01 - The TCPIP and OSI Networking Models

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01 - The TCP/IP and OSI

Networking ModelsBy Muhammad Asghar Khan

Reference: CCENT/CCNA ICND1 Official Exam Certification Guide By Wendell Odom


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Agenda

Networking Model ? TCP/IP Networking Model

OSI Reference Networking Model

Comparing OSI & TCP/IP Networking Models

Layering Concepts and Benefits

Layers Interaction Concept

Data Encapsulation Terminology

2 www.asghars.blogspot.com


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Networking Model ?

Networking Model or Networking Architecturerefers to an organized set of documents

Collectively, these documents define details of how

to create a complete network

By the late 1980s, the world had many competing

vendor-proprietary networking models plus the two

competing standardized networking models

TCP/IP Networking Model


TCP/IP won in the end

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TCP/IP Networking Model Initially started by the U.S. Defense Department

Researchers at various universities volunteered to

help further develop the TCP/IP Networking Model

TCP/IP Networking Model defines a large collection

of protocols that allow computers to communicate

Like other Networking Architectures, TCP/IP classify

the various protocols into different categories or

layers

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Application Layer TCP/IP application layer protocols provide services to

the application software (e.g. web browser) running

on a computer

HTTP is an example of TCP/IP Application Layer

protocol

The following figure depicts the usage of HTTP

protocol

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Transport Layer Transport layer defines the level of service and status

of the connection used when transporting data

It consists of two main protocol options: the

Transmission Control Protocol (TCP) and the User

Datagram Protocol (UDP)

In layered architecture, each layer provide service to

the layer above it

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The following figure depicts the services provided bythe TCP to HTTP

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Internet Layer It is also responsible for routing of IP datagrams

Internet layer of the TCP/IP networking model,

primarily defined by the Internet Protocol (IP)

IP defines logical addresses, called IP addresses,

which allow each IP hosts to have an address with

which to communicate

IP also defines routing, the process of how a routershould forward, or route, packets of data

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The following figure depicts the services provided bythe IP to TCP

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Network Access Layer This layer defines the protocols and hardware

required to deliver data across physical network

The term Network Access refers to the fact that this

layer defines how to physically connect a hostcomputer to the physical media over which data canbe transmitted

The functions of Network Access Layer can be broken

into two major categories: Data Link (Encapsulation & Addressing)

Physical ( Bit Transmission)

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Ethernet is one of the protocol at the TCP/IP NetworkAccess Layer

Ethernet defines the required cabling, addressing,

and protocols used to create an Ethernet LAN

Network Access Layer also defines protocols used todeliver data across WAN links, such as Point-to-Point

Protocol (PPP) and Frame Relay

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The following figure depicts the services provided bythe Ethernet and PPP to IP

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In late 1970s, the Open Systems Interconnection (OSI)reference model was created by the ISO

The OSI model was meant to help vendors create

interoperable network devices

The OSI reference model consists of seven layers

Each layer defines a set of typical networking functions

OSI as a whole never succeeded in the marketplace

So, why to read about OSI? Well, the OSI model now is

mainly used as a point of reference for discussing other

protocol specifications

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The seven layers are divided into two groups: Upper Layers

Lower Layers

Upper Layers

Lower Layers

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Summary of the functions defined at each layer ofthe OSI modelAll People Seem To Need Data Processing (Layers

7 to 1)

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Devises and Protocols covered in CCNA exams, andtheir comparable OSI layers.

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Comparing OSI & TCP/IP Networking Models

OSI can be used as a standard of comparison toother networking models

You can examine any networking protocol or

specification and make some determination of

whether it most closely matches OSI Layer L1, L2,

and so on

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Layering Concepts and Benefits

The layers break a large, complex set of conceptsand protocols into smaller pieces, making it easier

to talk about, easier to implement with hardware

and software, and easier to troubleshoot

The following list summarizes the benefits of

layered protocol specifications

Less complex compared to not using a model

Easier to learn Easier to develop

Multivendor interoperability

Modular engineering

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Layers Interaction Concept

Same-Layer Interaction on Different Computers

The two computers use a protocol to communicate withthe same layer on another computer

The protocol defined by each layer uses a header that istransmitted between the computers, to communicate

what each computer wants to do

Adjacent-Layer Interaction on Same Computer

On a single computer, one layer provides a service to ahigher layer

The software or hardware that implements the higherlayer requests that the next lower layer perform theneeded function

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Data Encapsulation Terminology

The term encapsulation refers to the process ofputting headers and trailers around some data

TCP/IP Encapsulation

OSI Encapsulation

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OSI uses a more generic term:

protocol data unit, or PDU


Documents

01 - The TCPIP and OSI Networking Models