Subject: Why can download manager can help?

From: KY Wong <[email-masked]>
Date: Thu, 31 May 2001 12:00:06 +0800

Some download managers such as NetAnts claim to be designed to maximize
throughput by making multiple HTTP connections, each of which downloads
a separate part of a single big file.

I wonder why doing this is helpful.

Suppose a user connects to the Internet via a 56kbps line. His first
HTTP connection should consume all the bandwidth of his line, how can
the multiple simultanous connections help?

Assume the Web server haven't limited the transfer rate for the requests
to it. If the user had a 1.5Mbps line now, then his first HTTP
connection could still transfer the file at 1.5Mbps (assume the network
is not the bottleneck), how can the multiple connections help?

Now suppose the network is the performance bottleneck (maybe network
congestion), then no matter how many simultanous connections are used,
the overall transfer speed is limited by the network. How can the
multiple connections help?

However, by real experience, this kind of download manager is helpful
and reduce the overall respond time. Why? Is it related to the HTTP 1.1?

Thank you for your attention.

Angus Wong

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From: Jon Mansey <[email-masked]>
Date: Thu, 31 May 2001 09:21:34 -0700

This is especially relevant to satellite IP networks where the 
latency affects each TCP connection by limiting the maximum 
throughput to an un-modified TCP stack on a client.

Opening multiple parallel TCP connections is a way "pull" more 
bandwidth on "one session".

You're right though, it probably wouldnt improve things over low 
latency 56k or T1 lines.

jm

>?Some download managers such as NetAnts claim to be designed to maximize