Modeling and Performance Evaluation of SCTP as Transport Protocol for Firewall Control

Firewalls are a crucial building block for securing IP networks. The usage of out-of-band-signaling protocols (such as SIP) for VoIP and multimedia applications requires a dynamic control of these firewalls, which can be implemented using the Simple Middlebox Configuration Protocol (SIMCO). In this paper, we study the performance of SCTP and TCP as transport protocols for the transaction-based signaling protocol SIMCO, which requires small end-to-end delays. We present an analytical model in order to quantify the impact of head-of-line blocking in SCTP. Both, the model and measurements reveal that SCTP can significantly reduce the SIMCO response times by leveraging transmission over multiple parallel streams. While a few SCTP streams can almost completely avoid head-of-line blocking, our measurements show that TCP may suffer from rather large end-to-end delays.