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WAN bandwidth management frequently asked questions

WAN bandwidth management is probably the most time-consuming aspect of a network engineer's job and is a common question on the ITKE forums. Here are the most common questions and the answers for managing WAN bandwidth.

Wide area network (WAN) bandwidth management is without a doubt near the top of most network engineers' responsibilities and as such is frequently a hot topic on TechTarget's IT Knowledge Exchange (ITKE). The most common questions include how to determine how much bandwidth is needed for a particular application, how to block unwanted applications from taking up enterprise WAN bandwidth, and how to determine which applications are using the WAN resources. We have compiled some of the more common questions, with the best answers for each.

Which uses the most bandwidth: digital voice, document imaging, compressed video, or full-motion video?

Answer: A lot of variables go into determining which applications and services consume the most WAN bandwidth on an enterprise network. Not only does each service have its own basic bandwidth requirements, the different audio and video codecs used by vendors can vary significantly. On top of that, the amount of bandwidth a given application uses is going to be affected by how many users are actually utilizing the service. Using the available network tools to divide out network traffic by application is the best way to determine what is consuming the most bandwidth on your enterprise network.

⇒ For more information, learn how to calculate network bandwidth in this tip from industry expert Ken Milberg, or check out our guide on WAN bandwidth optimization tools.

What is the best approach to take to block file sharing applications, such as BitTorrent, from abusing the enterprise network?

Answer: The BitTorrent protocol usually uses TCP ports 6881-6999 but is designed to operate on any number of ports, and because of its peer-to-peer nature, it cannot be affected by blocking a single destination IP address. A number of enterprise-class firewalls perform deep packet inspection, giving them the ability to detect and in turn block BitTorrent traffic regardless of which ports were used, so first check with your firewall vendor to see whether this is an option. If the firewall cannot filter this traffic, the next approach would be to deploy a traffic shaper. Traffic shapers can analyze network traffic at the application layer and could help identify and block unwanted peer-to-peer traffic.

Alternatively, the problem of peer-to-peer network usage could be handled at the clients themselves. Depending on the corporate environment, PC administrators could take several different approaches to blocking the file sharing applications, either by locking out users from installing non-approved applications on corporate machines through group policy or by identifying these applications through antivirus/anti-spyware agents on the machines.

⇒ Read's Network user management guide to learn more.

We are running an ISP and would like to manage our bandwidth and our customer requirements by providing different ratios of bandwidth for the uplink and downlink. Is there any product that allows us to manage WAN bandwidth and provide real-time graphs for customers to show which public IP addresses are utilizing more bandwidth in their assigned allotment?

Answer: A number of products are available, both commercial and open source, to monitor bandwidth usage. Open source products recommended by ITKE contributors include CACTI and Freeside. The other option, suggested by Barrie Sosinsky in his tip on bandwidth management solutions, is to purchase a product to help you control network traffic. Among the many products in this area are Allot NetEnforcer, Packeteer Packetshaper, Checkpoint Floodgate-1, Solaris Bandwidth Manager, among others.

⇒ Additional recommendations can be found with the bandwidth allocation tag on ITKE, and in this FAQ guide to bandwidth management services on

We have about 40 technical resource agents, providing 24/7 offshore support for a client. We are also using 10 IP phones for client communication. What type of WAN link and bandwidth are required for this kind of environment?

Answer: A typical VoIP line using a full quality telephone call will use up to 90 Kbps; but, at the cost of some loss of call quality, the line can be turned down to either 60 Kbps or 30 Kbps, if bandwidth is an issue. This additional bandwidth is on top of any Web browsing or other WAN traffic. For the example of 10 VoIP lines, at least a 1 Mbit WAN link would be recommended, and ramping up for any additional applications as needed. Quality of service (QoS) policies should also be put in place, prioritizing the voice traffic ahead of your data traffic. VoIP traffic is particularly sensitive to latency and needs to get pushed ahead of other data traffic moving across the WAN.

⇒ Take this crash course on VoIP bandwidth fundamentals from to learn more.

I have a 1 Gb local bandwidth with 10 Mb international bandwidth in my data center. My problem is I don't know how to share the international WAN bandwidth equally among my clients. I don't know whether there are devices I need to use or whether there is any way I could just control the international bandwidth with our Cisco 3845 routers and 2960 switch. The Internet link I have cannot be separated. How can I define local and international bandwidth?

Answer: Cisco should have a QoS module you can use to balance throughput across the line based on the destination IP address. You'll need to find out from your provider how it defines "international." There are also networking vendors, such as Quova, which are building geo-location databases based on the IP address that may be able to segregate the traffic to fit your needs. Their databases have been licensed and built into a number of network products.

Do you have a question about WAN bandwidth that you didn't find here? Check out the answers under the WAN bandwidth tag on the ITKE or send your questions to

This was last published in July 2010

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