voip voice over ip594
TRANSCRIPT
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VOIP
(Voice Over IP)
Yonca Cumurcu
Koray Kurt
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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?
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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.
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What is VoIP?
Voice Calls are
transmittedover Packet Switched
Network instead of Public
Switched Telephone
Networks (PSTN)
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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.
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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)
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Ways Of Using VoIP
PC to PC
PC to Phone
Phone to PC Phone to Phone
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Scenario 1: PC to PC
Need a PC with sound cardIP Telephony software(softphone): Skype, Gtalk,
VoIP Stunt, ...
Video optional
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Scenario 2: PC to Phone
Need a gateway that connects IP network to
phone network
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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
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Illustration of Gateway
AT-RG613TX
Gateway, 3 x 10/100TX LAN, 2 x FXS, 1 x 100TX WAN port
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Which Protocols are Required for
VoIP? UDP (User Datagram Protocol)
RTP (Real-Time Transport Protocol)
SIP( Session Initiation Protocol) H323
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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.
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UDP Protocol
UDP Connectionless protocol
Unreliable
No sequence numbers
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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.
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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
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RTP Protocol
mixer: mixing several audio streams into a single audio stream
translator: coding transformation
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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.
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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
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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
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SIP Protocol
Request Messages:
The format of the Request packet
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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
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SIP Protocol
Response Message:
The format of the Response message
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SIP Protocol
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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
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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
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H323 Architecture
- H323 Terminal
-Gateway
-Gatekeeper
- Multipoint Control Units (MCU)
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VoIP Challenges
Packet loss
Latency
Jitter Echo
Reliability
Firewalls
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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
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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.
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Advantages of VoIP
What are the esssential factors that
encourages people to use VoIP?
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Advantages of VoIP
Cost of equipment and deployement
Low price in leased-line(home phone)
Portability Flexibility
Versatility
Interconnectivity Time to market
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VoIP Producers
ITSP: Internet Telecommunication Service
Provider which provides VoIP softwares
Most popular VoIP software and also theproducers are MSN, SKYPE
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VoIP in TURKEY
Most popular producers in Turkey are Superonline
Borusan Telekom
Koçnet
Sabanc Telekom
Turk Telekom
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Sample Estimated Price
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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
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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.
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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.
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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
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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/
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Q UESTIONS?
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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
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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)
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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