MPLS Working Group R. Raszuk
Internet-Draft NTT I3
Intended status: Standards Track January 2, 2014
Expires: July 6, 2014
MPLS Domain Wide Labels
draft-raszuk-mpls-domain-wide-labels-01
Abstract
This document describes a mechanism of using concept of Domain Wide
MPLS Labels in parallel with any of the existing deployments using
other label distribution and allocation methods where multi protocol
label switching paradigm is used for transport. Specifically it
defines a new type of context label which can be used to
differentiate lookup tables when using Domain Wide transport Labels
from other downstream or upstream assigned transport labels. The end
result is creation of clean new label space in data plane allowing
very easy and smooth migration to the number of applications choosing
to use Domain Wide MPLS Labels.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. MPLS Domain Wide Label Indicator . . . . . . . . . . . . . . 3
3. Control plane . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Data plane . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Advantages . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Deployment considerations . . . . . . . . . . . . . . . . . . 4
7. Security considerations . . . . . . . . . . . . . . . . . . . 4
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
10.1. Normative References . . . . . . . . . . . . . . . . . . 4
10.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
With the growing number of applications for Domain Wide Labels (by
some also referred to as "global labels") there is also growing
concern related to the ease of deployment considering various
restrictions for available in the platform's data plane label space
or taking into account existing deployments of LDP, RSVP-TE, BGP3107
etc and their coexistence with the introduction of new MPLS
signalling and mpls switching data plane paradigm.
To list just a few examples number of related work has been already
seen in this space: Segment Routing
[I-D.filsfils-rtgwg-segment-routing], PCE
[I-D.sivabalan-pce-segment-routing], RFC5331 [RFC5331], Advertising
MPLS labels in IGP [I-D.gredler-rtgwg-igp-label-advertisement], 2547
egress PE Fast Failure Protection
[I-D.minto-2547-egress-node-fast-protection] etc...
Fundamentally there are two solutions to address this problem. One
solution revolves around using the notion of local per node label
pools with offset added at each node resulting in making the label
locally assigned yet still globally significant. While doable and
successfully used as application labels (example: RFC4761 [RFC4761])
authors believe that for transport the further simplification to such
scheme is helpful.
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The second solution described in this memo proposes an explicit
separation of domain wide label space from any other transport or
application label space used already today. Such separation into
different LFIB is accomplished with the use of new type of context
label RFC5331 defined as MPLS Domain Wide Label Indicator.
2. MPLS Domain Wide Label Indicator
In order to explicitly indicate that next label in the MPLS label
stack of each transported packet is Domain Wide Labels the new
context label Domain Wide Label Indicator has been defined. The
value of the label is taken from the reserved label pool and has been
allocated by IANA *TBD*
The MPLS label stack entry has 4 octets where 20 bits indicate the
label value, S bit indicates End of Stack, 3 bits indicate QoS value
and remaining 8 bits indicate TTL field.
In Domain Wide Label Indicator the label value determines the
separate LFIB to be used during packet processing. The S bit MUST be
set to 0 and QoS bits are to be reserved. The TTL field MAY be
copied from the first transport label in the MPLS stack.
3. Control plane
The signalling of Domain Wide Labels itself is out of scope of this
document as there are already specifications for both ISIS
[I-D.previdi-isis-segment-routing-extensions] and OSPF
[I-D.psenak-ospf-segment-routing-extensions] protocols describing the
required extensions. The existing IGP protocol specifications can be
very easily extended with a new flag indicating support for Domain
Wide Label Indicator.
4. Data plane
The processing of MPLS packets already supports the notion of context
labels, recognizing and processing the reserved label space or both.
Redirection for lookup to separate LFIB table has also been supported
already by number of platforms mainly for efficient protection and
restoration applications.
In one of the application called Segment Routing the LER performing
the imposition may require multiple transport labels to be imposed on
the packet each indicating the segment to be traversed. The LSR
(often a PHP node, but also gateway between Domain Wide labels and
traditional/legacy label distribution protocols) which preforms the
POP of the last Domain Wide transport Label *as determined by the
control plane signalling* MUST also strip Domain Wide Label Indicator
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before passing the remaining of the label stack (possibly containing
application labels) to other components or to other peers.
5. Advantages
This document provides ability to explicitly signal the notion of
Domain Wide Labels carried in the MPLS header of the packets. The
main objective is to simplify forwarding planes of LSRs to perform
lookup based forwarding without additional label swap actions
therefore further contributing to cost reduction, and increase of
speed and port density. Such technique is equally applicable to
traditional routers as well as to new class of emerging forwarding
devices where FIBs or LFIBs are programmed remotely by centralized or
semi-centralized entities.
While this memo solely focuses on transport labels the notion of
domain wide labels can also be found applicable to application
labels. It is however out of scope of this document.
6. Deployment considerations
There are no new deployment requirements introduced by this document.
The ability to recognize support of domain wide label is to be
embedded within the specifications defining protocol extensions used
for signalling of domain wide labels.
7. Security considerations
No new security issues are introduced by this specification. There
is also no operator configuration or risk of misconfiguration
introduced by this specification.
8. IANA Considerations
IANA is requested to allocate a new reserved space MPLS label value
to be used as MPLS Domain Wide Label Indicator.
9. Acknowledgments
TBD
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
[RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
Label Assignment and Context-Specific Label Space", RFC
5331, August 2008.
10.2. Informative References
[I-D.filsfils-rtgwg-segment-routing]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
"Segment Routing Architecture", draft-filsfils-rtgwg-
segment-routing-01 (work in progress), October 2013.
[I-D.gredler-rtgwg-igp-label-advertisement]
Gredler, H., Amante, S., Scholl, T., and L. Jalil,
"Advertising MPLS labels in IGPs", draft-gredler-rtgwg-
igp-label-advertisement-05 (work in progress), May 2013.
[I-D.minto-2547-egress-node-fast-protection]
Jeganathan, J., Gredler, H., and B. Decraene, "2547 egress
PE Fast Failure Protection", draft-minto-2547-egress-node-
fast-protection-02 (work in progress), July 2013.
[I-D.previdi-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., and
S. Litkowski, "IS-IS Extensions for Segment Routing",
draft-previdi-isis-segment-routing-extensions-04 (work in
progress), October 2013.
[I-D.psenak-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., and W. Henderickx, "OSPF Extensions for
Segment Routing", draft-psenak-ospf-segment-routing-
extensions-03 (work in progress), October 2013.
[I-D.sivabalan-pce-segment-routing]
Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., and
R. Raszuk, "PCEP Extensions for Segment Routing", draft-
sivabalan-pce-segment-routing-02 (work in progress),
October 2013.
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[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling", RFC
4761, January 2007.
Author's Address
Robert Raszuk
NTT I3
101 S Ellsworth Avenue Suite 350
San Mateo, CA 94401
US
Email: robert@raszuk.net
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