EEL 4781 Computer Communication Networks

Lecture 1

Network types, Architecture

Connection-Oriented vs. Connectionless

Introduction

Computer network a system of separate computers interconnected to complete a task

ie: internet, LAN Distributed system similar to a computer network except the network

appears to the user as one system

Ie: WWW (World Wide Web), MMORPG

Introduction

An example of a computer network with two clients and one server

Server

Client

Client

Uses of Computer Networks

Business Applications Resource sharing, VPN, web application, email, VoIP, remote desktop

Home Applications Peer-to-peer communication, Twitter, instant messaging, Facebook, Wikipedia, IPTV

Uses of Computer Networks

E-Commerce Business-to-consumer ordering books online Business-to-business car manufacturer ordering tires from supplier Government-to-consumer government distributing tax forms electronically Consumer-to-consumer auctioning second-hand products online Peer-to-peer music sharing

Uses of Computer Networks

Mobile and Wireless Users Mobile user Mobile device but connection does not have to be wireless Wireless user Connects through wireless medium but not necessarily a mobile device Applications Text messaging, GPS, NFC, sensor networks

Uses of Computer Networks

Social Issues Net neutrality All data on the internet should be treated equally Digital Millennium Copyright Act Authorizes takedown notices Companies can profile users based on their search history Cookies are small files that can be used to supply this information Gmail targets ads based on your activity. Viruses, malware, botnet, phishing, CAPTCHAs

Network Hardware

Personal Area Network (PAN) 1m Local Area Network (LAN) 10m - 1km Metropolitan Area Network (MAN) 10km Wide Area Network (WAN) 100km - 1000km Internet 10,000km

Network Hardware

Personal Area Network communication of the range of a person Bluetooth, RFID, peripheral devices (keyboard, mice, printer)

Local Area Network privately owned network that covers a single building Called enterprise networks used by businesses Devices used are access points, wireless routers, and base stations WiFi IEEE 802.11, Ethernet 802.3

Network Hardware

Metropolitan Area Network covers an entire city Cable television networks, WiMAX IEEE 802.16

Wide Area Networks covers a country or continent Connects users from a long distance apart and are generally internetworks Virtual private networks, network service provider

Network Hardware

Internetworks (Internet) Largest network Encompasses the entire world Most simply put, it is a large network made up of smaller networks connected together Originated from ARPANET (1950s) and NSFNET (1970s)

Network Hardware

Routing Algorithm How the network decides which path to use

Forwarding Algorithm How the router decides where the packet will be sent to next

Network Software

The network has been organized into a stack of layers Each of these layers performs some type of function Every layer needs protocols in order to standardize the communication

Network Software

Transport

Network

Link

Physical

Application

Example of the protocol stack used in this bookHeaders with additional data are added at each layer

H4

H4

H4

H4

H3

H3H2

H3H2H1

Transport

Network

Link

Physical

Application

H4

H4

H4

H4

H3

H3H2

H3H2H1

User 1 User 2

Physical Medium

Network Software

Design issues for the layers Reliability

some packets might get corrupted (error detection and error correction) Evolution of the network

Packets might need to be split in order to meet routers specifications Scalability

Network architecture needs to be able to vary in size without hurting performance

Network Software

Design issues for the layers Resource allocation

Fair vs unfair, static vs dynamic Flow control, congestion control, Quality of Service (QoS)

Security Encryption, authentication

Network Software

Static allocation of bandwidth Each user is given a fixed fraction of bandwidth whether or not they are using it Wastes extra resources when the user is inactive

Dynamic allocation of bandwidth Statistical multiplexing A queuing system is setup and users send data as they want The queue can be fair (FCFS) or unfair (priority)

Network Hardware

Two modes of transmission are point-to-point and broadcasting Unicasting is a form of point-to-point transmission with one sender and one receiver Multicasting sends data to every connected machine that registers as a receiver Broadcasting sends data to every connected point

Network Software

Connection-oriented service Telephone philosophy (direct) A negotiation between the sender and receiver is made before a connection is made

Connection-less service A packet is sent to the receiver without an established handshake Store-and-forward switching Intermediate nodes wait for the entire packet before

forwarding

Cut-through switching Intermediate nodes forward packets as they come instead of waiting for the complete message

Network Software

Connections-oriented services Reliable message stream ie: sequence of pages Reliable byte stream ie: movie download Unreliable connection ie: VoIP

Network Software

Connections-less services Unreliable datagram ie: junk email Acknowledged datagram ie: text messaging Request-reply ie: database query

Internet Architecture

Please refer to handwritten notes Tiers (figure 1-29)

Data centers and server farms Backbone, IXP, POP, DSLAM, CMTS FTTH, Dialup, Cable, DSL

TCP vs UDP

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