RFC 3642 (rfc3642) - Page 2 of 13

Common Elements of Generic String Encoding Rules (GSER) Encodings

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RFC 3642           Common Elements of GSER Encodings        October 2003


1.  Introduction

   The Generic String Encoding Rules (GSER) [7] define a human readable
   text encoding, based on ASN.1 [8] value notation, for an ASN.1 value
   of any ASN.1 type.  Specifications making use of GSER may wish to
   provide a non-normative equivalent ABNF [3] description of the GSER
   encoding for a particular ASN.1 type as a convenience for
   implementors unfamiliar with ASN.1.  This document supports such
   specifications by providing equivalent ABNF for the GSER encodings
   for ASN.1 types that commonly occur in LDAP [10] or X.500 [11]
   attribute and assertion syntaxes, as well as equivalent ABNF for the
   GSER encodings for the ASN.1 built-in types.

   The ABNF given in this document does not replace or alter GSER in any
   way.  If there is a discrepancy between the ABNF specified here and
   the encoding defined by GSER [7], then GSER is to be taken as
   definitive.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", and "MAY" in this document are
   to be interpreted as described in BCP 14, RFC 2119 [1].  The key word
   "OPTIONAL" is exclusively used with its ASN.1 meaning.

3.  Separators

   Certain separators are commonly used in constructing equivalent ABNF
   for SET and SEQUENCE types.

      sp  =  *%x20  ; zero, one or more space characters
      msp = 1*%x20  ; one or more space characters

      sep = [ "," ]

   The  rule is used in the ABNF description of the encoding for
   ASN.1 SET or SEQUENCE types where all the components are either
   OPTIONAL or DEFAULT.  It encodes to an empty string if and only if
   the immediately preceding character in the encoding is "{", i.e., it
   is only empty for the first optional component actually present in
   the SET or SEQUENCE value being encoded.

4.  ASN.1 Built-in Types

   This section describes the GSER encoding of values of the ASN.1
   built-in types, except for the restricted character string types.





Legg                         Informational
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