Per socket data transfer limitations. Are download managers useful yet?

The idea behind breaking up a download into multiple segments with different ranges is for increasing download speed. This works if the server has a per connection limit. A server without that limitation theoretically se开发者_运维百科rvers the same bytes with one or more connections.

My question is if download managers still speed up downloading from such a server or it's just a useless effort. In other words is there any limitations per TCP socket connection by default or not?

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No. There are no limitations per socket. Most OS:es will try to share the bandwidth equally between all sockets unless QoS is specified.

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While a server could throttle bandwidth usage per connection, they typically do not bother. If a response is big enough that it could be effectively throttled then it's about the same impact to slower clients if a fast download just completes sooner.

Splitting a download into pieces may actually hurt your client's performance because of the way TCP operates -- it has a "slow start" mechanism that reduces throughput on new connections.

Websites that implement throttling will typically do so between their various virtual hosts (so that the download site doesn't starve out a more interactive one) or will do so based on the remote IP address.

By far the primary benefit of a download manager is that it will simply continue the download if the connection gets broken.