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9

TL;DR: RFC870 Port zero has been included in the "Network Wide Standard Functions" range since RFC433 in 1972, but has never been assigned. https://www.rfc-editor.org/rfc/rfc433.html Here the range is given as 0-63, but the first assignment is port 1. I can find no "Assigned Numbers" RFC which assigns port 0. In October 1983, for the ...


11

IANA has reserved both TCP and UDP port 0. See the IANA Service Name and Transport Protocol Port Number Registry. IANA is the Internet Assigned Numbers Authority, so all internet numbers, including port numbers, are assigned by IANA. OSes have reserved that port number for an application to request an ephemeral port number by using it as a source port number,...


0

To understand inflation/deflation of cwnd one needs to understand how a sender in a window-based protocol chooses what segments to send. A good illustration for this is found here. Here is the figure from the reference for completeness. Here's my attempt to explain how this figure works in fast recovery. Note, that i have drawn the figure in the opposite ...


0

i think the short short answer is: an example of what sender can do is here rfc6675 First, TCP receiver does not process SACK fields. SACK, as ACK, is sent by the receiver, i.e., receiver creates information in SACK, and is processed by the sender. On the receiver: The actions of the receiver on duplicate packets do not depend on SACK option. TCP receiver ...


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