Tranztec connects systems through three methods, and which one applies depends on what the system on the other end supports — not a preference either side gets to pick in isolation.
API integration connects directly to a system's programmatic endpoints for near-real-time data exchange. This is typically the fastest to set up when the target system has a modern, documented API.
EDI integration uses standardized transaction sets (204, 214, 210, 990, and others) to exchange documents with trading partners that require it — most large shippers, brokers, and enterprise retailers.
Portal integration covers systems that don't expose an API or support EDI at all — data is captured or delivered through a web interface instead. It's the least automated of the three, but sometimes it's the only option a given partner supports.
Most carriers and brokers end up running all three simultaneously, one per trading partner, which is exactly the fragmentation a shared connectivity layer is built to absorb.