tcp-ip@ucbvax.ARPA (06/28/85)
From: hsw@TYCHO.ARPA (Howard Weiss) I have recently seen some strange behavior from the core gateways that I cannot understand or resolve. While receiving mail from BRL-TGR (and acking that mail), my host (TYCHO - 26.0.0.57) did not have the BRL gateway defined in its table. This meant that all packets for BRL-TGR were sent, by default, to the "smart" gateway otherwise known as the MIL-ARPA mail bridge gateway (26.0.0.106). Immediately, MIL-ARPA sent redirects back. One would normally think that the gateway would redirect to the BRL gateway (26.3.0.29), since that is the shortest path, but, that is NOT what happened. Instead, the MIL-ARPA gateway sent redirects to the MINET gateway (26.1.0.40). The MINET gateway, in turn, then sent back redirects to the BRL gateway. Does anyone have any good words or reasonings for this behavior? It would seem to me that MIL-ARPA should have redirected to the BRL gateway immediately. Howard Weiss -------
tcp-ip@ucbvax.ARPA (06/28/85)
From: Mike Brescia <brescia@bbnccv> (... 26.0.0.57 sending packets to BRL-TGR starting with 26.0.0.106) the MIL-ARPA gateway sent redirects to the MINET gateway (26.1.0.40). The MINET gateway, in turn, then sent back redirects to the BRL gateway. The reason for this is, while MILARPA and BRL are both gateways on the MILNET, MILARPA does not know about BRL, because BRL uses exterior gateway protocol (EGP) to pass around routing information, but the only gateways on MILNET which have EGP are MINET and AERO (26.8.0.65). The protocol used between 'core' gateways (e.g. MILARPA, MINET, AERO) does not carry the neighbor information about BRL from MINET to MILARPA, only the fact that the net is reachable. Current plans include putting EGP in some of the MILNET-ARPANET gateways so that routes from the ARPANET can reach local area nets off the MILNET without taking an extra hop through MINET or AERO. You should not have too much to worry about in your case, because when the redirects settle down, you do have the shortest route to BRL-TGR. It just takes 1 or 2 extra packets to get the (TCP) connection established. If your host were to save this information around between connections, you could eliminate even the first redirect in most exchanges. Mike Brescia
tcp-ip@ucbvax.ARPA (06/28/85)
From: hsw@TYCHO.ARPA (Howard Weiss) Mike, Thanks for the explanation of what is going on. Your answer was the only one that I could think of, but I thought that the core-gateways did have EGP. The problem on my host has now been fixed in that the BRL gateway is now defined and packets to the BRL net does NOT first get sent to MILARPA. thanks, Howard -------