SPRING Working Group S. Hegde
Internet-Draft K. Vairavakkalai
Intended status: Standards Track R. Bonica
Expires: July 12, 2021 Juniper Networks
January 8, 2021
The SRv6 END.DTM Segment Type
draft-bonica-spring-srv6-end-dtm-00
Abstract
This document describes a new SRv6 segment type, called END.DTM. The
END.DTM segment type supports inter-working between SRv6 and SR-MPLS.
Like any segment type, END.DTM contains a function and arguments.
The function causes the processing SRv6 node to remove an SRv6 header
and impose an SR-MPLS label stack. The arguments determine MPLS-
label stack contents.
Status of This Memo
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This Internet-Draft will expire on July 12, 2021.
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Use-case . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Processing . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
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
[I-D.ietf-spring-srv6-network-programming]. When SR is implemented
over MPLS, it is called SR-MPLS [RFC8660].
This document describes a new SRv6 segment type, called END.DTM. The
END.DTM segment type supports inter-working between SRv6 and SR-MPLS.
Like any segment type, END.DTM contains a function and arguments.
The function causes the processing SRv6 node to:
o Remove an SRv6 header (i.e., an IPv6 header and its extensions).
o Impose an SR-MPLS label stack.
The arguments determine MPLS-label stack contents and Transport Class
of the MPLS Tunnel.
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. Use-case
------ ------ ------ ------ ------
|Node 1| --- |Node 2| --- |Node 3| --- |Node 4| --- |Node 5|
------ ------ ------ ------ ------
Seg. A Seg. B Seg. C Seg. D
<-----------SRv6 Part ----------><-------SR-MPLS Part------>
Figure 1: END.DTM Use-case
Figure 1 depicts an inter-working SR path. The SR path originates on
Node 1 and terminates on Node 5. It contains:
o An SRv6 part
o An SR-MPLS part
The SRv6 part includes Nodes 1, 2 and 3. These nodes MUST be
SRv6-capable but are NOT REQUIRED to be SR-MPLS capable. An END.DTM
segment is instantiated on Node 3. Therefore, Node 3 MUST be able to
push an SR-MPLS label stack. However, it is NOT REQUIRED to process
incoming MPLS labels.
The SRv6 part also includes:
o Segment A - An END segment that is instantiated on Node 2.
o Segment B - An END.DTM segment that is instantiated on Node 3.
The SR-MPLS part includes Nodes 4 and 5. These nodes MUST be SR-
MPLS-capable but are NOT REQUIRED to be SRv6 capable.
The SR-MPLS part also includes:
o Segment C - A prefix segment that is instantiated on Node 4.
o Segment D - A prefix segment that is instantiated on Node 5.
The following paragraphs describe how a packet traverses this inter-
working SR path:
Node 1 encapsulates the packet in an SRv6 header. The SRv6 header
contains the following Segment Identifiers (SID):
o A SID representing Segment A, encoded in the Destination Address
field of the IPv6 header.
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o A SID representing Segment B, encoded in a Segment Routing Header
(SRH) [RFC8754].
Node 1 sends the packet to Node 2. When the packet arrives at Node
2, The Destination Address field in the IPv6 header represents a
locally instantiated END SID. Node 2 processes the packet as
follows:
o Decrement the Segments Left field in the SRH
o Copy the next SID from the SRH to the Destination Address field of
the IPv6 header.
o Forward the packet to Node 3.
When the packet arrives at Node 3, The Destination Address field in
the IPv6 header represents a locally instantiated END.DTM SID. Node
3 processes the packet as follows:
o Remove the IPv6 header and its extension headers (including the
SRH).
o Push two SR-MPLS labels, representing Segments D and C.
o Forward the packet to Node 4.
When the packet arrives at Node 4, it is encapsulated in an SR-MPLS
label stack. Node 4 processes the packet as described in SR-MPLS
[RFC8660].
4. Processing
The End.DTM SID MUST be the last segment in a SR Policy. A SID
instance is associated with:
o An SR-MPLS label stack.
o An outbound interface.
When Node N receives a packet destined to S and S is a locally
instantiated End.DTM SID, Node N executes the following procedure:
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S01. When an IPv6 Routing Header 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. Proceed to process the next header in the packet
S06. }
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an End.DTM SID, N executes the following procedure:
S01. Remove the outer IPv6 Header with all its extension headers
S02. Push the SR-MPLS label stack that is associated with the END.DTM instance
S03. Send the packet on the out interface associated with the END.DTM instance
5. IANA Considerations
IANA is requested to add the following entry to the "SRv6 Endpoint
Behaviors" sub-registry of the "Segment Routing Parameters" registry:
+-------+-----+-------------------+-----------+
| Value | Hex | Endpoint behavior | Reference |
+-------+-----+-------------------+-----------+
| TBD | TBD | END.DTM | [This.ID] |
+-------+-----+-------------------+-----------+
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
[I-D.ietf-spring-srv6-network-programming].
7. Acknowledgements
TBD
8. References
8.1. Normative References
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[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.
[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>.
[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>.
[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>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
[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>.
8.2. Informative References
[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
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Shraddha Hegde
Juniper Networks
Embassy Business Park
Bangalore, KA 560093
India
Email: shraddha@juniper.net
Kaliraj Vairavakkalai
Juniper Networks
1133 Innovation Way,
Sunnyvale, California 94089
USA
Email: kaliraj@juniper.net
Ron Bonica
Juniper Networks
Herndon, Virginia 20171
USA
Email: rbonica@juniper.net
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