Client Remote Access Technologies

1
Chapter 7

• Client Remote Access Technologies

2
Remote Access Methods 1970s

• Information Age
• Efforts focused on delivering access to mainframe
• Access applications and share remote printers
• Client side used dial up connections with PCs
• Computer used terminal emulation  
• Modem pools used with Terminal Servers
• Modem speed limited transmissions

3
Remote Access Methods
4
Remote Access Methods - 1980s

• Growth of client/server LAN technology
• Required more people to connect
• Need for simultaneous connections increases
• New technology emerged in line/modem cards
• Increase in digital circuitry and digital modems
• Transmission rates move up to 1.54 Mbps.

5
Remote Access Methods - 1990s

• Development of Internet-based operations
• Interconnected powerful information servers
• Increase in DSL and Cable Modems
• Explosion of Internet Email systems
• Security Intrusion and Firewall Protection

6
Remote Access to Internet

• Internet Servers
• Connected via routers to support PPP and IP
  access
• Access concentrators route local IP traffic
• Security concerns increase
• Use of RADIUS servers for authentication.
• Data rates increase
• 384 Kbps- home users
• 45 Mbps. branch office connections

7
Access Mobile Switches

• ISP and Telco carrier service facility growth
• Access switches racked to handle Internet traffic
• 5,000 to 10,000 calls per rack increase
• Support for joint dial up and broadband DSL
• Mobile Access
• Enhanced information services
• Multiple sources for travelers
• Security concerns for remote dial-up or DSL

8
Dial Up Access

• Process connecting remote users to corporate LAN
• Use of Modems, Servers, and Client connections
• Establishing connectivity for remote users
• Dial-up through POTS
• Specified connection telephone lines
• Connection through ISP or subscription service

9
Dial Up

• Remote users dial up over the Plain Old Telephone
  Service (POTS) to connect to corporate
  applications.
• A modem is used to establish a remote session.
• Many corporations provide phone numbers for users
  to dial into and provide access to specific
  servers. Others allow access through an ISP or a
  subscription service like CompuServe.

10
Dial Up Access
11
Terminal Emulation

• Most common method for remote dial up access
• Software is installed on PC
• Allows PC to emulate IBM or VAX terminal
• Remote user connects to mainframe as though they
  were directly attached
• works for host-based asynchronous applications

12
Remote Node

• Used for most standard connections
• Connects remote computer as if it were a node
• Remote control is used for data entry
• Dial up connection speed limited to 56 Kbps

13
Remote Control Process

• Enables remote user to take control of host PC
  residing on corporate network
• Calling PC sends keystrokes and mouse cursor
  movements
• Remote connection provides access to the host PC
• LAN provides access to application running on
  fileserver
• LAN returns screen images of application to
  remote PC
• Applications programs run on host -- data files
  stay on LAN

14
Remote Access Methods
15
DSL Technology

• Delivers broadband services to homes and small
  businesses
• Supports high-bandwidth applications
• Internet access, telecommuting, streaming media
• Uses existing phone line for high speed linkage
• Gives always on Internet access
• DSL is a transport service
• Moves computer data traffic
• Functions at high data transfer rates

16
DSL Connection
17
DSL LAN Connection

• User has dedicated LAN-like connection
• Signal is multiplexed and sent to ISP provider
• Speeds vary from 144 Kbps. to 1.5 Mbps
• 25 times faster than standard dial-up connection
• Services the local loop called last mile
• Distance from user to CO determines speed
• Signal is Asymmetrical - download speed faster

18
ADSL Transmission

• Modems divide bandwidth of phone lines
• Frequency-division multiplexing (FDM)
• Echo cancellation
• FDM
• Assigns one band for upstream/one for downstream
  data
• Downstream path divided by time division
  multiplexing (TDM)
• One or more high or low speed channels used
• Frequencies below 4 KHz for voice - above 4 KHz
  for data

19
ADSL Transmission Rates

• Uses advanced digital signal processing
• Requires systemwide equipment upgrades
• New digital analog filters and A/D) converters
• Provides significant transmission rate
  improvements
• 1.5 Mbps to 9 Mbps downstream
• 16 Kbps to 800 Kbps upstream

20
xDSL Types

• SDSL - Symmetrical High-Speed DSL
• Allows maximum data rate of 2.3 Mbps. both
  directions
• IDSL Integrated Services DSL
• IDSN and DSL service combined for data-only
  service
• IDSL transmits faster than standard ISDN
• Speeds reach 144 Bps and bypasses CO voice
  network
• IDSL is dedicated

21
xDSL Types (cont.)

• HDSL-2 High Rate DSL
• Supports voice, data, and video
• Uses ATM, Frame Relay, and T1 connections
• Symmetrical operations
• Transmission rates up to 1.5 Mbps
• Limited to 12,000 feet
• VDSL Very High Bit-Rate DSL
• High speed data transmission on existing phone
  lines
• Downstream speeds up to 55 Mbps
• Upstream channel speeds 1.6 to 2.3 Mbps

22
VDSL and ONU

• VDSL designed for high bandwidth signals over
  short distances
• Range of 1,000 to 6,000 feet from CO
• Shorter distances have higher connection rates
• VDSL connects to optical network units (ONUs)
• ONU connects directly to central office (CO) main
  fiber network backbone
• VDSL Silicon adapter circuitry very expensive
• No specifications for mass-producing VDSL silicon

23
Quote of the Day

• Before you contradict an old man, my fair friend,
  you should endeavor to understand him.
• George Santayana