Network hardware 2

Introduction To Networking

Networking Hardware

Slide 1

Networking Hardware

• NICs
• Repeaters and Hubs
• Switches
• Routers
• Network Example

Copyright(c)2006, Groove Systems. All Rights Reserved. Slide 2

NICs

• Network interface cards (also called NICs, network adapters,
or network cards) are connectivity devices that enable a
workstation, server, printer, or other node to receive and
transmit data over the network media
• Nearly all NICs contain a data transceiver, the device that
transmits and receives data signals
• NICs belong to both the Physical layer and Data Link layer of
the OSI Model, because they apply data signals to the wire and
assemble or disassemble data frames
• In addition, they perform the routines that determine which
node has the right to transmit data over a network at any
given instant


NICs


Repeaters and Hubs

Slide 6

Repeaters and Hubs

• Repeaters operate in the Physical layer of the OSI
Model and, therefore, have no means to interpret
the data they retransmit
• They simply regenerate a signal over an entire segment
• A repeater contains one input port and one output
port, so it is capable only of receiving and repeating
a data stream
• Repeaters are suited only to bus topology networks
• The advantage to using a repeater is that it allows
you to extend a network inexpensively


Repeaters and Hubs

• A hub is a repeater with more than one output port
• A hub typically contains multiple data ports into
which the patch cables for network nodes are
connected
• A hub accepts signals from a transmitting node and
repeats those signals to all other connected nodes
in a broadcast fashion


Repeaters and Hubs

• All devices connected to a hub share the same
amount of bandwidth and the same collision domain
• A collision domain is a logically or physically
distinct Ethernet network segment on which all
participating devices must detect and accommodate
data collisions
• The more nodes participating in the same collision
domain, the higher the likelihood of transmission
errors and slower performance


Switches

• Switches are connectivity devices that subdivide a
network into smaller logical pieces, or segments
• Switches operate at the Data Link layer of the OSI
Model, while more modern switches can operate at
Layer 3 or even Layer 4
• Switches interpret MAC address information


Switches

• Because they have multiple ports, switches can
make better use of limited bandwidth
• Each device connected to a switch effectively
receives its own dedicated channel to the switch
• From the Ethernet perspective, each dedicated
channel represents a collision domain
• Because a switch limits the number of devices in a collision
domain, it limits the potential for collisions
• By their nature switches provide better security
than many other devices because they isolate one
device's traffic from other devices' traffic


Switches

• Connecting a workstation to a switch


Switches

• A switch on a small network


Switches

• Switches differ in the method of switching they
use:
1. Cut-through mode
2. Store and forward mode
• Cut-Through Mode
• A switch running in cut-through mode reads a frame's
header and decides where to forward the data before it
receives the entire packet
• What if the frame becomes corrupt? Because the cut-
through mode does not allow the switch to read the frame
check sequence (FCS) before it begins transmitting, it can't
verify data integrity in that way


Switches

• Store and Forward Mode
• In store and forward mode, a switch reads the entire
data frame into its memory and checks it for accuracy
before transmitting the information
• Although this method is more time-consuming than the cut-
through method, it allows store and forward switches to
transmit data more accurately
• Store and forward mode switches are more appropriate for
larger LAN environments, because they do not propagate
data errors


Routers

• A router is a multiport connectivity device that
directs data between nodes on a network
• Routers can integrate LANs and WANs running at
different transmission speeds and using a variety of
protocols
• when a router receives an incoming packet, it reads
the packet's logical addressing information
• Based on this, it determines to which network the packet
must be delivered
• Then it determines the shortest path to that network
• Finally it forwards the packet to the next hop in that path


Routers

• A router's strength lies in its intelligence
• Not only can routers keep track of the locations of
certain nodes on the network, as switches can, but
they can also determine the shortest, fastest path
between two nodes
• For this reason, and because they can connect
dissimilar network types, routers are powerful,
indispensable devices on large LANs and WANs
• The Internet, for example, relies on a multitude of
routers across the world


Routers

• A typical router has an internal processor, an
operating system, memory, input and output jacks
for different types of network connectors
(depending on the network type), and, usually, a
management console interface


Network Example


Network hardware 2

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