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From David kerber <>
Subject Re: Performance 5.5 vs 6 vs 7
Date Mon, 14 Mar 2011 12:08:20 GMT
On 3/14/2011 3:12 AM, Peter Crowther wrote:
> On 13 March 2011 21:01, Tony Anecito<>  wrote:
>> As someone mentioned the network can imit you. If your bandwidth
>> utilization is
>> at 60% or over you are in trouble since collisions start to become a
>> serious
>> issue.
>> Collisions may or may not be an issue, depending on the exact mode of
> operation of the congested network link.
> Collisions are a feature of the original Ethernet.  They're still an issue
> on many Ethernets, but there are provisos even here.  If your switch does
> store-and-forward, or you simply have a switched network and all the traffic
> is between two stations, then collisions are relatively unlikely and the
> Ethernet usage can go considerably higher than 60% before collisions and
> retries start to become significant.  Sure, if you're on wireless or using
> an old 10baseT or Cheapernet hub, 60% is about the knee in the curve.  But
> I'd be a little surprised if Dave were using such ancient technology for a
> critical piece of infrastructure such as this server :-).

We're not, though you would probably be surprised how long it lasted 
before we modernized...  ;-D

> Point-to-point links, such as most broadband connections, do not suffer from
> collisions as the routers at each end store and forward traffic across the
> link.  That said, by the time you get to 80% usage then each packet is
> typically going to have to queue behind several others.  Even if this only
> adds a few milliseconds of latency each time, it builds up when you multiply
> it by the TCP 3-way handshake, 4-way FIN/ACK sequence, plus any data you're
> transferring.

Makes sense to me.

> Dave, could you give us any more information about your network?  What is
> the piece that's at 80% utilisation when you see the trouble?  Is it a
> point-to-point connection, or an Ethernet LAN, or what?  If it's Ethernet,
> what hardware are you using for connection?

It's our internet connection to the outside world, which is a T-1, with 
a Cisco ASA for the firewall.  The connections we're processing are from 
a bunch of separate customer sites, but which all connect to us through 
the customer's gateway.


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