1 Wide Area Network

2 What is a WAN? A wide area network (WAN ) is a data communications network that covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as telephone companies.

LANs and WANs LAN A LAN connects computers, peripherals, and other devices in a single building or other small geographic area. LANs typically are owned by the company or organization that uses them. WAN A WAN allows the transmission of data across greater geographic distances. An enterprise must subscribe to a WAN service provider to use WAN carrier network services. 3

WAN Here are the three major characteristics of WANs: –WANs generally connect devices that are separated by a broader geographic area than can be served by a LAN. –WANs use the services of carriers, such as telephone companies, cable companies, satellite systems, and network providers. –WANs use serial connections of various types to provide access to bandwidth over large geographic areas. 4

5 WAN Users WANs are used to connect local area networks (LANs) together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are private that uses either dedicated or switched communication link. Others are public that use the global Internet infrastructure.

6

7 WAN and OSI 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.

8

9 How to Build a WAN? WANs are most often built using leased lines. At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other. A set of switches and routers are interconnected to form a Wide Area Network. The switches can be connected in different topologies such as full mesh and half mesh.

10 WAN Internet

11

1- Dedicated (Point-to-Point) Connection A point-to-point link provides a single, pre-established WAN communications path from the customer premises through a carrier network to a remote network (It is a permanent full time connection). 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 this user only. 12

1- Dedicated (Point-to-Point) Connection These circuits are generally priced based on bandwidth required and distance between the two connected points. Advantage: Line is always reserved for the user Disadvantage: Expensive 13

14 2- Switched Network Switched network - Several users share the same line or the bandwidth of the line. There are two types of switched networks: –Circuit switching –Packet switching

Circuit Switching Circuit Switching allows data connections to be established when needed and then terminated when communication is complete. This works like a normal telephone line works for voice communication. When a router has data for a remote site, the switched circuit is initiated. When the two networks are connected and authenticated, they can transfer data. When the data transmission is complete, the call can be terminated.

2.1 - Circuit Switching Cost is determined by the connection time. Examples: ISDN Advantage: Cheap Disadvantage: Network is reserved for the connection even if no data is sent. Any failure in circuits will stop the connection, and require another call to reserve a new circuits. Some times you wait until network is ready. 16

2.2 - Packet Switching Many WAN users do not make efficient use of the fixed bandwidth that is available with dedicated or switched circuits, because the data flow fluctuates. Packet switching is a WAN technology in which users share common carrier resources. It splits traffic data into packets that are routed over a shared network. Packet-switching networks do not require a circuit to be established, and they allow many pairs of nodes to communicate over the same channel 17

2.2 - Packet Switching Because this allows the carrier to make more efficient use of its infrastructure, the cost to the customer is generally much better than with point-to-point lines. Examples of packet switching technologies: X.25, ATM, Frame relay Advantages: –Fast, but slower than circuit switching. –Cheap –Connection is always there, due to many paths that data can move through 18

3- Public WAN connection Public connections use the global Internet infrastructure. Until recently, the Internet was not a viable networking option for many businesses because of the significant security risks and lack of adequate performance guarantees in an end-to-end Internet connection. However, with the development of Virtual private network (VPN) technology, the Internet is become an inexpensive and secure option for connecting. 19

20 Virtual private network (VPN) Is a technology widely used in a public network 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.

21