Network Working Group Kamran Raza
Internet Draft Cisco Systems
Intended Status: Standards Track
Expiration Date: January 7, 2011 Sami Boutros
Cisco Systems
July 8, 2010
LDP Typed Wildcard PW FEC Elements
draft-raza-l2vpn-pw-typed-wc-fec-01.txt
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Abstract
An extension to the Label Distribution Protocol (LDP) defines the
general notion of a "Typed Wildcard Forwarding Equivalence Class
(FEC) Element". This can be used when it is desired to request all
label bindings for a given type of FEC Element, or to release or
withdraw all label bindings for a given type of FEC element.
However, a typed wildcard FEC element must be individually defined
for each type of FEC element. This specification defines the typed
wildcard FEC elements for the Pseudowire Identifier (PW Id) and
Generalized Pseudowire Identifier (Gen. PW Id) FEC types.
Conventions used in this document
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].
Table of Contents
1. Introduction 3
2. Typed Wildcard for PWid FEC Element 3
3. Typed Wildcard for Generalized PWid FEC Element 3
4. Operation 3
4.1. PW Consistency Check 4
4.2. PW Graceful Shutdown 5
5. Security Considerations 5
6. IANA Considerations 5
7. Acknowledgments 5
8. References 5
8.1. Normative References 5
8.2. Informative References 6
Author's Address 6
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1. Introduction
An extension [TYPED-WC] to the Label Distribution Protocol (LDP)
[RFC5036] defines the general notion of a "Typed Wildcard
Forwarding Equivalence Class (FEC) Element". This can be used
when it is desired to request all label bindings for a given type
of FEC Element, or to release or withdraw all label bindings for
a given type of FEC element. However, a typed wildcard FEC
element must be individually defined for each type of FEC element.
[RFC4447] defines the "PWid FEC Element" and "Generalized PWid
FEC Element" but it does not specify Typed Wildcard format for
these elements. This document specifies the format of the Typed
Wildcard FEC for the "PWid FEC Element" and the "Generalized
PWid FEC Element" defined in [RFC4447]. The procedures for Typed
Wildcard processing for PWid and Generalized PWid FEC Elements are
same as described in [TYPED-WC] for any typed wildcard FEC Element
type.
2. Typed Wildcard for PWid FEC Element
The format of the PWid FEC Typed Wildcard FEC is:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Typed Wcard | Type = PWid | Len = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Format of PWid Typed Wildcard FEC Element
Where:
Typed Wcard (one octet): as specified in [TYPED-WC]
FEC Element Type (one octet): PWid FEC Element (type 0x80
[RFC4447])
Len FEC Type Info (one octet): Zero. (There is no additional FEC
info)
3. Typed Wildcard for Generalized PWid FEC Element
The format of the Generalized PWid FEC Typed Wildcard FEC is:
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0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Typed Wcard | Type=Gen.PWid | Len = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Format of Generalized PWid Typed Wildcard FEC Element
Where:
Typed Wcard (one octet): as specified in [TYPED-WC]
FEC Element Type (one octet): Generalized PWid FEC Element (type
0x81 [RFC4447])
Len FEC Type Info (one octet): Zero. (There is no additional FEC
info)
When Generalized PWid FEC Typed Wildcard is used, "PW Grouping ID
TLV" [RFC4447] MUST NOT be present in the same message.
4. Operation
The use of Typed Wildcard FEC elements for PW can be useful under
several scenarios. This section describes two use cases to
illustrate their usage. The following use cases consider two LSR
nodes, A and B, with LDP session between them to exchange L2VPN PW
bindings.
4.1. PW Consistency Check
A user may request a control plane consistency check at LSR A for
the PWid FEC and Generalized PWid FEC bindings that it had learnt
from LSR B over LDP session. To perform this consistency check, LSR
A marks all its learnt PW bindings from LSR B as stale, and then
sends a Label Request message towards LSR B with Typed Wildcard FEC
element for PWid FEC element and Generalized PWid FEC element. Upon
receipt of such request, LSR B replays its database related to PWid
FEC elements and Generalized PWid FEC element in Label Mapping
message. As a PW binding is received at LSR A, the associated
binding state is marked as refreshed (no stale). When replay
completes for a given type of FEC, LSR B sends End-of-LIB
Notification [END-OF-LIB] to mark the end of update for the given
FEC type. Upon receipt of this Notification at LSR A, any remaining
stale PW binding of given FEC type learnt from the peer LSR B, is
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cleaned up and removed from the database. This completes consistency
check with LSR B at LSR A for given FEC type.
4.2. PW Graceful Shutdown
It may be desirable to perform shutdown/removal of existing PW
bindings advertised towards a peer in a graceful manner -
- i.e. all
advertised PW bindings to be removed from a peer without session
flap. For example, to request a graceful delete of the PWid FEC and
Generalized PWid FEC bindings at LSR A learnt from LSR B, LSR A
would send a Label Withdraw message towards LSR B with Typed
Wildcard FEC elements pertaining to PWid FEC element and Generalized
PWid FEC element. Upon receipt of such message, LSR B will delete
all PWid and Generalized PWid bindings learnt from LSR A.
Afterwards, LSR B would send Label Release message corresponding to
recieved Label Withdraw with Typed FEC element.
5. Security Considerations
No new security considerations beyond that apply to the base LDP
specification [RFC5036], [RFC4447] and [MPLS_SEC] apply to the use
of the PW Typed Wildcard FEC Element types described in this
document.
6. IANA Considerations
This document defines no new element for IANA Consideration.
7. Acknowledgments
The authors would like to thank Eric Rosen, M. Siva, and Zafar Ali
for their valuable comments.
This document was prepared using 2-Word-v2.0 template.dot.
8. References
8.1. Normative References
[RFC5036] Andersson, L., Menei, I., and Thomas, B., Editors, "LDP
Specification", RFC 5036, September 2007.
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[TYPED-WC] Thomas, B., Asati, R., and Minei, I., "LDP Typed Wildcard
FEC", draft-ietf-mpls-ldp-typed-wildcard-07.txt, Work in
Progress, March 2010.
[END-OF-LIB] Asati, R., Mohapatra, P., Chen, E., and Thomas, B.,
"Signaling LDP Label Advertisement Completion",
draft-ietf-mpls-ldp-end-of-lib-04.txt, Work in Progress,
June 2010.
[RFC4447] L. Martini, Editor, E. Rosen, El-Aawar, T. Smith, G. Heron,
"Pseudowire Setup and Maintenance using the Label
Distribution Protocol", RFC 4447, April 2006.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC2119, March 1997.
8.2. Informative References
[MPLS_SEC] Fang, L. et al., "Security Framework for MPLS and GMPLS
Networks", draft-ietf-mpls-mpls-and-gmpls-security-
framework-05.txt, Work in Progress, March 2009.
Author's Address
Syed Kamran Raza
Cisco Systems, Inc.,
2000 Innovation Drive,
Kanata, ON K2K-3E8, Canada.
E-mail: skraza@cisco.com
Sami Boutros
Cisco Systems, Inc.
3750 Cisco Way,
San Jose, CA 95134, USA.
E-mail: sboutros@cisco.com
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