Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site amdcad.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!amdcad!phil From: phil@amdcad.UUCP (Phil Ngai) Newsgroups: net.dcom,net.lan Subject: Re: Digital LANBridge-100 survey results Message-ID: <11798@amdcad.UUCP> Date: Mon, 26-May-86 13:50:53 EDT Article-I.D.: amdcad.11798 Posted: Mon May 26 13:50:53 1986 Date-Received: Tue, 27-May-86 07:43:59 EDT References: <264@cucca.UUCP> Reply-To: phil@amdcad.UUCP (Phil Ngai) Organization: AMD, Sunnyvale, California Lines: 77 Keywords: ethernet Xref: watmath net.dcom:1947 net.lan:1520 In article <264@cucca.UUCP> cck@cucca.UUCP (Charlie C. Kim) writes: >Since I posted the original message, we received a LAN Bridge-100 and >installed it for testing; I include some information below. If you >need information on what the LAN Bridge-100 is and what it can do, see >the "Networks and Communications Buyer's Guide, 1986 January Edition" >from Digital, pp. 2.55-2.61. Ask your salesman for the current "Networks and Communications Buyer's Guide", they come out frequently and the Jan edition is out of date. >Basically, I should mention that the LAN Bridge-100 can be aptly >described as a "selective, adaptive repeater" between exactly two >ethernet segments. I think your use of the word "repeater" here is unfortunate as there is a specific meaning as to what an "Ethernet Repeater" is and the LANBridge 100 is not an "Ethernet Repeater". It is a bridge. >diable selected Bridge, black traffic, and look at statistics. "RBMS >uses the IEEE 802.3 managment protocol for use in both DECnet and >non-DECnet environments." No, it's IEEE 802.1 management protocol, not IEEE 802.3. >I'm not 100% clear on the number of segments you can connect. DEC >says "When planning an extended LAN, Digital recommends configuring a >maximum of seven Bridges in a series. This figure insures the >performance of time critical protocols. There is no restriction on >the number of Bridges when time critical protocols are not an issue. >An extended LAN consisting of 8,000 node addresses and spanning up to >22,400 meters can be constructed by using the Bridge." Well, the >confusing part to me is the last sentence. The 8000 node limit is >understandable - this is the memory in the LANBridge for node >addresses. The confusing part is 22,400 meter part - exactly what do >they mean by this? That this is the maximum? If so, why? I talked to engineers at Digital who confirmed my understanding of the above paragraph. Because the LANBridge 100 operates in a store and forward mode, each pass through one adds delay. The recommendation is that your network be designed such that any path only accumulates up to seven of these delays. A particular Ethernet can span 2800 meters, 2800 times 8 = 22,400. If delay is not important you can string an arbitrary number in series, subject to the 8K node limit. >the Bridge goes to a H4000 tap and the other goes to a DELNI (which >happens to be tiered to 3 levels e.g. three DELNIs in the path). If >you get one - take a look at the LEDs in the back - two of them are >used to indicate traffic on each of ports. Could you describe this 3 level DELNI setup? I thought you couldn't cascade DELNIs, that is, attach a DELNI to a DELNI? >I'm still interested in hearing about realistic alternatives to the >LANBridge-100. (The only thing that comes close that I've heard of is >the Vitalink box, but that's really meant more for long-haul >connections and about double the price (I think)). Other things I've The Vitalink box is much slower. DEC says the LANBridge 100 runs at full Ethernet speed. Vitalink is limited to something like 224Kb per SIO with a four SIO max. >David Post at Siemens points out something that people should be >careful about. He warns that running another kind of Bridge in >parallel causes problems. I assume he means some protocol dependent >bridge since I don't know of a comparable product to DEC's. In DEC's (and many other people's) terminology, Bridges are by definition protocol independent. Perhaps you mean a router? -- Vote Yes on Proposition 51! Phil Ngai +1 408 749 5720 UUCP: {ucbvax,decwrl,ihnp4,allegra}!amdcad!phil ARPA: amdcad!phil@decwrl.dec.com