[SR-Users] Amazon VPS, long UDP packets are seen by sniffer, but don't reach application

[Tristan Mahé]

Le 12/02/2015 13:08, Andrey Utkin a écrit :
> 2015-02-12 22:33 GMT+02:00 Tristan Mahé <t.mahe at b-and-c.net>:
>> Hi,
>>
>> bad checksum may be caused by the virtual network adapter that does not
>> perform hardware checksum. I had this issue on a kvm test setup.
>>
>> MTU is to be looked at, as udp does not handle very well packet
>> fragmentation ( to say the least ). Could you reproduce the same issue
>> using an openvpn tcp virtual link between your two servers ?
> Hi, and thanks for your comment.
> Will definitely try VPN, I just wonder why is it so that
>
>> udp does not handle very well packet fragmentation ( to say the least )
> ? My first action was to fill a ticket at rtpengine, but developers
> replied to me that this mechanism is known to be reliable, and that
> they don't consider adding TCP version of interface. I haven't tested
> this case on a lot of different networks, but for now this issue seems
> specific to Amazon.
> Anyway, will try with tunnel (which is, howevre, a workaround, not a solution).
>
The thing with UDP fragmentation is that it depends on the routers in
the path, I've seen a lot of fw able to deal with TCP frag, but not with
UDP...

If the TCP tunnel resolves the issue, then you know where the issue lies
and what to do to resolve it ( propose a pull request with support of tcp ).

Let us know the results of your tests, it's interesting !

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