Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!mit-eddie!genrad!decvax!ucbvax!GUNTER-ADAM.ARPA!AFDDN.TCP-IP From: AFDDN.TCP-IP@GUNTER-ADAM.ARPA.UUCP Newsgroups: mod.protocols.tcp-ip Subject: Re: Packet network reliability Message-ID: <8703312012.AA25019@ucbvax.Berkeley.EDU> Date: Tue, 31-Mar-87 15:01:02 EST Article-I.D.: ucbvax.8703312012.AA25019 Posted: Tue Mar 31 15:01:02 1987 Date-Received: Thu, 2-Apr-87 06:11:56 EST References: Sender: daemon@ucbvax.BERKELEY.EDU Distribution: world Organization: The ARPA Internet Lines: 28 Approved: tcp-ip@sri-nic.arpa I'm in the same boat with Dave; VC versus datagram is one of my buttons. I'm much more familiar with the BBN way of doing things than with PDNs. I can see where PDNs would want to have very tight control over everything going on in the network. Tightly binding resources in a single virtual path through the network does let you know what resources are going where and for how long. I think it also tends to stabilize network delays around some median which might be nice. You can also establish stable (fixed) routing. Some nets I believe have a single route source that has global knowledge of the network and returns routes to the net nodes for every connection request. The disadvantage I see is that every VC will use up a given amount of net resources whether data is actually being transmitted across the VC or not. In the cases where static routing is downloaded from a central site, the survivability of the network as a whole is only as good as that of the central site. BBN gets around these two disadvantages at a cost. The Milnet for instance is gettingvery large, very fast. I don't know the formula for computing the amount of bandwidth required for the internal routing updates, but I would suspect it would go up exponentially with the number of nodes(and connectivity of them). If anybody knows the numbers I'd like to have them. The current limit of 256 nodes on one network has already been reached for Milnet. They nodes aren't installed and operational yet, but the addresses have been allocated to future nodes. And even with the size of the backbone, there are nodes with 12-18 hosts connected or slated for connection. Maybe we need "butter" switches? Darrel B. -------