Date: Sat, 27 Mar 1999 08:13:38 -0700 From: Wes Peters <wes@softweyr.com> To: Mike Jenkins <mjenkins@carp.gbr.epa.gov> Cc: freebsd-net@freebsd.org, mm@i.cz Subject: Re: switch vs bridge (fwd) Message-ID: <36FCF5A2.8F3F11E9@softweyr.com> References: <199903270149.TAA07234@carp.gbr.epa.gov>
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Mike Jenkins wrote:
>
> Wes Peters wrote:
> > The you either don't understand the job, or don't understand the (very
> > limited) capabilities of these so-called layer 4 switches. It's not that
> > it's a bad idea, just that there are a couple of vendors out there giving
> > the idea a bad name with their implementations.
>
> I think the concept of switching based on udp/tcp port is useful.
> One thing I'm not clear on is at what layer is the switch gathering
> the packets? Is it at the data link (Ethernet) layer or the network
> layer (IP)? I was assuming the data link layer to allow transparency.
> If it is the network layer then the switch is your router as Wes said.
> Do layer 3 switches have the ability to redirect packets based on
> udp/tcp port numbers?
That is, by definition, layer 4. Layer 3 is the IP address layer, and
no "port" information occurs there. As I said above, it's not that
layer 4 switching is a bad idea, it's just that the current implementation
from some of these vendors is a bit weak, and none are based on standard
protocols.
And it *is* a bad idea to have every switch on your network peeking all
the way into the layer 4 information of EVERY packet flowing through,
that means you've bought a couple thousand times more packet processing
power than you really need. The best way to do it would be to stick
a layer-4 balancing engine inside a switch chassis, managing ports
via the switch backplane. AFAIK nobody has done this yet, but it's such
a darned good idea, I know somebody who might. ;^)
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters Softweyr LLC
http://www.softweyr.com/~softweyr wes@softweyr.com
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