For your enterprise clients, you need perfect support for both T38 and G721 Fax
You need to be capable of handling routing for millions of DIDs
You need to be able to calculate cost for Toll Free calling based on ANI and jurisdiction
For your clients, you need to provide a fully featured self-service portal for your clients to select and buy DIDs, check DDR, and reports
You need to be able to rate and route calls based on US jurisdiction.