Network Working Group S Bryant. Bryant, Ed.
Internet-Draft M Morrow.
Intended status: Informational G Swallow.
Expires: August 11, 2008 Cisco Systems
R Cherukuri.
Juniper Networks,
T Nadeau.
BT
N Harrison.
BT Global Services
February 8, 2008
Application of Ethernet Pseudowires to MPLS Transport Networks
draft-ietf-pwe3-mpls-transport-02
Status of this Memo
By submitting this Internet-Draft, each author represents that any
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This Internet-Draft will expire on August 11, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
A requirement has been identified by the operator community for the
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transparent carriage of the MPLS network of one party over the MPLS
network of another party. This document describes an IETF-
recommended method of satisfying this need using the existing RFC4448
PWE3 Ethernet pseudowire standard.
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 . . . . . . . . . . . . . . . . . . . . . . 5
3. OAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. VCCV profile 1: BFD without IP/UDP Headers . . . . . . . . 5
3.2. VCCV profile 2: BFD with IP/UDP Headers . . . . . . . . . 6
4. MPLS Layer . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. External Configuration . . . . . . . . . . . . . . . . . . 6
4.2. Control Plane Configuration . . . . . . . . . . . . . . . 7
5. Congestion Considerations . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Introduction
The operator community has identified the need for the transparent
carriage of the MPLS network of one party over the MPLS network of
another party. This document describes one IETF-recommended
mechanism to satisfy this requirement using the existing RFC4448
[RFC4448] PWE3 Ethernet pseudowire standard. The mechanism described
here fulfills the requirements liaised to the IETF PWE3 working group
by the ITU: - [1]and [2].
The key purpose of this document is to demonstrate that there is an
existing IETF-recommended mechanism that satisfies the requirements
posed by the operator community. It is recognised that it is
possible to design a more efficient method of satisfying the
requirement, and the IETF anticipates that improved solutions will be
proposed in the future.
The architecture required for this mechanism is illustrated in Figure
1 below.
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+----------------------------------------------------------------+
| |
| IP/MPLS PSN (PHP may be enabled) |
| (client) |
| |
| +---------------------------+ |
| | | |
| | MPLS PSN (No PHP) | |
| | (server) | |
| | | |
| CE1 |PE1 PE2| CE2 |
| +-----+ +-----+ +-----+ +-----+ |
| | | | | | | | | | | | | | | | | |
| | | | +------+ | | | | | | +------+ | | | |
| | | | | 802.3| | | | | | | | 802.3| | | | |
| +-----+ +-----+ +-----+ +-----+ |
| | | | | | | | | |
| | | +-- ---------------------- -+ | | |
+----- --- -------- -- ---------------------- - -------- --- ----+
| | | |<--MPLS LSP (no PHP)->| | | |
| | | | (server) | | | |
| | | | | |
| | |<------------PW----------->| | |
| | | (server) | | |
| | | |
| |<-------------802.3 (Ethernet)-------------->| |
| | (client) | |
| |
|<---------IP/MPLS LSP (PHP may be supported)-------->|
| (client) |
Figure 1: Application Ethernet over MPLS PW to MPLS Transport
Networks
An 802.3 (Ethernet) circuit is established between CE1 and CE2. This
circuit may be used for the concurrent transport of MPLS packets as
well as IPv4 and IPv6 packets. The MPLS packets may carry IPv4,
IPV6, or Pseudowire payloads, and Penultimate-Hop-Popping (PHP) may
be used. For clarity these paths are labeled as the client in Figure
1.
An Ethernet pseudowire (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. For clarity this Ethernet PW and the MPLS PSN are labeled as
the server in Figure 1. In the remainder of this draft call the
server network a transport network.
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2. PWE3 Configuration
The PWE3 encapsulation used by this specification to satisfy the
transport requirement 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 required by the profile of the PWE3
Ethernet pseudowire functionality defined in this document.
The Pseudowire Label is statically provisioned.
3. OAM
Within a connection, traffic units sent from the single source are
constrained to stay within the connection under defect-free
conditions. During misconnected defects, a connection can no longer
be assumed to be constrained and traffic units (and by implication
also OAM packets) can 'leak' uni-directionally outside a connection.
Therefore during a misconnected state, it is not possible to rely on
OAM which relies on a request/response mechanism ; and, for this
reason such OAM should be treated with caution if used for diagnostic
purposes.
Further, when implementing an ECMP function with MPLS, use of the
label stack as the path selector such that the OAM and data are not
in a co-path as any failure in the data path will note be reflected
in the OAM path. Therefore, an OAM that is carried within the data-
path below the PW label such as VCCV is NOT vulnerable to the above
failure mode. For these reasons the OAM mechanism is RFC5085
[RFC5085], using Bidirectional Forwarding Detection (BDF) BFD
[I-D.ietf-bfd-base] for connection verification (CV). The method of
using BFD as a CV method in VCCV is described in
[I-D.draft-ietf-pwe3-vccv-bfd] . One of the VCCV profiles described
in Section 3.1 or Section 3.2 MUST be used. Once a VCCV 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
When PE1 and PE1 are not IP capable or have not been configured with
IP addresses, the following VCCV mechanism SHOULD be used.
The connection verification method used by VCCV is BFD with
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diagnostics as defined in [I-D.draft-ietf-pwe3-vccv-bfd].
RFC5085 [RFC5085] specifies that the first nibble is set to 0x1 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 [TBD] to indicate that the payload carried is BFD
without IP/UDP headers, as is defined in
[I-D.draft-ietf-pwe3-vccv-bfd].
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.
The connection verification method used by VCCV is BFD with
diagnostics as defined in [I-D.draft-ietf-pwe3-vccv-bfd].
RFC5085 [RFC5085]specifies that the first nibble is set to 0x1 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].
4. MPLS Layer
The architecture of MPLS enabled networks is described in RFC3031
[RFC3031] PSN . This section describes a subset of the functionality
of the MPLS enabled PSN. There are two cases that need to be
considered:
1. The case where external configuration is used.
2. The case where a control plane is available.
Where the use of a control plane is desired this may be based on
GMPLS[RFC3945]
4.1. External Configuration
The use of external provisioning is not precluded from being
supported by the current MPLS specifications. It is however
expicitly described in this specification to addess the requirements
specified by the ITU <https://datatracker.ietf.org/public/
liaison_detail.cgi?detail_id=286> and <https://datatracker.ietf.org/
public/liaison_detail.cgi?detail_id=287> to address the needs in a
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transport environment.
The MPLS encapsulation is specified inRFC3032 [RFC3032]. All MPLS
labels used in the server layer (Figure 1) MUST be statically
provisioned. Labels may be selected from either the per-platform or
the per-interface label space.
All 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 transport LSRs MUST be disabled on
transport LSPs.
Both E-LSP and L-LSP MUST be supported as defined in RFC3270
[RFC3270].
For the MPLS EXP field RFC3270 [RFC3270] only the pipe and short-pipe
models are supported.
4.2. Control Plane Configuration
In this section we describe the control plane configuration
whenRFC3209 [RFC3209] "RSVP-TE: Extensions to RSVP for LSP Tunnels"
or the bi-directional support in GMPLS RFC3471 [RFC3471] "Generalized
Multi-Protocol Label Switching (GMPLS) Signaling Functional
Description" andRFC3473 [RFC3473] "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions" are used to configure the transport
MPLS PSN. When these protocols are used to provide the control plane
the following are automatically provided:
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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).
3. Label switched 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 NOPHP
[I-D.ali-mpls-rsvp-te-no-php-oob-mapping].
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 describes a method of using the existing RFC4448 [RFC4448]
PWE3 Ethernet pseudowire to solve a particular network application.
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
This draft is a description of the use of existing IETF proposed
standards to solve a network problem, and raises no new security
issues.
The PWE3 security considerations are described in RFC3985
[RFC3985]and the Ethernet pseudowire security consoderations RFC4448
[RFC4448]
The Ethernet pseudowire is transported on an MPLS PSN; therefore, the
security of the pseudowire itself will only be as good as the
security of the MPLS PSN. The server MPLS PSN can be secured by
various methods, as described in RFC3031. [RFC3031]
The use of static configuration exposes an MPLS PSN to a different
set of security risks to those found in a PSN using dynamic routing.
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If a path is missconfigured in a staticly configued network the
result can be a persistent black hole, or much worst, a persistent
forwarding loop. On the otherhand most of the distributed components
are less complex. This is however offset by the need to provide
failover and redundancy in the management and configuration system
and the communications paths between those central systems and the
LSRs.
Security achieved by access control of MAC addresses , and the
security of the client layers is out of the scope of this document.
7. IANA Considerations
There are no IANA actions required by this draft.
8. Acknowledgements
The authors wish to thank John Dake, Adrian Farrel, Andy Malis, Ben
Niven-Jenkins, and Yaakov Stein for their review and proposed
enhancements to the text.
9. References
9.1. Normative References
[I-D.ali-mpls-rsvp-te-no-php-oob-mapping]
Ali, Z., "Non PHP Behavior and out-of-band mapping for
RSVP-TE LSPs",
draft-ali-mpls-rsvp-te-no-php-oob-mapping-01 (work in
progress), July 2007.
[I-D.ietf-bfd-base]
Katz, D. and D. Ward, "Bidirectional Forwarding
Detection", draft-ietf-bfd-base-07 (work in progress),
January 2008.
[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.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
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[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.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
(GMPLS) Architecture", RFC 3945, October 2004.
[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.
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
9.2. 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
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
Thomas D. Nadeau
BT
Email: tom.nadeau@bt.com
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Neil Harrison
BT Global Services
CTO, Network Architecture
Email: neil.2.harrison@bt.com
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