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Re: Problems with Internet Download Manager and Squid 2.7 Stable 9

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On 19.01.2012 07:16, Saiful Alam wrote:
Hi,
I am using Squid 2.7 Stable on Ubuntu 10.10 x64

Files like
 mp3 which have a refresh_pattern defined, and downloaded within the
browser download manager is cached, but if I download the file with
Internet Download Manager 6.05, the file is not cached. Note that IDM by
 default uses 8 connections to download a single file. Again, if I
reduce the default connection number to 1, and try to download again
with IDM, then the file is cached instantly.


"cached instantly" is a bit of a strange description. Surely it requires download time before caching? or did you means something else entirely?


Consider what that download manager is doing. Splitting the file into 8+ pieces and requesting each of those pieces as different HTTP requests. Squid cannot cache partial files, only whole files.


You can check for the download manager User-Agent value with a "browser" type ACL and also a "maxconn" type ACL to block more than 1 connection at a time by it. The range_offset_limit and abort settings will also help with these partial file requests. Their use is best known for WU, but applies to any big partial file. http://wiki.squid-cache.org/SquidFaq/WindowsUpdate


Alternatively you can balance the users mistaken perception of DL manager benefit with delay_pools which use the "browser" ACL type and slow its rate of download so that users see it as worse than normal traffic when they use it. Migration away from the manager

It is polite to inform your users about the proxy and the effect these managers are having before going to such extremes. If you can make them understand that they get *faster* downloads by working with the proxy cache sharing. You can perhapse advise alternative methods of getting fast download at the same time to encourage the change. see below.


Most users in our
network have IDM as their primary download manager, and if we can't
cache objects downloaded with IDM, then :((((((((((((((((


This is a strong sign that they perceive the multiple connections the manager provides as a faster network connection than the proxied traffic. I've usually seen this sort of perception growing out of the old browsers limitation of only opening ~2 connections to a proxy, which makes things appear really slow when big objects are filling one of the connections. There is a "connections to server" setting in browsers which can be raised to 8-10 to double or quadruple the bandwidth availability for each user without needing a manager to do it specifically. NP: be careful you have enough FD available on the Squid before letting them know about that.

Amos


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