cccna r&s-02-the tcp-ip and osi networking models

©2015 Amir Jafari – www.amir-Jafari.com

Routing and Switching 200-1202 - The TCP/IP and OSI Networking Models

The TCP/IP and OSI Networking Models


Agenda

Basic Ideas About Computer Networking

TCP/IP Networking Model

OSI Networking Model

Comparing OSI and TCP/IP



Perspectives on Networking

How you use the Internet from home high-speed Internet connection like DSL or cable TV



Perspectives on Networking

Enterprise Network

Small Office Home Office (SOHO)



Networking Model

Also called either a networking architecture or networking blueprint

Networks require all the devices to follow the rules

The networking model defines rules about how each part of the network should work, as well as how the parts should work together

The networking model refers to a comprehensive set of documents

Protocol: set of logical rules that devices must follow to communicate

Like an architectural blueprint for building a house

Vendors build their products with some networking model



History Leading to TCP/IP

Systems Network Architecture (SNA) published by IBM in 1974

Open Systems Interconnection (OSI) networking model International Organization for Standardization (ISO) To standardize data networking protocols to allow communication

between all computers across the entire planet

TCP/IP (Transmission Control Protocol/Internet Protocol) Department of Defense (DoD) Researchers at various universities volunteered to help further

develop the protocols OSI has slower formal standardization process as compared with

TCP/IP



History Leading to TCP/IP



Overview of the TCP/IP Networking Model

References a large collection of protocols that allow computers to communicate

Requests for Comments (RFC): define a protocol

Referring to standards or protocols created by other standards body or vendor consortium

Layers: Help people understand a networking model, Each model breaks the functions into a small number of

categories




TCP/IP actually has two alternative models The model on the left shows the original TCP/IP model listed in RFC

1122 The TCP/IP model on the right is a common method used today




TCP/IP Architectural Model and Example Protocols



TCP/IP Application Layer

Provide services to the application software running on a computer

The application layer does not define the application itself

Provides an interface between software running on a computer and the network itself



HTTP Overview

HTTP (Hyper Text Transfer Protocol)

HTTP defines how web browsers can pull the contents of a web page from a web server



HTTP Protocol Mechanisms

Uniform Resource Locators (URL) The full version of most web addresses begins with the letters “http,” which means that HTTP is used

to transfer the web pages



TCP/IP Transport Layer

Transport layer protocols provide services to the application layer protocols that reside one layer higher in the TCP/IP model

The two most commonly used transport layer protocols :1. Transmission Control Protocol (TCP) 2. User Datagram Protocol (UDP)



TCP Error Recovery Basics

TCP/IP needs a mechanism to guarantee delivery of data across a network

To recover from errors, TCP uses the concept of acknowledgments



Same-Layer and Adjacent-Layer Interactions



TCP/IP Network Layer

One major protocol: the Internet Protocol (IP)

Provides several features, most importantly, addressing and routing

TCP/IP defines two versions of IP: IP Version 4 (IPv4) and IP Version 6 (IPv6).



Internet Protocol and the Postal Service



Internet Protocol Addressing Basics TCP/IP host—needs a unique address so that it can be identified in

the network

Defines how to group addresses together



Internet Protocol Addressing Basics

This style of number is called a dotted-decimal notation (DDN)

Routers are networking devices that connect the parts of the TCP/IP network together for the purpose of routing (forwarding) IP packets to the correct destination

Routers make decisions based on the IP address included with the packet

IP host refers to any device, regardless of size or power, that has an IP address and connects to any TCP/IP network.



IP Routing Basics

The TCP/IP network layer, using the IP protocol, provides a service of forwarding IP packets from one device to another

The process of forwarding the IP packet is called IP routing.



TCP/IP Link Layer (Data Link Plus Physical)

defines the protocols and hardware required to deliver data across some physical network

Ethernet network, implements link-layer protocols



TCP/IP Link Layer (Data Link Plus Physical)

The link layer includes all the variations of Ethernet protocols, along with several other LAN standards

The link layer includes wide-area network (WAN) standards for different physical media, such as the Point-to-Point Protocol (PPP) and Frame Relay

The TCP/IP link layer includes two distinct functions1. Functions related to the physical transmission of the data2. Protocols and rules that control the use of the physical media



Comparing the Original and Modern TCP/IP Models



Data Encapsulation Terminology)

Each layer adds its own header to the data supplied by the higher layer

Encapsulation: the process of putting headers (and sometimes trailers) around some data



Names of TCP/IP Messages)




The first large effort to create a vendor-neutral networking model

OSI no longer exists as a networking model

Although some of the original protocols referenced by the OSI model still exist

The OSI model has many similarities to the TCP/IP model from a basic conceptual perspective



Comparing OSI and TCP/IP



Describing Protocols by Referencing the OSI Layers

The comparison of OSI layers to other protocol models is a general comparison of major goals, and not a comparison of the specific methods

For Example, both the OSI and TCP/IP network layers define logical addressing and routing. However, the addresses have a different size, and the routing logic even works differently.



OSI Layers and Their Functions



OSI Layering Concepts and Benefits

Benefits of layered protocol specifications:

Less complex

Standard interfaces

Easier to learn

Easier to develop

Multivendor interoperability

Modular engineering



OSI Encapsulation Terminology

OSI uses a more generic term: protocol data unit (PDU)

The TCP/IP and OSI Networking Models


References

1) Cisco Systems, Inc, www.cisco.com/

2) Wendell Odom ,”Cisco CCENT/CCNA ICND1 100-101 Official Cert Guide”, Cisco Press, USA, 2013

http://www.cisco.com/

cccna r&s-02-the tcp-ip and osi networking models

Technology

original tcpip model

networking architecture

osi networking models

amir jafari

data networking protocols

networking blueprint

tcpip application layer

protocols osi