Why has my Internet connection slowed down?

Slow Internet access can be a right pain both at the workplace and at home. Nowadays, we demand fast access to websites and cloud services. Gone are the days of 9600 baud modems and in its place we have high speed links allowing instant access to information.

However, I often come across instances of people complaining that "the Internet is slow". Today it was my neighbor with one computer on their network, and last week it was a hospital network with thousands of connected systems. Here are some of the reasons why an Internet connection can slow down:

  • Local network is overloaded

Most people do not connect their computers directly to the Internet. Instead, there is a local area network (LAN) which everyone connects to. The LAN could be wired or wireless and it will have a connection to the Internet router. If the LAN is over loaded with something like backup traffic, then this will slow down Internet activity. Traffic to and from the Internet will have to pass the busy junction which is the overloaded LAN. You can get visibility as to what is happening on your network by considering one of the many network management tools which are available. Some people worry about the impact monitoring could have on the network. However over on the EtherGeek blog, Josh Stephens dispels this network myth and other taboos.   

  • Slow DNS responses

The domain name system (DNS) is still widely used as computers cannot connect to hostnames like www.computerworld.com. This host name must be converted to an IP address before a connection can be established. A slow response from a DNS server will cause delays. You should be aware of the DNS hierarchy on your network. If you change Internet service provider, make sure you also check how DNS is configured.

  • Unknown downloading

Most modern applications are constantly on the lookout for updates and upgrades from the Internet. These update processes can run in the background so may not be visible. Some updates are small but things like operating system service packs can be greater than 1GB in size. You should consider local software update servers if you have lots of clients on your network. Getting visibility of who is doing what on your network is crucial.  

  • Bandwidth vampires

I define a bandwidth vampire as someone who has gained unauthorized access to your network to download or upload data. In the case of a home user, it could be a neighbor getting access to an open wireless network. In the workplace, it can be something like users bringing their own devices to work and using them to gain access to the Internet. Cheap storage media devices now come with 2TB drives and include options like Bittorrent clients. Once connected to a network they can use up massive amounts of bandwidth on an Internet connection.

  • ISP throttling

Some internet service providers have implemented a policy where they will slow down an Internet connection if something like Bittorrent is detected. This is designed to frustrate people from downloading data via peer-to-peer networks. If you want to check for this type of activity on your network, I have further info in my checking if your Internet filter is working blog post.

  • The website or service being accessed has slowed down.

A common but obvious example of this is when tickets come out for some must-see game or show and everyone swamps the ticket selling website. Just when you are about to pay, the website slows down or crashes.  Over on platforms in the cloud, Frank Artale has an interesting post on how the data deluge is driving innovation.  Some sites and services are not coping with end users expectations that content has to appear immediately after posting. If you need to look at this further, there are end-user monitoring systems available for monitoring transaction times. A simple trace route (tracert in DOS) can also reveal the response time of each hop between you and the website in question.

  • Malware or scareware on end users computers

Malware or scareware software is becoming an increasing problem on computer networks. There are many attack vectors, from strangers calling the end user and asking them to click on links to user's access compromised websites. In a lot of cases the user is not aware that there is anything installed on their system but they may notice that Internet access is slower. This can be down to the rogue software hijacking search strings and displaying useless ads. A zombie host like this your network should be taken offline and cleaned. However, if the system is used to access any sensitive data I would recommend a complete reinstall.

  • Bad connection

Problems with your physical Internet connection are one of the least common causes of slow response times. You will not have much visibility into what happens after your Internet router. If you suspect a problem, your ISP can remotely run tests on your line.


Darragh Delaney is head of technical services at NetFort Technologies.  As Director of Technical Services and Customer Support, he interacts on a daily basis with NetFort customers and is responsible for the delivery of a high quality technical and customer support service.

Copyright © 2011 IDG Communications, Inc.

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