Identifying the protocols being used by current connections

There are four different Net-Library options are available for SQL Server.

Shared Memory
TCP/IP
Named Pipes
VIA (Virtual Interface Adaptor)

Below script provides you details about existing connections when connection was establish and which protocol used by particular connection.

SELECT session_id,connection_id, connect_time, net_transport, net_packet_size, client_net_address
FROM sys.dm_exec_connections

To learn more about protocol please click here