Overview of the Lab
Layout of the Room
The diagram below shows the ITL floorplan.
The lab is 40 feet deep and 29 feet wide. It contains 6 work areas where teams of students can experiment. Each work area consists of 4 computers and two racks of network equipment. Each work area is identified by a number as shown. There are two additional racks in the back of the room devoted to equipment and servers shared by the entire lab. There is a shelf circling the room just above the tops of the racks to hold the cabling that connects the equipment in the room.
The lab has an overhead projector suspended from the ceiling and a 10' x 8' projection screen at the front of the room. The racks have been located to leave sight lines clear from every student to the screen. There is a cabinet in a corner at the front of the room that contains a computer and dvd player, both connected to the overhead projector. This computer has a wireless keyboard and a wireless mouse to allow the instructor to manipulate it from a podium in front of the class.
Wiring Infrastructure
The diagram below shows some of the connections within work area 1.
The other work areas are similarly wired.
Two independent networks coexist in this lab. One, the public network, connects each computer in the lab to the campus network and thereby to all the network resources supported by the Computer Science Department (e.g. servers, printers) and by the campus, and also to the Internet. The connections to the public network are part of the CS Department subnet 130.157.166.0/24. The other network, the private network, connects each computer in the lab to the network hardware used for instruction in computer networking. The connections to the private network are part of the network 192.168.200.0/24. The private network is not connected to the campus network or to the Internet except that each computer has a connection to both. Some hardware is always connected to the private network (e.g. the computers, the terminal servers, the private network server) while others can be connected as needed (switches and routers located in the work areas).
Located throughout the lab above the cable shelf are 10 outlets each with three RJ45 jacks for a total of 30 connections to the public network. Every computer is connected to the public network through its network interface 0. The unused connections are made available for connecting laptop computers to the public network. There is one additional connection to the public network for the computer in the media cabinet. The physical connections between the computers and the public network jacks should be left in place. If it is necessary to disconnect a computer from the public network this can be done in software.
On one rack in each work area there is a patch panel to which the 3 remaining network interfaces on each computer are connected. The computers can be connected to each other and to other equipment by connecting patch cables to this patch panel. There are also connections on this patch panel to a central switch. This constitutes the connection to the private network. A short patch cable is left in place on the patch panel to connect network interface 1 of each computer to the private network. This patch cable can be removed if an experiment requires the use of all three extra network interfaces, but should generally be left in place. This connection to the private network allows each computer to access the services of the private network server as well as access to the console ports of all the network equipment.
This patch panel is also used for connections to the two serial ports on each computer. A computer's serial port can be connected to a console port on some piece of equipment of these connections (although usually access to the console ports will be made by telneting to the terminal server), or two serial ports can be connected to each other.
On one rack in each work area there is a terminal server. This terminal server is connected to the private network through ethernet, and to the console ports of each piece of network equipment (hubs, switches, routers) in the work area through serial cables. It is through the terminal servers that each computer gains access to the console ports of network equipment. Each terminal server also uses the private network to access the private network server from which it loads its operating system. When a terminal server loses its connection to the private network it can be reached directly through one of its serial ports so that it can be reconfigured. This is accomplished by connecting its port 1 to the jack on the patch panel that is connected to a serial port on one of the computers.
The diagram below shows other connections within work area 1. The other work areas are similarly wired.
On one rack in each work area there is a patch panel that connects that work area to the other work areas. These connections are available for experiments on a larger scale than can be accomplished within a work area, or to allow a piece of equipment available in only one work area to be used from another work area. Every work area has 2 ethernet connections to every other work area. One set of connections is colored gray and the other is colored yellow. There is no significance to the colors other than to allow the 2 sets of connections to be easily distinguished. The connections on each patch panel are labelled with the number of the rack to which the connection leads. On each rack the connection whose number is the same as its work area is not otherwise used, so these jacks are used for a connection to one of the shared racks in the back of the lab and are labelled with an asterisk (*).
Connections between a computer and another computer, between a computer and a piece of network equipment, or between two pieces of network equipment can be accomplished using patch cables to connect patch panels on the racks.
All cabling in the lab infrastructure is straight-through cabling. Any crossover connections that are needed must be made using patch cables. Cables were built using the T568A conventions.
Computers
There are 24 student computers in the lab, 4 in each work area.
Each is identified by its work area number (1 through 6) and a letter (A through D).
There is an additional, identical computer in the media cabinet in the corner of
the room. This computer is connected to the overhead data projector and is used
by the instructor for demonstrations.
Each computer has 4 network interfaces. Interface 0 is built into the motherboard. Interfaces 1, 2, and 3 are Network Interface Cards (NICs) installed in PCI slots. All 4 support speeds of 10 Mbs and 100 Mbs.
There is an additional computer in the lab whose sole function is as a server for use on the private network. This computer is supported by an uninterruptable power supply. It is left running, and on this server root access is restricted. The terminal servers load their operating systems from this server using TFTP. This server is also used to provide other network services to the computers in the lab when the campus network is either unavailable or inappropriate. These services include DHCP and Web Serving.
There is another computer in the lab whose sole function is as a server for use by students. The root password for this server is the same as the root password for "itl linux" on the work area computers. This computer is not left running. It has one network interface that can be connected and configured as students wish (i.e. to the private network, directly to a switch or router in a work area, etc.) Students using this server should make no assumptions about its configuration, as that may have been changed by other students. This server can be used for experimenting with DHCP, web serving, etc.
Network Equipment (Hubs, Switches, Routers)
Each work area has a variety of network equipment. A basic set of hubs, swiches,
and routers is the same in every work area so that standard experiments can be
performed in the same way at any work area. More
specialized and less generally used equipment may be present in one or another
work area but not necessarily in all of them. The basic set of equipment includes:
Power Issues
There are 2 separate 15-amp circuits available for each work area, one circuit for
each of the 2 racks.
(The circuit breakers are 20 amps, but the circuits are supposed to remain at or
below 15 amps.)
The shared racks in the back of the room must share a circuit
with work areas 3 and 4. There is an independent circuit for the media cabinet and
projector.
Some pieces of network equipment have their own power switches. These are generally powered off when not in use. A few pieces of equipment do not have power switches and are powered on as soon as they are plugged in. These pieces of equipment are plugged into uninterruptable power supplies. Each uninterruptable power supply has a master power switch.
It is important to avoid changing the way in which the equipment is plugged in. The total current drawn by all the equipment exceeds the 15 amp capacity of a single circuit and must be distributed among the circuits so that none of the circuits is overloaded. [Click here if you are interested in more details on the current drawn by the equipment and how it was measured.]