aleksandra smiljanić [email protected] local and wide area networks
TRANSCRIPT
Course Outline: First Third
• Introduction to networking• Transmission media
– Air, twisted pairs, coaxial cables, optical fibers• Data link techniques
– Error detection and correction codes – Sliding window protocol – HDLC, PPP• Medium access protocols
– Ethernet, FDDI, RPR– DOCSIS– Wireless LAN
Course Outline: Second Third
• Switches and QoS– Circuit switches: Clos structure– Packet switch architectures– Weighted fair queueing (WFQ), random early
detection (RED) – High-capacity packet switches • Bridging
– Learning bridges– Spanning tree algorithm
Course Outline: Third Third• Routing – Connection-oriented and connectionless
networks– Distance vector routing– Link state routing– OSPF, RIP
• Transport end-to-end protocols– TCP, UDP
• Applications– FTP, Telnet, Email, DNS, WWW,
Multimedia• Network Security
Business Applications
• Sharing resources
• Common databases for customer records, inventory, accounts
• E-commerce
• Video-conferencing
• Disseminating the information, and coordination
Home Applications
• Getting the remote information
• Person-to-person information
• E-commerce
• Entertainment
• E-flea
Wireless Applications
• Portable offices
• Trucks, taxis, police need to communicate
• Help with orientation in the area
• Car rental return
• M-commerce
• Status of the machines
Network Types
• Local Area Networks
• Metropolitan Area Networks
• Wide Area Networks
• Wireless Networks
• Home Networks
• Internetworks
Wireless Networks
Categories of wireless networks:
• System interconnection
• Wireless LANs
• Wireless WANs
Home Network Categories
• Computers (desktop PC, PDA, shared peripherals)• Entertainment (TV, DVD, VCR, camera, stereo, MP3)• Telecomm (telephone, cell phone, intercom, fax)• Appliances (microwave, fridge, clock, furnace, airco)• Telemetry (utility meter, burglar alarm, babycam).
Network Hardware
• Transmission medium
• Transceivers: transmitters and receivers on the point-to-point connections
• Multiplexers, demultiplexers
• Packet and circuit switches
• Bridges
• Routers
• Servers, gateways, management units
Transmission Medium
• Air: different frequency bands
• Wires: twisted pairs
• Coaxial cables
• Optical fibers
Transceivers
• Transmitters perform modulation and coding to provide efficient and reliable communication.
• Receivers perform the reverse operations.
• Depending on the medium transceivers are electronic devices, antenas, or lasers and photodiodes.
Multiplexers and Demultiplexers
• Multiplexers receive multiple lower bit-rate streams of data and according to some rule transmit the higher bit-rate stream of data.
• Demultiplexers do the opposite.
Circuit and Packet Switches
• It does not make sense to connect every user with every other user in the network.
• Circuit and packet switches connect multiple inputs to multiple outputs.
• In circuit switches, the configuration pattern changes on a slow time scale.
• In packet switches, the configuration changes on a packet-per-packet basis.
Servers, Gateways, etc.
• Servers store various kinds of information for users, for example DNS databases, e-mails, web pages and provide it to the users.
• Gateways convert data format, and negotiate QoS with the network.
Network Software
• Protocol Hierarchies• Design Issues for the Layers• Connection-Oriented and Connectionless Services• Service Primitives• The Relationship of Services to Protocols
Service Primitives (2)
Packets sent in a simple client-server interaction on a connection-oriented network.
Reference Models with Layers
• A layer should have well defined function
• Function of a layer should be internatinationally standardized
• The information flow between interfaces should be minimized
Comparing OSI and TCP/IP Models
Concepts central to the OSI model• Services• Interfaces• Protocols
Concept of TCP/IP
• Implementation of the required functionality with three layers
A Critique of the OSI Model and Protocols
Why OSI did not take over the world
• Bad timing
• Bad technology
• Bad implementations
• Bad politics
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
Example Networks• The Internet
• Connection-Oriented Networks: X.25, Frame Relay, and ATM
• Ethernet
• Wireless LANs: 802.11
The ARPANET
(a) Structure of the telephone system.(b) Baran’s proposed distributed switching system.
The ARPANET
Growth of the ARPANET (a) December 1969. (b) July 1970.(c) March 1971. (d) April 1972. (e) September 1972.
TCP/IP Development
• In 1974, TCP/IP model has been established by Cerf and Kahn, and incorporated into Berkeley UNIX.
• Because of the large number of hosts, domain name system (DNS) was created in 1980s.
Internet Usage
• Traditional applications (1970 – 1990) – E-mail– News– Remote login– File transfer
• World Wide Web developed by CERN physicist Tim Bernars-Lee, and Mark Andressen at National Center for Supercomputer applications
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• Main sectors
• Radiocommunications• Telecommunications Standardization• Development
• Classes of Members• National governments• Sector members (AT&T, Cisco, Intel, AOL Time
Warner…)• Associate members• Regulatory agencies (FCC)
ISO• 200 Technical Committees, divided into
subcommittees, and working groups involving 100000 voluneers.
• TC97 in charge for computers and information processing.
• American National Standards Institute (ANSI) is US representative in ISO.
• National standards organization -> committee draft ->draft international standard -> standard
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.