[e2e] Question about RFC 2581

[Michael Welzl]

Dear all,

I have a question regarding the congestion avoidance part of
RFC 2581 - it is probably a stupid one, so please don't shoot me   :)


RFC 2581 states:

   One formula commonly used to update
   cwnd during congestion avoidance is given in equation 2:

      cwnd += SMSS*SMSS/cwnd                     (2)

   This adjustment is executed on every incoming non-duplicate ACK.
   Equation (2) provides an acceptable approximation to the underlying
   principle of increasing cwnd by 1 full-sized segment per RTT.  (Note
   that for a connection in which the receiver acknowledges every data
   segment, (2) proves slightly more aggressive than 1 segment per RTT,
   and for a receiver acknowledging every-other packet, (2) is less
   aggressive.)


My question is:

Why is (2) slightly more aggressive than 1 segment per RTT if the
receiver ACKs every segment?

I just don't get it.


Cheers,
Michael