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WAN Technologies Transcription

Welcome to our WAN connection technologies module. A WAN is a wide area network or a network that connects systems located in a large geographical area, typically over leased lines. We can see an example of a WAN at the bottom of the screen here, where our Dallas office is connected to our New York office securely.

We can use several different types of technologies to accomplish this. PSTN, or the Public Switch Telephone Network, ISDN, DSL, Frame Relay, X.25, ATM, Voice over IP, Multi-Protocol Label Switching, or Metro Ethernet. Typically WANs would use dedicated leased lines between two locations over copper wiring. These least lines would be used to create a dedicated link for the wide area network between these two locations.

Today, thanks to the internet, we are not seeing dedicated lines being used as frequently. Most wans are connected through the internet using packet switched networks and virtual private networking between locations to provide a wide area network without having to purchase leased lines. ISDN was one of the early digital wide area network systems.

ISDN technology was available before DSL and cable modems, and it allowed businesses to have higher bandwidth than the dial up that they could use. And this type of service was provided by the local telephone company. ISDN was a digital circuit switch technology that utilized standard copper voice lines, for what is known as the last mile or the short distance between the local central office and the customer's location.

And this utilized CSU DSU technology, or channel-service unit, data-service unit. ISDN was configured with a basic service for data transmission, and a supplementary service to provide call waiting and call transfer. Basic rate interface, or BRI, was a combination of two 64 kilobit per second data channels, known as B channels, and one D channel or control channel, and this provided the user with a combined bandwidth of 144 kilobits per second which is very useful for small offices and home offices.

Primary rate interface, or PRI provided up to 23 B channels, with one D or control channel, each at 64 kilobytes per second. The total bandwidth for this connection was equivalent to a T1 line or 1.544 megabytes per second. Frame relay is another WAN protocol that can provide simple framing and no error connection.

It's a packet switching technology that can be used with permanent virtual circuits or PVC's which provide a customer with a certain bandwidth level and is permanently established, and can be configured with supporting switches. You can also use switched virtual circuits, or SVC which are built dynamically when a connection is required.

Committed information rate, or CIR requires the customer to pay a certain monthly bill to make sure they have a certain minimum bandwidth which will always be available to them. DSL technology, or digital subscriber line, was popular for small offices and home offices because it provided a more affordable digital data service over their existing telephone lines.

It provided much higher speeds than the obsolete ISDN and analog dial up modem technologies. It provided true end to ends connections using asynchronous DSL technology which offered more download bandwidth and with DSL, we did see a security issue, because the individual's computer was always connected to the network.

So it became important for individuals to have firewalls, antivirus software, and also for them to turn off their computer when they were not using it to resist attacks. Previously, when a user was only connecting by dial-up, their computer would only be online for a small portion of the day when they were actually using it, and the other times the computer was not connected, making it virtually impossible for someone to remotely hack into that system.

Asynchronous transfer mode, or ATM, is a connection oriented high bandwidth technology that can be used for wide area networks, or local area networks, and it uses switching and multiplexing. ATM uses 53 byte fixed cells instead of different sizes of frames or packets. Cell switching technology is popular in wide area networks.

For the CISSP examination, you should remember that asynchronous transfer mode, or ATM, uses 53 byte cells instead of packets. SONET, or the synchronous optical network, is a very high speed layer one standard for transferring data over Fiber optic lines. SONET can be used with several different protocols including frame relay, ATM, and SMDS or Switched Muliti-megabit Data Services.

SONET uses multiple channels which is multiplexed together and is commonly used as a backbone in carrier networks. SONET defines transmission rates, optical interfaces and signal formats, and it also defines the way that telephone companies transmit their digital voice and data over optical networks. One interesting quality of SONET is that it is self-healing.

If there is a break in the line, it will automatically use a back-up redundant ring. For the CISSP examination, you should remember that SONET is self healing, and also remember that it is used to transmit data over fiber optic lines. This concludes our WAN connection technologies module. Thank you for watching.