Transmission Control Protocol (TCP) (RFC793) performs an enormous service as the primary transport protocol in the means of reliable data transfer in IP networks. However, because it was defined a long time ago and was designed as a packet-oriented protocol, TCP imposes several limitations for new emerging applications. An increasing number of recent applications have found TCP too limiting. Some of the limitations include the following:

• Reliability mechanisms—TCP provides both reliable data transfer, through acknowledgments mechanism, and strict order of transmission delivery of data, through sequencing mechanism. Some applications need reliable transfer without sequence maintenance, while others would be satisfied with partial ordering of the data. In both of these cases the head-of-line blocking caused by TCP adds unnecessary delay.

• Real-time issues—The abovementioned acknowledgement mechanism (which added the unnecessary delay) makes the TCP inappropriate for real-time applications.

• TCP sockets—The limited scope of TCP sockets complicates the task of providing highly available data transfer capability using multi-homed hosts.

• Security issues—TCP is relatively vulnerable to denial-of-service attacks.

All the abovementioned limitations of TCP are relevant while trying to transport SS7 signaling over IP networks, and this is the direct motivation for the development of SCTP as a new transport protocol for SIGTRAN. SCTP has not been developed solely for SIGTRAN; thus SCTP may be a good solution for the requirements of other applications.