What is TLS?
TLS (“Transport Layer Security”) is the modern version of SSL and is used to secure TCP sockets. TLS is specified in RFC 2246 (version 1.0), RFC 4346 (version 1.1) and RFC 5246 (version 1.2). When people talk about connections “secured with SSL”, today TLS is the technology that’s really used instead of older editions of SSL.
See the Wikipedia entry for TLS if you are interested in the technical mechanics behind TLS.
BEST PRACTICE: All modern file transfer clients and file transfer servers should support TLS 1.0 today. Most clients and servers support TLS 1.1 today, but TLS 1.1 support will probably not be required unless major issues appear in TLS 1.0. Some clients and servers support TLS 1.2 today but it’s a trivial concern at this point. All file transfer software should use FIPS validated cryptography to provide TLS services across file transfer protocols such as HTTPS, FTPS, AS1, AS2, AS3 or email protocols secured with TLS.