SPRING Working Group K. Salih
Internet-Draft S. Hegde
Intended status: Standards Track M. Rajesh
Expires: January 11, 2022 R. Bonica
Juniper Networks
July 10, 2021
SRv6 inter-domain mapping SIDs
draft-salih-spring-srv6-inter-domain-sids-00
Abstract
This document describes three new SRv6 end point behaviors, named
END.REPLACE, END.REPLACEB6 and END.DB6. These SIDs are used in
distributed inter-domain solutions for connecting SRv6 domains. This
behavior is normally executed on border routers between different
domains. These SIDs can also be used to provide multiple intent
based paths across these domains.
Status of This Memo
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Usecases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. usecase 1 . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. usecase 2 . . . . . . . . . . . . . . . . . . . . . . . . 3
4. SRv6 SID behaviors . . . . . . . . . . . . . . . . . . . . . 4
4.1. END.REPLACE . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. END.REPLACEB6 . . . . . . . . . . . . . . . . . . . . . . 5
4.3. END.DB6 . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Overview
Segment Routing (SR) [RFC8402] allows source nodes to steer packets
through SR paths. It can be implemented over IPv6 [RFC8200] or MPLS
[RFC3031]. When SR is implemented over IPv6, it is called SRv6
[RFC8986].
This document describes three new SRv6 endpoint behaviors, named
END.REPLACE, END.REPLACEB6 and END.DB6. These SIDs help in building
paths over different SRv6 domans in a distributed manner. These
extensions will aid in end to end SRv6 intent based path stitching as
well.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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3. Usecases
The document [I-D.hegde-spring-mpls-seamless-sr] describes different
models of topology applicable for the use-cases mentioned in this
document.
3.1. usecase 1
This requirement is mentioned in the document
[I-D.hegde-spring-mpls-seamless-sr] under the section 4.1.1.
---IBGP------EBGP----IBGP------EBGP-----IBGP---
| | | | | |
+-----------+ +-----------+ +-----------+
| | | | | |
| ASBR1+--+ASBR2 ASBR3+--+ASBR4 |
PE1+ AS1 | X | AS2 | X | AS3 +PE2
| ASBR5+--+ASBR6 ASBR7+--+ASBR8 |
| | | | | |
+-----+-----+ +-----------+ +-----------+
PE3
|---SRv6---| |---SRv6---| |---SRv6---|
Figure 1: Multiple ASes connected with E-BGP
The above diagram Figure 1 has three different ASes (AS1, AS2 and
AS3). All the three domains are having SRv6. BGP is used for
getting option C [RFC4364] style connectivity end to end from PE1 to
PE2.
3.2. usecase 2
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+-----------+ +------------+
/ \ / \
| ABR1 |
| | |
PE1+ AS1 + AS2 +PE2
| | |
| ABR2 |
\ /\ /
+------------+ +-----------+
Figure 2: Single AS with Multiple IGP domains
The above diagram Figure 2 shows two different SRv6 domains, AS1 and
AS2. Services are running between PE1 and PE2 in option B [RFC4364]
style. The requirement here is to avoid service route lookup on ABR1
and ABR2 to provide option B style end to end connectivity.
4. SRv6 SID behaviors
Here we will describe the new SRv6 SID behaviors
4.1. END.REPLACE
For the use-case mentioned under Section 3.1 END.REPLACE SID is
applicable
The End.REPLACE SID cannot be the last segment in SRH or SR Policy.
Any SID instance of this behavior is associated with a set, J, of one
or more L3 adjacencies of immediate BGP neighbors
When Node N receives a packet destined to S and S is a locally
instantiated End.REPLACE SID, Node N executes the following
procedure:
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S01. When an SRH is processed {
S02. If (Segments Left == 0) {
S03. Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet.
S04. }
S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address with Code 0
(Hop limit exceeded in transit), interrupt packet processing, and discard packet
S07. }
S08. Decrement IPv6 Hop Limit by 1
S09. Update IPv6 DA with new destination address(SID) mapped with END.REPLACE SID.
S10. Submit the packet to the IPv6 module for transmission
to the new destination via a member of J.
S11. }
4.2. END.REPLACEB6
For the use-case mentioned under Section 3.1 END.REPLACEB6 SID is
applicable
The End.REPLACEB6 SID cannot be the last segment in a SRH or SR
Policy.
Node N is configured with an IPv6 address T (e.g., assigned to its
loopback).
When Node N receives a packet destined to S and S is a locally
instantiated End.REPLACEB6 SID, Node N executes the following
procedure:
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S01. When an SRH is processed {
S02. If (Segments Left == 0) {
S03. Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet.
S04. }
S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address with Code 0
(Hop limit exceeded in transit), interrupt packet processing, and discard packet
S07. }
S08. Decrement IPv6 Hop Limit by 1
S09. Update IPv6 DA with new destination address(SID) mapped with END.REPLACEB6.
S10. Push an IPv6 header with an SRH.
S11. Set outer IPv6 SA = T and outer IPv6 DA to the first SID in the segment list
S12. Set outer Payload Length, Traffic Class, Hop Limit, and Flow Label fields
S13. Set the outer Next Header value
S14. Submit the packet to the IPv6 module for transmission to the First SID.
S15. }
4.3. END.DB6
For the use-case mentioned under Section 3.2 END.DB6 SID is
applicable.
The End.DB6 SID MUST be the last segment in SRH or SR Policy.
Node N is configured with an IPv6 address T (e.g., assigned to its
loopback).
When Node N receives a packet destined to S and S is a locally
instantiated End.DB6 SID, Node N executes the following procedure:
S01. When an SRH is processed {
S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S04. }
S05. Remove the outer IPv6 header with all its extension headers.
S06. Push the new IPv6 header with the SRv6 SIDs associated with the
END.DB6 sid in an SRH.
S07. Set outer IPv6 SA = T and outer IPv6 DA to the first SID in the segment list.
S08. Set outer Payload Length, Traffic Class, Hop Limit, and Flow Label fields
S09. Set the outer Next Header value
S10. Submit the packet to the IPv6 module for transmission to First SID.
S11. }
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5. IANA Considerations
This document requires no IANA action.
The authors will request an early allocation from the "SRv6 Endpoint
Behaviors" sub-registry of the "Segment Routing Parameters" registry.
6. Security Considerations
Because SR inter-working requires co-operation between inter-working
domains, this document introduces no security consideration beyond
those addressed in [RFC8402], [RFC8754] and [RFC8986].
7. Contributors
Swamy SRK
Juniper Networks
Email: swamys@juniper.net
G. Sri Karthik Goud
Juniper Networks
Email: gkarthik@juniper.net
8. Acknowledgements
Thanks to Ram Santhanakrishnan, Srihari Sangli, Rajendra Prasad
Bollam and Kiran Kushalad for their valuable comments.
9. References
9.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[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>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
9.2. Informative References
[I-D.hegde-spring-mpls-seamless-sr]
Hegde, S., Bowers, C., Xu, X., Gulko, A., Bogdanov, A.,
Uttaro, J., Jalil, L., Khaddam, M., Alston, A., and L. M.
Contreras, "Seamless SR Problem Statement", draft-hegde-
spring-mpls-seamless-sr-05 (work in progress), February
2021.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
Authors' Addresses
Salih K A
Juniper Networks
Embassy Business Park
Bangalore, KA 560093
India
Email: salih@juniper.net
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Shraddha Hegde
Juniper Networks
Embassy Business Park
Bangalore, KA 560093
India
Email: shraddha@juniper.net
Rajesh
Juniper Networks
Embassy Business Park
Bangalore, KA 560093
India
Email: mrajesh@juniper.net
Ron Bonica
Juniper Networks
Herndon, Virginia 20171
USA
Email: rbonica@juniper.net
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