Publish Nav 2009R2 Web Service on Internet

Hello, I need to publish NAV Web Services on the Internet.

I have a 3-tier architecture
SQL Server DB, NAV 2009R2 Server, Web Services for NAV
Web Services are currently published only on the network (only on customer’s intranet) with the delegation of authentication (Kerboeros).

Now i need to install a second Web Service and publish others services it on the Internet (WAN)

What types of publishing scenarios are possible and what model of security is better to implement?

have you any example of publications ?

Thanks for your support