Zhiyong,
> When I use vxlan in both VM and physical machine , packet
> drop issue is come across, after setting VPP MTU = 1600, this issue will
> disappear. As we all know, some of routes on the network doesn’t support
> more than 1518 bytes packet.
> Should I try to use IP fragment in this case? Or any other better solution?
> Does VPP IP fragment work now? If yes, Could you show me how to configure?
> Thank you very much.
Fragmentation now works. Currently both for IPv4 and IPv6 packets are
fragmented in ip{4,6}_rewrite. Note that only locally originated IPv6 packets
can be fragmented, and only IPv4 packets with DF = 0.
Assuming the above two restrictions are adhered to, if the VXLAN node sent
packets larger than the outgoing interface MTU they should be fragmented now.
There is no configuration for fragmentation. (Although I am thinking of adding
a knob, with default disabled).
For reassembly, VPP has a short-coming, It can only reassemble as an input
feature, meaning all fragments, even though not destined for the VPP instance
itself are reassembled.
I think Juraj is working on a fix for that.
The next steps for tunnels, to help avoid fragmentation is to add some sort of
tunnel path MTU discovery.
But in short, you are much better off with a well managed MTU, than you are
with fragmentation.
See our draft in intarea for a list:
https://tools.ietf.org/html/draft-ietf-intarea-frag-fragile-00
Cheers,
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