TCP and UDP

  • Ethernet frame
Dest MAC Srce MAC Dest IP Srce IP Dest Port Srce Port Sequence ACK Data FCS
  • IP Packet - The chunk of data left the moment the frame comes off the network card
Dest IP Srce IP Dest Port Srce Port Sequence ACK Data
  • TCP & UDP
Dest Port Srce Port Sequence ACK Data


Understanding Ports

dest IP srce IP dest Port srce Port
  • The destination port number is set by the type of application you are using
    • Web server : 80
    • FTP server : 21
    • email server : 110
  • Port numbers 0 to 1023 are called well known ports, used for fixed applications and locked in stone
  • The source port number is generated as an ephemeral port by the client
    • It’s incrementally generated
    • It’s got to be a number 1024 up to 65,000