[SunRescue] LAN Commmunication (was Sparc 10 cover plates)

Gregory Leblanc GLeblanc at cu-portland.edu
Wed Dec 22 02:11:40 CST 1999

> -----Original Message-----
> From: Bjrn Ramqvist [mailto:brt at osk.sema.se]
> Sent: Tuesday, December 21, 1999 11:58 PM
> To: rescue at sunhelp.org
> Subject: [SunRescue] LAN Commmunication (was Sparc 10 cover plates)
> paul pries wrote:
> > 
> > > I don't think so...we have a small network 16 systems 
> here on Two SMC Hubs
> > > and we get local trafic at 8.8 - 9.1 Mbit/sec on ordenary 
> 10Mb/s network.
> > 
> > The worst case I've ever seen is a saturation
> > point of 3.8 Mbit/s. But
> > then again, this is exceptional. Lots of koax
> > segments, mulitport
> > repeaters, some hubs with their TP segments. No
> > switching at all, just
> > one logical segment with a lot of traffic...
> > No one had ever thought of doing a proper design,
> > no one had thought
> > of traffic patterns or what protocols they had
> > running.
> > It really was a mess.
> OK.
> "background" traffic increase when the amount of hosts increase.
> But, imagine in a switched LAN with multiple repeaters, switches,
> bridges, mediaconverters and all such things, they can't get rid of
> "all" traffic either, no?

True, but if you do your routing and "layer 3 switching" properly, then you
can keep it down to reasonable levels.  

> I was just thinking of when I was at one of our customers site, where
> they have hosts in the amount of "thousands". They sure is connecting
> through switches, but what I came to notice was that it was a huge
> amount of broadcast packets?
> I mean, imagine a WinNT network where EVERY machine thinks it needs to
> know EXACTLY where every machine is, it's status, it's wifes 
> name, it's
> social security number, the color of your dogs eyes and so on - this
> must be a problem. Just "keeping up" the LAN is almost 
> rendering itself
> useless.

<novell BIAS>
Is this an IP network, IPX, or something else?  All of the IPX/SPX networks
that I've inherited have been HORRIBLY misconfigured, causing some really
bad network performance.  However, if you take the time to set up every
device properly when you put it on the network, routed IPX can be really
fast.  No decent Unix implemntation that I've found yet though.  IP on the
other hand would much rather be quiet, and is sometimes easier to get to
behave.  But IP gives you all of this DNS and DHCP garbage, which you don't
have to deal with on an IPX network.  
</novell BIAS>

> You can't exactly add just more switches and increase segements, cause
> you'd still have these broadcasts running through to every segment
> available everywhere, right?

You can't just add switches, because they only separate collision domains,
but you can add routers to separate collision domains.  Everything I've
heard about BGP4 for IP sounds really good, but I don't completely
understand how it works yet.  Using it should keep maintence to a minimum,
and allow for load balancing across multiple links.

> Not that we are talking much bandwidth or huge packets, but a sum of
> packets fairly spread, just enough to make a collision sound like a
> normal everyday happening.
> I just hate it when I plug in a freshly installed server, not even
> booted, into a switch and see the blinkenlichts starts to 
> glow - without
> even having any traffic.

Our network is fairly quiet, with about 700+ nodes.  The majority of our
traffic is headed for our internet connection, so it doesn't even get to the
switches for our servers, which could be why I don't see any activity.  I'd
check out 3Com, Cisco, and a couple of other people for "Layer 3 Switches",
to see if you can't increase the number of broadcast domains, since it
sounds like it's a fairly big problem.  Wow, something on the Sun list that
I'm almost qualified to answer...  :-)

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