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22.4 WAN Communication Link Options
WAN Communication Link Options Section 22: Introducing WAN Technologies Options for implementing WAN solutions involve technology, speed, and cost factors. WAN connections can be carried over a private infrastructure or over a public infrastructure such as the Internet. Private connections include dedicated and switched communication link options. Dedicated communication links: When permanent dedicated connections are required, pointtopoint lines are used. These lines have various capacities and physical limitations, and the user must decide how much it is willing to pay for dedicated lines. A pointtopoint link provides an established WAN communication path from the customer premises through the provider network to a remote destination. Pointtopoint WAN links are usually leased from a carrier and are also called l e a s e d l i n e s . Switched communication links: Many WAN users do not efficiently use the fixed bandwidth that is available with dedicated communication links because data flow fluctuates. Service providers have data networks available to appropriately service these users. In packetswitched networks, the data is transmitted in labeled cells, frames, or packets over a common infrastructure that is used by several customers at the same time. Different technologies can be used to ensure privacy and isolation of different customers and to provide desired bandwidth requirements and service level agreements. Internet communication links: Public connections use the global Internet infrastructure. The development of VPN technology made the Internet an inexpensive and secure option for connecting teleworkers and remote offices when performance guarantees are not critical. Internet WAN connection links are provided through broadband services such as DSL, cable modem, and broadband wireless. Broadband connection options are typically used to connect telecommuting employees to a corporate site over the Internet. LeasedLine Options Leased lines can be implemented as pointtopoint links when a private intranet is built or when public connections are made to an ISP. The selection of the link type and its associated bandwidth must be weighed against monthly recurring costs. The higher the bandwidth, the higher the monthly expense. In North America, Japan, and South Korea, the Tcarrier system of multiplexed communication channels is used to provide data services. Tcarrier Leased Line Common Uses Description Bandwidth Common Use Description Bandwidth Common Use DS0 64 Kb/s Bank ATMs DS1 (T1) 1.544 Mb/s Branch office communication DS3 (T3) 44.736 Mb/s Headquarters communication Most countries outside North America, Japan, and South Korea use a similar system called Ecarrier. The number of channels and the signaling in Ecarrier systems are incompatible with Tcarrier. Cisco routers can accommodate both Ecarrier and Tcarrier interface modules. Ecarrier Leased Line Common Uses Description Bandwidth Common Use Description Bandwidth Common Use DS0 64 Kb/s Bank ATMs DS1 (E1) 2.048 Mb/s Branch office communication DS3 (E3) 34.368 Mb/s Headquarters communication Up Next: PointtoPoint Connectivity