Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!image.soe.clarkson.edu!abstine
From: abstine@image.soe.clarkson.edu (Arthur Stine)
Newsgroups: comp.dcom.lans
Subject: Re: Do multiport repeaters buffer packets?
Message-ID: <1990Aug27.135439.9422@sun.soe.clarkson.edu>
Date: 27 Aug 90 13:54:39 GMT
References: <65056@yarra.oz.au>
Sender: abstine@sun.soe.clarkson.edu (Arthur Stine)
Organization: Clarkson University, Potsdam, NY
Lines: 45

From article <65056@yarra.oz.au>, by chris@yarra.oz.au (Chris Jankowski):
> 
> Most Ethernet and IEEE.802.3 LANs design guidelines recommend use
> of multiport repeaters to increase LAN robustness and manageability
> of fault finding.
> Assume an asymmetrical configuration in the sense that there is
> a large server on one segment and a large number of PCs talking to it.
> The PCs are distributed among the other ports hanging off the multiport
> repeater.
> Just consider the following example:
> Assume that N-1 PCs each on different Ethernet segment generates a packet
> directed to the server at the same time. Even if the server's Ethernet
> segment is quiet only one of those packets can be delivered at a time.
> What happens with the others? 
If they all generate a packet at the same time, they will all see a collision.
A MPR is a repeater, not a store-forward device. The server will see
exactly the same line activity as any of the PC's at the same instant
in time (relative to the propagation delay of the wire...)

> Does the N port repeater buffer the remaining frames?
No, it doesn't buffer any frames

> If not (and I believe that store and forward is a function of a bridge)
> what other strategy can a multiport repeater use?
It just repeats the bits, just like any other ethernet repeater. It is just
a multiport version ...

> Or am I missing something important altogether?
> 
> Thanks for your help.
> 
>       -m-------   Chris Jankowski - Senior Systems Engineer chris@yarra.oz{.au}
>     ---mmm-----   Pyramid Technology Corporation Pty. Ltd.  fax  +61 3 820 0536
>   -----mmmmm---   11th Floor, 14 Queens Road                tel. +61 3 820 0711
> -------mmmmmmm-   Melbourne, Victoria, 3004       AUSTRALIA       (03) 820 0711
> 
> micron n. - a unit of length of one milionth of a meter, 
>             worth $2,000,000,000 since the fault in the Hubble space telescope 
>             mirror has been identified.
-- 
Art Stine
Sr Network Engineer
Clarkson U
ABStine@CLVMS.Clarkson.Edu