Multiplexing/Demultiplexing

Core

Port Number

segment(数据段)

unit of data exchanged between transport layer entities

• TPDU: transport protocol data unit

segment

• segment header
• application-layer data

Multiplexing(多路复用)

gathering data from multiple application processes, enveloping data with header(later used for demultiplexing)

Demultiplexing(多路分解)

delivering received segments to correct application layer processes

multiplexing/demultiplexing

• based on sender, receiver port numbers, IP addresses

  • source, destination port in each segment
  • well-known port numbers for specific applications

• TCP/UDP segment format

  • source port(2 bytes)
  • destination port(2 bytes)
  • other header fields
  • application data(message)