thank you priscilla for your kindness
thanks a million
regards,
suaveguru
--- Priscilla Oppenheimer <[EMAIL PROTECTED]> wrote:
> You should know about the different switching types
> a router can handle for
> the CIT test and for the real world and possibly
> other exams too. Below is
> a copy and paste from Chapter 12 of Top-Down Network
> Design. The chapter
> covers optimizing your network design.
>
> One of the major jobs of a router is to switch
> packets from incoming
> interfaces to outgoing interfaces. Switching
> involves receiving a packet,
> determining how to forward the packet based on the
> routing topology and QoS
> and policy requirements, and switching the packet to
> the right outgoing
> interface or interfaces. The speed at which a router
> can perform this task
> is a major factor in determining network performance
> in a routed network.
> Cisco supports many switching methods, with varying
> speeds and behaviors.
>
> In general, you should use the fastest switching
> method available for an
> interface type and protocol, (though there are some
> exceptions to this
> guideline.) Using a speedy switching mode is
> especially important on
> backbone and core enterprise routers. Depending on
> the version of IOS
> software you are running, the fastest mode might
> need to be configured. (It
> is not always the default.)
>
> Below are some of the details on the switching
> types.
>
> Process switching is the slowest of the switching
> methods. With process
> switching, when a packet arrives at an interface,
> the system processor is
> interrupted for the time it takes to copy the packet
> from the interface
> buffer to system memory. The processor looks up the
> Layer-3 destination
> address for the packet in the routing table to
> determine the exit
> interface. The packet is rewritten with the correct
> header for that
> interface and copied to the interface. At this time,
> an entry is also
> placed in the fast-switching cache so that
> subsequent packets for the
> destination address can use the same header. The
> first packet to a
> destination is always process switched.
>
> Fast switching allows higher throughput by switching
> a packet using an
> entry in the fast-switching cache that was created
> when a previous packet
> to the same destination was processed. With fast
> switching, a packet is
> handled immediately, without scheduling an interrupt
> of the system processor.
>
> Autonomous switching is available on Cisco
> 7000-series routers and uses an
> autonomous-switching cache located on interface
> processors. Autonomous
> switching provides faster packet switching by
> allowing the ciscoBus
> controller to switch packets independently, without
> having to interrupt the
> system processor.
>
> Silicon switching is similar to autonomous
> switching, but speeds up
> autonomous switching through the use of a
> silicon-switching cache located
> on the Silicon Switch Processor (SSP) on some Cisco
> 7000-series routers.
>
> Optimum switching is similar to fast switching, but
> is faster, due to an
> enhanced caching algorithm, and the optimized
> structure of the
> optimum-switching cache. Optimum switching is only
> available on routers
> equipped with a Route/Switch Processor (RSP).
>
> Distributed switching is supported on routers that
> include Versatile
> Interface Processor (VIP) cards or other interface
> cards that can receive
> route information from the master RSP to make their
> own autonomous,
> multilayer switching decisions. Distributed
> switching supports very fast
> throughput because the switching process occurs on
> the interface card.
>
> NetFlow switching is a relatively new switching mode
> that is optimized for
> environments where services must be applied to
> packets to implement
> security, QoS features, and traffic accounting. An
> example of such an
> environment is the boundary between an enterprise
> network and the Internet.
> NetFlow switching identifies traffic flows between
> hosts, and then quickly
> switches packets in these flows at the same time
> that it applies services.
> NetFlow switching also lets a network manager
> collect data on network usage
> to enable capacity planning and bill users based on
> network and application
> resource utilization. The data can be collected
> without slowing down the
> switching process.
> To maximize network scalability, a good design
> practice is to use NetFlow
> switching on the periphery of a network to enable
> features such as traffic
> accounting, QoS functionality, and security, and to
> use an even faster
> switching mode in the core of the network. At the
> core of the network, the
> switching mode should forward packets based on
> easily-accessible
> information in the packet, and generally should not
> spend time applying
> services.
>
> Hope this helps.
>
> Priscilla
>
> At 06:44 PM 3/4/01, suaveguru wrote:
> >hi all,
> >
> >while studying for the support exam I came across
> >Silicon switching, netflow switching , silicon
> >switching , Automonous switching , process
> switching
> >etc.
> >
> >I am confused by so many switching types and what
> >routers support them
> >
> >anyone can give me a quick brief overview and what
> it
> >will be tested on in the exam
> >
> >thanks
> >
> >suaveguru
> >
> >
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>
> ________________________
>
> Priscilla Oppenheimer
> http://www.priscilla.com
>
> _________________________________
> FAQ, list archives, and subscription info:
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[EMAIL PROTECTED]
__________________________________________________
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_________________________________
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