Removal of the 30-Second Delay When Hosts Come Up (RFC0410)
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2019-Feb-12
Internet Society Requests For Comment (RFCs)
Network Working Group John M. McQuillan Request for Comments #410 Bolt Beranek and Newman NIC #12402 10 November 1972 Categories: B-1
Removal of the 30-Second Delay When Hosts Come Up -------------------------------------------------
The IMP currently delays accepting input from a Host for 30 seconds after the Host has come up. This delay serves to allow the fact that the Host is up to propagate through the network. The fundamental problem is that a Host must not be permitted to communicate with a second Host until the second Host (actually its IMP) has been made aware that the first Host is up. Otherwise, one Host may come up and send a "hello" message to another Host, whose reply is discarded by the IMP because it is for a dead destination.
All this reasoning is based on a dead destination de- tection mechanism at the source IMP. The 30-second delay is based on the worst-case propagation delay for routing information in the network, so that every potential source IMP can update its host up/down table. There are several drawbacks to this scheme:
1. Hosts should not have to wait the worst-case time of 30 seconds to send to Hosts at their IMP or nearby in the network.
2. The operation of half-duplex interfaces is made even more complicated because of the startup delay.
3. The timeout period of 30 seconds is really a function of network topology and we would like to be able to change it when necessary as the network expands.
We propose to eliminate the 30-second delay altogether. The IMP subnetwork will detect messages for a dead Host at the destination IMP instead of at the source IMP. There is no delay
involved for an IMP to sense when its own Hosts come up, so that it can always make the correct decision about whether to give a message to one of its Hosts or to return a destination dead message to the source Host. Under this new scheme, when- ever the IMP’s ready line is up it is ready to accept input from its Hosts without delay. Several comments on this change should...