Network Working Group JP. Vasur Request for Comments: 5029 S. Previdi Category: Standards Track Cisco Systems, Inc September 2007 Definition of an IS-IS Link Attribute Sub-TLV
Status of This Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for
improvements. Plea refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited. Abstract
This document defines a sub-TLV called "Link-attributes" carried
within the TLV 22 and ud to flood some link characteristics.
Table of Contents
1. Introduction (2)
1.1. Terminology (2)
2. Link-Attributes Sub-TLV Format (2)
3. Interoperability with Routers Not Supporting This Capability (3)
4. IANA Considerations (3)
5. Security Considerations (3)
6. Acknowledgements (3)
7. References (4)
7.1. Normative References (4)
7.2. Informative References (4)
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1. Introduction
[IS-IS] specifies the IS-IS protocol (ISO 10589) with extensions to
support IPv4 in [RFC1195]. A router advertis one or veral Link
State Protocol data units that are compod of variable length tuples called TLVs (Type-Length-Value).
[RFC3784] defines a t of new TLVs who aims are to add more
information about links characteristics, increa the range of IS-IS metrics, and optimize the encoding of IS-IS prefixes.
This document defines a new sub-TLV named "Link-attributes" carried
within the extended IS reachability TLV (type 22) specified in
[RFC3784].
1.1 Terminology
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 [RFC2119].
2. Link-Attributes Sub-TLV Format
The link-attribute sub-TLV is carried within the TLV 22 and has a
format identical to the sub-TLV format ud by the Traffic
Engineering Extensions for IS-IS ([RFC3784]): 1 octet of sub-type, 1 octet of length of the value field of the sub-TLV followed by the
value field -- in this ca, a 16 bit flags field.
百花齐放的近义词The Link-attribute sub-type is 19 and the link-attribute has a length of 2 octets.
This sub-TLV is OPTIONAL and MUST appear at most once for a single IS neighbor. If a received Link State Packet (LSP) contains more than
one Link-Attribute Sub-TLV, an implementation SHOULD decide to
consider only the first encountered instance.
The following bits are defined:
Local Protection Available (0x01). When t, this indicates that the link is protected by means of some local protection mechanism (e.g., [RFC4090]).
卵巢囊肿吃什么药Link excluded from local protection path (0x02). When t, this link SHOULD not be included in any computation of a repair path by any
other router in the routing area. The triggers for tting up this
bit are out of the scope of this document.
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3. Interoperability with Routers Not Supporting This Capability
A router not supporting the link-attribute sub-TLV will just silently ignore this sub-TLV.
4. IANA Considerations
IANA has assigned codepoint 19 for the link-attribute sub-TLV defined in this document and carried within TLV 22.
IANA has created a registry for bit values inside the link-attributes sub-TLV. The initial contents of this registry are as follows
Value Name Reference
----- ---- ---------
0x1 Local Protection Available [RFC5029]
0x2 Link Excluded from Local Protection [RFC5029]
Further values are to be allocated by the Standards Action process
defined in [RFC2434], with Early Allocation (defined in [RFC4020])
permitted.
5. Security Considerations
Any new curity issues raid by the procedures in this document
depend upon the opportunity for LSPs to be snooped and modified, the ea/difficulty of which has not been altered. As the LSPs may now
contain additional information regarding router capabilities, this
new information would also become available to an attacker.
Specifications bad on this mechanism need to describe the curity considerations around the disclosure and modification of their
information. Note that an integrity mechanism, such as one defined
in [RFC3567], should be applied if there is high risk resulting from the modification of capability information.欧阳报军
6. Acknowledgements
The authors would like to thank Mike Shand, Les Ginsberg, and Bill
Fenner for their uful comments.
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7. References
7.1. Normative References
[IS-IS] "Intermediate System to Intermediate System Intra-Domain
Routing Exchange Protocol for u in Conjunction with the Protocol for Providing the Connectionless-mode Network
Service (ISO 8473)", ISO 10589.
[RFC1195] Callon, R., "U of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, December 1990.
[RFC2119] Bradner, S., "Key words for u in RFCs to Indicate
澳大利亚景点
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,潭
October 1998.
[RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate
System (IS-IS) Extensions for Traffic Engineering (TE)",
RFC 3784, June 2004.
[RFC4020] Kompella, K. and A. Zinin, "Early IANA Allocation of
Standards Track Code Points", BCP 100, RFC 4020, February 2005.
7.2. Informative References
[RFC3567] Li, T. and R. Atkinson, "Intermediate System to
Intermediate System (IS-IS) Cryptographic Authentication", RFC 3567, July 2003.
红掌的寓意是什么[RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute色姑姑
Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May
2005.
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Authors’ Address
JP Vasur
环保英语Cisco Systems, Inc
1414 Massachutts Avenue
Boxborough, MA 01719
USA
EMail:
Stefano Previdi
Cisco Systems, Inc
Via Del Serafico 200
Roma 00142
Italy
EMail:
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