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7 Network Working Group J. Myers
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8 Request for Comments: 2088 Carnegie Mellon
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9 Cateogry: Standards Track January 1997
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10
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11
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12 IMAP4 non-synchronizing literals
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13
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14 Status of this Memo
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15
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16 This document specifies an Internet standards track protocol for the
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17 Internet community, and requests discussion and suggestions for
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18 improvements. Please refer to the current edition of the "Internet
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19 Official Protocol Standards" (STD 1) for the standardization state
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20 and status of this protocol. Distribution of this memo is unlimited.
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21
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22 1. Abstract
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23
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24 The Internet Message Access Protocol [IMAP4] contains the "literal"
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25 syntactic construct for communicating strings. When sending a
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26 literal from client to server, IMAP4 requires the client to wait for
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27 the server to send a command continuation request between sending the
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28 octet count and the string data. This document specifies an
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29 alternate form of literal which does not require this network round
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30 trip.
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31
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32 2. Conventions Used in this Document
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33
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34 In examples, "C:" and "S:" indicate lines sent by the client and
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35 server respectively.
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36
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37 3. Specification
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38
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39 The non-synchronizing literal is added an alternate form of literal,
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40 and may appear in communication from client to server instead of the
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41 IMAP4 form of literal. The IMAP4 form of literal, used in
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42 communication from client to server, is referred to as a
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43 synchronizing literal.
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44
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45 Non-synchronizing literals may be used with any IMAP4 server
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46 implementation which returns "LITERAL+" as one of the supported
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47 capabilities to the CAPABILITY command. If the server does not
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48 advertise the LITERAL+ capability, the client must use synchronizing
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49 literals instead.
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50
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51 The non-synchronizing literal is distinguished from the original
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52 synchronizing literal by having a plus ('+') between the octet count
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53 and the closing brace ('}'). The server does not generate a command
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54 continuation request in response to a non-synchronizing literal, and
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55
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56
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57
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58 Myers Standards Track [Page 1]
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59
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60 RFC 2088 LITERAL January 1997
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61
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62
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63 clients are not required to wait before sending the octets of a non-
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64 synchronizing literal.
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65
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66 The protocol receiver of an IMAP4 server must check the end of every
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67 received line for an open brace ('{') followed by an octet count, a
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68 plus ('+'), and a close brace ('}') immediately preceeding the CRLF.
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69 If it finds this sequence, it is the octet count of a non-
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70 synchronizing literal and the server MUST treat the specified number
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71 of following octets and the following line as part of the same
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72 command. A server MAY still process commands and reject errors on a
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73 line-by-line basis, as long as it checks for non-synchronizing
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74 literals at the end of each line.
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75
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76 Example: C: A001 LOGIN {11+}
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77 C: FRED FOOBAR {7+}
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78 C: fat man
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79 S: A001 OK LOGIN completed
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80
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81 4. Formal Syntax
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82
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83 The following syntax specification uses the augmented Backus-Naur
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84 Form (BNF) notation as specified in [RFC-822] as modified by [IMAP4].
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85 Non-terminals referenced but not defined below are as defined by
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86 [IMAP4].
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87
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88 literal ::= "{" number ["+"] "}" CRLF *CHAR8
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89 ;; Number represents the number of CHAR8 octets
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90
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91 6. References
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92
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93 [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4",
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94 draft-crispin-imap-base-XX.txt, University of Washington, April 1996.
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95
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96 [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text
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97 Messages", STD 11, RFC 822.
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98
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99 7. Security Considerations
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100
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101 There are no known security issues with this extension.
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102
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103 8. Author's Address
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104
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105 John G. Myers
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106 Carnegie-Mellon University
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107 5000 Forbes Ave.
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108 Pittsburgh PA, 15213-3890
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109
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110 Email: jgm+@cmu.edu
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111
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112
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113
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114 Myers Standards Track [Page 2]
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115
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