.

   [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,
              <https://www.rfc-editor.org/info/rfc4443>.

   [RFC4884]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
              "Extended ICMP to Support Multi-Part Messages", RFC 4884,
              DOI 10.17487/RFC4884, April 2007,
              <https://www.rfc-editor.org/info/rfc4884>.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <https://www.rfc-editor.org/info/rfc7665>.

Authors' Addresses

   Zafar Ali
   Cisco Systems, Inc.
   US

   Email: zali@cisco.com

   Clarence Filsfils
   Cisco Systems, Inc.
   Belgium

   Email: cfilsfils@cisco.com

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   Nagendra Kumar Nainar
   Cisco Systems, Inc.
   7200-12 Kit Creek Road
   Research Triangle Park, NC  27709
   US

   Email: naikumar@cisco.com

   Carlos Pignataro
   Cisco Systems, Inc.
   7200 Kit Creek Road
   Research Triangle Park, NC  27709-4987
   US

   Email: cpignata@cisco.com

   Francois Clad
   Cisco Systems, Inc.
   France

   Email: fclad@cisco.com

   Faisal Iqbal
   Cisco Systems, Inc.
   2000 Innovation Dr
   Ottawa, ON  3E8
   Canada

   Email: faiqbal@cisco.com

   Xiaohu Xu
   Alibaba

   Email: xiaohu.xxh@alibaba-inc.com

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