How to determine the number of links for a router based on its throughput in KPPS

Unanswered Question
Dec 4th, 2009

Dear Team,

                    Please let me know if we need to determine the type of router for a location, what are the parameters to be considered?If we are given only throughput in KPPS (Kilo Packets Per Second) for a packet size of 64 bytes how can you determine the size or Bandwidth of the link that may be connected to this router without compromising on the performance level for all practicle purposes.

For example for 3845 router the performance is 500 KPPS now upto what bandwidth the router will perform without a problem in a praticle scenerio where the packet size may not be limited only to 64 bytes packet.

Regards

Abhishek

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Giuseppe Larosa Fri, 12/04/2009 - 05:31

Hello Abhishek,

two possible approaches here:

worst case analysys: considering packets of smallest size

a sort of average analysis: considering packets of average size, let's say 500 bytes.

given a packet forwarding capabilities in pps you can find the equivalent bandwidth:

by dividing by 2 to take in account bidirectionality and then you multiply using the packet size

(pps/2) * packet_size* (1/8)

bits/byte

be aware that the only safe approach is the worst case analysys because performance data are given without any feature applied (ACLs, QoS, NAT) that reduce performance in software based routers.

Hope to help

Giuseppe

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