Kari-Anne,
It's hard to make a fair determination of what the Pros and Cons will actually be for your VOIP deplyment with so little information that is available. So I will provide your general question with a general answer. Some of the conditions that I have described below may not be applicable toward your circumstance, but I thought I should mention them.
Management
Available staff - knowlegable personnel - local hiring practices - you will need to have personnel at each site that will be able to support your VOIP network and call routing to your local PSTN gatway
Time zone difference considerations - a technical issue occurs at a location that is several time zones away from the needed vendor support locations
Will there be localized vendor support for your media gateway hardware - localized vendor support can provide you with onsite personnel for the support of your IP / PSTN gateway. This will add to the benefit of a service level agreement with your gateway vendor
Communicating with technical staff in a variety of languages - the interpretation of technical documentation and support calls could become a consideration for the purchasing of the Media Gateway in different countries. This could lead to addtional personnel traning and addtional equipment costs.
Legal
Regionally supported protocls for communication with the local PSTN - this will become a matter that has to be researched on a country by country basis
Regional phone services carrier license - researching any local legislation that sutains the need for a type of license may be needed. Taxation on a per coutry basis may be a reality also.
Need for localized attorney to assist with the local adminstration of legal technicalities - to be able to reorganize - renegotiate local contracts with goverment and PSTN vendors as laws and protocols change
Hardware
Implementing gateway hardware from the same vendor - can the same equipment be used at all locations and will worldwide technical support be an issue - language barriers
Pros
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Cost
The overall cost of a worldwide telephone network for your organization
Hardware
If your deployment is going to be to several small branch offices then the cost of equipment will be relatively inexpensive. In this type of deployment purchasing equipment from local vendors that can provide a adequate service level agreement willl be appreciated.
If you need some more information then please provide me with some more details.
Thanks,
Mike Adkins OCS - beta support team