Developing service VOIP in Viet Nam

Telecom project: Developping Service VOIP

Ha Noi open university

Center For International training Co-operation

Thesis:

Teacher : NguyÔn Th¸i Nguyªn

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Lª Träng NghÜa

NguyÔn Xu©n T

Mai Träng Dòng

Bïi Thanh Nhµn

Ng« ThÞ Nhµn

Hµ Néi ngµy 15/1/2006

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Telecom project: Developping Service VOIP

Glossary

ATM : Asynchronous Trasfer mode

ACELP : Algebraic Code Excited Linear Predictive

ARQ : Automatic Rrepeat Request

ACF : Admission Confirm

DES : Data Encryption Stadard

PSTN : Public Switched Telephone Network

PC : Personal Computer

PCM : Pulse Code Modulation

IP : Internet Protocol

ITU : International telecommunication Union

IETF : Internet Engineering Task Force

ISUP : ISDN User Part

INAP : Intelligent Network Application Part

ITSP : Internet Telephony Service Provider

MAP : Mobile Application Part

MGCP : Multimedia Gateway Control Protocol

MTP : Message Trasfer Part

MP : Multi point

MCU : Media Control Unit

OLC : Open Logical Channel

QoS : Quality of Service

RC : Report Court

RSVP : Resource Reservation Protocol

RTCM : Real Time Control Mode

RTP: Real Time Post

SIP : Session Initiation Protocol

SS7 : Signal No.7

SCCP : Signaling Connection Control Part

STP : Signaling Transfer Point

TCP : Transmission Control Protocol

TCAP: Transaction Capabilities Application Part

UDP : User Data Package

VAD : Voice Activity Detector

VoIP : Voice over Internet Protocol

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Telecom project: Developping Service VOIP

General of the thesis

VoIP -Voice over Internet protocol

VoIP ( Voice over IP- that is, vioce delivered using the Internet Protocol) is a term

used in IP telephony for a set of faccilities for managimg the delivery of voice

information using the Internet Protocol(IP). In general, this means sending voice

information in digital form in discrete packets rather than in the traditional circuit –

committed protocols of the public switched telephone network (PSTN). A major

advantage of VoIP and Internet telephony is that it avoids the tolls charged by

ordinary telephone service.

VoIP, now used somewhat generally, derives from the VoIP Forum, an effort by

major equipment providers, including Cisco, Vocltec, 3 Com, and Netspeak to

promotethe use of ITU-T H.323, the standard for sending voice (audio) and video

using IP on the public Internet and within anintranet. The Forum also promotes the

user of directory service standard so that user can locate other users and the use of

touch-tone signals for automatic call distribution and voice mail.

In addition to IP, VoIP uses the real-time protocol (RTP) to help ensure that packets

get delivered in a timely way. Using public networks,it is currently difficult to

guarantee Quality of Service (QoS). Better service is possible with private network

managed by an enterprise or by an Internet telephony service provider (ITSP).

A technique used by at least one equipment manufacturer, Netspeak, to help ensure

faster packet delivery is to Packet Internet or Inter- Network Groper (Ping) all

possible network gateway computeres that have access to the public network and

choose the fastest path before establishing a Transmission Control Protocol (TCP)

sockets connection with the other end.

Using VoIP, an enterprise positions a “VoIP device” (such as Cisco’

s AS5300

access server with the VoIP feature) at a gateway. The gateway receiver packetixed

voice tranmissions from users within the company and then routes them to othe parts

of its intranet (local area or wide area netnork) or using a T- carrier system or E￾carrier interface, sends them over the public switched telephone network (PSTN)

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Telecom project: Developping Service VOIP

Chapter1:Voice over IP (VoIP) Technology

1. Fundamental features of channel switching network and Internet:

1.1. Fundamental features of channel switching network:

The channel switching network is designed for rapid connect and eliminating

the ineffectiveness of time-consume on connecting. In the channel shifting

network, the user is provided a conductive channel to exchange information

together. When the exchange completed, the conductive channel is released. This

could lead to loss because of limits of conductive channel. The utility is low but

ensures the calling quality because a two-way 64 kbps channel is set aside for

caller and receiver. The channel shifting network is designed optimum for real

transmission time with high service quality. In the channel switching network, all

terminal equipment and switch board are inserted a fixed number so no need to

enter address for information exchanging process. The switching system in

channel switching network will base on the address of called subscriber to define

the conductive line. Because the band width is ensured not be changed during

calling, calling fee of channel switching network is based on distance and calling

time.

1.2. Fundamental features of Internet:

Internet is the package switching network suitable with applications that are

not exchanged according to the real time; Package delay doesn’t effect strongly

on service quality like email and file transmission. Package switching networks

don’t set aside a fixed line between two users, so, not ensure the service quality.

All information on the network are divided into packages, these packages contain

the destination address and its order.

Channel fixer and host on the network will send these packages to the

targeted address. On Internet, all packages are treated the same with out

distinguishing their contents. When packages to the destination address, they will

be arranged according to the initial number. By form of package information

transmission, the utility is maximum. However, real time applications will be

greatly effected on service quality. The fee is not calculated on distance or time

but on used band width. On Internet, on address of package is marked by IP

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Telecom project: Developping Service VOIP

address, the IP address will be named for the host and terminal stations. Channel

fixing will be controlled by the IP destination address. To create a

understandable, convenient address type for the IP address by name like service

of regional name or email address.

Because the limit of IP address, the users are temporarily inserted IP while

dialing. The IP address is only for one terminal equipment while connecting

Internet and deleted while not connecting. The deleted IP address will be used for

another connecting on the network.

1.3. Advantages of VOIP against PSTN:

The users will pay for used time of PSTN if more time for call establishment,

more increased fee to be paid. At one time, they can contact to one person. But with

VoIP, the time for call establishment is independent to subscriber’s fee. One

subscriber could have calls to different ones and exchange data, dialogue, pictures,

paintings and video with other subscribers.

Figure 1: The basic structure of telephone network by IP

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Telecom project: Developping Service VOIP

1.4. Outlook of VoIP technology:

+ Some technical features of IP telephone:

By analysis of fundamental features of channel switching network and

Internet, we see that it is typical to accumulate real time signal into the package

switching network and IP telephone. Firstly, we should classify IP telephones. All

IP telephones change according to 3 characters: type of terminal equipment,

position of gateway, between IP and PSTN networks and main transmission

equipment.

a. Terminal equipment and gateway: There are 03 main types of IP. They are PC

to PC, PC to Phone, Phone to Phone.

+ PC to PC is the first model of IP telephone. Users at two ends of PC to PC

should have 1 PC that is equipped audio, a software and connected to Internet.

This service no need gateway and PCTN because PCTN never switch these

calls, the main transmission tool is public Internet. Due to sound quality and

complexity of use, the PC to PC has a litter affect on traditional telephone

service.

+ PC to Phone expands the number of users but for exploiters, the call of PC to

Phone is more complex than that of PC to PC.

+ Phone to Phone is very important market including mainly commercial

services, because, people prefer to communicate by phones. However, the 3rd

model of IP requires more investment capital because it needs input gateway to

PSTN near places providing service. Services of Phone to Phone are nearly

similar to that of traditional telephones.

b. Transmission equipment: The classification between IP and VoIP telephone is

based on the nature of main transmission equipment. IP telephone is for voice

transmission, fax and services relating to package switching networks on IP.

Internet phone and VoIP are basic types of IP. Internet phone is IP in which the

main transmission network is public Internet (global super-network).

Voice over IP is IP in which the main transmission network is private-used one

basing on IP.

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Telecom project: Developping Service VOIP

Besides, being the replacing tools for distance and international phone, the IP

technology creates a plenty of other services that can transmit every service by IP.

This part only mentions the technology of VoIP and interests in the terminal

equipment that is telephone on the channel switching network (Phone to Phone).

Figure 2: IP call: Phone to Phone

+ Special features of VoIP:

a. Adjustable quality: The quality of VoIP depends on each part (coding and low

speed re-coding for each part). Internet is not specific service network, the

exchanging methods are entirely selected by terminal systems. Thus, the

terminal systems can control the compressed volume on the network bandwidth

or content for transmission.

b. Security: Using SIP to order a password and confirm messages indicating the

terminal. RIP make and the password to be the password of transmission

method. Therefore, all program is coded to secure transmission.

c. Users interface: Terminal systems of VoIP have plentiful indications and can

give out instructions and various graphic interface.

d. Connecting telephone and computer: Available to solve these complex

connections.

1.5. Conclusion:

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