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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.
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
‹ 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.
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 doesn‘t guarantee transmission of packets in proper order.
Transport Layer œ 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
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
W hat is an IP Address?
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 => 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
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
CLASSES OF IP ADDRESSES:
Identifying a class:
7 bits Network Address
24 bits Host Address
14 bits Network Address
21 bits of Network Address
16 bits Host Address
8 bits Host Address
Multicast Address (126.96.36.199-188.8.131.52)
Reserved for future use
Class œA 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 ID‘s =1 œ126
Class œB address:
° Number of networks = 16384 (0-16383)
° Number of hosts = 65,536 (0 œ 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 œC address:
° Number of networks = 20,97,152 (0-2097151)
° Number of hosts = 256 (0 œ 255)
° Host ID ”00000000‘ is not used
° Host ID 11111111 is reserved for broadcast purposes
° Number of hosts per network = 254
Class œ 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
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
The addresses 184.108.40.206/24 and 220.127.116.11/255.255.255.0 mean the
Subnetting effiently uses the full network addresses. It provides for another
hierarchy for routing.
∑ 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 1‘s in subnet address can be used as a valid address.
· 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
18.104.22.168/29 11001001 11011110 00000101
· 5 bits of Subnetting
· Subnet address: 22.214.171.124 (64+32+16+8)
· Host address: 1
· B/Cast address: 126.96.36.199
Identif ng network address
NATIONAL INTERNET BACKBONE (NIB) &
Internet setup in
· 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)
· 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.
Its a multi ier structure:
First-Tier: 14 major cities & towns (Type A citi
* 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
· WWW, etc
2.Internet accounts to customers
· Leased Lines
· Virtual Private Network (VPN)
· 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*
· Frame Relay (FR)
· Asynchronous Transfer Mode (ATM)
4.Private ISP Access Mechanism
access at 64 Kbps, N*64 Kbps, 2Mbps & 2*
A Typical configuration of Mumbai Node
Mail 1& 2
Billing 1& 2
Radius 1& 2
M ilita riz e d
Symbol shows 2
ISP Leased line & Customer
How Does an Internet W ork?
DOT’s, A, B, CI,
CII, CIII Nodes Pvt. ISP’s
VPNs, X.25 and
· An ISP uses its network to move its customer‘s information from
one point to other.
· Since the destination need not necessarily be ISPs network.
Hence ISP uses exchange points (IX) to move informati
· 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 can
be termed as a —
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).
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
Successful ISPs are recognized by their connections to major exchanges [e.g.
PAIX, MAE-EAST, MAE-WEST]
FOR ISP I
FOR ISP III
GIGABIT ETHERNET LAYER 2/3
FOR ISP II
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
· Address is written in hexadecimal
- eg. FEDC:BA98:7654:3210:4567:234A:EACD:0321
· Zeroes can be truncated
· Only one set of zeroes can be truncated
· The most remarkable feature of this addressing scheme is that the class
wise subnetting will be removed.
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