UDP: the most common transport for SIP. Use port 5060 (standard) or 5070 (when 5060 is blocked).
TCP: supported by most SIP clients. This is a better option when using SIP on a mobile device because it polls less frequently and thus uses less power. This is also available on port 5060 (standard) and 5070 (alternate).
TLS: supported by some SIP clients. This transport is encrypted and operates on TCP port 5061.