WAN Technologies Lesson 8

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

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

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

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.

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

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

How Packet Switching Works

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: E-mail is a store-and-forward technology

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

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

How Virtual Circuit Switched Communications Work

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

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

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

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

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

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

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

Worldwide Interoperability for Microwave Access (WiMAX) A wireless communications standard that uses microwaves Most current version of WiMAX is IEEE 802.16m Data rates Up to 40 megabits per second on mobile platforms Up to 1 gigabit per second on fixed platforms

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

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

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

Molniya Orbit

Primary Orbits in Use for Satellite Communications Networks

Legend for Primary Orbits in Use for Satellite Communications Networks Image

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

Cellular Network and Channels

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

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

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

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

The Last Mile and the Local Loop

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

Basic Configuration of an ISDN Networked Device

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

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 1.544 mbps

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

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

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

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

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

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

Example of a Stylized X.25 Network

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

How Frame Relay Works

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

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

T-Line Levels and Specifications

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

UNI ATM Cell

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

SONET OC Levels and Associated Frame Formats and Data Rates

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

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

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

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.

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.