Network Working Group Acee Lindem (Redback Networks)
Internet Draft Naiming Shen (Redback Networks)
Expiration Date: November 2002 Rahul Aggarwal (Redback Networks)
Scott Shaffer (Genuity, Inc.)
Extensions to IS-IS and OSPF for Advertising
Optional Router Capabilities
draft-raggarwa-igp-cap-00.txt
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026, except that the right to
produce derivative works is not granted.
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2. Abstract
It is useful for routers in a IGP domain to know of the capabilities
of their IGP neighbors and/or other routers in the domain. This draft
proposes extensions to IS-IS and OSPF for advertising optional router
capabilities. We define an optional Router Capability TLV for IS-IS,
while for OSPF we define an optional Router Capability Opaque LSA.
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3. Motivation
It is useful for routers in a IGP domain to know of the capabilities
of their IGP neighbors and/or other routers in the domain. A domain
refers to the IGP link state packet flooding domain. Hence for OSPF a
domain implies the same area, while for IS-IS it implies the same
level. It gives operators a domain wide view of IGP capabilities on
different routers in the network. This can be fairly useful for
network management and troubleshooting. Here IGP domain refers to
the IGP link state packet flooding domain,
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 mis-configuration
or an incorrect software version. Hence this capability information
can be used to track problems resulting from mis-configuration or an
incorrect software version.
There is no existing mechanism in IS-IS to advertise optional router
capabilities. On the other hand OSPF uses the options field in the
hello packet to advertise optional router capabilities [2]. However
this attribute is not extensible for advertising optional
capabilities such as hitless graceful restart. We propose extensions
to IS-IS and OSPF for advertising these optional capabilities. For
current IS-IS and OSPF capabilities this advertisement will be used
primarily for informational purposes. Conceivably, future IS-IS and
OSPF capability advertisements could be used for other purposes.
4. IS-IS Router Capability TLV
IS-IS routers will optionally advertise their optional capabilities
in an IS-IS Router Capability TLV of type 242. This optional TLV is
included in the IS-IS LSP packet [6]. It SHOULD reside in fragment
zero of the LSPs of each level. If a router does not advertise this
TLV in any of its LSP packets, it does not imply that the router does
not support one or more of the defined capabilities. If this TLV is
included in a LSP, the router SHOULD set all the defined bits
corresponding to the capabilities which the software supports, unless
they are explicitly configured off.
draft-raggarwa-igp-cap-00.txt [Page 2]
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The following figure depicts the format of the IS-IS Router
Capability TLV.
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... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type A 8 bit field set to 242.
Length A 8 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.
4.1 Reserved IS-IS Router Capability Bits
We have assigned some pre-determined bits to the first capability
flag.
Bit Capabilities
0-3 Reserved
4 IS-IS hitless graceful restart capable [9]
5 IS-IS and BGP blackhole avoidance capable [11]
6 IS-IS wide metric processing capable [8]
7 IS-IS hmac-md5 authentication capable [10]
8 IS-IS Traffic Engineering support [8]
9 IS-IS point-to-point over LAN [12]
10-31 For future assignments
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5. OSPF Router Information LSA
OSPF routers will optionally advertise their optional capabilities
in an area-scoped Opaque-LSA [1]. 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 current OSPF capabilities,
the advertisement will be used solely for information purposes.
Conceivably, future OSPF capabilities could require other capability
LSA advertisement. The LSA is area-scoped to be consistent with the
scope of the OSPF router LSA [2]. The Router Information LSA will
be originated at startup and re-originated when router capabilities
change or when periodically refreshed.
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 | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- TLVs -+
| ... |
The format of the TLVs within the body of a Router Information LSA is
the same as the TLV format used by the Traffic Engineering Extensions
to OSPF [3]. The TLV header consists of a 16-bit Type field and a
16-bit length field, and is followed by zero or more bytes of value.
The length field indicates the length of the value portion in bytes.
The value portion is padded to four-octet alignment, but the padding
is not included in the length field. 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.
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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... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1 OSPF Router Capability TLV
Initially, only a single TLV may appear in the body of a Router
Information LSA. This is the Router Capability TLV. It MUST be
included. A router advertising an optional Router Information LSA
SHOULD set defined its corresponding to the supported optional
capabilities, unless they are explicitly configured off, in the
Router Capability TLV.
The format of the Router Capability 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
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5.2 Reserved OSPF Router Capability Bits
We have assigned some pre-determined bits to the first capability
flag.
Bit Capabilities
0-3 Reserved
4 Hitless graceful restart capable [4]
5 OSPF hitless graceful restart helper [4]
6 Stub Router support [5]
7 Traffic Engineering support [3]
8 OSPF point-to-point over LAN [12]
8-31 Future assignments
6. Security Consideration
This document does not introduce new security issues. The security
considerations pertaining to the original IS-IS and OSPF protocols
remain relevant.
7. Acknowledgments
The idea for this work grew out of a conversation with Andrew Partan
and we would like to thank him for his contribution.
8. References
[1] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July
1998.
[2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[3] Katz, D., D. Yeung and K. Kompella, "Traffic Engineering
Extensions to OSPF", Internet Draft, work in progress.
[4] Moy, J., "OSPF Hitless OSPF Restart", Internet Draft, work in
progress.
[5] Retana, A., et al, "OSPF Stub Router Advertisement",
RFC 3137, June 2001.
[6] Callon, R., "OSI IS-IS for IP and Dual Environment," RFC 1195,
December 1990.
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[7] ISO, "Intermediate system to Intermediate system routeing
information exchange protocol for use in conjunction with the
Protocol for providing the Connectionless-mode Network
Service (ISO 8473)," ISO/IEC 10589:1992.
[8] Li, T. et al, "IS-IS Extensions for Traffic Engineering",
Internet Draft, work in Progress.
[9] Shand, M., "Restart Signaling for IS-IS", Internet Draft, work
in Progress.
[10] Li, T., "IS-IS Cryptographic Authentication", Internet Draft,
work in progress.
[11] McPherson, D., "IS-IS Transient Blackhole Avoidance", Internet
Draft, work in progress.
[12] N. Shen, et al, "Point-to-point operation over LAN in
link-state-routing protocols", Internet Draft, work in
progress.
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
Redback Networks
350 Holger Way
San Jose, CA 95134
e-mail: rahul@redback.com
Scott Shaffer
Genuity, Inc.
3 Van de Graaff Drive
PO Box 3073
Burlington, MA 01803
e-mail: sshaffer@genuity.com
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