What Affects Upload and Download Speeds

As a video platform, we move tons of data to and from our clients. Even with the support of a content delivery network and an accelerated uploader, there are times when people don’t achieve the speed they are expecting with an upload or a download. We’ve put together this guide to help you understand some of the factors that affect connection speeds.

To start looking at the different factors, we’ll begin with your computer and move out from there towards the servers at the other end of your upload or download.

As we will see below, ISP policies can have a big bearing on your transfer speeds. Debates about the Open Internet, Net Neutrality, and Fast Lanes aren’t just academic. They have a direct bearing on the performance of the different sites you visit and web applications you use.

Your Computer

Sometimes your own computer can be a bottleneck. If you are using an old computer, you may have an old WiFi radio, which could be limiting your connection speed.

For example, your old Windows XP computer may be rocking an 802.11b network card, in which case the theoretical maximum transfer rate will be 10 Mbps, and the practical speed will be much less. It’s not worth paying for a 50 Mbps connection if that’s going to be the bottleneck.

Even if your hardware isn’t to blame, misconfigured network settings can slow things down, as can too many open browser tabs and background processes like Dropbox. You may want to check if you have programs like a bittorrent client chewing up bandwidth.

Your Wireless Network

Many of us use WiFi networks in our homes and businesses without a second thought. Sometimes, they can be the cause of slow upload and download speeds.

Factors at play include the distance from your access point, physical interruptions, signal interference from microwaves and cordless phones, or too many neighbors competing for the same swath of unlicensed spectrum (very common in apartment buildings).

One of the most frustrating aspects of using a WiFi networks is signal interference. Your connection can be humming along and then drop out for what appears to be an inexplicable reason. If it drops out for long enough, an upload or download can fail. Devices that are connecting via the 2.4 Ghz band, which is used by 802.11 b/g networks, are more susceptible to radio interference and these sudden drop-offs.

Connections that use the 5.0 Ghz range, 802.11 a/n/ac, tend to have fewer of these jarring drop-outs when someone turns of the microwave or talks on their old cordless phone, but they have their own challenges. The higher the frequency, the harder it is for a signal to pass through materials, so these connections tend to get blocked more easily by physical obstructions.

One way to test whether your Wi-Fi network is potentially the cause of a connection problem is to connect your computer to a wired connection. I just switched to a 50 Mbps Internet connection in my home, but when I tested it using Speedtest.Net, the maximum speed that I got in most rooms was 20 Mbps. Since I can transfer data at full speed when I connected directly to my router, I know that my wireless network is the bottleneck.

Perhaps changing the wireless channel, moving my access point to a more central location, or installing a network extender will help improve my connection speed. Failing that, it might be time to look for a better router. If you decide you need to go wired, you can do the obvious thing and run ethernet cable between your router and your computer, which is fine if your computer is near your router. Alternatively you can look at some of the power-line networking solutions that are available - not as convenient as wireless, but better than running exposed cables through hallways and way cheaper than running cables through the wall.. If your network isn’t meeting your expectations you can try some of these different solutions. Unfortunately, it may take a bit of trial and error to figure out what works best for you.

Your ISP's Network

Not surprisingly, your choice of connection technology, and your ISP's network will have a big impact on your connection speed. I’ll break this down into DSL, cable, and fiber, since each network type has its own issues. Then I’ll address the common factors that affect all of them.


A phone network has a dedicated wire that runs from your house to a remote terminal or the phone company’s central office. The shorter the distance between your house and the point where the phone company aggregates traffic, the faster your potential connection will be.

In recent years, telcos have been trying to shrink the distance between people’s homes and these connection points by pushing fiber optic connections closer to people’s homes. The benefit is that these short connections support more advanced variants of DSL that offer higher potential connection speeds and can also be used to offer television service.

The reason I bring up the distance point is that if you live in a rural location, chances are you won’t see the same speeds as someone that lives in a city. In my case the difference is pretty substantial. I get a 50 Mbps connection in my house, and 1 Mbps at my friend's cottage. Likewise, some locations in cities may still have relatively slow speeds due to their distance from the central office or remote terminal.


The architecture of cable networks is different. Instead of having a direct connection to your cable company’s hub, there is one very fast connection and each home in your neighborhood essentially taps into it. Think of it like a bunch of streets feeding into a major artery.

In this sense, cable is a shared network. The more people sharing the connection and the more intensively they are using it at the same time, the slower the effective speeds will be for each user.

Cable companies have been doing lots of work to reduce the number of people that share the same connection. By splitting the nodes into smaller and smaller groups of households, they are better able to control the speeds that their customers get.

The big benefit of cable’s architecture is that it’s much less distance sensitive. So if you are living in a rural area and have the choice between cable and DSL, it’s fairly likely that you’ll be able to get faster speeds with cable.


Fiber Internet connections like Verizon’s FiOS service and Google Fiber represent the best option for Internet access. It’s like having a dedicated roadway between your house and your service provider’s network.

Fiber uses an optical connection that doesn’t suffer from the ups and downs of radio frequency interference. It supports much higher speeds, it doesn’t suffer from distance limitations, and it’s not directly shared with others in your neighborhood.

If you have the option of buying a fiber connection and the price is reasonable, take it. Unfortunately, fiber Internet access isn't broadly available to consumers and small business customers due to the high cost of replacing existing networks with fiber.

ISP Network Bottlenecks

Outside of the access technology that is used, there are several other areas within the ISP network that can cause slow upload and download speeds.


A major factor here is how much capacity your network provider has provisioned per subscriber. As an easy to understand example, imagine an ISP with 100 customers, each of which has a 25 Mbps Internet connection.

At some point, this service provider connects to the Internet (there are some major simplifications here). All of the traffic for the 100 customers is aggregated and sent in and out of the network. The service provider doesn’t provision capacity with the assumption that all customers will be uploading and downloading at their peak speed at the the same time (100 customers x 25 Mbps = 2500 Mbps). Instead, it over-subscribes this bandwidth. Perhaps its usage models say that it only needs 1/10 of this bandwidth, or a 250 Mbps connection to support all of its users and give them their desired throughput.

Different ISPs are going to have different assumptions around contention. Perhaps that low cost DSL reseller with unlimited access is cutting costs by increasing the contention ratio or provisioning less capacity per customer. At 2:00 in the morning, this may be fine, but at peak times the effective throughput may not be satisfactory as people fight for capacity.

Network capacity

Network providers need to continually add capacity as usage patterns change. As more people use bandwidth intensive services like Netflix during peak times, service providers must add capacity or use other alternatives like caching content locally or partnering with content delivery networks.

ISPs can fall behind on adding capacity and this can lead to degraded performance. Sometimes this is a case of inadequate preparation, and other times it’s a business decision to manage spending on new capacity or force someone else to pay for it.

As a real-world example, Comcast customers have complained about poor performance. Netflix and Comcast pointed fingers back and forth about whose fault it was, but it was really a protracted negotiation about who should pay for the increased capacity required to support growing Netflix usage.

In the end, Netflix signed a commercial interconnection agreement with Comcast. Essentially, it paid for the right to connect directly into Comcast’s network. Since Netflix signed the interconnection agreement with Comcast, the speed of its customer connections has improved dramatically.

The bottom line here is that ISP business decisions affect the experience when using different services. This is most noticeable with services like video applications where large files must be delivered in real-time.

Traffic Management

Some ISPs throttle, or intentionally slow down, certain kinds of traffic like BitTorrent or other peer to peer applications. If you are a regular user of these applications, try shutting them down to see if this improves your connection speed.

Likewise, some ISPs may actually slow down your transfer rates once you have passed a certain usage threshold. If you suspect this is the case, you might want to get in touch with your ISP to see what the limits are.

Troubleshooting Your ISP

The long and short of it is that not all ISPs are created equal when it comes to things like capacity, peering, interconnection agreements, caching and traffic management. The actual throughput you get may not meet your needs during prime usage periods.

If you have run speed tests on your connection while directly connected to the modem and you aren’t getting the upload and download speeds you expect, you should contact them to see if they can help you out.

If you don’t have much success troubleshooting with your ISP, you may want to look for a new one. I’ve found that DSL works better in some locations and cable works better in others. It can be helpful to compare your ISP with others in your region using benchmarks like Ookla Netindex or Netflix’s data.

Distance and Congestion

Upload and download speed is also affected by the distance between your computer and the server that is either sending or receiving data.

In general, the greater the distance the slower the speed of the data transfer. When connecting over larger geographic distances, traffic makes more hops between different connections, and each hop increases latency.

Your data can take a multitude of different routes between your computer and a remote server. Sometimes transfers simply get caught up in congestion along the way. Further, traffic from different ISPs (or even different locations with the same ISP) will be routed differently. As a result, users of one ISP may fast upload and download speeds from a site, while users of another ISP may see a temporary glitch in performance.

There isn’t much you can do to reduce the distance your data travels or avoid congestion, but there are plenty of things that service providers can do to help improve delivery. Probably the most important one is to use a content delivery network. Instead of serving all media from one location, popular content will be cached in different points of presence around the world. When a person requests a file, it is automatically served from the location that will provide the best performance (barring some sort of congestion, this is usually the one closest to them).

We’ve been using a CDN to improve the ScreenLight video playback experience for several years.

We’ve taken a similar approach to handling the upload experience. Rather than sending uploads to one central location, we transparently send files to the location nearest the person that’s uploading the file. Again, on average, the shorter the distance, the faster and more reliable the upload.


The protocol that is used for uploading or downloading a file can also have an impact on the speed of data transfer. HTTP and FTP use the TCP/IP protocol for sending and receiving data. The protocol is great for reliability. Unfortunately, it’s not the fastest way to transmit large files over long distances when using fast connections.

Transfer speeds can be accelerated over fast connections (at least 5 Mbps) by using the UDP protocol. File Catalyst does a good job of explaining why the UDP protocol is more efficient than TCP/IP for transferring files. Aspera, Signiant, and File Catalyst all offer accelerated file transfer solutions that are geared at companies that need to send vast amounts of data back and forth between different locations.

In order to take advantage of the potential speed of these services you need a fast connection. So for uploads, most residential and small business users won’t see much benefit unless they have a consistent uplink speed of at least 5Mbps.

Troubleshooting Tips

If you aren’t receiving the upload and donwload speeds that you are expecting with ScreenLight, or any other site, here is a recap of the troubleshooting tips above:

Check with your ISP to see what package you have subscribed to. Note the upload and download speeds. Most residential and small business packages have much faster download speeds.

Test your connection speed via Speedtest.net. If you usually use a wireless connection, you’ll want to test your speed when connected to your wireless network and when connected to a wired connection. This will help isolate whether the speed issue is with your ISP or with your wireless network. Note: when testing your wireless connection, try to do it when there aren’t other people using the network.

If you get your target speed when you are connected to the wired network, but not when you are connected wirelessly, you’ll want to work on improving the performance of your wireless network. Check the placement of the device, try changing the network channel, and make sure you have the latest drivers for your devices. If this troubleshooting doesn’t do the trick, you may want to look at adding a network extender or even upgrading to a new wireless router.

If you aren’t getting your target speed when connected to a wired connection, you’ll need to give your ISP a call to see if there is anything that they can do to resolve the problem. It will be helpful if you can provide information on whether the problem happens when connecting to sites in general, or if the poor performance is limited to certain sites and applications.

If you experience problems with uploads or downloads to ScreenLight, but not with other sites, then it may be an issue with the route that your traffic is taking. Please contact us directly and we’ll work with you to resolve the issue.