Multilink PPP vs ping times.

OK, I'm new to multilink, so perhaps I'm missing something obvious...

Two routers with 3 point-to-point T1s between them. One is a 7206VXR, the other is a 2821. I've bundled them together with PPP Multilink, intending to create a single fat pipe between the sites. (To replace the single T1 we'd been using, which will join the bundle once it's behaving properly.) I'm getting the increased overall bandwidth ok, but ping times have gone down the toilet. On a single T1, average ping time is 6ms; on the bundle it's about 34ms. If I do multiple pings for an extended time period, it repeatedly speeds up and slows down over about 1-second intervals. CPU times are reasonable: 2% on the 7206 and 3% on the 2821.

On 7206 12.2(4)BW1: interface Multilink1 ip address no ip route-cache cef delay 2000 no cdp enable ppp multilink ppp multilink fragment-delay 20 ppp multilink interleave multilink-group 1 interface Serial6/1:0 no ip address encapsulation ppp no fair-queue ppp multilink multilink-group 1 (same for s6/2:0, s6/3:0)

On 2821 12.4(3g): interface Multilink1 ip address delay 2000 ppp multilink ppp multilink fragment delay 20 ppp multilink interleave ppp multilink group 1 interface Serial0/0/1:0 no ip address encapsulation ppp no fair-queue ppp multilink ppp multilink group 1 (same for s0/1/0:0, s0/1/1:0)

Any ideas?

Reply to
Mike Dorn
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Typically this would be because of competing traffic on the link. Remember that while your total bandwidth is (almost) tripled, individual packet fragments are still sent at T1 rates. You will need to configure quality of service if you have traffic which is overly delay sensitive (such as VoIP).

Good luck and good hunting!

Reply to
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