MPLS Working Group Rajiv Asati
Internet Draft Cisco Systems
Intended status: Standards Track
Expires: July 2010 Ina Minei
Juniper Networks
Bob Thomas
March 4, 2010
Label Distribution Protocol (LDP) 'Typed Wildcard' Forward
Equivalence Class (FEC)
draft-ietf-mpls-ldp-typed-wildcard-07.txt
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on July 4, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
Asati, Thomas & Minei Expires July 4, 2010 [Page 1]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the BSD License.
Abstract
The Label Distribution Protocol (LDP) specification for the Wildcard
Forward Equivalence Class (FEC) element has several limitations.
This document addresses those limitations by defining a Typed
Wildcard FEC element and associated procedures. In addition, it
defines a new LDP capability to address backward compatibility.
Table of Contents
1. Introduction...................................................3
2. Specification Language.........................................4
3. The Typed Wildcard FEC Element.................................4
4. Procedures for the Typed Wildcard FEC Element..................5
5. Typed Wildcard FEC Capability..................................6
6. Typed Wildcard FEC Element for Prefix FEC Element..............7
7. Typed Wildcard FEC Element for Host and Wildcard FEC Elements..8
8. IANA Considerations............................................8
9. Security Considerations........................................9
10. Acknowledgments...............................................9
11. References...................................................10
11.1. Normative References....................................10
11.2. Informative References..................................10
Author's Addresses...............................................11
Asati, Thomas & Minei Expires July 4, 2010 [Page 2]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
1. Introduction
LDP [RFC5036] distributes labels for Forwarding Equivalence Classes
(FECs). LDP uses FEC TLVs in LDP messages to specify FECs. An LDP
FEC TLV includes 1 or more FEC Elements. A FEC element includes a
FEC type and an optional type-dependent value.
RFC5036 specifies two FEC types (Prefix and Wildcard), and other
documents specify additional FEC types; e.g., see [RFC4447] [MLDP].
As specified by RFC5036, the Wildcard FEC Element refers to all FECs
relative to an optional constraint. The only constraint RFC5036
specifies is one that limits the scope of the Wildcard FEC Element
to "all FECs bound to a given label".
The RFC5036 specification of the Wildcard FEC Element has the
following deficiencies which limit its utility:
1) The Wildcard FEC Element is untyped. There are situations where
it would be useful to be able to refer to all FECs of a given
type (as another constraint).
2) Use of the Wildcard FEC Element is limited to Label Withdraw and
Label Release messages only. There are situations where it would
be useful to have Wildcard FEC Element, with type constraint, in
Label Request messages.
This document:
- Addresses the above limitations by defining a Typed Wildcard
FEC Element and procedures for its use.
- Specifies use of the LDP capability mechanism [RFC5561] at
session establishment time for informing a peer that an LDP
speaker is capable of handling the Typed Wildcast FEC.
- Specifies use of Typed Wildcard FEC Element in Label Request
message.
- Specifies the Typed Wildcard FEC Element for the Prefix FEC
Element specified by RFC5036.
Note that this document does not change procedures specified for the
LDP Wildcard FEC Element by RFC5036.
Asati, Thomas & Minei Expires July 4, 2010 [Page 3]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
2. Specification 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].
LDP - Label Distribution Protocol
FEC - Forwarding Equivalence Class
TLV - Type Length Value
LSR - Label Switch Router
3. The Typed Wildcard FEC Element
The Typed Wildcard FEC Element refers to all FECs of the specified
type that meet the constraint. It specifies a 'FEC Element Type' and
an optional constraint, which is intended to provide additional
information.
The format of the Typed Wildcard FEC Element is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Typed (IANA) | FEC Element | Len FEC Type | |
| Wildcard | Type | Info | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
~ Additional FEC Type-specific Information ~
| (Optional) |
| +-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 Typed Wildcard FEC Element
where:
Asati, Thomas & Minei Expires July 4, 2010 [Page 4]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
Typed Wildcard : One octet FEC Element Type (to be assigned
by IANA).
FEC Element Type : One octet FEC Element Type that specifies
the FEC Element Type to be wildcarded. Please see section 3.4.1 of
RFC5036.
Any (future) document specifying new FEC Element Type (not
defined in RFC5630) should prescribe whether typed wildcarding
is needed for that FEC Element Type.
Len FEC Type Info : One octet that specifies the length in
octets of the FEC Type Specific information field. It MUST be set
to 0 if there is no Additional FEC Type-specific Information.
Additional FEC Type-specific Information: (Optional) Additional
information specific to the FEC Element Type required to fully
specify the Typed Wildcard. If this field is absent, then all FECs
of the specified FEC Type would be matched.
Any (future) document specifying Typed wildcarding for any FEC
Element Type should also specify the length and format of
Additional FEC Type Specific Information, if included.
This document specifies one FEC Element Type instance (e.g. Prefix
FEC) for the 'Typed Wildcard FEC Element' in section 6.
4. Procedures for the Typed Wildcard FEC Element
When a FEC TLV contains a Typed Wildcard FEC Element, the Typed
Wildcard FEC Element MUST be the only FEC Element in the TLV. If an
LDP speaker receives a FEC TLV containing Typed Wildcard FEC Element
and any other FEC Elements, then the LDP speaker should ignore the
other FEC Elements and continue processing as if the message had
contained only the Typed Wildcard FEC Element.
An LDP implementation that supports the Typed Wildcard FEC Element
MUST support its use in Label Request, Label Withdraw and Label
Release messages.
An LDP implementation that supports the Typed Wildcard FEC Element
MUST support it for every FEC Element Type implemented for which it
is defined.
Asati, Thomas & Minei Expires July 4, 2010 [Page 5]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
Receipt of a Label Request message with a FEC TLV containing a Typed
Wildcard FEC Element is interpreted as a request to send one or more
Label Mappings for all FECs of the type specified by the FEC Element
Type field in the Typed Wildcard FEC Element encoding.
An LDP implementation that supports the Typed Wildcard FEC Element
MUST support the following constraints whenever a Typed Wildcard FEC
appears in a Label Withdraw or Label Release message:
1) If the message carries an optional Label TLV the Typed Wildcard
FEC Element refers to all FECs of the specified FEC type bound to
the specified label.
2) If the message has no Label TLV the Typed Wildcard FEC Element
refers to all FECs of the specified FEC type.
Backwards compatibility with a router not supporting the Typed
Wildcard FEC element is ensured by the FEC procedures defined in
RFC5036. Quoting from RFC5036:
"If it" [an LSR] "encounters a FEC Element type it cannot decode,
it SHOULD stop decoding the FEC TLV, abort processing the message
containing the TLV, and send an "Unknown FEC" Notification message
to its LDP peer signaling an error."
A router receiving a FEC TLV containing a Typed Wildcard FEC element
for a FEC Element Type that it either doesn't support or for a FEC
Element Type that doesn't support the use of wildcarding, MUST stop
decoding the FEC TLV, abort processing the message containing the
TLV, and send an "Unknown FEC" Notification message to its LDP peer
signaling an error.
5. Typed Wildcard FEC Capability
As noted above, RFC5056 FEC procedures provide for backward
compatibility with an LSR not supporting the Typed Wildcard FEC
Element. However, they don't provide means for LSR wishing to use
the Typed Wildcard FEC Element to determine whether a peer supports
it other than to send a message that uses the FEC Element and to
wait and see how the peer responds.
An LDP speaker that supports the Typed Wildcard FEC Element MUST
inform its peers of the support by including a Typed Wildcard FEC
Element Capability Parameter [RFC5561] in its Initialization
messages.
Asati, Thomas & Minei Expires July 4, 2010 [Page 6]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
The Capability Parameter for the Typed Wildcard FEC capability is a
TLV with the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Typed WCard FEC Cap (IANA)| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved |
+-+-+-+-+-+-+-+-+
Figure 2 Typed Wildcard FEC Capability format
Where:
U and F bits : MUST be 1 and 0 respectively as per
section 3 of LDP Capabilities [RFC5561].
Typed WCard FEC Cap : TLV code point to be assigned by IANA.
S-bit : MUST be 1 (indicates that capability is
being advertised).
6. Typed Wildcard FEC Element for Prefix FEC Element
RFC5036 defines the Prefix FEC Element but it does not specify a
Typed Wildcard for it. This section specifies the Typed Wildcard
FEC Element for Prefix FEC Elements.
The format of the Prefix FEC Typed Wildcard FEC Element ("Prefix FEC
Wildcard" for short), based on Figure 1, is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Typed Wcard | Type = Prefix | Len = 2 | Address... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...Family |
+-+-+-+-+-+-+-+-+
Figure 3 Format of Prefix FEC Element using Typed Wildcard
Asati, Thomas & Minei Expires July 4, 2010 [Page 7]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
Where:
FEC Element Type : "Prefix" FEC Element (0x02, per RFC5036).
Len FEC Type Info : Two octets (=0x02).
Address Family : Two octet quantity containing a value from
ADDRESS FAMILY NUMBERS in [IANA-AF].
The procedures described in Section 4 apply to the Prefix FEC
Wildcard processing.
7. Typed Wildcard FEC Element for Host and Wildcard FEC Elements
There is no need to specify Typed Wildcard FEC Elements for the Host
FEC Element specified by [RFC3036], nor for the Wildcard FEC Element
specified by RFC5036. The [RFC3036] Host FEC Element has been
removed from RFC5036, and the Wildcard FEC Element is untyped by
definition.
In other words, the 'FEC Element Type' field in 'Typed Wildcard FEC
Element' MUST NOT be 0x01.
8. IANA Considerations
This draft introduces a new LDP FEC Element Type and a new LDP
Capability both of which require IANA assignment -
The 'Typed Wildcard' FEC Element requires a code point from the
LDP FEC Type Name Space. [RFC5036] partitions the FEC Type Name
Space into 3 regions: IETF Consensus region, First Come First
Served region, and Private Use region. The authors recommend
that the code point 0x05 from the IETF Consensus range be
assigned to the 'Typed Wildcard' FEC Element.
The 'Typed Wildcard FEC' Capability requires a code point from
the TLV Type name space. [RFC5036] partitions the TLV TYPE name
space into 3 regions: IETF Consensus region, Vendor Private Use
region, and Experimental Use region. The authors recommend that
a code point from the IETF Consensus range be assigned to the
'Typed Wildcard FEC' Capability.
Asati, Thomas & Minei Expires July 4, 2010 [Page 8]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
9. Security Considerations
No security considerations beyond those that apply to the base LDP
specification [RFC5036] and further described in [MPLSsec] apply to
use of the Typed Wildcard FEC Elements as described in this
document.
One could deduce that the security exposure is reduced by this
document, since an LDP speaker using Typed Wildcard FEC Element
could use a single message to request, withdraw or release all the
label mappings of a particular type (a particular AFI, for example),
whereas an LDP speaker using Wildcard FEC Element, as defined in
based LDP specification [RFC5036], could use a single message to
request, withdraw or release all the label mappings of all types
(all AFIs, for example).
10. Acknowledgments
The authors would like to thank Yakov Rekhter for suggesting that
the limitations of the Wildcard FEC be addressed. Also, thanks to
Adrian Farrel and Richard L. Barnes for extensive review of this
document.
This document was prepared using 2-Word-v2.0.template.dot.
Asati, Thomas & Minei Expires July 4, 2010 [Page 9]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5036] Andersson, L., Minei, I., and Thomas, B., "LDP
Specification", RFC 5036, October 2007.
[RFC5561] Thomas, B., Aggarwal, S., Aggarwal, R., Le Roux, J.L.,
"LDP Capabilities", RFC5561, May 2007.
11.2. Informative References
[RFC3036] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and
Thomas, B., "LDP Specification", RFC 3036, January 2001.
[RFC4447] Martini, L., Editor, "Pseudowire Setup and Maintenance
Using the label Distribution Protocol (LDP)", RFC4447,
April 2006.
[MLDP] Minei, I., Wijnands, I., Editors, "Label Distribution
Protocol Extensions for Point-to-Multipoint and
Multipoint-to-Multipoint Label Switched Paths", draft-
ietf-mpls-ldp-p2mp-08.txt, Work in Progress, Oct 2009.
[MPLSsec] Fang, L., "Security Framework for MPLS and GMPLS
Networks", draft-ietf-mpls-mpls-and-gmpls-security-
framework-07, Work in Progress, Oct 2009.
[IANA-AF] http://www.iana.org/assignments/address-family-numbers.
Asati, Thomas & Minei Expires July 4, 2010 [Page 10]
Internet-Draft draft-ietf-mpls-ldp-typed-wildcard March 4, 2010
Author's Addresses
Ina Minei
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
Email: ina@juniper.net
Bob Thomas
Email: bobthomas@alum.mit.edu
Rajiv Asati
Cisco Systems,
7025-6 Kit Creek Rd, RTP, NC, 27709-4987
Email: rajiva@cisco.com
Asati, Thomas & Minei Expires July 4, 2010 [Page 11]
