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+Network Working Group S.E. Hardcastle-Kille
+Requests for Comments 1278 University College London
+ November 1991
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+ A string encoding of Presentation Address
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+Status of this Memo
+ This memo provides information for the Internet community. It
+ does not specify an Internet standard. Distribution of this memo
+ is unlimited.
+
+Abstract
+ There are a number of environments where a simple string encoding
+ of Presentation Address is desirable. This specification defines
+ such a representation.
+
+
+
+
+RFC 1278 String encoded P-Address November 1991
+
+
+1 Introduction
+
+OSI Application Entities use presentation addresses to address other
+Application Entities. The model for this is defined in [ISO87b].
+Presentation addresses are stored in the OSI Directory using an ASN.1
+representation defined by the OSI Directory [CCI88]. Logically, a
+presentation address consists of:
+
+
+ o A presentation selector
+
+ o A session selector
+
+ o A transport selector
+
+ o A set of network addresses
+
+The selectors are all octet strings, but often have IA5 character
+representations. The format of network addresses is defined in
+[ISO87a].
+There is a need to represent presentation addresses as strings in a
+number of different contexts. This Internet Draft defines a format
+for use on the Internet. It is for display to human users, and its
+use is recommended whenever this needs to be done. Typically, this
+will be for system managers rather than for end users. It is not
+intended for internal storage.
+
+This Internet Draft was originally published as UCL Research Note
+RN/89/14 [Kil89]. It was agreed as a unified syntax for the THORN and
+ISODE projects. It is used throughout ISODE.
+Christian Huitema of Inria and Marshall Rose of PSI Inc. gave much
+useful input to this document.
+
+
+2 Requirements
+
+The main requirements are:
+
+
+ o Must be able to specify any legal value.
+
+ o Should be clean in the common case of the presentation address
+ containing network addresses and no selectors.
+
+
+Hardcastle-Kille Page 1
+
+
+
+
+RFC 1278 String encoded P-Address November 1991
+
+
+ o Must deal with selectors in the following encodings:
+
+ -- IA5
+
+ -- Decimal digits encoded as IA5 (this is the most common syntax
+ in Europe, as it is required by X.400(84) and should receive a
+ straightforward encoding)
+
+ -- Numeric encoded as a 16 bit unsigned integer (US GOSIP). This
+ is mapped onto two octets, with the first octet being the high
+ order byte of the integer.
+
+ -- General Hexadecimal
+
+ o Should give special encodings for the ad hoc encoding proposed in
+ ``An interim approach to use of Network Addresses'' [HK91].
+
+ -- X.25(80) Networks
+
+ -- TCP/IP Networks
+
+ o Should be extensible for additional forms.
+
+ o Should provide a reasonably compact representation .
+
+
+3 Format
+
+The_BNF_is_given_in_figure_1.__________________________________________
+
+
+<digit> ::= [0-9]
+<other> ::= [0-9a-zA-Z+-.]
+<domainchar> ::= [0-9a-zA-Z-.]
+<hexdigit> ::= [0-9a-fA-F]
+<hexoctet> ::= <hexdigit> <hexdigit>
+<decimaloctet> ::= <digit> | <digit> <digit>
+ | <digit> <digit> <digit>
+
+<digitstring> ::= <digit> <digitstring> 10
+ | <digit>
+<otherstring> ::= <other> <otherstring>
+ | <other>
+
+
+Hardcastle-Kille Page 2
+
+
+
+
+RFC 1278 String encoded P-Address November 1991
+
+
+<domainstring> ::= <domainchar> <otherstring>
+ | <domainchar>
+<hexstring> ::= <hexoctet> <hexstring> | <hexoctet>
+
+<dotstring> ::= <decimaloctet> "." <dotstring>
+ | <decimaloctet> "." <decimaloctet>
+ 20
+
+
+<dothexstring> ::= <dotstring> | <hexstring>
+
+
+<presentation-address> ::=
+ [[[ <psel> "/" ] <ssel> "/" ] <tsel> "/" ]
+ <network-address-list>
+
+<network-address-list> ::= <network-address> "_" <network-address-list>30
+ | <network-address>
+
+<psel> ::= <selector>
+<ssel> ::= <selector>
+<tsel> ::= <selector>
+
+<selector> ::= '"' <otherstring> '"' -- IA5
+ -- For chars not in this
+ -- string use hex
+ | "#" <digitstring> -- US GOSIP 40
+ | "'" <hexstring> "'H" -- Hex
+ | "" -- Empty but present
+
+<network-address> ::= "NS" "+" <dothexstring>
+ -- Concrete Binary Representation
+ -- This is the compact encoding
+ | <afi> "+" <idi> [ "+" <dsp> ]
+ -- A user oriented form
+ | <idp> "+" <hexstring>
+ -- ISO 8348 Compatability 50
+
+<idp> ::= <digitstring> -
+
+<dsp> ::=
+ | "d" <digitstring> -- Abstract Decimal
+ | "x" <dothexstring> -- Abstract Binary
+ | "l" <otherstring> -- IA5: local form only
+
+Hardcastle-Kille Page 3
+
+
+
+
+RFC 1278 String encoded P-Address November 1991
+
+
+ | "RFC-1006" "+" <prefix> "+" <ip>
+ [ "+" <port> [ "+" <tset> ]]
+ | "X.25(80)" "+" <prefix> "+" <dte> 60
+ [ "+" <cudf-or-pid> "+" <hexstring> ]
+ | "ECMA-117-Binary" "+" <hexstring> "+" <hexstring>
+ "+" <hexstring>
+ | "ECMA-117-Decimal" "+" <digitstring> "+"
+ <digitstring> "+" <digitstring>
+
+<idi> ::= <digitstring>
+<afi> ::= "X121" | "DCC" | "TELEX" | "PSTN" | "ISDN"
+ | "ICD" | "LOCAL"
+ 70
+<prefix> ::= <digit> <digit>
+
+<ip> ::= <domainstring>
+ -- dotted decimal form (e.g., 10.0.0.6)
+ -- or domain (e.g., twg.com)
+<port> ::= <digitstring>
+<tset> ::= <digitstring>
+
+<dte> ::= <digitstring>
+<cudf-or-pid> ::= "CUDF" | "PID" 80
+
+
+________________________Figure_1:__String_BNF__________________________
+
+Four examples:
+
+
+"256"/NS+a433bb93c1_NS+aa3106
+
+#63/#41/#12/X121+234219200300
+
+'3a'H/TELEX+00728722+X.25(80)+02+00002340555+CUDF+"892796"
+
+TELEX+00728722+RFC-1006+03+10.0.0.6
+
+
+Note that the RFC 1006 encoding permits use of either a DNS Domain
+Name or an IP address. The former is primarily for ease of entry. If
+this DNS Domain Name maps onto multiple IP addresses, then multiple
+network addresses should be generated. The DNS Domain Name form is
+
+
+Hardcastle-Kille Page 4
+
+
+
+
+RFC 1278 String encoded P-Address November 1991
+
+
+for convenient input. When mapping from an encoded address to string
+form, the IP address form should always be used.
+
+
+4 Encoding
+
+Selectors are represented in a manner which can be easily encoded. In
+the NS notation, the concrete binary form of network address is given.
+Otherwise, this string notation provides a mechanism for representing
+the Abstract Syntax of a Network Address. This must be encoded
+according to Addendum 2 of ISO 8348 [ISO87a].
+
+
+5 Macros
+
+There are often common addresses, for which a cleaner representation
+is desired. This is achieved by use of Macros. If a
+<network-address> can be parsed as:
+
+
+<otherstring> "=" *( any )
+
+Then the leading string is taken as a Macro, which is substituted.
+This may be applied recursively. When presenting Network Address to
+humans, the longest available substitution should be used. For
+example:
+
+ ________________________
+ |_Macro_|Value__________ |
+ | UK.AC |DCC+826+d110000 |
+ |_Leeds_|UK.AC=120______ |
+
+Then ``Leeds=22'' would be expanded to ``DCC+826+d11000012022''.
+
+
+6 Standard Macros
+
+
+No Macros should ever be relied on. However, the following are
+suggested as standard.
+
+
+
+
+
+Hardcastle-Kille Page 5
+
+
+
+
+RFC 1278 String encoded P-Address November 1991
+
+ ________________________________________________
+ |_Macro_____________|Value______________________ |
+ | Int-X25(80) |TELEX+00728722+X25(80)+01+ |
+ | Janet-X25(80) |TELEX+00728722+X25(80)+02+ |
+ | Internet-RFC-1006 |TELEX+00728722+RFC-1006+03+ |
+ |_IXI_______________|TELEX+00728722+RFC-1006+06+_|
+
+7 References
+
+
+References
+
+[CCI88] The Directory --- overview of concepts, models and services,
+ December 1988. CCITT X.500 Series Recommendations.
+
+[HK91] S.E. Hardcastle-Kille. Encoding network addresses to support
+ operation over non-osi lower layers. Request for Comments
+ RFC 1277, Department of Computer Science, University College
+ London, November 1991.
+
+[ISO87a] Information processing systems - data communications -
+ network services definition: Addendum 2 - network layer
+ addressing, March 1987. ISO TC 97/SC 6.
+
+[ISO87b] ISO DIS 7498-3 on naming and addressing, May 1987.
+ ISO/IEC/JTC-1/SC 21.
+
+[Kil89] S.E. Kille. A string encoding of presentation address.
+ Research Note RN/89/14, Department of Computer Science,
+ University College London, February 1989.
+
+
+8 Security Considerations
+
+Security considerations are not discussed in this memo.
+
+
+9 Author's Address
+
+ Steve Hardcastle-Kille
+ Department of Computer Science
+ University College London
+ Gower Street
+ WC1E 6BT
+
+
+Hardcastle-Kille Page 6
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+RFC 1278 String encoded P-Address November 1991
+
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+ England
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+ Phone: +44-71-380-7294
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+ EMail: S.Kille@CS.UCL.AC.UK
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+Hardcastle-Kille Page 7
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