4.1 Network Fundamentals
4.2 The Internet
Lecture 10: Networking and the Internet
Linked computer systems, in which
computers are connected so that data can be
transferred from machine to machine
Scope
Local area network (LAN)
Metropolitan area (MAN)
Wide area network (WAN)
Ownership
Closed versus open
Exchange messages & share resources
Printing capabilities
Software packages
Data storage facilities
Topology (configuration)
Ring
Bus
Star
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Rules by which network activities are
conducted.
When a machine can transmit its own
message
Token ring
Popular in ring networks
Possession of token provides right to introduce
new message
CSMA/CD (Carrier Sense, Multiple Access with
Collision Detection)
Used in bus topology networks
Silent bus provides right to introduce new
message
When a machine should forward messages it
receives
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• Each message is broadcast to all the machines on the bus.
• Token: a unique bit pattern.
• A machine can transmit its own message when holding the token, otherwise
forward messages
• Forward the token to next machine when it receives its own message.
• Each machine monitors all the messages but only keep those addressed to itself
• A machine can send a message if the bus is silent, at the same time it keeps
monitor the bus
• If it detects a collision, wait for a random period and transmit again.
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Repeater: Extends a network
Connects two buses to form a large long bus
Repeater simply pass signals between two original buses
Bridge: Connects two compatible networks
Connects two buses.
Look at the destination address that accompanies each
message.
Forward a message across the connection when the
destination is a computer on the other side.
Switch: Connect several compatible networks
A bridge with multiple connections
Router: Connects two incompatible networks resulting
in a network of networks called an internet
Example. Connect a ring network with a bus network
Router: a computer belongs to both networks. Forward a
message from one network into another network.
Look at the destination address, may receive a message in
one protocol and forward message to the other network using
another protocol.
Internet (uppercase I) : refers to a particular,
worldwide internet
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• Look at the destination address
• receive a message in one protocol and forward it in another protocol
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Summarize the distinction between a repeater and a
bridge
What is a router?
What is a protocol?
The Internet: An internet that spans the world
Original goal was to develop a means of
connecting networks that would not be disrupted
by local disasters.
Today it has shifted from an academic research
project to a commercial undertaking.
Describe the steps followed by a machine that wants
to transmit a message in a network using the
CSMA/CD protocol?
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Domain: A portion of the Internet that
network or internet controlled by a single
authority
Connected to the rest of the Internet (the cloud)
by a router called a gateway
Internet Corporation for Assigned Names &
Numbers (ICANN): Oversees the registration
of domains
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Internet Service Provider (ISP): Provides
connectivity to the Internet
Popular means of connecting:
Traditional telephone (dial up connection)
Cable connections
DSL
Wireless
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IP address: 32 bit identifier for a machine
(currently being expanded to a 128 bit
system)
Network identifier: Assigned by ICANN
Host address: Assigned by domain administrator
Dotted decimal notation: Common notation
for displaying IP addresses
Example: 192.207.177.133
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Mnemonic address made up of two parts:
Domain name
Assigned by a registrar
Example: aw.com
Top level domain: Classification of domain owner
By usage – Example: .com = commercial
By country – Example: .au = Australia
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Electronic Mail (email)
File Transfer Protocol (FTP)
Telnet and SSH
Subdomains and individual host names
Assigned by domain owner
Example: r2d2.compsci.nowhereu.edu
Translation between mnemonic addresses and IP addresses
handled by name servers
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Labs starting next week
Lab instructor: Jasper Lin
His office hours: Tuesdays 1:30-3:30pm
Email: [email protected]
Reading Assignments: Chapter 4.1- 4.3
Homework Assignment 4
(Due Next Wednesday March 14th)
Page 142: 2, 9, 11, 12, 15
Page 189: 4, 9
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