Slow download speeds
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.
Slow downloads from certain user(s)
Reasons connections with some users may be too slow:
The upload bandwidth of the peer you are downloading from is maxed
out. Don't pay attention to the value of the Connection
column in the user list: it is subjective and often not an accurate
representation of the user's actual speed.
The peer you are downloading from is too far from you (maybe on another
continent) and too many hops are necessary to connect you
to your peer.
It is also possible that either your ISP or the other user's provider has
limited overseas bandwitdh available.
You can view your peer's country in Transfers area (provided the
Guess user country from IP setting is enabled).
- The person who you are downloading from is using a bandwidth limiter. There
are two types of limiting: client based or using a third-party program.
So for particularly slow transfers (1 KiB/s or slower) from a certain user,
abusive upload limiting may be to blame.
- Clients with bandwidth limiting capability often 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. From version 0.760 DC++ also has
internal file transfer limiting capability. If enabled, DC++ shows the
upload limiting rate in the Connection coloumn of a hub's
user list. Other (older) clients may show this value in L: or B: part of the
- 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. This type of application never enforce a download
speed:upload speed ratio, it may be more prone to abuse.
- 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 find more sources for your download, right-click it from the Download Queue or from the Transfers area and select the Search for
alternates command. A corresponding Search window will
open, the "Slots" column of the result list of which can be leveraged to
find users with available bandwidth.
More sources for queued files can be discovered and automatically added if
you enable Automatically Match Queue for Search Hits in
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
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
Slow downloads within DC++ may be caused by the following:
- Bandwidth limiting is enabled for downloads. Make sure the
limiter is disabled or set to a high enough value.
- 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.
- 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 also
common at Universities and at the workplace, and is the topic
of another FAQ.
- 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.
- 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).
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.
- The "QoS Packet Scheduler" is enabled
in your Windows so you are not able to use some reserved bandwidth for
download. Follow this guide to disable QoS in Windows
Vista, 7 or 8. Some routers also have QoS capabilities, but it shouldn't be
enabled by default. Please consult your router's manual for more
- 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 in
Windows 7 and 8.x and in Windows Vista. If you're
running Windows 10 Anniversary Update or later you can try this
tool to fix network settings and more.