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