cit232©ifm-cit dept the internet. cit232©ifm-cit dept know how the internet began. understand the...

CIT232 ©IFM-CIT Dept

The Internet


Know how the Internet began.Know how the Internet began.

Understand the architecture of today’s Internet and its relation-Understand the architecture of today’s Internet and its relation-ship with ISPs. ship with ISPs.

Understand the importance of the TCP/IP protocol suite. Understand the importance of the TCP/IP protocol suite.

OBJECTIVESOBJECTIVES

Understand the role of IP, UDP, and TCP in the Internet. Understand the role of IP, UDP, and TCP in the Internet.

Understand the difference between the Internet, an intranet,Understand the difference between the Internet, an intranet,and an extranet.and an extranet.


Internet History

The internet traces its origins to a military network called ARPANET.

ARPANET was created in response to an increased need for national

security, and the need to connect remote computing resources.

After ARPARET, other private network sprang up , and eventually all

of these networks were connected.

The connection of these networks formed what we call the Internet.

Read the handoutRead the handout


Internet

Terms

1. Internet

2. Packet Switching Network

3. Modem - Modulator/Demodulator


Internet: is the global collection of computers, communication systems, and software.

Public telephone system connects all this equipment to form the internet

Packet Switched Network: On a packet switched network, the data is closed in electronic packet. Each packet is individually addressed and forwarded across the network.

Modem: Modem stands for modulator/demodulator. Modems are used to send data from a computer over the telephone lines.

Computers use digital technology, and the telephone system usually uses analog technology


How the Internet Works

Internet is the Packet Switched Network

• Data sent in packets

• Each packet has an IP address

1. Every computer in the Network has an address called an IP address.

2. IP- Internet Protocol;

3. IP defines the rules of sending communication across the network


1. Internet is the switched network means data sent over internet is

encapsulated in packets

2. The packets are addressed according to their destination

3. Internet database keep track of the addresses and allow

networking equipment to forward packet to the correct computer.

4. This analogy to telephone systems.

Internet is the Packet Switched Network


Basic Internet Architecture


• Peering» ISPs at the same level usually do not

charge each other for exchanging messages

• Higher level ISPs charge lower level ones– National ISPs charge regional ISPs

which in turn charge local ISPs

• Local ISPs charge individuals and corporate users for access

Packet Exchange Charges


Connecting to an ISP

• Done by through ISP’s Point of Presence (POP)– A place ISP provides service to its customers

• Individual users – Typically through a dial-up line using the PPP protocol

• Handled by the ISP’s modem pool– Userid and password checked by Remote Access Server (RAS)

• Once logged in, the user can send packets over the phone line

• Corporate users – Typically access the POP using a T-1, T-3 or ATM

OC-3 connections provided by a common carrier• Cost = ISP charges + circuit charges


Internet today


Technical Focus:Technical Focus: Maturity Levels of an RFCMaturity Levels of an RFC

An RFC, during its lifetime, falls into one of six maturity levels: proposed standard, draft standard, Internet standard, historic, experimental, and informational.


Internet administration


Internet Society

ISOC: Is an international, nonprofit organization formed 1992 to provide support for internet standard process.

ISOC supports other Internet administrative bodies such as IAB, IETF, IRTF and IANA.

ISOC also promotes research and other scholarly activities related to the internet

IAB - Internet Architecture Board

IETF - Internet Engineering Task Force

IRTF - Internet Research Task Force

IANA - Internet Assign Number Authority


TCP/IP protocol suite

IP: handle datagram routing

TCP:is responsible for higher level functions such as segmentation, reassembling, and error detection.


IP datagram


Technical Focus:Technical Focus: Inside the Header of an IP DatagramInside the Header of an IP Datagram

An IP datagram contains several fields. The most important are the source and destination addresses of the datagram (IP addresses). The header also contains fields related to fragmentation. The size of a datagram may be too large for some LAN or WAN protocols. In this case, the datagram is divided into fragments; each fragment carries the same identification number as well as other information to help the receiver assemble the datagram. The header also has two length fields; one defines the length of the header, the other defines the length of the entire packet. One field that can decrease traffic on the Internet holds the number of routers a packet can visit before it is discarded. The header also contains a checksum field to determine the validity of the packet.


IP Address


4.1 INTRODUCTION4.1 INTRODUCTION1.1. The identifier used in the IP layer of the TCP/IP protocol suite to The identifier used in the IP layer of the TCP/IP protocol suite to

identify each device connected to the Internet is called the Internet identify each device connected to the Internet is called the Internet

address or IP address. address or IP address.

2.2. An IP address is a 32-bit address that uniquely and universally An IP address is a 32-bit address that uniquely and universally

defines the connection of a host or a router to the Internet. defines the connection of a host or a router to the Internet.

3.3. IP addresses are unique. They are unique in the sense that each IP addresses are unique. They are unique in the sense that each

address defines one, and only one, connection to the Internet. address defines one, and only one, connection to the Internet.

4.4. Two devices on the Internet can never have the same address. Two devices on the Internet can never have the same address.

Introduction


An IP address is a 32-bit address.

8-bit8-bit 8-bit 8-bit

IP- address is normally written as four decimal number separated by

dots (called dotted - decimal notation)


The address space of IPv4 is232 or 4,294,967,296.


CLASSFUL ADDRESSING

Classful addressing includes the following: Classful addressing includes the following:

• Recognizing ClassesRecognizing Classes

• Netid and HostidNetid and Hostid

• Classes and BlocksClasses and Blocks

• Network AddressesNetwork Addresses

• Sufficient InformationSufficient Information

• MaskMask


Addresses per classAddresses per class


Find the class of each address:

a. 227.12.14.87 b.193.14.56.22 c.14.23.120.8d. 252.5.15.111 e.134.11.78.56

Example 7

Solutiona. The first byte is 227 (between 224 and 239); the class is D.b. The first byte is 193 (between 192 and 223); the class is C.c. The first byte is 14 (between 0 and 127); the class is A.d. The first byte is 252 (between 240 and 255); the class is E.e. The first byte is 134 (between 128 and 191); the class is B.


Netid and hostid


The number of addresses in class C is smaller than the needs of most

organizations.


Class D addresses are used for multicasting; there is only one block in

this class.


Class E addresses are reserved for future purposes; most of the block is

wasted.


In classful addressing, the network address (the first address in the block) is the one that is assigned to the organization. The range of addresses can automatically be inferred from the network address.


Given the network address 17.0.0.0, find the class, the block, and the range of the addresses.

Example 9

SolutionThe class is A because the first byte is between 0 and 127. The block has a netid of 17. The addresses range from 17.0.0.0 to 17.255.255.255.



Example 10

Solution

The class is B because the first byte is between 128 and 191. The block has a netid of 132.21. The addresses range from 132.21.0.0 to 132.21.255.255.



Example 11

SolutionThe class is C because the first byte is between 192 and 223. The block has a netid of 220.34.76. The addresses range from 220.34.76.0 to 220.34.76.255.


Masking concept


AND operation


Default masksDefault masks


The network address is the beginning address of each

block. It can be found by applying the default mask to

any of the addresses in the block (including itself). It

retains the netid of the block and sets the hostid to zero.


Given the address 23.56.7.91, find the beginning address

(network address).

Example

Solution

The default mask is 255.0.0.0, which means that only the first

byte is preserved and the other 3 bytes are set to 0s. The

network address is 23.0.0.0.


Given the address 132.6.17.85, find the beginning address

(network address).

Example

Solution

The default mask is 255.255.0.0, which means that the first 2

bytes are preserved and the other 2 bytes are set to 0s. The

network address is 132.6.0.0.


Given the address 201.180.56.5, find the beginning address (network address).

Example 14

SolutionThe default mask is 255.255.255.0, which means that the first 3 bytes are preserved and the last byte is set to 0. The network address is 201.180.56.0.


Note that we must not apply the default mask of one class to an address

belonging to another class.

Note:Note:


4.3 OTHER ISSUES

In this section, we discuss some other issues that are related to In this section, we discuss some other issues that are related to addressing in general and classful addressing in particular. addressing in general and classful addressing in particular.

The topics discussed in this section include:The topics discussed in this section include:

Multihomed DevicesMultihomed DevicesLocation, Not NamesLocation, Not NamesSpecial AddressesSpecial AddressesPrivate AddressesPrivate AddressesUnicast, Multicast, and Broadcast AddressesUnicast, Multicast, and Broadcast Addresses


Figure 4.12 Multihomed devices


Table 4.3 Special addressesTable 4.3 Special addresses


Figure 4.13 Network address


Figure 4.14 Example of direct broadcast address


Figure 4.15 Example of limited broadcast address


Figure 4.16 Examples of “this host on this network”


Figure 4.17 Example of “specific host on this network”


Figure 4.18 Example of loopback address


Table 4.5 Addresses for private networksTable 4.5 Addresses for private networks


Multicast delivery will be discussed in depth in Chapter 15.

Note:Note:


Table 4.5 Category addressesTable 4.5 Category addresses


Table 4.6 Addresses for conferencingTable 4.6 Addresses for conferencing


Figure 4.19 Sample internet


4.4 SUBNETTING AND SUPERNETTINGIn the previous sections we discussed the problems associated with In the previous sections we discussed the problems associated with classful addressing. Specifically, the network addresses available for classful addressing. Specifically, the network addresses available for assignment to organizations are close to depletion. This is coupled with assignment to organizations are close to depletion. This is coupled with the ever-increasing demand for addresses from organizations that want the ever-increasing demand for addresses from organizations that want connection to the Internet. In this section we briefly discuss two connection to the Internet. In this section we briefly discuss two solutions: subnetting and supernetting.solutions: subnetting and supernetting.

The topics discussed in this section include:The topics discussed in this section include:

SubnettingSubnettingSupernettingSupernettingSupernet MaskSupernet MaskObsolescenceObsolescence


IP addresses are designed with two levels of hierarchy.

Note:Note:


Figure 4.20 A network with two levels of hierarchy (not subnetted)


Figure 4.21 A network with three levels of hierarchy (subnetted)


Figure 4.22 Addresses in a network with and without subnetting


Figure 4.23 Hierarchy concept in a telephone number


Figure 4.24 Default mask and subnet mask


What is the subnetwork address if the destination address is 200.45.34.56 and the subnet mask is 255.255.240.0?

Example 15

SolutionWe apply the AND operation on the address and the subnet mask.

Address ➡ 11001000 00101101 00100010 00111000

Subnet Mask ➡ 11111111 11111111 11110000 00000000

Subnetwork Address ➡ 11001000 00101101 00100000 00000000.


Figure 4.25 Comparison of a default mask and a subnet mask


Figure 4.26 A supernetwork


In subnetting, we need the first address of the subnet and the subnet

mask to define the range of addresses.

In supernetting, we need the first address of the supernet and the

supernet mask to define the range of addresses.

Note:Note:


Figure 4.27 Comparison of subnet, default, and supernet masks


The idea of subnetting and supernetting of classful addresses is

almost obsolete.

Note:Note:


Internet address


Technical Focus:Technical Focus: Classful versus Classless AddressingClassful versus Classless Addressing

With more and more organizations wanting to use the Internet, the Internet authorities are running out of IP addresses. Internet addresses were originally designed as classful addresses. By this, we mean that the total number of 32-bit addresses was divided unevenly into five classes: A, B, C, D, and E. Class A and B contain blocks of addresses with a very large range. Each block is granted to one organization, but most of these organizations never use their allotted number of addresses. This is a tremendous waste of addresses.

Recently, a new design called classless addressing has been implemented. In this design, all available addresses are put into a big pool; each organization is granted a range of addresses according to its need.


Figure 13-6 A part of the Internet


Figure 13-7UDP user datagram


Technical Focus:Technical Focus: Inside a UDP headerInside a UDP header

The header of the UDP datagram is very simple: it contains only four fields. One field defines the application program that has sent the packet (the source), and another defines the application program that is to receive the packet (the destination). Another field defines the length of the entire packet. The last field carries a checksum for error detection.


Figure 13-8TCP segment format


Technical Focus:Technical Focus: Inside a TCP Segment HeaderInside a TCP Segment Header

The header of a segment is very complicated and contains optional as well as mandatory fields. We briefly discuss just the required fields. One pair of fields defines the source and destination application programs. Another pair is used for error and flow control; one holds the unique sequence number, and the other holds the acknowledgment number. One field defines the size of the sliding window in the transport layer. The sliding window in the transport layer uses the same concept as the one in the data link layer (see Chapter 5). There are also flags that define the purpose of the segment (for connection establishment, for termination, for acknowledgment, and so on). The last required field carries a checksum for error detection.


NEXTNEXTGENERATIONGENERATION

NEXTNEXTGENERATIONGENERATION

13.313.3


ACCESS TO THEACCESS TO THEINTERNETINTERNET

ACCESS TO THEACCESS TO THEINTERNETINTERNET

13.413.4


PRIVATE NETWORKS:PRIVATE NETWORKS:INTRANET AND INTRANET AND

EXTRANETEXTRANET

PRIVATE NETWORKS:PRIVATE NETWORKS:INTRANET AND INTRANET AND

EXTRANETEXTRANET

13.513.5


Technical Focus:Technical Focus: Network Address Translation (NAT)Network Address Translation (NAT)

A technology that is related to private networks is network address translation (NAT). The technology allows a site to use a set of private addresses for internal communication and a set of (at least one) global Internet addresses for communication with other sites.

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