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CEF Per-Packet over 2 DS-3's


I have 2 P2P DS-3's and they are setup with CEF per-packet, I also have a few T-1's as a backup (MLPP), however I only get 30 MB transfer (peak) from the two DS-3's, looking at traffic they ARE load balancing but I never get the full bandwidth, any ideas?

Thank you!

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Re: CEF Per-Packet over 2 DS-3's

There are several factors that may be involved in your situation. One factor is the type of traffic. If the traffic is TCP based packets then you are constrained by the TCP window size. This is sometimes referred to as the bandwidth delay product. You can send a certain amount of traffic and then you must wait for an acknowledgement before you can send more traffic. The longer the link and the more delay the lower the effective throughput.

You may also be impacted by out of order packets. When you specify per packet load share you greatly increase the possibility of out of order packets. The impact of out of order packets may vary depending on the application. But in many cases when there is an out of order packet the end stations must back up and retransmit to get packets in order. The impact of diminished throughput.

It may also depend on what is generating the traffic and what is receiving the traffic. It may be that one end or the other is constrained (perhaps by processing capability, or storage access requirements, or something similar) and is limiting the amount of throughput.

I assume that you specified per packet for its supposed more equal loading of the links. If that is the goal I believe that you might get better performance if you put both DS-3s into multilink PPP which will provide very equal load on the link and will eliminate the out of order packet issue.



Community Member

Re: CEF Per-Packet over 2 DS-3's

Thanks Rick, but when I tried it on the DS-3's MLPP never comes up, looking at debugs it shows that:

Jul 25 23:38:16.834: Sey/y MLP: Request add link to bundle

Jul 25 23:38:16.834: Sey/y MLP: Adding link to bundle

Jul 25 23:38:16.834: Sey/y MLP: Bundle in different multilink group

Jul 25 23:38:16.834: Sey/y MLP: Link not added to bundle

The T-1's are also bundled with MLPPP but are on a different MLPP group all together, the DS-3 MLPPP never came up. I have a feeling that a router and a peer can only be in one group unless you use ppp auth chap?

Community Member

Re: CEF Per-Packet over 2 DS-3's

For anyone else that is interested - I removed the MLPP from the T-1's (bundle) and added the DS3's to the bundle instead, only one bundle per peer it would seem.

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