1. WAN Technologies
Lesson 8

2. Objectives Exam Objective Matrix Technology Skill Covered
Exam Objective Number
Types of Circuit Switching
Categorize WAN technology types and properties.
• Properties:
• Circuit switch
• Packet switch
3.4
Transmission Media
• Types:
• DWDM
• Satellite
• Cellular
• WiMAX
• LTE
• HSPA+
• Fiber
• PON
• Speed
• Transmission media
• Distance

3. Objectives Exam Objective Matrix Technology Skill Covered
Exam Objective Number
Various WAN Technologies
Categorize WAN technology types and properties.
• Types:
• T1/E1
• T3/E3
• DS3
• OCx
• SONET
• SDH
• ISDN
• Cable
• DSL
• Dialup
• Frame relay
• ATMs
• Properties:
• Speed
• Transmission media
• Distance
3.4

4. Objectives Exam Objective Matrix Technology Skill Covered
Exam Objective Number
Describe different network topologies.
• MPLS
3.5
Remote Access
Explain the methods of network access security.
• Tunneling and encryption:
• VPN
5.2

5. Circuit Switching
A type of communications that establishes a dedicated communications channel for the duration of a given transmission
The oldest means by which communications channels were established
Example: Basic circuit switched network is the telephone service.

6. How Circuit Switching Works
In circuit switching, a connection is established from one end of the communications link to the other before data is sent

7. Packet Switching
Data is broken up into small blocks of data called A network communications technology that only opens up connections long enough for a small data packet to move from one network segment to another
packets
Regardless of type, content, or structure
Each packet is given enough information to find its own path to its intended destination

8. How Packet Switching Works

9. Developed in 1961, evolved into packet switching
Message Switching
A data communications technology that routes whole messages to their destination one hop at a time
Developed in 1961, evolved into packet switching
Message switching today is more likely to be known as store-and-forward
Example: is a store-and-forward technology

10. Virtual Circuit Switching
An attempt to keep the efficiency of circuit switched technology while taking advantage of the flexibility allowed by packet switched technology

11. How Virtual Circuit Switched Communications Work
A communications link is established between two points in a larger network such as the Internet
Data to communicate is broken into discreet packets, like in packet switching
Once link is established and the data broken into packets, data packets are sent to destination computer using the pre-established communications path

12. How Virtual Circuit Switched Communications Work

13. WAN networks use different types of media to transmit data
Transmission Media
WAN networks use different types of media to transmit data
Some media used for WAN data transmissions are similar to those used for LAN data transmissions but implementation differs
Examples: Copper wires, fiber-optic cables, radio frequency (RF) signals

14. Oldest network transmission media used
Copper Cables
Oldest network transmission media used
Electricity pulses down a copper wire to transmit network communications
Copper has largely been replaced by other media in WAN environments
Copper media still used in last segment leading to the LAN
Example: Digital subscriber line (DSL) coming into homes and small businesses

15. Fiber-Optic Cables
Dominant transmission media used in WAN environments
Very small hollow glass tubes with a reflective coating
Reflect pulses of light down the tube as a means of transmitting network communications

16. Fiber-Optic Cables – Two Modes
Single-mode fiber
Thinner than multimode fiber
Carries very compact light pulses
Is generally baseband and can carry signals much farther than multimode fiber
Multimode fiber
Carries less compact pulses of light
Can carry broadband signals
Usually used for shorter range applications

17. Passive Optical Network (PON)
Point-to-multipoint fiber optics network
Signal from once source goes out to multiple end points
When going downstream from the central office, signal is broadcast to all destinations the fiber optic cable goes to
Encryption is often used to ensure privacy

18. Dense Wavelength Division Multiplexing (DWDM)
A type of multiplexing that uses wavelength to place more data on a cable rather than time segments
Assigns different signals to different wavelengths of light
Because DWDM transmits multiple wavelengths of light at the same time, increasing bandwidth of fiber-optic cable, ATM and SONET can use DWDM

19. Microwaves
A form of wireless communications seen in WAN environments
Use the electromagnetic spectrum between the frequencies of 300 MHz and 300 GHz
Range covers RF wireless technologies like Wi-Fi, Bluetooth, and cellular technologies
Microwave communications used in WANs usually involve a point-to-point wireless technology

20. Worldwide Interoperability for Microwave Access (WiMAX)
A wireless communications standard that uses microwaves
Most current version of WiMAX is IEEE m
Data rates
Up to 40 megabits per second on mobile platforms
Up to 1 gigabit per second on fixed platforms

21. Worldwide Interoperability for Microwave Access (WiMAX) (Continued)
Has a maximum fixed platform range of 30 miles and a maximum mobile platform range of 3 to 5 miles
LTE, Long Term Evolution, is a WiMAX alternative

22. Communications are a variation on microwave communications
Satellites
Communications are a variation on microwave communications
Ground stations and satellites themselves use microwave signals to communicate
Ground station communicates to one or more satellites in orbit
Satellites relay communications to a different ground station (no line of sight of original ground station) or another satellite in orbit within line of sight

23. Ideal position for seeing largest area is geosynchronous orbit (GEO)
Satellite Orbits
Depending on how high up a satellite orbits, can have lesser or greater line of sight
Ideal position for seeing largest area is geosynchronous orbit (GEO)
Are not able to be reached by ground stations in higher latitudes
Molniya orbit designed to cover locations in far northern regions

24. Molniya Orbit

25. Primary Orbits in Use for Satellite Communications Networks

26. Legend for Primary Orbits in Use for Satellite Communications Networks Image

27. Radio Frequency (RF)
Cellular networks are the most common form of radio frequency WAN media
Today’s cell tower usually has three directional antennas pointed 120 degrees away from each other
Allows full coverage in a circle around the tower while pushing the range of the tower out farther
Cells are generally represented as hexagons

28. Cellular Network and Channels

29. Cellular
A radio frequency based communications network spread over a large land area
Cellular network is made up of individual transceiver points that slightly overlap the range of other transceiver points adjacent to it
Most well-known cellular network is mobile phone or cell phone network

30. Cellular Technologies
LTE (Long Term Evolution)
LTE Advanced
High Speed Packet Access (HSPA)
HSPA+

31. One of the oldest WAN network communication technologies available
Dial-up
One of the oldest WAN network communication technologies available
Dial-up works by using a modem to connect a computer to a plain old telephone service (POTS)
Methods to work around speed limitations:
V.44 compression
Server-side compression

32. Public Switched Telephone Network (PSTN)
The entire worldwide telephone network
Demarc point: Where service provider comes into a local home or business
Last mile: From the demarc point to the remote switching facility
Central office: Where remote switching facility boxes terminate
Local loop: From a customer’s demarc to the central office
Remote switching facility is green or silver box located in neighborhood or underground

33. The Last Mile and the Local Loop

34. Integrated Services Digital Network (ISDN)
A set of standards designed to carry voice, video, data, and other services in a digital format over the PSTN
Uses circuit switching to establish, maintain, and release connections
Allows access to packet switched networks
ISDN’s advantage over dial-up is that it is able to integrate voice and data over the same lines

35. Basic Configuration of an ISDN Networked Device

36. Integrated Services Digital Network-Basic Rate Interface (ISDN-BRI)
An entry-level version of ISDN and is the most commonly used version
Achieves upstream and downstream data rates by bonding to 64 kbps channels
B channels known as bearer channels
One 16 kbps signaling channel called a delta channel or a D channel
Carries the Q.931 protocol

37. ISDN-Primary Rate Interface (ISDN-PRI)
Similar to ISDN-BRI except it has more than two B channels bonded together
D channel for ISDN-PRI has a throughput of 64 kbps instead of 16 kbps
In the United States, ISDN-PRI commonly carried over a T-1 line of mbps

38. Digital Subscriber Line (DSL) Technologies
Uses the PSTN
Uses a higher frequency than voice communications to carry data
Phone systems that support DSL also need a special terminal adapter on the customer end

39. Asymmetric Digital Subscriber Line (ADSL)
Provides a different data throughput for upstream communications than for downstream
Depending on ADSL standard being used, downstream transmission rates can range from 1.5 mbps to 12.0 mbps
Upstream transmission rates range from .5 mbps to 1.8 mbps
Upstream communications refer to communications that go from the consumer or end user up to the ISP or server
Downstream communications refer to communications down to the consumer or end user

40. High-Bit-Rate Digital Subscriber Line (HDSL)
Developed to use twisted-pair copper
Can carry both voice and data
Uses T-1 lines and is often used to interconnect local carriers
When used to interconnect local carriers, repeaters are placed every 1.2 miles or so

41. Very-High-Bit-Rate Digital Subscriber Line (VDSL)
Can provide very high data transfer rates
Up to 52 mbps downstream rates and up to 16 mbps upstream
VDSL standard first approved in 2001, updated and improved in 2006
In the United States, AT&T, Verizon, and Qwest offer VDSL in some areas

42. Broadband and Cable Modems
A technology used by cable companies to provide data communications capabilities for customers
In a more technical sense, refers to any technology that sends more than one signal over the same communications media

43. X.25
A technology developed in the 1970s as a means to use packet switched communications in a WAN environment
Not as widely used today; replaced by newer alternatives
Originally designed as an analog technology
Performs error checking on the packets it passes through

44. Example of a Stylized X.25 Network

45. Frame Relay
WAN service designed to connect two points that require only intermittent communications
Gives the impression of a dedicated line like a T1 to end user without the associated cost

46. How Frame Relay Works

47. T-Lines
Group of technologies that use digital multiplexing in telecommunications
Are distinctive from other telecommunications technologies because they are made up of a number of smaller channels, created by multiplexing.
Multiplexing creates smaller channels; one media cable can carry multiple channels

48. Smaller channels, or sub-channels, are 64 kbps in bandwidth
T-Lines (Continued)
Smaller channels, or sub-channels, are 64 kbps in bandwidth
T-Lines come in several different levels:
Fractional T-Lines, T1, T1C, T2, T3, T4, and T5
Most commonly used levels are T1, T3, and T5

49. T-Line Levels and Specifications

50. Asynchronous Transfer Mode (ATM)
A multiplexing technique that uses time slots to break a communications signal into different channels
Differs from conventional time division multiplexing, which breaks a signal into a set number of channels at all times without regard to whether the channels are actually being used in any given time slot
ATM only breaks the signals into the number of time slots needed

51. UNI ATM Cell

52. Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH)
Multiplexing protocols used to transfer multiple digital bit streams, also called channels, over fiber-optic cables using either lasers or LED (light emitting diodes)
Both can send multiple digital bit streams over copper wires at data rates slower than those possible with fiber optic
SONET and SDH are essentially the same; SONET used in the United States and Canada, rest of world uses SDH

53. SONET OC Levels and Associated Frame Formats and Data Rates

54. Multiprotocol Label Switching (MPLS)
Purpose is to speed up the movement of data across a larger network
Adds a label to a group of packets that need to be passed on to a specific destination
Number of hops needed to reach destination is listed on label, added by MPLS
Speeds up transmission because it bypasses the need for router to determine next hop for each packet as it arrives

55. Remote Access Services (RAS)
A group of technologies used to facilitate remote access to a computer network
Most RAS technologies are software based
Citrix is an example of RAS
Must set up a RAS server and a RAS client on the client end

56. Virtual Private Network (VPN)
A technology commonly used by corporations to allow users to gain secure remote access to corporate servers
Can use the Internet to establish connections
Field workers can effectively gain access to corporate network anywhere they can get access to the Internet

57. Summary
Circuit switching is a type of communications that establishes a dedicated communications channel for the duration of a given transmission.
Packet switching is a network communications technology that only opens up connections long enough for a small data packet to move from one network segment to another.
Virtual circuit switching is an attempt to keep the efficiency of circuit switched technology while taking advantage of the flexibility allowed by packet switched technology.

58. Summary (Continued)
WAN networks can use copper wires, fiber-optic cables, and radio frequency (RF) signals.
WAN technologies are widely diverse and include microwaves and WiMAX to cellular technologies to Frame Relay.