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 Ring Advantages Physical Broadcast Inherent Security, Limited Delay Reliability, Limited Delay Disadvantages Poor Security – 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

Architecture of the original Ethernet. 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) 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)

Relation between hosts on LANs and the subnet. Wide Area Networks (1) Relation between hosts on LANs and the subnet.

A stream of packets from sender to receiver. 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

(a) Bluetooth configuration (b) Wireless LAN 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.

The philosopher-translator-secretary architecture. 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 The TCP/IP 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 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.

The principal metric prefixes. Metric Units The principal metric prefixes.