ASR9K LC (A9K-24X10GE-1G-TR) oversubscription mode ?

[ferdi]

Hello,

The A9K-24X10GE-1G-TR LC datasheet has an explanation as below. Can someone explain this a bit?

- The throughput is 200G (I think there are 2 x 100G conenction at backplane), and how can it operate up to 240G ?

https://www.cisco.com/c/en/us/products/collateral/routers/asr-9000-series-aggregation-services-routers/datasheet-c78-738704.html

The 24-port and the 48-port line cards are designed for throughput of 200G and 400G, respectively, but can operate in oversubscription mode up to 240G for the 24-port card and 480G for the 48-port card.

Thanks

[Giuseppe Larosa]

Hello ferdi,

working in oversubscription mode means that you can activate 24 tengiga ports on the linecard but they will share the available to fabric and from fabric bandwidth of 200 Gbps each.

In other words the linecard supports up to 20 tengiga ports full rate.

If using all 24 ports they cannot work at full rate at the same time. This is called oversubscription.

The same for the other linecard with 48 tengiga ports and 400 Gbps to fabric and from fabric BW.

In this case up to 40 ports can be full rate at the same time.

Hope to help

Giuseppe

[ferdi]

Thanks for the reply.

How do we calculate the 240G ?

If it was a typhoon card I could say as below, but it is tomahawk. As I know tomahawk provides 115G per fabric and this LC is 5 fabric card.

• On the LC itself, between the crossbar and each FIA, there are 4 x 8 x 7.5 links which provide 240G of raw bandwidth per FIA. Between NP and FIA, the single 8 x 7.5 link gives 60 G of raw bandwidth.
• The bandwidth referenced is the raw bandwidth. Actual bandwidth is slightly less after overhead is considered, it is 200G for this LC.

The LC NPU-FIA connection is as on the attachment.