Network Sales and Services Handbook (Cisco Press Networking Technology)
Networks are defined as one of the following four categories, depending on the geographic relation of the network components:
Wide Area Network (WAN) Interconnection spanning geographically separate networks.
Campus Area Network (CAN) Interconnection of local area networks (LANs) within a limited geographical space.
Metropolitan Area Network (MAN) Designed for a town or city; larger than LANs and smaller than WANs.
Local Area Network (LAN) Spans across a small area; often within a building or on a single floor within a building.
These network components are broken down into one of the following four basic types of internetworking hardware:
Hubs (LAN) Connect multiple LAN hosts/users to a single device, in turn connected to the network.
Bridges (LAN) Logically separate network segments within the same network.
Switches (LAN/WAN) Similar to bridges, switches provide a unique network segment on each switch port, separating LAN collision domains.
Routers (LAN/WAN) Interconnect different networks and separate broadcast domains.
Internetworks are made up of the following three-tiered hierarchical model:
Core The backbone layer providing (optimal) transport between sites.
Distribution Layer providing policy-based connectivity.
Access Layer providing site/user access to the network.
Oversubscription of a WAN port can be effective for achieving more economical network connectivity in an enterprise organization because data connections tend to be bursty, or used intermittently.
Oversubscription is often measured as a percentage; for example, 200 or 400 percent oversubscription. For example, four 32 Kbps permanent virtual circuits (PVCs) a total CIR of 128 Kbps attached to a 64-Kbps port represents a 200 percent subscription.