We where talking about pings yesterday and fast path which I found a bit difficult to explain, so I went and found this, which is translated from German:
fast path is the name for an option for the decrease of the latency with ADSL connections.
Advantages are a better response time with on-line plays, a smaller language delay and better echo killing with Internet Telefonie, as well as a slightly liquid Web use. As disadvantage the effective data transmission rate can sink in rare cases.
See Here
I think the term in English is Interleaving:
See Here