[e2e] MSS and cwnd increase

Salman Abdul Baset salman at cs.columbia.edu
Sat Jul 1 13:22:09 PDT 2006

I am wondering how the Linux 2.6 updates its congestion window when a CBR
stream (packet size << MSS) is sent over TCP.

In general, if I am sending 100 packets every second with a packet size
of one byte and assuming each packet is ACKed, then increasing window by
one every RTT (during congestion avoidance) will artifically inflate the
window. Thus, the cwnd calculation should not assume that the last packet
sent contained MSS bytes of data.

The rfc and the code and seem to imply that cwnd increase is MSS-based. I
haven't confirmed either way (still testing it) and will like to know:
1) What is the RFC suggested way?
2) How Linux 2.6 is implementing it?


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