Download Evolution of PC_LANS and Networks

Network Classification and
Standards
Organizational Communications and Technologies
Prithvi N. Rao
Carnegie Mellon University
Web: http://www.andrew.cmu.edu/course/90-702/
Reading
Data Communication Fundamentals
(Stallings and van Slyke) Chapter 5
TCP/IP and Other Protocol
Architectures (Stallings and van Slyke)
Chapter 12
Objectives

Describe the methods for classifying computer
networks

List the different size classification of networks

List the two major types of transmission media

List two types of switching service

Define the layered approach to communication
architectures
Objectives


Describe the seven layers of the Open Systems
Interconnection (OSI) model
Compare TCP/IP and SNA architectures to the OSI
model
Network Topologies and
Components

Computer networks classified in the following ways

Size

Ownership

Type of transmission media

Type of switching service

Logical access method
Classification




Size refers includes number of users and geographic
location
Local Area Network (LAN) spans less than 1 km
Campus Area Network span 5 to 100 km and are
privately owned
Metropolitan Area Network (MAN) span 2 to 100 km
and found within campuses or within and office
complex
Classification


Wide Area Network (WAN) spans more than 100 km
WAN is the “long haul” network of choice and spans
the nation or entire world
Ownership


Determines who is ultimately responsible for the
maintenance of the network components and the
addition of new equipment
Private





Private businesses, universities or individuals
Includes all cables, and intermediate equipment
Includes most LAN and MAN
Provide the greatest flexibility of service
Restrict who can connect to them and distance of
communication
Ownership

Public owned by public utility companies




Owned predominantly by the phone companies
Some MAN and nearly all WAN networks are in this category
Offer tremendous connectivity
Provider determines connectivity and flexibility of service
Transmission Media


Type of transmission media identifies network by
physical media used to communicate between
locations
Bounded


Cable, wire or fiber optic media in which signal is contained
Various types of cables and are closely related to various
network topologies
Transmission Media


Type of transmission media identifies network by
physical media used to communicate between
locations
Bounded


Cable, wire or fiber optic media in which signal is contained
Various types of cables and are closely related to various
network topologies
Transmission Media

Unbounded



Microwave, satellite, radio wave or infrared media
WAN service providers use “long-haul” unbounded media
Typically there is a combination of media types used in
providing services to users
Switching Service

Circuit Switching




Analogous to a telephone call
Line is maintained throughout duration of conversation
Transmission resources are dedicated and reserved for
duration of connection
Service is optimal for continuous or time sensitive
information flow



Bulk file transfer (not necessarily time sensitive)
Voice
Video
Switching Service

Packet Switching






Analogous to the postal service; package can take several
possible routes to reach destination
Network information is broken into packets
Transmission resources are shared by many connections.
More than one path to destination
Each transmission unit must contain addressing information
More efficient because they share resources
Provide best to non-time sensitive data



Logging sessions
Transaction processing
Query and response systems
Logical Access Method

Connection Oriented logical access requires user to
establish connection with the receiver before
communication can take place

Sender and receiver must both terminate connection

Applies to most voice and wide area packet networks




Public switched voice network
X.25, T1 and T3 high speed communication channels
ISDN frame relay and ATM (Asynchronous Transfer Mode)
Transmission Control Protocol (TCP)
Logical Access Method



Connectionless logical assumes communication
channel is always available
Senders and receivers transmit without establishing a
communications channel
PC-LAN provide connectionless access




Broadcast LAN (ethernet)
Broadcast satellite transmission
Cable TV and FM radio
User Datagram Protocol (UDP)
Protocol Defined



Agreed upon set of rules defining how devices
communicate
Define which language is used and the grammar and
syntax
Define message format
Standard Protocol Defined

Set of specifications defining a specific method or
technology for use in a fixed set of applications




Hardware
Software
Access methods
Message handling formats
Standard Setting Bodies


Institute of Electrical and Electronic Engineers (IEEE)
American National Institute of Standards and
Technology (NIST)

International Standards Organization (ISO)

Internet Activities Board (JAB)

Consultative Committee for International Telegraphy
and Telephony (CCITT)
Open Systems


Products and technologies designed and
implemented in accordance with vendor-independent
standards
Distributed multi-vendor environment open systems
enable users to achieve portability among
applications, data and people
Goals of the Open Systems
Movement

Portability


Scalability


Ability to move applications and data from one system to another
without re-programming and data conversion
Ability to grow applications from one computer platform to larger
more platforms in the future
Interoperability

Ability for a network of heterogeneous computers to operate with
the same data and applications independently of one another and
to use those applications in the native machine interface
The OSI Model


International Standards Organization (ISO) developed
layered model for supporting communications
architecture
Modularity was motivation



Each layer is independent of another layer
Protocol of one layer does not rely on the protocol of any
specific protocol of any other layer for information
Function duplication should be avoided
Resulting OSI model not widely implemented although the US
Government is pushing for acceptance of this architecture
Layer Purpose

Application




Provides interface between end-user services
Email, file transfer
All lower layers support this layer
Presentation




Performs protocol conversion, data encryption and decryption
Performs data compression
Concerned mainly with representation of data rather than content
Interfaces to application layer above it and to lower level services
Layer Purpose

Session




Establishes and terminates data streams between network
nodes
Manages and synchronizes direction of data flow
NetBIOS is one of the first session layer protocols
Transport (TCP, SPX, XNS)



Provides an additional layer of connection below session
layer
Ensures that session connections are transparent and
handles details of data transfer
Assembles packets for routing by the network layer
Layer Purpose

Network (IP and IPX)



Datalink



Provides routing mechanisms between nodes on a network
Concerned with addressing and identification of nodes
Defines the access method for connection with network
Error detection and connection are important functions here
Physical


Determines the electrical mechanical aspects of network
Responsible for bit stream transmission and error checking
OSI Summary




Simplify model and use it as basis for discussion
Application, Presentation and Session layers deal with
how computers on each end handle information
internally
Network, Data Link and Physical layers handle data
once it has entered the network
Transport layer interfaces between upper and lower
OSI Summary




Simplify model and use it as basis for discussion
Application, Presentation and Session layers deal with
how computers on each end handle information
internally
Network, Data Link and Physical layers handle data
once it has entered the network
Transport layer interfaces between upper and lower
OSI Model
7 Application Layer
6 Presentation Layer
NetBIOS
5 Session Layer
4 Transport Layer
NOS
drivers
hardware
End User Interface
Data Translation
Time Management
Messages
3 Network Layer
Packets
2 Data Link Layer
Frames
1 Physical Layer
Data Bits
Comparison of OSI, TCP/IP
and SNA
OSI
TCP/IP
Application
Presentation
Session
Transport
Network
End User Applications
Process or application
FTP, Telnet, or SMTP
TCP/UDP
Internet
Data Link
Physical
IBM SNA
Network Access
Or Local Network
Presentation Services
Data Flow
Transmission Control
Path Control
Data Link
Physical
Network Compatibility
Network Operating
System
Driver
Version &
Specs
System Board
BIOS
NIC Card Configuration
NOS Version and Manufacturer
Network Application
Hardware
Summary

Classification of networks based on





Size
Ownership
Type of media
Switching method
Logical Access Method
TCP and SNA are examples of layered approaches