ITEC350 Networks I
Lecture 1
Hwajung Lee
References
 Panko, “Business Data Networks and
Telecommunications,” 4th Edition, Prentice
Hall, 2003.
 Tanenbaum, “Computer Networks,” 4th Edition,
Prentice Hall PTR, 2003.
 Wells, “Guide to Linux Networking and
Securitity,” Course Technology, 2003.
 Minasi, “Mastering Windows Server 2003,”
SYBEX Inc., 2003.
What is Computer Networks?
A collection of autonomous computers
interconnected by a single technology
 Interconnected via:
•
•
•
•
•
Copper wire
Fiber optics
Microwaves
Infrared
Communication satellites, etc.
Why Computer Networks?
Business Applications
 [Goal1] Resource Sharing
• To connect isolated computer and information to
be able to extract and correlate information about
the entire company.
• To make all programs, equipment (ex: printers,
scanners, and CD burners), and especially data
available to anyone on the network without regard
to the physical location of the resource an the user.
 [Goal 2] Communication Medium
• Electronic mail (e-mail)
• Shared resources (ex: shared hard driver)
• Videoconferencing, a shared virtual blackboard
 [Goal 3] Electronic Commerce (e-commerce)
• To do business electronically with other
companies. (ex: order the parts of a product from a
variety of suppliers)
• To do business with consumers over the Internet.
Home Applications
 [Goal 1] Access to remote information
• Newspapers, Digital library
 [Goal 2] Person-to-person communication
• Email, Instant messaging, Chat room,
Worldwide newsgroups
• Peer-to-peer communication (ex: Napster)
• Internet phone, Internet video phone, Internet
radio, Telelearning
Home Applications (cont.)
 [Goal 3] Interactive entertainment
• Video on demand, Interactive live television show,
Multiperson real-time simulation games – possibly
with worldwide shared virtual reality.
 [Goal 4] Electronic commerce
• Home shopping, Electric flea markets, On-line
auctions
 Mobile Network Users

[Goal] To have a portable office
•
Cellular phone, PDA, Military use, Wireless
sensor networks, Mobile-commerce,
Wearable wireless computers
Combinations of wireless networks and mobile computing.
Network Types Based on Roles
 Terminal Connection
Network Types Based on Roles
 Client-server
Network Types Based on Roles
Peer-to-peer
 Computers act as both client and server on the
network
 There is no reliance on a centralized server to
provide access to data and other resources
 Compared to a centralized client-server model,
peer-to-peer is decentralized, meaning any
host can communicate with any other host
Network Topologies
RING
STAR
MESH
HYBRIDS
OF THESE
BUS
Comparison of Basic Topologies
Topology
Bus
Star
Advantages
Physical
Broadcast
Inherent Security, Reliability,
Limited Delay
Limited Delay
Disadvantages
Poor
Security – All
Poor Reliability
stations see the data
at once
Inefficient –
collisions when two or
more stations send at
once.
Ring
Poor Security
(central controller is – All stations
single point of
see the data
failure)
as is travels
around the ring
Classification of interconnected
processors by scale.
Personal Area Network (PAN)
 A person’s body or desk area
Local Area Networks (1)
Local Area Network (LAN)
 Limited geographical distance: home, office,
building, campus, industrial part
 Customer premises operation
• User firm chooses technology
• User firm needs to manage on ongoing basis
 Low cost per bit transmitted
• Companies can afford high speed
• 100 Mbps to the desktop is typical
Local Area Networks (2)
Two broadcast networks
(a) Bus (b) Ring
Local Area Networks (3)
 Ethernet

Most popular LAN
Architecture of the original Ethernet.
Metropolitan Area Networks
Metropolitan Area Network (MAN)
 Single urban area (city and its suburbs)
 Faster than long-distance WANs
 Still slower than LANs
Metropolitan Area Networks
A metropolitan area network based on cable TV.
Wide Area Network (WAN)
WAN
 To link sites
• Long distances
 Requires the use of carriers to provide service
• Limited and complex choices but carrier manages
 High cost per bit transmitted
• Companies cannot afford high speeds
• Usually low speed (56 kbps to a few megabits per
second)
Wide Area Networks (1)
Relation between hosts on LANs and the subnet.
Wide Area Networks (2)
A stream of packets from sender to receiver.
Wireless Networks
 Categories of wireless networks:
 System interconnection
 Wireless LANs
• Speed: Upto about 50Mbps
• Distance: Tens of meters
 Wireless WANs (ex: cellular system)
• Speed: below 1Mbps
• Distance: Kilometers
Wireless Networks (2)
(a) Bluetooth configuration (b) Wireless LAN
 Wireless LANs
(a) Wireless networking with a base station.
(b) Ad hoc networking.
 Standard for Wireless LANs
IEEE 802.11 network.
 Wireless WAN Networks
(a) Individual mobile computers
(b) A flying LAN
Network Software
 Protocol Hierarchies
 Design Issues for the Layers
 Connection-Oriented and
Connectionless Services
 Service Primitives
 The Relationship of Services to
Protocols
Network Software
Protocol Hierarchies
 Layers, protocols, and interfaces.
Protocol Hierarchies
The philosopher-translator-secretary architecture.
Protocol Hierarchies (3)
 Example information flow supporting
virtual communication in layer 5.
Design Issues for the Layers





Addressing
Error Control
Flow Control
Multiplexing
Routing
Connection-Oriented and
Connectionless Services
The software used to maintain each protocol
is often called a protocol stack
Transport layer protocols can be:
 Connectionless, or stateless, which sends each
packet without regard to whether any other
packet was received by the destination computer
(implementation: packet switching, UDP)
 Connection oriented, or stateful, which
maintains information about which packets have
been correctly received by the destination
computer (implm.:circuit-switching, TCP)
Connection-Oriented and
Connectionless Services
 Six different types of service.
Service Primitives
 Five service primitives for implementing a
simple connection-oriented service.
Service Primitives (2)
 Packets sent in a simple client-server
interaction on a connection-oriented
network.
Services to Protocols
Relationship
The relationship between a service and a protocol.
Why
Standard or Reference Model?
Consumer
 Easy to select a product which is compatible
with other equipments.
Supplier
 Minimize risk when it develops new
technologies.
Reference Models
 The OSI Reference Model


ISO (International Organization for
Standardization)
OSI (Open Systems Interconnection) Model
 The TCP/IP Reference Model


TCP (Transmission Control Protocol)
IP (Internet Protocol)
 A Critique of the OSI Model and Protocols
 A Critique of the TCP/IP Reference Model
OSI Reference Model
OSI Reference Model
The TCP/IP reference model
Conceptual Models of Networking
(1)
Acronyms
 POP (Post Office Protocol)
 FTP (File Transfer Protocol)
 UDP (User Datagram Protocol)
 TCP (Transmission Control Protocol)
 SMTP (Simple Mail Transport Protocol)
 HTTP (Hypertext Transport Protocol)
 DNS (Domain Name Service)
 ICMP (Internet Control Message Protocol)
 PPP (Point-to-Point Protocol)
 SATNET (Satellite Networks)
 IRC (Internet Relay Chat)
A Critique of the OSI Model and
Protocols
 Why OSI did not take over the world



Bad timing
Bad implementations
Bad politics
Bad Timing
 The apocalypse of the two elephants.
A Critique of the TCP/IP Reference
Model
 Problems:





Service, interface, and protocol not
distinguished
Not a general model
Host-to-network “layer” not really a layer
No mention of physical and data link layers
Minor protocols deeply entrenched, hard to
replace
Networking Technologies
Ethernet
 Most widely used technology
 Three variation of Ethernet based on
transmission speed, or bandwidth
Token-ring
 Uses a token to identify which computer on
the network has the right to transmit data
 Not as fast as Ethernet, and may be more
expensive
Networking Technologies
Fiber Distributed Data Interface (FDDI)
 Reliable, but slower and costlier than Ethernet
Arcnet
 Reliable, but slower token-passing technology
Asynchronous Transfer Mode (ATM)
 high-speed, very reliable and very expensive used
for Internet backbones
Wireless LAN (WLAN)
 No cables used to connect nodes to the network
 Data is transmitted via radio signals of infrared
Networking Technologies
Network Standardization
 Who’s Who in the Telecommunications World
 Who’s Who in the International Standards World
 Who’s Who in the Internet Standards World
ITU
(International Telecommunication Union)
 Main sectors
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Radiocommunications
Telecommunications Standardization
Development
 Classes of Members
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National governments
Sector members
Associate members
Regulatory agencies
IEEE 802 Standards
The 802 working groups. The important ones are marked
with *. The ones marked with  are hibernating. The one
marked with † gave up.
Metric Units
The principal metric prefixes.