There were a number of TCP enhancements that went in around the 5.1

timeframe which impact the way window scaling works as well.

Also, do you have path-mtu enabled on all the devices?

on XR you want something like this:

tcp selective-ack

tcp window-size 65535

tcp path-mtu-discovery


ip tcp path-mtu-discovery

ip tcp window-size 65535

> interface GigabitEthernet0/0/1 no ip address


> service instance 100 ethernet

> xconnect x.x.x.x {VC_ID} encapsulation mpls mtu {}


> But If I configured the below

> l2vpn xconnect context {NAME}


> There is no option for the MTU under it



You have to configure it on the pseudowire interface: