Chapter 1 - Introduction How do Computer Networks and Internet operate? Explosive growth Internet Economic impact Complexity Abstractions and concepts
How do Computer Networks and Internets Operate? Network: system for connecting computer using a single transmission technology Internet: set of networks connected by routers that are configured to pass traffic among any computers attached to networks in the set Data transmission - media, data encoding Packet transmission - data exchange over a network Internetworking - universal service over a collection of networks Network applications - programs that use an internet
Explosive growth New phenomenon - now, networks are an important part of everyday activities Business Home Government Education Global Internet growing exponentially Initially a research project with a few dozen sites Today, millions of computers and thousands of networks world-wide
Internet Roots in military network called Arpanet Fundamental changes from centralized to distributed computing Incorporated features for reliability and robustness Multiple links Distributed routing Ethernet made local networking feasible TCP/IP protocol made internetworking possible Developed after Arpanet Switchover occurred in 1983 Exponential growth - doubling every 18 months
Economic impact Large industry has grown around: Networking hardware Computers Software Companies must integrate planning, implementation, management and upgrade
Complexity Computer networking is complex Many different hardware technologies Many different software technologies All can be interconnected in an internet No underlying theory Terminology can be confusing TLAs Industry redefines or changes terminology from academia New terms invented all the time
Chapter 2 - Motivation and Tools Introduction Historic motivation ARPA Packet switching Internetworking History and growth Probing the Internet Ping Traceroute
Introduction Motivation Service Tools for exploration
Historic motivation Early computers were expensive Large footprint Centralized Programs took a long time to run Couldn't afford to put computers everywhere
ARPA Advanced Research Projects Agency initiated project to connect researchers with computers Adopted new technology: Packet switching Internetworking Resulted in system for remote access to expensive resources
Packet switching Data transmitted in small, independent pieces Source divides outgoing messages into packets Destination recovers original data Each packet travels independently Includes enough information for delivery May follow different paths Can be retransmitted if lost
Internetworking Many (mutually incompatible) network technologies No one technology appropriate for every situation Internetworking glues together networks of dissimilar technologies with routers Result is virtual network whose details are invisible
History and growth ARPAnet began in late 1960s (not using TCP/IP) TCP/IP developed in late 1970s ARPAnet switched to TCP/IP in early 80s Start of Internet Few hundred computers Few tens of networks
Probing the Internet Two tools: Ping - sends message that is echoed by remote computer Traceroute - reports path to remote computer
Ping Sends packet to remote computer Remote computer replies with echo packet Local computer reports receipt of reply % ping is alive
Traceroute Sends series of packets along path to destination Each successive packet identifies next router along path Uses expanding ring search Reports list of packets