Internship Report

OMC

(Operation & Maintenance Center EWSD HYD)

Group Members:1

NAMES DEPARTMENT, UNIVERSITY

Syed Saad Mehdi Second year, Electrical Engineering, MUET, Jamshoro

Zeeshan Hyder Final year, Telecom, Sindh University

Habibullah Dars Final year, Telecom, Sindh University

Najaf Ali Shah Final year, Telecom, Sindh University

Irshad Hussain Tunio Final Year, IT, Sindh Agricultural University, Tandojam

Syed Tariq Shah Final Year, IT, Sindh Agricultural University, Tandojam

Submitted to: Madam Quratulain Bhatti

Submitted on: 09/7/12

Table of Content

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1. General information.......................................................................1

1.1 Introduction............................................................................................1

1.2 Historical Background ..........................................................................1

1.3 Vision.......................................................................................................2

2. Operation and Maintenance Center (OMC)...............................2

2.1 Operation Departments........................................................................3

2.2 Operation And maintenance Center....................................................3

2.3 Purpose of Working at the OMC........................................................4

3. Exchange.........................................................................................5

3.1 Types Of Exchange.................................................................................5

3.2 Local Exchange.......................................................................................5

3.3 Transit Exchange....................................................................................6

3.4 Combined Exchange..............................................................................6

3.5 Gateway Exchanges................................................................................6

3.6 Remote Exchangs...................................................................................7

3.7 RLDU.......................................................................................................8

3.8 OMC connection with exchanges..........................................................9

4. Optical Fiber Access Network (OFAN).........................................11

4.1 Optical Fiber Communication...............................................................11

4.2 Optical Line Terminal (OLT)................................................................12

4.3 Optical Network Unit (ONU)................................................................12

4.4 OFAN (Optical Fiber Access Network).........................................14

5. Signaling System No. 7.......................................................................16

5.1 Common Channel Signaling (CSS)......................................................17

5.2 Channel Associated Signaling (CAS)....................................................18

5.3 Signaling modes......................................................................................19

6. Conclusion ……………………………………………………………20

1. General Information:

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1.1 Introduction:

PTCL (Pakistan Telecommunication Limited) is one of the largest employers in the country with its work all over the country to provide an essential service to the people of Pakistan.. The Company consists of around 2000 telephone exchanges across country providing largest fixed line network. Pakistan Telecommunication Company Limited (PTCL) is thePakistan's most reliable and largest converged services carrier, which provides all telecommunications services from basic voice telephony to data, internet, video-conferencing andcarrier services to consumers. PTCL intends to be the leading ICT provider in the region by achieving customer’s satisfaction and maximizing shareholders’ value and as such PTCL perceives its future as a costumer centric organization enhancing its infrastructure and investing in people. Moreover its collaboration with the two mojar telecommunication sectors of world namely Hauwei and ZTE has blessed it with the latest technology.

2.2 History

From the beginnings of Posts & Telegraph Department in 1947 and establishment of Pakistan Telephone & Telegraph Department in 1962, PTCL has been a major player in telecommunication in Pakistan. Despite having established a network of enormous size, PTCL workings and policies have attracted regular criticism from other smaller operators and the civil society of Pakistan..

Pakistan Telecommunication Corporation (PTC) took over operations and functions from Pakistan Telephone and Telegraph Department under Pakistan Telecommunication Corporation Act 1991. This coincided with the Government's competitive policy, encouraging private sector participation and resulting in award of licenses for cellular, card-operated pay-phones, paging and, lately, data communication services.

Pursuing a progressive policy, the Government in 1991, announced its plans to privatize PTCL, and in 1994 issued six million vouchers exchangeable into 600 million shares of the would-be PTCL in two separate placements.

In 1995, Pakistan Telecommunication (Reorganization) Ordinance formed the basis for PTCL monopoly over basic telephony in the country. The provisions of the Ordinance were lent permanence in October 1996 through Pakistan Telecommunication (Reorganization) Act. The same year, Pakistan

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Telecommunication Company Limited was formed and listed on all stock exchanges of Pakistan

PTCL launched its mobile and data services subsidiaries in 2001 by the name of Ufone and PakNet respectively. None of the brands made it to the top slots in the respective competitions. Lately, however, Ufone had increased its market share in the cellular sector. The PakNet brand has effectively dissolved over the period of time. Recent DSL services launched by PTCL reflects this by the introduction of a new brand name and operation of the service being directly supervised by PTCL.

1.3 Vision

To be the leading Information and Communication Technology Service Provider in the region by achieving customer satisfaction and maximizing shareholders' value'.

The future is unfolding around us. In times to come, we will be the link that allows global communication. We are striving towards mobilizing the world for the future. By becoming partners in innovation, we are ready to shape a future that offers telecom services that bring us closer.

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2. Operation and Maintenance Center:

2.1 Operation Departments:

The aim of operation department is the overall management and general administration of the core operations of the company. This department keeps a check on the personnel, legal matters and regular operations of the company.

Following are the three main departments present in this building of Central Exchange PTCL.

Multimedia and Broadband Department . Transmission Department. Operation and Maintenance Center.

2.2 Operation & Maintenance Centre OMC:

An Operations and Maintenance Center is the central location to operate and maintain the network. The OMC forms a central function for controlling and supervising the other network elements as well as monitoring the quality of

all the services provided by the network. 

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OMC

HYBD CxMPK Cx

MDFOperations Department

Figure 1. Connectivity of OMC with Exchanges.

HCEN3 Lx

Media Transmission

OMC Hyderabad controls local as well as transit Exchanges of Mirpur Khas, Sukkhar and Central-III EWSD MSU Hyderabad. Hence it acts to work as a combined exchange.

2.3 Purpose:

Here are some main reasons due to which the functionality of an OMC Operating and maintenance department is purposeful to the fault free system.

Fault detection and its clearance.

Security Management.

Network configuration, Operation and Performance Management.

Maintenance Tasks.

Safe handling of exchanges through servers placed within the OMC.

Database Management.

All the above-mentioned functions are accomplished through Net Manager Client terminal placed within the OMC. The operator log into the database of particular exchange and perform these tasks.

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3. Exchange:

In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls. A central office (CO) is the physical building used to house inside plant equipment including telephone switches, which make telephone calls "work" in the sense of making connections and relaying the speech information. The term exchange area can be used to refer to an area served by a particular switch.

3.1 Types of Exchanges:

Following are the types of Exchanges Telecommunication.

Local Exchanges

Transit Exchanges

Combined Exchanges

Gateway Exchanges

Remote Exchanges

3.2 Local Exchange:

There may also be exchanges which only transfer traffic between the local exchanges, and which thus lack the ability to switch upwards in the hierarchy. Such an exchange is called a local transit exchange.

(Local calling areas, in which it is not necessary to pay a long-distance rate, typically cover more than one rate center even in small metropolitan areas.) The exchange code or central office code (often called the prefix by the public) refers to the first three digits of the local number (NXX), though most non-rural exchanges have more than one code or prefix.

Local subscriber’s international call route is shown in the fig

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3.3 Transit Exchange:

A Transit Exchange does nothing but transfers traffic between sub-ordinate exchanges in the network and to those further up in the network hierarchy.

At node points in the telephone network transit exchanges connect together trunks to and from other exchanges up to 60,000 incoming outgoing or both trunks can be connected to EWSD transit or long distance exchanges.

3.4 Combined Exchange OR Local/Transit Exchange:

These exchanges handle transit or long distance traffic as well as incoming and outgoing local traffic. Any number of subscriber lines and trunks can be combined within the maximum traffic handling capabilities of the exchange.

RLU remote line unit subscriber’s call is forwarded to this exchange directly after the verification from RLU, it depends whether it is a combined or local and transit exchange separate.

3.5. Gateway Exchange:

A gateway exchange or more rightly an international gateway exchange is a telephone switch that forms the gateway between a national telephone network and one or more other international gateway exchanges, thus providing cross-border connectivity.

A voice gateway is a device that allows you to use your broadband Internet to make and receive a high-speed telephone call rather than using a regular analog phone.

An international gateway exchanges are commonly implemented using hardware that could also serve to build a Class 4 (national transit) switch, some of the differences between an international gateway exchange and a Class 4 switch include: International variants of signaling protocols, such as International ISUP and, in addition to the relevant national signaling protocols. Support for echo cancellers. Support for DCME Support for international accounting and settlement agreements. Support for A-law /mu-law transcoding High capacity

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(some of the largest telephone exchanges in the world are international gateway exchanges). Support for the numbering plans of each of the countries.

3.6 Remote Exchange:

It’s a small unit placed in a remote or rural area where there is no influential traffic of subscribers for Telephonic calls or the use of Broadband

In this regard instead of placing a large exchange a small unit is installed which is controlled by the local exchange through a server placed within the OMC operation and maintenance centre of the PTCL Building.

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Figure 2: Path of an International Call

RDLURemote Digital Line Unit:

The Remote Digital Line Unit (RDLU) provides the ability to locate the port sections of the switching system at a remote site. It can be equippedwith its own batteries and chargers and can be located up to 30 miles from theswitching equipment. The RDLU is designed to operate in hostile ambienttemperature environments, so installation in an equipment closet is acceptable.The RDLU is an economically sound way to avoid cable access nightmaresand reduce the overall footprint of the switching system for large installationsand campus environments. There are no limitations to the number of RDLUs that can be equipped and supported, up to the maximum system size. Each RDLU requires only fiber optic or microwave connectivity. The RDLU and the switching equipment use many of the same circuit boards, providing easy access to spare parts.In the diagram below, the RLDU Network is explained. It shows different RLDUs connection with exchanges and to the operation and maintenance department of Hyderabad and Karachi.

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1 RLDU

7 RLDU

9 RLDU

HYBD

HCEN3

MPK

OFS

OFS

OFS

KHI OMC

OFS

HYDOMC

net manager

Router

Switch

Figure 3: RLDUs links with OMC

3.7 OMC connection with exchanges and Transmission dpt.

EWSD (Elektronisches Wählsystem Digital) in German or Electronic Digital Switching System:It is one of the most widely installed exchange systems in the world. EWSD can work as a local or tandem switch or combined local/tandem, and for landline or mobile phones. e over 160 million subscriber lines in more than 100 countries.

The software of EWSD is called APS (Automatic Program System). The APS is on a hard drive and includes the operating system, developed by Siemens in cooperation with Bosch. It is predominantly written in the CHILL language. Application software is switch specific and serves among other things traffic management, path search, and call charging. Support software serves translating programs, binding modules as well as administration of libraries for generating data. Operating and data communication software serve for co-operation of maintenance centers and switching centers.

ZTE (Zhongxing Telecommunication Equipment Corporation)it is a Chinese multinational telecommunications equipment and systems company headquartered in Shenzhen, China. It is the world's fifth-largest telecoms equipment maker measured by 2011 revenues (after Ericsson, Huawei, Alcatel-Lucent and Nokia Siemens Networks) and the world's fourth-largest mobile phone manufacturer measured by 2011 unit sales.

ZTE's core products are wireless, exchange, access, optical transmission and data telecommunications gear; mobile phones;[4] and telecommunications software.] It also offers products that provide value-added services, such as video on demand and streaming media. ZTE primarily sells products under its own name but it is also an OEM, manufacturing some products which retail under other brand names.

Alcatel-Lucent:

It is a global telecommunications equipment corporation, headquartered in the 7th arrondissement of Paris, France. It provides telecommunications solutions to service providers, enterprises, and governments around the world, enabling these customers to deliver voice, data, and video services. The company focuses on fixed, mobile, an converged networking hardware, IP technologies, software, and services. It holds Bell Labs, one of the largest innovation and R&D houses in the communications industry Bell Labs was awarded 7 Nobel Prizes and holds over 29,000 patents. Alcatel-Lucent has

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operations in more than 130 countries. In 2011 it was added to the Dow Jones Sustainability Index. On May 22, 2012, Alcatel-Lucent announced the development of its "7950 XRS," which is an Internet router capable of speeds up to five times faster than speeds offered by the nearest competitor.

All these exchanges are part of PTCL communication system and most of the subscriber’s are indirectly connected through these exchanges.

In the Central Exchange PTCL they are HCEN3 Siemens, Central ZTE and Transit AlcaTel.

Following figure shows their functionality with the OMC Operation and maintenance center and Transmission Department.

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Figure 4: Interconnection of exchanges with OMC and Transmission Department

4. Optical Fiber Access Network (OFAN):

4.1 Optical Fiber Communication:

Optical fiber can be used as a medium for telecommunication and computer networking because it is flexible and can be bundled as cables. It is especially advantageous for long-distance communications Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The Information or the packets of information travels at the speed of light which makes it more reliable and furious.

4.2 Optical line termination (OLT)

An optical line termination (OLT), also called an optical line terminal, is a device which serves as the service provider endpoint of a passive optical network. It provides two main functions:

1, To perform conversion between the electrical signals used by the service provider's equipment and the fiber optic signals used by the passive optical network. to coordinate the multiplexing between the conversion devices on the other end of that network (called either optical network terminals or optical network units).

2, A downstream frame processing means for receiving and churning an asynchronous transfer mode cell to generate a downstream frame, and converting a parallel data of the downstream frame into a serial data.

A wavelength division multiplexing means for performing an electro/optical conversion of the serial data of the downstream frame and performing a wavelength division multiplexing.

A upstream frame processing means for extracting data from the wavelength division multiplexing means, searching an overhead field, delineating a slot boundary, and processing a physical layer operations administration and maintenance (PLOAM) cell and a divided slot separately.

A control signal generation means for performing a media access control (MAC) protocol and generating variables and timing signals used for the downstream frame processing means and the upstream frame processing means.

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A control means for controlling the downstream frame processing means and the upstream frame processing means by using the variables and the timing signals from the control signal generation means.

An OLT, in a nutshell, is where the PON cards reside. The OLT also contain the CPU and the GWR and VGW uplink cards. Each OLT can have a few or many dozens of PON cards.

PON = Passive Optical Network

GWR = Gateway Router

4.3 Optical Network Unit:

Optical network unit (ONU) is the user side equipment in the GEPON (Gigabit Ethernet Passive Optical Network) systems. Optical network unit is used with OLT and provides the users with many kinds of broadband services such as VoIP, HDTV, and videoconferences. Optical network unit is economic and high efficient equipment and play an important role in the FTTx fiber optic network.

GEPON system is a telecom grade FTTx broadband access equipment mainly for telecom operator and large corporate users with the characteristic of high integration, flexible application, high stableness, easy management, flexible extend and buildup of the network, as well as providing QoS function. Optical network unit converts the fiber optic signal into the electric signal at the user side and enables reliable fiber optic Ethernet services to business and residential users through fiber-based network infrastructure.

An ONU closure is a mechanical compartment that houses the ONU equipment. The outer closure faces the outside environment and provides physical, mechanical, and environmental protection for cable (fiber and copper) components or equipment housed within it.

An ONU system consists of a closure that is a metallic or non-metallic enclosure that provides physical and environmental protection for the active electronic, optoelectronics, and passive optical components it houses. It terminates optical fibers from the ODN and processes the signals to and from the Customer Premises Equipment (CPE). It is the NE that provides the tariffed telecommunications as well as video service interfaces for multiple residential and small business customers.

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Services on the customer side of the ONU are communicated over metallic twisted pairs and coaxial cable drops (in the future, possibly fiber cable or wireless) to a Network Interface (NI) where they are handed off to the customer’s network (usually, inside wiring). Depending on the deployment strategy, the ONU closure may provide one or more of the following additional features:

Primary power for ONUs is derived from either an external DC or an external AC power source. Back-up power for ONUs can either be derived from an external power source or be internal to the ONU closure and be provided by the FITL system supplier. Primary power and external back-up power can be delivered to ONUs over either copper twisted pairs or coaxial cable facilities. These cable facilities are commonly referred to as the TSC.

Deployment of an ONU system requires access to the fiber distribution cable, TSC, and metallic customer drop wires. When access to these cables is provided internal to the ONU closure (i.e., by looping each cable through the closure), it is necessary that the ONU closure also provide splicing and storage facilities for each of these cables GR-950, Generic Requirements for Optical Network Unit (ONU) Closures and ONU Systems, contains complete proposed specifications for the ONU closures and systems. The following figure shows the connectivity Of ONUs with the operation and maintenance center.

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Figure 5: OMC’s Connections ONUs of Sindh

4.4 Optical Fiber Access network:

In OFAN, the Network management server NMS is linked to an optical line terminal (OLT) which connected to the Optical Network Units ONUs placed nearer to the exchange of Siemens named as EWSD which then goes to the individual exchange (local or remote) through a splitter. And all the Information is displayed on the NMS which helps in recognition of different faults in the route of Subscriber’s call.

The following figure illustrates its application in PTCL. PTCL management has progressively deployed Optical Access Network for the delivery of narrowband and broadband telecommunication services to its customers, initially in major cities.

The Optical Fiber Access Network provides fast internet access and other new and rapidly growing interactive data communication services.

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OLT

EXG

NMS

OLT

EXG

ONUs

OLT

EXG

ONUs

ONUs

Figure 6: NMS’ connection with ONUs and OLTs

5. Signaling System No. 7 (SS7):

Signaling System No. 7 (SS7) is a set of telephony signaling protocols which are used to set up most of the world's public switched telephone network telephone calls. The main purpose is to set up and tear down telephone calls. Other uses include number translation, local number portability, prepaid billing mechanisms, short message service (SMS), and a variety of other mass market services.

It is usually referenced as Signaling System No. 7 or Signaling System #7, or simply abbreviated to SS7. In North America it is often referred to as CCSS7, an abbreviation for Common Channel Signaling System 7. In some European countries, specifically the United Kingdom, it is sometimes called C7 (CCITT number 7) and is also known as number 7 and CCIS7 (Common Channel Interoffice Signaling 7). In Germany it is often called as N7 (Signalisierungssystem Signaling protocol was defined by the ITU-T as Signaling System No. 6 (SS6) in 1977. Signaling System No. 7 was defined as an international standard by ITU-T in its 1980 (Yellow Book) Q.7XX-series recommendations. SS7 was designed to replace SS6, which had a restricted 28-bit signal unit that was both limited in function and not amenable to digital systems. SS7 has substantially replaced SS6, Signaling System No. 5 (SS5), R1 and R2, with the exception that R1 and R2 variants are still used in numerous nations. Number 7).

There is only one international SS7 protocol defined by ITU-T in its Q.700-series recommendations. There are however, many national variants of the SS7 protocols. Most national variants are based on two widely deployed national variants as standardized by ANSI and ETSI, which are in turn based on the international protocol defined by ITU-T. Each national variant has its own unique characteristics. Some national variants with rather striking characteristics are the China (PRC) and Japan (TTC) national variants.

The Internet Engineering Task Force (IETF) has also defined level 2, 3, and 4 protocols that are compatible with SS7:

Message Transfer Part (MTP) level 2 (M2UA and M2PA)

Message Transfer Part (MTP) level 3 (M3UA)

Signaling Connection Control Part (SCCP) (SUA)

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but use a Stream Control Transmission Protocol (SCTP) transport mechanism. This suite of protocols is called SIGTRAN.

5.1 Common Channel Signaling:

Common Channel Signaling protocols have been developed by major telephone companies and the ITU-T since 1975; the first international Common Channel Signaling protocol was defined by the ITU-T as Signaling System No. 6 (SS6) in 1977. Signaling System No. 7 was defined as an international standard by ITU-T in its 1980 (Yellow Book) Q.7XX-series recommendations. SS7 was designed to replace SS6, which had a restricted 28-bit signal unit that was both limited in function and not amenable to digital systems. SS7 has substantially replaced SS6, Signaling System No. 5 (SS5), R1 and R2, with the exception that R1 and R2 variants are still used in numerous nationsSS5 and earlier systems used in-band signaling, in which the call-setup information was sent by playing special multi-frequency tones into the telephone lines, known as bearer channels in the parlance of the telecom industry. This led to security problems with blue boxes. SS6 and SS7 implement out-of-band signaling protocols, carried in a separate signaling channel, explicitly keep the end-user's audio path—the so-called speech path—separate from the signaling phase to eliminate the possibility that end users may introduce tones that would be mistaken for those used for signaling.

The common channel signaling paradigm was translated to IP via the SIGTRAN protocols as defined by the IETF. While running on a transport based upon IP, the SIGTRAN protocols are not an SS7 variant, but simply transport existing national and international variants of SS7

5.2 Channel associated signaling (CAS)

This is the case for earlier analogue trunks, MF and R2 digital trunks, and DSS1/DASS PBX trunks.

In contrast, SS7 signaling is termed Common Channel Signaling (CCS) in that the path and facility used by the signaling is separate and distinct from the telecommunications channels that will ultimately carry the telephone conversation. With CCS, it becomes possible to exchange signaling without first seizing a facility, leading to significant savings and performance increases in both signaling and facility usage.

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Because of the mechanisms used by signaling methods prior to SS7 (battery reversal, multi-frequency digit out pulsing, A- and B-bit signaling), these older methods could not communicate much signaling information. Usually only the dialed digits were signaled, and only during call setup. For charged calls, dialed digits and charge number digits were outpulsed. SS7, being a high-speed and high-performance packet-based communications protocol, can communicate significant amounts of information when setting up a call, during the call, and at the end of the call. This permits rich call-related services to be developed. Some of the first such services were call management related, call forwarding (busy and no answer), voice mail, call waiting, conference calling, calling name and number display, call screening, malicious caller identification, busy callback.

The earliest deployed upper layer protocols in the SS7 signaling suite were dedicated to the setup, maintenance, and release of telephone calls. The Telephone User Part (TUP) was adopted in Europe and the Integrated Services Digital Network (ISDN) User Part (ISUP) adapted for public switched telephone network (PSTN) calls was adopted in North America. ISUP was later used in Europe when the European networks upgraded to the ISDN. North America never accomplished full upgrade to the ISDN and the predominant telephone service is still the older POTS). Due to its richness and the need for an out-of-band channel for its operation, SS7 signaling is oftenly used for signaling between telephone switches and not for signaling between local exchanges and customer-premises equipment (CPE).

Because SS7 signaling does not require seizure of a channel for a conversation prior to the exchange of control information, non-facility associated signaling (NFAS) became possible. NFAS is signaling that is not directly associated with the path that a conversation will traverse and may concern other information located at a centralized database such as service subscription, feature activation, and service logic. This makes possible a set of network-based services that do not rely upon the call being routed to a particular subscription switch at which service logic would be executed, but permits service logic to be distributed throughout the telephone network and executed more expediently at originating switches far in advance of call routing. It also permits the subscriber increased mobility due to the decoupling of service logic from the subscription switch. Another characteristic of ISUP made possible by SS7 with NFAS is the exchange of signaling information during the middle of a call.

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5.3 Signaling modes:

As well as providing for signaling with these various degrees of association with call set up and the facilities used to carry calls, SS7 is designed to operate in two modes: associated mode and quasi-associated mode.

When operating in the associated mode, SS7 signaling progresses from switch to switch through the PSTN following the same path as the associated facilities that carry the telephone call. This mode is more economical for small networks. The associated mode of signaling is not the predominant choice of modes in North America. When operating in the quasi-associated mode, SS7 signaling progresses from the originating switch to the terminating switch, following a path through a separate SS7 signaling network composed of signal transfer points. This mode is more economical for large networks with lightly loaded signaling links. The quasi-associated mode of signaling is the predominant choice of modes in North America.

The Message Transfer Part (MTP) covers a portion of the functions of the OSI network layer including network interface, information transfer, message handling and routing to the higher levels. Signaling Connection Control Part (SCCP) is at functional Level 4. Together with MTP Level 3 it is called the

Network Service Part (NSP). SCCP completes the functions of the OSI network layer: end-to-end addressing and routing, connectionless messages (UDTs), and management services for users of the Network Service Part (NSP). Telephone User Part (TUP) is a link-by-link signaling system used to connect calls. ISDN User Part (ISUP) is the key user part, providing a circuit-based protocol to establish, maintain, and end the connections for calls. Transaction Capabilities Application Part (TCAP) is used to create database queries and invoke advanced network functionality, or links to Intelligent Network Application Part (INAP) for intelligent networks, or Mobile Application Part (MAP) for mobile services.

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Conclusion:

In this center we became familiar with operations being carried out in the operation and maintenance center and the programs being run on the NMS network and management system. Moreover, the interconnectivity of exchanges with each other helped in understanding the communication system throughout the province.

This part of PTCL has introduced us to the main topics of SS7 and OFAN, which are the advanced ways of communication in this era. Besides, all this we all saw the EWSD, an exchange of Siemens and the Optical network unit (ONU), which was an amplification to our knowledge.

We learned how to recognize faults and their clearance on NMS network management server.

In short, this week of internship was very much fruitful as it enhanced our knowledge related to telecommunication.

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