UDP Packet Latency: RLC AM vs RLC UM

[praghur]

Hello. 

In the indoor OTA lab, I am using x310 as gNBs and COTS UE to send UDP packets from one UE to another via CN. I am using qos.yml file (attached) to change RLC mode to RLC UM. 

Using wireshark captures, I see that not running the qos.yml defaults to RLC AM. However, when I change the RLC mode to RLC UM via qos.yml, I do not see much change in the latency obtained of the UDP packets sent across the UEs via the core network. The Github repository used for this experiment: https://github.com/praghur/srsran_OTA/tree/IProuting

Please see some results below calculating latency:

RLC AM:

Command used at gNB Node: sudo /var/tmp/srsRAN_Project/build/apps/gnb/gnb  -c /local/repository/etc/srsran/gnb_x310_1.yml

:~$ traceroute -U -f 2 -m 2 -p 33435 10.45.4.10
traceroute to 10.45.4.10 (10.45.4.10), 2 hops max, 60 byte packets
 2  10.45.4.10 (10.45.4.10)  27.759 ms  27.727 ms  39.661 ms

RLC UM:

Command used at gNB Node: sudo /var/tmp/srsRAN_Project/build/apps/gnb/gnb  -c /local/repository/etc/srsran/gnb_x310_1.yml -c /local/repository/etc/srsran/qos.yml

:~$ traceroute -U -f 2 -m 2 -p 33435 10.45.4.10
traceroute to 10.45.4.10 (10.45.4.10), 2 hops max, 60 byte packets              
 2  10.45.4.10 (10.45.4.10)  28.692 ms  28.660 ms  34.523 ms

What am I missing here? Is there any reason why I do not much difference in latency between two RLC modes?

Thanks in advance.