Unlike LAN or Local Area Network, WAN or a Wide Area Network spans over a large geographical area, which can be over a state, province or country. WANs often connect multiple smaller networks, such as LANs or metro area networks (MANs). One good example of a WAN is the Internet. Many WANs are corporate or research networks that utilize leased lines.
WANs normally use the public telecommunication system to provide cost-effective connection between LANs. WAN communication can use the public packet-switched networks, satellite communication networks, and wireless packet switching network. Since these links are supplied by independent telecommunications utilities, they are commonly referred to as ‘communication cloud’. Routers perform this type of activity. They store the message at LAN speed and re-transmit it across the communication cloud at a different speed. When the entire message has been received at the access router of the remote LAN, it is once again forwarded at LAN speed. A typical speed at which a WAN interconnects varies between 9600 bps for a leased line to 40 Gbps for a SDH/SONET connection.
Types of WAN Connection
WAN connections are usually of these types:
- Leased Connection – It is a permanent full time connection. When a dedicated connection is used, then the entire cable bandwidth is leased and the user enjoys exclusive usage rights.
- Switched network – Several users share the same bandwidth of the line. There are two types of switched networks:
- Circuit switching – This is a temporary connection between two points such as dial-up or ISDN.
- Packet switching – This is a connection between multiple points. It breaks data down into small packets to be sent across the network. A virtual circuit can improve performance by establishing a set path for data transmission. This will shave some overhead of a packet switching network. Frame Relay and X.25 are packet switching technologies. Speeds can vary from 56Kbps to 2.048Mbps.
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WAN Connection Technologies and Protocols
WAN technologies function at the lower three layers of the OSI reference model:
• Physical Layer (L1)
• Data Link Layer (L2)
• Network Layer (L3)
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Here are some of the important protocols used by a WAN connection:
- X.25 – This set of protocols specify how to connect computer devices over an inter-network. Normally X.25 is used on packed switching PDNs (Public Data Networks) and has a speed of 64Kbps. A line must be leased from the LAN to a PDN to connect to an X.25 network. These protocols use a great deal of error checking if used over unreliable telephone lines.
- Frame Relay – Frame Relay is a Date Link and Physical Layer specification that provides high performance. Error checking is handled by devices at both sides of the connection. A permanent virtual circuit (PVC) is established between two points on the network. Frame Relay facilities are less prone to error than X.25 and they also use less overhead. Frame Relay provides features for dynamic-bandwidth allocation and congestion control.
- Integrated Services Digital Network (ISDN) – This is a set of digital services that transmit voice and data over existing phone lines. ISDN can offer a cost-effective solution for remote users who need higher-speed connections compared to that offered by analog dial-up links. A device resembling a modem (called an ISDN modem) is used to connect to ISDN. The computer and telephone lines are plugged into it.
- PPP – Point-to-Point protocol (PPP) is used to create point-to-point links between different vendor equipment. It allows authentication and multilink connections and can be run over asynchronous and synchronous links.
- HDLC – High-Level Data Link Control (HDLC) is a connection-oriented protocol at the Data Link layer. It has the benefit of having very little overhead. The HDLC header carries no identification of the type of protocol being carried inside the HDLC encapsulation. So, each vendor uses their own Network layer protocol identification and each vendor’s HDLC is proprietary for their equipment.
- SDLC – Synchronous Data Link Control (SDLC) is a bit-oriented, full-duplex serial protocol that is spread across numerous protocols.
- Asynchronous Transfer Mode (ATM) – ATM is designed to handle data, video, and voice traffic simultaneously in real time. It uses fixed length data packets of 53 bytes called cell switching. It uses hardware devices to perform the switching of the data.
- Synchronous Optical Network (SONET) – Transmits data, voice, and video over the fiber optic cables widely used for long-distance transmission. SONET defines data rates in terms of optical carrier (OC) levels and uses multiplexing. The transmission rate of OC-1 is 51.8 Mbps.
WAN is mainly used to cover large geographical areas so that long distance businesses can connect over one network. It helps in sharing of software and resources with connecting workstations. But WAN connection can be very costly and slow. Also you need a good firewall to protect the network from outsiders. If reliability is needed for a time critical application, WANs can be quite unreliable, as delay in the information transmission is varied and wide. For this reason, WANs can only be used if the necessary error detection or correction software is in place, and if propagation delays can be tolerated within certain limits.
To know more about other Networks like VPN, naviagte through the course Virtual Private Networks for beginners – VPN, Cisco training. As the demand for professionals knowledgeable in Networking and Switching technology is on the rise, it may be a good idea to take the CCNP Switch Examto add more feathers to your cap.