Introduction to Computer Networks and Data Communications

What is computer network?

A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource sharing among a wide range of users (cited from technophobia).

Cell Phone Layout

Constantly expanding market across the U.S. and world • Third and fourth generation services available in many areas and under many types of plans • Latest generation includes higher speed data transfers (100s to 1000s of kilobits per second)

TDMA Time Division Multiple Access

Divide the available user channel by time.

Local Area Network to Local Area Network Layout

Found in systems that have two or more LANs and a need for them to intercommunicate A bridge like device (such as a switch) is typically used to interconnect LANs Switch can filter frames

Physical layer

Handles the transmission of bits over a communications channel Includes voltage levels, connectors, media choice, modulation techniques The processes of transmitting and receiving packets on a given link can be controlled both in the software device driver for the network card, as well as on firmware or specialized chipsets. DSL, Bluetooth, USB, Modem

Wide Area Network to Wide Area Network Layout

High speed routers and switches are used to connect one wide area network to another Thousands of wide area networks across North America, many interconnected via these routers and switches

Microcomputer to Local Area Network Layout

Highly common throughout business and academic environments, and now homes Typically a medium to high speed connection Computer (device) requires a NIC (network interface card) NIC connects to a hublike device (hub or switch) CAT5 or CAT6 cable

Personal Area Network to Workstation Layout

Interconnects wireless devices such as smartphones, laptops and notebooks, and music playback devices Used over short distances such as a few meters Bluetooth, wireless ad hoc connection, infrared communication, Universal Serial Bus connection, etc

4th Generation

LTE (Long Term Evolution) theoretical speeds of 100 Mbps or more, actual download speeds 10 15 Mbps HSPA (High Speed Packet Access) 14 Mbps downlink, 5.8 Mbps uplink; HSPA+ theoretical downlink of 84 Mbps, 22 Mbps uplink (T-Mobile)

Local Area Network to Wide Area Network Layout

One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network) A router is the typical device that performs LAN to WAN connections Routers are more complex devices than switches

Microcomputer to Internet Layout

Popular with home users and small businesses Technologies such as DSL (Digital Subscriber Line) and cable modems are common.CAT3, CAT5, CAT6 and optic cable Router Authorization technologies are necessary RADIUS, Kerberos, etc

Network (Internet or internet work or IP) layer

Responsible for creating, maintaining and ending network connections Determine routing information and applies it to each packet Transfers data packet from node to node (e.g. router to router) within network

Network access (data link) layer

Responsible for transferring data between adjacent network nodes in WAN or between node on the same LAN segment. MAC addressing, LAN switching, etc

What technologies are essential to computer networks

Signaling, addressing, routing, error checking, multiplexing,

CDMA Code Division Multiple Access

Spreads the transmission of signal over a wide range of frequency.

2.5 Generation

Supports more bandwidth intensive data streams of text and images.New protocol for transmitting data at faster speeds were developed.GPRS (General Packet Radio Service) can transmit data at 30 kbps to 40 kbps CDMA2000 1xRTT (one carrier radio transmission technology)

Signal

Twisted pair wire, coaxial cable, optic cable Terrestrial Microwave Transmission,WiMax, WiFi, Bluetooth, Infrared, etc

3rd Generation

UMTS (Universal Mobile Telecommunications System) also called Wideband CDMA Supports downstream data rates of 220 kbps to 320 kbps The 3G version of GPRS UMTS not backward compatible with GSM (thus requires phones with multiple decoders) 1XEV (1 x Enhanced Version) 3G replacement for 1xRTT two forms:1xEV DO for data only 1xEV DV for data and voice

Local Area Network to Metropolitan Area Network Layout

Used to interconnect companies (usually their local area networks) to networks that encompass a city MAN is usually provided by ISP High speed networks with redundant circuits Optic cable is used. Metro Ethernet is latest form of metropolitan LAN

GSM Global System for Mobile Communications

Uses a different form of time division multiple access technology

Application layer

Where the application using the network resides Process to process communications Common network applications include web browsing, e mail, file transfers, and remote logins

Suppose you want to connect your Smartphone to your car stereo What kinds of factors do we need to consider to make a network?

WiFi, WiMax, Terrestrial Microwave Transmission, Wired network

Wide area network

a large network that encompasses parts of states, multiple states, countries, and the world

Personal area network

a network of a few meters, between wireless devices such as smartphone, laptops, and similar devices

Bluetooth

a specification for short range, point to point or point to multipoint voice and data transfer

DAMPS (Digital AMPS)

applied digital multiplexing techniques on top of AMPS analog channels

PCS (Personal Communication Systems)

essentially all digital cell phone service

AMPS (Advanced Mobile Phone Service)

first popular cell phone service; used analog signals and dynamically assigned channels

Data

information that has been translated into a form more conducive to storage, transmission, and calculation

Local area network

networks that are small in geographic size spanning a room, floor, building, or campus

Metropolitan area network

networks that serve an area of 1 to 30 miles, approximately the size of a typical city

Transport layer

responsible for delivering data to the destination. provides reliable, ordered and error checked delivery.TCP, UDP, etc

Compression

the technique that can maximize the amount of data sent over a medium

Multiplexing

the transmission of multiple signals

Solid state drive

uses integrated circuit assemblies as memory to store data persistently

Hard disk drive

uses rapidly rotating disks (platters) coated with magnetic material