31. This means that the transport layer can keep track of the segments and retransmit those that fail. 32. The most common transport layer protocol to use multicast addressing is User Datagram Protocol ( UDP ). 33. For secure transmissions of SIP messages, the protocol may be encrypted with Transport Layer Security ( TLS ). 34. The SSL / TLS library operates above the transport layer ( uses TCP ) but below application protocols. 35. In addition, any other protocol encapsulations used during transit, such as IPsec or Transport Layer Security, are removed. 36. XNS combined the OSI's Session and Transport layers into the single Interprocess Communications layer ( layer 2 ). 37. By letting only the transport layer deal with physical network-dependent issues, global interoperability can be acquired using mediating gateways. 38. In addition to supporting other transport layers , the successor to the CCP protocol contains many functional improvements such as: 39. Examples of transport layers which are typically removed include WAN environments, Inverse Multiplexed ATM, PPP Multilink are also common. 40. There are several other APIs described in the X Transport Interface, for instance TLI ( Transport Layer Interface ).
