Impact of sack delay and link delay on failover performance in SCTP

The Stream Control Transmission Protocol (SCTP) was developed to support the transfer of telephony signaling over IP networks. One of the ambitions when designing SCTP was to offer a robust transfer of traffic between hosts. For this reason SCTP was designed to support multihoming, which gives the possibility to set up several paths between the same hosts in the same session. If the primary path between a source machine and a destination machine breaks down, the traffic may still be sent to the destination by utilizing one of the alternate paths. The failover that occurs when changing path is to be transparent to the application. Consequently, the time between occurrence of a break on the primary path until the traffic is run smoothly on one of the alternate paths is important. This paper presents experimental results concerning SCTP failover performance. The focus in this paper is to evaluate the impact of the SACK delay and link delay on the failover time as well as on the maximum transfer time for a single message, which complements earlier studies in this area. The results show a significant performance impact of the SACK delay as well as of the link delay. This suggests that the SACK delay is an important parameter to tune to enhance application transparency in failure situations.