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Bug 1.8.2: ignoring global maximum connections limit!


jamarr

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I am having a serious issue with uTorrent and the number of globally allowed connections. Here's the deal, I set my the global maximum connections to 150, and I set the maximum number of peers per torrent to 150 also. Per these descriptions, I expect no more than 150 connections to be allowed globally. And if I only have 1 torrent downloading/uploading, I expect no more than 150 connections for that torrent. The problem is that when I increase the number of available torrent slots, the number of connections going out increases beyond 150 globally allowable connections!

I have tested this using my router, with me being the only person on the network. It seems like the maximum number of connections per torrent is overriding/ignoring the maximum number of globally allowed connections. For example, when I made 2 additional torrent slots available my router jumped from ~150 to over 450 active connections!

This makes it impossible to use uTorrent to download more than 1 torrent at a time when other users have to use my network, even if they are only browsing the web.

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I am using the DD-WRT router software on a Linksys router. Among the many cpu, memory, and network statistics available one of the available monitoring tools is "Active IP Connections" which shows how many total active ip connections are going through the router.

An obvious side-effect of this is that I can download 1 torrent at time while my network is being used by multiple clients, but as soon as I increase the number of available torrent slots from 1 to N people start trying to bite my head off. **Note that the maximum amount of bandwidth holds firm (does not increase), but the increase in the number of connections is more than my router can efficiently manage and causes too much congestion slowing down the whole network.

As I monitor the number of active ip connections on the router, when I only have a single torrent slot available the number active of ip connections on the router reflects what I would expect (150-200, depending on if i have any websites open). As soon as I increase the number of available torrent slots (and actually have additional torrents to download) that number increases seemingly at the same rate as allowed connections per torrent, thus ignoring the global maximum limit.

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not yet. I assumed that uTorrent wouldn't bother opening any more connections if I was already consuming the global maximum, even if I made more torrent slots available. i did notice that after closing utorrent it took a while for the number of active connections to diminish, so that may be partly to blame. I will test that out and post my findings later.

** it looks like that was the problem. I was downloading several smaller sized torrents, and when one torrent finished and another started the number of active connections only increases; it takes some time (sometimes a long time) for the existing connections to dissipate. when the number of torrents being download simultaneously increases, the problem is exacerbated.

unfortunately I do not know of any methods of resolving this issue on the router side. I wonder if this is issue is router-specific, or router-class specific? I suspect that if there where anything you could do on the uTorrent side that you guys would have already implemented it?

at least I know what the problem is now...thanks.

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Global maximum number of connections is only counting connected peers and seeds.

It is not counting UDP streams (used possibly by DHT and Resolve IPs) which routers often mistaken as connections. (sometimes PER packet!)

It is also not counting incoming connection attempts or tracker updates.

Does uTorrent's Help, Show Statistics report anything amiss?

Have you disabled Resolve IPs and DHT to vastly decrease uTorrent's use of UDP packets? (...which are the common reason why routers overload)

Also have you tried the 2nd link in my signature?

It could also be uTP connections which uses UDP as well, though that'd likely cause problems with just 1 torrent active.

Teredo/IPv6 also uses UDP, so check that too.

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@jamarr: At best, you'd probably be able to decrease the timeout interval for connections in the router configuration so that entries are cleared off the connection table more quickly. Other than that, it's really just a router thing (in many routers) where they seem to track connection for an extended period of time.

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  • 3 weeks later...
** it looks like that was the problem. I was downloading several smaller sized torrents, and when one torrent finished and another started the number of active connections only increases; it takes some time (sometimes a long time) for the existing connections to dissipate. when the number of torrents being download simultaneously increases, the problem is exacerbated.

I would advise you to use the logger to monitor what uT acutally is doing. Right click in the logger tab and select 'Peer Traffic Logging' --> 'Log disconnects'. Then start downloading a torrent with enough seeds/peers so your # of connections will increase up to your max limit. You may follow the increasing by adding the seed + peers # left side of the # in brackets. Also you may check by clicking menu Help--> Show statistics and repeat this regularly to follow the connecting state. In the logger you should follow the reasons leading to disconnections like offline (timed out) or inactivity or is seed etc. At some point the connections should be refused because of the max connection limitation which will be clearly indicated in the logger messages.

Another thing you might want to test / observe: disconnection due to inactivity. You should go to the peers tab and right click on the headers bar, then select the 'inactive' column to be shown (hidden by default). Now if you did not change something in the advanced options the oldest activity should be no more than 6 min. You should observe that uT is closing every connection which is inactive for more than 5 min on a 1 min basis. So every min the older (inactive) connection should be droped and this is also visible in the logger disconnection messages.

If you want to push the game further you might wait until you have let's say 150 connections for a max of 150 allowed. Than you reduce your max to say 100 and follow what will happen with the methods I explained above. You should see that starting from that moment uT will refuse any new connection because of max connection reached. The "5 min purge" should remain the same as before so slowly the older connections will be kicked out AND no new connection will be allowed, so the total amount of connections will have to be reduced (besides drop of connections for various other technical reasons I don't want to detail here) down to 100 in this example. Then you should be able to observe how uT will "open the door" again for incoming (and outgoing) connections. You may want to add the flag 'Log incoming connections' (and/or outgoing) so see when new connections are allowed / established and how (encrypted etc)...

This should give you a clear insight / picture of what uT is doing in the background concerning the connection management. It should help you to make some parallels with your router configuration / information.

Let me know if it helped you. :)

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