At 04:55 PM 6/7/01, Graham, Darel R. wrote:
>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.
A switch makes a forwarding decision. A router that has cached the
MAC-layer encapsulation for outgoing frames for a destination (and possibly
source and port number) also makes a decision, and it can make that
decision essentially as fast as a switch can make its decision.
A router runs routing protocols. In an optimized architecture, running
routing protocols does not affect the performance of forwarding packets. A
switch runs Spanning Tree Algorithm and possibly VTP and other management
(control?) protocols. In an optimized architecture, running these protocols
does not affect the performance of forwarding packets.
> Switches have basically one job at either level.
>
> On the other hand you have warts :)
Thanks a lot!? ;-)
> 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.
You think this is slow?
Cisco 12000 = 375 million PPS
http://www.cisco.com/univercd/cc/td/doc/pcat/12000.htm
Cisco 7600 - 30 million PPS
http://www.cisco.com/univercd/cc/td/doc/pcat/7600.htm
My conclusion: They're the same damn thing! Does anyone remember that Janis
Joplin song where she sings about travelling by train with her group when
they discovered that night and day are the same f***ing thing! ;-)
Priscilla
> 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
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=7641&t=7406
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