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Network Working Group B. Manning (Rice University)
INTERNET DRAFT R. Colella (NIST)
May 7, 1993
DNS NSAP Resource Records
Status of This Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas, and
its Working Groups. Note that other groups may also distribute working
documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months.
Internet-Drafts may be updated, replaced, or obsoleted by other
documents at any time. It is not appropriate to use Internet-Drafts as
reference material or to cite them other than as a "working draft" or
"work in progress."
To learn the status of any Internet-Draft, please check the 1id-
abstract.txt listing contained in the Internet-Drafts Shadow Directories
on nic.ddn.mil, nnsc.nsf.net, nic.nordu.net, ftp.nisc.sri.com, or
munnari.oz.au.
It is intended that this document will be submitted to the IESG for
consideration as a standards document. Distribution of this document is
unlimited.
Abstract
The Internet is moving towards the deployment of an OSI lower layers
infrastructure. This infrastructure comprises the connectionless network
protocol (CLNP) and supporting routing protocols. Also required as part
of this infrastructure is support in the Domain Name System (DNS) for
mapping between names and NSAP addresses.
This document defines the format of two new Resource Records (RRs) for
the DNS, building upon earlier work in RFC 1348. This format may be used
with any NSAP address format.
Expiration Date November 7, 1993 [Page 1]
INTERNET-DRAFT DNS NSAP Resource Records May 7, 1993
1 Introduction
The Internet is moving towards the deployment of an OSI lower layers
infrastructure. This infrastructure comprises the connectionless network
protocol (CLNP) [ISO86b] and supporting routing protocols. Also required
as part of this infrastructure is support in the Domain Name System
(DNS) [Moc87a , Moc87b] for mapping between DNS names and OSI Network
Service Access Point (NSAP) addresses [ISO88] [Note: NSAP and NSAP
address are used interchangeably throughout this memo].
This document defines the format of two new Resource Records (RRs) for
the DNS, building upon earlier work in RFC 1348. This format may be used
with any NSAP address format.
This memo assumes that the reader is familiar with the DNS. Some
familiarity with NSAPs is useful; see [CGC91] or [ISO88] for additional
information.
2 Background
The reason for defining DNS mappings for NSAPs is to support CLNP
in the Internet. Debugging with CLNP ping and traceroute is becoming
more difficult with only numeric NSAPs as the scale of deployment
increases. 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 is the most
serious short-term problem. Scaling of a hosts.txt-like solution has
well-known long-term scaling difficiencies.
A second reason for this work is the proposal to use CLNP as a re-
placement for IP: "TCP and UDP with Bigger Addresses (TUBA), A Simple
Proposal for Internet Addressing and Routing" [Cal92]. Should this pro-
posal be selected, the DNS must be capable of supporting CLNP addresses.
3 Scope
The RRs defined in this paper support all known NSAP formats. This
includes support for the notion of a custom-defined NSAP format based on
an AFI obtained by the IAB for use in the Internet.
B. Manning/R. Colella [Page 2]
INTERNET-DRAFT DNS NSAP Resource Records May 7, 1993
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,
addendum two of the network service definition, ISO8348/Ad2 [ISO88],
is the root registration authority and this memo defines how the DNS
is used as a publication method.
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.
Accommodation of this distributed authority requires flexibility in the
DNS inverse mapping of NSAPs to names, allowing sub-authorities to
represent the substructure they define, if any, in the DNS as well as
the NSAP values themselves.
While all NSAP structures currently known to be in use in the Internet
have fixed field sizes (e.g., [CGC91, Bry92]), some NSAP formats defined
in ISO8348/Ad2 define one of the fields as variable-sized. These formats
are still parsable, since the total NSAP length is known and there is,
at most, one variable-sized field. These formats are accommodated in this
document, even though there is no current requirement.
For the purposes of this memo, NSAPs can be thought of as a tree of
identifiers. The root of the tree is defined in ISO8348/Ad2 [ISO88],
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 US GOSIP defines NSAPs [GOSIP].
Under the AFI of 47, NIST (National Institute of Standards and Technol-
ogy) 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 [ISO84]). NIST defined the subsequent fields in
[GOSIP], as shown in Figure 1. The field immediately following 0005 is
a format identifier for the rest of the US GOSIP NSAP structure, with
a hex value of 80. Following this is the three-octet field, values for
B. Manning/R. Colella [Page 3]
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which are allocated to network operators; the registration authority for
this field is delegated to GSA (General Services Administration).
_______________
|_<--_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.
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 will 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.
In the event that CLNP is used to support TCP and UDP services, the
NSel value used will be 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 [ISO86a] in addition to TCP/UDP
will select NSels for use by OSI Transport that do not conflict with
the IP PROTO
values.
In Master Files and in the printed text in this memo, NSAPs are
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 (ISoc, GOSIP, ANSI,
etc.). The use of this notation is strictly for readability. The "."s do
B. Manning/R. Colella [Page 4]
INTERNET-DRAFT DNS NSAP Resource Records May 7, 1993
not appear in DNS packets. For example, a printable representation of
the first four fields of a US GOSIP NSAP might look like
47.0005.80.005a00
and a full US GOSIP NSAP might appear as
47.0005.80.005a00.0000.1000.0020.00800a123456.00.
For more information on US GOSIP NSAPs, see RFC1237 [CGC91]. Other NSAP
formats have different fields and field widths (see [Bry92]).
5 The NSAP RR
The NSAP RR is defined with mnemonic "NSAP" and TYPE code 22 (decimal).
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 DNS 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 /
/ /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
B. Manning/R. Colella [Page 5]
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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
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.
* RDLENGTH: an unsigned 16 bit integer that specifies the length in
octets of the RDATA field.
* RDATA: a variable length string of octets containing the NSAP.
The value is the binary encoding of the NSAP as it would appear in
the CLNP source or destination address field. A typical example of
such an NSAP (in hex) is shown below. For this NSAP, RDLENGTH is
20 (decimal); "."s have been omitted to emphasize that they don't
appear in the DNS packets.
39840f80005a0000000001e13708002010726e00
NSAP RRs cause no additional section processing.
6 The NSAP-PTR RR
[Editors' note: the inverse mapping function is for further study. The
current thinking is that NSAP structure information is stored with NSAP
prefixes in Master Files and returned with queries on NSAP prefixes.
Exactly how this works needs to be given more thought.]
B. Manning/R. Colella [Page 6]
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7 Master File Format
The format of NSAP RRs in Master Files conforms to Section 5, "Master
Files," of RFC 1035. Below is an example of the use of NSAP RR in a
Master File.
[Note: the format of NSAP-PTR RRs in Master Files is for further study.]
;;;;;;
;;;;;; Master File for domain tuba.ncsl.nist.gov.
;;;;;;
@ IN SOA emu.ncsl.nist.gov. root.emu.ncsl.nist.gov. (
900831 ; Serial - date
1800 ; Refresh - 30 minutes
300 ; Retry - 5 minutes
604800 ; Expire - 7 days
3600 ) ; Minimum - 1 hour
IN NS emu.ncsl.nist.gov.
;
;
$ORIGIN tuba.ncsl.nist.gov.
;
emu IN NSAP 47.0005.80.005a00.0000.0001.e137.08002010726e.00
IN A 129.6.55.32
IN HINFO Sun_Sparc SunOS_4.1.3
;
osi IN NSAP 47.0005.80.005a00.0000.0001.e137.080020079efc.00
IN A 129.6.55.1
;
cursive IN NSAP 47.0005.80.005a00.0000.0001.e137.eeeeee000085.00
IN A 129.6.224.85
IN HINFO PC_386 DOS_5.0/NCSA_Telnet(TUBA)
;
cisco1 IN NSAP 47.0005.80.005a00.0000.0001.e137.888888000181.00
IN A 129.6.224.181
;
3com1 IN NSAP 47.0005.80.005a00.0000.0001.e137.111111000111.00
IN A 129.6.225.111
B. Manning/R. Colella [Page 7]
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8 Resolving NSAP-PTR Queries
[Editors' note: this section is still very drafty. It's predicated on
the idea of embedding the NSAP structure information in the Master Files
with the RRs for NSAP prefixes.]
The NSAP-PTR RR is defined with mnemonic "NSAP-PTR" and TYPE code
23 (decimal). It's function is analogous to the PTR record used for
IP addresses [Moc87b], although the details of how it operates are
different.
NSAP-to-name mapping using the NSAP-PTR RR differs from the inverse
lookup for IP addresses due to the structure of NSAPs and the require-
ments this places on the lookup process.
The NSAP-to-name scheme operates with minimal a priori knowledge of how
NSAPs are structured and operates according to a simple algorithm. Given
an NSAP to be resolved, the only a priori information needed is that the
first field of all NSAPs is one octet. The basic algorithm operates as
follows:
1. build an initial query to read the record associated with the first
octet.
2. knowledge of the NSAP structure is not complete, so set (COMPL-KNOW
= FALSE).
3. send the query.
4. when the response is returned, if (COMPL-KNOW == TRUE), done.
5. construct a more detailed query with the additional structure
information from the response.
6. if the structure information returned in step 4 ends with a ".",
then set (COMPL-KNOW = TRUE).
7. go to step 3.
The a priori knowledge required is that all NSAPs begin with an initial
one-octet field, the AFI (Authority and Format Identifier, see [ISO88]);
this is captured in step 1.
Steps 3 through 7 represent a simple learning algorithm in which the
resolver issues queries that are increasingly detailed until the result
is obtained.
B. Manning/R. Colella [Page 8]
INTERNET-DRAFT DNS NSAP Resource Records May 7, 1993
Successful termination, step 4, occurs if the last query sent was based
on complete NSAP structure information, as determined by the trailing
".".
9 Security
Security issues are not addressed in this memo.
10 Authors' Addresses
Bill Manning
Rice University -- ONCS
P.O. Box 1892
6100 South Main
Houston, Texas 77251-1892
USA
Phone: +1.713.285.5415
EMail: bmanning@rice.edu
Richard Colella
National Institute of Standards and Technology
Technology/B217
Gaithersburg, MD 20899
USA
Phone: +1 301-975-3627 (voice); +1 301 590-0932 (fax)
EMail: colella@nist.gov
A. Issues
A number of issues remain to be addressed.
A.1 Relationship to X.500
It may be useful to associate an X.500 distinguished name with an NSAP.
Some thought should be given to whether this is useful and how it could
be done.
B. Manning/R. Colella [Page 9]
INTERNET-DRAFT DNS NSAP Resource Records May 7, 1993
A.2 NSAP prefixes
Should NSAP prefixes be encoded in the DNS? This may have some useful
features.
References
[Bry92] P. Bryant. NSAPs. IPTAG/92/23 PB660, Science and Engineering
Research Council, Rutherford Appleton Laboratory, May 1992.
[Cal92] R. Callon. TCP and UDP with Bigger Addresses (TUBA), a Simple
Proposal for Internet Addressing and Routing. RFC 1347, Network
Working Group, June 1992.
[CGC91] R. Colella, E. Gardner, and R. Callon. Guidelines for OSI
NSAP Allocation in the Internet. RFC 1237, IETF OSI NSAP
Administration Working Group, July 1991.
[GOSIP] GOSIP Advanced Requirements Group. Government Open Systems
Interconnection Profile (GOSIP) Version 2 [final text]. Fed-
eral Information Processing Standard, U.S. Department of
Commerce, National Institute of Standards and Technology,
Gaithersburg, MD, (Pending Publication).
[ISO84] ISO/IEC. Data Interchange - Structures for the Identification
of Organization. International Standard 6523, ISO/IEC JTC 1,
Switzerland, 1984.
[ISO86a] ISO/IEC. Connection Oriented Transport Protocol Specification.
International Standard 8073, ISO/IEC JTC 1, Switzerland, 1986.
[ISO86b] ISO/IEC. Protocol for Providing the Connectionless-mode
Network Service. International Standard 8473, ISO/IEC JTC 1,
Switzerland, 1986.
[ISO88] ISO/IEC. Information Processing Systems -- Data Communications
-- Network Service Definition Addendum 2: Network Layer
Addressing. International Standard 8348/Addendum 2, ISO/IEC
JTC 1, Switzerland, 1988.
B. Manning/R. Colella [Page 10]
INTERNET-DRAFT DNS NSAP Resource Records May 7, 1993
[Moc87a] P. Mockapetris. Domain Name -- Concepts and Facilities. RFC
1034, Network Working Group, November 1987.
[Moc87b] P. Mockapetris. Domain name -- Implementation and Specifica-
tion. RFC 1035, Network Working Group, November 1987.
Expiration Date November 7, 1993 [Page 11]