Network Working Group S Bryant. Bryant, Ed.
Internet-Draft M Morrow.
Intended status: Informational T Nadeau.
Expires: November 22, 2007 G Swallow.
Cisco Systems
R Cherukuri.
Juniper Networks,
N Harrison.
BT Global Services
May 21, 2007
Application of PWE3 to MPLS Transport Networks
draft-ietf-pwe3-mpls-transport-00
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
A key requirement has been identified by the operator community for
the transparent carriage of the MPLS network of one party over the
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MPLS network of another party. This document describes one IETF-
recommended profile to satisfy this requirement using the existing
RFC4448 PWE3 Ethernet pseudowire standard. This solution does not
preclude other solutions being developed in the future.
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 RFC2119 [RFC2119].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. PWE3 Configuration . . . . . . . . . . . . . . . . . . . . . . 4
3. OAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. VCCV profile 1: BFD without IP/UDP Headers . . . . . . . . 5
3.2. VCCV profile 2: BFD with IP/UDP Headers . . . . . . . . . 5
4. MPLS Layer . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. External Configuration . . . . . . . . . . . . . . . . . . 6
4.2. Control Plane Configuration . . . . . . . . . . . . . . . 6
5. Congestion Considerations . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . . . 11
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1. Introduction
MPLS [RFC3031] is based on the ability to arbitrarily stack label
switched paths (LSPs). Such stacked LSPs all belong to the same MPLS
layer network. The limited isolation provided by this mechanism
means that it is not possible to directly carry an LSP belonging to
the MPLS network of party A over an LSP belonging to the MPLS network
of party B in a truly transparent, functionally decoupled manner. In
other words, stacked LSPs do not intrinsically provide a client-
server layer network relationship. Several operators have identified
this as a problem that requires urgent attention.
One solution to the problem is to use existing pseudo-wire (PW)
techniques to insert a 'functional other technology breakwater'
between the two MPLS networks (of say party A and party B as noted
above). This could in principle use any PW technology. However, in
this document we restrict our solution to using an Ethernet PW as
defined in RFC4448 [RFC4448] . The design described here fulfills
the requirements liaised to the IETF PWE3 working group by the ITU
- [1]- [2]
Note that this does not preclude other solutions emerging in the
future. The key purpose of this document is to show that there
exists a solution to the problem posed by the operator community
using already defined IETF standards.
This document is focused on providing a client/server relationship
between two MPLS networks owned/operated by different parties, as
this is the essential requirement that operators have indicated must
be met from the larger set of "transport network" requirements
generated in the liaison to the IETF PWE3 WG from ITU SG15ITU2 [2].
The architecture required for this configuration is illustrated in
Figure 1 below.
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+----------------------------------------------------------------+
| |
| IP/MPLS PSN (PHP may be enabled) |
| |
| +---------------------------+ |
| | | |
| | MPLS PSN (No PHP) | |
| | | |
| CE1 |PE1 PE2| CE2 |
| +-----+ +-----+ +-----+ +-----+ |
| | | | | | | | | | | | | | | | | |
| | | | +------+ | | | | | | +------+ | | | |
| | | | | 802.3| | | | | | | | 802.3| | | | |
| +-----+ +-----+ +-----+ +-----+ |
| | | | | | | | | |
| | | +-- ---------------------- -+ | | |
+----- --- -------- -- ---------------------- - -------- --- ----+
| | | |<--MPLS PSN (no PHP)->| | | |
| | | | | |
| | |<------------PW----------->| | |
| | | |
| |<-------------802.3 (Ethernet)-------------->| |
| |
|<---------IP/MPLS LSP (PHP may be supported)-------->|
Figure 1: Application PWE3 to MPLS Transport Networks
An IP or an MPLS Label Switched Path (LSP) must be established
between CE1 and CE2. This MPLS PSN may utilize Penultimate-Hop
Popping (PHP). This LSP is to be carried over Ethernet. An Ethernet
PW is provisioned between PE1 and PE2 and used to carry the Ethernet
from PE1 to PE2. The Ethernet PW is carried over an MPLS PSN, but
this PSN MUST NOT be configured with PHP.
2. PWE3 Configuration
The only PWE3 encapsulation that is supported in this version of the
profile is Ethernet RFC4448 [RFC4448]. This is used in "raw" mode.
The Control Word MUST be used. The Sequence number MUST be zero.
The use of the Pseudowire Setup and Maintenance Label Distribution
Protocol RFC4447 [RFC4447] is not supported in this version of the
profile.
The Pseudowire Label is statically provisioned.
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3. OAM
The OAM mechanism is VCCV [I-D.ietf-pwe3-vccv]. One of the VCCV
profiles described in Section 3.1 or Section 3.2 MUST be used. Once
a VCCV profile is provisioned, and the operational status of the PW
is UP, no other profile SHOULD be used until such time as the PW's
operational status is set to DOWN.
3.1. VCCV profile 1: BFD without IP/UDP Headers
As specified in VCCV [I-D.ietf-pwe3-vccv], the first nibble is set to
0001b to indicate a channel associated with a pseudowire RFC4385
[RFC4385]. The Version and the Reserved fields are set to 0, and the
Channel Type is set to 0x07 to indicate that the payload carried is
BFD without IP/UDP headers, as is defined in section 4.1.1 of VCCV
[I-D.ietf-pwe3-vccv].
The connection verification method used by VCCV is BFD with
diagnostics as defined in 4.1 of VCCV [I-D.ietf-pwe3-vccv].
3.2. VCCV profile 2: BFD with IP/UDP Headers
When PE1 and PE1 are IP capable and have been configured with IP
addresses, the following VCCV mechanism MAY be used.
As specified in VCCV [I-D.ietf-pwe3-vccv], the first nibble is set to
0001b to indicate a channel associated with a pseudowire RFC4385
[RFC4385]. The Version and the Reserved fields are set to 0, and the
Channel Type is set to 0x21 for IPv4 and 0x56 for IPv6 payloads
RFC4446 [RFC4446].
The connection verification method used by VCCV is BFD with
diagnostics as defined in 4.1 of VCCV [I-D.ietf-pwe3-vccv].
4. MPLS Layer
This section describes the profile of the MPLS RFC3031 [RFC3031] PSN
. The profile considers two cases:
1. The case where external configuration is used
2. The case where a control plane is available
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4.1. External Configuration
All MPLS labels RFC3032 [RFC3032] used by the transport LSPs
supporting (i.e. acting as a server to) the PWs described in section
2 MUST be statically provisioned. Labels may be selected from the
per-platform or the per-interface label space.
All LSPs for the transport LSPs utilized by the PWs described in
section 2 MUST support both unidirectional and bi-directional point-
to-point connections.
The transport LSPs SHOULD support unidirectional point-to-multipoint
connections.
The forward and backward directions of a bi-directional connection
should follow a symmetrically routed (reciprocal) LSP in the server
network.
Equal cost multi-path (ECMP) load balancing MUST NOT be configured on
the transport LSPs utilized by the PWs described in sections 2.
The merging of label switched paths is prohibited and MUST NOT be
configured for the transport LSPs utilized by the PWs described in
section 2.
Penultimate hop popping by the LSRs MUST be disabled on LSPs
providing PWE3 transport network functionality.
Both E-LSP and L-LSP MUST be supported as defined in RFC3270
[RFC3270].
The MPLS EXP field is supported according to RFC3270 for only when
the pipe and short-pipe models are utilized.
4.2. Control Plane Configuration
In this section we describe the profile when RSVP-TE RFC3209
[RFC3209] or the bi-directional support in GMPLS RFC3471 [RFC3471]
RFC3473 [RFC3473] are used to configure the MPLS PSN used to provide
the transport LSPs. When these protocols are used to provide the
control plane the following are automatically provided:
1. There is no label merging unless it is deliberately enabled to
support Fast Re-route (FRR) RFC3209 [RFC3209].
2. A single path is provided end-to-end (There is no ECMP).
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3. Paths may be unidirectional or bidirectional as required.
Additionally the following configurations restrictions required to
support external configuration MUST be applied:
o Penultimate hop popping by the LSRs MUST be disabled on LSPs
providing PWE3 transport network functionality.
o Both E-LSP and L-LSP MUST be supported as defined in RFC3270
[RFC3270].
o The MPLS EXP field is supported according to RFC3270 for only when
the pipe and short-pipe models are utilized.
5. Congestion Considerations
This draft is a profile of an RFC4448 [RFC4448] PWE3 Ethernet
pseudowire. The congestion considerations associated with that
pseudowire and all subsequent work on congestion considerations
regarding Ethernet pseudowires is applicable to this draft.
6. Security Considerations
PWE3 security considerations are described in RFC3985 [RFC3985].
This draft is a profile of existing IETF proposed standards and
raises no new security issues.
7. IANA Considerations
There are no IANA actions required by this draft.
8. References
8.1. Normative References
[I-D.ietf-pwe3-vccv]
Nadeau, T., "Pseudo Wire Virtual Circuit Connectivity
Verification (VCCV)", draft-ietf-pwe3-vccv-13 (work in
progress), March 2007.
[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.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, May 2002.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, February 2006.
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge
Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4448] Martini, L., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, April 2006.
8.2. Informative References
[RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
Edge (PWE3) Architecture", RFC 3985, March 2005.
URIs
[1] <https://datatracker.ietf.org/public/
liaison_detail.cgi?detail_id=286>
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[2] <https://datatracker.ietf.org/public/
liaison_detail.cgi?detail_id=287>
Authors' Addresses
Stewart Bryant (editor)
Cisco Systems
250, Longwater, Green Park,
Reading RG2 6GB, UK
UK
Email: stbryant@cisco.com
Monique Morrow
Cisco Systems
Glatt-com
CH-8301 Glattzentrum
Switzerland
Email: mmorrow@cisco.com
Thomas D. Nadeau
Cisco Systems
300 Beaver Brook Drive
Boxborough, MA
USA
Email: tnadeau@cisco.com
George Swallow
Cisco Systems
1414 Massachusetts Ave
Boxborough, MA 01719
Email: swallow@cisco.com
Rao Cherukuri
Juniper Networks,
1194 N. Mathilda Ave
Sunnyvale CA 94089
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Neil Harrison
BT Global Services
CTO, Network Architecture
Email: neil.2.harrison@bt.com
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