Sunday, May 29, 2011

About TCP protocol flaws

While not about security itself, this topic is about very related question - performance of internet communication (and performance is closely linked to security).

The article discusses alternatives to TCP and includes description of TCP design as part of the discussion. The flaw of the design is caused by the strategy used by TCP stack when detecting undelivered packets - it reduces transmission rates dramatically and increases them back in small steps. This leads to very uneven delivery rate and ineffective transmission in the end.

"Another issue of current TCP implementations is the fact that the AIMD algorithm constantly pushes network loads into an overflow condition. This occurs because the only feedback that the sender gets from the receiver is about whether or not packets are lost along the way. If packets aren’t lost, then the assumption is that the sending rate can be increased; if packets are lost then the sending rate needs to be decreased. In this situation, senders are constantly ramping up data rates to the point when buffer overflow occurs."

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