When EDI is set up via a service provider, communication channels are provided by the latter. Some of these service providers are known as VANs (Value Added Network), and they perform EDI transmission within their own private network, typically through X.400 mailboxes. Another segment is known simply as EDI providers - they provide message transmission via an open network and generally also offer conversion and other services, such as invoice archiving. These service providers are closer to the outsourcing service of EDI.
Interestingly, despite offering a more limited range of services, VANs are more expensive than outsourcing providers. This has historical reasons: VANs were set up first, and outsourcing providers, established later, are competing with them by offering lower prices.