Reducing US/NZ Web Page Latencies
M. Pearson, A. McGregor and J. Cleary
The University of Waikato,
Private Bag 3107, Hamilton, New Zealand
Much of New Zealand's Web traffic crosses the Pacific Ocean on
sub-oceanic fiber channels. This imposes approximately 60ms of
latency in each direction. Because fetching a web page often requires
the fetching of many HTML components and each component requires
several round trip times this latency is multiplied many times in a
typical web page retrieval.
Caches and proxies are often used to reduce the effect of these
delays. Providers of Internet service have several choices in how to
deploy these components. Depending on the architecture chosen the
traffic on the international circuit might be made up of a large
number of independent connections or a smaller number of connections
carrying aggregated traffic. The appropriate approach is not
immediately apparent because there are opposing performance factors.
In this paper we describe a discrete event simulation of the effect of
carrying multiplexed HTTP connections over an simulated NZ/US circuit.
We show that a high degree of multiplexing mitigates against TCP's
bandwidth delay product limits but that carrying every HTTP connection
in a seperate TCP causes a significant increase in delay.
The simulation environment used includes a TCP/IP stack derived from a
real TCP implementation and is driven by data collected from a large
New Zealand web cache.
TCP/IP performance, HTTP, cache, proxy