1. Introduction to Wide Area Networks
1st semester

2. WAN switching and WAN connections
Chapter1
Chpater1
Introduction
WAN switching and WAN connections
WAN Hierarchal model

3. Part1 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

4. Part1 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

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

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

7. Why do we need a WAN?

8. Why do we need a WAN?
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
Regional or branch offices of an organization need to be able to communicate and share data with the central site.
Organizations need to share information with other customer organizations. For example, software manufacturers routinely communicate product and promotional information to distributors that sell their products to end users.
Employees who travel on company business frequently need to access information that resides on their corporate networks.
Home computer users also need to send and receive data across increasingly larger distances
Consumers now commonly communicate over the Internet with banks, stores, and a variety of providers of goods and services It is not feasible to connect computers across a country, or around the world, with physical cables.

9. Part1 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

10. WAN
A wide-area network (WAN) is a data communications network that extends across a large geographic area to interconnect LANs.
WANs provide for the exchange of data packets/frames between routers/switches and the LANs they support.
A WAN operates beyond the geographic scope of a LAN

11. 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 such as a telephone network, cable company, or satellite service .
But even so, it wouldn’t exactly be cost effective or efficient to install your own cable and connect all of your company’s remote locations yourself, now would it? A much better way to go about doing this is to simply lease the existing installations that service providers already have in place—and then save big time
A WAN is owned by a service provider . An organization must pay a fee to use the provider’s network services to connect remote sites
Service providers provide links to interconnect remote sites for the purpose of transporting data, voice, and video.

12. 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 provider.
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!)

13. Part1 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

14. 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.
Whereas a LAN connects computers, peripherals, and other devices in a single building or other small geographic area, a WAN allows the transmission of data across greater geographic distances. In addition, an enterprise must subscribe to a WAN service provider to use WAN carrier network services. LANs typically are owned by the company or organization that uses them.
LANs typically are connected workstations, printers, and other devices within a limited geographic area such as a building.
All the devices in the LAN are under the common administration of the owner of that LAN, such as a company or an educational institution.

15. Part1 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

16. WAN and OSI model
WAN operations focus primarily on Layer 1 and Layer 2 of the OSI reference model.
Layer 2 protocols define how data is encapsulated for transmission toward a remote location, and the mechanisms for transferring the resulting frames. A variety of different technologies are used, such as the Point-to-Point Protocol (PPP), Frame Relay, and Asynchronous Transfer Mode (ATM). Some of these protocols use the same basic framing or a subset of the High-Level Data Link Control (HDLC) mechanism.

17. WAN Standards
WAN access standards typically describe both physical layer delivery methods and data link layer requirements.
WAN access standards are defined and managed by a number of recognized authorities, including the TIA/EIA, ISO, and IEEE.
Unlike Ethernet LAN standards, which define both Layer 1 and Layer 2 details, most WAN standards focus on either Layer 1 or Layer 2

18. WAN Standards
The WAN access physical layer describes the physical connection between the company network and the service provider network.
WAN data-link protocols describe how data is encapsulated for transmission toward a remote location, physical addressing and the mechanisms for transferring the resulting frames.

19. WAN Physical Layer Concepts
The WAN physical layer includes several devices and terms specific to wide-area networks.
In the following slides:
WAN Devices
WAN Physical Layer Terminology

20. WAN Devices The following devices are used in WANs
there are various methods, and therefore devices, that are used to access the WAN connection.
Service providers also have specific WAN devices within their network and devices that are required to interconnect to other WAN providers.

21. 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
Provides internetworking and WAN access interface ports that are used to connect to the service provider network. These interfaces may be serial connections, Ethernet, or other WAN interfaces.
Core router/multilayer switch: These are the routers and multilayer switches that reside within the service provider WAN backbone. To fulfill this role, the
devices must be able to support routing protocols being used in the core and multiple high speed interfaces used in the WAN core backbone. They must also
be able to forward IP packets at full speed on all of those interfaces. Key core routers interconnect to other provider core routers.

22. WAN Switches
A multiport internetworking device used in service provider networks.
These devices typically switch traffic and operate at Layer 2.
Figure 3-5 illustrates two routers at remote ends of a WAN that are connected by WAN switches.

23. 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).
At the source, digital signals are converted to a form suitable for transmission over analog communication facilities. At the destination, these analog signals are returnedto their digital form.
Modulates an analog carrier signal to encode digital information, and also demodulates the carrier signal to decode the transmitted information.
Dialup modem: Considered to be a legacy WAN technology, a voiceband modem converts (i.e., modulates) the digital signals produced by a computer into
voice frequencies that can be transmitted over the analog lines of the public telephone network. On the other side of the connection, another modem converts
the sounds back into a digital signal (i.e., demodulates) for input to a computer or network connection.
Broadband modem - A type of digital modem used with high-speed DSL or cable Internet service. Both operate in a similar manner to the voiceband modem, but use higher broadband frequencies and transmission speeds.
A dial-up modem converts the digital signals into voice frequencies that can be transmitted over the analog lines of the public telephone network
Faster modems, such as cable modems and DSL modems, transmit using higher broadband frequencies

24. 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.
The CSU provides termination for the digital signal and ensures connection integrity through error correction and line monitoring.
The DSU converts the line frames into frames that the LAN can interpret and vice versa.

25. To T1 circuit
To router
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26. Access Server
An access server acts as a concentration point for dial-in and dial-out connections
Figure 3–6 illustrates an access server concentrating dial-out connections into a WAN.
Access server - Concentrates dialup modem, dial-in and dial-out user communications. Considered to be a legacy technology, an access server may have a mixture of analog and digital interfaces and support hundreds of simultaneous users.

27. WAN Devices
The type of devices used depends on the WAN technology implemented
WAN technologies are either circuit-switched or packet-switched. The type of devices used depends on the WAN technology implemented.
Communication servers—Concentrate dial-in and dial-out user communication.
Access server: Devices used to concentrate the dial-in and dial-out user communications of dialup modems. Considered to be a legacy technology, an access
server may have a mixture of analog and digital interfaces and support hundredsof simultaneous users.

28. 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.
This section will discuss the different WAN terms

29. WAN Terms
Devices on the subscriber premises are called customer premises equipment (CPE).
The subscriber owns the CPE or leases the CPE from the service provider.
A copper or fiber cable connects the CPE to the service provider’s nearest exchange or central office (CO).
This cabling is often called the local loop, or "last-mile".

30. WAN Terms 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.

31. 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.

32. WAN Terms

33. WAN Terms 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.

34. WAN Terms
A WAN network normally consists of 2 DTE networks connect through a DCE network.
The DCE network includes the CSU/DSU at both ends, the Telco wiring, and Telco switches. DCE devices provide clocking to DTE interfaces, eg: router serial interfaces.

35. WAN Terms
Toll network
This consists of the long-haul, all-digital, fiber-optic communications lines, switches, routers, and other equipment inside the WAN provider network.

36. WAN Terms
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37. 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.
It is usually placed for easy access by a technician.
The demarcation point is the place where the responsibility for the connection changes from the user to the service provider. This is very important, because when problems arise, it is necessary to determine whether the user or the service provider is responsible for troubleshooting or repair.
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38. WAN Terms
In the US, the WAN provider provides the local loop into the customer premises, making the demarcation point between the the DCE (usually a CSU/DSU) and the CO switch.
In other countries, the demarcation point is between the DTE and the DCE.
However, service providers often provide the network terminating unit (NTU) to the customer, and a customer connects his/her router to the NTU via a V.35 or RS-232 serial interface.
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41. Part1 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

42. 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.
The DTE/DCE interface uses various physical layer protocols
EIA/TIA-232
EIA/TIA-449/530
EIA/TIA-612/613
V.35
X.21
The EIA and ITU-T develops the standards that allow DTEs to talk to DCEs
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43. 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
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44. WAN Physical Layer Standards
Choosing a protocol is largely determined by the service provider’s method of facilitation
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45. Review Are WANs Necessary? How do WANs and LANs differ?
Where do WANs operate on the OSI model?
What devices are used in WANs? And where ?
WAN terms
WAN Physical Layer standards