The Topology Generator

The Topology Generator tool, is part of the configuration application (GSAC), it supports three main tasks:

1. Selecting access-transit network interfaces (ATI)

This is a two layered task, the first part is routine, the second involves the judgement of the user. First the customer site information is gathered from the global service request and all ATIs which are local to these sites are retrieved from the database. At the same time, the ATI which is closest to each customer site is identified and is marked as the default interface for that customer site. Once this is done the user is able to browse customer site, ATI and service information using other facilities of the tool. By looking at the types of network supported at the various ATIs and their location, together with the information transfer needs, the user exercises his judgement to select the most appropriate ATI for each customer site.

2. Generating transport and resource requirements

The global service request contains information about transport requirements and extra resource requirements, such as database usage. The topology generator retrieves this information and reformats it for the use of the other GSAC tools. Transport requirements are modelled in the global service request as end to and connections, i.e. from one of the clients site to another. In contrast, GSAC is more specific about where requirements are placed. So the topology generator places transport requirement on a particular access network link or on a particular transit network link. This task is performed once the user is satisfied with the ATIs selected and is initiated from the Generate Requirements option in the Task menu.

3. Converting information from RIBS to CLOS

A most important aspect of the topology generator tool is to decompose the global service request in order to identify the information which is relevant to other GSAC tools. Having done this, that information is converted to a form which is acceptable to the tools which are designed to work on it. The global service request is in RIBS format since it is retrieved directly form the database. On the other hand the GSAC tools which take as input groups of abstract communication entities expect them to be in CLOS format (Common Lisp Object System). The fact that this conversion task is performed by the topology generator saves unnecessary duplication of the same conversion being performed by other tools.

The User Interface (see screenshot, side 2)

The way in which information is represented and manner in which that information may be manipulated by the user was considered to be of vital importance to the topology generator tool. In the form in which GSAC exists at present, this tool is always the first to be scheduled¹ and therefore it has the important role of presenting the job in its entirety to the user. To aid simplicity the user interface to the topology generator is integrated within a single window. Apart from the menu bar this window consists of four panes:

Customer Site Menu (top left)

This consists of a button for each locality where the customer has a site for which services are to be provisioned. When the user asks for new information to be shown in the other panes, the topology generator displays information pertaining to the locality selected in this panel.

End to End Connections Graph (top right)

The information presented in this panel consists of all the connections required to support the services needed by one of the customer sites. To view, the user selects a customer site of interest from the Customer Site Menu and then selects End to End Connection from the Display menu bar. The graph drawn links the customer site selected to a nearby access-transit interface which is, in turn, linked to a number of other access-transit interfaces each of which is linked to a customer site which the original customer site needs to communicate with.

Locality Graph (lower left)

This pane displays all the access-transit interfaces within the vicinity of a customer site. The diagram is to scale so that it is easy to see the relative proximity of each ATI to the customer site. Detailed information about an ATI is displayed in the General Display pane when the user clicks on the ATI. This enables him to form an opinion about the relative merits of the ATIs at meeting the service needs pertaining to the client site in question.

General Display (lower right)

This pane is used to display detailed information about customer sites and ATIs. It is also used to display feedback about the processes performed by the topology generator. For example when ATI information is being retrieved from the database their locations are listed here, and when requirements are generated a summary is displayed.

Note 1: Strictly speaking the user sees the task orderer tool before the topology generator, but the latter is the first tool where the user interacts with the problem directly.