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Community Member

7600 1 Gig to 10Gig routing performance problems

I have a 7606 with a sup720 and msfc3

with WS-X6148-GE-TX and WS-X6704-10GE

I am trying to send ~1.2 Gbps of traffic from the 6148 to the 6704.

I have a packet generator connected to 10 of the 1G ports each sending ~120Mbps 512byte packets. The first 3 (1/30-1/32)ports don't drop any packets but the next 7 ports (1/33-1/39) drop ~2.25% each.

I checked "show int summary" and it is reporting that packets are being dropped on the input queues.

The config is pretty much default.

I just don't understand why so much packet loss at such a low rate.

I know the 6148 is just a wiring closet blade but it's supposed to have 32Gbps bandwidth to the backplane.

Is there something I need to tune?

2 ACCEPTED SOLUTIONS

Accepted Solutions
Cisco Employee

Re: 7600 1 Gig to 10Gig routing performance problems

Hi,

The 6148 and 6548 cards are subscribed at a rate of 8:1. The architecture of this card is such that there is a shared 1Mb buffer between groups ports (1-8, 9-16, 17-24, 25-32, 33-40, 41-48) since each block of eight ports is 8:1 oversubscribed. If any port in this range is receiving or transmitting traffic at a rate that exceeds its bandwidth or utilizing a large amount of buffers to handle bursts of traffic, the other ports in the same range of 8 may experience packet loss. This explains why you aren't seeing the packet loss on the first three ports, as you are not hitting the oversubscription limit, while you are hitting that limit on the remaining ports.

In short, you can only expect 1Gb/s of aggregate throughput for each block of 8 ports.

HTH,

Bobby

*Please rate helpful posts.

Cisco Employee

Re: 7600 1 Gig to 10Gig routing performance problems

Hi,

That's correct-- 6gig in each direction.

HTH,

Bobby

5 REPLIES
Cisco Employee

Re: 7600 1 Gig to 10Gig routing performance problems

Hi,

The 6148 and 6548 cards are subscribed at a rate of 8:1. The architecture of this card is such that there is a shared 1Mb buffer between groups ports (1-8, 9-16, 17-24, 25-32, 33-40, 41-48) since each block of eight ports is 8:1 oversubscribed. If any port in this range is receiving or transmitting traffic at a rate that exceeds its bandwidth or utilizing a large amount of buffers to handle bursts of traffic, the other ports in the same range of 8 may experience packet loss. This explains why you aren't seeing the packet loss on the first three ports, as you are not hitting the oversubscription limit, while you are hitting that limit on the remaining ports.

In short, you can only expect 1Gb/s of aggregate throughput for each block of 8 ports.

HTH,

Bobby

*Please rate helpful posts.

Community Member

Re: 7600 1 Gig to 10Gig routing performance problems

Thanks for the insite, so I guess the best I could expect if I am transmitting to the 10gig would be ~6Gig correct?

Cisco Employee

Re: 7600 1 Gig to 10Gig routing performance problems

Hi,

That's correct-- 6gig in each direction.

HTH,

Bobby

Community Member

Re: 7600 1 Gig to 10Gig routing performance problems

Are there any non-blocking 10/100/1000 modules?

Is the 6704 10Gig Module oversubscribed?

Where do you find this information?

Thank for all the help!

Cisco Employee

Re: 7600 1 Gig to 10Gig routing performance problems

Hi,

There are currently no 10/100/1000 that are 100% non-blocking (running all ports at 1000 and line rate).

AS for the 6704, it's not quite 100% non-blocking.

"Fully nonblocking when using only two ports (2 and 4, 1 and 3, 1 and 4, or 2 and 3)

Up to 98 percent nonblocking with all four ports active when using dCEF"

http://www.cisco.com/en/US/products/hw/modules/ps4835/products_data_sheet09186a00801dce34.html

The module's forwarding ASIC (there are two onboard) maxes out at about 26mpps, which equates to roughly 17Gb at 64 bytes. You get better throughput at larger packet sizes, but never quite 100%.

HTH,

Bobby

*Please rate helpful posts.

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