Internet Draft B. Carpenter February 26, 1995 (editor) Mechanisms for OSI NSAPs, CLNP and TP over IPv6 Abstract draft-carpenter-ipv6-osi-00.txt This document recommends that network implementors who have planned or deployed an OSI NSAP addressing plan, and who wish to deploy or transition to IPv6, should redesign a native IPv6 addressing plan to meet their needs. However, it also defines a set of mechanisms for the support of OSI NSAP addressing, CLNP, and Transport Protocols over an IPv6 network. These mechanisms are the ones that MUST be used if such support is required. This document also defines a mapping of IPv6 addresses within the OSI address format, should this be required. DISCUSSION LIST: send mail to majordomo@sunroof.eng.sun.com with "subscribe nosi" as message body. OPEN ISSUES: 1. Use of restricted or truncated NSAPAs in source routing header? 2. Any advice for CLNP sites with more than one NSAP prefix in use? 3. Do discovery and stateless auto-config work with restricted NSAPs? Do discovery and any kind of auto-config work with truncated NSAPs? 4. Do we need the Total Length field in the NSAPA extension header? (If not make it a reserved field to preserve the alignment) 5. Is the NSAP extension header included in the security payload? 6. Re routing with truncated NSAP addresses (section 4, just below: the diagram) Should we expand the "any suitable way" clause in this paragraph? It seems to imply a high degree of correlation between the [presumedly existing] CLNP network topology and the IPV6 subnet structure. Or is this an unjustified assumption? 7. Should CLNP encapsulation & TP over IPv6 be separate documents? 8. Which IETF working groups should adopt the document(s) after Danvers? Expires August 31, 1995 [Page 1] Table of Contents: Status of this Memo.............................................3 1. General recommendation on NSAP addressing plans..............4 2. Summary of defined mechanisms................................5 3. Restricted NSAPA in a 16-byte IPv6 address for ICD and DCC...6 4. Truncated NSAPA used as an IPv6 address......................8 5. Carriage of full NSAPAs in IPv6 extension headers............9 6. CLNP encapsulated in IPv6...................................10 7. ISO Transport Protocols over IPv6...........................11 8. IPv6 addresses inside an NSAPA..............................13 9. Security condiderations.....................................14 Acknowledgements...............................................14 References.....................................................15 Annex A: Summary of NSAP Allocations...........................16 Authors' Addresses.............................................18 Expires August 31, 1995 [Page 2] 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 and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as ``work in progress.'' To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Expires August 31, 1995 [Page 3] 1. General recommendation on NSAP addressing plans This recommendation is addressed to network implementors who have already planned or deployed an OSI NSAP addressing plan for the usage of OSI CLNP [IS8473] according to the OSI network layer addressing plan [IS8348]. It recommends how they should adapt their addressing plan for use with IPv6 [IPv6]. The majority of known CLNP addressing plans use either the Digital Country Code (DCC) or the International Code Designator (ICD) formats defined in [IS8348]. A particular example of this is the US Government OSI Profile Version 2 (GOSIP) addressing plan [RFC1629]. The basic NSAP addressing scheme and current implementations are summarised in Annex A. [IS8348] specifies a maximum NSAP address size of 20 bytes and some network implementors have designed address allocation schemes which make use of this 20 byte address space. Other NSAP addressing plans have been specified by the ITU-T for public data services, such as X.25 and ISDN, and these can also have addresses up to 20 bytes in length. The general recommendation is that implementors SHOULD design native IPv6 addressing plans according to [Rekhter], but doing so as a natural re-mapping of their CLNP addressing plans. While it is impossible to give a general recipe for this, CLNP addresses in DCC or ICD format can normally be split into two parts: the high order part relating to the network service provider and the low order part relating to the user network topology and host computers. For example, in some applications of US GOSIP the high order part is the AFI, ICD, DFI, AA and RD fields, together occupying 9 bytes. The low order part is the Area and ID fields, together occupying 8 bytes. (The selector byte and the two reserved bytes are not part of the addressing plan.) Thus, in such a case, the high-order part would be replaced by the provider part of an IPv6 provider-based addressing plan. An 8-byte provider prefix is recommended for this case and [Rekhter] MUST be followed in planning such a replacement. The low order part would then be mapped directly in the low-order half of the IPv6 address space, and user site address plans are unchanged. A 6- byte ID field, exactly as used in US GOSIP and other CLNP addressing plans, will be acceptable as the token for IPv6 autoconfiguration [addrconf]. Analogous rules would be applied for other CLNP addressing plans similar to US GOSIP, which is considered only as a well known example. Expires August 31, 1995 [Page 4] 2. Summary of defined mechanisms The remainder of this document defines six distinct mechanisms. All of these are ELECTIVE mechanisms, i.e. they are not mandatory parts of an IPv6 implementation, but if such mechanisms are needed they MUST be implemented as defined in this document. 1. Restricted NSAPA mapping into 16-byte IPv6 address 2. Truncated NSAPA for routing, full NSAPA in IPv6 extension header 3. Normal IPv6 address, full NSAPA in IPv6 extension header 4. CLNP encapsulated in IPv6 5. OSI Transport Protocol carried over IPv6 6. IPv6 address carried as OSI address Note in addition that an Internet Standard STD-35 "ISO Transport Service on top of the TCP" exists already [RFC1006]. There is a also a Proposed Standard for "OSI Connectionless Transport Service over UDP" [RFC1240]. To clarify the relationship between the first four mechanisms, note that: If the first byte of an IPv6 address is hexadecimal 0x02 (binary 00000010), then the remaining 15 bytes SHALL contain a restricted NSAPA mapped as in Section 3 below. If the first byte of an IPv6 address is hexadecimal 0x03 (binary 00000011), then the remaining 15 bytes SHALL contain a truncated NSAPA as described in Section 4 below. EITHER an extension header containing the complete NSAPA, as in Section 5 below, OR an encapsulated CLNP packet, SHALL be present. With any other format of IPv6 address, an extension header containing a complete NSAPA, as defined in Section 5 below, MAY be present. Alternatively, an encapsulated CLNP packet MAY be present. Expires August 31, 1995 [Page 5] 3. Restricted NSAPA in a 16-byte IPv6 address for ICD and DCC Some organizations may decide for various reasons not to follow the above general recommendation to redesign their addressing plan. They may wish to use their existing OSI NSAP addressing plan unchanged for IPv6. It should be noted that such a decision has serious implications for routing, since it means that routing between such organizations and the rest of the Internet is unlikely to be optimised. An organization using both native IPv6 addresses and NSAP addresses for IPv6 would be likely to have inefficient internal routing. Nevertheless, to cover this eventuality, the present document defines a way to map a subset of the NSAP address space into the IPv6 address space. The mapping is algorithmic and reversible within this subset of the NSAP address space. Certain other uses of this algorithmic mapping could be envisaged. It could be used as an intermediate addressing plan for a network making a transition from CLNP to IPv6. It could be used in a header translation scheme for dynamic translation between IPv6 and CLNP. It could be used to allow CLNP and IPv6 traffic to share the same routing architecture within an organization (Ships in the Day). 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0-3 |0 0 0 0 0 0 1 0| AFcode| IDI (last 3 digits) |Prefix(octet 0)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 4-7 | Prefix (octets 1 through 4) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 8-11 | Area (octets 0 and 1) | ID (octets 0 and 1) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 12-15| ID (octets 2 through 5) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The AFcode nibble is encoded as follows 0000-1001 AFI value is 47 (ICD) (0-9 decimal) AFcode is first BCD digit of the ICD IDI is last three BCD digits of the ICD 1010 AFI value is 39 (DCC) (hex. A) IDI is the three BCD digits of the DCC 1011-1111 Reserved, not to be used. (hex. B-F) The NSEL octet is not included. It is of no use for TCP and UDP traffic. In any case where it is needed, the mechanism described in the next section should be used. The longest CLNP routing prefixes known to be in active use today are 5 octets (subdivided into AA and RD fields in US GOSIP version 2). Thus the semantics of existing 20-octet NSAPAs can be fully mapped. DECnet/OSI (Registered Trade Mark) address semantics are also fully mapped. Expires August 31, 1995 [Page 6] A network using such addresses could route using Internet routing protocols (or suitably adapted implementations of ES-IS [3], IS-IS [4] and IDRP [5]). It is expected that hosts using such addresses could be configured using IPv6 stateful auto-configuration [addrconf]. Expires August 31, 1995 [Page 7] 4. Truncated NSAPA used as an IPv6 address An NSAP address contains routing information (e.g. Routing Domain and area/subnet identifiers) in the form of the Area Address (as defined in [IS10589]). The format and length of this routing information are typically compatible with a 16 byte IPV6 address, and may be represented as such using the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0-3 |0 0 0 0 0 0 1 1| High order octets of full NSAP address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 4-7 | NSAP address continued | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 8-11 | NSAP address continued and truncated | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 12-15| zero pads if necessary | pack ID if applicable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ In this case, the high order octets which make up the Area Address portion of the NSAP address are used in any suitable way for routing to an IPv6 node which can interpret a full NSAP address. Depending upon the length of the NSAP, it may be possible to use the same system ID value in the IPv6 address as in the NSAP. If appropriate, the address can be interpreted as an IPv6 pack address, with the pack ID in the two low order bytes of the address. A pack ID may be used to identify either a host or router, or potentially even an OSI Endsystem or Intermediate System. For example, a pack ID might be configured to identify the endpoints of a CLNP tunnel, or it might identify a particular OSI capable system in a particular subnet. If such an address is used as either the source or destination IPv6 address, an NSAPA extension header or CLNP packet MUST be present. It is the responsibility of the system identified by the pack ID to take the appropriate action for each IPV6 packet received (e.g. forward, decapsulate, discard) and, if necessary, return to the originating host an appropriate ICMP error message. If a pack ID is used to identify a router in a particular subnet, and the NSAPA extension header follows the IPV6 routing header, then it is the responsibility of that router to forward the complete IPV6 packet to the appropriate host based upon the Destination NSAP field in the NSAPA header. This forwarding process may be based upon static routing information (i.e. a manual mapping of NSAPs to IPV6 unicast addresses), or it may be gathered in an automated fashion analogous to the ES-IS mechanism, perhaps using extensions to the Neighbor Discovery protocol. The details of such a mechanism are beyond the scope of this document. This document does not restrict the formats of NSAP address that may be used in truncated NSAPAs, but it is apparent that binary ICD or DCC formats will be much easier to accomodate in an IPv6 routing infrastructure than the other formats defined in [IS8348]. Expires August 31, 1995 [Page 8] 5. Carriage of full NSAPAs in IPv6 extension headers The codings described in the previous sections are inadequate if the ICD or DCC binary format in use is too large to fit into 16 bytes, or if any other format defined in [IS8348] must be carried. In this case, an IPv6 extension header of type NSAPA is used. Protocol code 57 has been assigned by IANA for this and will appear in the next edition of [assigned]. This header follows the IPv6 routing header if present, and its format is: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Total Length |Source NSAP Len| Dest. NSAP Len| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + | | + Source NSAP + | | + + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination NSAP + | | + + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Pad with zeros to next 64-bit boundary | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The length fields are each one octet long and are expressed in octets. The boundary between the source NSAP and the destination NSAP length is simply aligned on an octet boundary. With standard 20 octet NSAPs the total header length is 48 bytes. The NSAP encodings follow [IS8348] exactly. If only one of the end systems uses NSAP addresses, the NSAP Length field of the other SHALL be set to zero in the NSAP extension header. This extension header is used in two cases. Firstly, an IPv6 source node using normal IPv6 addresses (unicast address or pack address) MAY supply an NSAP extension header for interpretation by the IPv6 destination node. Secondly, an IPv6 node MAY use a truncated NSAP address in place of a normal IPv6 address. Expires August 31, 1995 [Page 9] 6. CLNP encapsulated in IPv6 If it is required to tunnel CLNP [IS8473] through an IPv6 network, then the transport header SHALL be a CLNP PDU, and the final IPv6 Next Header field SHALL have the value 80 decimal (as defined for ISO-IP in [assigned]). Mechanisms for the creation of CLNP tunnels and their management are outside the scope of this document. As for the cases described in the previous section, the IPv6 end nodes might be conveniently reached by pack addresses. Note that the tunnelling of CLNP over the Internet is discussed in detail in [RFC1070], but that document has no standards status and makes different assumptions about address mapping. In contrast to [RFC1070], CLNP tunnels through an IPv6 network are simply a virtual point-to-point encapsulation technology, using statically configured tunnel endpoints. There is no support for simulating a multipoint subnetwork, nor for dynamic mapping between NSAP addresses and IP addresses. Instead, IP addresses are simply viewed as Subnetwork Point of Attachment (SNPA) addresses that must be statically configured to create the tunnel. Once a tunnel is established, data is transmitted using CLNP [IS8473]. The ES-IS [3], IS-IS [4], and IDRP [5] protocols may be used to dynamically establish neighbor adjacencies and routing. Any NSAP addresses may be assigned to the systems at either end of the tunnel. There is no need to constrain the NSAP address format as documented in [RFC1070], since there is no need to perform dynamic address mapping. The "EON" header of [RFC1070] is not present. No attempt is required to implement feedback of error indications from ICMP in the IP subnetwork into CLNP error PDUs. The tunnel is ignorant of problems in the IP subnetwork, and depends upon mechanisms in the OSI routing protocols to detect connectivity failures. Expires August 31, 1995 [Page 10] 7. ISO Transport Protocols over IPv6 If it is required to carry ISO Transport Protocols [ISO8072, ISO8073] over an IPv6 network, then the IPv6 transport header SHALL be a TP PDU, and the final IPv6 Next Header field SHALL have the value 29 decimal (as defined for ISO-TP in [assigned]). +---------------+------------------------ | IPv6 header | TP PDU | | | Next Header = | | ISO-TP | +---------------+------------------------ +---------------+----------------+------------------------ | IPv6 header | Routing header | TP PDU | | | | Next Header = | Next Header = | | Routing | ISO-TP | +---------------+----------------+------------------------ 7.1 Protocol Classes The ISO connection-oriented transport protocol [ISO8073] supports five different classes of service. Only one such class, class 4 (TP4), is suitable for use on a connectionless network service such as provided by IPv6. Transport classes 0 through 3 should not carried over an IPv6 network in this manner. Note that the connectionless transport protocol [ISO8072] has no such restriction. Its PDUs should be carried exactly as described above. There is no conflict inherent in using the same IPv6 Next Header value for both connection-oriented and connectionless protocols. ISO transport implementations can distinguish the two protocols by their different PDU types. 7.2 Maximum TPDU Size When negotiating a maximum TPDU size, TP4 implementations may consider the services available from the network layer. Unlike IPv4 or CLNP, IPv6 only permits fragmentation by the originating system. TP4 may use its knowledge of the capabilities of the local system to maximize the efficiency of data transfer. 7.2.1 Path MTU Discovery and Fragmentation If the TP4 implementation can accept Path MTU Discovery [RFC1191] information, and if the TP4 implementation can efficiently invoke the IPv6 fragmentation function, then the TP4 may propose the largest TPDU size and/or preferred maximum TPDU size that the implementation can support. If, during the life of the connection, IPv6 reports PMTU information to the TP4 implementation, TP4 should adjust its local TPDU size accordingly. Note that the original TPDU (the one which solicited the PMTU) cannot be repacketized; TP4 must instead rely on IPv6 fragmentation for that PDU's retransmission. Expires August 31, 1995 [Page 11] 7.2.2 No Path MTU Discovery or Fragmentation If the TP4 implementation cannot accept Path MTU Discovery information from IPv6, or if it cannot efficiently invoke the IPv6 fragmentation function, then TP4 may propose a TPDU size of {512|1024} octets and a preferred maximum TPDU size of {512|1408} octets. These sizes will ensure that TPDUs are no larger than the IPv6 minimum MTU of {576|1500} bytes [IPv6]. 7.3 PDU Lifetime Unlike IPv4 and CLNP, IPv6 nodes are not required to enforce PDU lifetimes. Any transport protocol that relies on the network protocol to limit packet lifetime ought to be upgraded to provide its own mechanisms for detecting and discarding obsolete packets. 7.4 Related work The carriage of OSI Connectionless Transport Services over UDP is described in [RFC1240], which is currently a Proposed Standard. The present proposal is independent of that one. Expires August 31, 1995 [Page 12] 8. IPv6 addresses inside an NSAPA If it is required, for whatever reason, to embed an IPv6 address inside a 20-octet NSAP address, then the following format MUST be used. A specific possible use of this embedding is to express an IP address within the ATM Forum address format [UNI]. Another possible use would be to allow CLNP packets that encapsulate IPv6 packets to be routed in a CLNP network using the IPv6 address architecture. Several leading bytes of the IPv6 address could be used as a CLNP routing prefix. The first three octets are an IDP meaning "this NSAPA embeds a 16 byte IPv6 address" and the last octet is a dummy selector. To maintain compatibility with both NSAP format and IPv6 addressing, this octet must be present but unused. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0-3 | AFI = 47 | ICD = ISoc (TBD) | IPv6 (byte 0)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 4-7 | IPv6 (bytes 1-4) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 8-11 | IPv6 (bytes 5-8) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 12-15| IPv6 (bytes 9-12) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 16-19| IPv6 (bytes 13-15) |0 0 0 0 0 0 0 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Recursive address embedding is not allowed. The embedded IPv6 address MUST NOT have the prefixes 0x02 or 0x03, and an NSAP with the Isoc ICD code MUST NOT be embedded in an IPv6 packet. Expires August 31, 1995 [Page 13] 9. Security condiderations Security issues are not specifically addressed in this document, but it is compatible with the IPv6 security mechanisms [security]. Note, however, that when CLNP is tunnelled through IPv6 the IPv6 security mechanisms can at best protect the tunnel, but not the end-to-end CLNP service. Acknowledgements All direct contributors of text are listed below as authors. The editor is also pleased to acknowledge the suggestions and comments of Richard Collella, Dirk Fieldhouse, Denise Heagerty, Cyndi Jung, Yakov Rekhter, and many other members of the former TUBA and new IPv6 working groups of the IETF. The support of Scott Bradner and Allison Mankin of the IESG was essential. Expires August 31, 1995 [Page 14] References [ISO8072] Protocol for providing the connectionless-mode transport service, ISO/IEC 8072, 1987. [ISO8073] Protocol for providing the connection-mode transport service, ISO/IEC 8073 (2nd ed.), 1992. [RFC1191] Path MTU Discovery, Mogul and Deering, November 1990. [IS8473] Data communications protocol for providing the connectionless-mode network service, ISO/IEC 8473, 1988. [IS8348] Annex A, Network Layer Addressing, and Annex B, Rationale for the material in Annex A, of ISO/IEC 8348, 1993 (identical to CCITT Recommendation X.213, 1992). [IS10589] ??? [3] ISO, "End system to Intermediate system routeing exchange protocol for use in conjunction with the Protocol for providing the connectionless-mode network service (ISO 8473)," ISO 9542:1988. [4] ISO, "Intermediate system to Intermediate system routeing information exchange protocol for use in conjunction with the Protocol for providing the Connectionless-mode Network Service (ISO 8473)," ISO/IEC 10589:1992. [5] ISO, "Intermediate system to Intermediate system interdomain routeing information exchange protocol for use in conjunction with the Protocol for providing the Connectionless-mode Network Service (ISO 8473)," ISO/IEC 10747:1993. [IPv6] The IPv6 base documents [RFC1006] STD-35, ISO Transport Service on top of the TCP... [RFC1070] Use of the Internet as a Subnetwork for Experimentation with the OSI Network Layer... [RFC1240] OSI Connectionless Transport Services on top of UDP... [RFC1629] The one that explains GOSIPv2 addressing [Rekhter] Forthcoming IPv6 address allocation documents. [addrconf] Forthcoming IPv6 autoconfig document. [assigned] J. Reynolds, J. Postel, "ASSIGNED NUMBERS", RFC 1700 [UNI] ATM Forum UNI 3.x [security] IPv6 security spec Expires August 31, 1995 [Page 15] Annex A: Summary of NSAP Allocations -----IDP------ ----------------------------------------------------- | AFI | IDI | DOMAIN SPECIFIC PART | ----------------------------------------------------- --------------------20 bytes max--------------------- The Initial Domain Part (IDP) is split into Authority and Format Identifier (AFI) followed by the Initial Domain Identifier (IDI). This combination is followed by the Domain Specific Part and allocation within that part is domain specific. The following is a summary of current allocations: ISO DCC Scheme AFI = decimal 38 or binary 39 = ISO Data Country Code Scheme. IDI = 3 decimal or binary digits specifying the country. ISO allocate the country codes. The DSP is administered by the standards authority for each country. In the UK, the British Standards Institution have delegated administration to the Federation of Electronics Industries - FEI The UK DSP is split into a single digit UK Format Indicator (UKFI) which indicates large, medium or small organisation rather like IP addressing and a UK Domain Identifier (UKDI). Using binary code decimal examples only (there are binary equivalents): UKFI = 0 is reserved UKFI = 1, UKDI = nnn, UK Domain Specific Part = 31 digits. UKFI = 2, UKDI = nnnnn, UKDSP = 29 digits max. UKFI = 3, UKDI = nnnnnnnn, UKDSP = 26 digits max. UKFI = 4 to 9 reserved The UK Government have been allocated a UKDI in the UKFI = 1 (large organisation) format and have specified the breakdown of the Government Domain Specific Part with sub domain addresses followed by a station ID (which could be a MAC address) and a selector (which could be a TSAP selection). ITU-T X.121 AFI = decimal 36 or 52, binary 37 or 53 indicates that the IDI is a 14 digit max X.121 International Numbering Plan address (prefix, 3 digit Data Country Code, dial up data network number). The full X.121 address indicates who controls the formatting of the DSP. ITU-T F.69 AFI = 40,54 or binary 41,55 indicates that the IDI is a telex number up to 8 digits long. ITU-T E.163 AFI = 42,56 or binary 43,57 indicates that the IDI is a normal telephone number up to 12 digits long. Expires August 31, 1995 [Page 16] ITU-T E.164 AFI = 44,58 or binary 45,59 indicates that the IDI is an ISDN number up to 15 digits long. ISO 6523-ICD AFI = 46 or binary 47 indicates that the IDI is an International Code Designator allocated according to ISO 6523. You have to be a global organisation to get one of these. The Organisation to which the ISO 6523 designator is issued specifies the DSP allocation. Expires August 31, 1995 [Page 17] Authors' Addresses Jim Bound Member Technical Staff Phone: (603) 881-0400 Network Operating Systems Fax: (603) 881-0120 Digital Equipment Corporation Email: bound@zk3.dec.com 110 Spitbrook Road, ZKO3-3/U14 Nashua, NH 03062 Brian E. Carpenter Group Leader, Communications Systems Phone: +41 22 767-4967 Computing and Networks Division Fax: +41 22 767-7155 CERN Telex: 419000 cer ch European Laboratory for Particle Physics Email: brian@dxcoms.cern.ch 1211 Geneva 23, Switzerland Dan Harrington Phone: (508) 486-7643 Digital Equipment Corp. 550 King Street (LKG2-2/Q9) Email: dan@netrix.lkg.dec.com Littleton, MA 01460 Jack Houldsworth Phone- ICL: +44 438 786112 ICL Network Systems Home: +44 438 352997 Cavendish Road Fax: +44 438 786150 Stevenage Email: j.houldsworth@ste0906.wins.icl.co.uk Herts UK SG1 4BQ Dave Katz Phone: +1 (415) 688-8284 cisco Systems, Inc. EMail: dkatz@cisco.com 1525 O'Brien Dr. Menlo Park, CA 94025 Alan Lloyd Phone: +61 3 727 9222 Datacraft Technologies Fax: +61 3 727 1557 252 Maroondah Highway Email: alan.lloyd@datacraft.com.au Mooroolbark 3138 Victoria Australia X.400- G=alan;S=lloyd;O=dcthq;P=datacraft;A=telememo;C=au Stephen Thomas Associate Principal Engineer Phone: (404) 514-3522 AT&T Tridom Fax: (404) 514-3491 840 Franklin Court Email: stephen.thomas@tridom.com Marietta, GA 30067 USA Expires August 31, 1995 [Page 18]