A

Internship Assessment report

on

“BSNL – NIB AND D-TAX”

At
BHARAT SANCHAR NIGAM LIMITED
(DELHI)

Bachelor of Technology
In
Electronics & Communication Engineering

Submitted by
KAVITA PRAJAPATI (2001430310004)

Of
Department Electronics & Communication Engineering,
IMS Engineering College, Ghaziabad

Dr. A.P.J. Abdul Kalam Technical University, Lucknow

2023-24

pg. 1
 Acknowledgment

With heartfelt thanks, I convey my great obligation to all B.S.N.L

employees, without their support and supervision, this internship would
not have materialized and assumed a proper shape. Mr. Virendra sir
(SDE: D- TAX) , Mrs. Diptee Verma mam(AGM- NIB) my industry
mentor in charge, deserve special recognition for their unwavering support
and cooperation during my training time. I am also grateful to my parents
and teachers for their constant support and encouragement.
I would like to thank the HOD Dr Pramod Kumar and class coordinator
Dr. Balwant Singh for giving
me the opportunity to do an industrial training with BSNL.

Although quite short, for me this was a great experience I can learn from.
This training
period was a wonderful chance of learning and professional development.

KAVITA PRAJAPTI
ECE , FINAL YEAR
(2001430310004)

pg. 2
 Introduction to the company

On September 15, 2000, BSNL was incorporated. It took over the

telecommunication solutions and network management businesses on a going
concern basis from the previous part of Central Government Departments of
Telecom Services and Operations on October 1st, 2000. Exception of Delhi and
Mumbai, the company offers telecommunications services all over India. BSNL is a
government-owned PSU with an earned capital of 1250 million rupees that contains
in equity 500 million rupees and 750 million rupees in preferential shares capital. In
the fiscal year 2020-21, it had a profit of Rs.18,595 crores.

BSNL is a technology-driven integrated telecom service provider that offers a full

range of telecom services, including:
 Wire line services: The huge landline switching network consists of 27,329
exchanges with a capacity of 228.62 lakhs lines and 76.48 lakh consumers.
 GSM mobile services featuring 2G, 3G, 4G: BSNL has practically all of the
cities covered, as well as a significant portion of State Highway, National
Expressways, and Rail Paths. BSNL's Cellular services also give remote
regions with incidental service that are located along major national and state
highways. There are 1131.86 lakh mobile connections out of a total capacity
of 1142.50 lakhs. BSNL has 84,544 2G BTSs, 62,408 3G Node-Bs, and 8,637
e-Node-Bs for 4G technology. In total, 6,272 cities and towns have received
3G mobile service.
pg. 3
  Broadband and Internet connections, including FTTH (fiber to the home).
 Wi-Fi facilities
 In January 2005, BSNL began offering broadband services using ADSL2+
technology. With a total capacity of 100.18 lakh broadband ports, 23.06 lakh
connections are operational. BSNL has provided broadband services to 665
DHQ, 5,996 BHQ, 4,524 Cities, and 1, 71,476 Villages.
 Wi-Fi broadband connections are provided by BSNL. BSNL has a total of
6.09 lakh Wi-Fi users.

 BSNL also offers a variety of Value Added Services to both mobile and
landline clients. Value Added Services is typically a third-party service that is
delivered based on revenue share through a franchisee model.

As a result, the BSNL telecommunication services are a component of a modern

global network that connects countries all over the world to send voice, data, and
video are all ways to send information.

BSNL’s Vision

 To be India's leading telecom service provider.

 Be a consumer’s corporation that excels at customer service and business.
 Make use of technology to offer a wide spectrum of customers low-cost,
innovative telecom services and goods.

pg. 4
BSNL’s current objectives

 Become the most admired, trusted, and chosen telecom brand.

 Providing cost-effective and dependable telecom services.
 Creating value for all parties involved like stakeholders, including employees,
shareholders, vendors, and partners.
 Using Next Generation Networks to remove conventional wire line exchanges
and creating Wi-Fi hotspots.
 Fiber to the home is being utilized to expand the reach of the fiber network
near to address bandwidth requirements on customer premises, particularly in
residential complexes requirements for both data and video applications.
 BSNL's current infrastructure will be used to aid in the implementation of
government projects and initiatives such as the National Optical Fiber
Network (NOFN), Network for Spectrum (NFS), and the Smart City idea.
To become the government's preferred service provider for a service network that is
stable and secure, as well as to support national security needs.

Description of the allotted work

During my internship at BSNL Janpath (Delhi) I was introduced to various telecom
services being provided by the company which is a Government of India enterprise
in Telecom business. I was assigned to an SDE level officer who used to oversee
my work and guide me from time to time. As BSNL has layered structure and
various fields are subdivided into the sections based upon the basic telecom service
they provide, I was assigned to these sections namely National Internet Backbone
pg. 5
(dealing with various network connection) from 5.07.2023 to 7.07.2023 &
24.07.2023 to 28.07.2023, and D- TAX (10.07.2023 to 21.07.2023).

The description of the works executed is provided as below.

NIB (National Internet Backbone) Section :-

Here I was introduced with the OTN which are present for the purpose of
providing fastest and largest networks which are linked together with fiber optic
connections and high performance routers deployed by BSNL. There I learnt about
fiber connections, router and various terms used in networking. Initially I was
introduced to these aspects of the network which augmented my college learning
and I could put, the things I learnt at the college, to test in practical scenario like
how the network really works, how is it deployed, how the connectivity actually
looks like and its basic architecture. I worked on the reports the section prepares
daily to monitor the health of the network. Based upon these fault analysis and
diagnosis was carried out and if the need so arises, we have check the connections
and the wiring of the connectivity.

D- TAX section:

pg. 6
BSNL has vase network of Underground Copper cables which are used to provide
the landline connectivity to the general customers. This constituted the legacy
telecom system of the department and BSNL provides basic telephony, Lease lines
over Cu pairs, ADSL broadband, PRI connectivity over this network. In this section
we learn about how the call flow, servers, soft switches and their connectivity
throughout the north India and about the trunk media gateway.
A.C and D.C batteries set was to provide power back up to the network, the
Telecom switching equipment called Telephone exchange in general terms, its
various components and parts. I was taught about the call setup scenarios and the
processes / components involved at various stages and in various scenarios like
local calls, outbound calls, inter exchange calls, landline to mobile network calls
and vice versa. I worked on how on the connections and check if all the traffics
were properly working or not. I also worked on the part to check the working of the
E1 and its channels.

Details of work done during training

pg. 7
In NIB sections

In NIB section, I worked in OTN ( Optical Transport Networking) and

routing.
An optical transport network (OTN) is a digital wrapper that encapsulates frames
of data, to allow multiple data sources to be sent on the same channel. This creates
an optical virtual private network for each client signal.
Here I learned about few terms like about IP Addressing, topologies which we used
in networking, OSI model, different types of ports and their uses.

IP ADDRESS
An Internet Protocol (IP) address is a unique numerical identifier for every device
or network that connects to the internet. There is a direct relationship between the
value of the Internet and the number of sites connected to the Internet. Over the past
few years, the Internet has experienced two major scaling issues as it has struggled
to provide continuous and uninterrupted growth. In order to provide the flexibility
required to support different size networks, the designers decided that the IP address
space should be divided into three different address classes - Class A, Class B, and
Class C. This is often referred to as "classful" addressing because the address space
is split into three predefined classes, groupings, or categories. Each class fixes the
boundary between the network-prefix and the host-number at a different point
within the 32-bit address.
Class A Networks (8 Prefixes)
Each Class A network address has an 8-bit network-prefix with the highest order bit
set to 0 and a seven-bit network number, followed by a 24-bit host-number. Class
A networks are now referred to as "/8s" since they have an 8-bit network-prefix. A
maximum of 126 (27 -2) /8 networks can be defined. The calculation requires that
the 2 is subtracted because the /8 network 0.0.0.0 is reserved for use as the default
route and the /8 network 127.0.0.0 (also written 127/8 or 127.0.0.0/8) has been
reserved for the "loopback" function

Class B Networks (/16 Prefixes)

Each Class B network address has a 16-bit network-prefix with the two highest
order bits set to 1-0 and a 14-bit network number, followed by a 16-bit host-
number. Class B networks are now referred to as"/16s" since they have a 16-bit
pg. 8
network-prefix .A maximum of 16,384 (214 ) /16 networks can be defined with up
to 65,534 (216 -2) hosts per network.

Class C Networks (/24 Prefixes)

Each Class C network address has a 24-bit network-prefix with the three highest
order bits set to 1-1-0 and a 21-bit network number, followed by an 8-bit host-
number. Class C networks are now referred to as "/24s" since they have a 24-bit
network-prefix. A maximum of 2,097,152 ( 221 )/24 networks can be defined with
up to 254 (28 -2) hosts per network.
SUBNETTING
Sub netting attacked the expanding routing table problem by ensuring that the
subnet structure of a network is never visible outside of the organization's private
network. The route from the Internet to any subnet of a given IP address is the
same, no matter which subnet the destination host is on. Sub netting overcame the
registered number issue by assigning each organization one (or at most a few)
network number(s) from the IPv4 address space. The router accepts all traffic from
the Internet addressed to network 130.5.0.0, and forwards traffic to the interior sub
networks based on the third octet of the classful address. The deployment of sub
netting within the private network provides several benefits: The size of the global
Internet routing table does not grow because the site administrator does not need to
obtain additional address space and the routing advertisements for all of the subnets
are combined into a single routing table entry. The local administrator has the
flexibility to deploy additional subnets without obtaining a new network number
from the Internet. Route flapping (i.e., the rapid changing of routes) within the
private network does not affect the Internet routing table since Internet routers do
not know about the reachability of the individual subnets - they just know about the
reachability of the parent network number. Extended-Network-Prefix Internet
routers use only the network-prefix of the destination address to route traffic to a
sub netted environment. Routers within the sub netted environment use the
extended-network- prefix to route traffic between the individual subnets. The
extended-network-prefix is composed of the classful network-prefix and the subnet-
number.

pg. 9
Topology

Topology defines the structure of the network of how all the components are
interconnected to each other. There are two types of topology: physical and logical
topology.
Physical topology is the geometric representation of all the nodes in a network.
There are six types of network topology which are Bus Topology, Ring Topology,
Tree Topology, Star Topology, Mesh Topology, and Hybrid Topology.
Bus Topology

fig. 1(Bus Topology)

The bus topology is designed in such a way that all the stations are connected
through a single cable known as a backbone cable. Each node is either connected to
the backbone cable by drop cable or directly connected to the backbone cable.
When a node wants to send a message over the network, it puts a message over the
network. All the stations available in the network will receive the message whether
it has been addressed or not. The bus topology is mainly used in 802.3 (ethernet)
and 802.4 standard networks. The configuration of a bus topology is quite simpler
as compared to other topologies. The backbone cable is considered as a "single
lane" through which the message is broadcast to all the stations.

pg. 10
Ring Topology

Fig 2(Ring Topology)

If all the nodes in a communication network are cascaded with no node open, a ring
network is formed. If the first and last open nodes of a line network are connected, a
ring network is formed. In a ring network, to connect two nodes, all the nodes
between them should be connected. The best advantage of this network topology is
its strong survivability, which is of vital importance to a modern high-capacity
optical fiber network. Therefore, special importance is attached to a ring network in
an SDH network. Ring architectures are often preferred in practice because of their
simpler and faster switching mechanism.

Mesh Topology

If many nodes in a communication network are directly interconnected, a mesh

topology is formed. If all the nodes are directly interconnected, such mesh topology
is called an ideal one. In a non-ideal mesh topology, any two nodes not connected
directly with each other can be connected via the connection function of other
nodes. The mesh structure is not influenced by the problems of node bottleneck and
failure and there are multiple optional routes between two nodes. It has a high
reliability, but a complex structure and high costs. Therefore, it is applicable to a
backbone network with heavy traffic.
In a word, all these topology structures have their own features and can be applied
in a network to different degrees. What network topology to be selected depends on
many factors. For instance, a network should be of high survivability and easy to
configure, and the net architecture should be suitable for the introducing of new
pg. 11
services. The different parts of an actual network are applicable to different
topology structures. For instance, ring topology and star topology structures are
very applicable to a local network (namely, an access network or user network),
with a line topology structure sometimes used. Ring topology and line topology are
very applicable to a local interchange relay network while a toll network may
demand mesh topology.

Fig 3 (Mesh Topology)

Tree topology

This topology has a hierarchical flow of data. In Tree Topolog, protocols like
DHCP and SAC (Standard Automatic Configuration) are used. The various
secondary hubs are connected to the central hub which contains the repeater. This
data flow from top to bottom i.e. from the central hub to the secondary and then to
the devices or from bottom to top i.e. devices to the secondary hub and then to the
central hub. It is a multi-point connection and a non-robust topology because if the
backbone fails the topology crashes. It allows more devices to be attached to a
single central hub thus it decreases the distance that is traveled by the signal to
come to the devices.
It allows the network to get isolated and also prioritize from different computers.

pg. 12
 Fig. 4 (Tree
Topology)
Star Topology

In Star Topology, all the devices are connected to a single hub through a cable.
This hub is the central node and all other nodes are connected to the central node.
The hub can be passive in nature i.e., not an intelligent hub such as broadcasting
devices, at the same time the hub can be intelligent known as an active hub. Active
hubs have repeaters in them. Coaxial cables or RJ-45 cables are used to connect
the computers. In Star Topology, many popular Ethernet LAN protocols are used
as CD(Collision Detection), CSMA (Carrier Sense Multiple Access), etc.
If N devices are connected to each other in a star topology, then the number of
cables required to connect them is N. So, it is easy to set up.
Each device requires only 1 port i.e. to connect to the hub, therefore the total
number of ports required is N.
It is Robust. If one link fails only that link will affect and not other than that.
Easy to fault identification and fault isolation.
Star topology is cost-effective as it uses inexpensive coaxial cable.

Fig. 5 (Mesh Topology)

pg. 13
Multi-Protocol Label Switching (MPLS)

Multi-Protocol Label Switching (MPLS) is a data-carrying mechanism in packet-

switched networks and it operates at a TCP/IP layer that is generally considered to
lie between traditional definitions of Layer 2 (data link layer) and Layer 3 (network
layer or IP Layer), and thus is often referred to as a "Layer 2.5" protocol. It was
designed to provide a unified data-carrying service for both circuit-based clients and
packet-switching clients, which provide a datagram service model. It can be used to
carry many different kinds of traffic, including IP packets as well as native ATM,
SONET, and Ethernet frames. The Internet has emerged as the network for
providing converged, differentiated classed of services to user with optimal use of
resources and also to address the issues related to Class of service (CoS) and
Quality of Service (QoS). MPLS is the technology that addresses all the issues in
the most efficient manner.
MPLS is a packet-forwarding technology that uses labels to make data forwarding
decisions. With MPLS, the Layer 3 header analysis (IP header) is done just once
(when the packet enters the MPLS domain).
Functions of MPLS:-
1. Specifies mechanisms to manage traffic flow of various granularities, such as
flows between different hardware, machines, or even flows between different
applications.
2. Remains independent of the Layer-2 & layer-3 protocols.
3. Provides a means to map IP addresses to simple, fixed-length labels used by
different packet-forwarding and packet-switching technologies
4. Interfaces to existing routing protocols such as resource reservation protocol
(RSVP) and open shortest path first (OSPF).
5. Supports the IP, ATM, and frame- relay Layer-2 protocols
Operation of MPLS:-
The following steps must be taken for a data packet to travel through an MPLS
domain. Label creation and distribution, Table creation at each router, Label-
switched path creation, Label insertion/table lookup and Packet forwarding. The
source sends its data to the destination. In an MPLS domain, not all of the source
traffic is necessarily transported through the same path. Depending on the traffic
pg. 14
characteristics, different LSPs could be created for packets with different CoS
requirements.

Data flow

LER2

LSR2
LER1 LSR1 LER4
LSR3

LER3

Label distribution
Label request

Fig. 6
(MPLS

MPLS Application:-

MPLS addresses today’s network backbone requirements effectively by providing a

standards-based solution that accomplishes the following:
1. Improves packet-forwarding performance in the network
2. MPLS enhances and simplifies packet forwarding through routers using
Layer-2 switching paradigms.
3. MPLS is simple which allows for easy implementation.
4. MPLS increases network performance because it enables routing by switching
at wireline speeds.
5. Supports QoS and CoS for service differentiation
6. MPLS uses traffic-engineered path setup and helps achieve service-level
guarantees.
7. MPLS incorporates provisions for constraint-based and explicit path setup.
8. Supports network scalability
9. MPLS can be used to avoid the N2 overlay problem associated with meshed
IP – ATM networks.
pg. 15
 10. Integrates IP and ATM in the network
11. MPLS provides a bridge between access IP and core ATM.
12. MPLS can reuse existing router/ATM switch hardware, effectively
joining the two disparate networks.
13. Builds interoperable networks
14.MPLS is a standards-based solution that achieves synergy between IP and
ATM networks
Advantages of MPLS over other technologies

BSNL's primary objectives in setting up the BGP/MPLS VPN network are:

1. Provide a diversified range of services (Layer 2, Layer 3 and Dial up VPNs) to
meet the requirements of the entire spectrum of customers from Small and
Medium to Large business enterprises and financial institutions.
2. Make the service very simple for customers to use even if they lack experience
in IP routing.
3. Make the service very scalable and flexible to facilitate large-scale deployment.
4. Provide a reliable and amenable service, offering SLA to customers.
5. Capable of meeting a wide range of customer requirements, including security,
quality of Service (QOS) and any-to-any connectivity.
6. Capable of offering fully managed services to customers.
7. Allow BSNL to introduce additional services such as bandwidth on demand etc
over the same network.

Main Distribution Frame

To obtain flexibility in interconnecting, external line plants and the exchange

equipment and between different circuits in the exchange itself, certain
arrangements is made by the use of iron frames. These iron frames are called main
distribution frames, intermediate distributions frames or combined main and
intermediate distribution frames, depending upon their functions.
The subscriber’s lines enter an exchange through a number of large capacity
cables, each of which serves a different part of the exchange area. The numbers
pg. 16
given to the subscriber’s lines do not bear any relationship to the geographical
location of the subscriber. Hence the exchange numbers include in any one cable
are entirely haphazard .Moreover, as subscribers cease to have telephones and new
subscribers are connected, the exchange numbering of the external cable pairs is
constantly changing. On the other hand, all lines within the exchange are in strict
numerical order. It is, therefore, necessary that some means must be provided for
temporary connection between the two. This conversion from the geographical
order of the external pairs to the numerical order within the exchange is carried out
on a main distribution frame

Fig. 7
In D-TAX sections (MDF)

In D-tax section I worked further in two different types of sections: - In D Tax and
another one is IP tax.
pg. 17
Here in both the sections I learned various terms of telecommunication sector. In
this section I go through the whole procedure of making a call whether it’s a
national or international call.

SSTP (Standalone Signaling Transfer Point)

By the name it indicates that it is used to transfer the signaling between two
different points.
The Stand Alone Signaling Transfer Point (SSTP) is a digital system used in the
telecommunication network for transfer of signaling data between
telecommunication system (mobile exchanges, local exchanges, trunk exchanges
etc.).
The SSTP system acts as a transit system for the transfer of signaling data from one
location to a distant location through defined transmission network.
As the numbers of nodes are growing, the routing is also increasing exponentially.
If the management of the routing is to be done on these individual nodes, the
complexity increases accordingly, which also mean the increased chances of error
& hence losing the revenue. The SSTP enabling the uniform signaling in SS7
domain provided a single routing database, which is managed centrally. This
routing database is able to make the routing decision based on the destination point
codes (DPC), global title translation (GTT), etc. For reliability reasons, SSTPs are
nearly always deployed in mated pairs.

Fig. 8
Need of SSTP:- (SSTP)

The efficiency of SS7 had made a numbers of applications possible in GSM world.
As the size of the network grew, it became more and more difficult to manage the
pg. 18
direct SS7 links between the switches and from switches to other network elements
like HLR, SMSC, SCPs etc . This capability also offloaded some of the processing
power required in the L-1 TAX and all switches could breathe easier.
The introduction of Standalone Signal Transfer Point (SSTP) was a historic step
from that perspective & able to handle the signaling very efficiently.
The SSTP suddenly became the vantage point in the network because of the simple
reason that the signaling protocol was common.
SSTP also handle the non-call related messages efficiently. These messages exist in
all the technology and may not be needed to be hand by a switch. Many times these
will actually involve multiple technologies and in absence of the uniform signaling
layer, the complexity increase many fold.
The SSTP, enabling the uniform signaling in SS7 domain, provided a single routing
database, which is managed centrally. This routing database is able to make the
routing decision based on the destination point codes (DPC), global title translation
(GTT), routing keys etc.
When any mobile subscriber of a private operator roams into service area of other
operator (say BSNL), the signaling traffic or SMS are being handled by signaling
channel of BSNL taken by private operator against the POI. BSNL was not able to
measure the traffic and it was also not known about the type of signaling traffic. To
measure and know type of signaling traffic, SSTP was planned and installed so that
billing to private operators can be done accordingly. Due to reasons explained
above, BSNL decided to have a separate signaling network by installing a number
of SSTPs at various locations.

Functions of SSTP:-
1. SS7 Message routing
2. SS7 Network Management
pg. 19
 3. Global Title Translation(GTT)
4. Gateway Function
5. Gateway Screening(GWS)
6. Mobile Number Portability(MNP)
7. Equipment Identity Register
Basic Architecture of SSTP

Fig. 9
(Architectu

SS7 or CCS7

In CCS there is a common signaling channel which takes care of all the signaling
information to be exchanged during communication. All other channels can be used
for speech or data as required.
Signaling System 7 (SS7) is architecture for performing out of band signaling in
support of the call- establishment, billing, routing and information-exchange
functions of the public switched telephone network (PSTN). It identifies functions
to be performed by a signaling-system network and a protocol to enable their
performance.
pg. 20
 Fig.
10(SS7)

SS7 layer wise function

MTP Level 1(Message Transfer Protocol)

MTP1 is at the physical layer. The 1st level defines the physical, electrical, and
functional features of the signaling data link.

MTP Level 2
MTP-2 ensures accurate end-to-end transmission of a message across a signaling
link. MTP Level 2 implements flow control, message sequence validation, and error
checking. When an error occurs on a signaling link, the message is retransmitted.

MTP Level 3
MTP3 provides routing of signaling messages between signaling points. All
network elements that have an MTP3 instance are provided with a numeric SS7
address called a Point Code(PC) which is used for routing the signaling messages.
In case of congestion or failed links, the MTP3 layer is responsible for congestion
control & re-routing of the signaling messages.

SCCP(Signalling Connection Control Protocol)

SCCP is a part of the network layer together with MTP3 & enhances the MTP
protocol with two main features:
1.Subsytem Number(SSN)
2.Global Title Translation(GTT)

TCAP(Transaction Capabilities Application Protocol)

TCAP is a connection less protocol that runs on top of SCCP. It executes operation
at remote nodes & receives the results from these process.
pg. 21
Ex: Mainly used to filter the messages having same Transaction ID.
Provides services to
INAP (IN Application Part)
MAP (Mobile Application Part)

ISUP(ISDN User part)

ISUP provides the signalling procedures used to set-up, manage & release voice &
data calls over the PSTN. It reserves trunk circuits between signalling points and
later releases them when user terminates the call.

Concept of NGN

Next Generation Network (NGN) refers to a packet based network and it can be
used for both telecommunication services as well as data and it supports mobility. It
is able to make use of multiple broadband capabilities; especially Quality of Service
(QoS) enabled transport technologies where the service related functions are
independent of the underlying transport related technologies.
The main goal of Next Generation Network is to serve/ work as an replacement of
Public Switched Telephone Network (PSTN) and Integrated Service Digital
Network(ISDN)

Fundamental Characteristics for defining NGN:

 Packet based transfer
 Separation of control functions for bearer capabilities , call/sessions- service.
 Decoupling of service and network and provision of open interface(I/F).
 A wide range of services like (Real time (RT)/streaming/non real
time(RT)/multimedia)
 Internetworking with legacy networks via open I/F.
 Support of Generalized mobility.
 Support to unrestricted access by users to different service providers.
Layers of Next Generation Network

 In Access Layer, different types of media gateways that support connection to

and from access network with the core network are included.

pg. 22
 Core network layer is network handling converged services based on Internet
Protocol (IP). Control layer works as call server. It provides call control
functions also provides control of a media gateway.
 Service layer is an IT platform that creates a service creation environment
extending its functionality in order to cover new network scenarios as an
intelligent network.

Fig.
11( NGN

Architecture of NGN

pg. 23
pg. 24
 Fig. 12
(Architectu

SIP( Session Initiation Protocol)

The Session Initiation Protocol is a signaling protocol used for initiating,

maintaining, and terminating communication sessions that include voice, video and
messaging applications. SIP is used in Internet telephony, in private IP telephone
systems, as well as mobile phone calling over LTE . The protocol defines the
specific format of messages exchanged and the sequence of communications for
cooperation of the participants. SIP is a text-based protocol, incorporating many
elements of the Hypertext Transfer Protocol (HTTP) and the Simple Mail Transfer
Protocol (SMTP).[3] A call established with SIP may consist of multiple media
streams, but no separate streams are required for applications, such as text
messaging that exchange data as payload in the SIP message.
SIP works in conjunction with several other protocols that specify and carry the
session media. Most commonly, media type and parameter negotiation and media
setup are performed with the Session Description Protocol (SDP), which is carried
as payload in SIP messages. SIP is designed to be independent of the
underlying transport layer protocol and can be used with the User Datagram
Protocol (UDP), the Transmission Control Protocol (TCP), and the Stream Control
Transmission Protocol (SCTP). For secure transmissions of SIP messages over
insecure network links, the protocol may be encrypted with Transport Layer
Security (TLS). For the transmission of media streams (voice, video) the SDP
payload carried in SIP messages typically employs the Real-time Transport
Protocol (RTP) or the Secure Real-time Transport Protocol (SRTP).
.

pg. 25
 Fig.
13(SIP)

SIP request message:-

o REGISTER: Used by a user agent to register to the registrar (SIP server).
o INVITE: Used to establish a media session between user agents.
o ACK: Confirms reliable message exchanges.
o CANCEL: Terminates a pending request.
o BYE: Terminates an existing session.

SIP response messages:-

 Provisional (1xx): Request received and being processed.

 100 Trying, 180 Ringing, 183 Session in Progress.
 Success (2xx): The action was successfully received, understood, and
accepted.
 200 OK.
 Client Error (4xx): The request contains bad syntax or cannot be fulfilled
at the server.
pg. 26
  401 Unauthorized.
 Global Failure (6xx): The request cannot be fulfilled at any server.
 604 Does Not Exist Anywhere.

REAL TIME PROTOCOL

A protocol is designed to handle real-time traffic (like audio and video) of the
Internet, is known as Real Time Transport Protocol (RTP). RTP must be used
with UDP. It does not have any delivery mechanism like multicasting or port
numbers. RTP supports different formats of files like MPEG and MJPEG. It is very
sensitive to packet delays and less sensitive to packet loss.
Applications of RTP:-
1. RTP mainly helps in media mixing, sequencing and time-stamping.
2. Voice over Internet Protocol (VoIP)
3. Video Teleconferencing over Internet.
4. Internet Audio and video streaming.

Fig.
14(Real
Time

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 Fig . 15
(RTP

RTP Control Protocol (RTCP) is used in conjunction with RTP to send information
back to the sender about the media stream. RTCP is primarily used for the client to
send quality of service (QoS)data, such as jitter, packet loss and round-trip time
(RTT). The server may use this information to switch to a different codec or stream
quality. This data can also be used for control signaling or to collect information
about the participants when many are connected to the stream .RTP does not define
specific codecs or signaling and uses other standards for data types. It can use
several signaling protocols such as session initiation protocol (SIP), H.323 or
XMPP. The multimedia can be of almost any codec, including G.711, MP3, H.264
or MPEG-2.Secure real-time transport protocol (SRTP) adds encryption to RTP. It
can be used to secure the media stream so that it cannot be deciphered by others

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CONCLUSION

To summarize, this internship was a wonderful and rewarding experience. I can

confidently say that my stint at BSNL guided me a lot. Needless to say, the
technical aspects of my work are not ideal and might be improved with more time.
Since I had no prior experience in the topic of practical communication systems, I
trust that the time I spent researching and learning and understanding consumer
demands it was all well worth it, as it enabled me to find a good answer to any day-
to-day difficulty that a firm would have in the communication domain. Two of the
most significant lessons I've learned are time management and self-motivation.
There were times when dealing with customers was challenging, but Pradeep sir,
Ram Niwas sir, and Navdeep sir were constantly by my side to point out my flaws
and how to correct them in the future internship process. It was a proud feeling to
be part most oldest telecommunication industry in India.

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