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Site-toSite 2801 VPN with AIMs: Why the jitter?

I have 2 2801s each with AIM-VPN/EPII-PLUS modules in them. According to the Cisco documentation, they should be able to support VPN at 100Mbps. We have a 3xT1 Internet connection at one site and DS3 on the other(hub). Both Internet connections are hosted on routers other than the 2801s, with no apparent drops anywhere, both using the same carrier.

The issue that I am seeing is a large amount of jitter. The average RTT for a 64 Byte ping is ~36msec. Quite often though I will see something like this:

Reply from 10.3.5.1: bytes=32 time=41ms TTL=125

Reply from 10.3.5.1: bytes=32 time=71ms TTL=125

Reply from 10.3.5.1: bytes=32 time=37ms TTL=125

Reply from 10.3.5.1: bytes=32 time=144ms TTL=125

Reply from 10.3.5.1: bytes=32 time=66ms TTL=125

Reply from 10.3.5.1: bytes=32 time=36ms TTL=125

Reply from 10.3.5.1: bytes=32 time=36ms TTL=125

Reply from 10.3.5.1: bytes=32 time=45ms TTL=125

Reply from 10.3.5.1: bytes=32 time=36ms TTL=125

Reply from 10.3.5.1: bytes=32 time=36ms TTL=125

Reply from 10.3.5.1: bytes=32 time=36ms TTL=125

Reply from 10.3.5.1: bytes=32 time=45ms TTL=125

Reply from 10.3.5.1: bytes=32 time=67ms TTL=125

This bothers me a great deal. This seems to begin to occur once we ramp up to pushing at least 800Kbps in either direction, with the jitter increasing as we push through more data.

I do no see any packet drops on interfaces or within the crypto stats.

Any ideas?

Thanks, Russ

1 REPLY
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Re: Site-toSite 2801 VPN with AIMs: Why the jitter?

The issue may be due to network congestion, improper queuing, or configuration errors, this steady stream can become lumpy, or the delay between each packet can vary instead of remaining constant.

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