Device and method for transferring identification and/or data flow control information between devices

A method for interfacing between link partner devices, comprising:

• obtaining a data packet;
• fragmenting the packet into multiple fragments if a size of the packet is greater than a maximum fragment size;
• generating a packet control header for the packet or each fragment of the packet, wherein the packet control header includes at least one of:
• a sub-port ID field, an extension field type field, or an extension field;
• and
• sending the packet or the fragments of the packet with the packet control header to a link partner device.

Non-transitory computer readable storage media comprising instructions that, when executed by a processor, cause a system to perform operations comprising:

• obtain a data packet;
• fragment the packet into multiple fragments if a size of the packet is greater than a maximum fragment size;
• generate a packet control header for the packet or each fragment of the packet, wherein the packet control header includes at least one of:
• a sub-port ID field, an extension field type field, or an extension field;
• and
• send the packet or the fragments of the packet with the packet control header to a link partner device.