RFC 516 (rfc516) - Page 2 of 2
Lost message detection
Alternative Format: Original Text Document
RFC 516 LOST MESSAGE DETECTION May 1973
hosts is set to zero.
Each time a message is sent the current send message number is
entered into a field in the message header, and the current send
message number is incremented (modulo N, say N=256)
Each time a message is received the message number from the
message is compared to the current receive message number and:
if the received message is the expected one then the message
is acceptable and current receive message number is
incremented (modulo N);
if the received message is not the expected one then a
message has been lost.
What to do when a missing message is detected, not clear, but at
least can be logged and reported to the network control center. A
missing message may not be fatal to an interactive conversation, but
it is critical in a file transfer, thus I suggest that missing
messages which are not recovered be cause to close the conversation.
The third scheme:
Host to host acknowledgements could be required. Such an
acknowledgement scheme could be implemented similarly to the IMP to
IMP scheme. This is a serious change to the current protocols so I
will not elaborate on it here, feeling that deeper study will be
necessary to fully specify a reasonable host to host acknowledgement
strategy.
Of these three suggestions the first is the most immediately practical
and implementable; in fact several hosts all ready do this. These
schemes also are non-conflicting, they could be implemented and used
simultaneously.
[ This RFC was put into machine readable form for entry ]
[ into the online RFC archives by Alex McKenzie with ]
[ support from GTE, formerly BBN Corp. 9/99 ]
Postel