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Connecting
to the Network
Valašské Meziříčí 25. 5. 2017
© 2007 Cisco Systems, Inc. All rights reserved.
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Objectives
 Concept of networking
 Benefits of networks
 Communication protocols
 Local Ethernet network
 Access layer devices
 Distribution layer devices
Valašské Meziříčí 25. 5. 2017
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Networking and Its Benefits
 Types of networks
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Networking and Its Benefits
 Examples of small, medium and large networks
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Networking and Its Benefits
 Components of an Information network
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Networking and Its Benefits
Roles of computers on a network:
 Clients and servers
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Networking and Its Benefits
 Computer peer-to-peer network
Equal peer nodes function as both "clients" and "servers”.
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Networking and Its Benefits
 Computer peer-to-peer network
Advantages
• Easy to set up
• Simple
• Low cost
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Networking and Its Benefits
 Computer peer-to-peer network
Disadvantages
•
•
•
•
Difficult to administer
Less secure
Not scalable
Slow: All devices both
clients and servers
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Network Topologies
 Logical and physical topologies
Physical topology:
Where the devices are
located.
hubs
routers
servers
switches
computers
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Network Topologies
 Logical and physical topologies
Logical
topology:
How devices
communicate
with one
another.
Shows names,
addresses,
applications.
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Communication Protocols
Communication: source, channel, destination
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Communication Protocols
 Protocols = Set of Rules
When?
How long?
Uni- , Multi-, Broad-cast?
Sound, Light, Electricity?
What box, paper?
What paragraphs?
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Communication Protocols
 Encoding in human communication
What has he
decoded?
What is she
dreaming
about?
Bad encoding - decoding...
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Communication Protocols
 Timing and access methods
Calling ...
... sleeping.
Bad timing ...
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Communication Protocols
 Message patterns
Multicast
Unicast
Broadcast
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Communication Protocols
Human communications:
 messages
 unit sizes
 timing
 encapsulation
 encoding
 message patterns
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“Protocol”
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Local Ethernet Network
People must share
common languages
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 Devices on a network must
share common protocols
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Local Ethernet Network
 Standardization in computer communication protocols
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Local Ethernet Network
 Physical addressing: MAC addresses
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Local Ethernet Network
 Hierarchical design in an Ethernet Network
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Local Ethernet Network
 The logical network address: IP address
Which
host?
Which network?
Network address
Host addresss
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Access Layer Devices
 The function of a Hub
1 source, ...
... 1 destination, ...
... but all devices receive all messages.
Only one communication at a time.
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Access Layer Devices
 The function of a Hub
2 sources sending at
the same time ...
... collision !!!
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Access Layer Devices
 The function of switches
Switch learns
MAC addresses
and sends
messages only to
the right
destination.
Many communications at a time.
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Distribution Layer Devices
 The function of routers
•
•
•
•
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Packets forwarding
Packets filtering
Logical grouping of devices
Joining – separating networks
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Distribution Layer Devices
 Default gateway
192.168.1.1
192.168.1.3
aa.aa.aa.33.33.33
Inside a single network the computers know each other‘s
addresses – no problem to communicate.
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Distribution Layer Devices
 Default gateway
192.168.1.1
192.168.1.3
aa.aa.aa.33.33.33
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But if they want to send a packet outside their
own network, they need somebody, who
knows the way.
They need the Default gateway.
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Summary






Networks carry data.
Hosts can be clients, servers, or both.
All communication needs a source, destination, and channel.
Protocols are sets of rules.
Protocols govern computer communications.
Each network host needs
• physical MAC address
• logical IP address.
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