Internet DRAFT - draft-ali-spring-sr-service-programming-oam
draft-ali-spring-sr-service-programming-oam
spring Z. Ali
Internet-Draft C. Filsfils
Intended status: Standards Track N. Nainar
Expires: May 15, 2023 C. Pignataro
F. Clad
Cisco Systems, Inc.
F. Iqbal
Arista Networks
X. Xu
Capitalonline
November 16, 2022
OAM for Service Programming with Segment Routing
draft-ali-spring-sr-service-programming-oam-05
Abstract
This document defines the Operations, Administrations and Maintenance
(OAM) for service programming in SR-enabled MPLS and IP networks.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 2
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Document Scope . . . . . . . . . . . . . . . . . . . . . . . 3
5. OAM for Service Programming . . . . . . . . . . . . . . . . 3
5.1. Service Programming OAM Packet Processing . . . . . . . . 3
5.2. Service Programming OAM in SRv6 Data Plane . . . . . . . 3
5.2.1. OAM with SR-aware services . . . . . . . . . . . . . 4
5.2.2. OAM with SR-unaware services . . . . . . . . . . . . 4
5.3. Service Programming OAM in SR-MPLS Data Plane . . . . . . 5
5.4. Controlling OAM packet processing in Services . . . . . . 5
6. Illustration . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. SRv6 Dataplane . . . . . . . . . . . . . . . . . . . . . 5
6.1.1. Pinging SR Service Policy . . . . . . . . . . . . . . 6
6.1.2. Pinging a Service SID . . . . . . . . . . . . . . . . 7
6.1.3. Tracing a SR Service Policy . . . . . . . . . . . . . 7
6.2. SR-MPLS Dataplane . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8
10. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
[I-D.ietf-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 [RFC8402],
[I-D.ietf-spring-srv6-network-programming]
[I-D.ietf-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. OAM for Service Programming
Section 4 of [I-D.ietf-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 ping and path tracing to Service Programming
environment in Segment Routing network.
5.1. Service Programming OAM Packet Processing
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.
The pseudo code for the service function SIDs in
[I-D.ietf-spring-sr-service-programming] has been defined to avoid
such uncertainty, as explained in the following subsections.
5.2. Service Programming OAM in SRv6 Data Plane
When the service programming is applied in an SRv6 network, the
Upper-layer header type is typically set to ICMPv6 or UDP to differentiate the
OAM packet from the data packets.
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5.2.1. OAM with SR-aware services
As defined in section 4.1 of
[I-D.ietf-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, processing the upper layer
header, etc.
An SR-aware service SHOULD skip applying the service on the OAM.
As defined in section 9, a local policy may be used to control any
malicious use of OAM marker.
An SR-aware service follows the procedure defined in the
[I-D.draft-ietf-6man-spring-srv6-oam] to implement ping and trace-route
to a SR-aware SID and additional OAM mechanisms including the support
for the OAM flag (O-flag).
5.2.2. OAM with SR-unaware services
As defined in section 4.2 of
[I-D.ietf-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.
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The SRv6 pseudocode for SR Proxy defined in Sections 6.1.2.1, 6.1.2.2
and 6.1.2.3 of [I-D.ietf-spring-sr-service-programming] handles the
OAM packets as explained in the following.
- Case 1: The service service programming segment is a transit segment.
In this case, if the Upper-layer header does not match Ethernet,
IPv4 or IPv6, the service function is skipped and packet is
resubmitted to the IPv6 module for transmission to the new destination
in the header (towards the next SRv6 segment).
Please refer to the following lines of SRv6 pseudocode for SR Proxy
defined in Sections 6.1.2.1, 6.1.2.2
and 6.1.2.3 of [I-D.ietf-spring-sr-service-programming], respectively.
In case of Static Proxy for Inner Type Ethernet:
S15. If (Upper-layer header type != 143 (Ethernet)) {
S16. Resubmit the packet to the IPv6 module for transmission to
the new destination.
S17. }
In case of Static Proxy for Inner Type IPv4:
S15. If (Upper-layer header type != 4 (IPv4)) {
S16. Resubmit the packet to the IPv6 module for transmission to
the new destination.
S17. }
In case of Static Proxy for Inner Type IPv6:
S15. If (Upper-layer header type != 41 (IPv6)) {
S16. Resubmit the packet to the IPv6 module for transmission to
the new destination.
S17. }
- Case 2: The service service programming segment is the ultimate segment.
This is the case of OAM operations are targetted to a service programming
SID (e.g., Ping and Trace-route to a service programming SID).
In this case, as part of the Upper-layer header
processing, the SR proxy processes to OAM payload, skips applying the
service on the OAM packet and responds to the OAM message, accordingly.
Please refer to the following lines of SRv6 pseudocode for SR Proxy
defined in Sections 6.1.2.1, 6.1.2.2
and 6.1.2.3 of [I-D.ietf-spring-sr-service-programming], respectively.
In case of Static Proxy for Inner Type Ethernet:
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 static proxy SID for Ethernet
traffic, the following pseudocode is executed.
S01. If (Upper-layer header type != 143 (Ethernet)) {
S02. Process as per [I-D.ietf-spring-srv6-network-programming]
Section 4.1.1
S03. }
In case of Static Proxy for Inner Type IPv4:
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 static proxy SID for IPv4
traffic, the following pseudocode is executed.
S01. If (Upper-layer header type != 4 (IPv4)) {
S02. Process as per [I-D.ietf-spring-srv6-network-programming]
Section 4.1.1
S03. }
In case of Static Proxy for Inner Type IPv6:
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 static proxy SID for IPv6
traffic, the following pseudocode is executed.
S01. If (Upper-layer header type != 41 (IPv6)) {
S02. Process as per [I-D.ietf-spring-srv6-network-programming]
Section 4.1.1
S03. }
5.3. Service Programming OAM in SR-MPLS Data Plane
This section will be updated later.
5.4. Controlling OAM packet processing in Services
As mentioned in the above sections, SR-aware service or the SR proxy
can use the Upper-layer header to differentiate the OAM packet from
data packet to skip the service treatment. To avoid any intentional
or unintentional use of OAM, a local policy SHOULD be used in the SR-
aware service or SR Proxy to rate limit the incoming OAM packets.
6. Illustration
This section illustrates how the existing OAM tools can be used to
perform the connectivity check or path tracing of SR Service
Policies.
6.1. SRv6 Dataplane
This section illustrates how ICMPv6 can be used to ping or trace SR
service policies in an SRv6 network using the below example topology.
+-----------------------------------------------------+
| |
| +---------+ |
| | S2 | |
| |(service)| |
| +---------+ |
| | | |
+----+----+ ---> +---------+ ---> +---------+ +----+-----+
| H +--------+ S1 +--------+ SR +----+| E |
|(headend)| |(service)| | Proxy | |(endpoint)|
+----+----+ +---------+ +---------+ +----+-----+
| |
| SRv6 Network |
+-----------------------------------------------------+
Figure 2. SR Service Policies in SRv6 Network
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6.1.1. Pinging SR Service Policy
The user interested to ping the SR service policy shown in Figure 2
will trigger the ICMPv6 echo request from the headend H with
IP6(H,S1)(SRH) and the upper layer header set to ICMPv6. The probe
will be processed along the path as below:
+-----------------------------------------------------+
| |
| +---------+ |
| | S2 | |
| |(service)| |
| +---------+ |
| | | |
+----+----+ ---> +---------+ ---> +---------+ +----+-----+
| H +--------+ S1 +--------+ SR +----+| E |
|(headend)| |(service)| | Proxy | |(endpoint)|
+----+----+ +---------+ +---------+ +----+-----+
| |
+---------+ +---------+ +---------+ |
| |IP6(H,S1)| |IP6(H, S)| |IP6(H,E.)| |
| +---------+ +---------+ +---------+ |
| |SRH(E,..,| |SRH(E,..,| |SRH(E,..,| |
| | S2,..;| | S2,..;| | S2,..;| |
| | S1,..;| | S1,..;| | S1,..;| |
| | SL=i)| | SL=j)| | SL=k)| |
| +---------+ +---------+ +---------+ |
| | ICMPv6 | | ICMPv6 | | ICMPv6 | |
| +---------+ +---------+ +---------+ |
| SRv6 Network |
+-----------------------------------------------------+
Figure 3. Ping to SR Service Policies in SRv6 Network
S1 (SR-aware service) will apply END function and follow the steps
defined in [I-D.draft-ietf-6man-spring-srv6-oam].
The Upper-layer header matches ICMPv6 but
the Segment Left is not 0 and so the packet will be forwarded to
the next destination S2. Service function is skipped due to ICMPv6
payload.
SR Proxy upon receiving the packet will match the local proxy SID
and follow the steps defined in Sections 6.1.2.1, 6.1.2.2
and 6.1.2.3 of [I-D.ietf-spring-sr-service-programming].
The Upper-layer header
does not match Ethernet, IPv4 or IPv6 and so resubmit the packet
to the IPv6 module for transmission to the next destination E
and service function is skipped.
The endpoint E will process the upper-layer header and reply back
to the initiator node H.
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6.1.2. Pinging a Service SID
The user interested to ping a specific service SID SR service policy
shown in Figure 4 will trigger the ICMPv6 echo request from the
headend H with IP6(H,S1) and the upper layer header set to
ICMPv6. The probe will be processed along the path as below:
+-----------------------------------------------------+
| |
| +---------+ |
| | S2 | |
| |(service)| |
| +---------+ |
| | | |
+----+----+ ---> +---------+ ---> +---------+ +----+-----+
| H +--------+ S1 +--------+ SR +----+| E |
|(headend)| |(service)| | Proxy | |(endpoint)|
+----+----+ +---------+ +---------+ +----+-----+
| |
+---------+ |
| |IP6(H,S1)| |
| +---------+ |
| | ICMPv6 | |
| +---------+ |
| SRv6 Network |
+-----------------------------------------------------+
Figure 4. Ping to specific Service SID in SRv6 Network
S1 (SR-aware service) will follow the steps
defined in [I-D.draft-ietf-6man-spring-srv6-oam]. Specifically,
the service processes the ICMPv6 message and respond to the source,
accordingly.
S2 (SR-Unaware Service): The SR Proxy upon receiving the packet will
match the local proxy SID
and follow the steps defined in Sections 6.1.2.1, 6.1.2.2
and 6.1.2.3 of [I-D.ietf-spring-sr-service-programming].
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated SID, the proxy process the ICMPv6 payload
and respond to it, accordingly.
6.1.3. Tracing a SR Service Policy
The user interested to trace the SR service policy shown in Figure 2
will trigger the ICMPv6 echo request from the headend H with
IPv6(H,S1)(SRH), set the upper layer header set to ICMPv6 and the TTL
to 1 and increment the same in the subsequent packets. The probe
will be processed along the path as below:
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The first probe sent from H will reach S1 (SR-aware service) with
Hop Limit of 1. S1 will process TTL expiry as described in
[I-D.draft-ietf-6man-spring-srv6-oam] and sends
an ICMP Time Exceeded message to H with Code 0.
The second probe sent from H will reach S2 (SR Proxy) with Hop
Limit of 1. SR Proxy will process as defined in the step S05 in
Sections 6.1.2.1, 6.1.2.2
and 6.1.2.3 of [I-D.ietf-spring-sr-service-programming] and sends
an ICMP Time Exceeded message to H with Code 0.
The third probe sent from H will reach E with Hop Limit of 1. E
processes TTL expiry as described in
[I-D.draft-ietf-6man-spring-srv6-oam] and send an ICMP Time
Exceeded message to H with Code 0.
6.2. SR-MPLS Dataplane
To be Updated.
7. IANA Considerations
None.
8. 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.
9. Acknowledgement
Authors would like to thank Bruno Decraene for review and useful
comments.
10. Normative References
[I-D.ietf-6man-segment-routing-header]
Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-26 (work in
progress), October 2019.
[I-D.ietf-6man-spring-srv6-oam]
Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M.
Chen, "Operations, Administration, and Maintenance (OAM)
in Segment Routing Networks with IPv6 Data plane (SRv6)",
draft-ietf-6man-spring-srv6-oam-08 (work in progress),
October 2020.
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[I-D.ietf-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-ietf-spring-sr-service-
programming-03 (work in progress), September 2020.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-28 (work in
progress), December 2020.
[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>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
Authors' Addresses
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Zafar Ali
Cisco Systems, Inc.
US
Email: zali@cisco.com
Clarence Filsfils
Cisco Systems, Inc.
Belgium
Email: cfilsfils@cisco.com
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
Arista Networks
Email: faisal.ietf@gmail.com
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Xiaohu Xu
Alibaba
Email: xiaohu.xu@capitalonline.net
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