07/10/09 m.chai; e.r.edwards 07/10/09 staffordshire university school of computing the osi model and...

07/10/09M.Chai; E.R.Edwards 07/10/09 Staffordshire UniversitySchool of Computing

The OSI Model and TCP/IP

Slide 1


IADCN - Week 2Format

Networking Standards Introduction to root concepts Layered models of processes Why do we need protocols? The seven layers

Slide 2


IADCN - Week 2Standards

Standards are documented agreements containing technical specifications or other precise criteria that stipulate how a particular product or service should be designed or performed

Slide 3


IADCN - Week 2Networking Standards Organizations

American National Standards Institute (ANSI) Electronics Industry Alliance (EIA) Institute of Electrical and Electronic Engineers (IEEE) International Organization for Standardization (ISO) International Telecommunication Union (ITU)

Slide 4


IEEE Networking Specifications

Slide 5


IADCN - Week 2Protocols

The Open Systems Interconnect (OSI) model is not a protocol

It is a conceptual system that most real protocols are based upon

A protocol is an agreed set of rules, an interface between two systems, “a mutually agreed treaty or diplomatic document”– E. g. Traffic lights at a junction control the flow of vehicles

on a road system– This is a simple, world-wide protocol

• Although in France they do not use amber between red and green!

Slide 6


IADCN - Week 2OSI model – Why bother?

Real-world network protocols don’t implement the OSI seven layer protocol stack model

But nearly all network protocols are based on a simplified layered model

The layered model helps us think about the many processes involved in communicating over networks

A good model provides support for thinking “First, solve the problem. Then implement a solution.”

Slide 7


IADCN - Week 2Why a “Layered Model”?

Answer by providing an analogy - The “Big Data Corporation” wants 10,000 mouse mats showing its new corporate logo– The CEO makes the decision, the budget is agreed, the requirements set

and the order processed

– The order is then transferred to a manufacturer

– The order is processed, then sent to the design team

– The design is then created and checked

Note that the process of handling the order goes through many layers within two businesses

Slide 8


IADCN - Week 2A Fine-Grained Breakdown

This is a multilayer model

It shows two different “protocol stacks”

The courier service is analogous to network cabling (in a wired system)

President/CEO

Directors

Quality Control

Marketing

Clerical

Mail Room Mail Room

Courier or Postal Service

Clerical

Design

Manufacture

Slide 9


Communication Between Two Systems

Slide 10


IADCN - Week 2

Version2 10/07/09 Slide 11

ISO OSI Reference Model

Slide 11


Data Transformation

Slide 12


IADCN - Week 2The Seven Layer Model

Nmemonics – – Please do not throw sausage pizza

away!– All PC’s seem to network data

poorly At the top, the Application layer

provides OS services for application software

At the bottom, the Physical layer deals with wiring issues

Application

Presentation

Session

Transport

Network

Data link

Physical

Slide 13


IADCN - Week 2The Application Layer

Provides interface to the software enabling programs to use network devices

Definition of the way that network services use the network Defines how many services work, including

– File sharing, Network Printing, Message Services etc E.g Application Program Interface (API)

– Routine that allows a program to interact with the operating system

– Belongs to the Application layer of OSI Model Microsoft Message Queuing (MSMQ)

– Used in API network environment

– Stores messages sent between nodes in queues

– Forwards them to their destination

Slide 14


IADCN - Week 2The Presentation Layer

This layer “presents” data, which is to say it does some pre-processing, such as– data compression

– encryption

– character set conversion

Translates between the application and the network

Slide 15


IADCN - Week 2The Session Layer

A communications management layer Defines how two computers synchronise, maintain

and close a communication session This includes such things as

– security authentication

– acknowledgement of data transfer

– establishing and relinquishing a connection identity

Slide 16


IADCN - Week 2The Transport Layer

Data packet management Ensures that chunks of data have been transferred

without error – does lots of error and flow control Takes data and packs it into chunks or chops it up into

chunks suitable for transmission Takes chunks and unpacks them or combines them

into data streams

Slide 17


IADCN - Week 2The Network Layer

This is Internet Protocol address layer for path selection around the network

Routing of packets uses IP addresses Network Layer Address

– Resides at Network level of OSI Model

– Follows hierarchical addressing scheme

– Can be assigned through operating system software

Slide 18


IADCN - Week 2The Data Link Layer

Decodes packets into what are called frames which contain– Physical source and destination addressing

– data validity / error checking

The network technology being used will influence how this layer works e.g. Ethernet, token ring …..

To accommodate shared access for multiple network nodes, the IEEE expanded the OSI Model by separating the Data Link layer into two sublayers– Logical Link Control (LLC) sublayer

– Media Access Control (MAC) sublayer

Slide 19


Subdivided Data Link Layer

LLC and MAC sublayers

Slide 20


IADCN - Week 2Data Link Layer Sublayers

LLC – Upper sublayer

– Provides common interface

– Supplies reliability and flow control services

MAC – (Media Access Control)– Lower sublayer

– Appends the physical address of the destination computer onto the frame

– Number uniquely defining a network node– Manufacturer-hard codes the address

• Block ID• Device ID

Slide 21


IADCN - Week 2The Physical Layer

This is the physical networking media layer which includes the cabling technology

Defines the transmission technique and the hardware definitions (connectors and so on)

Networking may take place over copper cables, optical fibres, infra-red radiation, radio waves… and this variation should be transparent to the user

Slide 22


OSI Model Summary

Slide 23


IADCN - Week 2

OSI Model TCP/IP

Transmission Control Protocol/Internet Protocol (TCP/IP) Suite

Slide 24

Application Layer

Transport Layer

Network Layer

Physical and Data Link Layers


IADCN - Week 2Addressing and Protocols

SMTP, FTP, HTTP, DNS, SNMP, Telnet,…

SCTP, TCP, UDP

ICMP, IGMP, ARP, RARP

Port Address

Logical Address

Physical Address

Application Layer

Transport Layer

Network Layer

Physical and Data Link Layers


IADCN - Week 2

Slide 26

Conclusion

We have discussed:- Organizations that set standards for networking Standard “root concepts” of networking Layered models of processes and layers in our

conceptual model of networking Why protocols are required for interoperability Details of the seven layers of the OSI model

07/10/09 m.chai; e.r.edwards 07/10/09 staffordshire university school of computing the osi model and...

Documents