Ravi Blogs about IT Topics

First off, a little background… Please note that this discussion is about Wesleyan’s network and Woodframe houses are NOT part of this network. We will be using the term Bandwidth a lot. This simply refers to the amount of data that can be transmitted in one second. For example, the typical broadband access from homes have a bandwidth of 6-10 Mb (Million Bits per second), wireless connections can support up to 56 Mbps and wired connections have 10-100 Mb bandwidth.

Wesleyan has an extensive internal network, both wired and wireless and typically 4500 devices use this network. Most wired connections are capable of supporting 100 Mb transmission; however, the wireless connections speeds vary depending on the quality of the connection. In addition, several wireless computers connect through a single wireless access point, which will affect how fast each connected computer can communicate.

Anytime your computer needs to access the internet, that traffic is routed through several network devices before exiting out from our network on to the Connecticut Education Network (CEN) who is our internet service provider. We have purchased 70 Mb bandwidth from CEN and continue to increase the bandwidth based on need and the cost. We expect to increase this in the Fall, but it is too early to tell by how much.

Since we have only 70 Mb available for everyone to connect to the network, we need to be careful about how to manage the connections so that everyone gets their fair share of the network. The art of managing the available bandwidth so that everyone gets a fair share of the network is called Bandwidth Shaping or Packet Shaping.

Our network is split into several separate categories – student, public labs and classrooms, wireless, faculty and staff, and servers. Then we allocate the 70 Mb bandwidth amongst these groups in various ways. I cannot go into the exact details of how it is allocated here. I can tell you that we do this by taking into consideration a whole lot of things. For example, sometime after 5 PM, the student network gets a larger portion of the bandwidth than the others, because most faculty and staff are not here to use the network. And, critical services such as the web servers and mail servers are allocated bandwidth that are never re-allocated to other services.

The packet shaping device also provides the ability to control the bandwidth at very granular level that goes beyond the categories listed. For example, we can specify that filesharing from the student network to the internet should be allocated a very small bandwidth, but web connection to the network should have a much larger bandwidth. We tweak all these based on usage patterns.

The packet shaping device also gets automatic updates from the vendor often. So, for example, if there is a new program that has been made available on the internet that affects the network performance adversely, an automatic update will be sent to the device to instruct that this be moved to a default partition that typically has a very small bandwidth. This is very nice because the vendor is doing all the work, but we are still informed.

One such update mistakenly allocated a very small bandwidth to the YouTube video streaming sometime in February. Many of you noticed this and complained and we looked around, found the problem and fixed it. Similarly, we heard that the same thing was happening on the wireless side. We immediately located the problem on the wireless network configuration (a different issue at this time) and fixed it.

We monitor these network devices to detect problems and correct them asap. Here are three images that show the internet usage. The green line shows the amount of traffic that is coming into our network. If you are watching a youtube video, the traffic is coming in to our network and is captured by the green line. You will notice that it is maxing around 80 M. We have temporarily increased it from 70 M for a couple of days. The blue line is the amount of traffic going out of Wesleyan. Traffic from all outsiders coming to our website or the email that our mail server sends to outside hosts are all captured here. This is for the past 24 hours. You will see that the traffic starts to go down around 2 AM when the students begin to retire for the day!!! Then you see the activity picking up again around 8 AM when faculty and staff begin coming to work…

This is the pattern for the past week. The pattern repeats itself.When we look at it more closely, we see that Saturday and Sunday morning activities begin later than 8 AM.

This is for the past year. As you can see, May-Aug, the usage is extremely low because the students are not here. This sort of gives us some idea for usage by the rest of the community and helps us shape the bandwidth accordingly.

As you can imagine, the network is VERY complicated and it is extremely hard to explain all the details on this topic and do it in a way that does not compromise our security. Hopefully this provides a good general idea about how we manage our network bandwidth.