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Catalyst 2960-XR x Catalyst 3650 Forwarding Rate

apereira3
Level 1
Level 1

Hello Dears,

I would like know why does it show the following performance parameters at 64-bytes L3 packets to the two Catalyst switch families:

Cisco Catalyst 2960XR-24TD-I                                           Cisco Catalyst 3650-24TD-S                                    

Forwarding Rate: 95.2 Mpps                                                Forwarding Rate: 68,45 Mpps

Both models have 24 10/100/1000 Ethernet ports and 2 x 10 GbE uplink ports.

The Catalyst 2960XR family has the IP Lite feature set that implements static routing and some features for dynamic routing (routed access). The Catalyst 3650 with the IP Base feature set also performs static routing, RIPv1/RIPv2 routing and others advanced IP unicast routing protocols for routed access. 

What is the reason for these difference between the forwarding performance at 64-bytes L3 packets?

Thank you!

Allyson

6 Replies 6

Joseph W. Doherty
Hall of Fame
Hall of Fame

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.

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In no event shall Author be liable for any damages wha2tsoever (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

What is the reason for these difference between the forwarding performance at 64-bytes L3 packets?

They are very likely different architectures.

BTW, for 24g + 10g + 10g, wire speed, for 64 byte packets needs 44g * 1.488 Mpps = 65.472 Mpps.  So, both switches have PPS rating higher than they need.  Why?  Hardware might have excess capacity that, in theory, wouldn't ever be used (but makes for nice numbers in the sales literature).

Hi Joseph,

Thank you for your help!

But can you explain me the values of this operation (44g * 1.488 Mpps)?

Thanks!

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 wha2tsoever (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

Sure, wire speed Ethernet "needs" 1.488 Mpps per gig, so if we have 44 gig total (sum of all the interface bandwidths), we need 44g * 1.488 Mpps = 65.472 Mpps.  If the device doesn't provide at least that, it wouldn't support wire speed for all the interfaces concurrently.

Thank you for providing this information!

Is the information about forwarding performance related to wire speed?

How can you reach "1.488 Mpps"? Anything associate with Ethernet packet lenght (1.518 bytes)?

Thanks!

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 wha2tsoever (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

Is the information about forwarding performance related to wire speed?

Yes it is.

How can you reach "1.488 Mpps"?

By transmitting 64 byte packets at 1 Gbps.

Anything associate with Ethernet packet lenght (1.518 bytes)?

Yes, see table below for PPS rates for some different Ethernet packet sizes.

Packet Size (Bytes)  64  128  256  512  1024  1518 
Theoretical Maximum Kpps

1488

845

453

235

120

81

Ok. Thank you very much!

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