Tech tips

TCP Header (Flags – Urgent Flag & Urgent Pointer) # 2.3

Welcome to Blog Post  # 4

Never bend your head. Always hold it high. Look the world straight in the eye – Helen Keller

Next, we will discuss TCP Flags – Urgent Flags & Urgent Pointer in depth.

Key Takeaway :

  • TCP Urgent Flag
  • TCP Urgent Pointer

1. TCP Urgent Flag & Urgent Pointer

The sender indicates that in a segment, few bytes are urgent, they pass the data to the application without buffering that urgent information.

The urgent field associated with the Urgent pointer. This Urgent Pointer indicates where in the segment the urgent data right after the header.

1.1 Example

The application streams of data to TCP, there may be a number of bytes in that stream in the application wants the remote host, to handle in the same special way.

So TCP creates a segment & puts the urgent data at the beginning of the segment followed by normal data.

The urgent pointer field indicates the end of the “Urgent Data”.

The segment receives, data passed up to its Application. To provide special treatment to those bytes as needed.

Note: Along with Urgent data, the push function is usually involved.

1.2 From the PCAP lets see the details :

These are the same packets, which proceed with the other packet.



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