Mpps, Need some help

Answered Question
Mar 5th, 2010

I never understood the Mpps Parameter, does this paarmeter referers to the switches ability to process this many packets per second, secondly it changes with packet size but why, thirdly do cisco switches 2960 3750 4948 based on centralized forwarding or distributed forwarding.




2960-48PST-S

13.3 Mpps

Correct Answer by Ganesh Hariharan about 6 years 11 months ago

I never understood the Mpps Parameter, does this paarmeter referers to the switches ability to process this many packets per second, secondly it changes with packet size but why, thirdly do cisco switches 2960 3750 4948 based on centralized forwarding or distributed forwarding.




2960-48PST-S

#

13.3 Mpps



Hi,


MPPS stands for million packets per second and Cisco prefers to refer throughput in MPPS.For a layer-3 switch an Mpps value is shared one. For some of the higher-end cisco routers the routing is "distributed" between multipe line-cards, in which case the PPS numbers are based on the number of line cards, bit for non-distributed architectures (Catalyst switches) the numbers are based on the routing engine, so it is the maximum number of Packets Per Second that the box can route.


and as giuslar said 2960 switches are centralized cef based forwarding.


Hope to Help !!


Ganesh.H

Correct Answer by Giuseppe Larosa about 6 years 11 months ago

Hello Khalid,


the figure Mpps expresses the maximum number of frames per second that can be processed by the device.

It is not dependent on frame size but clearly small frames require higher packet rates.


To give you an idea of what this number says:

smallest frames in ethernet are 64 bytes in size, taking in account the preamble (8 bytes) and the minimum interframe gap (the last two counts roughly for 20.2 bytes) to fill a GE port in one direction you need

1484560 frame per second.


10^9 / [(64+20,2)*8]


where 8 is bits/byte


so a number of 13.3  Mpps is equivalent to 4,47 GE ports filled with smallest frames bidirectional.


on the other hand frames of max size 1518 bytes require 81264 fps to fill a GE port in one direction.


So this number expresses the forwarding capability of the device.

A non blocking device with 48 GE ports would require 2 * 1484560 * 48 as Mpps or higher.


A device like C2960 can be classified as centralized CEF forwarding.


Hope to help

Giuseppe

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Correct Answer
Giuseppe Larosa Sat, 03/06/2010 - 00:39

Hello Khalid,


the figure Mpps expresses the maximum number of frames per second that can be processed by the device.

It is not dependent on frame size but clearly small frames require higher packet rates.


To give you an idea of what this number says:

smallest frames in ethernet are 64 bytes in size, taking in account the preamble (8 bytes) and the minimum interframe gap (the last two counts roughly for 20.2 bytes) to fill a GE port in one direction you need

1484560 frame per second.


10^9 / [(64+20,2)*8]


where 8 is bits/byte


so a number of 13.3  Mpps is equivalent to 4,47 GE ports filled with smallest frames bidirectional.


on the other hand frames of max size 1518 bytes require 81264 fps to fill a GE port in one direction.


So this number expresses the forwarding capability of the device.

A non blocking device with 48 GE ports would require 2 * 1484560 * 48 as Mpps or higher.


A device like C2960 can be classified as centralized CEF forwarding.


Hope to help

Giuseppe

asharkhalid Mon, 03/08/2010 - 01:14

Thanks giuslar and Ganesh,


Refereing to table below, 71 mpps mean 23.85 GE Ports full duplex packet per second processing can be achieved right, then how can 4928 can switch @ 96 Gbps.



Cisco Catalyst 4900 Series Switch Model Comparison for Fiber Aggregation

Feature and Description

Cisco Catalyst 4928 10 Gigabit Ethernet Switch

Switch Capacity

96 Gbps

Throughput

71 mpps

Ganesh Hariharan Mon, 03/08/2010 - 01:56

Re: Mpps, Need some help                                                                                                                                  


                                                                  

Thanks giuslar and Ganesh,


Refereing to table below, 71 mpps mean 23.85 GE Ports full duplex packet per second processing can be achieved right, then how can 4928 can switch @ 96 Gbps.



Cisco Catalyst 4900 Series Switch Model Comparison for Fiber Aggregation

#

#

Feature and Description

#

Cisco Catalyst 4928 10 Gigabit Ethernet Switch

#

Switch Capacity

#

96 Gbps

#

Throughput

#

71 mpps


Hi,


Switching capacity is some times given as  the amount of frames a switch can deal with over a given time frame and throughput on the other hand means  how much actually data can cross the switch in a given time frame.


Hope to Help !!


Ganesh.H

Correct Answer
Ganesh Hariharan Sat, 03/06/2010 - 05:20

I never understood the Mpps Parameter, does this paarmeter referers to the switches ability to process this many packets per second, secondly it changes with packet size but why, thirdly do cisco switches 2960 3750 4948 based on centralized forwarding or distributed forwarding.




2960-48PST-S

#

13.3 Mpps



Hi,


MPPS stands for million packets per second and Cisco prefers to refer throughput in MPPS.For a layer-3 switch an Mpps value is shared one. For some of the higher-end cisco routers the routing is "distributed" between multipe line-cards, in which case the PPS numbers are based on the number of line cards, bit for non-distributed architectures (Catalyst switches) the numbers are based on the routing engine, so it is the maximum number of Packets Per Second that the box can route.


and as giuslar said 2960 switches are centralized cef based forwarding.


Hope to Help !!


Ganesh.H

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