Author: John
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Finding out something
Tends to apply to physical sciences involving experimentation and observation. e.g. observing behaviour of a bird to establish how it finds it’s way half-way around the world during migration. Use new technology such as GPS and micro-transponders to tag a bird and map their route. New knowledge as routes were not previously known before the…
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What is Research?
Answering questions. Research starts with a question. Research is: proving a theory done by experts used to establish facts about something scientific objective a lot of hard work and not fun All of above can apply and equally none! Scientific research – find out something new and something, or invent something new. Keyword is “new”.
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Benefits of VoIP
Lower operational cost – single infrastructure, free additional features (caller ID & conference call). Flexibility – more than one call over single broadband connection. Security – encrypt/authenticate IP stream. Integration – video conversation, data file exchange & audio conference.
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Corporate Users
Many large companies have extensive data communications networks internally and across sites. No need to spend extra for voice services, use existing network for VoIP services. Advantages: Migrating from copper-wire to VoIP over data network Better use of bandwidth Lower cost – no duplicating services Unified communication systems – single infrastructure to manage Dual-mode phones…
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Telecommunication Providers
“IP Backhaul” – providing links between switching stations (exchanges) and connecting between providers. Some providers rolling out VoIP in place of standard telephony service.
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Consumer Market
Available since 2004. Delivered by existing broadband connection. Behaves much like standard Public Switched Telephone Network (PSTN). Requires equipment: Dedicated VoIP phone, or Adaptor for standard analog phone, or Software and headset/web cam Benefit for home users is ability to make free phone calls, especially when making long distance calls. Most common provider is Skype.
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SIP Components
User Agents: End system acting on behalf of user e.g. client & server. Initiates SIP request & server receives requests and returns responses on behalf of user. Network Servers: Three types available: Registration server – receives client location updates. Proxy server – forwards receiving request to next-hop server. Redirect server – determines next-hop server, returns…
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SIP Functions
SIP has following functions: User Location: determination of end system to use for communications Call Setup: ringing & establishing call parameters by both called and calling parties User Availability: determination of willingness of called party to engage in communications User Capabilities: determination of media and media parameters to use Call Handling: transfer & termination of…
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Session Initiation Protocol (SIP)
Distributed architecture for creating, modifying and terminating sessions with one or more participants. Controls communications sessions. Standardised under IETF. Covers video conferencing, audio conferencing and one-to-one telephone calls. Stack independent, usually run over TCP or UDP. Uses request/response model similar to HTTP – client sends a request and gets a response from server. Requests/responses in…