Transcript OUHK, CT212 - network programming & design

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
CT212 Course Team
P.1
CT212F (Sept 2008)
Agenda
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Further Course Info
Syllabus
Material
Assessment
Support
Your UNIX account
Lecture 2
 Your Internet/Network/ mobile phone
experiences {Video capture
 Convert PPT to flash web page

CT212 Course Team
P.2
CT212F (Sept 2008)
Your Unix Account
Server: labsupport.no-ip.org
 IP address (how do you find out?)
 Login s+first 7 digits
 Passwd : ptsang123
 Change your passwd after you login using
secure telnet such as putty.[ See Lab2.1 of
your lab book]

CT212 Course Team
P.3
CT212F (Sept 2008)
Lecture 2
Objective of Lecture 2
 Lecture 2
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Network classification : LAN & WAN
Layering network model – OSI & TCP/IP
LAN topology
Network Transport method : Ethernet & Token
ring
Components of network
 Cable concentrating devices
 Transmission media
 NOS (to be discussed in Tutorial 2)
Introduction to E-commerce & network games
CT212 Course Team
P.4
CT212F (Sept 2008)
Objectives of Lecture 2
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Identify building blocks (components) of network
Describe how these building blocks can be glued
together
Explain the layers of the OSI model, & describe
specific networking services within each layer of the
OSI model.
Describe the physical characteristics of coaxial cable,
STP, UTP, fiber-optic & atmospheric transmission
media.
Discuss the Ethernet & Token Ring network
transport systems
Describe the basic topologies, & explain the benefits
& uses of different topologies
Describe the features of different network devices
CT212 Course Team
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CT212F (Sept 2008)
Network classification (1)
Definition 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.
What 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……
CT212 Course Team
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CT212F (Sept 2008)
Network classification (2)
Classification of networks by size
LAN (Local Area Network)
within an office or building
usually private
WAN (Wide Area Network)
across city, country or even international
Connected through public data network
provided by carrier
Nowadays, most LANs or WANs are
connected to INTERNET
CT212 Course Team
P.7
CT212F (Sept 2008)
Network classification (3)
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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
CT212 Course Team
P.8
CT212F (Sept 2008)
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
CT212 Course Team
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CT212F (Sept 2008)
Layered network model (2)
Logical 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)
CT212 Course Team
P.10
CT212F (Sept 2008)
Layered network model (3)
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Peer-to-Peer Protocol
CT212 Course Team
P.11
CT212F (Sept 2008)
Layered network model (4)
Advantages
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
CT212 Course Team
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CT212F (Sept 2008)
Layered network model (5) – OSI (1)
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OSI model
7 layers – Application, Presentation, Session,
Transport, Network, Data link, Physical layer
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“ 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
CT212 Course Team
P.13
CT212F (Sept 2008)
Layered network model (6) – OSI (2)
Layer 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.
Layer 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.
CT212 Course Team
P.14
CT212F (Sept 2008)
Layered network model (7) – OSI (3)
 Layer 3 - The Network Layer
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defines logical addressing for identifying any node
Packet forwarding
Fragmentation at sender or intermediate node
reassembly at destination
Eg. IP, IPX, AppleTalk DDP
 Layer 4 - The Transport Layer
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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
CT212 Course Team
P.15
CT212F (Sept 2008)
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
CT212 Course Team
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CT212F (Sept 2008)
Layered network model (9) – OSI (5)
 Layer 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
 Layer 7 - The Application Layer
 Interface between application & user
 Specify protocols used between applications
(communications capabilities)
 Eg. FTP, http, Telnet, NFS, SMTP, SNMP
CT212 Course Team
P.17
CT212F (Sept 2008)