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packet per seconds (pps) vs bits per seconds (bps)

Sherif Ismail
Level 1
Level 1

Hello all

In datasheets of routers/switches, I noticed that performance is defined in two terms

One with a unit of packet per seconds (pps) and other one is bits per sec

I found serveral terms for these 2 units as system capacity, forwarding capacity, throughput, backplane capacity

However I believe one should look at the unit whether it is pps or bps

Now question what is the difference between both terms ?

Why it is important to check both when comparing any 2 devices ?

Do pps calculation is based on a definced packet size ?

Many thanks

3 Replies 3

Joseph W. Doherty
Hall of Fame
Hall of Fame

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Posting

A bps rating often provide the internal bandwidth of the device, often documented for switches.  For example, a switch with 48 gig ports requires a fabric of 96 Gbps to allow all ports to transmit at their gig rate, duplex.  However, many switch fabrics could be less, for example, I recall many of the original 3750 switch's fabric peaks at 32 Gbps.

Switches and routers need to look at frames and packets and decide what to do with them, and then do it.  This is what pps measures, i.e. the maximum number of frames or packets that can be processed.  Since both frames and packets often can vary in size, smaller frames/packets require a higher rate to accomplish the same throughput.  For minimum size Ethernet, 64 bytes, 10 Mbps Ethernet requires 14,880 pps.  However, for 1518 bytes, 10 Mbps only requires 812 pps, much less process demanding.

Thanks for your reply but why this Disclaimer and Liability Disclaimer note !

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Principally because of paragraph 11 of this site's CISCO SUPPORT COMMUNITY ACCEPTABLE USE AGREEMENT.  Unfortunately, you haven't previously also agreed to release me from liabilities, as you have for Cisco.  For example, see paragraphs 10 (c) and 12, same agreement.

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