Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track R. Raszuk
Expires: June 6, 2015 Mirantis Inc.
U. Chunduri
Ericsson
December 3, 2014
Connecting MPLS-SPRING Islands over IP Networks
draft-xu-spring-islands-connection-over-ip-03
Abstract
MPLS-SPRING is a source routing paradigm in which a sender of a
packet is allowed to partially or completely specify the route the
packet takes through the network by imposing stacked MPLS labels to
the packet. The current MPLS-SRPING architecture requires an end-to-
end MPLS Label Switched Path (LSP) between any two MPLS-SPRING-
enabled routers (e.g., two adjacent hops of a given explicit path).
In order to enable MPLS-SPRING-enabled routers to be deployed even
when there are non-MPLS routers along the path between two MPLS-
SPRING-enabled routers, it is desirable to have an alternative, which
allows the use of IP-based tunnels (e.g., GRE tunnels) to connect two
MPLS-SPRING-enabled routers. This document describes a mechanism for
such usage.
Status of This Memo
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This Internet-Draft will expire on June 6, 2015.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Packet Forwarding Procedures . . . . . . . . . . . . . . . . 3
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
MPLS-SPRING [I-D.ietf-spring-segment-routing-mpls] is a source
routing paradigm in which a sender of a packet is allowed to
partially or completely specify the route the packet takes through
the network by imposing stacked MPLS labels to the packet. The
current MPLS-SRPING architecture requires an end-to-end MPLS Label
Switched Path (LSP) between any two MPLS-SPRING-enabled routers
(e.g., two adjacent hops of a given explicit path). In order to
enable MPLS-SPRING-enabled routers to be deployed even when there are
non-MPLS routers along the path between two MPLS-SPRING-enabled
routers, it is desirable to have an alternative, which allows the use
of IP-based tunnels (e.g., MPLS-in-IP/GRE tunnel [RFC4023], MPLS-in-
L2TPv3 tunnel [RFC4817] or MPLS-in-UDP tunnel [I-D.ietf-mpls-in-udp])
to connect two MPLS-SPRING-enabled routers which are specified as
adjacent hops of a given explicit path. The tunnel destination
address would be the address of next-hop MPLS-SPRING-enabled router
along the explicit path, and this would cause the packet to be
delivered to the next explicit hop. In this procedure, the ingress
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and egress of the IP-based tunnel MUST support MPLS-SPRING features
including the MPLS forwarding capability, whereas those transit
routers along the path between them don't need to support any MPLS-
SPRING features including the MPLS forwarding capability. The above
mechanism is much useful for incrementally deployment of the MPLS-
SPRING technology, especially in the MPLS-SPRING-based Service
Function Chainning (SFC) case where only a few specific routers
(e.g., service nodes and classifiers) are actually required to be
MPLS-SPRING-capable.
1.1. Requirements 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 RFC 2119 [RFC2119].
2. Terminology
This memo makes use of the terms defined in
[I-D.ietf-spring-segment-routing-mpls].
3. Packet Forwarding Procedures
Assume an MPLS-SPRING-enabled router X prepares to forward an MPLS
packet to the next explicit hop Y which is identified by the top
label of the MPLS packet, if the next-hop router Z which is
physically adjacent to X is a non-MPLS-SPRING router, X would
encapsulate the MPLS packet into an IP-based tunnel (e.g., GRE tunnel
or UDP tunnel) where the tunnel destination is an IP address of Y
(i.e., the /32 or /128 IGP prefix FEC corresponding to that top
label) and the tunnel source is an IP address of X. If the top label
is a Penultimate Hop Popping (PHP) label, X SHOULD pop that top label
before performing the encapsulation. The IP encapsulated packet
would be forwarded according to the IP forwarding table. Upon
receipt of that IP encapsulated packet, Y would decapsulate it and
then process the decapsulated MPLS packet accordingly.
As for which tunnel encapsulation type should be used by X, it can be
manually specified on X or dynamically learnt from Y's advertisement
of its tunnel encapsulation capability. How to advertise the tunnel
encapsulation capability is outside of the scope of this document.
4. Acknowledgements
Thanks Joel Halpern for his insightful comments on this draft.
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5. IANA Considerations
No action is required for IANA.
6. Security Considerations
TBD.
7. References
7.1. Normative References
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J.,
and E. Crabbe, "Segment Routing with MPLS data plane",
draft-ietf-spring-segment-routing-mpls-00 (work in
progress), December 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[I-D.ietf-mpls-in-udp]
Xu, X., Sheth, N., Yong, L., Pignataro, C., Yongbing, F.,
Callon, R., and D. Black, "Encapsulating MPLS in UDP",
draft-ietf-mpls-in-udp-07 (work in progress), October
2014.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating
MPLS in IP or Generic Routing Encapsulation (GRE)", RFC
4023, March 2005.
[RFC4817] Townsley, M., Pignataro, C., Wainner, S., Seely, T., and
J. Young, "Encapsulation of MPLS over Layer 2 Tunneling
Protocol Version 3", RFC 4817, March 2007.
Authors' Addresses
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
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Robert Raszuk
Mirantis Inc.
Email: robert@raszuk.net
Uma Chunduri
Ericsson
Email: uma.chunduri@ericsson.com
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