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[英文]PBX in the Cloud or in the Closet?

2011-01-31 00:00:00   作者:   来源:   评论:0  点击:



First I want to say that over the course of my career I have designed, implemented and supported VoIP network solutions in both hosted and premises architectures. I hold no specific bias one way or the other but I believe that one strategy has advantage over the other based upon attributes of the company proposing to utilize the solution and their specific needs. In my experience, the following factors weigh most heavily in determining whether a company should consider a hosted or a premises solution:
Company size (count of end users to be supported)
Very small companies (fewer than 20 users) almost invariably find a better value in a hosted architecture than a premises deployment. This due to the fact that the recurring monthly expense of a hosted solution in these quantities is typically digestible and (assuming the availability of quality bandwidth) they can typically be purchased without an extended contract term which leaves the door open to change providers if needed. In a range from 20 to 50 users, the economies of a hosted solution are dictated by a combination of bandwidth cost / availability and anticipated monthly maintenance expense for telephony platform. Above 50 users, the economies of hosted solution typically collapse and higher recurring monthly expense overshoots the potential savings in operation, maintenance and upgrades.
Number of physical facilities (count of company locations to be supported)
The count of branch facilities to be supported also plays heavily in determining the value of hosted solutions versus premises solutions. For companies with a single facility that has 50 to 100+ users, a premises deployment will be both architecturally and financially more attractive. For companies with up to 3 branch facilities, a premises installation in each facility linked together via SIP or IAX2 trunks provides both financial efficiency and site isolation from bandwidth or machine failures. Above 3 branch facilities, the potential redundant expenses in each location begin to make the argument for a centralized, hosted design for purposes of ease of management / maintenance, price efficiency and disaster recovery.
Amount of daily or monthly PBX maintenance anticipated
Many companies shopping VoIP infrastructure are anticipating some ability to handle daily maintenance activities inside of their own doors. The “point and click” simplicity of solutions such as Digium’s SwitchVox appliance puts much of the day-to-day configuration and management within the technical capabilities of the average IT guy and reduces the necessity of outside maintenance assistance. Still, those companies that anticipate a high amount of monthly management requirements can benefit from the inclusive support provided by many hosted operations. Essentially, where a customer can receive significant value from inclusive support in a hosted configuration, this deployment design has distinct advantages.
Condition of WAN and associated carrier contracts
One of the more compelling ROI opportunities available in a conversion to a VoIP infrastructure is powered by cost savings through disconnection of conventional TDM service connections and replacing them with public or private data connections. However, if a company is under contract for telecommunication services, the cost to break these contracts can have a significant impact on available monthly savings. Customers in fresh telecommunications contracts are stronger candidates for premises deployments while those who are not encumbered by contracts are typically better candidates for a potential conversion to a hosted or co-located solution where their other attributes make them a strong candidate for this design.
Up time requirements
There has been a heavy focus on business continuity and disaster recovery for all aspects of IT infrastructure in recent years. While conventional PBX solutions have not historically provided any measurable level of redundancy, the migration of these technologies into IP network environments has raised the bar for availability in business telecommunications solutions. If business continuity is a high priority, the advantage can go to a hosted design. This is not to say that a premises deployment cannot be engineered for high availability, but the costs to supply this ability can slant the value proposition toward a hosted or co-located solution design.
The third option: Hybrid or “Co-located”
There is a third, hybrid deployment design that is best described as “co-located” that supplies the efficiency and assurances of a hosted design with a financial structure more akin to a premises deployment. This structure includes customer-owned equipment running in a data center with private network connectivity to both the customer facility and VoIP carrier networks. A co-located design raises the bar for quality a