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 Continue Reading
John
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 Continue Reading
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.
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 Continue Reading
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.
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. Continue Reading
SIP Messages
SIP protocol defines several messages: INVITE: inviting user to call BYE: terminating connection between two end points ACK: reliable exchange of invitation messages OPTIONS: get information about capabilities of call REGISTER: passes user location information to SIP registration server CANCEL: terminates search for user
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 Continue Reading
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 Continue Reading
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 Continue Reading