📖 IT Bible

TCP Control Flags

  1. URG (Urgent) - a value of 1 here indicates that the segment is considered urgent and that the urgent pointer field has more data about this
  2. ACK (acknowledged) - a value of 1 means that the acknowledgement number field should be examined
  3. PSH (push) - transmitting device wants the receiving device to push currently-buffered data to the application on the receiving end as soon as possible
    • Buffer - computing technique where a certain amount of data is held somewhere before being sent somewhere else
  4. RST (reset) - one of the sides in a TCP connection has not been able to properly recover from a series of missing or malformed segments
  5. SYN (synchronize) - used when first establishing a TCP connection and makes sure that the receiving end knows to examine the sequence number field
  6. FIN (finish) - when this flag is set to one, it means the transmitting computer does not have any more data to send and the connection can be closed

Three-Way Handshake

  1. computer A sends TCP segment to computer B with a SYN flag sent
  2. computer B then responds with a TCP segment where both SYN/ACK flags are set
  3. computer A responds again with just ACK flag set

Pasted image 20260607175734