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INTERNET-FUNDAMENTALS - TCP/IP Architecture

comunications

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INTERNET-FUNDAMENTALS


Intenet


Today Internet is the fastest and the mostly widely used media for exchange

of information. Internet works on a set of protocols. They are Transport

Control Protocol and Internet Protocol together referred to as TCP/IP.

TCP/IP Architecture

Requirements of layering:

Package the data

Determine the path the data willoll

Transmithe data on a physical medium

Regulate the rate of data transfer according to the available bandwidth

and the capacity of the receiver to absorb

Assemble the incoming data in sequence so that no information is out of

place

Check incoming data for duplicate pieces

Notif he sender of how much of data has been received safely

Handle data to the right appli ion

Handle error or problem events

IP is the protocol for the network layer while TCP is meant for transport layer.

Network Layer-IP

It performs the network layer functions. Its main objective is to effectively

route data between systems. The smallest units, which carry data from one

place to other, are called Datagrams. It is a connectionless protocol since

every datagram is routed independently. Though IP guarantees proper routing

of information it doesnt guarantee transmission of packets in proper order.

Transport Layer TCP

TCP guarantees reliable data connection services to the appli ion. It contains

mechanisms, which guarantee that data is deli ed error free without

omission and in sequence.

Thus both TCP and IP are important for proper and effient functioning of an

Internet.

TCP/IP suite includes

o Program to control communication

o File Transfer Protocol (FTP)

o Simple Mail Transfer Protocol (SMTP)

o Terminal access

o DNS directory services

o Network File System (NFS) <Server and Client>

o uses Remote Procedure Call (RPC)

o Communication program libraries


PING


Telnet


FTP

TCP

ICMP

ARP


SMTP


X


Trace

route

IP

LLC

MAC


DNS


TFTP


BOOTP

UDP

IGMP

RARP


SNM


NFS


TRANSMISSION MEDIA

TCP/IP SUITE


172



W hat is an IP Address?


Intenet


Each host on TCP/IP network is known by a 32-bit address at IP layer. This IP

address specifies the logical location of the host or client on the network.

The conversion of Domain Name to IP address is done by Domain Name

service. DNS is the name to network address translation service.

ADDRESS SCHEME (IPv4):

The IP address is of the form <network ID, host ID>. The address is not

actually separated but read as a whole. The IP address is also called as

protocol address. Two types of addressing schemes exist. They are

- Classful

- Classless

Classful => This type of addressing scheme is mostly employed in customer

sites. It is also the ori nal style of addressing that is based on fist 8 bits of

the address.

Classless => This is a new type of addressing scheme in which class bit of an

address is disregarded and a variable prefi mask) is applied to determine the

network number.

CLASSES OF IP ADDRESSES:

Identifying a class:


A


0


ADDRESS IDENTIFIER

7 bits Network Address


NETWORK ADDRESS


HOST ADDRESS

24 bits Host Address


C


10

110


14 bits Network Address

21 bits of Network Address


16 bits Host Address

8 bits Host Address


D

E


1110

11110


Multicast Address (224.0.0.0-239.255.255.255)

Reserved for future use


Class A address:

Number of networks = 128 (0-127)

Network ID 0 is not used

Network ID 127 is reserved for loop back

Number of networks = 126

Network IDs =1 126

Class B address:

Number of networks = 16384 (0-16383)

Number of hosts = 65,536 (0 65,535)

Host ID 0.0 is not used

Host ID 255.255 is reserved for broadcast purposes

Number of hosts per network = 65,534

Class C address:

Number of networks = 20,97,152 (0-2097151)

Number of hosts = 256 (0 255)

Host ID 00000000 is not used

Host ID 11111111 is reserved for broadcast purposes

Number of hosts per network = 254

Class D & E addresses

These are special addresses and are known as multicast addresses. These are

assigned to a group of networks and not to represent a unique address. This

173



Intenet

address is used to send IP datagrams to a group but not to all hosts on the

network. This address is also used to address router update messages.

MASKS & PREFIXES:

A prefix or a mask is that which slides over the IP address to determine

its IP number. Natural Mask/Default Mask is a network mask that simply

covers network portion of address. A mask and prefix is essenti ly the same

thing.

The addresses 210.10.240.0/24 and 210.10.40.0/255.255.255.0 mean the

same thing.


IP Address

10.2.1.1

130.113.64.16

201.222.5.64

SUBNETTING:


Prefix

/8

/16

/24


Subnet Mask

255.0.0

255.255.0.0

255.255.255.0


Subnetting effiently uses the full network addresses. It provides for another

hierarchy for routing.


RULES:


Internet


130.1.0.0


130.1.1.0

130.1.2.0 130.1.3.0

----------- 130.1.255.0


Subnetting allows assigning some of the bit normally used by the host

portion of the address, to the network portion of the address.

Any of the classes can be subnetted.

The format of the subnetted IP address should be

<network number, subnet number, host number>

Subnet is real network under real network.

With any of the addresses, any number of host bit except for the last

2 bit may be used for Subnetting.

The subnet bits must be contiguous.

All s and 1s in subnet address can be used as a valid address.

Class-B Subnetti


172.16.2.0/24


10101100

172


00010000

Network

16

Network


00000010

2

Subnet


Host


00000000

0

Host


Eight bits of subnetting

Subnetaddresses: 172.16.2.0 (0+0+0+0+0+0+2+0)

Host address: 172.16.2.1-172.16.2.254

B/Cast address: 172.16.2.255

Class-C Subnetti

201.222.5.121/29 11001001 11011110 00000101

Network


01111001


201


222

174


Network


5


120 001



5 bits of Subnetting

Subnet address: 201.222.5.120 (64+32+16+8)

Host address: 1

B/Cast address: 201.222.5.127

Identif ng network address


Intenet


201.222.5.121/29

Subnet Mask

ANDing


11001001

11111111

11001001

201


11011110

11111111

11011110

222

NETWORK


00000101

11111111

00000101

5


01111001

11111000

01111000

120


NATIONAL INTERNET BACKBONE (NIB) &

INTERNET EXCHANGE

Existing Internet setup in INDIA

100 plus Internet nodes (DoT/MTNL, VSNL).

Nodes provided dial-up TCP/IP & shell account Vanilla services. L/L &

ISDN access provided only to certain customers at elected citi

Most of nodes have only Remote Access Servers (RAS).

RAS connected to nearest VSNL gateway node through 2 Mbps links.

VSNL is providing the infrastructure & IP addresses.

Star topology-no redundancy in links and devices.

Need for NIB



Non-availability of access due to capacity constraints.

Inadequate dial up ports. Deficiencies in POP (Point Of Presence)

equipments.

Congestion in the international/national access segment.

Government policy: permission for entries of private ISPs.

Need for a scalable platform.

Star topology-no redundancy in links and devices.

Decision of telecom commission in July 1997: to setup a separate

infrastructure for Internet.

NIB architecture

Its a multi ier structure:

First-Tier: 14 major cities & towns (Type A citi


* Delhi

* Chennai

Hyderabad

Jaipur

Patna


*Mumbai

*Bangalore

Bhopal

Ludhiana

Ahmedabad


*Calcutta

*Pune

Lucknow

Ernakulam


* CITIES WITH INTERNATIONAL GATEWAY (IG)

Second-Tier:31 medium sized towns (Type B Stations)

Third-Tier: 504 small zed towns (Type C Stations)

The following services will be provided by NIB

1.Connecti ty to Internet

E-Mail

FTP

WWW, etc

2.Internet accounts to customers

175



Shell

TCP/IP

Leased Lines

Virtual Private Network (VPN)

3.Customer Access

PSTN dial up access up to 56Kbps

ISDN Dial-Up at BRI (144 Kbps)

X.25 access through net

IP leased lines at 64 Kbps, N*64 Kbps, 2Mbps & 2*N Mbps

Frame Relay (FR)

Asynchronous Transfer Mode (ATM)

4.Private ISP Access Mechanism

Leased line access at 64 Kbps, N*64 Kbps, 2Mbps & 2*N Mbps

A Typical configuration of Mumbai Node


Intenet


Proxy 1&

2

Mail 1& 2


Ethernet Switch


Billing 1& 2


Secured Zone

LAN II


NMS &

APP Work

Station


(10/100

Mbps)

LAN III

Radius 1& 2

De -


Firewall

Server

1&2

ETHERNET Swit

Mbps)

LAN I


Ethernet switch

(10/100

Mbps)

(10/100

GATEWAY ROUTER

AGGREGATION

ROUTER


To IG

Helpdesk

CSU/DSU

Converter

To

A

Node

s with


M ilita riz e d

Symbol shows 2

Servers connected


Login1 &

WWW1


ISP Leased line & Customer

Aggregation

Aggre

Leased Lines,


IG


in Cluster

Configuration

How Does an Internet W ork?


DOTs, A, B, CI,

CII, CIII Nodes Pvt. ISPs


Corporate LANs,

VPNs, X.25 and

FR Customers


An ISP uses its network to move its customers information from

one point to other.

Since the destination need not necessarily be ISPs network.

Hence ISP uses exchange points (IX) to move informati

between networks.

Exchange points enable IPSs to meet growing customer demands

for an effective communication.

No single network can behave as an Internet.

Thus Internet works with efficient & effective co-ordination

between various networks.

Thus, Internet Exchange Points come into picture.

Internet Exchange

Internet Exchange can be termed as a Central Offi and serves as

the highest level of Switching and Peering point in the Internet. Commercial

qualit Xes is the core of Internet. An IX can also be referred to as Network

Access Point (NAP).

176



Intenet

To manage the entire traffic a single IX proves to be highly ineffient,

and hence multi e IXes are required by ISPs for

- Increasing network efficiency [redundancy]

-

- Reduce distance the data must travel [different routes to same

destination]

Successful ISPs are recognized by their connections to major exchanges [e.g.

PAIX, MAE-EAST, MAE-WEST]

INTERNET EXCHANGE


ISP I

CONTENT


ROUER

FOR ISP I


NMMS

SERVER

Private Peering


ROUTER

FOR ISP III


ISP II


SERVERS

(OPTIONAL)


GIGABIT ETHERNET LAYER 2/3

SWITCH

ROUTER FOR


ROUTER

FOR ISP II


R

A

S


ROUTE

REFLECTOR

SERVER


ISP IV


NIB

BACKBONE


ISP III


PSTN


Line Driver


ISP IV

INTERNET


IPv6 ADDRESSING SCHEME:

To comply with the ever-increasing consumer demands technocrats have

worked out a new IP addressing scheme. Salient features of this new

addressing scheme are

It is a 128 bit addressing scheme

Addresses possible are

340282366920938463463374607431768211456

Address is written in hexadecimal

- xxxx.xxxx.xxxx.xxxx.xxxx.xxxx

- eg. FEDC:BA98:7654:3210:4567:234A:EACD:0321

Zeroes can be truncated

- 00FF:0000:0000:0000:0000:9085:9043:1234

- FF::9085:9043:1234

Only one set of zeroes can be truncated

-1080:0000:0000:5698:0000:0000:9887:1234

-1080::5698:0000:0000:9887:1234 or

-1080:0000:0000:5698::9887:1234

The most remarkable feature of this addressing scheme is that the class

wise subnetting will be removed.

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