





Network Working Group                                       D. McPherson
Request for Comments: 5301                                Arbor Networks
Obsoletes: 2763                                                  N. Shen
Category: Standards Track                                  Cisco Systems
                                                            October 2008


             Dynamic Hostname Exchange Mechanism for IS-IS

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please 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

   RFC 2763 defined a simple and dynamic mechanism for routers running
   IS-IS to learn about symbolic hostnames.  RFC 2763 defined a new TLV
   that allows the IS-IS routers to flood their name-to-systemID mapping
   information across the IS-IS network.

   This document obsoletes RFC 2763.  This document moves the capability
   provided by RFC 2763 to the Standards Track.

Table of Contents

   1. Introduction ....................................................2
      1.1. Specification of Requirements ..............................2
   2. Possible Solutions ..............................................2
   3. Dynamic Hostname TLV ............................................3
   4. Implementation ..................................................4
   5. Security Considerations .........................................4
   6. Acknowledgments .................................................4
   7. IANA Considerations .............................................4
   8. Informative References ..........................................4













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1.  Introduction

   IS-IS uses a variable 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 system IDs
   and Link State Protocol Data Unit (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 system IDs and to find system IDs 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 statically-configured table with
   mappings between router names and system IDs.  These tables need to
   contain the names and system IDs of all routers in the network, and
   must be modified each time an addition, deletion, or change occurs.

   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 provide a third solution,
   which in wide-scale implementation and deployment has proven to be
   easier and more manageable than static mapping or DNS schemes.

1.1.  Specification of Requirements

   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.  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, on every 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 system ID of one router, or adding a new router will affect the
   configurations of all the other routers on the network.  This will
   make it very likely that those static tables are outdated.





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   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 Connection Network Service (CLNS)
   Network Service Access Points (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 PDUs.  This document defines a new TLV that
   allows the IS-IS routers to include the name-to-systemID mapping data
   in their LSPs.  This will allow simple and reliable transport of name
   mapping information across the IS-IS network.

3.  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-pseudonode 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 it
   can be any string operators want to use for the router.  The use of
   FQDN or a subset of it is strongly recommended.  The content of this
   value is a domain name, see [RFC2181].  The string is not null-
   terminated.  The system ID of this router can be derived from the LSP
   identifier.

   If this TLV is present in a pseudonode LSP, then it SHOULD NOT be
   interpreted as the DNS hostname of the router.

   The Value field is encoded in 7-bit ASCII.  If a user-interface for
   configuring or displaying this field permits Unicode characters, that
   user-interface is responsible for applying the ToASCII and/or
   ToUnicode algorithm as described in [RFC3490] to achieve the correct
   format for transmission or display.









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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 system ID in its hostname
   mapping table for the IS-IS network.

   A router may also optionally insert this TLV in its pseudonode LSP
   for the association of a symbolic name to a local LAN.

   If a system receives a mapping for a name or system ID that is
   different from the mapping in the local cache, an implementation
   SHOULD replace the existing mapping with the latest information.

5.  Security Considerations

   Since the name-to-systemID mapping relies on information provided by
   the routers themselves, a misconfigured or compromised router can
   inject false mapping information.  Thus, this information needs to be
   treated with suspicion when, for example, doing diagnostics about a
   suspected security incident.

   This document raises no other new security issues for IS-IS.
   Security issues with IS-IS are discussed in [RFC5304].

6.  Acknowledgments

   The original efforts and corresponding acknowledgements provided in
   [RFC2763] have enabled this work.  In particular, we'd like to
   acknowledge Henk Smit as an author of that document.

7.  IANA Considerations

   This document specifies TLV 137, "Dynamic Name".  This TLV has
   already been allocated and reserved [RFC2763].  As such, no new
   actions are required on the part of IANA.

8.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, July 1997.

   [RFC2763]  Shen, N. and H. Smit, "Dynamic Hostname Exchange Mechanism
              for IS-IS", RFC 2763, February 2000.



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   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
              "Internationalizing Domain Names in Applications (IDNA)",
              RFC 3490, March 2003.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, October 2008.

Authors' Addresses

   Danny McPherson
   Arbor Networks, Inc.
   EMail:  danny@arbor.net

   Naiming Shen
   Cisco Systems, Inc.
   EMail: naiming@cisco.com



































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