About MTU Size

[s5uishida]

Hi @linouxis9

To avoid IP fragmentation, it is good to change the MTU of the network interface assigned to PacketRusher's VRF from the current 1464 to 1456. In fact, with the current MTU=1464, I observed IP packet fragmentation when capturing packets from the N3 interface. Just to be safe, I recommend that you will confirm that there as well.

For your reference, I wrote some brief notes [4]-[7] below about the MTU of UERANSIM and srsRAN_4G (NR-UE and UE(4G)).

https://github.com/s5uishida/simple_confirmed_info_for_mobile_network#footnotes

Best regards,

--Shigeru

[linouxis9]

Hi @s5uishida,

I hope you have been doing well!

Thank you a lot for your message as always. This issue was already reported by @yoursunny here: #151 .
The issues actually lies with gtp5g not setting the correct MTU when adding an extension header in the GTP-U packets, but it's something that can be overriden from PacketRusher, so I'll do it.

Thanks and cheers,
Valentin

[s5uishida]

Hi @linouxis9

Thank you for your reply.

I've got it and sorry for pointing this out without checking the past issues.

I would appreciate for your efforts.

Best regards,

--Shigeru