Jumbo Frame Support Info

If you enable Jumbo Frames within a Layer 2 switching infrastructure, the following table shows what will happen depending on a hosts NIC settings:

Host A & Host B: Jumbo Frames Enabled: =>TCP and UDP will communicate using Jumbo frames.

Host A: Jumbo Frames Enabled, Host B: Jumbo Frames Disabled

=>TCP will communication will use non Jumbo (1514 byte) frames. During the TCP 3-way handshake hosts indicate to each other in the initial SYN and SYN-ACK (using the TCP Options Maximum Segment Size (MSS) field) what size segments they can support. A sender will use the lower of the received MSS and the MSS of its outgoing NIC.

=>UDP communication could fail from Host A to B as A could send too large a frame that B can not support. A wireshark trace on Host B would not even show the traffic as the NIC would discard it.