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If you experience slow downloads, it could be for many reasons. However, they can be different when you experience slow download speed from certain user(s) or when you get slow speeds downloading from every peer. Please try to download from or get filelist of several (at least 10) users before you go on. Note that this faq does NOT cover the case when your downloads won't start at all. If searches and downloads do not work at all you must setup connection properly or enable DC++ in your firewall.

Slow downloads from certain user(s)

This can happen for the following reasons :

    •The upload bandwidth of the person(s) you're downloading from is maxed out. Don't pay attention to the value of the Connection column in the user's list, it's completely subjective and often is not a true reflection on the person's connection type since they can set it.

    •The peer you're downloading from is too far from you (maybe in another continent) and there's too many hops in the connection between you and your peer. Its also possible that either your ISP or the other user's provider has limited overseas bandwidth available. You can check what country is your peer from in the IP column of the Connections window if the setting Guess user country from IP is enabled in the Appearance settings panel.

  1. The person who you are downloading from is using a bandwidth limiter. There are two types: client based and third-party program.
    • Often the clients with limiting capability have set download and upload speed ratios in place to avoid abuse. (ex. If the upload speed limit is set below 6 KiB/s, then the client will restrict the client download speed to a 2:1 ratio). This varies from client to client and obviously not all support upload limiting.  This type of speed limiting only restricts the uploading of files, including user lists. It does not limit chat, private messages, or searches.
    • Users could also be using a third-party program to limit the speed of traffic. This type of speed limiting is absolute; it will limit the speed of all traffic by the user, which can include file transfers, searches, chat, and private messages. Since this type of application does not enforce a download speed:upload speed ratio, it may be more prone to abuse. For particularly slow transfers - 1 KiB/s or slower, it may be to blame.

  2. The person who you are downloading from suffers from one or more constant speed problem described in the next section.

Solution : try to find more sources for your downloads :

  • To gain more possible sources for your download select your download either in the Download Queue or in the Downloads window. Then use the right-click function Search for alternates to see if there are other users have the file shared. In the slots column of the Search results window you can find users with fewer slots used may result in faster speeds - someone with two out of three (2/3) slots free may have more bandwidth available than someone with one out of three (1/3).
  • Sources from search results can be automatically added to the queue if you enable Automatically Match Queue for Auto Search Hits in Queue settings.
  • Automatic discovery for additional sources is also possible if you enable Automatically Search for Alternative Download Locations in Queue settings. Note that some hubs have predefined minimum search interval rules so enabling this function may result no hits for manual searches in these hubs.
  • To minimize the download time make sure you have checked Enable segmented downloads in Advanced settings. With segmented downloads enabled you are able to download the pieces of a file from several sources at the same time.

Slow downloads from every user

If you experience constant slow downloads with DC++ this can be for one or more of the following reasons:

  1. Your Internet connection is shared with others on your LAN and they are using up all the available bandwidth. Tell them to knock it off. =) Also your connection speed to the gateway or router on your LAN can be slower than the available speed from your ISP. It could be for reasons like week signal strength on a wireless connection, broken/old network devices, etc... Try to do a file transfer test within your local network to be sure that it's fast enough.

  2. Your ISP may be limiting your P2P traffic via some method of packet shaping. Call up the ISP and inquire if they do anything with P2P traffic. You can try to connect to ADC hubs and test your downloads there. As ADC is a newer and more efficient DC protocol it can be still unknown to your ISP's throttling system. If the ISP does throttle you, then there is nothing much that can be done to increase the speeds. This is very common at Universities and at the workplace, and is the topic of another FAQ.

  3. You haven't set up your third party firewall or internet monitor software correctly. Some of these security applications may treat P2P transfer as a DDoS flood attempt and tries to defend your computer from it. Try to disable or even uninstall these applications temporarily and test your downloads again. If it helps refer the application's documentation how to make exception rules for DC++. If you have a router its also possible that it has some anti-DDoS or flood protection feature and it may enabled by default. Check the router's documentation or configuration page for a possible option of this kind.

  4. You need to optimize your operating system for your current connection speed. First, close all P2P applications. Next run the DSLReports TweakTest. Once you have optimized it, then run a speed test at DSLReports SpeedTest Page or at the nice looking SpeedTest.Net page (select a test site closest to your location for accurate results). This will give you a good idea what your maximum download and upload speeds are. If you're getting within 10% of your connection speed, that's the best you can get! If you are having trouble with your broadband connection, and it relates to packet loss, excessive latency, or Internet or ISP congestion, running the Line Quality Test may help find the cause (requires logon, free signup).

  5. Your Internet connection is DSL, cable, or satellite one with an asymmetrical connection speed, such as 768/128 Kib/s or 3.0 Mib/s / 256 Kib/s. On such connections, if you upload near the speed of your upload limit (16 KiB/s in the case of the 768/128 connection), it may affect the speeds of your downloads, no matter how much larger your download connection is. If this is happening, you can use the built-in transfer limiting function to set the maximum upload rate value slightly lower than your available upload speed (eg. to 15 or 14 KiB/s in the case above).
    If you aren't allowed to use upload limiting you can also experiment with changing the size of Socket Write Buffer in Experts Only panel of DC++ settings. It defaults to 8 KiB and you can try to change it to a smaller value. You should specify the value in bytes and you may have to try several values to test what size suits your connection best. Note that you should restart DC++ to changes take effect.

  6. Your copy of Windows XP, 2003 Server, Vista or 7 has the "QoS Packet Scheduler" enabled so you are not able to use some reserved bandwidth for download. Follow this guide to disable QoS in XP or this one to disable QoS in Vista or Windows 7. Windows 2000 does not come with QoS. Some routers also have QoS capabilities, but shouldn't be enabled by default. Please consult your router's manual for more information.

  7. Your computer is infected with malicious software which altered the low level network settings of your operating system. This is common when your Windows become infected with spy/adware. Even they are disinfected, their destructive modifications usually still remain. You can follow the official guided help from Microsoft how to restore these settings here and here.

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by USR56K See Profile edited by eMTee See Profile
last modified: 2012-11-06 12:31:50