[[TCP (Transmission Control Protocol)]] [[TCP Flow, Error and Congestion Control]]

• Up to 40 bytes
• Each option is a 4 byte field as HLEN in TCP header increments by 4

Single Byte Options (kinds)

• (EOP) End of option list
  • Signifies the end of options segment
• (NOP) No operation option
  • Acts as a padding to ensure 4 byte boundaries based on other options ### Multi-byte options
• (MSS) Max segment size
  • Defines the max size of data that can be received by the destination TCP target
• (WSS) Window Scale Factor
  • Used to scale the value in the Windows Size field in the header
  • New Window Size = WindowSize x 2^ ScaleFactor
  • Largest value allowed is 14 (00001110)
• (TS) Timestamp option
  • Used to calculate the RTO
• (SACK) Selective ACK
  • Determines whether SACK can be used and how selectivity works