SIP (Session Initiation Protocol) is an open standard protocol which provides the connection and routing of VOIP calls.

The power of SIP is that it is driven by DNS servers - the same servers which allow you send email and browse the web using easy to remember addresses. The same applies to SIP calls.

Example: A company decides to convert to a SIP phone system, but keeps the extension numbers the same to allow for DDI numbers to match extensions.
They have a registered domain name of acompany.com With this in mind they set up a sub domain sip.acompany.com which is serviced by their SIP phone system.

Now with the minimum of effort they issue SIP phone numbers. So Joe Bloggs on extension 2000 also has an alias of Joe, which gives him a sip address of joe@sip.acompany.com. Anyone with a SIP phone, regardless of location, can effectively call Joe for free, allowing for internet connectivity costs. Of course it's just as simple to issue "sales" or "support" and direct these calls to the correct part of the organisation.

Most people will say "what's the point, I don't know anyone who has a SIP phone" A valid point, but SGJ Solutions believes that we are at this moment in time in the same position as the early adopters of the Fax machine.

You could buy one but you had no one to fax. The fax machine's early adopters were offices with multiple sites, then slowly other companies bought faxes to deal with suppliers and customers in the "I have one why don't you" scenario.

The same will apply to SIP; the initial requests will be for inter-office calls, or home workers to be brought into the organisation rather than working from stand alone lines in their houses. However by doing this they are allowing for SIP traffic from outside their organisation to also call them for free allowing of course for internet connectivity costs. This is something to bear in mind when looking to purchase a new phone system.