The MSS Adjust feature is used to prevent fragmentation of TCP traffic. The TCP synchronize/start (SYN) packets are intercepted and their MSS value inspected to ensure that it conforms with the configured MSS value. If the inspected value is greater than the value configured in the VSR BR, the MSS value in the packet is lowered to match the configured value before the TCP SYN packet is forwarded.
As the end nodes governing the MSS value are IPv4 nodes, this feature is supported for IPv4 packets only.
An MSS adjust is performed in both the upstream and downstream directions.