Ccna-2 Osi & Tcp Ref Model

8/3/2019 Ccna-2 Osi & Tcp Ref Model

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OSI & TCP/IPReference Model


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On completing this session, you will be able to:

Describe OSI Reference model

Describe TCP/IP Reference Model

Objectives


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Standard for Networking

ISO OSI Reference Model:(In OSI, all networking processes are divided into logicalgroups, called layers)

TCP/IP Reference Model:(TCP/IP is a condensed version of OSI reference model)

Protocols: (Four types)

LAN Protocols : TCP/IP, SPX/IPX, ATWAN Protocols : HDLC, PPPRouted Protocols : IP, IPXRouting Protocols : RIP, IGRP, EIGRP, OSPF, IS-IS


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APPLICATION

PRESENTATION

SESSIONTRANSPORT

NETWORK

DATA LINK

PHYSICAL1

2

3

4

5

6

7 ISO has defined the generic

Networking standard, calledOpen System Interconnect

(OSI)

OSI Reference Model - 7 Layers


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Keeping differentapplications data separate

User Interface

How data is presentedSpecial processing such as

encryption

TelnetHTTP

ASCII

EBCDICJPEG

Operating System/Application AccessScheduling

Transport Layer

Data Link

Network Layer

Physical

EXAMPLES

Session

Presentation

Application

Role of Upper Layers


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TCPUDPSPX

802.3 /802.2HDLC

EIA/TIA-232, V.35

IPIPX

Presentation

Application

SessionEXAMPLES

Role of Lower Layers

Reliable or unreliable delivery Error correction before retransmit

Combines bits into bytes andbytes into frames

Access to media using MAC address Error detection not correction

Move bits between devices Specifies voltage, wire speed and

pin-out cables

Transport

Data Link

Physical

Network Provide logical addressing which

routers use for path determination


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Encapsulating DataEncapsulating Data

Transport

Data Link

Physical

Network

Upper Layer Data

Upper Layer DataTCP Header

DataIP Header

DataLLC Header

0101110101001000010

DataMAC Header

PresentationApplication

Session

Segment

Packet

Bits

Frame

PDU

FCS

FCS


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Upper Layer Data

De-encapsulating DataDe-encapsulating Data

LLC Hdr+IP+TCP+Upper Layer Data

MA C H e a

d e r

IP + TCP + Upper Layer Data

L L C H e a

d e r

TCP+ Upper Layer Data

I P H e a d

e r

Upper Layer Data

T C P H e a d e

r

0101110101001000010

Transport

Data Link

Physical

Network

Presentation

Application

Session


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Broadcast DomainA group of computers receiving broadcast frames initiatedfrom any device within that group is known as a broadcastdomain.

Collision Domain The network area in Ethernet over which frames collisionwill be deducted. Collisions are propagated by hub & repeater and not by LAN Bridges, Switches and Routers.

Domains


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Q 1

1. Which OSI layer deals with errorcorrection?

A) Physical LayerB) Data Link LayerC) Network LayerD) Transport Layer

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Q 2

2. Which protocols belongs to the OSItransport layer?

A) TCPB) UDPC) SPXD) All the above

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Q 3

3. Which OSI layer converts frames intopackets?

A) Data Link LayerB) Network LayerC) Session LayerD) Physical Layer

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7

6

5

4

3

2

5

4

3

2

Application

Presentation

Session

Transport

Network

Data Link

Physical1

Application

Transport

Internet

Data Link

Physical1

TCP/IP Vs OSI reference model

OSI TCP/IP


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Application Layer Overview

*Used by the router

Application

Transport

Internet

Data Link

Physical

File Transfer- TFTP *- FTP *- NFS

E-Mail

- SMTPRemote Login

- Telnet *- rlogin *

Network Management- SNMP *

Name Management- DNS*

File Transfer- TFTP *- FTP *- NFS

E-Mail

- SMTPRemote Login

- Telnet *- rlogin *

Network Management- SNMP *

Name Management- DNS*


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Transport Layer Overview

Transmission ControlProtocol (TCP)

User DatagramProtocol (UDP)

Transmission ControlProtocol (TCP)

User DatagramProtocol (UDP)

Application

Transport

Internet

Data Link

Physical

Connection-Oriented

Connectionless


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Internet Layer Overview

OSI network layer corresponds to the TCP/IP Internet layer

Internet Protocol (IP)

Internet Control MessageProtocol (ICMP)

Address ResolutionProtocol (ARP)

Reverse AddressResolution Protocol (RARP)

Internet Protocol (IP)

Internet Control MessageProtocol (ICMP)

Address ResolutionProtocol (ARP)

Reverse AddressResolution Protocol (RARP)

Application

Transport

Internet

Data Link

Physical


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TCP Segment Format

Source port (16) Destination port (16)

Sequence number (32)

Headerlength (4)

Acknowledgement number (32)

Reserved (6) Code bits (6) Window (16)

Checksum (16) Urgent (16)

Options (0 or 32 if any)

Data (varies)

20Bytes

Bit 0 Bit 15 Bit 16 Bit 31


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Send SYN(seq=100 ctl=SYN)SYN received

Send SYN, ACK(seq=300 ack=101 ctl=syn,ack)

Established(seq=101 ack=301 ctl=ack)

Host A Host B

1

2

3

SYN received

TCP Three Way Handshake


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IP Datagram

IP Version(4)

Destination IP Address (32)

Options (0 or 32 if any)

Data (varies if any)

1Bit 0 Bit 15 Bit 16 Bit 31

HeaderLength (4)

Priority & Typeof Service (8) Total Length (16)

Identification (16) Flags(3) Fragment offset (13)

Time to live (8) Protocol (8) Header checksum (16)

Source IP Address (32)

20Bytes


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No sequence or acknowledgment fields

UDP Segment Format

Source port (16) Destination port (16)

Length (16)

Data (if any)

1Bit 0 Bit 15 Bit 16 Bit 31

Checksum (16)

8Bytes


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Internet Control Message Protocol

Application

Transport

Internet

Data Link

Physical

Destination

Unreachable

Echo (Ping)

Other

ICMP1


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Internet Control Message Protocol

ICMP

ARP (Address Resolution Protocol)RARP (Reverse Address Resolution Protocol)PING: ICMP echo request (Source to Destination)

ICMP echo reply (Destination to source)Time Exceed

Destination Unreachable:-- Network Unreachable-- Host Unreachable-- Port Unreachable-- Protocol Unreachable

Dont Fragment & Trace route# ICMP Message: (Represents Symbols)!!!!! : Indicates successful delivery of all packets.!!!! : 1st Packet dropped (Lack of Synchronize).. : All Packet lost????? : Destination unknownm.m.m.m.m : Dont fragmentu.u.u.u.u : Unreachable destination


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LAN Protocol

TCP/IP, SPX/IPX, AT

Default LAN protocols are vendor neutral standard andenable in all manufactures machine


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WAN Protocol

Default WAN protocols : HDLC and PPP

HDLC (High-Level Data Link connection ) Cisco proprietary default WAN protocol

CISCO CISCO

PPP (Point-to-point) Industry standard default WAN protocols

Juniper CISCO


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Protocol Standard

Routed Protocols: IP, IPX User protocol carrying routing information when knowing the

path

Routing protocols:

IGP (Interior Gateway routing protocol)RIP, IGRP, EIGRP, OSPF, IS-IS

BGP (Border Gateway routing protocol) ibgp (Interior Border Gateway routing protocol) ebgp(Exterior Border Gateway routing protocol)


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Q 4

4. Which is a connectionless protocol?

A) IP

B) TCPC) UDPD) DHCP

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Q 5

5. What are the default WAN protocols ?

A) TCP/IP

B) HDLC & PPPC) RIP, EIGRP & OSPFD) All the above

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Q 6

6. Define ICMP message type for Destination unknown ?

A) !!!!!B) m.m.m.m.mC) ?????D) u.u.u.u.u

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Q&A


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Summary

In this session, you have learnt to: OSI Reference model TCP/IP Reference Model


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Quizzes & Assignments

The quizzes & Assignments related to thissession are available on the learning portal.

OSI Reference Model TCP/IP Reference Model


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Whats Coming Up

In the next session, you will learn about

Cables & types of cables Different types of Racks How to Crimping a cable Identification and marking of cables


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Feedback

1. How do you rate this session?

A) Excellent

B) GoodC) Satisfactory

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Ccna-2 Osi & Tcp Ref Model

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