TCP IP Illustrated

Valid values are the two strings us ascii and iso

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Unformatted text preview: 3 18:50:27 -0400 ehlo sun.tuc.noao.edu 500 Command unrecognized rset 250 Reset state file:///D|/Documents%20and%20Settings/bigini/Doc...omenet2run/tcpip/tcp-ip-illustrated/smtp_sim.htm (16 of 23) [12/09/2001 14.47.52] Chapter 28. SMTP: Simple Mail Transfer Protocol Instead of receiving a 250 reply to the EHLO command, the client receives a 500 reply. The client should then issue the RSET command, followed by a HELO command. Header Changes: Non-ASCII Characters RFC 1522 [Moore 1993] specifies a way to send non-ASCII characters in RFC 822 message headers. The main use of this is to allow additional characters in the sender and receiver names, and in the subject. The header fields can contain encoded words. They have the following format: =? charset ? encoding ? encoded-text ?= charset is the character set specification. Valid values are the two strings us-ascii and iso-8859-X, where X is a single digit, as in iso-8859-1. encoding is a single character to specify the encoding method. Two values are supported. 1. Q encoding means quoted-printable, and is intended for Latin character sets. Most characters are sent as NVT ASCII (with the high-order bit set to 0, of course). Any character to be sent whose eighth bit is set is sent instead as three characters: first the character =, followed by two hexadecimal digits. For example, the character *e* (whose binary 8-bit value is 0xe9) is sent as the three characters =E9. Spaces are always sent as either an underscore or the three characters =20. This encoding is intended for text that is mostly ASCII, with a few special characters. 2. B means base-64 encoding. Three consecutive bytes of text (24 bits) are encoded as four 6-bit values. The 64 NVT ASCII characters used to represent each of the possible 6-bit values are shown in Figure 28.6. 6-bit value ASCII char 6-bit value ASCII char 6-bit value ASCII char 6-bit value ASCII char 0 A 10 Q 20 g 30 w 1 B 11 R 21 h 31 x 2 C 12 S 22 i 32 y 3 D 13 T 23 j 33 z 4 E 14 U 24 k 34 0 5 F 15 V 25 l 35 1 6 G 1...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.

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