VOIP Voice Over IP Yonca Cumurcu Koray Kurt

VOIP (Voice Over IP) Yonca Cumurcu Koray Kurt

Today, we will deal with; • • • What is Vo. IP? Ways of using Vo. IP? What is PSTN? Which protocols are used? What are the Challanges? Advantages of the Vo. IP usage? Which companies produce Vo. IP software? Vo. IP prices? Vo. IP in Turkey and legal issues?

What is Vo. IP? • Vo. IP allows you to make telephone calls using a computer network, over a data network like the Internet • Vo. IP uses the internet as its medium to send voice. • For our purposes we will restrict it to mean voice communications among 2 or more computers.

What is Vo. IP? • Voice Calls are transmitted over 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 telephone system • Is now entirely digital • Includes not only fixed telephones but also mobile phones.

What is PSTN? • Two types of PSTN: • POTS(Plain Old Telephone Service): analog acoustic signal transformed to (similar) analog electrical signal. (ANALOG Telephony) • ISDN(Integrated Services Digital Network): transforming analog acoustic or electric signal to digital values. (DIGITAL Telephony)

Ways Of Using Vo. IP • • PC to PC PC to Phone to PC Phone to Phone

Scenario 1: PC to PC • Need a PC with sound card • IP Telephony software(softphone): Skype, Gtalk, Vo. IP 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 the Internet. • The phone networks could be intra-company PBXs or the carrier switches

Illustration of Gateway AT-RG 613 TX Gateway, 3 x 10/100 TX LAN, 2 x FXS, 1 x 100 TX WAN port

Which Protocols are Required for Vo. IP? • • UDP (User Datagram Protocol) RTP (Real-Time Transport Protocol) SIP( Session Initiation Protocol) H 323

UDP Protocol • Available in transport layer • Enable the transmission of information between the correct processes (or applications) 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 being transmitted. 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 • translator: coding transformation • mixer: mixing several audio streams into a single audio stream

SIP Protocol • SIP is a application layer control simple signalling protocol for Vo. IP implementations • SIP: not only for Vo. IP, but in general for multimedia communication eg: audio / video conferencing, server-based or p 2 p • 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 or UDP

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

H 323 Protocol • H 323 Prtocol is a ITU-T standard (International Telecommunications Union) • framework for multimedia communication • allow multimedia transmission through an unreliable packet-based network

H 323 Protocol • H 323 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, H 263 – Data sharing T. 120 – Media transport RTP, RTCP

H 323 Architecture - H 323 Terminal -Gateway -Gatekeeper - Multipoint Control Units (MCU)

Vo. IP Challenges • • • Packet loss Latency Jitter Echo Reliability Firewalls

Vo. IP Challenges • Vo. IP 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 voice packets

Vo. IP 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 Vo. IP traffic through firewalls blocks voice packets transmission.

Advantages of Vo. IP • What are the esssential factors that encourages people to use Vo. IP?

Advantages of Vo. IP • • Cost of equipment and deployement Low price in leased-line(home phone) Portability Flexibility Versatility Interconnectivity Time to market

Vo. IP Producers • ITSP: Internet Telecommunication Service Provider which provides Vo. IP softwares • Most popular Vo. IP software and also the producers are MSN, SKYPE…

Vo. IP in TURKEY Most popular producers in Turkey are • • • Superonline Borusan Telekom Koçnet Sabancı Telekom Turk Telekom

Sample Estimated Price

Vo. IP 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. 12 YTL, however; Calling with Vo. IP Stunt is 0. 3 YTL

Vo. IP 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 also. Türk Telekom did not reach the necessary judgement. • Today, it is legalized to some degree. • However, Türk Telekom brought these producers to justice by esteeming this service as illegal.

Vo. IP usage area in Turkey and Legal Issues • Judgement come out in favour of the producers. • However, Türk Telekom can cut the ISS lines and stop the activities of any voip firms without the judgement decision. • Since, the Türk Telekom has voice monopoly, domination on Vo. IP 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 Vo. IP firms because of the nonconstructed infrastructure • However, it is the unchangable fact that Vo. IP revolution 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/

QUESTIONS?

• Q 1) Is it possible to use voip solutions in wifi enabled cellphones? • A 1) 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? • A 2) 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 differences in price between PSDN and Vo. IP? • A 3: Voip networks uses IP networks and over these networks voice packages are transferred. 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.