Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!amdcad!ames!mailrus!cornell!uw-beaver!uoregon!jqj From: jqj@uoregon.uoregon.edu (JQ Johnson) Newsgroups: comp.dcom.lans Subject: Re: What about "brouters"? Message-ID: <2944@uoregon.uoregon.edu> Date: 8 Oct 88 14:45:53 GMT References: <281@fed.FRB.GOV> <25255@bu-cs.BU.EDU> Reply-To: jqj@drizzle.UUCP (JQ Johnson) Organization: University of Oregon, Computer Science, Eugene OR Lines: 23 Kent England argues that the cisco HyBridge is the appropriate model for defining a "brouter" i.e. a hybrid bridge-router. Though I agree that the HyBridge is a very nice product (I have one on order), I'm not sure you should call it a "brouter". RAD and others have been using the "brouter" term for some time now for a different beast -- a bridge that does some intelligent routing using only MAC-layer addresses. By comparison, the HyBridge does routing using network-layer addresses. The RAD product's intelligence is, as I recall, limited to traditional packet filtering, creation and regeneration of a spanning tree, and load sharing among multiple MAC-layer paths. One could imagine a very intelligent bridge that did still more; given a protocol that exchanged caches among bridges you could imagine doing true routing using only MAC-layer addresses! By the way, one major problem with the HyBridge model is figuring out how to incorporate such a partial bridge into a spanning tree of bridges. Seems to me the presence of a HyBridge would imply that the spanning tree algorithm would have to be extended to communicate the routing vs. bridging rules so everybody could agree. It would be disasterous to have a routing HyBridge in parallel with an active DEC LANBridge! I'm not convinced that HyBridge works in complex bridged topologies.