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Service Creation Using SIP
Broadband 1 MC Hsieh, J.Okuthe, A. Terzoli
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Table of Contents Investigating SIP Services
How to implement the voic service using SIP How to implement the alarm service using SIP Issues in Service Creation SIP stands for Session Initiation Protocol. It is a signaling protocol developed by the IETF. It is used to establish, modify and terminate sessions. Sessions can be multimedia conferences, telephone calls or multimedia distributions. I’ll be talking about the Various kinds of services that I investigated and implemented using SIP. I’ll be looking in detail specifically the voic service and how it is implemented in different architectures Then I’ll talk about the service that I created the alarm service, to demonstrate how new services can be created. Lastly touching on issues in service creation.
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Presentation requirements
What you need in order to understand my presentation? Some understanding of how SIP works Used a voic service before Used an alarm service before I’ll not explain how SIP works in this presentation. You can find more information in my presentation last year. You’ll also need to have used a voic service before or an alarm clock.
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List of services Non-interactive (signaling) services Call blocking
Call forwarding Interactive services Voic Wake me up Internetwork services SIP – SIPH323 – OPENISDN – ISDN -PSTN Various other service at: Internetwork services is when you want to use a service on a different network. So if you’re on a SIP network and you want to use a service on a H323 network you can use the SIPH323csgw to forward your calls to the h323 network. For example at Rhodes University, My college Jason Penton has setup an OPENISDNgw and I used an SIPH323csgw to communicate with it to make calls to the PSTN.
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Software Used Software used to investigate services
Commercial product: SIPCOMM Open source product: VOCAL (Vovida Open Communication Application Library) Deploying the products Studying the various services in both environment I began deploying the products which involved finding the right hardware and doing the correct installations.
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Sipcomm Voicemail Architecture
6 Alice 1 P 4 5 V R Here are the various components in the SIPCOMM architecture. P is the SIP Proxy/Redirect Server it functions are to proxy the calls to other proxies or redirect the calls to other users. V is the voic server it functions to accept calls and to establish connection between a user and a R Server. R is the RTSP (Real Time Streaming Protocol) Server it receives RTP Streams from any user agent and records them into a file. I’ve setup the P, V and R server on a single P2-mmx 450Mhz computer running all these services. They can however be distributed among many computers. P = Proxy Server V = Voic Server R = RTSP Server 2 Bob 3
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Vocal Voicemail Architecture
1 Alice MS RS VMFS 2 3 Bob MS 4 Vmclient The vocal architecture is slightly different from the SIPCOMM one. Vocal has separated the functionalities of the proxying into the MS (Marshal server) and the redirect feature into the RS (Redirect server). Vocal also contains FS (Feature servers) where features of the system is stored. The logic of the voic service is stored on the vmserver and the SIP/Signaling functionalities is in the vmclient. I’ve installed the MS, RS, VMFS, Vmclient and Vmserver on a P2 333Mhz machine but like SIPCOMM these services can be distributed. Because the vmclient here is able to handle only one simultaneous call at one time the VMFS is being used to redirect the call to the many instants of vmclient that you can create. MS = Marshal Server RS = Redirect Server VMFS = Voic Feature Server 6 5 Vmserver
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Sipcomm Alarm Architecture
5 1 Alice P 2 AlarmServer 4 In the SIPCOMM architecture I started by modifying the voic server to change it into an alarmserver. The AlarmServer would accept calls from users and establish a session with them. The sessions would be text based I.e. Just text input would be accepted using UDP sockets. The user would invite the alarmserver to a session, a session would be established. The user inputs the time when he wants to be notified of an event and then terminates the session. The alarmserver would wait for the timed event to take place and then calls back the user when he can located. This can be at any number of locations. The location information is stored on the proxy server. 3 P = Proxy Server
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Vocal Alarm Architecture
1 Alice MS 2 RS AMFS 5 3 Amclient The alarm service is more difficult to implement in the vocal environment because I had to make modifications to three things. I had to modify the vmclient into an amclient, the vmserver into an amserver and also the VMFS into an AMFS. The vmclient had to modified to understand how to record digits and the vmserver had to be modified to tell the amclient to record digits. The operation of the alarm service here is different because once you recorded the time of the event you can also record the voice message that you want to be played back to you. MS = Marshal Server RS = Redirect Server AMFS = Alarm Feature Server 4 Amserver
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Service Creation Issues
Interoperability issues Make sure your service is compatible with any SIP client E.g. The client from sipcomm does not work with the Voic service from Vocal Device issue When you are creating a service you have to aware of the kind of device it is going to be run on Here are some of the things to watch out for when developing services. Make sure your service is compatible with any user agent. I found out that the client from sipcomm is not compatible with the voic service from vocal, this was due to some fields that were missing in the SIP messages from the sipcomm client. Device issues are also important. For example in the alarm service I had to determine whether my clients were using normal telephones or just ordinary keyboards.
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Conclusion Easy service creation in SIPCOMM
Reliable services using VOCAL
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SIP and the future Microsoft is planning to release RTC (Real Time Communications) server with Windows .Net Server This will ensure that the SIP services that you write with the .Net framework will work on any device Its all about services and apps Now I am going to tell you how services are going to be created in the future. RTC Server is the equivalent of the RTC Client that comes with Windows XP. RTC Client provides services such as instant messaging, voice over ip and application sharing. RTC Client uses SIP to setup communications. The future will be all about services and how accessible your service is.
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This work was undertaken in the
Distributed Multimedia Centre of Excellence at Rhodes University with financial support from Telkom, Comparex Africa, Letlapa Mobile Solutions and THRIP. We also acknowledge the bursary support of the National Research Foundation.
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