In networking, the term enterprise refers to an entire organization, including its local and remote offices, a mixture of computer systems, and a number of departments. Enterprise-wide computing must therefore take into account the breadth and diversity of a large organizationís computer needs. Enterprise-wide networks expand on the simple and hybrid LAN topologies. As a result, their topologies require more interconnection devices and more reliable routes than simple LAN topologies can provide. An enterprise-wide network may include or form part of a WAN, but an enterprise-wide network connects only one organizationís resources. A WAN (for example, the Internet) may connect resources from many different organizations.
As with LAN topologies, a number of variations on the basic enterprise-wide topologies exist. This section describes some popular methods of arranging these larger networks.
A network backbone is the cabling that connects the hubs, switches, and routers on a network. Backbones usually are capable of more throughput than the cabling that connects workstations to hubs. This added capacity is necessary because backbones carry more traffic than any other cabling in the network.
A serial backbone is the simplest kind of backbone network. It consists of two or more hubs connected to each other by a single cable. Although the serial backbone topology could be used for enterprise-wide networks, it is rarely implemented for that purpose.
A distributed backbone consists of a number of hubs connected to a series of central hubs or routers in a hierarchy. This kind of topology allows for simple expansion and limited capital outlay for growth, because more layers of hubs can be added to existing layers.
A distributed backbone also provides network administrators with the ability to segregate workgroups and therefore manage them more easily. It adapts well to an enterprise-wide network confined to a single building, where layers of hubs can be assigned according to the floor or department.
The collapsed backbone topology uses a router or switch as the single central connection point for multiple subnetworks. In a collapsed backbone, a single router or switch that makes up the collapsed backbone must contain multiprocessors to handle the heavy traffic going through it. The dangers of using this arrangement relate to the fact that a failure in the central router or switch can bring down the entire network. In addition, because routers cannot move traffic as quickly as hubs, using a router may slow data transmission.
A parallel backbone is the most robust enterprise-wide topology. This variation of the collapsed backbone arrangement consists of more than one connection from the central router or switch by more than one cable. The most significant advantage of using a parallel backbone is that its redundant links ensure network connectivity to any area of the enterprise. Parallel backbones are more expensive than other enterprise-wide topologies because they require much more cabling than the others. However, they make up for the additional cost by offering increased performance.
In a mesh network, routers are interconnected with other routers, with at least two pathways connecting each router. The mesh network is more complex than the backbone networks. In fact, it typically contains several different backbone networks. Indeed, the term "mesh network" is a general topology term that can apply to many different arrangements of workgroups and interconnection devices.