ITEC350 Networks I Lecture 1 Hwajung Lee. References Panko, “Business Data Networks and...
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Transcript of ITEC350 Networks I Lecture 1 Hwajung Lee. References Panko, “Business Data Networks and...
ITEC350 Networks ILecture 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
HYBRIDSOF THESE
RING
STAR
BUS
MESH
Comparison of Basic Topologies
Topology Bus Star Ring
Advantages Physical Broadcast
Inherent Security, Limited Delay
Reliability, Limited Delay
Disadvantages PoorSecurity – All stations see the data at once
Inefficient – collisions when two or more stations send at once.
Poor Reliability (central controller is single point of failure)
Poor Security – All stations see the data 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.
WANWide Area Network (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 SoftwareProtocol 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
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
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)
AcronymsPOP (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 TechnologiesEthernet
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 TechnologiesFiber 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• Radiocommunications• Telecommunications Standardization• Development
Classes of Members• 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.