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RFC 4824, "The Transmission of IP Datagrams over the Semaphore Flag Signaling System (SFSS)", April 2007

See Also: RFC 4824 w/ inline errata

Errata ID: 878
Status: Verified
Type: Technical
Publication Format(s) : TEXT

Reported By: Henrik Levkowetz
Date Reported: 2007-04-08
Verifier Name: Jogi Hofmueller
Date Verified: 2007-04-16

Section 3.4 says:

                   SFS       \0/     \0__     0/_     0/
                              |       |       |       |\
                             / \     / \     / \     / \
                              U       V       W       X
                   IP-SFS    ACK     KAL     NAK     RTR


                   SFS        0__     0__
                             /|       |\
                             / \     / \
                              Y       Z
                   IP-SFS    RTT    unused

It should say:

                   SFS       \0/     |0       0/_     0/
                              |       |\      |       |\
                             / \     / \     / \     / \
                              U       V       W       X
                   IP-SFS    ACK     KAL     NAK     RTR


                   SFS       \0__     0__
                              |       |\
                             / \     / \
                              Y       Z
                   IP-SFS    RTT    unused


The illustrated SFS for symbol 'Y', signifying control signal 'RTT',
is depicted as identical with symbol 'M', which signals nibble value
0x0C. This means that some implementations may break off receipt with
an error on receiving 0x0C and interpreting it as RTT, while others
may see RTT and interpret it as a spurious 0x0C, and ignore it.

References [JCroft, Wikipedia] gives a different way of signalling 'Y',
which does not coincide with any of the other symbols. This
discrepancy between the current specification and the references may
also result in both implementation and execution differences, as some
interfaces may already have signal 'Y' hard-coded according to [JCroft]
or [Wikipedia], which will result in transmission of an SFS which will
not be understood by an interface that follows the current specification

Author: Errors in the forms of SFS representation for SFS V/KAL and SFS Y/RTT.

from pending

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