RFC 65 (rfc65) - Page 2 of 2
Comments on Host/Host Protocol document #1
Alternative Format: Original Text Document
RFC 65 Comments on Host-Host Protocol August 1970 bits to the right of the link in the leader. The IMP must preserve these bits and return them with RFNMs and the receiver must use the pseudo link instead of the link in RET and INR. The extra memory necessary to store the pseudo link in the NCP receive tables (which are indexed by link) and the link in the NCP send tables (which are indexed by pseudo link) is certainly less than the overhead necessary to maintain associative tables. Page 8. The allocate mechanism seems very inconvenient for the receive portion of the NCP to use. The receiver wants the allocation to be used up in units of the receiver's buffer size not in units of sender messages which may be variable length. Otherwise the receiver has a memory compaction problem. Page 9. The new irregular message to make the "cease" mechanism work are unnecessary, I think. The sender can keep track (probably with a one bit counter) of ALLs and GVBs and ignore GVB 0s for which resume ALLs have already arrived. This the receiver need not know whether the cease has been sent or not. Page 15. If I implemented an NCP, all ERRs would be treated like NOP. As an error control mechanism ERR is complicated and insufficient. Who wants to debug a complicated mechanism which only catches bugs due to the primary mechanism being undebugged. The one error control mechanism I would provide is a receive process to send process acknowledgment on every message. If this is not received for too long, the send process can send the message again if it has been saving it. This acknowledgment catches errors causing message loss at the process/NCP, NCP/NCP, Host/IMP, IMP/IMP, etc. levels. Currently the Host/IMP interface is particularly lacking in useful error controls. I wouldn't worry about kinds of errors check-sums are designed to pick up. If dropped and picked up bits ever become a problem either add hardware to more interfaces or let the receive process not send the process to process acknowledgment if a software checksum does not check. The page 3 and page 6 comments involve a change to the IMP program. I feel a tiny bit guilty suggesting changes I don't have to implement any more. However, I trust Crowther and Cosell will, as always, resist bad changes while making sensible ones. The page 9 comment is aimed at avoiding a change in the IMP program. [ This RFC was put into machine readable form for entry ] [ into the online RFC archives by Luke Hollins 8/99] Walden
