Network Classification and Standards

Organizational Communications and TechnologiesPrithvi N. Rao

Carnegie Mellon UniversityWeb: 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

Ability to move applications and data from one system to another without re-programming and data conversion

Scalability 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)

Provides routing mechanisms between nodes on a network Concerned with addressing and identification of nodes

Datalink 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

5 Session Layer

4 Transport Layer

3 Network Layer

2 Data Link Layer

1 Physical Layer

End User Interface

Data Translation

Time Management

Messages

Packets

Frames

Data Bits

drivers

hardware

NOS

NetBIOS

Comparison of OSI, TCP/IP and SNA

Application

Presentation

Session

Transport

Network

Data Link

Physical

OSI TCP/IP IBM SNA

Process or application

FTP, Telnet, or SMTP

TCP/UDP

Internet

Network AccessOr Local Network

End User Applications

Presentation Services

Data Flow

Transmission Control

Path Control

Data Link

Physical

Network Compatibility

Network OperatingSystem

Hardware

Network Application

DriverVersion &Specs

System BoardBIOS

NIC Card Configuration

NOS Version and Manufacturer

Summary Classification of networks based on

Size Ownership Type of media Switching method Logical Access Method

TCP and SNA are examples of layered approaches