Going Online Chapter 3a

Connectivity Computer strength Ability of computers to communicate with each other at computer speeds Ultimate example is Internet Interconnected Networks Collection of independent networks w/ Internet host connected 24/7

Internet Began in 1969 as APRANET project of Dept of Defense Build a communications network for military, scientists, researchers across nation Important stipulation – network should remain functional even if parts were down Resulted in network with no central computer and multiple communication pathways between sites

Internet (contd) 1990 government project ended Today Internet is commercial Governed by international group of volunteers Sets standards Coordinate global operation

Ingredients to go online Communications channel Connection method Communications protocol Communications software

Communication channels Rated by bandwidth Number of bits transmitted per second (bps) Low bandwidth = narrow bandwidth High bandwidth = broadband Broadband is now generic term for High–speed Internet access Always on

Communication channels Dialup access with POTS Narrowband Temporary connection Required modem to convert Computer digital signals Phone line analog signals ISP provides access to a host Internet server 56 Kbps

Communication channels Cable Broadband Available from cable TV companies Limited to metropolitan areas Requires cable modem 10 Mbps

Communication channels DSL or digital subscriber line New broadband technology using POTS Required DSL modem Limited to metropolitan areas Two speeds Downstream rate (to client) 9 Mbps Upstream rate (to server) 1.5 Mbps

Communications channels Satellite Broadband Must have southern exposure Problems Latency = lag in response time of ¼ second Weather dependence Requires satellite dish and satellite modem 1.5 Mbps

Communication channels Wireless Requires access point or a link to a wired network Uses short-range radio waves Wi-Fi is the umbrella for several wireless standards (IEEE ) Wireless-B (IEEE b) 11 Mbps, up to 300 ft Wireless-A (IEEE a) 54 Mbps, up to 50 ft Wireless-G (IEEE g) 54 Mbps, up to 300 ft

Connection methods ISP = Internet service provider Commercial service via dialup, cable, DSL, satellite Each channel requires a modem Network = Local Area network (LAN) Network has a host Internet server Broadband access shared by all users in network Requires network interface card (NIC) on each PC

Communication protocols Communication relies on protocols Set of rules computers use to communicate with each other Establish, maintain, terminate connection Many different protocols A single computer can support multiple protocols To communicate both computers must use the same protocol

Communication protocols Protocol of the Internet is TCP/IP Uses an IP address to uniquely identify each user on the Internet Four number (0-255), separated by periods i.e IP address is assigned by ISP or network

TCP/IP Numbers are difficult to remember so TCP/IP includes DNS service Translates domain names to IP address Users use domain names to access Internet i.e. Names must be registered Charge is assessed to support Internet operations

DNS Domain names are read from right to left To determine IP address of First, goes to root DNS server (.) for addresses of next level DNS server (edu) Next, goes to edu server and retrieves address for next level DNS server (victoriacollege) Finally, goes to victoriacollege DNS server to retrieves address for www (host PC)

Communications software To be continued…