[c-nsp] Packet Fragmentation
Lukas Tribus
luky-37 at hotmail.com
Thu Feb 12 14:20:05 EST 2015
> Currently, using Cisco 3800's. Unfortunately, because the traffic is UDP,
> mss adjust can't be used to adjust the frame size. The fragmentation is
> unavoidable as this involves VPNs and the applications can't be adjusted to
> try smaller sized frames.
>
> Are there any documents that show the impact for each platform? I can find
> pps, throughput, etc... but nothing says how fragments impact things.
Of course not, its software processed and unpredictable.
Avoid MTU mismatches, switch to IPv6, set the DF-bit on UDP traffic (to invoke
PathMTU) - or - if thats not possible at all, buy boxes with bigger CPU. Behavior
will still be unpredictable, but an ISR G2 can probably fragment a few mbit/s of
traffic.
If PPPoE is the problem, use rfc4638/ppp max payload.
Lukas
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