Networking – TCP segment of a reassembled PDU

internetnetworkingtcpipwireshark

In wireshark sometimes I see this:

478195  5738.896809 192.168.1.79    61.213.44.124   TCP [TCP segment of a reassembled PDU]

What is a PDU? Was it reassembled? What does this mean?

Best Answer

A "PDU" is a "Protocol Data Unit." One unit of information being transferred in accordance with a given protocol (e.g., "login USERNAME very-long-base64-encoded-authentication-data" then wait for server to respond) will be disassembled into many packets (smaller pieces) if it's too large to fit in one packet (or segment in this case).

This is normal and is just TCP/IP working as designed.

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