Networks and Communication Links

Normally, locations will have some form of electronic communications, which could range from a dial-up modem connected to a telephone system, a dedicated Wide-Area Network, the Internet or a satellite link. Normally the link should have a relatively high speed and reliable on-line communication channel with as many satellite locations as possible. However, line speeds as low as 48K are supported.

The communications network must be a tree structure, which means that there is a unique path between one location and another. The Hub is the root of the tree. It is possible to have links between one satellite and another, using Location Groups ‑ in this case there is more than one path between locations. Refer to Location Groups.

The following diagram shows some of the different configurations possible, when Groups are not used. For a diagram showing the use of Groups, refer to Location Groups.

Examples of tree structures for locations

The relationship between locations is described in terms of a family tree: there are parents, children, ancestors and descendants. For example, in Figure 3:1.: Examples of tree structures for locations, the relationships between locations A, B, C, D and E are described as follows:

• A is the parent of B and C.

• B and C are the children of A.

• B, C, D and E are the descendants of A.

• A, C and D are the ancestors of E

Every location except the Hub has a parent. The parent of each location is stored in the Global database. The parent-child relationships define the connectivity of the communications network, and allow the Global daemons to find the path from one location to another.