Chapter 06 teleworker services

Chapter 6: Teleworker Services
CCNA Exploration 4.0
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Objectives
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Describe the enterprise requirements for providing
teleworker services, including the differences between
private and public network infrastructures.
•
Describe the teleworker requirements and recommended
architecture for providing teleworking services.
•
Explain how broadband services extend enterprise networks
using DSL, cable, and wireless technology.
•
Describe the importance of VPN technology, including its
role and benefits for enterprises and teleworkers.
•
Describe how VPN technology can be used to provide
secure teleworker services to an enterprise network.
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Business Requirements for
Teleworker Services
4
•
More and more companies are finding it beneficial to have
teleworkers.
The Business Requirements for Teleworker
Services
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The Teleworker Solution

•
Organizations need secure, reliable, and cost-effective
networks to connect corporate headquarters, branch offices,
and suppliers.
•
Three remote connection technologies available to
organizations for supporting teleworker services:
–
Traditional private WAN Layer 2 technologies, including
Frame Relay, ATM, and leased lines, provide many
remote connection solutions. The security of these
connections depends on the service provider.
–
IPsec Virtual Private Networks (VPNs) offer flexible and
scalable connectivity.
–
Site-to-site connections can provide a secure, fast, and
reliable remote connection to teleworkers.
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The Teleworker Solution
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Teleworker Solution Components
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Broadband Services
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Connecting Teleworkers to the WAN
•
Teleworkers typically use diverse applications (for example,
e-mail, web-based applications, mission-critical applications,
real-time collaboration, voice, video, and videoconferencing)

that require a high-bandwidth connection.
•
The choice of access network technology and the need to
ensure suitable bandwidth are the first considerations to
address when connecting teleworkers.
•
Dialup access
–
An inexpensive option that uses any phone line and a
modem. To connect to the ISP, a user calls the ISP
access phone number.
–
Dialup is the slowest connection option, and is typically
used by mobile workers in areas where higher speed
connection options are not available.
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Connecting Teleworkers to the WAN
DSL
•
Also uses telephone lines, more expensive than dialup, but
provides a faster connection.
•
Provides a continuous connection to the Internet.
•
Uses a special high-speed modem that separates the DSL
signal from the telephone signal and provides an Ethernet
connection to a host computer or LAN.
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Connecting Teleworkers to the WAN
Satellite

•
Offered by satellite service providers.
•
The computer connects through Ethernet to a satellite
modem that transmits radio signals to the nearest point of
presence (POP) within the satellite network.
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Connecting Teleworkers to the WAN
Cable modem
•
Offered by cable television service providers. The Internet
signal is carried on the same coaxial cable that delivers
cable television. A special cable modem separates the
Internet signal from the other signals carried on the cable
and provides an Ethernet connection to a host computer or
LAN.
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Cable
•
Accessing the Internet through a cable network is a popular
option used by teleworkers to access their enterprise
network.
•
The cable system uses a coaxial cable that carries radio
frequency (RF) signals across the network. Coaxial cable is
the primary medium used to build cable TV systems.
•
CATV originally meant “community antenna television.” This
form of transmission shared TV signals
•

Cable systems were originally built to extend the reach of TV
signals and improve over-the-air TV reception
•
Modem cable systems use fiber and coaxial cable for signal
transmission
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What is a Cable System
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What is a Cable System
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Sending Digital Signals over Radio Waves
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Cable
•
The Data-over-Cable Service Interface Specification
(DOCSIS) is a standard for certification of cable equipment
vendor devices (cable modem and cable modem termination
system).
•
DOCSIS specifies the physical and MAC layers.
–
Physical layer: DOCSIS specifies the channel widths
–
MAC layer - Defines a deterministic access method,
TDMA or S-CDMA.
•
DOCSIS defines RF interface requirements for a data-over-
cable system.
•
Cable equipment vendors must pass certification conducted

by CableLabs.
•
Euro-DOCSIS is a variation adapted for use in Europe.
About DOCSIS: />About Euro-DOCSIS:
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Sending Data over Cable
•
Delivering services over a cable network requires different radio
frequencies. Downstream frequencies are in the 50 to 860 MHz range,
and the upstream frequencies are in the 5 to 42 MHz range.
•
Two types of equipment are required to send digital modem signals
upstream and downstream on a cable system:
–
Cable modem termination system (CMTS) at the headend of the
cable operator
–
Cable modem (CM) on the subscriber end
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Sending Data over Cable
•
CMTS (Cable Modem Termination System): is a component
that exchanges digital signals with cable modems on a cable
network. A headend CMTS communicates with CMs that are
located in subscriber homes.
•
CM (Cable Modem): enables you to receive data at high
speeds. Typically, the cable modem attaches to a standard
10BASE-T Ethernet card in the computer.
•

Fiber: The trunk portion of the cable network is usually fiber
optic cable.
•
Node: converts optical signals to RF signals
•
Distribution Area (feeder segment) is from 500 to as many
as 2000 subscribers
•
Coaxial cable: coaxial feeder cables originate from the note
and carry RF signals to the subscriber.
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DSL
•
Is a means of providing high-speed connections over
installed copper wires.
•
Uses high transmission frequencies (up to 1 MHz).
•
Technology for delivering high bandwidth over regular
copper lines.
•
Connection between subscriber and CO, less than 5.5
kilometers (3.5 miles).
•
The two basic types of DSL technologies are asymmetric
(ADSL) and symmetric (SDSL).
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DSL
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DSL

•
The connection is set up between a pair of modems on
either end of a copper wire that extends between the CPE
and the DSL access multiplexer (DSLAM).
•
The two key components are the DSL transceiver and the
DSLAM:
–
Transceiver: Connects the computer of the teleworker to
the DSL. Usually is a DSL modem connected to the
computer using a USB or Ethernet cable. Newer DSL
transceivers can be built into small routers with multiple
10/100 switch ports suitable for home office use.
–
DSLAM: Located at the CO of the carrier, the DSLAM
combines individual DSL connections from users into one
high-capacity link to an ISP, and thereby, to the Internet.
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DSL
•
The advantage that DSL has over cable technology is that
DSL is not a shared medium. Each user has a separate
direct connection to the DSLAM. Adding users does not
impede performance, unless the DSLAM Internet connection
to the ISP, or the Internet, becomes saturated.
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ADSL
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A key feature of ADSL is coexistence with POTS.
•

Transmission of voice and data signals is performed on the
same wire pair.
•
Data circuits are offloaded from the voice switch.
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ADSL
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A microfilter is a passive low-
pass filter with two ends.