-and I thought something that moved data packets at layer 3 was supposed to
be called a router?
>>>Brian
>From: "Howard C. Berkowitz" <[EMAIL PROTECTED]>
>Reply-To: "Howard C. Berkowitz" <[EMAIL PROTECTED]>
>To: [EMAIL PROTECTED]
>Subject: RE: But isn't that the routers job???
>Date: Tue, 23 Jan 2001 12:44:35 -0500
>
>Let me try to inject some perspective. This thread seems to have an
>underlying premise about certain platform design goals being universal
>across all router applications.
>
>Fortunately or unfortunately, the requirements for a SOHO router, a branch
>office router, an enterprise core router, an ISP POP router, and an ISP
>core router have substantially different motivations.
>
>Take the small routers at SOHO or branch. These devices are price
>sensitive. If both lookups and forwarding can be done in the same "cheap"
>processor, how more affordable is the router if it doesn't need a separate
>RP?
>
>There tends to be a lot of assumptions that routers present significant
>internal delay (and a salesish assumption that "layer 3 switches" somehow
>don't). In most circumstances, you'll find router-associated delays, below
>the major ISP level, to be more a matter of serializatin and queueing delay
>than internal transfer.
>
> >
> >
> >Hey Group,
> > Me again. I'm reading for my CIT and am at the section where it
> >goes
> >into detail of the various switching methods in the router (i.e.,
> >silicon,
> >CEF, autonomous, etc.) I understand how all this works and understand
> >how the
> >SP takes a lot of the stress away from the RP and this is good because
> >your
> >avoiding bogging the RP/CPU down. I have a problem with these statements
> >though and want some clarification...
>
>Cost may be more important than bogging.
>
> >
> >Taken form the book (Lammle's CIT p. 173):
> >
> > "This is just another reason why switching is such a good practice.
> >Why
> >burden the RP with every packet if it's not necessary? By using
> >switching
> >methods, the RP is free to use valuable CPU time on more important
> >things
> >than doing route lookups for every packet that comes in the router."
>
>First, route lookup isn't terribly CPU expensive, especially if it uses an
>algorithm such as the CEF mtrie. You're talking on the order of 4-5 memory
>accesses in CEF. More in other methods, but not a major source.
>
>Rewriting packet headers (e.g., for fragmentation) is much more CPU
>expensive. Filtering can be.
> >
> >
> >Basically, could somebody give me a list of some other things the RP/CPU
> >has
> >to do other than route lookups...(I know there are access-lists and
> >other CPU
> >things here, I just would like a solid list to remember). Thanks team,
>
>Memory management
>SNMP
>Console & telnet
>Interrupt scanning
>Dynamic routing
>Filtering
>Traffic shaping
>Debug
>Packet rewriting
>Accounting
>Encryption, tunneling, compression
>
>...
>
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