switch vs. router question
Response - it depends on what you want it to do.
If you want something that makes no routing decisions - then a
switch is the answer.
Switches have basically one job at either level.
On the other hand you have warts :)
Really - routers will have a different load to handle, even in a
multi layered approach.
So, a router is likely to be slower in accomplishing mega packets
per second.
Make the decision based on what it will be used for in the network
design.
Remember use the right tool for the job and no one gets hurt.
Darel R Graham
Beer is proof that God loves us and wants us to be happy.
-Benjamin Franklin
-----Original Message-----
From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]]
Sent: Thursday, June 07, 2001 3:52 PM
To: [EMAIL PROTECTED]
Subject: Re: Layer3 switch vs Router [7:7406]
I just wanted to get my $0.02 in, but the message had gotten so long I
think the filters dropped my response. I apologize if this is a duplicate.
Priscilla
At 12:39 AM 6/7/01, Michael L. Williams wrote:
>Chuck...... I talked to a good friend of mine that knows more of this than
>I do...... and even HE wasn't clear on the line of switch -vs- router.....
>so my following comments are strickly my thinking out loud...... mostly to
>get feedback .....
>
>I don't think there is a difference in a layer 3 switch that does 100,000
>packets/sec -vs- a router that does 100,000 packets/sec. However,
>respectfully submit that I don't know of any routers that can keep up with
>Layer 3 switches because in multilayer switching the route processor only
>has to route the first packet in a flow.
Yes, but..... Isn't that true for a router with fast switching, silicon
switching, optimum switching, distributed switching, etc? And with NetFlow
switching, a router can take into account access control lists and QoS
features that need to be applied to a flow, much in the same way that these
new MLS switches can do this with their flow masks. (Thanks for your
earlier message that explained flow masks so well.)
I agree that MLS has great potential. It sounds complicated to configure
and hard to troubleshoot, though. I think I would keep a hub and a protocol
analyzer handy when first implementing it, so I could check traffic between
the MLS-RP and MLS-SE when things went wrong.
Regarding packets-per-second, we need to remember that this is a marketing
game. The enormous numbers come from the absolute maximum possible number
of packets on a Gigabit Ethernet, taking into account the inter-frame gap
and preamble. The test engineers pump frames of the smallest possible size
into the switch to make the numbers really look big. (I wonder if they take
into account the carrier extension with Gigabit Ethernet? That would make
the numbers less.) The PPS is based on this max number of packets coming in
one port and going out another Gigabit Ethernet port. They can increase the
numbers even more by using multiple ingress and egress ports and no
contention for an egress port.
The numbers for both switches and some routers are so astronomically high
these days that they stretch credibility. Do real-world traffic generators
really send that much traffic?
Regarding CPUs, the general-purpose CPU on the Cisco routers may not be
very fast, but the high-end routers also have Versatile Interface
Processors that help with high-speed switching.
One last point is that routers have features that switches don't have
today. We configure access lists on routers. (Although an MLS-SE can make
use of these access control lists, we still configure them on the router).
Routers run running protocols. Routers act as firewalls, policy servers,
handle RSVP and other QoS requests, connect telephones, act as DHCP
servers, connect modems both analog and cable, etc.
Just a few thoughts before this interesting discussion undergoes a
well-deserved retirement.
Priscilla
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=7632&t=7406
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