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:  [email protected]

  Naiming Shen
  Cisco Systems, Inc.
  EMail: [email protected]



































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