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Versions: (draft-jones-dime-extended-naptr) 00 01 02 03 04 05 06 07 08 09 RFC 6408

Individual Submission                                           M. Jones
Internet-Draft                                       Bridgewater Systems
Updates: 3588 (if approved)                                  J. Korhonen
Intended status: Standards Track                  Nokia Siemens Networks
Expires: July 2, 2010                                  December 29, 2009


                        Diameter Extended NAPTR
                   draft-ietf-dime-extended-naptr-00

Abstract

   This document describes an extended format for the NAPTR service
   fields used in dynamic Diameter agent discovery.  The extended format
   allows NAPTR queries to contain Diameter Application-Id information.

Requirements Language

   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 [RFC2119].

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   This Internet-Draft will expire on July 2, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the



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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   it for publication as an RFC or to translate it into languages other
   than English.




























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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Extended NAPTR Service Field  . . . . . . . . . . . . . . . . . 4
   4.  Extended NAPTR-based Diameter Peer Discovery  . . . . . . . . . 5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8









































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1.  Introduction

   The Diameter base protocol [RFC3588] specifies three mechanisms for
   the Diameter peer discovery.  One of these involves the Diameter
   implementation performing a NAPTR query [RFC3403] for a server in a
   particular realm.  These NAPTR records provide a mapping from a
   domain, to the SRV record [RFC2782] for contacting a server with the
   specific transport protocol in the NAPTR services field.

   Section 11.6 of RFC 3588 defines the following NAPTR service fields:

         Services Field               Protocol
         AAA+D2T                       TCP
         AAA+D2S                       SCTP

   However, foreseen network topologies require border AAA nodes that
   will be specialized by Diameter application and the NAPTR service
   field does not allow a Diameter implementation to determine the
   application supported by the AAA node.  Without this information, a
   Diameter implementation must connect and perform a capability
   negotiation with each candidate AAA node.  This document addresses
   this problem by specifying an extended NAPTR service field format
   that permits discovery of Diameter peers that support a specific
   Diameter application.


2.  Terminology

   The Diameter base protocol specification (Section 1.4 of RFC 3588)
   defines most of the terminology used in this document.


3.  Extended NAPTR Service Field

   The Extended NAPTR service field ABNF specification for the discovery
   of Diameter agents supporting a specific Diameter application is show
   below.














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         naptr-svc-field     = "AAA+D2" < protocol> [ *appln-list ]

         protocol            = "T" / "S"
                               ; "T" for TCP and "S" for SCTP.

         appln-list          = "+AP:" appln-id [ *( "," appln-id ) ]
                               ; Comma separated list of application
                               ; identifiers prefixed by "+AP:".

         appln-id            = *DIGIT
                               ; Application identifier expressed as a
                               ; decimal integer.

   For example, a NAPTR service field value of:

   'AAA+D2S+AP:6'

      Means that the Diameter node in the SRV record supports the
      Diameter Session Initiation Protocol (SIP) Application ('6') and
      SCTP as the transport protocol.

   'AAA+D2S+AP:6,1,5,4294967295'

      Means that the Diameter node in the SRV record supports the
      Diameter Session Initiation Protocol (SIP) Application ('6'),
      NASREQ Application ('1'), EAP Application ('5') and SCTP as the
      transport protocol.  The Diameter node also provides Relay
      functionality ('4294967295').

   The maximum length of the NAPTR service field is 256 octets including
   one octet length field (see Section 4.1 of RFC 3403 and Section 3.3
   of [RFC1035]).  The DNS administrator of some domain SHOULD also
   provision base RFC 3588 style NAPTR records in order to guarantee
   backwards compatibility with legacy RFC 3588 compliant Diameter
   peers.  If the DNS administrator provisions both extended NAPTR
   records as defined in this specification and legacy RFC 3588 NAPTR
   records, then the extended NAPTR records MUST have higher priority
   (e.g. lower order and/or preference values) than legacy NAPTR
   records.


4.  Extended NAPTR-based Diameter Peer Discovery

   The basic Diameter Peer Discover principles are described in Section
   5.2 of [RFC3588].  This specification extends the NAPTR query
   procedure in the Diameter peer discovery mechanism by allowing the
   querying node to determine which applications are supported by
   resolved Diameter peers.



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   The extended format NAPTR records provide a mapping from a domain, to
   the SRV record for contacting a server supporting a specific
   transport protocol and Diameter application.  The resource record
   will contain an empty regular expression and a replacement value,
   which is the SRV record for that particular transport protocol.  If
   the server supports multiple transport protocols, there will be
   multiple NAPTR records, each with a different Services Field value
   and potentially different list of supported Diameter applications.

   The assumption for this mechanism to work is that the DNS
   administrator of the queried domain has first provisioned the DNS
   with extended format NAPTR entries.  The steps below replace the
   NAPTR query procedure steps in Section 5.2 of [RFC3588].

   a. The Diameter implementation performs a NAPTR query for a server in
      a particular realm.  The Diameter implementation has to know in
      advance which realm to look for a Diameter agent in and which
      Application Identifier it is interested in.  The realm could be
      deduced, for example, from the 'realm' in a NAI that a Diameter
      implementation needed to perform a Diameter operation on.

   b. If the returned NAPTR service fields contain entries formatted as
      "AAA+D2X+AP:Y" where "X" indicates the transport protocol and "Y"
      is a comma-separated list of Application Identifiers, the target
      realm supports the extended format for NAPTR-based Diameter peer
      discovery defined in this document.

         If "X" matches a transport protocol supported by the client and
         "Y" contains the required Application Identifier, the client
         resolves the "replacement" field entry to a target host using
         the lookup method appropriate for the "flags" field.

         If "X" does not match a transport protocol supported by the
         client or "Y" does not contain the required Application
         Identifier, the peer discovery is abandoned.

   c. If the returned NAPTR service fields contain entries formatted as
      "AAA+D2X" where "X" indicates the transport protocol, the target
      realm supports the NAPTR-based Diameter peer discovery defined in
      [RFC3588].

         If "X" matches a transport protocol supported by the client,
         the client resolves the "replacement" field entry to a target
         host using the lookup method appropriate for the "flags" field.







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         If "X" does not match a transport protocol supported by the
         client, the peer discovery is abandoned.

   d. If the target realm does not support NAPTR-based Diameter peer
      discovery, the client proceeds with the next peer discovery
      mechanism described in Section 5.2 of [RFC3588].


5.  IANA Considerations

   Section 11.6 of [RFC3588] defines a IANA registry for the NAPTR
   Services Field entries.  Although this document does not define a new
   transport protocol, it is proposed to add the following entries to
   the existing registry to reflect the extended format of the NAPTR
   Services Field:

         Services Field               Protocol
         AAA+D2T+AP:x                  TCP
         AAA+D2S+AP:x                  SCTP

   Editor's Note: IANA is currently missing the registry for the NAPTR
   Service Fields defined in [RFC3588].  This oversight will need to be
   resolved for this document to proceed.


6.  Security Considerations

   This document specifies an enhancement to the NAPTR service field
   format defined in the Diameter base protocol and the same security
   considerations described in RFC 3588 are applicable to this document.
   No further extensions are required beyond the security mechanisms
   offered by RFC 3588.  However, a malicious host doing NAPTR queries
   learns applications supported by Diameter agents in a certain realm
   faster, which might help the malicious host to scan potential targets
   for an attack more efficiently when some applications have known
   vulnerabilities.


7.  Normative References

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

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

   [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,



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              February 2000.

   [RFC3403]  Mealling, M., "Dynamic Delegation Discovery System (DDDS)
              Part Three: The Domain Name System (DNS) Database",
              RFC 3403, October 2002.

   [RFC3588]  Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
              Arkko, "Diameter Base Protocol", RFC 3588, September 2003.


Authors' Addresses

   Mark Jones
   Bridgewater Systems
   303 Terry Fox Drive, Suite 500
   Ottawa, Ontario  K2K 3J1
   Canada

   Email: mark.jones@bridgewatersystems.com


   Jouni Korhonen
   Nokia Siemens Networks
   Linnoitustie 6
   FI-02600 Espoo
   FINLAND

   Email: jouni.nospam@gmail.com























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