Network Working Group S. Bryant, Ed.
Internet-Draft M. Morrow
Intended status: Informational G. Swallow
Expires: August 31, 2009 Cisco Systems
R. Cherukuri
Juniper Networks,
T. Nadeau
N. Harrison
B. Niven-Jenkins
BT
February 27, 2009
Application of Ethernet Pseudowires to MPLS Transport Networks
draft-ietf-pwe3-mpls-transport-03
Status of this Memo
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and restrictions with respect to this document.
Abstract
A requirement has been identified by the operator community for the
transparent carriage of the MPLS(-TP) network of one party over the
MPLS(-TP) network of another party. This document describes a method
of satisfying this need using the existing PWE3 Ethernet pseudowire
standard RFC4448.
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 . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
The operator community has identified the need for the transparent
carriage of the MPLS(-TP) network of one party over the MPLS(-TP)
network of another party [I-D.ietf-mpls-tp-requirements]. This
document describes one mechanism to satisfy this requirement using
existing IETF standards such as PWE3 Ethernet pseudowire standard
[RFC4448] . The mechanism described here fulfills the MPLS-TP
requirements for transparent carriage (MPLS-TP requirements 20 & 21)
of the Ethernet data plane.
The key purpose of this document is to demonstrate that there is an
existing IETF mechanism with known implementations 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
requirements, and the IETF anticipates that improved solutions will
be proposed in the future.
Much of the notation used in this document is defined in [RFC3985] to
which the reader is referred for definitions.
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 packet switched Netwok (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]. 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] 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 Equal Cost Multi-path (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 Virtual
Circuit Connectivity Verification (VCCV) is NOT vulnerable to the
above failure mode. For these reasons the OAM mechanism is
[RFC5085], using Bidirectional Forwarding Detection (BDF)
[I-D.ietf-bfd-base] for connection verification (CV). The method of
using Bidirectional Forwarding Detection (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 control channel 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.
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The connection verification method used by VCCV is BFD with
diagnostics as defined in [I-D.draft-ietf-pwe3-vccv-bfd].
[RFC5085] specifies that the first nibble is set to 0x1 to indicate a
channel associated with a pseudowire [RFC4385].
The Version and the Reserved fields are set to zero, 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] specifies that the first nibble is set to 0x1 to indicate a
channel associated with a pseudowire [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].
4. MPLS Layer
The architecture of MPLS enabled networks is described in [RFC3031].
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
Generalized Multi-Protocol Label Switching (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 [I-D.ietf-mpls-tp-requirements] to address the
needs in a transport environment.
The MPLS encapsulation is specified in [RFC3032]. All MPLS labels
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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 Label Switched Paths (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 label switched routers
(LSRs) must be disabled on transport LSPs.
Both EXP-Inferred-PSC LSPs (E-LSP) and Label-Only-Inferred-PSC LSPs
(L-LSP) must be supported as defined in [RFC3270].
For the MPLS EXP field [RFC3270] [RFC5462] only the pipe and short-
pipe models are supported.
4.2. Control Plane Configuration
In this section we describe the control plane configuration
when[RFC3209] "RSVP-TE: Extensions to RSVP for LSP Tunnels" or the
bi-directional support in GMPLS [RFC3471] "Generalized Multi-Protocol
Label Switching (GMPLS) Signaling Functional Description"
and[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:
1. There is no label merging unless it is deliberately enabled to
support Fast Re-route (FRR) [RFC3209].
2. A single path is provided end-to-end (there is no ECMP).
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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
[I-D.ali-mpls-rsvp-te-no-php-oob-mapping].
o Both E-LSP and L-LSP must be supported as defined in [RFC3270].
o The MPLS EXP [RFC5462] 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 PWE3 Ethernet
pseudowire [RFC4448] 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] and the
Ethernet pseudowire security considerations of[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].
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.
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.
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Security achieved by access control of media access control (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 Matthew Bocci, John Drake, Adrian Farrel,
Andy Malis, 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-09 (work in progress),
February 2009.
[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.
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[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.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, February 2009.
9.2. Informative References
[I-D.ietf-mpls-tp-requirements]
Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
and S. Ueno, "MPLS-TP Requirements",
draft-ietf-mpls-tp-requirements-04 (work in progress),
February 2009.
[RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
Edge (PWE3) Architecture", RFC 3985, March 2005.
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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
Neil Harrison
BT
Email: neil.2.harrison@bt.com
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Ben Niven-Jenkins
BT
208 Callisto House, Adastral Park
Ipswich, Suffolk IP5 3RE
UK
Phone:
Fax:
Email: benjamin.niven-jenkins@bt.com
URI:
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