Internet DRAFT - draft-xu-mpls-spring-islands-connection-over-ip
draft-xu-mpls-spring-islands-connection-over-ip
Network Working Group X. Xu, Ed.
Internet-Draft Huawei
Intended status: Standards Track R. Raszuk
Expires: April 15, 2017 Bloomberg LP
U. Chunduri
L. Contreras
Telefonica I+D
L. Jalil
Verizon
October 12, 2016
Connecting MPLS-SPRING Islands over IP Networks
draft-xu-mpls-spring-islands-connection-over-ip-00
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 April 15, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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 . . . . . . . . . . . . . . . . . . . . . . . 6
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-UDP tunnel [RFC7510] or MPLS-in-L2TPv3 tunnel
[RFC4817] 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 egress of the active node
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
remaining 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,
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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
this new technology. Furthermore, since there is no need to run any
other label distribution protocol (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] and
[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 node 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. Acorrding to the following specification as
quoted from Section 3.22 of [RFC3031], the MPLS packet would be
discarded in the currenet MPLS implementations:
"When a labeled packet is traveling along an LSP, it may
occasionally happen that it reaches an LSR at which the ILM does
not map the packet's incoming label into an NHLFE, even though the
incoming label is itself valid...Unless it can be determined
(through some means outside the scope of this document) that
neither of these situations obtains, the only safe procedure is to
discard the packet. "
This document proposes an improved procedure to deal with the above
case. The basic idea is to set an IP tunnel towards the egress of
topmost LSP as the NHLFE of that incoming label. More specifically,
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 label to the corresponding label significant to Y and then
encapsulate the MPLS packet into the IP-based tunnel towards Y. The
tunnel destination address is the IP address of Y (e.g., the /32 or
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/128 prefix FEC associated with that top label) and the tunnel source
address is the IP address of X. If the label is a PHP label and not
at the bottom of the label stack, X SHOULD pop that label before
performing the above MPLS over IP encapsulation. The IP encapsulated
MPLS packet would be forwarded according to the IP routing table.
Upon receipt of that IP encapsulated MPLS 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 be 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.ietf-ospf-encapsulation-cap]
respectively.
4. Acknowledgements
Thanks Joel Halpern, Bruno Decraene and Loa Andersson for their
insightful comments on this draft.
5. IANA Considerations
No IANA action is required.
6. Security Considerations
TBD.
7. References
7.1. 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,
<http://www.rfc-editor.org/info/rfc2119>.
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-07 (work in progress), June 2016.
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[I-D.ietf-ospf-encapsulation-cap]
Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras,
L., and L. Jalil, "Advertising Tunnelling Capability in
OSPF", draft-ietf-ospf-encapsulation-cap-00 (work in
progress), October 2015.
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Shakir, R.,
jefftant@gmail.com, j., and E. Crabbe, "Segment Routing
with MPLS data plane", draft-ietf-spring-segment-routing-
mpls-05 (work in progress), July 2016.
[I-D.xu-isis-encapsulation-cap]
Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras,
L., and L. Jalil, "Advertising Tunnelling Capability in
IS-IS", draft-xu-isis-encapsulation-cap-06 (work in
progress), November 2015.
[I-D.xu-sfc-using-mpls-spring]
Xu, X., Shah, H., Contreras, L., and d.
daniel.bernier@bell.ca, "Service Function Chaining Using
MPLS-SPRING", draft-xu-sfc-using-mpls-spring-06 (work in
progress), July 2016.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<http://www.rfc-editor.org/info/rfc3031>.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed.,
"Encapsulating MPLS in IP or Generic Routing Encapsulation
(GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005,
<http://www.rfc-editor.org/info/rfc4023>.
[RFC4817] Townsley, M., Pignataro, C., Wainner, S., Seely, T., and
J. Young, "Encapsulation of MPLS over Layer 2 Tunneling
Protocol Version 3", RFC 4817, DOI 10.17487/RFC4817, March
2007, <http://www.rfc-editor.org/info/rfc4817>.
[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", RFC 7510,
DOI 10.17487/RFC7510, April 2015,
<http://www.rfc-editor.org/info/rfc7510>.
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Authors' Addresses
Xiaohu Xu (editor)
Huawei
Email: xuxiaohu@huawei.com
Robert Raszuk
Bloomberg LP
Email: robert@raszuk.net
Uma Chunduri
Email: uma.chunduri@gmail.com
Luis M. Contreras
Telefonica I+D
Email: luismiguel.contrerasmurillo@telefonica.com
Luay Jalil
Verizon
Email: luay.jalil@verizon.com
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