Network Working Group A. Lindem (Editor)
Internet-Draft Cisco Systems, Inc
Expires: May 30, 2005 N. Shen
BCN Networks, Inc
R. Aggarwal
Juniper Networks
S. Schaffer
BridgePort Networks
JP. Vasseur
Cisco Systems, Inc
November 29, 2004
Extensions to OSPF for Advertising Optional Router Capabilities
draft-ietf-ospf-cap-04.txt
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Copyright (C) The Internet Society (2004).
Abstract
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It is useful for routers in an OSPF routing domain to know the
capabilities of their neighbors and other routers in the OSPF routing
domain. This draft proposes extensions to OSPF for advertising
optional router capabilities. A new Router Information (RI) opaque
LSA is proposed for this purpose.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. OSPF Router Information (RI) Opaque LSA . . . . . . . . . . . 4
2.1 OSPF Router Capabilities TLV . . . . . . . . . . . . . . . 5
2.2 Reserved OSPF Router Capability Bits . . . . . . . . . . . 6
2.3 Flooding Scope of the Router Information LSA . . . . . . . 6
3. Security Considerations . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 Normative References . . . . . . . . . . . . . . . . . . . . 10
5.2 Informative References . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 10
A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . 13
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1. Introduction
It is useful for routers in an OSPF routing domain to know the
capabilities of their neighbors and other routers in the OSPF routing
domain. This can be useful for various applications:
o In MPLS Traffic Engineering (TE), it can be used as a discovery
mechanism [TECAP] to announce a LSR's TE capabilities like Path
Computation Server capability (Capability of an LSR to be a Path
Computation Server for TE LSP path computation) or the intention
of an LSR to be part of a particular MPLS TE mesh group.
o For network management and troubleshooting. It gives operators a
network wide view of OSPF capabilities on different routers. The
presence of a capability on a given router implies that the
software version supports the capability and the router is
configured to support it. On the other hand, the absence of an
expected capability on a particular router can imply either
misconfiguration or an incorrect software version. Hence, this
capability information can be used to track problems resulting
from misconfiguration or an incorrect software version.
OSPF uses the options field in the hello packet to advertise optional
router capabilities [OSPF]. However, all the bits in this field have
been allocated and there is no way to advertise new optional or MPLS
TE capabilities. This document proposes extensions to OSPF to
advertise these optional capabilities. For existing OSPF
capabilities, this advertisement will be used primarily for
informational purposes. For MPLS TE features, it is used for
advertisement and discovery. Future OSPF features could also use
this mechanism for advertisement and discovery.
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2. OSPF Router Information (RI) Opaque LSA
OSPF routers will optionally advertise their optional capabilities in
an area-scoped, local scope, or AS-scoped Opaque-LSA [OPAQUE]. If a
router does not advertise this LSA, it does not imply that the router
does not support one or more of the defined capabilities. For
existing OSPF capabilities, this advertisement will be used primarily
for informational purposes. For MPLS TE features, it is used for
advertisement and discovery. Future OSPF features could also use
this mechanism for advertisement and discovery. The RI opaque LSA
will be originated when one of the advertised capabilities is
configured or changed.
The Router Information LSA will have an Opaque type of 4 and Opaque
ID of 0.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 9, 10 or 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- TLV's -+
| ... |
The format of the TLV's within the body of a router information LSA
is the same as the format used by the Traffic Engineering Extensions
to OSPF [TE]. The LSA payload consists of one or more nested Type/
Length/Value (TLV) triplets. The format of each TLV is:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Length field defines the length of the value portion in octets
(thus a TLV with no value portion would have a length of zero). The
TLV is padded to four-octet alignment; padding is not included in
the length field (so a three octet value would have a length of
three, but the total size of the TLV would be eight octets). Nested
TLV's are also 32-bit aligned. For example, a one byte value would
have the length field set to 1, and three bytes of padding would be
added to the end of the value portion of the TLV. Unrecognized types
are ignored.
2.1 OSPF Router Capabilities TLV
The first defined TLV in the body of an RI opaque LSA is the Router
Capabilities TLV. A router advertising an RI opaque LSA SHOULD
include the Router Capabilities TLV and SHOULD correctly identify the
status of the capabilities defined in section 2.2.
The format of the Router Capabilities TLV is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Capabilities |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type A 16 bit field set to 1.
Length A 16 bit field that indicates the length of the value
portion in bytes. Its set to N x 4 octets. N starts
from 1 and can be increased when there is a need. Each 4
octets are referred to as a capability flag.
Value This comprises one or more capability flags. For each 4
octets, the bits are indexed from the most significant
to the least significant, where each bit represents one
router capability. When the first 32 capabilities are
defined, a new capability flag will be used to
accommodate the next capability.
The Router Capabilities TLV MAY be followed by optional TLV's that
further specify a capability.
2.2 Reserved OSPF Router Capability Bits
The following bits in the first capability flag have been assigned:
Bit Capabilities
0-3 Reserved
4 OSPF graceful restart capable [GRACE]
5 OSPF graceful restart helper [GRACE]
6 OSPF Stub Router support [STUB]
7 OSPF Traffic Engineering support [TE]
8 OSPF point-to-point over LAN [P2PLAN]
9 OSPF Path Computation Server discovery [TECAP]
10 OSPF Experimental TE [EXPTE]
11-31 Future assignments
2.3 Flooding Scope of the Router Information LSA
The flooding scope for a Router Information opaque LSA is determined
by the LSA type. A type 9 (link-scope), type 10 (area-scoped), or a
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type 11 (AS-scoped) opaque LSA may be flooded. If a type 11 opaque
LSA is chosen, the originating router should also advertise type 10
LSA(s) into any attached NSSA/stub area(s). An OSPF router MAY
advertise different capabilities when both NSSA/stub area type 10
LSA(s) and an AS scoped type 11 opaque LSA is advertised. The choice
of flooding scope is made by the advertising router and is a matter
of local policy. The originating router MAY advertise multiple RI
opaque LSAs as long as the flooding scopes differ. TLV flooding
scope rules will be specified on a per-TLV basis.
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3. Security Considerations
This memo does not create any new security issues for the OSPF
protocol. Security considerations for the base OSPF protocol are
covered in [OSPF].
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4. IANA Considerations
A new opaque LSA type will need to be assigned by IANA.
Additionally, IANA will need to have registries for the Router
Information opaque LSA TLV's. The TLV assignee will be responsible
for allocation of any sub-TLV's for the IANA assigned TLV. All TLV's
and sub-TLV's will be subject to OSPF WG review.
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5. References
5.1 Normative References
[OSPF] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[RFC2119] Bradner, S., "Key words for use in RFC's to Indicate
Requirement Levels", RFC 2328, March 1977.
[TE] Katz, D., Yeung, D. and K. Kompella, "Traffic Engineering
Extensions to OSPF", RFC 3630, September 2003.
5.2 Informative References
[EXPTE] Srisuresh, P. and P. Joseph, "OSPF OSPF-TE: An
experimental extension to OSPF for Traffic Engineering",
draft-srisuresh-ospf-te-07.txt (work in progress).
[GRACE] Moy, J., Pillay-Esnault, P. and A. Lindem, "Graceful OSPF
Restart", RFC 3623, November 2003.
[OPAQUE] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July
1998.
[P2PLAN] Shen, N. and A. Zinin, "Point-to-point operation over LAN
in link-state routing protocols",
draft-ietf-isis-igp-p2p-over-lan-05.txt (work in progress).
[STUB] Retana, A., Nguyen, L., White, R., Zinin, A. and D.
McPherson, "OSPF Stub Router Advertisement", RFC 3137, June
2001.
[T3CAP] Vasseur, JP., Psenak, P., Yasukawa, S. and JL. Le Roux,
"OSPF MPLS Traffic Engineering Capabilities",
draft-vasseur-ospf-te-caps-00.txt (work in progress).
Authors' Addresses
Acee Lindem
Cisco Systems, Inc
7025 Kit Creek Road
Research Triangle Park, NC 27709
USA
EMail: acee@cisco.com
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Naiming Shen
BCN Networks, Inc
2975 San Ysidro Way
Santa Clara, CA 95051
USA
EMail: naiming@bcn-inc.net
Rahul Aggarwal
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
EMail: rahul@juniper.net
Scott Schaffer
BridgePort Networks
One Main Street, 7th Floor
Cambridge, MA 02142
USA
EMail: sschafferl@bridgeport-networks.com
Jean-Philippe Vasseur
Cisco Systems, Inc
300 Beaver Brook Road
Boxborough, MA 01719
USA
EMail: jpv@cisco.com
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Appendix A. Acknowledgments
The idea for this work grew out of a conversation with Andrew Partan
and we would like to thank him for his contribution. The authors
would like to thanks Peter Psenak for his review and helpful comments
early versions of the draft.
The RFC text was produced using Marshall Rose's xml2rfc tool.
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