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3.1 | WAN Communication |
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3.1.1 | WAN design requirements |
WAN communication occurs between
geographically separated areas. When a local end station wants to
communicate with a remote end station (that is, an end station located
at a different site), information must be sent over one or more WAN
links. Routers within WANs are connection points of a network. These
routers determine the most appropriate path through the network for
the required data streams.
As you have learned, WAN communication is often called a service because the network provider often charges users for the WAN services it provides. Circuit-switching and packet-switching technologies are two types of WAN services, each of which has advantages and disadvantages. For example, circuit-switched networks offer users dedicated bandwidth that cannot be infringed upon by other users. In contrast, packet switching is a method in which network devices share a single point-to-point link to transport packets from a source to a destination across a carrier network. Packet-switched networks have traditionally offered more flexibility and used network bandwidth more efficiently than circuit-switched networks. Traditionally, relatively low throughput, high delay, and high error rates have characterized WAN communication. WAN connections are also characterized by the cost of renting media (that is, wire) from a service provider to connect two or more campuses together. Because the WAN infrastructure is often rented from a service provider, WAN network designs must optimize the cost of bandwidth and bandwidth efficiency. For example, all technologies and features used in WANs are developed to meet the following design requirements:
Recently, traditional shared-media networks are being overtaxed because of the following new network requirements:
Compared to current WANs, the new WAN infrastructures must be more complex, based on new technologies, and able to handle an ever-increasing (and rapidly changing) application mix with required and guaranteed service levels. In addition, with a 300% traffic increase expected in the next five years, enterprises will feel even greater pressure to contain WAN costs. Network designers are using WAN technologies to support these new requirements. WAN connections generally handle important information and are optimized for price and performance bandwidth. The routers connecting the campuses, for example, generally apply traffic optimization, multiple paths for redundancy, dial backup for disaster recovery, and quality of service (QoS) for critical applications. The table summarizes the various WAN technologies that support such WAN requirements.
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