02 Internet Protocol

Revision no.: PPT/2K605/03

CCNA640-801

Internet Protocol

Revision no.: PPT/2K605/03©

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TCP/IP ProtocolThe Transmission Control Protocol/Internet Protocol (TCP/IP) suit was created by the Department of Defense (DoD).Later TCP/IP was included with the Berkeley Software Distribution of UNIX.The Internet Protocol can be used to communicate across any set of interconnected networks.TCP/IP supports both LAN and WAN communications.IP suite includes not only Layer 3 and 4 specifications but also specifications for common applications like e-mail, remote login, terminal emulation and file transfer.The TCP/IP protocol stack maps closely to the OSI model in the lower layers.


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The DoD ModelThe Process / Application Layer

The Host-to-Host Layer

The Internet Layer

The Network Layer


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The DoD & OSI

Application

Application

Presentation

Session

Transport

Network

Data Link

Physical

Host-to-Host

Internet

Network Access

DoD Model OSI Model


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Process/Application Layer

The Process / Application layer defines protocols for node-

to-node application communication and also controls user-

interface specification.

A vast array of protocols combine at this layer of DoD’s

Model to integrate the activities and duties of upper layer of

OSI.

Examples for this layer are :

Telnet, FTP, TFTP, NFS, SMTP, SNMP, DNS DHCP, BootP etc.


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Host-to-Host Layer

The Host-to-Host layer parallels the functions of the OSIs

Transport layer

It performs the following:

Defining protocols for setting up the level of transmission service for

Applications

It tackles issues like creating reliable end-to-end communication.

It ensures the error free delivery of data

It handles packet sequencing and maintains data integrity.


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Internet Layer

Internet Layer corresponds to the OSI’s Network Layer.

It performs the following:

Designating the protocols relating to the logical transmission of

packets over the entire network.

It takes care of the addressing of hosts by giving them an IP address.

It handles routing of packets among multiple networks.

It also controls the communication flow between the two hosts.


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Network Access Layer

This layer is equivalent of the Data Link and Physical Layer of OSI

model.

It performs the following

It monitors the data exchange between the host and the network.

Network Access Layer overseas hardware addressing and defines

protocols for the physical transmission of the Data.

Lets have a look on how TCP/IP Protocol suit relates to the DoD

model layers.


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TCP/IP Protocol Suit at DoD

Process /Application

Host-to-Host

Internet

Network Access

Telnet FTP LPD SNMP

X WindowNFSSMTPTFTP

TCP UDP

ICMP

Ethernet

ARP RARP

IP

FastEthernet

TokenRing FDDI

BootP

TCP/IP Protocol Suit

DoD Model


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Telnet

Telnet is used for Terminal Emulation.

It allows a user sitting on a remote machine to access the

resources of another machine.


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F T P (File Transfer Protocol)

It allows you to transfer files from one machine to another.

It also allows access to both directories and files.

It uses TCP for data transfer and hence slow but reliable.


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Network File System (NFS)

It is jewel of protocols specializing in file sharing.

It allows two different types of file systems to interoperate.


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T F T P (File Transfer Protocol)

This is striped down version of FTP.

It has no directory browsing abilities.

It can only send and receive files.

It uses UDP for data transfer and hence faster but not reliable.


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LPD (Line Printer Daemon)

The Line Printer Protocol is designed for Printer sharing.

The LPD along with the LPR (Line Printer Program) allows

print jobs to spooled and sent to the network’s printers

using TCP/IP.


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X Window

X-windows defines a protocol for the writing of graphical

user interface-based client/Server application.

It allows a program to run on one computer and have it

display on another computer.


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Simple Network Management Protocol

SNMP enable a central management of Network.

Using SNMP an administrator can watch the entire network.

SNMP works with TCP/IP.

IT uses UDP for transportation of the data.


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DNS (Domain Name Service)

DNS resolves FQDN with IP address.

DNS allows you to use a domain name to specify and IP

address.

It maintains a database for IP address and Hostnames.

On every query it checks this database and resolves the IP.


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Bootstrap Protocol (BootP)

BootP stands for Bootstrap Protocol.

BootP is used by a diskless machine to learn the following:

Its own IP address

The IP address and host name of a server machine.

The boot filename of a file that is to be loaded into memory

and executed at boot-up.

BootP is an old program and is now called the DHCP.


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DHCP (Dynamic Host Configuration Protocol)The DHCP server dynamically assigns IP address to hosts.All types of Hardware can be used as a DHCP server, even a Cisco Router.BootP can also send an operating system that a host can boot from. DHCP can not perform this function.Following information is provided by DHCP while host registers for an IP address:

IP AddressSubnet maskDomain nameDefault gateway (router)DNSWINS information


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Transmission Control Protocol (TCP)

TCP works at Transport Layer

TCP is a connection oriented protocol.

TCP is responsible for breaking messages into segments

and reassembling them.

Supplies a virtual circuit between end-user application.


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TCP Segment Format

Bit 31Bit 15 Bit 16Bit 0

Code bits (6)

Reserved (6)

Data (varies)

Options (0 or 32 if any)

Urgent (16)Checksum (16)

Window (16)Header length (4)

Acknowledgment number (32)

Sequence number (32)

Destination port (16)Source port (16)

24 bytes


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UDP (User Datagram Protocol)

A connectionless and unacknowledged protocol.

UDP is also responsible for transmitting messages.

But no checking for segment delivery is provided.

UDP depends on upper layer protocol for reliability.

TCP and UDP uses Port no. to listen to a particular services.


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UDP segment


Data (if any)Checksum (16)Length (16)

Destination port (16)Source port (16)

8 b ytes


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Key Features of TCP and UDP

TCP UDP

Sequenced Unsequenced

Reliable Unreliable

Connection-oriented Connectionless

Virtual circuit Low overhead

Acknowledgments No acknowledgment

Windowing flow control No windowing or flow control


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on. Some common services and port numbers Transport

layer protocol.

FTP TCP 21

Telnet TCP 23

SMTP TCP 25

DNS TCP & UDP 53

DNS uses UDP for name resolution and TCP for Server Zone

Transfers

TFTP UDP 69

POP3 UDP 110

News UDP 144

.


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Port Numbers

Some ports are reserved in both TCP and UDP

Port Numbers have the following assigned ranges:

Numbers below 1024 are considered well-knows ports

Numbers above 1024 are dynamically assigned ports

Registered ports are those registered for vender-specific

applications. Most of them are above 1024.

Maximum Port numbers can go upto 65,535.


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The Internet Layer Protocols

Internet Protocol (IP)

Internet Control Message Protocol (ICMP)

Address Resolution Protocol (ARP)

Reverse Address Resolution Protocol (RARP)


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Internet Protocol (IP)

Provides connectionless, best-effort delivery routing of datagrams.

IP is not concerned with the content of the datagrams.

It looks for a way to move the datagrams to their destination.


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IP header

Data (varies if any)

Fragment offset (13)Flags(3)

Priority and Type of

Service (8)

Header length (4)


Protocol (8)

Options (0 or 32 if any)

Destination IP address (32)

Source IP address (32)

Header checksum (16)Time to Live (8)

Identification (16)

Total length (16)Version(4)

20 bytes


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The Protocol field in an IP header

ProtocolNumbers

InternetLayer

TransportLayer

IP

UDPTCP

6 17


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on. Possible Protocols Found in the Protocol Field of

an IP Header

Protocol Protocol NumberICMP 1IGRP 9EIGRSP 88OSPF 89IPv6 41GRE 47IPX in IP 111Layer 2 tunnel (L2TP) 115


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Internet Control Message Protocol (ICMP)

ICMP messages are carried in IP datagrams and used to

send error and control messages.

The following are some common events and messages that

ICMP relates to:

Destination Unreachable

Buffer Full

Hops

Ping

Traceroute


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Address Resolution Protocol (ARP)ARP works at Internet Layer of DoD ModelIt is used to resolve MAC address with the help of a known IP address.All resolved MAC addresses are maintained in ARP cache table is maintained.To send a datagram this ARP cache table is checked and if not found then a broadcast is sent along with the IP address.Machine with that IP address responds and the MAC address is cached.


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RARP (Reverse ARP)This also works at Internet Layer.It works exactly opposite of ARP.It resolves an IP address with the help of a known MAC address.DHCP is the example of an RARP implementation.Workstations get their IP address from a RARP server or DHCP server with the help of RARP.


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Binary to Decimal and Hexadecimal Conversion

Binary to Decimal Memorization Chart

Binary Value Decimal Value10000000 12811000000 19211100000 22411110000 24011111000 24811111100 25211111110 25411111111 255


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Binary to Decimal and Hexadecimal Conversion (contd.)

Hex to Binary to Decimal Chart

Hexadecimal Value Binary Value Decimal Value0 0000 01 0001 12 0010 23 0011 34 0100 45 0101 56 0110 67 0111 78 1000 89 1001 9A 1010 10B 1011 11C 1100 12D 1101 13E 1110 14F 1111 15


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IP Addressing

IP Terminology

Bits

Bytes

Octet

Network Address

Broadcast Address


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The Hierarchical IP Addressing Scheme

ResearchClass E:

MulticastClass D:

HostNetworkNetworkNetworkClass C:

HostHostNetworkNetworkClass B:

HostHostHostNetworkClass A:

8 bits8 bits8 bits8 bits


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The Hierarchical IP Addressing Scheme (contd.)

Network Address Range: Class AThe Class A range of network addresses:00000000 = 001111111 = 127

Network Address Range: Class BThe Class B range of network addresses:10000000 = 12810111111 = 191

Network Address Range: Class CThe Class C range of network addresses:11000000 = 19211011111 = 223


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The Hierarchical IP Addressing Scheme (contd.)

Network Address Ranges: Classes D and E

The addresses between 224 and 255 are reserved for Class D and E

networks. Class D (224–239) is used for multicast addresses and Class

E (240–255) for scientific purposes .

Network Addresses: Special Purpose

Some IP addresses are reserved for special purposes, so network

administrators can’t ever assign these addresses to nodes.


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Reserved IP Addresses

Broadcast to all nodes on the current network; sometimes called an “all 1s broadcast” or limited broadcast.

Entire IP address set to all 1s (same as 255.255.255.255)

Used by Cisco routers to designate the default route. Could also mean “any network.”

Entire IP address set to all 0s

Interpreted to mean “all nodes” on the specified network; for example, 128.2.255.255 means “all nodes” on network 128.2 (Class B address).

Node address of all 1s

Interpreted to mean “network address” or any host on specified network.

Node address of all 0s

Reserved for loopback tests. Designates the local node and allows that node to send a test packet to itself without generating network traffic.

Network 127.0.0.1

Interpreted to mean “all networks.”Network address of all 1s

Interpreted to mean “this network or segment.”Network address of all 0s

FunctionAddress


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Private IP Addresses

192.168.0.0 through 192.168.255.255

Class C

172.16.0.0 through 172.31.255.255

Class B

10.0.0.0 through 10.255.255.255Class A

Reserved address spaceAddress Class

Reserved IP Address Space


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Broadcast Addresses

These are packets sent from a single source, and transmitted to many devices on different networks.

Multicast

These are sent to a single destination host.Unicast

These are sent to all nodes on the network.Broadcasts (layer 3)

These are sent to all nodes on a LAN.Layer 2 broadcasts


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on. Introduction to Network Address

Translation (NAT)

In NAT terminology, the inside network is the set of networks that

are subject to translation. The outside network refers to all other

addresses—usually those located on the Internet.

NAT operates on a Cisco router—generally only connecting two

networks together—and translates your private (inside local)

addresses within the internal network, into public (inside global)

addresses before any packets are forwarded to another network.


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on. Introduction to Network Address

Translation (NAT) (contd.)

There are different flavors of NAT:

Static NAT:- Designed to allow one-to-one mapping between local and global addresses. This flavor requires you to have one real Internet IP address for every host on your network.

Dynamic NAT:- Designed to map an unregistered IP address to a registered IP address from out of a pool of registered IP addresses. You don’t have to statically configure your router to map an inside to an outside address as in static NAT, but you do have to have enough real IP addresses for everyone who wants to send packets to and from the Internet.

Overloading:- This is the most popular type of NAT configuration. Overloading is a form of dynamic NAT that maps multiple unregistered IP addresses to a single registered IP address (many-to-one) by using different ports. Therefore, it’s also known as port address translation

Documents

02 Internet Protocol