Transmission rate though MPLS

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Nov 25th, 2007
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Hi all,

Hope someone could help me in this. I've set a rate-limit on the CE router at 6Mbps. However, using software to generate traffic at 10 Mbps would push the limit of the line at 5.2-5.4 Mbps, 15-20% lower than the maximum bandwidth. I know that labels and other overheads with packet loss could attribute to the lower throughput, Is there anyone who knows the exact percentage of maximum throughput over MPLS?

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swaroop.potdar Mon, 11/26/2007 - 12:31
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Jason, for every CE packet going through the MPLS core there would be a over head of 8 bytes min. The throughput may vary based on the packet size you used for traffic generation. (smaller packet sizes more overheads lower throughput, bigger packet sizes close to 1500 lower overheads better throughput).

But again looking at your test setup, youhave done a ratelimit at the CE ingress of 6mb. So overall your line rate should not decrease but increase irrespective of smaller or bigger packets, when you observe in the MPLS core (PE-P connection or P-P connections)

If you are veryfying at the CE egress interface then you can verify agian whether you are sending steady rate traffic or bursty traffic through the software. If you ae sending bursty traffic and you havent set the right burst values then it may be getting dropped resulting in a lower egress line rate.



jason_leong7 Mon, 11/26/2007 - 17:49
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Hi Swaroop,

Thanks for your reply.

What if I was sending a steady rate traffic?

hmm...on the other hand i just remembered that i've set a packet size of 65535? It still shows a drop of throughput about 15-20%.

swaroop.potdar Mon, 11/26/2007 - 19:28
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Jason, I am not sure about the packet size of 65535. If you have a receiver probe for your software can you verify whether you are receiving actually 5.2 to 4 Mb or 6 Mb. And what you are seeing is purely cosmetic.




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