[c-nsp] Fragmentation causing low throughput on ASR9k

[Atif Sid]

Setup:

Testset A <GigInt------ *LINK MTU 9000 *---GigInt> non-Cisco device <GigInt----
*LINK MTU 4000---*GigInt> *ASR9K *<---- *LINK MTU 9000*-----> Testset B

Bi directional stream going through with the packet size of (*5000 bytes -
fragmentation allowed*) traffic is 900 MB.

Stream from TestsetA is fine 900 MB is reaching to Testset B; (non-Cisco
device is fragmenting 5000 byte packet due to interface MTU 4000 but
transmitting traffic with no loss; low CPU usage.

Stream from TestsetB is getting dropped by ASR9k egress interface (connected
to non-Cisco); ASR9K is receiving all the traffic 900 MB but sending out
only 70 MB to the MX. we have checked LPTS no counters incrementing.

 Tested 7606 replacing ASR9k results are similar traffic around 70- 80 MB.
on ES+ card.


Has anyone seen this behviour? can we modify config to make it working?