09-14-2012 09:12 AM - edited 03-07-2019 08:53 AM
Hello,
It is just of the curiosity but here is a question which have no answer for me.
Why Cisco implements so much switching capacity in their switches?
For example take the WS-C2960-24TT-L :
24 ports 10/100 Base-TX
2 combo ports 100/1000 Base-T or Base-X
Backplane Capacity:16 Gbps
Forwarding Performance : 6.5 Mpps
Obviously,16 Gbps of permutation performance is too much for the 8,8 Gbits (24*200+2*2000) needed by ports so why they put so many bandwidth?
Thanks for your help and sorry for my bad english skills.
Romain
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09-14-2012 11:04 AM
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
As also described by Giuseppe, many of the smaller switches have a one-size fabric bandwidth and forwarding performance; just number of ports wired to it varies per model. Cisco normally documents the capacity of the fabric regardless of the number of ports. Often there might be excess fabric bandwidth that cannot be used on a particular model (or not enough for other models). Cisco also normally documents the PPS, though, at the highest capacity the device can use given its ports, if aggregate performance requirement is less than hardware switching capacity, or total forwarding capacity if the total aggregation of ports can exceed physical switching capacity.
PS:
Requirements for worst-case wire-speed/line-rate Ethernet are: fabric bandwidth = 2 times all port bandwidths (stated non-duplex) and 1.488 Mpps per 1 Gbps of all port bandwidths (stated non-duplex).
09-14-2012 10:17 AM
Hello Romain,
the backplane HW may be the same of the 48 ports model.
Having a good switching capacity is not a bad thing at all.
Hope to help
Giuseppe
09-14-2012 10:20 AM
Hi,
What you calculated is for a 24 port switch. If you calculate the same for a 48 port switch, you come closer to 16Gig.
Usually, the Backplane capacity is built for max.
HTH
09-14-2012 11:04 AM
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
As also described by Giuseppe, many of the smaller switches have a one-size fabric bandwidth and forwarding performance; just number of ports wired to it varies per model. Cisco normally documents the capacity of the fabric regardless of the number of ports. Often there might be excess fabric bandwidth that cannot be used on a particular model (or not enough for other models). Cisco also normally documents the PPS, though, at the highest capacity the device can use given its ports, if aggregate performance requirement is less than hardware switching capacity, or total forwarding capacity if the total aggregation of ports can exceed physical switching capacity.
PS:
Requirements for worst-case wire-speed/line-rate Ethernet are: fabric bandwidth = 2 times all port bandwidths (stated non-duplex) and 1.488 Mpps per 1 Gbps of all port bandwidths (stated non-duplex).
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