3.2 Ihave/Sendme

     ihave <message ID list> <remotesys>
     sendme <message ID list> <remotesys>

This message is part of the "ihave/sendme" protocol, which allows one site (say "A") to tell another site ("B") that a particular message has been received on A. Suppose that site A receives article "ucbvax.1234", and wishes to transmit the article to site B. A sends the control message "ihave ucbvax.1234 A" to site B (by posting it to newsgroup "to.B"). B responds with the control message "sendme ucbvax.1234 B" (on newsgroup to.A) if it has not already received the article. Upon receiving the Sendme message, A sends the article to B.

This protocol can be used to cut down on redundant traffic between sites. It is optional and should be used only if the particular situation makes it worthwhile. Frequently, the outcome is that, since most original messages are short, and since there is a high overhead to start sending a new message with UUCP, it costs as much to send the Ihave as it would cost to send the article itself.

One possible solution to this overhead problem is to batch requests. Several message ID's may be announced or requested in one message. If no message ID's are listed in the control message, the body of the message should be scanned for message ID's, one per line.