2. CT212F (Sept 2008) CT212 Course Team P.1 212F (Sept 2008) Network Programming and Design Lecture 2 (Network Basics & Architecture) Course Coordinator : Dr. Philip Tsang Tutor : Mr. Ken Ho, Mr. Lee, Bo-sing (Joe) URL of my TA’s teaching website : http://ucourse.ouhk.edu.hk/~t441051/ct212 Link of today’s lecture: http://labsupport.no-ip.org/~opms/temp/ppt2swf.html

3. CT212F (Sept 2008) CT212 Course Team P.2 Agenda n Further Course Info  Syllabus  Material  Assessment  Support n Your UNIX account Lecture 2 n Your Internet/Network/ mobile phone experiences {Video capture n Convert PPT to flash web page

4. CT212F (Sept 2008) CT212 Course Team P.3 Your Unix Account n Server: labsupport.no-ip.org n IP address (how do you find out?) n Login s+first 7 digits n Passwd : ptsang123 n Change your passwd after you login using secure telnet such as putty.[ See Lab2.1 of your lab book]

5. CT212F (Sept 2008) CT212 Course Team P.4 Lecture 2 n Objective of Lecture 2 n Lecture 2  Network classification : LAN & WAN  Layering network model – OSI & TCP/IP  LAN topology  Network Transport method : Ethernet & Token ring  Components of network Cable concentrating devices Cable concentrating devices Transmission media Transmission media NOS (to be discussed in Tutorial 2) NOS (to be discussed in Tutorial 2)  Introduction to E-commerce & network games

6. CT212F (Sept 2008) CT212 Course Team P.5 n Identify building blocks (components) of network n Describe how these building blocks can be glued together n Explain the layers of the OSI model, & describe specific networking services within each layer of the OSI model. n Describe the physical characteristics of coaxial cable, STP, UTP, fiber-optic & atmospheric transmission media. n Discuss the Ethernet & Token Ring network transport systems n Describe the basic topologies, & explain the benefits & uses of different topologies n Describe the features of different network devices Objectives of Lecture 2

7. CT212F (Sept 2008) CT212 Course Team P.6 nDefinition of computer network  a group of computers & networking devices that are connected by some type of transmission media. The computers can communicate, provide or access shared resources, with the help of some networking S/W. nWhat does a network provide?  Entertainment (network games)  E-commerce  Share resources & data (storage, print, file,..)  Provide internet services (email, web, dns, ics,..)  Management/Workflow automation  Online discussion  Video conference…… Network classification (1)

8. CT212F (Sept 2008) CT212 Course Team P.7 nClassification of networks by size  LAN (Local Area Network) within an office or building within an office or building usually private usually private  WAN (Wide Area Network) across city, country or even international across city, country or even international Connected through public data network provided by carrier Connected through public data network provided by carrier nNowadays, most LANs or WANs are connected to INTERNET Network classification (2)

9. CT212F (Sept 2008) CT212 Course Team P.8 Network classification (3)  Classification of networks by transmission media: 1.Wired network  Transmission media is cable  Eg. Cat5. UTP, optic fiber, etc 2.Wireless network  Transmission media is through air  Eg. RF or Infrared

10. CT212F (Sept 2008) CT212 Course Team P.9 Layered network model (1)  In order to allow 2 computers to communicate, exchange data, share/access resource via a network, these 2 computers must follow a number of rules. The rules are so many and complicated. These rules are called networking protocols.  We need a method/mechanism to develop & handle these rules.  So, a layered network model is required for computer networking.  There are 2 networking models – OSI & TCP/IP

11. CT212F (Sept 2008) CT212 Course Team P.10 Layered network model (2) nLogical view of a layered network model  Network is divided into a number of layers  Lowest layer is numbered as 1, higher layer is numbered with larger number  Layer N (Boss) request service, layer N-1 (employee) provide service  Each layer is ignorant about implementation of other layers  Each layer only knows the interface (SAP) to directly lower or upper layer  Peer to peer protocol (refer to next slide)

12. CT212F (Sept 2008) CT212 Course Team P.11 n Peer-to-Peer Protocol Layered network model (3)

13. CT212F (Sept 2008) CT212 Course Team P.12 Layered network model (4) nAdvantages  Simplify complexity of network design & implementation  Easy for human to discuss & analyze  Allow interoperability between products from different vendors  Change of any layer is transparent to other layers  Implementation of any layer is independent of other layers

14. CT212F (Sept 2008) CT212 Course Team P.13 Layered network model (5) – OSI (1) n OSI model  7 layers – Application, Presentation, Session, Transport, Network, Data link, Physical layer “ A Police Stole Three New Dupoint Products” “ A Police Stole Three New Dupoint Products”  Well-defined  More restrictive in layering structure  Transport layer can use different protocols eg. SPX for Netware  Usually as a reference point for discussion use or academic research. Seldom implemented

15. CT212F (Sept 2008) CT212 Course Team P.14 Layered network model (6) – OSI (2) nLayer 1 - The Physical Layer  Deal with the physical, electrical characteristics of the physical medium.  Connectors, pin assignment, electrical currents, encoding, and light modulation  Eg. V.35, V.24, RJ45, Ethernet, 802.3, 802.5, FDDI, NRZI, NRZ, etc. nLayer 2 - The Data Link Layer  Define how a packet is transmitted as bits/ frames of bits  Perform error detection/correction by CRC  Eg. Frame Relay, HDLC, PPP, FDDI, ATM, Ethernet, Token ring, etc.

16. CT212F (Sept 2008) CT212 Course Team P.15 Layered network model (7) – OSI (3) nLayer 3 - The Network Layer  defines logical addressing for identifying any node  Packet forwarding  Fragmentation at sender or intermediate node  reassembly at destination  Eg. IP, IPX, AppleTalk DDP nLayer 4 - The Transport Layer  Provide end-to-end transmission of data  Perform error recovery  Perform flow control  Perform congestion control  Reordering of the incoming data stream when packets arrive out of order  Connection-oriented or connectionless-oriented  Eg.TCP, UDP, SPX

17. CT212F (Sept 2008) CT212 Course Team P.16 Layered network model (8) – OSI (4)  Layer 5 - The Session Layer  Define how to start, control, and end conversations (called sessions)  Control and management of multiple bidirectional messages  The session layer creates ways to imply which flows are part of the same session and which flows must complete before any is considered complete,  E.g. ATM machines  NFS, NetBios names

18. CT212F (Sept 2008) CT212 Course Team P.17 Layered network model (9) – OSI (5) nLayer 6 - The Presentation Layer  Define data format  Perform data format translation  Perform data encryption and decryption  For example, binary or ASCII transfer of FTP, Character Sets translation in RDBMS  TIFF, GIF, JPEG, ASCII, EBCDIC, MPEG, MIDI, MP3, Big5, GB nLayer 7 - The Application Layer  Interface between application & user  Specify protocols used between applications (communications capabilities)  Eg. FTP, http, Telnet, NFS, SMTP, SNMP