Optimizing the Transmission Bittorrent Client for Speed

This guide shows how to speed up downloads in Transmission.  All bittorrent programs need to have their incoming and outgoing communications flow freely in order to achieve the highest download speeds and that is essentially what this guide is about.

This guide was put together using information given by the developers of bittorrent programs at their forums, guides and FAQs.  There are no secret tricks, just the real basics of proper set up of a bittorrent program.  Following these simple steps should result in increased download speed.

These are the basic principles of optimizing a bittorrent client, like Transmisssion, for speed: 

• Choose a proper port to avoid ISP blocks and conflicts with other programs
• Forward that port through any software firewall and router to allow incoming connections
• Adjust internal settings based upon upload capacity of the internet connection to allow room for outgoing communications and to distribute upload efficiently. 

There are some programs that claim to optimize speed in Transmission.  Such programs are a scam and generally contain adware or spyware.  I have seen it said, by the developers of all bittorrent programs, that nothing will increase your download speed in a bittorrent client more than the basic steps set forth herein.

 Note When viewing this guide in Internet Explorer the Mac command key symbol appears as a box.  I do not know why yet.
This guide is now for Transmission 1.33, thanks to the anonymous poster below who provided the screen shots

Choosing A Proper Port

To avoid messing up a network connection that is already cleared, first check and see if your communications are blocked or are already clear.

Click to Test Your Port  Success-just go to Adjusting Internal Settings.   Error- follow all steps.

This setting in Transmission is at Preferences (⌘ + ,) or (Ctrl+,)>Network -"Network: Peer listening port":

If you failed the port test above, then you should first set your port to a proper one.  The most important choice here is to avoid using a port within the 6881-6999 range.  This was the range originally used by bittorrent programs and is often blocked by Internet Service Providers (ISPs).  (If your port was in this range, change and re-test). The safest choice is a port in the 49152-65534 range as this will avoid ISP blocks and possible conflicts with other applications.
Azureus-Wiki:  Port is Blacklisted

Forwarding The Port

Introduction
A router will block incoming communications unless an exception is made.  All software firewalls will block incoming communications and most will also block outgoing communications, unless an exception is made.  If you are "firewalled", then other people will not be able to initiate connections with you (see Why Is Being Firewalled Bad).
As there are many firewalls and routers, this guide can not give explanations as to each.  However, there are guides available, on the internet for most firewalls and routers and this guide will link you to them.

Software Firewall - The permission should be set to allow TCP and UDP in both directions.  Generally, you will have a choice to set permission for  the Transmission port or for the Transmission program.  Setting permission for the port is the safer choice.  You can check these options for guides:

• The help file of your software firewall is the best place to look
•  The µTorrent forum  has some guides posted
•  PortForward.com Firewall Guides also has some guides. (see Note)

Router - There are two choices here.  The easier way is to use UPnP (NAT-PMP in Mac).  However, this has a possible security issue.  Using UPnP, or NAT-PMP, allows any program to create a port mapping through the router without consent of the owner.  The other choice is to manually forward the port through the router.  This does not have that security issue, but involves going through several steps to accomplish.  Using the guides linked herein, this should not be that difficult and is the preferred method.

UPnP (NAT-PMP in Apple) - The Easy Way -  Enable UPnP (NAT-PMP for Apple) in Transmission and router.
In Transmission this setting is at Preferences (⌘ + ,) or (Ctrl+,)>Network "Automatically Map Port"

Manual Forwarding-The Preferred Way

1. UPnP (NAT-PMP) must be disabled in Transmission (see Image above). 
2. Use the Static IP Guide.
3. Set permission for Transmission port.  This should be set to allow both TCP and UDP communications.
   You can check these options for guides: 
   

• The help file of your router is the best place to look
• Portforward.com Router Index  has guides for most routers  See Note.

Click Here to Re-Test Port    Success-Proceed to next step.   Error- re-do steps or seek help in Forums.

Note:  Portforward.com does not have guides specific to Transmission.  Use the guides for Azureus/uTorrent and the screen shots from this guide.

Adjusting Internal Settings

Introduction
The most important setting here is to cap upload in Transmission to 80% of your overall upload capacity as there needs to be room for outgoing communications or else download speeds will suffer.  Other adjustments are made to distribute your upload so that you receive back the most download from other peers.

Speed Test: Speedtest.net
First the upload capacity of your internet connection must be determined by taking an online speed test. You should stop all internet activity, including torrents, before taking the test and the test should be taken a few times to obtain a reliable average. Speedtest.net has test locations worldwide and will highlight the one closest to you. Note that the result of Speedtest.net is in kilobits (kb) and bittorrent clients show speeds in kilobytes (kB). This is important as 8kb = 1kB. See Azureus-Wiki: Data Units
Note:  Before taking the speed test, press Settings in the upper left of the speedtest.net page and make certain the Speed Measurement is set to either kilobits or kilobytes.  This will help in inputing into the caculator below.

Calculator:  Azureus Upload Settings Calculator
Once you have an average upload speed for your connection go to the online Azureus Upload Settings Calculator. Although designed for Azureus, this calculator will work for all bittorrent clients. Enter your average upload speed in the appropriate box and the calculator will automatically give the proper figures to adjust various options in your client.

Input Results Into Transmission - Screen shots of locations in Transmission of settings to be adjusted

Preferences (⌘ + ,) or (Ctrl+,)>Bandwidth

The "Speed Limit Mode" is a scheduler and should not be enabled at this time.  If you are with and ISP that limits bandwidth usage at certain times of day, this would be useful.

Preferences (⌘ + ,) or (Ctrl+,)>Peers

The three options below the connections options should be enabled.  Peer Exchange (PEX) allows Transmission to seek seeds/peers outside of the tracker.  This will obviously help torrent health and speeds.  Transmission does not have DHT (Distributed Hash Table) capability at this time.  DHT, like PEX seeks additional seeds/peers outside of the tracker.  In my readings at their forum, it appears that there recently has been some work on this and it may be included in the future.  However, it is not one of their priorities.
The "Prefer Encrypted Peers" option means that Transmission will accept all seeds/peers, but will first attempt to contact via an encrypted connection.  Clients like Vuze/uTorrent will switch to encrypted automatically upon such contact.
The "Prevent known bad peers from connecting" option utilizes a blocklist of known anti-P2P IPs, to prevent them from connecting and possibly interfering with transfers.  I do not have information on setting up the list as of yet.

Preferences (⌘ + ,) or (Ctrl+,)>Transfers>Management

Transmission does not have the "Max Active Torrents" setting, enter the number in the Seeding maximum above.

Good Torrents

The above settings should work well most of the time.  Downloads of individual torrents depends on other factors.  See Good Torrents

Related Articles

• Searching for Torrents Popular and unique torrent search sites, with comments.
• Finding Legal (and Free) Torrents sites that offer only legally downloadable and distributable content.

Gizmo's Best Ever Freeware Forums

If you still have issues after using this guide and would like some assistance, please post in Networking & Internet section of our forums.  The comment section here is not well set up for ongoing discussions and the forums would be a better place to post as there will be a seperate thread for your discussion and keeping track of our discussion will be much easier.

Those who wish to post a thanks may post here or in the forums.  I always appreciate hearing from those who this helped and I do read the posts regularly.  I used to respond to each thanks, but realized it was clogging up the comments section.  I thank all those who have posted their appreciation and all those who will.

If you have a suggestion or correction for the guide, you may post here or in the forums.

Older posts on issues that were made here have been deleted as they were clogging up the comments section