[112339] in North American Network Operators' Group
Re: switch speed question
daemon@ATHENA.MIT.EDU (Eric Gearhart)
Tue Feb 24 10:54:15 2009
In-Reply-To: <003901c99662$eacdff60$c069fe20$@com>
Date: Tue, 24 Feb 2009 08:51:12 -0700
From: Eric Gearhart <eric@nixwizard.net>
To: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
On Tue, Feb 24, 2009 at 2:33 AM, Bruce Grobler <bruce@yoafrica.com> wrote:
> Hi,
>
> It depends on how heavily loaded your switch is expected to be, for instance
> two machines using the switch will be able to get a full 1Gbps, however
> depending on the backplane (switching fabric), it limits how many ports will
> receive full 1Gbps when the switch is congested, e.g. a 2 gig backplane
> against a 24 gig.
>
> Regards,
>
> Bruce
Note that the traffic to a switch is bi-directional (full duplex) - so
a 24 port gigabit switch can max out its 32 Gig backplane, if all 24
ports have a gig coming in and going out (24 X 2 is 48, more than the
32 gig backplane).
This isn't immediately apparent - the other day someone at my work
asked the exact question "Why's the 32 gig backplane > the 24 ports on
the switch?"
--
Eric
http://nixwizard.net
