to route emergency calls over your SIP trunk to the provider, the distrib- uted model best accomplishes this. Calls from the site enter the PSTN locally, and routing to the local authorities is not a challenge. Also, in a distributed trunking model, the Border Element is collocated at the site that originated the emergency call, and location information is intrinsically correct when delivered to the provider, and in turn by the provider to the authorities. In the centralized SIP trunking model, ensuring correct location information is more chal- lenging. If an emergency call originates from a remote site in the state of Utah, but enters the PSTN through a centralized SIP trunk in New York, the SP has two challenges: The call must be routed to the correct authorities in Utah, which might be under dif- ferent regulations and jurisdictions than New York. The location information available to the SP is that of your Border Element in New York where the call was delivered to the provider's network. How can the information that this is actually a call from Utah be available to the SP? Tip Carefully consider emergency call routing and location information delivery for SIP trunks, especially in the centralized model. Discuss emergency call routing with your SP, and if the answer is unsatisfactory, keep emergency calls on TDM trunks for the time being. Dial Plan and Call Routing Considerations If you choose the distributed model, your dial plan and call routing implementation most likely needs to change much less than for centralized trunking to accommodate the migration from TDM PSTN to SIP PSTN access. Although it could change if you decide, perhaps based on cost benefits, to route only certain types of calls (for example, long distance calls or contact center calls) or calls to and from only certain sites over the SIP trunk. Different business drivers motivate SIP trunk use for different types of calls, and there isn't a single answer about which calls you should use your SIP trunk for first. The typical possibilities f