ResNet
Bandwidth Usage:
How does sharing audio and video files impact ResNet?
As students continue to use the network for both academic and recreational computing, ITSS staff and Residence Hall students must look at new ways to manage this limited resource. Currently, students are experiencing periods of slow network performance in the residence halls because of the excessive bandwidth use of file-sharing programs. This article will explain:
- What is UMDNet's bandwidth?
- What is excessive bandwidth and who's using it?
- Why don't we buy more bandwidth?
- What are the legal and ethical issues?
- What is ITSS doing to improve performance?
- What can residents do to improve performance?
What is UMDNet's bandwidth?
It's important to understand the scale of the parts of the network to get a hold on bandwidth issues. As shown in the diagram below, desktop connections to the network run at a maximum of 10 Mbps (megabits per second) (see note 1). The network device you attach to connects to the network backbone at 100 Mbps (switch).
The main backbone runs at 1000 Mbps and is seldom busy. That's all local to the campus though, and many people want to get to things that are off campus, such as the Internet.
Our Internet link runs at about 35 Mbps, plus some "burst" bandwidth we can use that is on loan to UMD. Note that this is at least twice as slow as the slowest part of our backbone. This bandwidth is subdivided equally into two "pipes": a 25 Mbps pipe is set aside for campus use (including all offices, computer labs, and the campus servers), and another 25 Mbps pipe is set aside for ResNet use. This is done even though there are only about 2,500 students connected on ResNet, while there are over 4,400 faculty, staff and lab computers connected on the campus side.
The results? On any given day, the inbound and outbound traffic on the ResNet pipe is maxed out at 23-25Mbps (and users are seeing slow performance), while the campus pipe sits around 10-15Mbps for both inbound and outbound traffic (and users see normal performance). And remember - the campus pipe includes all of the campus-wide servers for email, the web and the student computer labs!
What's happening on the ResNet pipe? Students are using large amounts of bandwidth for file-sharing programs such as KaZaa and Morpheus, filling the ResNet pipe and creating network problems for all ResNet users.
What is "excessive bandwidth" and who's using it?
Normal Internet and email use does not consume excessive bandwidth. However, activities such as video or audio streaming on-line and downloading movies or MP3's do consume large amounts of bandwidth. For comparison, here are the relative sizes of several media files (see note 2):
| Media file | Size (in kb) |
|---|---|
| Microsoft Word file with nstructions on how to access email accounts | 19 |
| Image of the terrorist attack on the World Trade Center | 25 |
| Photo from the September 2002 issue of Time Magazine | 81 |
| MP3 version of Metallica's hit song "Nothing Else Matters" | 5,700 |
| Episode of "The Simpsons" where Lisa becomes a vegetarian | 25,000 |
| Version of the video game "Tomb Raider" | 203,000 |
| Compressed version of "Crouching Tiger, Hidden Dragon" | 800,000 |
Our PacketShaper and our monitoring software allow us to determine who is using large amounts of bandwidth and what type of files they are transferring. Please note that we do not monitor the contents of the files - only the size.
On any given day, the largest source of both inbound and outbound traffic in the residence halls is Kazaa: [NOTE: Since replaced by Morpheus and BitTorrent 9.02.05]
| Residence Hall Traffic - Thursday, Oct 31 | |
|---|---|
| Inbound traffic | Kazaa - 48% |
| Outbound traffic | Kazaa - 56% |
During that same period, three of the top 15 bandwidth users - including all of the email, web, lab, file, and software servers that ITSS maintains - were personal computers for students in the residence halls:
| Top bandwidth users on campus - Thursday, Oct 31 | ||
|---|---|---|
| Total bytes | User | |
| 208,017,081,289 | Campus authentication server | |
| 79,342,381,238 | Novell backup server | |
| 55,736,150,578 | Residence hall student's personal computer | |
| 39,961,968,043 | Campus web server | |
| 35,457,829,945 | Department server | |
| 32,681,291,709 | SunRay server | |
| 30,588,797,043 | Campus web server | |
| 30,439,192,030 | Department server | |
| 29,057,596,622 | Residence hall student's personal computer | |
| 25,582,602,961 | Campus email server | |
| 24,793,877,109 | Student lab server | |
| 23,938,029,903 | Residence hall student's personal computer | |
| 22,047,978,934 | Department server | |
| 21,931,748,226 | Department server | |
| 21,653,855,539 | Campus email server | |
Why don't we buy more bandwidth?
If the pipe is full, so to speak, why not just buy more bandwidth? There are a number of reasons not to do this.
First, bandwidth is expensive. Increasing our bandwidth costs will mean increasing fees for everyone on campus.
Second, we know based on experience that it won't work just to double our bandwidth. It won't work to triple our bandwidth (at triple the cost). Based on studies, we'd likely need to increase the bandwidth by a factor of ten or more. And based on our analysis of the traffic that is filling the ResNet pipe, we'd be buying that bandwidth to provide more access to file-sharing programs, not to meet academic needs.
Third, the campus pipe meets the needs of over 4,400 users doing (mainly) academic or work-related computing. Shouldn't the 2,500 users of the ResNet pipe be able to work within the same limits?
What are the legal and ethical issues?
In addition to the network performance problems caused by the file-sharing programs, there are legal and ethical issues concerning copyright protection.
The University is responsible for obeying the Digital Millenium Copyright Act, and there are clear procedures in place for ITSS to help in this. Complaints under this act come primarily from the recording and movie industries, who contact us when their copyrighted material is being distributed illegally. Complaints are reviewed by security experts and attorneys on the Twin Cities campus to make sure they follow the format specified by law. Then they are sent to ITSS for action. Our procedures are that the violation is verified, the port is turned off, and the user is notified. The port remains off until the user can demonstrate that the offending material has been removed.
Additionally, the leaders of six major higher-education organizations are asking the presidents of all American colleges to take steps to stop illegal distribution of copyrighted materials, such as songs and motion pictures, through college computer networks. See Higher-Educations Organizations Urge a Crackdown on Illegal File Sharing for details.
What is ITSS doing to improve performance?
Infrastructure improvements: ITSS made improvements to the UMD backbone, the Residence Hall areas, and the Internet link during the summer. In the residence halls, most remaining hubs were replaced with newer, faster switch technology, and connections to several buildings were increased to 100Mbps. Additionally, ITSS upgraded our Packeteer and PacketShaper software to the latest code and configuration. This device is crucial to maintaining reasonable sharing of bandwidth.
Bandwidth monitoring: Currently, we monitor bandwidth usage to determine which ports are using excessive bandwidth. Usually, these are computers that have been set up to be KaZaa or Morpheus servers. These ports are turned off, and the students are notified that they need to contact ITSS before the port will be turned on again.
Other options: We are currently looking at several other options. One is to limit all ResNet ports to a daily amount of network traffic - once a person exceeds that amount, their port is automatically turned off. A variation of that is to provide "premium" service to all ports that are using reasonable amounts of bandwidth, but ports that use excessive bandwidth would be dropped to a lower level of service.
What can residents do to improve performance?
Don't be a server: Most file sharing programs (KaZaa, Morpheus, etc.) install themselves as a server on your computer by default. Turn off server mode and improve performance for both your computer and the network. This will also prevent you from getting your port turned off when the recording industry sends a "Cease and desist" order to the University's legal department regarding the copyrighted files that are being served from your computer (we get these weekly). For details on how to do turn off server mode, see Turning server mode off.
Use the default ports for your programs: Changing ports may temporarily get you faster download speed, but it will also get you a call from our network administrator explaining why we've turned your port off.
Limit your downloading: Download what is most important to you, giving priority to your work as a student. Make sure you do NOT download music, videos, or other work that is copyrighted. Avoid downloading indiscriminately or excessively. If everyone did this, the network would be much faster.
Note 1: The speed of the connection from your desktop to the network is limited to 10Mbps by the wiring and the network configuration, NOT the speed of your Ethernet adapter. Thus, while most computers now have 10/100Mbps Ethernet adapters, your computer will only run at 10Mbps with the current network configuration. For the best performance on UMDNet, ITSS recommends that all Ethernet adapters be manually set to run at "10Mb/half-duplex". For details on how to do this, see: Connect and register.
Note 2: Data from North Central College