Path: utzoo!attcan!uunet!husc6!bu-cs!kwe From: kwe@bu-cs.BU.EDU (kwe@bu-it.bu.edu (Kent W. England)) Newsgroups: comp.dcom.lans Subject: What about "brouters"? Summary: What about "brouters"? Message-ID: <25255@bu-cs.BU.EDU> Date: 6 Oct 88 16:47:33 GMT References: <281@fed.FRB.GOV> Reply-To: kwe@buit13.bu.edu (Kent England) Followup-To: comp.dcom.lans Organization: Boston Univ. Information Tech. Dept. Lines: 89 In article hedrick@athos.rutgers.edu (Charles Hedrick) writes: > [delete all the good design advice that you can't buy at any price, including a discussion about routing and bridging...] > >I understand that you'd feel safer with bridges that could handle most >of the bandwidth of an Ethernet. On the other hand, if they can >really handle 20 to 30%, that may well be good enough. The whole >point of a bridge is to increase overall capacity by separating local >and non-local traffic. You'd hope that even on a 100% loaded >Ethernet, no more than 20 to 30% of the traffic would be going to >destinations off the Ethernet. > cisco is now selling the Hybridge and I expect to see others soon offering similar products. For those not intimately familiar with the Hybridge and the brouter concept behind it: cisco has a MultiChannel Interface (MCI) card that will hold two Ethernet interfaces and two serial port interfaces (running from 2400 bps up to T1 and beyond). The MCI has a CPU and some memory on it. The CPU/memory can do routing and bridging on the card. The MCI card(s) go into a standard Multibus I chassis with a 680x0 CPU card, optional config memory card, and possibly other interface cards of various sorts. The whole kaboodle is a kind of multiprocessor architecture designed to bring very high throughputs to (some) of the packet paths in the "brouter". The throughput is needed to run real internet packet forwarding (like IP, DECnet, XNS, PUP, Appletalk, Chaos, and ISO CLNS/ES-IS) together with bridging software. This is cisco's idea of a brouter. The Hybridge is a small chassis with two slots and two cards; one MCI (limited to two ports only) and the 68020 CPU card. The Hybridge runs all the internet forwarding protocols and the Bridge software. The Hybridge is essentially a two port brouter. You can also run Bridge software on other multiport cisco routers by buying the Bridge software as an extra cost option. [End of marketing regurgitation.] Taking the Hybridge as a kind of "proof of concept" product, I expect to see similar devices from other vendors, so from this point on let me speak of "brouters" as boxes with capability similar to the Hybridge. cisco is claiming 12kpps [I assume minimum size packets] throughput between the two Ethernet interface ports on an MCI. Therefore, the alleged throughput of a Hybridge is 12kpps, a combination of routed and bridged packets. cisco makes no distinction between the throughput of routed versus bridged packets. Accepting these figures as indicative of actual operational performance, is there any reason why a brouter isn't a superior product over a router or a bridge? Prices are similar or less. I would expect to use a brouter to route all protocols that supported internetting, and selectively bridge protocols that were not able to be routed either because the vendor doesn't understand (like that Mass computer company whose president amuses us about twice a year with his outrageous witticisms) or because, like EtherTalk, the protocol isn't yet supported by the brouter vendor. I would expect the hardware performance needed for bridging to help speed up routing and the flexibility to selectively use bridging to temporarily solve problems with unroutable protocols would be far better than either routing or bridging alone. Should we be telling each other: "The router versus bridge wars are over. Buy brouters and make your decisions in software not hardware." ? And, finally, does anyone have first hand knowledge about the actual operational performance of the Hybridge? How do we measure that anyway? (I can't afford a lab full of HP analyzers :-) Please don't flame on me about the "route not bridge" or "bridge not route" dichotomy. I will argue that you have the choice with a brouter and that a software choice is better than a hardware choice. You can always fix your mistakes by hitting a software switch. You can also migrate from an all bridge to a router/bridge configuration much more easily. Please, let's assume for the sake of argument that hardware performance is actually in the range of 10kpps (unless you are going to say that you know that the Hybridge doesn't cut it and that nothing else will either). Dr. Hedrick, what is your opinion? Do you think that brouters have a future? I could see them helping rcd@fed.frb.gov migrate his network to a routing network. Do you? Kent England, Boston University