The Network

From Waisman Brain Imaging Wiki

Possibly one of the most confusing things to newcomers at either lab is "the network". This is a broad term that encompasses dozens of server computers, miles of cable, and stacks of computer networking equipment.

When someone says that "the network is full!" they really mean that the file servers where all of the study data is stored are running out of disk space.

When someone says that "the network is slow!" they probably mean that there is a lot of computer activity in the lab right now, so that there is a lot of data being transferred between the file servers and various other computers in the lab. Since the physical lab computer network can only move a finite amount of data per second, the computers end up getting stuck waiting for their data to be transferred, and thus act unresponsive or slow.

When someone says that "the network is down!" they mean that from where they're sitting, the network appears to be broken. This might mean a lot of things:

• Perhaps the connection between the lab and the outside world is down. This happens a lot when DoIT (http://www.doit.wisc.edu/) is working on the UW campus network backbone (usually during the summer or on weekends).
• Perhaps some of the lab computer network hardware has stopped working. (This happens more during the summer since a lot of the hardware is in the ceiling over the kitchen where it gets very hot.) In this case, some people in the lab won't have access to the network, but others will.
• Perhaps the file server that they're getting their study data from has filled up or crashed. Everything else on the network still works, but it all seems broken to them, since the part that they're concerned about doesn't work.
• Perhaps the Windows-specific portion of the network is down. Things still work fine for the Macs and UNIX computers, but all of the Windows users are stuck. This is probably the most common network problem.
• Perhaps someone is running a huge network-stomping job, and the network is slowed down so badly that it just seems down.
• Or perhaps their computer is just having problems, and they're just blaming the network since something on the network seems to be breaking down all the time, so why not this time as well?

The Network includes all of the following and a lot more:

• Connections from Windows PCs to the lab network drives.
• Surfing the web from within the lab.
• Connecting laptops wirelessly via Wireless Wiscworld at Keck or the lab wireless access point at Brogden.
• Transferring files between the labs.

These are all inter-related, but not the exact same thing. So, when you hear someone say that "the network is down!", it might not mean that you can't get your work done, just that they can't get their work done.

The Network is also made up of these parts:

• File servers. These computers have huge hard disk arrays attached to them, so that they can store the data from many studies all at once. They all run UNIX. They are physically in the server rooms, and you'll likely never see them. But your computer will connect to them to get at your study's data.
• "Samba" servers. These computers translate UNIX network-speak into Windows network-speak. If they have problems, then the Windows PCs won't be able to connect to the file servers. But everything else still will.
• Windows "login" servers. When you log on to a lab Windows PC, you need to type in your account name and password. These are passed to the Windows login servers, which then give you permission to connect to the lab network drives. If your password is wrong or the Windows login servers are having problems, you won't be able to get to any of the lab computer resources.
• "Application" servers. These are computers just like the other ones in the lab general use rooms, except that they are very fast, have a lot of memory, and run Linux. They are shared by everyone, and are physically in the server rooms so that they're out of the way. You can't sit down in front of them and use them directly; you need to connect to them remotely using SSH.
• Network equipment. This includes the hardware needed to connect all of the servers and other computers together. The labs are fortunate in that they are set up with very good, very fast network equipment.