SNI

SNI is only supported in TLS 1.x, not SSL 3.0. Additionally, older clients (MSIE on XP, Java 6, Android versions, and some programming languages) lack SNI support, causing certificate errors when multiple certificates are hosted on the same IP address.

Python 3 may send a zero-length server name extension (SNI), causing tlsv1 alert decode errors that break TLS connections.