At this juncture, all of the current VoIP applications are written for Version 4. New releases of VoIP software will eventually support IPV6 as the technology becomes fully meshed with data as a standard procedure. As the market matures, V6 will eventually replace V4 as the defacto standard. V6 has some inherent advantages and characteristics, such as additional stacks, authentication, mobile user support, and auto-configuration among others, characteristics that provide a more "natural fit" for VoIP. This is not to say, however, that VoIP is not available or stable using V4. In a more rural or suburban environment how does VoIP and/or IP Telephony address 911 or 411 considerations where sophisticated PBXs do not exist?
911 and 411 considerations typically start with Central Office (telephone company) capability for E911/411. You should differentiate first between E911 regulatory compliancy and internal corporate desire/policy. E911 from the Central Office provides you the ability to be traced to the site at least, but not the specific handset/desk in the building, unless the feature is available in your PBX system. For compliancy purposes, you may just need to get to the building. Stricter requirements, to the desk, may be required in certain geographic areas or for internal corporate requirements, and therefore you may need to look at upgrades/replacements at some of your sites where necessary. Look to local mandates first, and then proceed from there. How do you support 911 services and Caller ID on VoIP?
VoIP is an evolving technology, and thus, certain more complex features such as E911 need to be addressed for remote mobile users. For most companies, remote mobile users that need to retain their addresses has yet to mature, however, E911 and Caller ID services using the PSTN public network via POTS lines, local dial-up T-1 lines, or ISDN lines can provide for such E911 services. Should you require E911 now for specific applications, address your core local site users first and define E911 via your PBX to the PSTN network. Definitely expect to see this area addressed and evolve in future releases for VoIP. We are currently preparing to pilot a VoIP project, one vendor has a distributed (call control at the edge) vs centralized call control (server), please comment on whether there is an advantage of either one and if so, what are they?
It is less a matter of what is technically better, but more preferential in nature. From a future applications and centralized network management point-of-view, my preference would be centralized call control. The centralized approach provides for future integrated voice mail/e-mail integration via Unified Messaging, and in the studies we have performed, also provides a better Total Cost of Ownership model.