Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!topaz!hedrick From: hedrick@topaz.RUTGERS.EDU (Charles Hedrick) Newsgroups: comp.dcom.lans Subject: Re: Milking machine performance/function Message-ID: <7432@topaz.RUTGERS.EDU> Date: Tue, 2-Dec-86 11:37:58 EST Article-I.D.: topaz.7432 Posted: Tue Dec 2 11:37:58 1986 Date-Received: Tue, 2-Dec-86 20:24:07 EST References: <1612@batcomputer.tn.cornell.edu> Distribution: na Organization: Rutgers Univ., New Brunswick, N.J. Lines: 83 > Does Bridge understand UDP RIP yet? (I suspect Cisco still only uses > its own proprietary routing protocol.) Actually, at this instant Cisco will handle either EGP or the PUP GWINFO (the PUP version of RIP). They are being very careful about testing their own protocol before turning it on in customer copies. As I understand it, they do not regard it as proprietary, and have considered issuing an RFC. (One might well describe routed as proprietary, since it is not described by an RFC. You have to figure it out from looking at source files. Under your license agreement, you can't divulge the information that you have obtained, though I suspect that this is being a bit more picky than they had in mind.) There are several problems with routed that make it unlikely that it will take over as a routing protocol. One is that in large networks, the algorithms behind RIP can lead to instability. It's unclear to me how many real networks have configurations that would lead to problems, but Cisco and similar companies would like their boxes to be usable to build networks on the scale of the Arpanet. (NSFnet and a number of regional networks are creating a market for routers that can handle big networks.) A more practical problem is that routed is largely a Unix-only protocol. If all your machines and gateways are BSD, fine. But we find it more practical to use other techniques to distribute routing. The most common ways to distribute routing information are routing redirects and proxy ARP. To use routing redirects, you set up a default gateway for each host. (It is common to have a convention that host number 1 on each subnet is a gateway.) If that gateway turns out not to be on the best route, it will issue an ICMP redirect pointing you to the better route. To use proxy ARP, you set things up so that your host issues an ARP request for every destination. The appropriate gateway responds to the ARP with its own Ethernet address. Routing redirects are probably the most common. Their use is described in the standards. Every TCP/IP implementation that I know of can use them. Proxy ARP is used primarily to handle hosts that do not understand subnetting on a subnetted network. However if you prefer not to wire in knowledge of a gateway to each host, you can also use this as your primary method for distributing routing. This method will always work for handling the subnet problem, but many host can't be told to ARP destinations on other networks. Bridge terminal servers are set up to use routing redirects. You can set a default gateway, and they obey ICMP redirects. I don't know anything about Bridge gateways, but I'd be real surprised if they didn't issue redirects when appropriate. Cisco terminal servers and gateways can use either technique. You can set a default gateway, and they will obey ICMP redirects. The terminal servers (but not gateways, I think) will also issue ARP's when they can't find any other way to get to a destination, even if it is on a different network. The gateways will issue redirects when appropriate, and will also handle proxy ARP. As far as I know, Berkeley Unix will not issue redirects when used as a gateway, but it will obey them when used as a host. It will also not respond to ARP requests for other networks when used as a gateway, but can be made to issue them when used as a host. In my opinion, this make Unix perfectly well-behaved as a host, but rules it out for use as a gateway, except in a network where you know you will never have any hosts other than Unix machines. (These comments are certainly true for 4.2. It is always possible that 4.3 has added code to issue redirects, though I haven't seen any sign of it in the announcements and other discussions on the net. I know that it hasn't added code to do proxy ARP, even though a number of sites have had to add it in order to bring up subnets.) As to your original question about milking machine performance: Bridge advertises their units for this purpose. We have used it in a small- scale way to front a PDP-11 and an IBM machine. It works. However the CS-100's, at least, are very short on memory. We have run into problems with machines when certain combinations of things are done with them. E.g. when the same machine is used as a milking machine and to drive a printer at high speed. Bridge has been working on these problems, and may have fixed it by now. Performance on connections when they are used this way is fine. You can certainly disable flow control. I've never seen any problem with welcoming banners, etc., but can't swear to the exact configurations we use. We've never measured throughput, but terminals look like they are running at full speed. Cisco does not advertise their equipment for use this way, but both they and we think they would work, at least up to some number of ports. There are things about the Bridge design that might make them slightly better, except for the dratted memory shortage.