rfc1706.txt

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Network Working Group                                         B. Manning
Request for Comments: 1706                                           ISI
Obsoletes: 1637, 1348                                         R. Colella
Category: Informational                                             NIST
                                                            October 1994


                       DNS NSAP Resource Records


Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   OSI lower layer protocols, comprising the connectionless network
   protocol (CLNP) and supporting routing protocols, are deployed in
   some parts of the global Internet.  Maintenance and debugging of CLNP
   connectivity is greatly aided by support in the Domain Name System
   (DNS) for mapping between names and NSAP addresses.

   This document defines the format of one new Resource Record (RR) for
   the DNS for domain name-to-NSAP mapping. The RR may be used with any
   NSAP address format.

   NSAP-to-name translation is accomplished through use of the PTR RR
   (see STD 13, RFC 1035 for a description of the PTR RR). This paper
   describes how PTR RRs are used to support this translation.

   This document obsoletes RFC 1348 and RFC 1637.


















Manning & Colella                                               [Page 1]

RFC 1706                      DNS NSAP RRs                  October 1994


1.  Introduction

   OSI lower layer protocols, comprising the connectionless network
   protocol (CLNP) [5] and supporting routing protocols, are deployed in
   some parts of the global Internet.  Maintenance and debugging of CLNP
   connectivity is greatly aided by support in the Domain Name System
   (DNS) [7] [8] for mapping between names and NSAP (network service
   access point) addresses [6] [Note: NSAP and NSAP address are used
   interchangeably throughout this memo].

   This document defines the format of one new Resource Record (RR) for
   the DNS for domain name-to-NSAP mapping. The RR may be used with any
   NSAP address format.

   NSAP-to-name translation is accomplished through use of the PTR RR
   (see RFC 1035 for a description of the PTR RR). This paper describes
   how PTR RRs are used to support this translation.

   This memo assumes that the reader is familiar with the DNS. Some
   familiarity with NSAPs is useful; see [1] or Annex A of [6] for
   additional information.

2.  Background

   The reason for defining DNS mappings for NSAPs is to support the
   existing CLNP deployment in the Internet.  Debugging with CLNP ping
   and traceroute has become more difficult with only numeric NSAPs as
   the scale of deployment has increased. Current debugging is supported
   by maintaining and exchanging a configuration file with name/NSAP
   mappings similar in function to hosts.txt. This suffers from the lack
   of a central coordinator for this file and also from the perspective
   of scaling.  The former describes the most serious short-term
   problem. Scaling of a hosts.txt-like solution has well-known long-
   term scaling difficiencies.

3.  Scope

   The methods defined in this paper are applicable to all NSAP formats.

   As a point of reference, there is a distinction between registration
   and publication of addresses. For IP addresses, the IANA is the root
   registration authority and the DNS a publication method. For NSAPs,
   Annex A of the network service definition, ISO8348 [6], describes the
   root registration authority and this memo defines how the DNS is used
   as a publication method.






Manning & Colella                                               [Page 2]

RFC 1706                      DNS NSAP RRs                  October 1994


4.  Structure of NSAPs

   NSAPs are hierarchically structured to allow distributed
   administration and efficient routing. Distributed administration
   permits subdelegated addressing authorities to, as allowed by the
   delegator, further structure the portion of the NSAP space under
   their delegated control.  Accomodating this distributed authority
   requires that there be little or no a priori knowledge of the
   structure of NSAPs built into DNS resolvers and servers.

   For the purposes of this memo, NSAPs can be thought of as a tree of
   identifiers. The root of the tree is ISO8348 [6], and has as its
   immediately registered subordinates the one-octet Authority and
   Format Identifiers (AFIs) defined there. The size of subsequently-
   defined fields depends on which branch of the tree is taken. The
   depth of the tree varies according to the authority responsible for
   defining subsequent fields.

   An example is the authority under which U.S. GOSIP defines NSAPs [2].
   Under the AFI of 47, NIST (National Institute of Standards and
   Technology) obtained a value of 0005 (the AFI of 47 defines the next
   field as being two octets consisting of four BCD digits from the
   International Code Designator space [3]). NIST defined the subsequent
   fields in [2], as shown in Figure 1. The field immediately following
   0005 is a format identifier for the rest of the U.S. GOSIP NSAP
   structure, with a hex value of 80. Following this is the three-octet
   field, values for which are allocated to network operators; the
   registration authority for this field is delegated to GSA (General
   Services Administration).

   The last octet of the NSAP is the NSelector (NSel). In practice, the
   NSAP minus the NSel identifies the CLNP protocol machine on a given
   system, and the NSel identifies the CLNP user. Since there can be
   more than one CLNP user (meaning multiple NSel values for a given
   "base" NSAP), the representation of the NSAP should be CLNP-user
   independent. To achieve this, an NSel value of zero shall be used
   with all NSAP values stored in the DNS. An NSAP with NSel=0
   identifies the network layer itself. It is left to the application
   retrieving the NSAP to determine the appropriate value to use in that
   instance of communication.

   When CLNP is used to support TCP and UDP services, the NSel value
   used is the appropriate IP PROTO value as registered with the IANA.
   For "standard" OSI, the selection of NSel values is left as a matter
   of local administration. Administrators of systems that support the
   OSI transport protocol [4] in addition to TCP/UDP must select NSels
   for use by OSI Transport that do not conflict with the IP PROTO
   values.



Manning & Colella                                               [Page 3]

RFC 1706                      DNS NSAP RRs                  October 1994


              |--------------|
              | <-- IDP -->  |
              |--------------|-------------------------------------|
              | AFI |  IDI   |            <-- DSP -->              |
              |-----|--------|-------------------------------------|
              | 47  |  0005  | DFI | AA |Rsvd | RD |Area | ID |Sel |
              |-----|--------|-----|----|-----|----|-----|----|----|
       octets |  1  |   2    |  1  | 3  |  2  | 2  |  2  | 6  | 1  |
              |-----|--------|-----|----|-----|----|-----|----|----|

                    IDP    Initial Domain Part
                    AFI    Authority and Format Identifier
                    IDI    Initial Domain Identifier
                    DSP    Domain Specific Part
                    DFI    DSP Format Identifier
                    AA     Administrative Authority
                    Rsvd   Reserved
                    RD     Routing Domain Identifier
                    Area   Area Identifier
                    ID     System Identifier
                    SEL    NSAP Selector

                  Figure 1: GOSIP Version 2 NSAP structure.


   In the NSAP RRs in Master Files and in the printed text in this memo,
   NSAPs are often represented as a string of "."-separated hex values.
   The values correspond to convenient divisions of the NSAP to make it
   more readable. For example, the "."-separated fields might correspond
   to the NSAP fields as defined by the appropriate authority (RARE,
   U.S. GOSIP, ANSI, etc.). The use of this notation is strictly for
   readability. The "."s do not appear in DNS packets and DNS servers
   can ignore them when reading Master Files. For example, a printable
   representation of the first four fields of a U.S. GOSIP NSAP might
   look like

                             47.0005.80.005a00

   and a full U.S. GOSIP NSAP might appear as

             47.0005.80.005a00.0000.1000.0020.00800a123456.00.

   Other NSAP formats have different lengths and different
   administratively defined field widths to accomodate different
   requirements. For more information on NSAP formats in use see RFC
   1629 [1].





Manning & Colella                                               [Page 4]

RFC 1706                      DNS NSAP RRs                  October 1994


5.  The NSAP RR

   The NSAP RR is defined with mnemonic "NSAP" and TYPE code 22
   (decimal) and is used to map from domain names to NSAPs. Name-to-NSAP
   mapping in the DNS using the NSAP RR operates analogously to IP
   address lookup. A query is generated by the resolver requesting an
   NSAP RR for a provided domain name.

   NSAP RRs conform to the top level RR format and semantics as defined
   in Section 3.2.1 of RFC 1035.

                                            1  1  1  1  1  1
              0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |                                               |
           /                                               /
           /                        NAME                   /
           |                                               |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |                    TYPE = NSAP                |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |                    CLASS = IN                 |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |                        TTL                    |
           |                                               |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |                      RDLENGTH                 |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           /                       RDATA                   /
           /                                               /
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

   where:

   *  NAME: an owner name, i.e., the name of the node to which this
      resource record pertains.

   *  TYPE: two octets containing the NSAP RR TYPE code of 22 (decimal).

   *  CLASS: two octets containing the RR IN CLASS code of 1.

   *  TTL: a 32 bit signed integer that specifies the time interval in
      seconds that the resource record may be cached before the source
      of the information should again be consulted. Zero values are
      interpreted to mean that the RR can only be used for the
      transaction in progress, and should not be cached. For example,
      SOA records are always distributed with a zero TTL to prohibit
      caching. Zero values can also be used for extremely volatile data.



Manning & Colella                                               [Page 5]