RFC 1146 (rfc1146) - Page 1 of 5
TCP alternate checksum options
Alternative Format: Original Text Document
Network Working Group J. Zweig Request for Comments: 1146 UIUC Obsoletes: RFC 1145 C. Partridge BBN March 1990 TCP Alternate Checksum Options Status of This Memo This memo suggests a pair of TCP options to allow use of alternate data checksum algorithms in the TCP header. The use of these options is experimental, and not recommended for production use. Note: This RFC corrects errors introduced in the editing process in RFC 1145. Distribution of this memo is unlimited. Introduction Some members of the networking community have expressed interest in using checksum-algorithms with different error detection and correction properties than the standard TCP checksum. The option described in this memo provides a mechanism to negotiate the use of an alternate checksum at connection-establishment time, as well as a mechanism to carry additional checksum information for algorithms that utilize checksums that are longer than 16 bits. Definition of the Options The TCP Alternate Checksum Request Option may be sent in a SYN segment by a TCP to indicate that the TCP is prepared to both generate and receive checksums based on an alternate algorithm. During communication, the alternate checksum replaces the regular TCP checksum in the checksum field of the TCP header. Should the alternate checksum require more than 2 octets to transmit, the checksum may either be moved into a TCP Alternate Checksum Data Option and the checksum field of the TCP header be sent as 0, or the data may be split between the header field and the option. Alternate checksums are computed over the same data as the regular TCP checksum (see TCP Alternate Checksum Data Option discussion below). TCP Alternate Checksum Request Option The format of the TCP Alternate Checksum Request Option is: Zweig & Partridge
