voip voice over ip594

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VOIP

(Voice Over IP)

Yonca Cumurcu

Koray Kurt



Today, we will deal with;

What is VoIP?

Ways of using VoIP?

What is PSTN?

Which protocols are used?

What are the Challanges?

Advantages of the VoIP usage?

Which companies produce VoIP software?

VoIP prices?

VoIP in Turkey and legal issues?



What is VoIP?

VoIP allows you to make telephone calls

using a computer network, over a data network

like the Internet VoIP uses the internet as its medium to send

voice.

For our purposes we will restrict it to meanvoice communications among 2 or more

computers.



What is VoIP?

Voice Calls are

transmittedover Packet Switched

Network instead of Public

Switched Telephone

Networks (PSTN)



What is PSTN?

PSTN is abbreveation of Public Switched

Telephone Network.

A network of fixed-line analog telephonesystem

Is now entirely digital

Includes not only fixed telephones but alsomobile phones.



What is PSTN?

Two types of PSTN:

POTS(Plain Old Telephone Service):analog

acoustic signal transformed to (similar) analogelectrical signal. (ANALOG Telephony)

ISDN(Integrated Services Digital Network):

transforming analog acoustic or electric signal

to digital values.(DIGITAL Telephony)



Ways Of Using VoIP

PC to PC

PC to Phone

Phone to PC Phone to Phone



Scenario 1: PC to PC

Need a PC with sound cardIP Telephony software(softphone): Skype, Gtalk,

VoIP Stunt, ...

Video optional



Scenario 2: PC to Phone

Need a gateway that connects IP network to

phone network



Scenario 3: Phone to Phone

Need more gateways that connect IP network to phone

networks

The IP network could be dedicated intra-net or theInternet.

The phone networks could be intra-company PBXs or

the carrier switches



Illustration of Gateway

AT-RG613TX

Gateway, 3 x 10/100TX LAN, 2 x FXS, 1 x 100TX WAN port



Which Protocols are Required for

VoIP? UDP (User Datagram Protocol)

RTP (Real-Time Transport Protocol)

SIP( Session Initiation Protocol) H323



UDP Protocol

Available in transport layer

Enable the transmission of information

between the correct processes (orapplications) on host computers.

UDP protocol is commonly used in transport

layer as an alternative to TCP protocol.



UDP Protocol

UDP Connectionless protocol

Unreliable

No sequence numbers



UDP Protocol

Source port:

Identifies the higher layer process which originated the data.

Destination port :

Identifies with higher layer process to which data is beingtransmitted.

Length :

The length in octets of the UDP data and payload (minimum 8).

Checksum :

Optional field supporting error detection.



RTP Protocol

provides end-to-end delivery services for data

with real-time characteristics (audio and

video)

includes payload type identification, sequence

numbering, and timestamping

supports mixers and translators



RTP Protocol

mixer: mixing several audio streams into a single audio stream

translator: coding transformation



SIP Protocol

SIP is a application layer control simple

signalling protocol for VoIP implementations

SIP:

not only for VoIP, but in general formultimedia communication

eg: audio / video conferencing, server-based or

p2p

provides the market with fast operation,

flexibility, scalability and multiservice support.



SIP Protocol

provides its own reliability mechanism

creates, modifies and terminates sessions

which are internet multimedia conferences,Internet telephone calls and multimedia

distribution with one or more participants.

well-known port number: 5060

support for instant messaging

format similar to HTTP



SIP Protocol

SIP works as follows; Callers and callees are identified by SIP addresses

a caller first locates the appropriate server and then

sends a SIP request

a SIP request may be redirected or may trigger a chain

of new SIP requests by proxies

Users can register their location(s) with SIP servers

SIP messages can be transmitted either over TCP orUDP



SIP Protocol

Request Messages:

The format of the Request packet



SIP Protocol

Methods Command:

- Invite: Initiate Call

- Ack: Confirm Final Response-Bye: Terminate and Transfer Call

- Cancel: Cancel Searches and Ringing

-Options: Features Support by Other Side- Register:Register with Location Service



SIP Protocol

Response Message:

The format of the Response message



SIP Protocol



H323 Protocol

H323 Prtocol is a ITU-T standard (International

Telecommunications Union)

framework for multimedia communication allow multimedia transmission through an

unreliable packet-based network



H323 Protocol

H323 includes

Call signaling H.225

Media control H.245 Audio coding G.711, G.722, G.723, G.728,

G.729 (G.711 is most used, G.729 is most

quality enhanced) Video coding H.261, H263

Data sharing T.120

Media transport RTP, RTCP



H323 Architecture

- H323 Terminal

-Gateway

-Gatekeeper

- Multipoint Control Units (MCU)



VoIP Challenges

Packet loss

Latency

Jitter Echo

Reliability

Firewalls



VoIP Challenges

VoIP implementations face problems dealing

with latency , echo and jitter

Echo:

waving of voice Latency: Changing in delivery time between

voice packets

Jitter:

Changing in delivery order of voicepackets



VoIP Challenges

Connection Problems:

problems behind NAT between peers.

Echo and jitter occurs because of packet loss. Internet stability problems can cause

reliability problems and this discourages voip

usage.

routing VoIP traffic through firewalls blocks

voice packets transmission.



Advantages of VoIP

What are the esssential factors that

encourages people to use VoIP?



Advantages of VoIP

Cost of equipment and deployement

Low price in leased-line(home phone)

Portability Flexibility

Versatility

Interconnectivity Time to market



VoIP Producers

ITSP: Internet Telecommunication Service

Provider which provides VoIP softwares

Most popular VoIP software and also theproducers are MSN, SKYPE



VoIP in TURKEY

Most popular producers in Turkey are Superonline

Borusan Telekom

Koçnet

Sabanc Telekom

Turk Telekom



Sample Estimated Price



VoIP Prices

Generally,

Producers get approximately $ 2-3

membership fee monthly . From Soft to Soft is free

From Soft to PSDN is cheaper than 80%

eg: Calling to USA with Turk Telekom is 0.12YTL, however; Calling with VoIP Stunt is 0.3

YTL



VoIP usage area in Turkey and Legal Issues

Cellphone usage cost in Turkey is very high

Until the half of the last year it was a confused

concept and alsoTü

rkT

elekom did not reachthe necessary judgement.

Today, it is legalized to some degree.

However, Türk Telekom brought these

producers to justice by esteeming this service

as illegal.



VoIP usage area in Turkey and Legal

Issues

Judgement come out in favour of the

producers.

However,Tü

rkT

elekom can cut the ISS linesand stop the activities of any voip firms

without the judgement decision.

Since, the Türk Telekom has voice monopoly,

domination on VoIP firms are increased legally

or illegaly.



In Conlusion,

We can criticise Türk Telekom because of these

immoral attitudes.

We can criticise the government because of

the latency of these legal arrangements.

We can criticise VoIP firms because of the

nonconstructed infrastructure

However, it is the unchangable fact that VoIPrevolution will dominate the all

telecommunication world several ten years

more



References;

1) http://en.wikipedia.org/wiki/Voip

2) http://www.erlang.com/protocols.html

3) http://www.pusulanet.com.tr/voipurun.htm 4) http://www.voip.gen.tr/

5) http://siptutorial.blogspot.com/

6) http://www.linecube.com/rates/compare/



Q UESTIONS?



Q 1) Is it possible to use voip solutions in wifi

enabled cellphones?

A1) Yes , it is possible. In many cellphone

operating systems there are many softphone

applications which enables voip usage. For

example, SJPhone is an application deployed

for Windows mobile 2005 OS



Q 2) Is it possible to call the PC from the phone

is used in daily life?

A2) YES. It is possible by using DID. By the help

of the special numbers which are assigned by

the daily phone network to voip network, it is

possible to provide the transition. However it

can not be used in Turkey because it is illegal.This transmission is also called number of

portability. (DID Number)



Q 3: What do you think about the differencesin price between PSDN and VoIP?

A3: Voip networks uses IP networks and over

these networks voice packages aretransferred. Internet can be used in terms of

IP network. So, there is no need to additional

investment. However, PSTNs performs

communication over the TDM and ATM

networks which have high cost. So, cost

advantage between them is very high and it

explains the difference in cost

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