The Stream Control Transmission Protocol (SCTP) is a newer transport protocol, having additional features to TCP. Although SCTP is an alternative transport protocol for the Session Initiation Protocol (SIP), we do not know how SCTP features influence SIP server scalability and performance. To estimate this, we measured the scalability and performance of two servers, an echo server and a simplified SIP server on Linux, comparing to TCP. Our measurements found that using SCTP does not significantly affect on data latency: approximately 0.3 ms longer for the handshake than that for TCP. However, server scalability in terms of the number of sustainable associations drops to 17-21%, or to 43% of TCP if we adjust the acceptable gap size of unordered data delivery.
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