6.3. A combined approach

In order to work out this location information for Hamilton Building, an online database system was constructed. A combined approach was taken, allowing both the physical and logical location to be determined using the same application.

Where possible, this information was to be gathered by the end users of the network, so it was important that any such system be simple and easy to use. To achieve this, a web interface to the database was developed. The interface was designed such that, in general, the user need only enter the number of the network point to which his computer is attached. The rest of the information required to populate the database was, as far as possible, gathered automatically.

The database running this application keeps two pieces of information. It stores a correlation between a switch port and the network point number (the logical location) and the user-entered coordinates of the network point as represented on a floor plan of the building (the physical location). These tables were populated with as much information as was previously known about the network in order to minimise the amount of information that would have to be collected from the end users.

Fortunately, the point numbering system in Hamilton Building makes it easy to correlate a network point with as specific room in the building. The network point number is divided into two separate parts, for example 37/1. The first part (37) uniquely identifies the room that the point is in and the second part (1) identifies a particular port within that room. The room number on the network point does not, however, correspond to the room number on peoples' doors. The relationship between these two numbers is known from the building plans and the database was pre-populated with a relationship between the two. The location of each room on the floor plan was also established and entered into the database. These two bits of information allow the system to make an accurate determination of the physical location of a network point.

When this web application is accessed from any computer in the building, the system first uses SNMP to locate which interface on which switch stack the remote computer is connected. This information is then looked up in the database to determine if there is already a correlation between this interface and an existing network point. If no such relationship is found, the user is prompted to enter the number of the network point to which their computer is attached. This point number is then recorded in the database against the interface number from the switch stack.

Once this information is known, the user is presented with a web page detailing the network point number, the room number and a description of the purpose of the room in which their computer is located. A subsection of the building's floor plan that pinpoints the position of the network point is also displayed. If no location is currently known for the network point, this subsection simply shows the room in which the network point is thought to be located. The user is then asked to more accurately position the point on the plan using their mouse. Any updates the user makes are saved back into the database. Figure 6-1 shows an example page from this system.

Figure 6-1. Location of a network point