A Wide Area Network consists of various network connections between multiple sites. A Wide Area Network is used to provide remote connectivity between sites usually using speeds considerable less than that of local area network connections. Numerous wide area network technologies and connectivity options exist which allow the connection of remote sites.
A modern wide area network must be able to support the bandwidth and network application requirements in order to reliably deliver both current and planned network services. Many newer network applications like Voice over IP (VoIP) and collaborative messaging require special network enabled services. These can be readily deployed by utilizing advanced router features. This allows for the provisioning of services such as network security, quality of service (QoS), link redundancy and IP multicasting.
Wide area network services
Wide area network services normally operate at the physical and data-link layers of the OSI model. Wide area network services such as Frame Relay, ATM and ISDN are popular mature technologies due to their ability to provide high speed digital services. X.25 and PSTN can be used to offer low speed connections at remote sites. Broadband solutions such as xDSL and Cable Modem can provide connectivity via an iVPN (encrypted tunnel) through the Internet. While technologies such as Microwave Wireless and Satellite may be used at extreme remote sites where normal Wide Area Network services may not exist.
There are many choices of wide area network services available such as:
- Frame relay that allows the speed up to 2.048 Mbps or higher
- Dedicated leased line that allows speed up to 2.048 or higher
- ISDN BRI (up to 128 Kbps)
- ISDN PRI (up to 2.048 Mbps)
- ATM (up to 155 Mbps or higher)
- X25 (up to 56 Kbps)
- Analogue modem (PSTN) allows the speed up 56 Kbps with compression
- Broadband xDSL & Cable-Modem
- Wireless (Microwave and satellite)
Frame relay and ISDN is a preferred service over X25 even at lower speeds. While, ISDN is a preferred service over analogue PSTN.
WAN technologies are normally categorized into the following classes of services;
- Leased line
- Circuit switched or
- Packet switched.
Leased line services use dedicated links provisioned from a carrier, while circuit switched services transmit data on the completion of a connection call (PSTN or ISDN) and packet switched services (Frame Relay, X.25 and ATM) use the carriers shared infrastructure to transmit data over virtual-circuits (VC).
Wide area network services
Packet switched services such as Frame Relay and ATM are popular due to their generally lower cost (per Kbps of bandwidth) and flexibility in provisioning virtual circuits across a single physical router interface. Most Permanent Virtual Circuits (PVCs) allow a circuit size to be predefined which guarantees a minimum level of service, and when network requirements change, the circuit size can be modified as needed.
WAN Bandwidth requirement
Circuit switched services such as those provided by ISDN and analogue PSTN, require a call to be made to establish a circuit for the duration of the connection. ISDN can also be often used as a connection point for other Wide Area Network services such as Frame Relay or X.25. It can also be used for dial on demand or link backup based systems. Leased lines provide full time connectivity with the connection pathway being permanently provisioned from the carrier. Newer broadband technologies such as xDSL offer fast connection speeds (as compared to standard PSTN) over standard copper telephone wire.
This technology is normally reserved for Internet based connections and may be limited in its service availability. Line of site microwave (wireless) and satellite can be used in extreme remote environments were carrier Wide Area Network services may not exist. These services offer a variety of connection speeds. Satellite may offer up to 512 Kbps, while line of site microwave can reliably offer up to 52 Mbps (or higher). It is important to note that Wide Area Network services do vary significantly based on availability (location and service provider), bandwidth, service levels and cost. Cost and bandwidth are the two main influencing factors in selecting a particular carrier’s Wide Area Network service. The Wide Area Network service selected will influence the type of physical interface required on the connecting router. Due to the number of Wide Area Network services and physical
Wide Area Network interface types available, a modular router is often preferred to provide flexibility in the choice of the Wide Area Network service connection.
Wide area network diagram
The above diagram is a basic wide area network connection – as basic wide area network model you can apply to your wide area network infrastructure.
Check out about:
- firewall security standards – guidelines in secured firewalls
- WAN technologies - types and topologies
- Understanding IP Routing guide
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