Presentation on theme: "CE80N Introduction to Networks & The Internet Dr. Chane L. Fullmer UCSC Winter 2002."— Presentation transcript:
CE80N Introduction to Networks & The Internet Dr. Chane L. Fullmer UCSC Winter 2002
January 29, 2002CE80N -- Lecture #82 Class Details Web Search Assignment due today. Midterm on Thursday. –Up to 50 questions.. (multiple choice) Taken from book, lectures and glossary –Section times.. Wed 7:30PM Web page submission: – to Subject: cmpe080n-assgn4
January 29, 2002CE80N -- Lecture #83 Grading Schedule
January 29, 2002CE80N -- Lecture #86 Master/Slave Networking Early computers were large and expensive. –One computer per company –Controlling I/O devices at remote sites. Master-Slave networking.
January 29, 2002CE80N -- Lecture #87 Small Computer Use Networks To Interact Personal computers had processing power and acted independently. –Resulting in: Peer-to-peer networking Distributed computing
January 29, 2002CE80N -- Lecture #88 Peer-to-Peer Networking Peer-to-Peer networking permit communication among computers in which all computers are equal.
January 29, 2002CE80N -- Lecture #89 Distributed Computing Distributed computing is any interaction that involves two or more computers communicating over a network.
January 29, 2002CE80N -- Lecture #810 Distributed Computing On The Internet The Internet offers an amazing diversity of services. –Sending messages –Retrieving files –Printing documents Also, diversity of styles of interaction. –Interacting with humans –Interacting with a computer program
January 29, 2002CE80N -- Lecture #811 Client-Server Computing Despite the diversity of services and differences in their use, all are client- server.
January 29, 2002CE80N -- Lecture #812 Three Basic Facts Programs communicate. TCP/IP does not create or run application programs. Computers can run multiple programs.
January 29, 2002CE80N -- Lecture #813 Programs Are Clients Or Servers Any program that offers a service is a server; any program that contacts a service is a client.
January 29, 2002CE80N -- Lecture #814 A Server Must Always Run A server program must always be ready to receive requests. Server software starts and runs automatically.
January 29, 2002CE80N -- Lecture #817 People Prefer Names To Numbers Names are preferred for computers instead of IP addresses. This is possible by: –Allowing users to name their machine –Allowing users to enter alphabetic name for their IP address –Providing a service that translates an alphabetic name to a numeric address
January 29, 2002CE80N -- Lecture #818 Naming A Computer Can Be Difficult Or Fun A name creates a sense of personality. –Can reflect the role of the computer Mail Smtp –Can reflect the name of the owner John –Can reflect a naming scheme (aka “naming convention”) I.e., chemical gases –Hydrogen, Helium, Argon, ….
Figure 18.1 The fifty most common names assigned to computers on the Internet in 2000.
January 29, 2002CE80N -- Lecture #820 Computer Names Must Be Unique Each computer on the Internet must have a unique name. The Internet uses a familiar idea. –Extends name by adding strings –Appends a suffix to the name –Qualifies each name by giving the type of organization
January 29, 2002CE80N -- Lecture #821 Names With Many Parts The Internet naming scheme allows names to contain multiple parts. –Permits organizations to add additional parts such as: Groups Departments Locations –www.cc.purdue.eduwww.cc.purdue.edu –www.soe.ucsc.eduwww.soe.ucsc.edu
January 29, 2002CE80N -- Lecture #822 Domain Names Outside The US Most countries append a two-letter code to the domain name. –Allows for alternative schemes jp = Japan uk = United Kingdom –Recognized internationally
January 29, 2002CE80N -- Lecture #823 Translating A Name To An Equivalent IP Address Internet communication software must use IP addresses to send and receive datagrams. –Translates names to IP addresses automatically –Called the Domain Name System (DNS)
January 29, 2002CE80N -- Lecture #824 Computer Name Lookup Is Automatic Figure 18.2 To communicate with a remote computer, an application program asks a local domain name server for the remote computer’s IP address If the local domain name does not know the answer, it contacts a remote domain server automatically. Numbers on the arrows tell the order of the four step taken.
January 29, 2002CE80N -- Lecture #825 IP Addresses And Domain Names Are Unrelated Domain names resemble IP addresses. –Can be deceiving –Look similar An IP address is a 32 bit number divided into 4 parts. A domain name may contain multiple parts.
January 29, 2002CE80N -- Lecture #826 Software Network Tools Nslookup: –Converts name IP address > nslookup mit.edu > nslookup Traceroute (tracert in windows) –Traces path between hosts –Displays delay along path > tracert mit.edu > tracert
January 29, 2002CE80N -- Lecture #827 Summary Distributed Computing Paradigm (Client-Server) –Programs communicate –TCP/IP does not create/run programs –Computers can run multiple programs Clients contact servers Servers always run 24/7…
January 29, 2002CE80N -- Lecture #828 Summary Computer naming … –Must be unique across the Internet –Name prefix added to domain suffix Domain Name System (DNS) provides translations between names and IP address –Names are similar in style, but not directly related to IP address
January 29, 2002CE80N -- Lecture #829 Glossary Client – A program that uses the Internet to contact a remote server Client-Server Computing –The interaction between two programs when they communicate across a network
January 29, 2002CE80N -- Lecture #830 Glossary Distributed Computing –Computations involving more than one computer Peer-to-Peer Networking –Any network system in which all computers are equal Server –A program that offers a service
January 29, 2002CE80N -- Lecture #831 Glossary Domain Name –The name assigned to a computer on the Internet. A single computer’s name can contain several strings separated by periods. Domain Name System –(DNS) The Internet service used to look up a computer’s name and find the computer’s IP address.
January 29, 2002CE80N -- Lecture #834 The Telephone Network Telephone analogy used for Internet development –1876: Alexander Graham Bell obtains patent for the telephone –1927: Commercial telephone service by radio between New York and London opens for the first time Provides Universal Service Ubiquitous Designed for voice transmission
January 29, 2002CE80N -- Lecture #835 Digital to Analog Analog is easy, but prone to distortion Digital is distortion free, but lossey Computers use binary numbers to encode digital information –ASCII encodes characters Sampling.. –Nyquist theorem Quantization –Introduces lossiness (quantization error)
January 29, 2002CE80N -- Lecture #836 Digital Telephone Network Circuit switched –circuit is limited to 64 kbps –wasteful when idle –unsuitable for multimedia services Telephone network is now digital –Multiplexed – TDMA DS0, DS1 = 24 DS0, DS2 = 4 DS1…..
January 29, 2002CE80N -- Lecture #837 Introduction to Networks Modulation of signals Modulator/Demodulator -- Modem Encoding of data to binary –ASCII Error detection –Parity, checksum LAN Technology –Easy, cheap, reliable
January 29, 2002CE80N -- Lecture #838 The Early Years The Internet began as an ARPA research project. The TCP/IP protocol software was developed to make the Internet operational. The Internet is an Open System, with the technology freely available to all. The Internet documentation is available on- line in the form of reports known as RFCs.
January 29, 2002CE80N -- Lecture #839 The Early Years BSD UNIX distributed TCP/IP suite freely to universities in the early 80s 1982 US Military adopted TCP/IP as primary communication standard Exponential growth from its inception IAB formed to coordinate development IETF - major technical development body –Working groups
January 29, 2002CE80N -- Lecture #840 The Early Years 1988 – NSFNET Backbone 1992 – Privatization (ANSNET) Exponential growth from its inception –Half of the users today have been there less than one year…… IP Address 32 bit limitation
January 29, 2002CE80N -- Lecture #841 The Global Internet was the first killer app. EBONE brought Europe to the Internet 1997 – Every continent is connected 1998 – Every populated country is connected The Internet is the new infrastructure TCP/IP is the key to how the Internet works.
January 29, 2002CE80N -- Lecture #842 How Does the Network Work? Circuit Switching –Reserves resources Packet Switching –Shares resources –Increased overhead – headers Packets are labeled with destination info –Efficient – resources used as needed –Unreliable – packets can be dropped
January 29, 2002CE80N -- Lecture #843 How Does the Network Work? Packet Switching –Store and Forward Packets move one hop at a time Decisions are made at each hop –Delay.. Processing delay Queueing delay Transmission delay Propagation delay
January 29, 2002CE80N -- Lecture #844 How Does the Network Work? A router is used to interconnect networks –LANs to LANs or LANs to WANs –Routers forward packets from one network to another Process is called Routing –Routers are the building blocks of the Internet
January 29, 2002CE80N -- Lecture #845 How Does the Network Work? ISPs provide the connection service to access the Internet –“The Last Mile” Dialup ADSL Cable modem Wireless –Also may provide , web space or other services
January 29, 2002CE80N -- Lecture #846 IP & Routing Protocols and protocol stack –Internet stack, OSI stack –Layering model IP addressing –Class-based vs. CDIR IP forwarding Routing –Link State –Distance Vector
January 29, 2002CE80N -- Lecture #847 Transport Layer Principles behind transport layer services: –multiplexing/demultiplexing –reliable data transfer –flow control, congestion control Instantiation and implementation in the Internet –UDP, unreliable delivery –TCP, reliable with control
January 29, 2002CE80N -- Lecture #848 See you Thursday!