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Subject:	Re: Network Problems / Dropped VT Sessions
From:	Tom Emerson <[log in to unmask]>
Reply To:	Tom Emerson <[log in to unmask]>
Date:	Fri, 21 Mar 2003 13:10:31 -0800
Content-Type:	Text/Plain
Parts/Attachments:	Text/Plain (51 lines)

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On Friday 21 March 2003 12:52 pm, Atwood, Tim (DVM) wrote:
>
> We "think" the network problem was:
>
> A misconfigured hub. From what our network manager told me (again I am not
> enough of a network guru to confirm what he tells me).

Quick question: did he SPECIFICALLY say "hub", or could he have possibly said
"switch"?  [and if he said "hub", was he "dumbing down" his response?]

"hubs" are the equivalent of "dumb terminals", if you will -- anything that
comes in on a particular "node" gets blasted out all other nodes without
regard for what is actually there.

SWITCHES, on the other hand, try to take a more practical approach: for every
packet of data coming in, there is a source address and a destination
address.  If the switch doesn't know the destination, it acts like a hub and
blasts it to all outbound ports.  At the same time, it "remembers" the source
address of the packet, so when a packet is destined for that address, (e.g.,
the response to the original packet) the switch can send it on the one
pathway that is needed without bothering any other computers or destinations.

In other words, the statement:

> The hub had a duplicate node configured.

makes no sense -- ALL nodes are considered "duplicates" so far as a HUB is
concerned.  It WOULD make a difference to a switch, and I would expect the
"problem" that would occur would be a high "collision" rate as data races
along each path and eventually re-connects somewhere downstream [which would
be the case if you connected two or more ports of the same "hub" to several
ports on the same "switch" via cross-over cables -- not the brightest thing
to do, since technically it could cause problems like this one]

- --
Yet another Blog: http://osnut.homelinux.net
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