Advantages of TCP MSS
TCP MSS has a number of advantages over the path MTU discovery (PMTUD) method.
The path MTU Discovery (PMTUD) method relies on transmission of multiple ICMP "Fragmentation Needed" (Type 3, Code 4) messages. Notably, many network devices block all ICMP messages.
Characteristics of TCP MSS:
- MSS is a parameter in the TCP options field, which comes between the TCP header and the payload (data) of the packet.
- It specifies the largest amount of data that a device can receive in a single TCP segment.
- It does not include the IP header and TCP header.
- TCP MSS is an announcement, not a negotiation.
- TCP MSS option is sent during the three-way handshake by both sides.
- TCP MSS can be different in each direction.