Transcript 1.Introduction

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Grading
 Attendance : 20%
 H/W: 20%
 Term-project: 30%
 Final exam: 30%
 Prof. Sang-Jo Yoo
 [email protected] 860-8304(5남369)
Prof. Sang-Jo Yoo
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Text Books
 Data & Computer Communications, Sixth Edition,
William Stallings, Prentice Hall
 Computer Networks, Third Edition, Andrew S.
Tanenbaum, Prentice Hall
 IPng and the TCP/IP Protocols: implementing the
next generation internet, Stephen A. Thomas, Wiley
Prof. Sang-Jo Yoo
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Term-Project
 Project proposal: March 26th
 Project presentation and demo: May 28th
 Socket programming (Winsock)
 Java network programming
 Chatting, file transfer, etc..
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1. Introduction
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Contents
1. Communication Model
2. Data Communication Networking
3. Protocols & Protocols Architecture
4. Standards Organizations
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Computer Networking
 Networking today
 Connectivity from ..,
 Office, factory, class room, labs, libraries, stores, bank, …
 Connectivity regardless of time and place
 Wired links
 Wireless links
 Exploding use of the Internet
 Benefits
 Also, challenges
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Computer Networking
 What is a computer network
 A collection of computers and peripherals connected so that
 Resource sharing is enables
 User/computer communication is enhanced
 And much more …
 The key components are
 Hosts
 Switches/routers
 Links
 Enabling software
 A network may also be a connected collection of smaller
networks
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1. Communication Model
Source System
Source
Destination System
Transmission
System
Transmitter
Receiver
Network
Terminal Adapter
Network
Terminal Adapter
Modem
Modem
Destination
Workstation
PSTN : Public Switched Telephone Network
Simplified Communication Model
Prof. Sang-Jo Yoo
Server
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Data Communication Tasks
Transmission system utilization
Interfacing
Signal generation
Synchronization
Exchange management
Error detection/correction
Flow control
Addressing
Routing
Recovery
Message formatting
Security
Network management
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Transmission System Utilization
- To make efficient use of transmission facilities that are typically shared
among the number of communicating devices
- Various techniques, for example multiplexer, are used to allocate the total
capacity of a transmission medium among a number of users
- Congestion control techniques may be required
RS-232C
X.25
PAD
X.25
Async
Terminal
Ring or Star
B-TE B-TE
Prof. Sang-Jo Yoo
X.25
Packet Switch
B-NT
155 M
X.25 DTE
PAD : Packet Assembly &
Disassembly
DTE : Data Terminal Equipment
B-TE
ATM Switch
B-NT : BISDN Network Terminator
B-TE : BISDN Terminal Equipment
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Interface
- A device must interface with transmission system in order to communicate
with the other devices
PSTN
DTE
Modem
Analog
Digital
Analog
Analog
Analog telephone
PSTN Switch
PSTN Switch
Analog telephone
ISDN
Digital
TE
NT
Digital
Digital
Digital
TE
NT
Digital
TE
ISDN Switch
ISDN Switch
U-interface S-interface
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Terminator
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Signal generation
- capable of being propagated through the transmission system
- interpretable as data at the receiver
Analog
Digital
Analog Signal
(0-3.4kHz)
PSTN Switch
Digital
Analog
Analog Signal
(0-3.4kHz)
PSTN Switch
Digital
NT
Digital
TE
ISDN Switch
ISDN Switch
U-interface
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S-interface -> Digital Waveform
(192Kbps = 2B+D+overhead)
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Synchronization
- Especially , in case of digital communication, receiver must be able to
determine when a signal begins to arrive and when it ends
- It must know the duration of each signal element
Sender
Receiver
Analog
Network
Original Signal
Propagation
1
Noise + Distortion + Original Signal
1
Digital
Network
0
0
duration
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duration
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Exchange management
- Requirement for communication between two party that might be collected
- For example,
Analog Phone : push button for dialing, ringing for alerting, lifting handset
ISDN Phone : Setup Msg, Alerting Msg, Connect Msg, etc
Outgoing Telephone
Lifting handset
Incoming Telephone
PSTN
ready tone for dial
DTMF Dial-Tone
Address Decoding&
Determine Destination
Ringing
Alerting Tone
Connect
Connect (Stop Alerting Tone)
Conversation
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Lifting handset
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Error detection/correction
- Required in circumstances where errors cannot be tolerated
- Channel coding scheme using overhead bit
- Retransmission using protocol (ARQ: Automatic Retransmission Request)
MS
CDMA
Wireless
Network
BS
PSTN
Switch
Data Send(Convolution Code)
Error detection/correction
Real Time Data
ARQ
Retransmission
Non-realtime Data
MS : Mobile Station
BS : Base Station
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PSTN
Subscriber
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Flow control
- Required to assure that source does not overwhelm the destination by sending
data transfer that they can be processed and absorbed
- In case of User-to Network Interface , flow control function is performed in
data link layer
- In case of User-to-User Interface , transport layer has flow control function
UUI
UNI
TE
TE
USER
NETWORK
USER
INFO
RR
RR : Receive Ready
RNR : Receive Not Ready
Enough buffer
INFO
no available buffer
RNR
TR_INFO_PDU
TR_RNR_PDU
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no available buffer
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Addressing & Routing
- Indicate the identify of the intended destination when a transmission facility
is shared by more than two devices
RSN
RSN
B-TE
RSN : Remote Switching Node
HSN : Header Switching Node
IISP : Interim Inter-Switch Protocol
NNI : Network-Network Interface
UNI : User-to-Network Interface
ATM Switch
E.164 Address
(02-2636100-01)
HSN
NNI
IISP
RSN
B-TE
UNI
B-TE
E.164 Address
(02-2616100-03)
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RSN
ATM-MSS
E.164 Address
(042-8695430)
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Recovery
- Needed in situations in which an information exchange is interrupted
due to a fault somewhere in the system
- The Objectivity is either to be able to resume activity at the point of interruption
or at least to restore the state of the systems involved to the condition prior to
the beginning of the exchange
- Generally, Recovery function is applied in transmission facility such as Switch,
Fiber Loop Carrier, SDH system via path duplication, equipment duplication
SDH System
Fault occured
F.O
SDH System
SDH System
SDH System
Transmission Path Duplication
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Message formatting
- An agreement between two parties as to the form of the data to be exchanged
or transmitted
- For example, both sides must use the same binary or ASCII code format for
character
Security
- In sender side, only intended party actually receive the data
- In receiver side, received data have not been altered in transit and data have
actually come from the purported sender
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Network management
- Configure the system
- Monitor its status
- React to failures and overloads
- Plan intelligently for future growth
NMS
Private Network
Target System
(Switch, etc)
Public Network
LAN
SNMP
CMIP
Manager
Client
UDP
IP
OSI 7
Protocol
Physical Layer
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SNMP
UDP
IP
MAC
Agent
Server
SNMP : Simple Network Management Protocol
CMIP : Common Management Interface Protocol
NMS : Network Management System
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2. Data Communication Networking
Wide-Area Networks
- Cover a large geographical area, require the crossing of public right of ways
- Typically, consists of a number of interconnected switching nodes
- Don’t care the content of the data
- Two main technologies : circuit switching, packet switching
- PSTN, PSPDN, Frame Relay &Switching, ISDN, BISDN
Local -Area Network
- The Scope of LAN is small, typically a single building or cluster of building
=> lead to different technical solution
- LAN is owned by same organization that owns the attached devices
=> user care about network management & substantial capital investment
- The internal data rates of LANs are typically much greater that those of wide
are networks
- Ethernet(802.3), ATM LAN, Wireless LAN(802.11)
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Simplified Network Model
Wide Area Network
TE
TE
Switching Node
Source System
Source
Transmission
System
Transmitter
Destination System
Receiver
Local Area Network
TE
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TE
TE
Destination
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3. Protocols and Protocols Architecture
 Protocols: A set of rules governing the exchange of data between two
or more (peer) entities. The key elements of a protocol are syntax,
semantics(procedures), and timing
 Key Elements of Protocol
 Syntax - format, size, and contents of protocol messages or
packets
 Procedures - semantics of messages, actions to take in response
to reception of different messages
 Timing - speed matching etc., when to discard a message,
retransmit, give up, etc.
 Protocol Layering
 Layering is a popular way of structuring such a family of
network protocols
 Each layer represents a new level of abstraction with well defined
function
 Interfaces - primitive objects, operations, and services provided
by one layer to its higher layers.
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Protocol Data Units
Application Data
Transport
Header
Transport Protocol
Data Unit
Network
Header
Network Protocol
Data Unit (packet)
Operation of a Protocol Architecture
Destination Y
Source X
record
record
Application
DSAP
DSAP
Transport
Application
Transport
Transport PDU
Network
Access
DHost
Packet PDU
Prof. Sang-Jo Yoo
DHost
Network
Access
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TCP/IP Protocol Architecture
- used in the grandparent of all computer networks,
the ARPANET, and its successor, the Internet
• Application layer (TELNET,RLOGIN, FTP, SMTP, ...)
• Host-to-host, or transport layer (TCP, UDP)
• Internet layer (IP)
• Network access layer
• Physical layer
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TCP/IP Protocol Architecture Model
Source System
Source
Destination System
Transmission
System
Transmitter
Destination
Receiver
Application
Application
TCP/UDP
TCP/UDP
IP
IP
LAN 2
ARP
ARP
LAN 1
LAN 3
Physical
Physical
Local Router
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Remote router
ARP : Address Resolution Protocol
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ISO OSI 7 Layer Model
Application
Presentation
Provides independence to the application processes from differences in
data representation (syntax)
Session
Establishes, manages, and terminates connections (sessions)
between application processes
Transport
Provides reliable, transparent transfer of data between end points;
provides end-to-end (host-to-host) error recovery and flow control
Network
Provides upper layers with independence from the data transmission and
switching technologies used (routing, congestion control)
Data Link
Provides for the reliable transfer of information across the physical link;
sends blocks of data (frames) with necessary synchronization, error
control, and flow control
Physical
Concerned with transmission of unstructured bit stream over physical
medium; deals with the mechanical, electrical, functional, and procedural
characteristics to access the physical medium (voltages, pin assignments,
bit times, ..)
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Correspondence between TCP/IP and OSI architecture
TCP/IP
OSI
Application
Application
User Space
Presentation
Session
Transport
(host-to-host)
Transport
Internet
Network
Network
Access
Data Link
Physical
Physical
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Software
Firmware
Hardware
Operating
System
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4. Standards Organizations
Internet Engineering Task Force (IETF)
The Internet and Internet Standards
Final Decision
IAB(Internet Architecture Board)
IETF
Internet Engineering Task Force
RFCs
Requests for Comments
Prof. Sang-Jo Yoo
IRTF
Internet Research Task Force
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Standards Track Diagram
Enter
Experiment
Proposed
Standard
Draft
Standard
Standard
Historial
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International Organization for Standardization(ISO)
- international agency for the development of standards on a wide range
of subjects
- voluntary, nontreaty organization
International Electrotechnical Commission
IEC
ISO
JTC1
OSI communication architecture &
the standard at each layer of OSI architecture
ISO & IEC standards
Prof. Sang-Jo Yoo
Joint Technical Committee 1
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ITU( Telecommunications Standardization Sector
ITU-T
15 Study Groups
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CCITT
International Telegraph and Telephone
Consultative Committee
ITU
International Telecommunication Union
ITU-R