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+Network Working Group R. Callon
+Request for Comments: 1069 DEC
+Obsoletes: RFC 986 H.W. Braun
+ UMich
+ February 1989
+
+
+ Guidelines for the use of Internet-IP addresses in the
+ ISO Connectionless-Mode Network Protocol
+
+Status of This Memo
+
+ This RFC suggests an addressing scheme for use with the ISO
+ Connectionless Network Protocol (CLNP) in the Internet. This is a
+ solution to one of the problems inherent in the use of "ISO-grams" in
+ the Internet. This RFC suggests a proposed protocol for the Internet
+ community, and requests discussion and suggestions for improvements.
+ Distribution of this memo is unlimited.
+
+ This memo is a revision of RFC 986. Changes were made in order to
+ allow the addressing used in the CLNP in the Internet to be
+ potentially useful for routing in the context of new inter- and
+ intra-domain routing protocols, and in the context of large numbers
+ of networks and routing domains. The addressing scheme proposed in
+ this RFC allows individual routing domains to make use of internal
+ routing algorithms utilizing a variety of addressing formats, while
+ still providing for a common addressing approach for use by inter-
+ domain routing. These features are important due to the rapid growth
+ currently being experienced in the Internet.
+
+1. Objectives
+
+ The data communications protocols currently emerging out of the
+ international standardization efforts warrant an early integration
+ into the existing extensive Internet network infrastructure. The two
+ possible approaches are a top-down one, where ISO applications like
+ FTAM, X.400 and VTP are integrated on top of the transport function
+ of the IP protocol suite, or a bottom-up approach where the whole ISO
+ tower gets integrated without merging the two suites. The bottom-up
+ approach may make use of the fact that the ISO-CLNP and the IP are
+ very similar in function. This implies that it is reasonable to
+ implement a multiprotocol function in some or all of the Internet
+ gateways (potentially including part or all of the Internet
+ environment). The result would be that at least large portions of
+ the Internet, in particular the backbones, can become usable for full
+ implementations of the ISO protocol stack.
+
+ A major problem with this approach is that there are open issues with
+
+
+
+Callon & Braun [Page 1]
+
+RFC 1069 IP ISO Addressing February 1989
+
+
+ regard to the ISO addressing within the CLNP. In particular, the ISO
+ network layer addressing standard allows a great deal of flexibility
+ in the assignment of addresses, and a particular address format must
+ be chosen. A further problem is the need for implementation and
+ integration of routing facilities for the ISO-compatible subset of
+ the Internet environment.
+
+ This paper proposed to use addresses which are considerably more
+ flexible than the addresses used in the current IP Internet
+ environment. This flexibility is necessary in order to allow some
+ routing domains to base their internal routing protocol on addresses
+ derived from the current IP addresses, to allow other routing domains
+ to base routing on addresses in accordance to the intra-domain
+ routing protocol being developed by ANSI and ISO [6], and to allow
+ generality for a future inter-domain routing protocol.
+
+ The addressing scheme proposed here makes use of the concept of
+ "routing domains" as used in ANSI and ISO. This concept is similar
+ to, but not identical with, the concept of "Autonomous System" used
+ in the Internet. Routing domains include a combination of gateways,
+ networks, and end systems (not just gateways), and routing domain
+ boundaries may be used to define associated access control and policy
+ routing constraints. Like autonomous systems, routing domains may be
+ assumed to be topologically contiguous. There is no a priori reason
+ why routing domains assigned for use with the ISO IP need to have any
+ particular relation with existing autonomous systems which have been
+ assigned for use with the IP. The assignment of specific routing
+ domain identifiers is an "assigned numbers" function which is
+ necessary for use of the ISO IP in the Internet, but is beyond the
+ scope of this document.
+
+ It is expected that this addressing scheme will be appropriate for
+ long term use with the ISO IP in the Internet. However, it is also
+ expected that in the long term, the Internet will be interconnected
+ with other routing domains making use of other schemes, such as
+ addresses assigned to commercial internets through ANSI, and
+ addresses assigned by national standards organizations in other
+ countries. This implies that, in the long term, gateways in the
+ Internet will need to be able to route datagrams to destinations in
+ other routing domains not conforming to the addressing format
+ proposed here. This is discussed in greater detail in section 6.
+
+2. Introduction
+
+ The CLNP is documented in [1], but for matters of completeness the
+ following illustration of the CLNP header is included here as Figure
+ 1.
+
+
+
+
+Callon & Braun [Page 2]
+
+RFC 1069 IP ISO Addressing February 1989
+
+
+ The addressing part of the header is the subject of this RFC, i.e.,
+ the source and the destination address, respectively. These
+ addresses are generally discussed in [2] and [3], with this document
+ presenting a specific method for addressing in the Internet
+ environment, consistent with the international standardized NSAP
+ addresses.
+
+ Octet
+ +--------------------------------------+ +--------
+ | Network Layer Protocol Identifier | 1 :
+ |--------------------------------------| :
+ | Length Indicator | 2 :
+ |--------------------------------------| :
+ | Version/Protocol Id Extension | 3 : Fixed
+ |--------------------------------------| :
+ | Lifetime | 4 : Part
+ |--------------------------------------| :
+ |SP|MS|E/R| Type | 5 :
+ |--------------------------------------| :
+ | Segment Length | 6,7 :
+ |--------------------------------------| :
+ | Checksum | 8,9 :
+ |--------------------------------------| +--------
+ | Destination Address Length Indicator | 10 :
+ |--------------------------------------| :
+ | Destination Address | 11 through m-1 : Address
+ |--------------------------------------| :
+ | Source Address Length Indicator | m : Part
+ |--------------------------------------| :
+ | Source Address | m+1 through n-1 :
+ |--------------------------------------| +--------
+ | Data Unit Identifier | n,n+1 :
+ |--------------------------------------| : Segment
+ | Segment Offset | n+2,n+3 : ation
+ |--------------------------------------| :
+ | Total Length | n+4,n+5 : Part
+ |--------------------------------------| +--------
+ | Options | n+6 through p : Options
+ Part
+ |--------------------------------------| +--------
+ | Data | p+1 through z : Data
+ +--------------------------------------+ +--------
+
+ Figure 1: PDU Header Format
+
+
+
+
+
+
+
+Callon & Braun [Page 3]
+
+RFC 1069 IP ISO Addressing February 1989
+
+
+3. Addresses for Use in the Internet
+
+ This section describes the addresses used to address NSAPs in the
+ Internet.
+
+ The appropriate Authority and Format Identifier (AFI) is one octet in
+ length. It specifies an ISO-6523-ICD assignment, and also that the
+ Domain Specific Part (DSP) of the address is based on binary. The
+ AFI octet uses the value "47". The ISO-6523-ICD format is used to
+ emphasize that this is an administrative assignment. The usage of an
+ ISO DCC (Data Country Code) would be possible, but could be
+ misleading due to the fairly far spread geographical extent of the
+ Internet.
+
+ As required by the ISO addressing standard, the next two octets of
+ the address, in this case, specify the Initial Domain Identifier.
+ This two octet value is the International Code Designator (ICD)
+ assigned to the Internet, "0006".
+
+ The remainder of the NSAP address is the Domain Specific Part (DSP).
+ This is assigned by the Internet administration, which is considered
+ to be an addressing domain. Note that there is no particular
+ relationship required between addressing domains and routing domains.
+ In this case, although the Internet is considered to be a single
+ addressing domain, it is expected that it will consist of multiple
+ routing domains.
+
+ The DSP of the address specifies a one octet version number, a two
+ octet global area number, a two octet routing domain number, a
+ variable length padding field, a variable length IGP specific part,
+ and a one octet selector field.
+
+ The version number is provided to allow for future extensions, and
+ must contain the value "02".
+
+ The global area number and routing domain number are provided to
+ allow for inter-domain routing. Initially, the global area number is
+ reserved and must be set to zero. The routing domain number may be
+ set to the routing domain number of any gateway by which the
+ associated host address is directly reachable.
+
+ The IGP specific part of the address may contain whatever addressing
+ format is used in the routing domain. Two particular formats are
+ expected to be used initially, and are presented in section 4.
+ Padding is used so that the entire address will always be 20 octets
+ in length.
+
+ The selector field performs the same function as the user protocol
+
+
+
+Callon & Braun [Page 4]
+
+RFC 1069 IP ISO Addressing February 1989
+
+
+ field in the IP header. This is necessary because the ISO protocol
+ considers identification of the user protocol to be an addressing
+ issue, and therefore does not allow for the user protocol to be
+ specified in the protocol header independently from the address.
+
+ The assignment of specific routing domain identifiers to defined
+ routing domains, and the assignment of values for use in the selector
+ field, are functions for the Assigned Numbers authority for the
+ Internet [4]. The specific values to be used are outside of the
+ scope of this document.
+
+ In summary, a source or destination address within the ISO
+ Connectionless Protocol, when used in the Internet, looks as follows:
+
+ Octet
+
+ +------------------------+
+ | AFI | 1
+ +------------------------+
+ | IDI / ICD | 2
+ +-- --+
+ |(specifies DoD Internet)| 3
+ +------------------------+
+ | Version Number | 4
+ +------------------------+
+ | Global Area | 5
+ +--- ---+
+ | Number | 6
+ +------------------------+
+ | Routing | 7
+ +--- ---+
+ | Domain | 8
+ +------------------------+
+ | | 9
+ : Padding : :
+ : : :
+ | | n
+ +------------------------+
+ | IGP | n+1
+ : : :
+ : : :
+ | Specific | 19
+ +------------------------+
+ | Selector | 20
+ +------------------------+
+
+ Figure 2: ISO IP address structure
+
+
+
+
+Callon & Braun [Page 5]
+
+RFC 1069 IP ISO Addressing February 1989
+
+
+ The Authority and Format Identifier (AFI) is "47" (BCD). The Initial
+ Domain Identifier (IDI) consists of the International Code Designator
+ (ICD) assigned to the Internet, and must contain the value "0006".
+ The Version Number must contain the value "02". The Global Area
+ Number must contains the value "00". The Padding field is of
+ variable length, but must contain the value zero.
+
+4. Specific Values for use with the IGP specific field
+
+ In general, a particular routing domain may specify any addressing
+ scheme for use with the IGP specific part of the address, up to 11
+ octets in length (consistent with the maximum address length of 20
+ octets). However, it is expected that initially addresses used in
+ this field will consist of either the current IP addresses, or
+ addresses conformant with those specified in the draft ANSI proposal
+ for intra-domain routing.
+
+ For end systems which are members of routing domains using the IP
+ addresses for internal routing, the addresses will look as follows:
+
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+Callon & Braun [Page 6]
+
+RFC 1069 IP ISO Addressing February 1989
+
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+ Octet
+
+ +------------------------+
+ | AFI | 1
+ +------------------------+
+ | IDI / ICD | 2
+ +-- --+
+ |(specifies DoD Internet)| 3
+ +------------------------+
+ | Version Number | 4
+ +------------------------+
+ | Global Area | 5
+ +--- ---+
+ | Number | 6
+ +------------------------+
+ | Routing | 7
+ +--- ---+
+ | Domain | 8
+ +------------------------+
+ | | 9
+ : Padding : :
+ : : :
+ | | 15
+ +------------------------+
+ | Four Octet | 16
+ +--- ---+
+ | Internet | 17
+ +--- ---+
+ | DoD | 18
+ +--- ---+
+ | Address | 19
+ +------------------------+
+ | Selector | 20
+ +------------------------+
+
+ Figure 3: ISO IP Address with Encoded DoD IP Address
+
+ For end systems which are members of routing domains using the
+ address format specified in the draft ANSI proposal for intra-domain
+ routing [6], the addresses will look as follows:
+
+
+
+
+
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+
+
+Callon & Braun [Page 7]
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+RFC 1069 IP ISO Addressing February 1989
+
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+ Octet
+
+ +------------------------+
+ | AFI | 1
+ +------------------------+
+ | IDI / ICD | 2
+ +-- --+
+ |(specifies DOD Internet)| 3
+ +------------------------+
+ | Version Number | 4
+ +------------------------+
+ | Global Area | 5
+ +--- ---+
+ | Number | 6
+ +------------------------+
+ | Routing | 7
+ +--- ---+
+ | Domain | 8
+ +------------------------+
+ | | 9
+ +--- ---+
+ | Padding | 10
+ +--- ---+
+ | | 11
+ +------------------------+
+ | | 12
+ +--- LOC-AREA ---+
+ | | 13
+ +------------------------+
+ | | 14
+ : ID : :
+ : : :
+ | | 19
+ +------------------------+
+ | Selector | 20
+ +------------------------+
+
+ Figure 4: ISO IP Address with Encoded ANSI-format Address
+
+5. Devices Attached to PDNs
+
+ Otherwise isolated end systems, which are attached to the Internet
+ only indirectly via public data networks, and simple LANs which are
+ similarly attached only via Public Data Networks, may make use of a
+ separate address format based on their X.121 address. Such addresses
+ may, for example, use the ISO-X.121 address format discussed in [3].
+ These addresses will need to be handled for routing purposes in much
+ the same way as addresses in routing domains which have been
+
+
+
+Callon & Braun [Page 8]
+
+RFC 1069 IP ISO Addressing February 1989
+
+
+ interconnected to the Internet, but which use other address formats,
+ such as those specified by national standards bodies.
+
+6. Migration to Future Routing Protocols
+
+ Initially, routing of ISO datagrams in the Internet may make use of
+ the first 8 octets of the address (AFI, ICD, version, global area
+ number, and routing domain number) as a flat field identifying the
+ routing domain. This implies that if EGP is initially used for
+ routing between routing domains, a new version of EGP may be required
+ to carry 8 octet routing domain numbers instead of 3 octet network
+ numbers.
+
+ There are currently several efforts underway to determine the
+ requirements for inter-autonomous system routing, and to define a new
+ protocol. One of the requirements of inter-autonomous system routing
+ is the need to be able to deal with a very large Internet. It is
+ anticipated that during the lifetime of the addressing scheme
+ described in this RFC the number of networks in the Internet will
+ grow to the point where it is no longer feasible for any gateway to
+ maintain separate routes to every network in the Internet. Allowing
+ inter-domain routing to be done by routing domain number instead of
+ network number is therefore a necessary step in the long term.
+
+ It is difficult to anticipate the rate at which the number of routing
+ domains may grow. For example, during a period of time in which the
+ number of networks grows by a factor of 100, it is not clear whether
+ the number of routing domains may also be expected to grow by a
+ factor of 100, or by some lesser amount. It is possible that the
+ number of routing domains will also grow to a point where it is not
+ feasible for a single gateway to maintain separate routes to each.
+ In order to prepare for this eventuality, we have provided for a
+ "global area" field.
+
+ In the long term, it will be necessary for gateways to route to
+ destinations which are in routing domains utilizing other addressing
+ formats, specified by other organizations such as ANSI, ECMA, etc.
+ In this case, it will not be possible to ensure that the first 8
+ octets of the address specifies the routing domain. In the long
+ term, it will therefore be necessary to route based on variable
+ length routing domain identifiers. It may be assumed that future
+ inter-domain routing protocols will allow for specification of either
+ (1) an address mask, specifying which part of an address is relevant
+ for specifying those destinations which are reachable via a
+ particular domain; or (2) a length field, specifying how many leading
+ octets in a particular address are relevant. Specification of the
+ details of such a routing protocol is beyond the scope of this
+ document.
+
+
+
+Callon & Braun [Page 9]
+
+RFC 1069 IP ISO Addressing February 1989
+
+
+References
+
+ [1] ISO, "Protocol for Providing the Connectionless-Mode Network
+ Services", RFC-926, ISO, December 1984.
+
+ [2] ANSI, "Guidelines for the Specification of the Structure of the
+ Domain Specific Part (DSP) of the ISO Standard NSAP Address",
+ RFC-982, ANSI Working Document X3S3.3/85-258, April 1986.
+
+ [3] ISO, Draft International Standard 8348/DAD2, "Information
+ Processing Systems -- Data Communications -- Network Service
+ Definition, Addendum 2 Covering Network Layer Addressing", RFC-
+ 941, April 1985.
+
+ [4] Reynolds, J. and J. Postel, "Assigned Numbers", RFC-1010,
+ USC/Information Sciences Institute, May 1987.
+
+ [5] Callon, R. and H. W. Braun, "Working Draft -- Guidelines for the
+ use of Internet-IP addresses in the ISO Connectionless-Mode
+ Network Protocol," RFC-986, June 1986.
+
+ [6] ISO TC97/SC6/WG2 working document, "Intermediate System to
+ Intermediate System Intra-Domain Routing Exchange Protocol".
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