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116 lines
4.0 KiB
Plaintext
116 lines
4.0 KiB
Plaintext
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Network Working Group J. Myers
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Request for Comments: 2088 Carnegie Mellon
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Cateogry: Standards Track January 1997
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IMAP4 non-synchronizing literals
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Status of this Memo
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This document specifies an Internet standards track protocol for the
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Internet community, and requests discussion and suggestions for
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improvements. Please refer to the current edition of the "Internet
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Official Protocol Standards" (STD 1) for the standardization state
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and status of this protocol. Distribution of this memo is unlimited.
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1. Abstract
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The Internet Message Access Protocol [IMAP4] contains the "literal"
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syntactic construct for communicating strings. When sending a
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literal from client to server, IMAP4 requires the client to wait for
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the server to send a command continuation request between sending the
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octet count and the string data. This document specifies an
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alternate form of literal which does not require this network round
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trip.
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2. Conventions Used in this Document
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In examples, "C:" and "S:" indicate lines sent by the client and
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server respectively.
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3. Specification
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The non-synchronizing literal is added an alternate form of literal,
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and may appear in communication from client to server instead of the
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IMAP4 form of literal. The IMAP4 form of literal, used in
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communication from client to server, is referred to as a
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synchronizing literal.
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Non-synchronizing literals may be used with any IMAP4 server
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implementation which returns "LITERAL+" as one of the supported
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capabilities to the CAPABILITY command. If the server does not
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advertise the LITERAL+ capability, the client must use synchronizing
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literals instead.
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The non-synchronizing literal is distinguished from the original
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synchronizing literal by having a plus ('+') between the octet count
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and the closing brace ('}'). The server does not generate a command
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continuation request in response to a non-synchronizing literal, and
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Myers Standards Track [Page 1]
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RFC 2088 LITERAL January 1997
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clients are not required to wait before sending the octets of a non-
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synchronizing literal.
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The protocol receiver of an IMAP4 server must check the end of every
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received line for an open brace ('{') followed by an octet count, a
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plus ('+'), and a close brace ('}') immediately preceeding the CRLF.
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If it finds this sequence, it is the octet count of a non-
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synchronizing literal and the server MUST treat the specified number
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of following octets and the following line as part of the same
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command. A server MAY still process commands and reject errors on a
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line-by-line basis, as long as it checks for non-synchronizing
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literals at the end of each line.
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Example: C: A001 LOGIN {11+}
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C: FRED FOOBAR {7+}
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C: fat man
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S: A001 OK LOGIN completed
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4. Formal Syntax
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The following syntax specification uses the augmented Backus-Naur
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Form (BNF) notation as specified in [RFC-822] as modified by [IMAP4].
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Non-terminals referenced but not defined below are as defined by
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[IMAP4].
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literal ::= "{" number ["+"] "}" CRLF *CHAR8
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;; Number represents the number of CHAR8 octets
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6. References
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[IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4",
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draft-crispin-imap-base-XX.txt, University of Washington, April 1996.
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[RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text
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Messages", STD 11, RFC 822.
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7. Security Considerations
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There are no known security issues with this extension.
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8. Author's Address
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John G. Myers
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Carnegie-Mellon University
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5000 Forbes Ave.
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Pittsburgh PA, 15213-3890
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Email: jgm+@cmu.edu
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Myers Standards Track [Page 2]
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