Bridges, hubs, routers and switches are used as interworking devices. They permit subnets and backbone networks to be created and transitions from LANs to WANs. In virtual LANs (VLANs) the traffic flows (unicast, multicast and broadcast traffic) can be configured with network management systems. Bridges and hubs operate at address level (Layer 2), router on the Network Layer (Layer 3).
The switch technology has been significantly enhanced in recent years. Today switches not only replace bridges and hubs, but are also available as very powerful switches on Layer 3 and Layer 4 and take the place of classical routers. Despite greater bandwidths, the assignment of bandwidth and prioritization of data streams is becoming increasingly important in order to optimize transmission costs and prevent bottlenecks for higher-priority applications. Owing to the wide distribution of the Internet and also of intranets and extranets, further development of interworking devices will concentrate primarily on TCP/IP products. Routers and switches are generally used in current networks.
A distinction is made between a:
bridge
switch
Layer 3 switch
hub
router