The WAN
The WAN
A natural extension of the LAN is the wide area network (WAN). A WAN connects remote LANs and ties remote computers together over long distances. The WAN provides the same functionality as the individual LAN, but on a larger scale - electronic mail, applications, and files can now move throughout the organization-wide internet. WANs are, by default, heterogeneous networks that consist of a variety of computers, operating systems, topologies, and protocols. The most popular internetworking devices for WANs are bridges and routers. Hybrid units called brouters, which provide both bridging and routing functions, are also appearing. The decision to bridge or route depends on protocols, network topology, and security requirements. Internetworking schemes often include a combination of bridges and routers.
The DHHS Departmental Information Management Exchange System (DIMES) is the wide area network for the Department, operated on a fee-for-service basis by the Public Health Service's Parklawn Computer Center (PCC). The DIMES network topology is a physical star, with the PCC as the hub. The PCC uses the FTS 2000 Digital Transmission Service for its backbone communications.
DIMES has evolved over the past decade to support a variety of networking capabilities for organizations within DHHS. These include: LAN to LAN interconnection, gateways to other government and private sector networks, and e-mail backbone capabilities. Network management and security services include long-haul data encryption (DES).
Figure 2-2, below, illustrates a basic LAN/WAN, connecting a Banyan LAN to the Parklawn Computer Center via DIMES. In this configuration, the Communications Server performs the routing functions for the LAN under the direction of the network operating system. No bridges are used in this configuration. While repeaters are not shown on the diagram, they are used on the Work Group LAN rings when required by distance factors.
LAN/WAN ENVIRONMENT
This section provides a
A natural extension of the LAN is the wide area network (WAN). A WAN connects remote LANs and ties remote computers together over long distances. The WAN provides the same functionality as the individual LAN, but on a larger scale - electronic mail, applications, and files can now move throughout the organization-wide internet. WANs are, by default, heterogeneous networks that consist of a variety of computers, operating systems, topologies, and protocols. The most popular internetworking devices for WANs are bridges and routers. Hybrid units called brouters, which provide both bridging and routing functions, are also appearing. The decision to bridge or route depends on protocols, network topology, and security requirements. Internetworking schemes often include a combination of bridges and routers.
The DHHS Departmental Information Management Exchange System (DIMES) is the wide area network for the Department, operated on a fee-for-service basis by the Public Health Service's Parklawn Computer Center (PCC). The DIMES network topology is a physical star, with the PCC as the hub. The PCC uses the FTS 2000 Digital Transmission Service for its backbone communications.
DIMES has evolved over the past decade to support a variety of networking capabilities for organizations within DHHS. These include: LAN to LAN interconnection, gateways to other government and private sector networks, and e-mail backbone capabilities. Network management and security services include long-haul data encryption (DES).
Figure 2-2, below, illustrates a basic LAN/WAN, connecting a Banyan LAN to the Parklawn Computer Center via DIMES. In this configuration, the Communications Server performs the routing functions for the LAN under the direction of the network operating system. No bridges are used in this configuration. While repeaters are not shown on the diagram, they are used on the Work Group LAN rings when required by distance factors.
LAN/WAN ENVIRONMENT
This section provides a