Network Working Group Acee Lindem
Internet Draft Naiming Shen
Expiration Date: April 2004 Redback Networks
Rahul Aggarwal
Juniper Networks
Scott Shaffer
Level 3 Communications
JP Vasseur
Cisco Systems, Inc
Extensions to OSPF for Advertising Optional Router Capabilities
draft-ietf-ospf-cap-01.txt
Status of this Memo
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Abstract
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.
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 RFC-2119 [3].
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Internet Draft draft-ietf-ospf-cap-01.txt October 2003
1. Motivation
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 [7, 8] 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 [1]. 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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Internet Draft draft-ietf-ospf-cap-01.txt October 2003
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 [2].
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 -+
| ... |
Figure 2. OSPF Router Information LSA
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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 [4]. The LSA payload consists of one or
more nested Type/Length/Value (TLV) triplets. The format of
each TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3. TLV Format
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 a RI opaque LSA is
the Router Capabilities TLV. A router advertising a 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:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4. OSPF Router Capabilities TLV
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Internet Draft draft-ietf-ospf-cap-01.txt October 2003
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 [5]
5 OSPF graceful restart helper [5]
6 Stub Router support [6]
7 Traffic Engineering support [4]
8 OSPF point-to-point over LAN [9]
9 OSPF Path Computation Server discovery [7, 8]
10-31 Future assignments
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2.3 Flooding Scope of the Router Information LSA
The flooding scope of the Router Information opaque LSA is determined
by the LSA type. A type 9 (link-scope), type 10 (area-scoped), or a
type 11 (AS-scoped) opaque LSA may be used. 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 values in advertised NSSA/stub area type 10
LSA(s) and its AS scoped type 11 opaque LSA. The choice of
flooding scope is made by the advertising router and is a matter of
local policy. The originating router MAY advertise multiple Router
Information LSAs as long as the flooding scope differs. TLV flooding
scope rules will be specified on a per-TLV basis.
3. Security Consideration
This memo does not create any new security issues for the OSPF
protocol. Security considerations for the base OSPF protocol are
covered in [1].
4. 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.
Funding for the RFC Editor function is currently provided by the
Internet Society.
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Internet Draft draft-ietf-ospf-cap-01.txt October 2003
5. 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.
6. References
Normative References
[1] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July
1998.
[2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Level", BCP 14, RFC 2119, March 1997.
Informative References
[4] Katz, D., D. Yeung and K. Kompella, "Traffic Engineering
Extensions to OSPF", RFC 3630, September 2003.
[5] Moy, J., "OSPF Graceful OSPF Restart", Internet Draft, work in
progress.
[6] Retana, A., et al, "OSPF Stub Router Advertisement",
RFC 3137, June 2001.
[7] Vasseur, Psenak, "Traffic Engineering Capability TLV for OSPF",
Internet Draft, work in progress.
[8] Vasseur et al, "RSVP Path computation request and reply
messages", draft-vasseur-mpls-computation-rsvp-te-03.txt,
work in progress
[9] N. Shen, et al, "Point-to-point operation over LAN in
link-state-routing protocols", Internet Draft, work in
progress.
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9. Author Information
Acee Lindem
Redback Networks
350 Holger Way
San Jose, CA 95134
e-mail: acee@redback.com
Naiming Shen
Redback Networks
350 Holger Way
San Jose, CA 95134
e-mail: naiming@redback.com
Rahul Aggarwal
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089 USA
e-mail: rahul@juniper.net
Scott Shaffer
Level 3 Communications
e-mail: scott.shaffer@level3.com
JP Vasseur
Cisco Systems, Inc.
300 Apollo Drive
Chelmsford, MA 01824
e-mail: jpv@cisco.com
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