Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Informational R. Raszuk
Expires: September 3, 2015 Mirantis Inc.
U. Chunduri
Ericsson
L. Contreras
Telefonica I+D
March 2, 2015
Connecting MPLS-SPRING Islands over IP Networks
draft-xu-spring-islands-connection-over-ip-04
Abstract
MPLS-SPRING is an MPLS-based 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. To facilitate the incremental deployment of
this new technology, this document describes a mechanism which allows
the outermost LSP be replaced by an IP-based tunnel.
Status of This Memo
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This Internet-Draft will expire on September 3, 2015.
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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 . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
MPLS-SPRING [I-D.ietf-spring-segment-routing-mpls] is a MPLS-based
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. To
facilitate the incremental deployment of this new technology, this
document describes a mechanism which allows the outermost LSP to be
replaced by an IP-based tunnel (e.g., MPLS-in-IP/GRE tunnel
[RFC4023], MPLS-in-L2TPv3 tunnel [RFC4817] or MPLS-in-UDP tunnel
[I-D.ietf-mpls-in-udp] and etc) when the nexthop along the LSP is not
MPLS-SPRING-enabled. The tunnel destination address would be the
address of the egress of the outmost LSP (e.g., the egres of the
active segment).
This mechanism is much useful in the MPLS-SPRING-based Service
Function Chainning (SFC) case [I-D.xu-sfc-using-mpls-spring] where
only a few specific routers (e.g., Service Function Forwarders (SFF)
and classifiers) are required to be MPLS-SPRING-capable while the
other immediate routers are just required to support IP forwarding
capability. In addition, this mechanism is also useful in some
specific Traffic Engineering scenarios where only a few routers
(e.g., the entry and exit nodes of each plane in the dual-plane
network ) are specified as segments of explicit paths. In this way,
only a few routers are required to support the MPLS-SPRING capability
while all the other routers just need to support IP forwarding
capability, which would significantly reduce the deployment cost of
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this new technology. Furthermore, since there is no need to run any
other label distribution protocols (e.g., LDP), the network
provisioning is greatly simplified, which is one of the major claimed
benefits of the MPLS-SPRING technology.
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 [RFC3031],
[I-D.ietf-spring-segment-routing-mpls] and
[I-D.xu-sfc-using-mpls-spring] .
3. Packet Forwarding Procedures
Assume an MPLS-SPRING-enabled router X prepares to forward an MPLS
packet to the next segment (i.e., the node segment of MPLS-SPRING-
enabled router Y) which is identified by the top label of the MPLS
packet. If the next-hop router of the best path to Y is a non-MPLS
router, X couldn't map the packet's top label into an Next Hop Label
Forwarding Entry (NHLFE) , even though the top label itself is a
valid incoming label. If the label is not a Penultimate Hop Popping
(PHP) label (i.e., the NP-flag
[I-D.ietf-isis-segment-routing-extensions] associated with the
corresponding prefix SID of that top label is set), X SHOULD swap the
top label to the corresponding label significant to Y and then
encapsulate the MPLS packet into an IP-based tunnel. The tunnel
destination address is the IP address of Y (e.g., the /32 or /128
prefix FEC associated with that top label) and the tunnel source
address is the IP address of X. If the top label is a PHP label and
not at the bottom of the label stack, X SHOULD pop that top label
before performing the above 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 learnt from Y's advertisement of its
tunnel encapsulation capability. How to advertise the tunnel
encapsulation capability using IS-IS or OSPF are specified in
[I-D.xu-isis-encapsulation-cap] and [I-D.xu-ospf-encapsulation-cap]
respectively. In addition, how to advertise the tunnel encapsulation
capability using BGP are specified in [RFC5512] and
[I-D.xu-bess-encaps-udp].
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4. Acknowledgements
Thanks Joel Halpern, Bruno Decraene and Loa Andersson for their
insightful comments on this draft.
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.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
7.2. Informative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
Extensions for Segment Routing", draft-ietf-isis-segment-
routing-extensions-03 (work in progress), October 2014.
[I-D.ietf-mpls-in-udp]
Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", draft-ietf-mpls-in-udp-11
(work in progress), January 2015.
[I-D.xu-bess-encaps-udp]
Xu, X., Sheth, N., and R. Asati, "BGP Tunnel Encapsulation
Attribute for UDP", draft-xu-bess-encaps-udp-00 (work in
progress), February 2015.
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[I-D.xu-isis-encapsulation-cap]
Xu, X., Raszuk, R., Chunduri, U., and L. Contreras,
"Advertising Encapsulation Capability Using IS-IS", draft-
xu-isis-encapsulation-cap-03 (work in progress), February
2015.
[I-D.xu-ospf-encapsulation-cap]
Xu, X., Raszuk, R., Chunduri, U., and L. Contreras,
"Advertising Encapsulation Capability Using OSPF", draft-
xu-ospf-encapsulation-cap-00 (work in progress), February
2015.
[I-D.xu-sfc-using-mpls-spring]
Xu, X., Li, Z., Shah, H., and L. Contreras, "Service
Function Chaining Using MPLS-SPRING", draft-xu-sfc-using-
mpls-spring-01 (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.
[RFC5512] Mohapatra, P. and E. Rosen, "The BGP Encapsulation
Subsequent Address Family Identifier (SAFI) and the BGP
Tunnel Encapsulation Attribute", RFC 5512, April 2009.
Authors' Addresses
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
Robert Raszuk
Mirantis Inc.
Email: robert@raszuk.net
Uma Chunduri
Ericsson
Email: uma.chunduri@ericsson.com
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Luis M. Contreras
Telefonica I+D
Ronda de la Comunicacion, s/n
Sur-3 building, 3rd floor
Madrid, 28050
Spain
Email: luismiguel.contrerasmurillo@telefonica.com
URI: http://people.tid.es/LuisM.Contreras/
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