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Max throughput - ubr10k with PRE4

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Max throughput - ubr10k with PRE4


Is anyone running a busy ubr10k / PRE4 / 3G60 (and maybe some SPA24s) ?

What is the max traffic you have seen with this combination ?

With a 10G WAN card in each SIP600, can the PRE4 support full 20Gbps of internet ?


Sorry, I can't help you there. We got rid of all of our 10k's before traffic hit that point, but if I remember correctly, the boxes didn't seem strain at all hitting 7+Gbps or so, cpu didn't pick up too much, so I would think 20G would be doable. Now with our cbr's and newer, faster speed packages, we're bumping 30Gbps on these bad boys.

Yes I have cBR8 as well,

Yes I have cBR8 as well, doing 50Gbps+ no drama there :-)

But one site has this busy uBR10k, and I saw a big multi-hour flatline at 12.4Gbps during one of those recent Akamai traffic surges.

3G60 linecards not maxing out, plenty of capacity there.

So PRE4 seems the likely bottleneck? Information on this topic is pretty scarce though....

This doc gives a few hints about PRE4 limits:
•10 Mpps forwarding performance through the PXF complex
•5.6 Gbps backplane bandwidth for each full-height backplane slot
•11.2 Gbps backplane bandwidth for each SPA interface processor (SIP)
•12.8 Gbps backplane interconnect bandwidth for each set of 4 full-height backplane slots

So based on above, it seems there is no contention feeding the 3G60 linecards

And it looks like there is sufficient backplane bandwidth to have a 10Gbps WAN card in each SIP-600

I did read somewhere that this backplane bandwidth ("ironbus") is full duplex.
So that means each SIP-600 has enough capacity to host 1 x 10G WAN plus 3 x SPA24's
(WAN traffic is mainly SIP -> PRE, whereas the SPA24 traffic is PRE -> SIP)
And the Cisco docs list that as a supported combination.

And I setup some graphing, the initial results appear to validate my theories about 11.2Gbps full-duplex per SIP.

I did find one doc which shows PRE4 in Cisco 10008, and it quotes PRE4 as 10M pps and 17Gbps max.
Interesting diagram there (Figure 3-1) showing how the traffic funnels upwards to this hard limit of 10Mppps / 17Gbps.
Doesn't match my 12.4Gbps flat-line, but perhaps in uBR application the PRE4 has a lower limit?

Unfortunately I don't have any uBR support contracts these days, so I cant open a TAC case to get their opinion.

Before I go and buy some used PRE5's, I was hoping someone else might have already been down this road and know the answer.

We upgraded this CMTS to PRE5

We upgraded this CMTS to PRE5

The previous 12.4Gbps throughput limit is now gone

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