>From the Cisco website:
http://www.cisco.com/warp/public/cc/so/cuso/epso/entdes/highd_wp.htm
watch that wrap :->
Layer 3 switching is hardware-based routing. In particular, the packet
forwarding is handled by specialized hardware, usually ASICs. Depending on
the protocols, interfaces, and features supported, Layer 3 switches can be
used in place of routers in a campus design. Layer 3 switches that support
standards-based packet header rewrite and time-to-live (TTL) decrement are
called packet-by-packet Layer 3 switches.
High-performance packet-by-packet Layer 3 switching is achieved in different
ways. The Cisco 12000 Gigabit Switch Router (GSR) achieves wire-speed Layer
3 switching with a crossbar switch matrix. The Catalyst(r) family of
multilayer switches performs Layer 3 switching with ASICs developed for the
Supervisor Engine. Regardless of the underlying technology, Cisco's
packet-by-packet Layer 3 switching implementations are standards-compliant
and operate as a fast router to external devices
End quote.
But also look at this:
http://www.cisco.com/warp/public/784/packet/july98/12.html
The primary difference between the packet-switching operation of a router
and a Layer 3 switch is the physical implementation. In general-purpose
routers, packet switching is typically performed by microprocessor-based
engines. A Layer 3 switch performs packet switching with
application-specific integrated circuit (ASIC) hardware, which enables
greater raw throughput.
Although higher-speed packet switching would seem to offer obvious benefits,
a common but flawed assumption is that it will automatically improve the
speed of applications. For example, if application demand on the network is
10,000 pps, and current Layer 3 devices process packets at 200,000 pps,
replacing them with devices that perform even at 10 million pps will not
speed up the applications.
Raw performance, therefore, is not the most important criterion for
selecting a Layer 3 switch. Route processing and intelligent network
services -- two vital software functions -- have a more significant impact
on the performance of specific applications and the network as a whole.
End of quote
Note the caveat, from Cisco's own mouth, as it were: layer 3 switching
cannot be assumed to automatically improve network performance.
This continues to be a wonderful thread, one forcing me, at least, to push
the envelope in my studying.
Chuck
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
Kevin Wigle
Sent: Tuesday, August 15, 2000 4:09 PM
To: Jeffrey Humphreys; Howard C. Berkowitz; [EMAIL PROTECTED]
Subject: Re: Switches !!!
hmmm......... in the aforementioned new Cisco CDs I just got there is a "8
Minute Layer III Switching QuickStudy".
The interesting thing it points out between differences in using a router to
route or a switch to "route" is that routers have RISC processors and
switches have ASICs.
It goes on to say that the RISC is more powerful and meant for doing other
things like encryption, handling WAN traffic, etc - whereas ASIC does
forwarding only. (but is much faster doing it)
So it comes down to your environment and the invariable "what problem are
you trying to solve" kind of thing.
Kevin Wigle
----- Original Message -----
From: "Jeffrey Humphreys" <[EMAIL PROTECTED]>
To: "Howard C. Berkowitz" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Monday, 14 August, 2000 23:42
Subject: Re: Switches !!!
> Sorry, I was thinking RSM and typed RSP but I don't see much of a
difference
> in there functionality. I agree with Howard's description of the RSP and
> RSM. We pretty much just took a 7500 RSP and modified it to interface to
> the Catalyst bus.
>
> Jeff Humphreys
>
> ----- Original Message -----
> From: Howard C. Berkowitz <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Monday, August 14, 2000 7:32 PM
> Subject: RE: Switches !!!
>
>
> > >I have to say that I'm a little confused my self!
> > >RSP "Route Switch Processor" is used by the 7500's
> > >RSM "Route Switch Module" can be used by Cat5500 for example.
> > >We have currently 7 5500's with RSM's, and I tell you it is doing all
of
> the
> > >routing for us to include VLANs. Lot's of then.
> > >What I am trying to say here is that I can Route between VLAN's just
fine
> > >with an RSM. I think that someone missed typed RSP with RSM.
> > >Paulo
> >
> >
> > Nahhh...
> >
> > The guts of a RSM and RSP are the same. The RSM connects to a Cat5000
> > bus and can have its own WAN interface. The RSP connects to a CBus
> > in a 7x00. There are also faster RSPs available than RSMs.
> >
> > ___________________________________
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