Download ch 11 Data Network Connectivity

Data Network
Connectivity
11
Objectives
In this chapter, you will learn to:
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Explain how NICs operate
List the most common types of NICs
Describe the purpose and operation of hubs and repeaters
Describe the purpose and operation of bridges and switches
Explain how routers connect dissimilar networks
Identify other Layer 3 connectivity devices and understand their
uses
Describe how remote users can connect to a LAN or WAN via a
modem
Identify the components necessary for access and carrier
network connectivity
Network Interface Cards (NICs)
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Devices that act as transceivers for workstations, servers,
connectivity devices, and peripherals on a network.
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Transmit data in a format that other network nodes can interpret.
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Receive and interpret encoded data from the network.
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Assemble data frames during transmission and disassemble data
frames during reception.
Adapter Card NICs
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A circuit board used to connect a device to the system
board.
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Expansion slots - openings with multiple electrical
contacts into which the adapter can be inserted.
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Bus - the circuit that is used by the system board to
transmit data to the computer’s components.
Adapter Card NICs
PC Card NICs
USB NICs
Hubs
Hubs
Hubs
Bridges
Bridges
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Transparent bridging - a bridge begins polling a network to learn
about its physical topology as soon as it is installed on the network.
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Spanning tree algorithm - a routine that can detect circular traffic
patterns and modify the way multiple bridges work together, thus
eliminating such patterns.
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Source-route bridging - a bridge polls the network to determine which
path is best for a packet to travel from point A to point B.
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Translational bridging - the bridge not only forwards packets, but also
translates packets between one logical topology and another.
Data Switches
Data Switches
Disadvantages
Advantages
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Switches offer greater
security because they isolate
one device’s traffic from
another.
They provide separate
channels for every device
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Switches can become
overwhelmed by
continuous, heavy traffic.
In that event, they cannot
prevent data loss.
On a fully switched
network, in which every
node uses its own port on
the switch and therefore
provides separate data
channel, devices cannot
detect collisions.
Routers
Routers
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Functions:
 Filter out broadcast transmissions to alleviate network congestion
 Prevent certain types of traffic from getting to a network, enabling
customized segregation and security
 Support simultaneous local and remote connectivity
 Provide higher network fault tolerance through redundant
components, such as power supplies or network interfaces
 Monitor network traffic and issue statistics to a database
 Diagnose internal or other connectivity problems and trigger
alarms
Routers
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Static routing - a technique in which a network
administrator programs a router to use specific paths
between nodes.
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Dynamic routing - automatically calculates the best
path between two nodes and accumulates this
information in a routing table.
Routers
Routing Protocols
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Best path - the most efficient route from one node on a network to
another.
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Routing protocols - to determine the best path, routers
communicate with each other through routing protocols.
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Convergence time - the time it takes for a router to recognize a
best path in the event of a change or outage.
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Bandwidth overhead - the burden placed on the underlying
network to support the routing protocol.
Routing Protocols
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Routing Information Protocol (RIP) for IP and IPX - factors in only the
number of of hops between nodes when determining a path from one
point to another.
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Open Shortest Path First (OSPF) for IP - uses more complex algorithm
for determining best paths.
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Enhanced Interior Gateway Routing Protocol (EIGRP) for IP, IPX, and
AppleTalk - offers the benefits of supporting multiple protocols and
limiting unnecessary network traffic between routers.
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Border Gateway Protocol (BGP) for IP - the routing protocol for Internet
backbones.
Firewalls
Gateways
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Combinations of networking hardware and software that
connects at least two dissimilar kinds of networks.
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Operate at multiple layers of the OSI model
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Can run on servers, workstations, or mainframe
computers
Gateway
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Categories:
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E-mail gateway - translates messages from one type of e-mail
system to another.
Internet gateway - allows and manages access between LANs
and the Internet.
LAN gateway - allows segments of a LAN running different
protocols, network access methods, or transmission types to
communicate with each other.
Voice/data gateway - allows a data network to issue data
signals over a voice network.
Wireless gateway - integrates a wireline network with a
wireless network.
Gateway
Remote Connection Methods
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Direct dial to a remote access server - the client uses a dial-in
software supplied with its operating system to connect to a remote
access server on the LAN.
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Direct dial to a host workstation - the remote client uses a dial-in
software supplied with its operating system to connect to a
workstation that is directly attached to the LAN.
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Connect via the Internet - the client first connects to the Internet
then connects to a private network.
Remote Connection Methods
How Modems Work
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Data compression:
 to obtain higher throughput, modems compress the data they
receive from a computer before transmitting it.
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Data Transfer Rates:
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V.90 defines 56 Kbps, asymmetrical transmission in which one of the
modems is assumed to be using a digital line.
V.92 improves upon V.90 by increasing the upstream transmission rate
to a maximum of 48 Kbps.
V.92 also accomplishes faster session negotiation because modems
using this standard keep a record of previous connections.
Flow Control and Buffering
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Software flow control (Xon/Xoff) - flow control information is
issued over the same channel as the data being sent.
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Hardware flow control - separates flow control information
from the data being sent.
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Buffer - a logically defined area of a computer’s memory where
data is temporarily stored until it is requested by software, or
until it is cleared.
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Buffering - the process of issuing data to a buffer.
Asynchronous and Synchronous
communication
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Asynchronous - refers to a communications method
in which data being transmitted and received by nodes
does not have to conform to any predetermined timing
schemes.
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Synchronous - refers to a communications method in
which data is transmitted in a continuous stream of
bits.
Modem Types
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Adapter card - modems can exist as an adapter card that connects
to a computer’s bus.
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Serial port - traditionally, external modems connected to a
computer via the serial port, which accepts a 22-pin, RS 232 data
connector.
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PC Card - an excellent alternative for laptop users.
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USB - an excellent option for both desktop and laptop computer
users.
Adapter Card
Serial Port
PC Card
USB
Virtual Private Networks
Digital Loop Carrier (DLC)
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A technique for delivering digital signals to a high volume of LEC
subscribers over a combination of new and old local loop
infrastructure.
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Uses multiplexing to consolidate multiple subscriber lines into
fewer, high-capacity digital connections that lead to the LEC’s
central office.
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The point at which lines are combined is called the remote
subscriber terminal.
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Central office terminal - separates individual subscriber lines into
their original circuits.
Digital Loop Carrier (DLC)
Access Nodes
The point at which a user’s traffic enters or exits a
carrier’s network.
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Digital cross-connect system (DCS) - a device that
directly connects multiple digital lines with other digital
lines.
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Integrated access devices (IADs) - integrate a
number of functions into one device.
Access Nodes
Summary
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NICs enable workstations and other nodes to connect
to a network.
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Gateways are combinations of software and hardware
that connect dissimilar networks or systems.
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A virtual private network (VPN) allows an organization
to carve a private WAN over public transmission
facilities.