[nsp] latency vs throughput

Lincoln Dale ltd@cisco.com
Mon, 16 Sep 2002 08:04:04 +1000


At 06:21 PM 14/09/2002 +0530, pakucable wrote:
>which one is true ??
>
>1) Latency increase ---> throughput(bandwidth usage) increase
>2) Latency decrease ---> throughput(bandwidth usage) increase

it depends on the context.

in reality, Latency & Throughput are two completely different metrics 
associated with "performance".
Latency isn't related to Throughput and vice-versa.

having said that, if the context is "related to TCP", then the most likely 
correct answer is (2) --
TCP is a window-based protocol with maximum performance capped by the 
"bandwidth * [rtt] delay" hitting the maximum number of bytes outstanding 
on the wire allowed by the TCP window-size.

given a suitably-sized TCP window-size as well as enough 'go-fast' TCP 
options (typically RFC 1323 including S/ACK & Fast Retransmission), most 
real-world increases in latency can be made to result in minimal decrease 
in throughput.


cheers,

lincoln.