Transcript Data Network Connectivity

Data Network
Connectivity
Chapter 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 two 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.