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1.1 ! root 1: \documentstyle [tgrind,ucl-rn] {article} ! 2: \rnnumber{RN/89/14} ! 3: \author {S.E. Kille} ! 4: \date {\today} ! 5: \title {A string encoding of Presentation Address} ! 6: \begin {document} ! 7: \bibliographystyle{alpha} ! 8: \maketitle ! 9: \begin {abstract} ! 10: There are a number of environments where a simple string encoding of ! 11: Presentation Address is desirable. ! 12: This specification is agreed for use in the ISODE and THORN projects, and ! 13: may be of wider interest. ! 14: This document is also THORN Document UCL-59. ! 15: \end {abstract} ! 16: ! 17: \section {Introduction} ! 18: ! 19: There is a need to represent presentation addresses as strings in a number ! 20: of different contexts. ! 21: This note is defines a unified syntax for the THORN and ISODE ! 22: projects, which might also ! 23: be appropriate as a de facto standard for a wider community. ! 24: ! 25: Christian Huitema or Inria and Marshall Rose or The Wollongong Group gave ! 26: much useful input to this document. ! 27: ! 28: \section {Requirements} ! 29: ! 30: The main requirements are: ! 31: ! 32: \begin {itemize} ! 33: \item Must be able to specify any legal value ! 34: \item Should be clean in the common case of no selectors ! 35: \item Needs to deal with selectors in the following encodings: ! 36: \begin {itemize} ! 37: \item IA5 ! 38: \item Digits encoded as IA5 (this is the most common syntax in ! 39: Europe, as it is required by X.400(84) and should receive an optimal ! 40: encoding) ! 41: \item Numeric encoded as integer (US GOSIP). This is mapped onto two ! 42: octets, with the first octet being the high order byte of the integer. ! 43: \item General Hexadecimal ! 44: \end {itemize} ! 45: ! 46: \item Should give special encodings for the ad hoc encoding proposed ! 47: in ``An interim approach to use of Network Addresses'' \cite{NSAP.Approach}. ! 48: \begin {itemize} ! 49: \item X.25(80) Networks ! 50: \item TCP/IP Networks ! 51: \end {itemize} ! 52: ! 53: \item Should be extensible for additional forms ! 54: ! 55: \item Should provide a compact representation (e.g., for use in a TSEL ! 56: encoding). ! 57: ! 58: \end {itemize} ! 59: ! 60: \section {Format} ! 61: ! 62: The BNF is given in figure \ref{bnf}. ! 63: ! 64: \tagrindfile{bnf}{String BNF}{bnf} ! 65: ! 66: Four examples: ! 67: ! 68: \begin {verbatim} ! 69: "256"/NS+a433bb93c1|NS+aa3106 ! 70: ! 71: #63/#41/#12/X121+234219200300 ! 72: ! 73: '3a'H/TELEX+00728722+X.25(80)+02+00002340555+CUDF+"892796" ! 74: ! 75: TELEX+00728722+RFC-1006+03+10.0.0.6 ! 76: ! 77: \end{verbatim} ! 78: ! 79: Note that the RFC 1006 encoding permits use of either domain or IP address. ! 80: The former is primarily for ease of entry. If this domain maps onto multiple IP ! 81: addresses, then multiple network addresses should be generated. When ! 82: mapping from an encoded address to string form, the reverse mapping (dotted quad to domain) ! 83: should not be used. ! 84: ! 85: \section {Encoding} ! 86: ! 87: Selectors are represented in a manner which can be easily encoded. ! 88: In the NS notation, the concrete binary form of network address is given. ! 89: Otherwise, this string notation provides a mechanism for representing ! 90: the Abstract ! 91: Syntax of a Network Address. This must be encoded according to Addendum 2 ! 92: of ISO 8348. ! 93: ! 94: \section {Macros} ! 95: ! 96: There are often common addresses, for which a cleaner representation is ! 97: desired. This is achieved by use of Macros. If a \verb|<network-address>| ! 98: can be parsed ! 99: as: ! 100: ! 101: \begin {verbatim} ! 102: <otherstring> "=" *( any ) ! 103: \end{verbatim} ! 104: ! 105: Then the leading string is taken as a Macro, which is substituted. ! 106: This may be applied recursively. When ! 107: presenting Network Address to humans, the longest available substitution ! 108: should be used. For example: ! 109: ! 110: \begin {center} ! 111: \begin {tabular}{|l|l|} ! 112: \hline ! 113: Macro & Value \\ ! 114: \hline ! 115: UK.AC & DCC+826+d110000 \\ ! 116: Leeds & UK.AC=120 \\ ! 117: \hline ! 118: \end {tabular} ! 119: ! 120: \end {center} ! 121: ! 122: Then ``Leeds=22'' would be expanded to ``DCC+826+d11000012022''. ! 123: ! 124: ! 125: \section {Standard Macros} ! 126: ! 127: No Macros should ever be relied on. However, the following are suggested as ! 128: standard. ! 129: ! 130: \begin {center} ! 131: \begin {tabular}{|l|l|} ! 132: \hline ! 133: Macro & Value \\ ! 134: \hline ! 135: Int-X25(80) & TELEX+00728722+X25(80)+01+ \\ ! 136: Janet-X25(80) & TELEX+00728722+X25(80)+02+ \\ ! 137: Internet-RFC-1006 & TELEX+00728722+RFC-1006+03+ \\ ! 138: \hline ! 139: \end {tabular} ! 140: ! 141: \end {center} ! 142: ! 143: \section {References} ! 144: ! 145: \bibliography {../../../bib/sek} ! 146: ! 147: \end {document}
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