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At 11:21 AM 2/19/2001 -0800, Priscilla Oppenheimer wrote:<br>
<blockquote type=cite class=cite cite>At 08:14 AM 2/19/01, AndyD
wrote:<br>
<br>
<br>
>It looks like you need to go to<br>
>layer 3 switching to do any load balancing other than this.
And<br>
>etherchannel is another option for aggregating bandwidth. But
someone said<br>
>with etherchannel using 4 full duplex 100 mbp ports will not give 800
mbps<br>
>of throughput? I always thought that in theory that was the
case??<br>
<br>
It's "statistical" load balancing, according to Cisco. The
operation that <br>
determines which link in a Fast EtherChannel to use is quite bizarre, and
<br>
does not provide precise load balancing. It provides load sharing. Think
of <br>
it like a complex highway system. Adding new highways distributes the
load, <br>
but it doesn't usually balance the load very
precisely.</blockquote><font face="Arial Narrow, Helvetica"><br>
Are you saying it should provide precise load balancing? That would
seem to add a scary amount<br>
of knowledge that the FEC interface would need to know -- RMON traffic
statistics or the like to <br>
figure out how to distribute flows. Intuitively, the cost of adding
that intelligence would exceed,<br>
by far, the cost of throwing more bandwidth at the problem.<br>
<br>
Recovery after failure would take longer as well, IMHO.<br>
<br>
<br>
</font><blockquote type=cite class=cite cite>The division of traffic
across a Fast EtherChannel is based on <br>
source/destination pairs, which is usually not very balanced. There are
<br>
usually some big talkers and receivers. The Ethernet Bundling Controller
<br>
(EBC) performs an X-OR operation on the last two bits of the source MAC
<br>
address and the destination MAC address. This operation yields one of
four <br>
results: (0 0), (0 1), (1 0), or (1 1). Each of these values points to a
<br>
link in the Fast EtherChannel bundle.<br>
<br>
Priscilla<br>
<br>
> Since<br>
>the data is transmitted on different wire pairs, if the sender and
receiver<br>
>transmit at the same time, why isn't 800 mbps possible????<br>
></blockquote></html>
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