21602MR@MSU.BITNET (Mark Rosenberg) (10/22/90)
I am re-zoning some Macs onto a star controller and using a shiva net bridge to go into the building appletalk backbone. The question I have concerns a couple of optimization decisions I need to make... The building appletalk backbone sends everybody (50 macs) down into the basmnt into star controllers which are then plugged into the backbone, so currently everybody *sees* everybody else through broadcast and also printing packets, right ? I am under the impression that all this traffic (there is a consider able amount of printing that goes on) slows mac down because they need to liste n to the net ? Well I'd like to put a bridge between our star controller and the building backbone, but some people on our star will have to go outside it to print since we can't capture a laser and we can't afford to buy another one at this time. We also have a server that will be on our star. I am wondering what the impact of bridging our star will be and if people have to go across zones to print will it still be useful ? Any info or reference on how the mechanics of appletalk,stars,bridges,etc work would be greatly appreciated... Thanks, Mark Rosenberg
woody@ucscb.UCSC.EDU (Bill Woodcock) (10/23/90)
> I am re-zoning some Macs onto a star controller > and using a shiva net bridge to go into the > building appletalk backbone. The question I have > concerns a couple of optimization decisions I need > to make... > > The building appletalk backbone sends everybody > (50 macs) down into the basmnt into star > controllers which are then plugged into the > backbone, so currently everybody *sees* everybody > else through broadcast and also printing packets, > right ? I am under the impression that all this > traffic (there is a consider able amount of > printing that goes on) slows mac down because they > need to liste n to the net ? Well I'd like to put > a bridge between our star controller and the > building backbone, but some people on our star > will have to go outside it to print since we can't > capture a laser and we can't afford to buy another > one at this time. We also have a server that will > be on our star. I am wondering what the impact of > bridging our star will be and if people have to go > across zones to print will it still be useful ? > Any info or reference on how the mechanics of > appletalk,stars,bridges,etc work would be greatly > appreciated... > > Thanks, Mark Rosenberg As I understand it, you're considering implementing the following: +----------------+ +----------------+ | "A" | | "B" | | LocalTalk Zone | | LocalTalk Zone | | with printer. | | with server. | | | | | +----------------+ +----------------+ | | +-----------+ +-----------+ | "A" | | "B" | | NetBridge | | NetBridge | | | | | +-----------+ +-----------+ | | | LocalTalk Backbone Zone "C" | ====================================================================== The problem inherent in this is that it does very little to reduce the amount of traffic in any location. Suppose someone in zone "A" wants to print. No problem, NetBridge "A" filters the traffic, and nobody in zones "B" or "C" can see it. Now suppose this person in zone "A" wants to mount your AppleShare server. The server s in zone "B", so NetBridge "A" passes the traffic through to zone "C", and NetBridge "B" passes it on to zone "B". Thus all three zones see the traffic from this transaction, and nobody benefits. In fact, things are slowed down considerably by the presence of the backbone and the second NetBridge. The solution is to move your network services onto the backbone, as follows: +----------------+ +----------------+ | "A" | | "B" | | LocalTalk Zone | | LocalTalk Zone | | users only. | | users only. | | | | | +----------------+ +----------------+ | | +-----------+ +-----------+ +-----------+ +-----------+ | "A" | | | | | | "B" | | NetBridge | | Printer | | Server | | NetBridge | | | | | | | | | +-----------+ +-----------+ +-----------+ +-----------+ | | | | | | | | ====================================================================== LocalTalk Backbone Zone "C" This way, when someone in zone "A" wants to print or mount a server, NetBridge "A" passes the traffic into zone "C" where the printer and server are located, but NetBridge "B" hides the traffic from the users in zone "B". The converse holds true for users in zone "B". The only problem remaining is that the printer and the server still see everyone's packets. This won't bother the printer too much, and one would assume that your server is already running on one of your fastest CPUs. The way to fix this final problem of backbone traffic is Ethernet. Most companies seem to establish an Ethernet backbone after they've got three or four zones. It's more expensive than LocalTalk, but the throughput is more than worth the expense. -Bill Woodcock NetAdmin, Berkeley Macintosh Users Group