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Network Working Group                                       D. McPhersonRequest for Comments: 5301                                Arbor NetworksObsoletes:2763                                                  N. ShenCategory: Standards Track                                  Cisco Systems                                                            October 2008Dynamic Hostname Exchange Mechanism for IS-ISStatus 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.AbstractRFC 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 obsoletesRFC 2763.  This document moves the capability   provided byRFC 2763 to the Standards Track.Table of Contents1. Introduction ....................................................21.1. Specification of Requirements ..............................22. Possible Solutions ..............................................23. Dynamic Hostname TLV ............................................34. Implementation ..................................................45. Security Considerations .........................................46. Acknowledgments .................................................47. IANA Considerations .............................................48. Informative References ..........................................4McPherson & Shen            Standards Track                     [Page 1]

RFC 5301                    Dynamic Hostname                October 20081.  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 inRFC 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.McPherson & Shen            Standards Track                     [Page 2]

RFC 5301                    Dynamic Hostname                October 2008   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.McPherson & Shen            Standards Track                     [Page 3]

RFC 5301                    Dynamic Hostname                October 20084.  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.McPherson & Shen            Standards Track                     [Page 4]

RFC 5301                    Dynamic Hostname                October 2008   [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.comMcPherson & Shen            Standards Track                     [Page 5]

RFC 5301                    Dynamic Hostname                October 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.McPherson & Shen            Standards Track                     [Page 6]