Session 1

Objectives: By the end of this session, the student will be able to:  Define the basic terminology of networks  Recognize the individual components of the big picture of computer networks  Outline the basic network configurations  Cite the reasons for using a network model & explain how they apply to current network systems  List the layers of the OSI model and describe the duties of each layer  List the layers of the TCP/IP protocol suite and describe the duties of each layer  Compare the OSI and TCP/IP protocol suite and list their differences and similarities

Definition of a Network 3 Network “An interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areas” Direct Interaction Internet ABM Interac Phone Indirect Interaction TTC roads (driving) shopping (the store's inventory tracking system)

Definition of a Network 4 Scale of a network PAN - Personal Area Network span several metres – laptops, PDAs, wireless LAN – Local Area Networks span a room, floor, building, campus MAN -Metropolitan Area Networks up to 80km (typical city size). High-speed networks connecting businesses and businesses to Internet WAN – Wide Area Networks spans portions of provinces, multiple provinces, countries and the world

Data and Signals 5 Data – an aspect of information to be moved from one computer to another Signals – the means to move the data TEST

Data and Signals 6 Digital Signal Analog Signal

Data and Signals 7 Data Communications Transmission of Digital Data or Analog Data over Digital or Analog Networks Digital NetworkAnalog Network Digital Datano conversionrequires modem Analog Datarequires sampling,no conversion then encoding using digitizer (a.k.a CODEC)

Voice Network vs. Data Network 8 Voice Network Historically an analog network carrying only voice (telephone calls) Data Network Historically a digital network carrying only data Merging of the Networks These networks are merging with use of modems to carry data over voice networks and VoIP (Voice over IP) to carry voice (telephone calls) over data networks

Components of the Network 9

Terminal/Microcomputer-to-Mainframe Dumb Terminal Terminal without processor, limited RAM, and a modem Typically slow speed Proprietary protocol PC as a Terminal Requires emulation software, perhaps hardware as well 10

Microcomputer-to-Local area network Services provided Printer sharing, file sharing, application sharing Common implementation Data on server is downloaded to PC. PC manipulates data PC returns data to server 11

Microcomputer-to-Internet 12

LAN-to-LAN Share software and peripherals. Screening information through switches for security or performance reasons 13

PAN-to-Workstation PANs emerged in late 1990s. Typically an off-line connection that requires the data repositories to periodically synchronize their data 14

LAN-to-MAN Typically uses fibre-optic links. Can transmit data at LAN speeds (very fast). Businesses use it to connect to their ISP. 15

LAN-to-WAN A business may wish to connect their LAN to the Internet (a WAN) A router is used to convert the LAN data into WAN data Modern routers can also provide some security functions 16

Sensor-to-LAN Common in manufacturing environments Connected to –assembly lines –robotic control devices –oven temperature –chemical analysis equipment to data gathering computers that control movements, operations, sound alarms, etc. 17

Satellite and Microwaves Satellite and microwaves A means to connect networks over prohibitively expensive distances (using wire), or over rough terrain (mountainous regions). Both voice networks and data networks use this technology. 18

Wireless Telephone Wireless telephone (cell phone) Newer technologies have less background noise Can transmit limited amounts of data Police and Emergency services use a portion of the frequency range to transmit data between laptops and central computer systems Cellular Digital Packet Data standard governs this technology 19

Components of a Network 20 Components of a network Wires Printed circuit boards wiring connectors and jacks computers centrally located wiring concentrators disk and tape drives computer applications Data communications programs for: data transfer error checking network access network privacy

Open Systems Interconnect Model Application Layer The application that is using the network resides here: file transfer remote login web browsing Creates data package with message contents and addresses. 21 Message and addressing

Open Systems Interconnect Model Presentation Layer Miscellaneous functions for ensuring message is presented properly to sender or receiver: Performs code conversion (ASCII/EBCDIC) Encryption / Decryption Compression/Decompression 22 addressing

Open Systems Interconnect Model Session Layer Least used layer Responsible for Establishing sessions between users Token management (a software token is passed back and forth to determine which computer talks during the current session), Synchronization points (backup points in case of errors or failures, eg transmitting a large book, and having synchronisation points at the end of each chapter) Tokens now are usually inserted at the Application layer, possibly the Transport layer Synchronisation now points are usually inserted at the Application layer 23 addressing

Open Systems Interconnect Model Transport Layer Ensures the data packet that left the originating station is identical to the packet received at the final destination No transmission errors Data arrives in the same order it was transmitted No duplication of data Responsible for end-to-end error control and end-to-end flow control This layer must be able to work across all kinds of networks whether thay are reliable or not Will try to recover from error conditions and return to a known safe-state if the underlying layers experience reset or restart conditions 24 addressing Error detection Flow control

Open Systems Interconnect Model End-to-end Layers The end-to-end layers are: Application Layer Presentation Layer Session Layer Transport Layer These four layers are responsible for the data transmitted between the end points of the network. They are only acted on by the end points, whereas the remaining layers perform their function at each node along the network path 25

Open Systems Interconnect Model Network Layer Responsible for: Creating Maintaining Ending network connections As package of data is sent from node to node on the network, this layer ensures that proper addressing is added to get the packet to its next intended receiver Applies: Routing information to get packet through network Performs congestion control 26 addressing Error Detection Flow Control Network Layer info

Open Systems Interconnect Model Data-link Layer Responsible for taking data from Network layer and transforming it into a Frame Contains: Identifiers that mark the beginning and ending of the frame Control information Address information (identifies a particular workstation in a line of mulitiple workstations) May perform Error Control Must perform Flow Control to ensure next workstation is not overwhelmed with too much data Whereas the Transport Layer performs error control and flow control between end- points, Data-link Layer performs error control and flow control between each node on the path 27 addressing Error Detection Flow Control Network Layer info Data-link Layer info

Open Systems Interconnect Model Physical Layer Handles transmission of bits over a communications channel Responsible for: voltage levels plug and connector dimensions pin configurations usually choice of wire or wireless media determined other electrical and mechanical issues As digital or analog data is encoded or modulated onto a digital or analog signal, this layer also determines the encoding technique or modulation technique. 28 addressing Error Detection Flow Control Network Layer info Data-link Layer info

TCP/IP Protocol Suite Application Layer Supports network applications Also incorporates the functions of the Presentation layer of the OSI model Frequently used applications: File Transfer Protocol (FTP) Telnet Simple Mail Transfer Protocol (SMTP) Simple Network Management Protocol (SNMP) Hypertext Transfer Protocol (HTTP) 29 Message and addressing

TCP/IP Protocol Suite Transport Layer Similar to OSI Transport Layer Commonly uses TCP (Transmission Control Protocol) to maintain error-free, end-to-end connection TCP includes: error control information in case one packet of a sequence does not arrive at its destination packet sequencing information so that all packets stay in the same sequence UDP (User Datagram Protocol) is another protocol at this level, although less frequently used 30 Message and addressing Error Detection Flow Control

TCP/IP Protocol Suite Network Layer Roughly equivalent to OSI Network Layer However, TCP/IP uses Internet Protocol (IP) almost exclusively to transfer data between networks Prepares a packet (a fixed-sized collection) of data so that it can move between networks on the Internet or between corporate networks. 31 Message and addressing Error Detection Flow Control Network Layer info

TCP/IP Protocol Suite Network Access Layer Roughly equivalent to OSI Data-link and Physical Layers 32 Message and addressing Error Detection Flow Control Network Layer info Network Access Layer info

Request for a Web Page 33

Logical / Physical Connections 34

RFC Process 35 RFCs are available at:

RFC Process 36 Process Internet draft – worked on by 1 or more groups until ready to be published as an RFC RFC assigned a number (proposed standard) Implemented and tested by a number of groups- results published If passes a minimum of two independent and interoperable implementations elevated to Draft Standard After results of test implementations, and if no further problems, elevated to Internet Standard

Internet Bureaucracy 37 Internet Society (ISOC) Internet Architecture Board (IAB) Internet Engineering Task Force (IETF) Internet Research Task Force (IRTF) Non-profit, international committee that provides support for the entire standards making process Technical Adviser to ISOC Working groups: Internet protocols, security, user services, operations, routing and network management Long-range goals of Internet Working groups: Architecture, technology, applications and protocols