The Urgent Flag(URG) is set whenever the sender's Application Layer wants to send some urgent data to the receiver. In this case, the Transport Layer does not wait for enough data to achieve maximum segment size. Now, my question is how do the routers in between recognize that the packet needs to be forwarded urgently(they do not have the transport layer)?

  • $\begingroup$ I'm not even confident this would be on-topic over at NetworkEngineering@SE. $\endgroup$
    – greybeard
    Commented Mar 28, 2020 at 7:34
  • $\begingroup$ This was asked at an interview for recruitment for the post of a scientist at one country's most prestigious organization. Though it may have been a tricky one to check the confidence level. $\endgroup$
    – Kanishk
    Commented Mar 28, 2020 at 12:13

1 Answer 1


They don't. The urgent flag doesn't affect the handling of the packet by routers. The urgent flag is an instruction to the TCP stack on the destination host, not an instruction to routers along the path.


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