1.  Introduction to Wide Area Networks 2 nd semester 1436-1437

2. Outline  Why do we need a WAN?  What is A wide-area network ?  How do WANs and LANs differ?  WAN and OSI model  WAN Devices  WAN terms  WAN Physical Layer Standards

3. For the purpose of communication and sharing resources. Computer networks LAN

4. Why do we need a WAN? Distributed organizational structures Business needs Remote access Individual user needs

5. Why do we need a WAN?

6.  Without WANs, LANs would be a series of isolated networks.  WANs allow the information exchange, communication and collaboration between branches, organizations and among employees effectively.  Regional or branch offices of an organization  Organizations need to share information with other customer organizations  Employees ( home or mobile worker)  Home computer users

7. WAN  A wide-area network (WAN) is a data communications network that extends across a large geographic area.  It interconnects LANs that are usually separated by large geographic areas.

8. WAN  who own the WAN ?  Is it cost effective for an organization to install its own cable and connect all LANs?  WAN networks often use transmission facilities provided by a service provider, for example, telephone companies.

9. WAN The major characteristics of WANs are as follows:  They connect networks that are separated by wide geographical areas.  They use the services of common carriers/ service provder such as a telephone network, cable company, or satellite service.  They use serial connections of various types to access bandwidth over large geographic areas.  The world’s most popular WAN is the internet ( our course!)

10. WAN and LAN What is the difference between WAN and LAN? WANs differ from LANs in several ways:  LAN  a single building or other small geographic area.  WAN  greater geographic distances.  LANs  typically are owned by the company that uses them.  WAN  use services of a WAN service provider.

11. WAN and OSI model  WAN operations focus primarily on the physical layer (Layer 1) and the data link layer (Layer 2) of the OSI reference model.

12. WAN Standards  WAN access standards typically describe both physical layer delivery methods and data link layer requirements, including physical addressing, flow control, and encapsulation.  WAN access standards are defined and managed by a number of recognized authorities, including the  Telecommunication Industry Association and the Electronic Industries Alliance (TIA/EIA)  International Organization for Standardization (ISO)  Institute of Electrical and Electronics Engineers (IEEE)

13. WAN Standards  Unlike Ethernet LAN standards, which define both Layer 1 and Layer 2 details, most WAN standards focus on either Layer 1 or Layer 2  WAN physical layer protocols describe how to provide electrical, mechanical, operational, and functional connections to the services of a communications service provider.  WAN data-link protocols describe how data is encapsulated for transmission toward a remote location, and the mechanisms for transferring the resulting frames.

14. WAN Physical Layer Concepts  The WAN access physical layer describes the physical connection between the company network and the service provider network.  The WAN physical layer includes several devices and terms specific to wide-area networks.  In the following slides:  WAN Devices  WAN Physical Layer Terminology

15. WAN Devices  The following devices are used in WANs

16. Router  Offer many services, including internetworking and WAN interface ports used to connect to the service provider network.  With some types of WAN interfaces, an external device, such as a DSU/CSU or modem is required to connect the router to the service provider.  The routers that reside within the service provider WAN backbone called Core router

17. WAN Switches  A multiport internetworking device used in service provider networks.  These devices typically switch traffic and operate at Layer 2.

18. Modem  A modem is a device that interprets digital and analog signals, enabling data to be transmitted over voice-grade telephone lines ( analog lines).  Modulating and demodulating signals ( Modem).

19. CSU/DSU  For digital lines, a channel service unit (CSU) and a data service unit (DSU) are required.  We won’t go into the differences here.  The CSU/DSU provides signal timing for communication between devices.  The two are often combined into a single piece of equipment, called the CSU/DSU.  The CSU/DSU may be  Separate device like a modem ( External CSU/DSU)  Built into the interface card in the router.

20. nalhareqi©2015 To routerTo T1 circuit

21. Access Server  An access server acts as a concentration point for dial-in and dial-out connections

22. WAN Devices  The type of devices used depends on the WAN technology implemented

23. WAN Terms  To understand WAN technologies, you need to understand the different WAN terms and connection types that can be used to connect your networks together.

24. WAN Terms

25. Customer Premises Equipment (CPE)  The devices and inside wiring located at the premises of the subscriber, connected with a telecommunication channel of a services provider.  The subscriber either owns or leases the CPE.  A subscriber: is a company that arranges for WAN services from a service provider or carrier.

26. WAN Terms Local loop  The copper or fiber cable that connects the CPE at the subscriber site to the central office (CO) of the service provider. The local loop is sometimes called the “last mile.” Central office (CO)  A local service provider facility or building where local cables link to long-haul fiber-optic communications lines through a system of switches and other equipment.

27. WAN Terms

28. Data Communications Equipment (DCE)  Also called data circuit-terminating equipment, the DCE consists of devices that put data on the local loop. ( CSU/DSU )  The DCE primarily provides an interface to connect subscribers to a communication link on the WAN cloud. Data Terminal Equipment (DTE)  The customer devices that pass the data from a customer network or host computer for transmission over the WAN. ( Router)  The DTE connects to the local loop through the DCE.

29. WAN Terms

30. nalhareqi©2015

31. WAN Terms Demarcation point  A point established in a building or complex to separate customer equipment from service provider equipment.  Physically, the demarcation point is the cabling junction box, located on the customer premises, that connects the CPE wiring to the local loop. nalhareqi©2015

32. WAN Terms nalhareqi©2015

34. WAN Physical Layer Standards  WAN physical-layer protocols describe how to provide electrical, mechanical, operational, and functional connections for WAN services.  The WAN physical layer also describes the interface between the DTE and DCE. nalhareqi©2015

35. WAN Physical Layer Standards  Choosing a protocol is largely determined by the service provider’s method of facilitation  The EIA and ITU-T develops the standards that allow DTEs to talk to DCEs

36. WAN Physical Layer Standards The DTE/DCE interface for a particular standard defines the following specifications  Mechanical/physical - Number of pins and connector type  Electrical - Voltage levels for 0 and 1  Functional - Specifies the functions that are performed by assigning meanings to each of the signaling lines in the interface  Procedural - Specifies the sequence of events for transmitting data nalhareqi©2015

37. WAN Physical Layer Standards nalhareqi©2015

38. Review  Are WANs Necessary?  How do WANs and LANs differ?  Where do WANs operate on the OSI model?  What devices are used in WANs?  WAN terms  WAN Physical Layer standards