[Iccrg] ctcp draft

[Douglas Leith]

Some additional comments on the ctcp internet draft.   In trying to  
write out the ctcp algorithm as pseudo-code one or two issues have  
come to light that I think would benefit from clarification.

1.  How is rtt to be measured ?  Is it the standard rtt measurement  
as per RFC 1323 and already used for RTO ?  Or does ctcp require  
something else e.g. with some kind of filtering used.

2.  How is baseRTT measured ?  Presumably its the lowest rtt measured  
over the connection lifetime, or something like that, but it would be  
helpful to make this explicit since its so central to the operation  
of the delay-based component of the algorithm.

3.  dwnd is updated each "round", but a "round" is not defined.  I  
presume a round means something like an update once per RTT (as per  
Vegas) but maybe that's wrong.  If it is once per RTT, should that be  
once per cwnd worth of packets or really once per RTT (and which RTT ?).

4.  How is slow-start handled ?    E.g. what does dwnd to during slow- 
start,  when do we exit slow-start (when the reno cwnd reaches  
ssthresh, or when the overall cwnd reaches ssthresh, or something else).

Doug

Hamilton Institute
www.hamilton.ie