Wide Area Network Technologies

A Wide Area Network (WAN) is a computer network covering multiple distance areas, which may spread across the entire world. WAN must be able to grow as needed through often connect multiple smaller networks, such as LANs or MANs. The world's most popular WAN is the Internet. The key difference between WAN and a LAN technology is scalability. 

Virtual private network (VPN) is a technology widely used in a public switched network (PSTN) to provide private and secured WAN for an organization. VPN uses encryption and other techniques to make it appear that the organization has a dedicated network, while making use of the shared infrastructure of the WAN. WANs are often built using leased lines. WANs can also be built using less costly circuit switching or packet switching methods. Network protocols including TCP/IP deliver transport and addressing functions. 

WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer. Key technologies often found in WANs include SONET/SDH, Frame Relay, X.25, ATM, DSL and PPP.

•        SONET/SDH:

 Synchronous Optical Network is an international standard for high speed communication over fiber-optic networks. The SONET establishes Optical Carrier (OC) levels from 51.8 Mbps to 10 Gbps (OC-192) or even higher. Synchronous Digital Hierarchy (SDH) is a European equivalent of SONET

•  Frame Relay:

A high-speed packet-switched data communications service. Frame relay is widely used for LAN-to-LAN interconnect services, and is well suited to the bursty demands of LAN environments. 

•  X.25:

The X.25 protocol allows computers on different public networks to communicate through an intermediary computer at the network layer level. 

•   ATM:

A dedicated-connection switching technology that organizes digital data into 53-byte cell units. Individually, a cell is processed asynchronously relative to other related cells and is queued before being multiplexed over the transmission path. Speeds on ATM networks can reach 10 Gbps. 

• DSL:

Digital Subscriber Line, is arguably the successor to ISDN. It also utilizes a special line set up by the telecom company, but utilizes a special “DSL” modem to translate the high-speed DSL signal to a network-friendly language. DSL can be as slow as 256 Kbps and some of the fastest DSL lines operate at speeds exceeding 10 Mbps. Connections on the new ADSL2+ Technology can now go up to 15 Mbps in certain areas

• PPP:

A point-to-point link provides a single, per-established WAN communications path from the customer premises through a carrier network, such as a telephone company, to a remote network. Point-to-point lines are usually leased from a carrier and thus are often called leased lines. For a point-to-point line, the carrier allocates pairs of wire and facility hardware to your line only.