Introduction to Networking
What is a Network?What is a Network?
A network consists of 2 or more computers connected
together, and they can communicate and share
resources (e.g. information)
Why Networking?Why Networking?
Sharing information — i.e. data communication
Do you prefer these?
• Or this?
HowHow many kinds of Networks?many kinds of Networks?
• Depending on one’s perspective, we can classify
networks in different ways
• Based on transmission media: Wired (UTP, coaxial
cables, fiber-optic cables) and Wireless
• Based on network size: LAN and WAN (and MAN)
• Based on management method: Peer-to-peer and
• Based on topology (connectivity): Bus, Star, Ring
Acts on the physical layer
Operate on bits rather than frames
Multiple Hubs can be used to extend the network
Regenerate the network’s signal and resend them to
Features & LimitationsFeatures & Limitations
• Can connect different types of media
• The most economic way of expanding networks
• Cannot join segments with
different access methods (e.g.
CSMA/CD and token passing)
• cannot filter network traffic
• cannot determine best path
• Used to boost the signal between two cable segments
or wireless access points.
Repeaters clean, amplify, and resend signals that are
weakened by long cable length.
• Resides on Layer 1 of the OSI model.
• Connects two LANs and forwards or filters data
packets between them.
• Forward data depending on the Hardware (MAC)
address, not the Network address (IP).
• The purpose is to filter traffic on a LAN, to keep
local traffic local, yet allow connectivity to other
segments of the network.
• Resides on Layer 2 of the OSI model.
Differences Between Bridges andDifferences Between Bridges and
OSI layer Physical layer Data link layer
Regenerate data at
the signal level
at the packet
Switches operate at the Data Link layer (layer 2) of the OSI
• Split large networks into small segments, decreasing the
number of users sharing the same network resources and
Each channel has its own capacity and need not be shared
with other channels
• Connects any number of LANs.
• Uses standardized protocols to move packets
efficiently to their destination.
• More sophisticated than bridges, connecting
networks of different types (for example, star and
• Forwards data depending on the Network address
(IP), not the Hardware (MAC) address.
• Used routing tables to determine the best path for
Joining together two networks that use different base
Implemented completely in software, completely in
hardware, or as a combination of both.
Gateways operate at the any layer of the OSI model.
Also called protocol converters.
Devices and the layers at whichDevices and the layers at which
They operateThey operate
Layer Name of Layer Device
3 Network Routers, layer 3
2 Data Link Switches,
1 Physical Hubs
• Repeaters are the least expensive way to expand a
network, but they are limited to connecting two
• Bridges function similar to repeaters, but can
understand the node addresses
• Switches can be considered as multiport bridges,
can divide a network into some logical channels
• Routers interconnect networks and provide
filtering functions. They can determine the best
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