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Network Working Group                                           N. ShenRequest for Comments: 2763                                Siara SystemsCategory: Informational                                         H. Smit                                                          Cisco Systems                                                          February 2000Dynamic Hostname Exchange Mechanismfor IS-ISStatus of this Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2000).  All Rights Reserved.Abstract   Currently, there does not exist a simple and dynamic mechanism for   routers running IS-IS to learn about symbolic hostnames. This   document defines a new TLV which allows the IS-IS routers to flood   their name to system ID mapping information across the IS-IS network.1. Introduction   IS-IS uses a 1-8 byte system ID (normally 6 bytes) to represent a   node in the network.  For management and operation reasons, network   operators need to check the status of IS-IS adjacencies, entries in   the routing table and the content of the IS-IS link state database.   It is obvious that, when looking at diagnostics information,   hexadecimal representations of systemIDs and LSP identifiers are less   clear than symbolic names.   One way to overcome this problem is to define a name-to-systemID   mapping on a router. This mapping can be used bidirectionally. E.g.,   to find symbolic names for systemIDs, and to find systemIDs for   symbolic names. One way to build this table of mappings is by static   definitions. Among network administrators who use IS-IS as their IGP   it is current practice to define such static mappings.   Thus every router has to maintain a table with mappings between   router names and systemIDs. These tables need to contain all names   and systemIDs of all routers in the network.Shen & Smit                  Informational                      [Page 1]

RFC 2763                    Dynamic Hostname               February 2000   There are several ways one could build such a table. One is via   static configurations. Another scheme that could be implemented is   via DNS lookups. In this document we propose a third solution. We   hope the proposed solution is easier and more manageable than static   mapping or DNS schemes.2. Possible solutions   The obvious drawback of static configuration of mappings is the issue   of scalability and maintainability. The network operators have to   maintain the name tables. They have to maintain an entry in the table   for every router in the network. They have to maintain this table on   each router in the network. The effort to create and maintain these   static tables grows with the total number of routers on the network.   Changing the name or systemID of one router, or adding one new router   introduced will affect the configurations of all the other routers on   the network. This will make it very likely that those static tables   are outdated.   Having one table that can be updated in a centralized place would be   helpful. One could imagine using the DNS system for this. A drawback   is that during the time of network problems, the response time of DNS   services might not be satisfactory or the DNS services might not even   be available. Another possible drawback might be the added complexity   of DNS. Also, some DNS implementations might not support A and PTR   records for CLNS NSAPs.   A third way to build dynamic mappings would be to use the transport   mechanism of the routing protocol itself to advertise symbolic names   in IS-IS link-state PDU. This document defines a new TLV which allows   the IS-IS routers to include the name to systemID mapping information   in their LSPs. This will allow simple and reliable transport of name   mapping information across the IS-IS network.3. The Dynamic Hostname TLV   The Dynamic hostname TLV is defined here as TLV type 137.         LENGTH - total length of the value field.         VALUE - a string of 1 to 255 bytes.   The Dynamic hostname TLV is optional. This TLV may be present in any   fragment of a non-pseudo node LSP. The value field identifies the   symbolic name of the router originating the LSP. This symbolic name   can be the FQDN for the router, it can be a subset of the FQDN or any   string operators want to use for the router. The use of FQDN or aShen & Smit                  Informational                      [Page 2]

RFC 2763                    Dynamic Hostname               February 2000   subset of it is strongly recommended. The content of this value is a   domain name, seeRFC 2181. The string is not null-terminated. The   systemID of this router can be derived from the LSP identifier.   If this TLV is present in a pseudo node LSP, then it should not be   interpreted as the DNS hostname of the router.4. Implementation   The Dynamic Hostname TLV is optional. When originating an LSP, a   router may decide to include this TLV in its LSP. Upon receipt of an   LSP with the dynamic hostname TLV, a router may decide to ignore this   TLV, or to install the symbolic name and systemID in its hostname   mapping table.   A router may also optionally insert this TLV in it's pseudo node LSP   for the association of a symbolic name to a local LAN.5. Security Considerations   This document raises no new security issues for IS-IS. However, it is   encouraged to use authentications for IS-IS routing protocol.  The   authentication mechanism for IS-IS protocol is specified in [1] and   it is being enhanced within IETF in [2].6. Acknowledgments   The authors would like to thank Enke Chen and Yakov Rekhter for their   comments on this work.7. References   [1] ISO, "Intermediate system to Intermediate system routing       information exchange protocol for use in conjunction with the       Protocol for providing the Connectionless-mode Network Service       (ISO 8473)," ISO/IEC 10589:1992.   [2] Li, T.,"IS-IS HMAC-MD5 Authentication", Work in Progress.Shen & Smit                  Informational                      [Page 3]

RFC 2763                    Dynamic Hostname               February 20008. Authors' Addresses   Naiming Shen   Siara Systems, Inc.   1195 Borregas Avenue   Sunnyvale, CA, 94089   EMail: naiming@siara.com   Henk Smit   Cisco Systems, Inc.   170 Tasman Drive   San Jose, CA, 95134   EMail: hsmit@cisco.comShen & Smit                  Informational                      [Page 4]

RFC 2763                    Dynamic Hostname               February 20009. Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Shen & Smit                  Informational                      [Page 5]