Comparison of HTTP over TCP and SCTP

in High Delay Networks

Below is a list of links to quicktime movies (.mov) that compare a webpage loading operation for HTTP over TCP (left side) and HTTP over SCTP (right side). The web client and server are Firefox and Apache, respectively. Firefox and Apache were modified by the PEL research group for HTTP to run over SCTP.

The loss values refer to the percent of TCP (or SCTP) packets that were lost by our network connection, using DummyNet to control the loss rate, delay and bandwidth. When two loss values are listed, the first value corresponds to lost TCP packets; the second value to lost SCTP packets.

The emulated path had a 56Kbps bandwidth and a 1080ms RTT, intended to represent a typical communication using satelites from a developing nation.

HTTP over TCP uses a single persistent pipelined TCP connection. HTTP over SCTP uses a single persistent multistreamed SCTP association. When there is loss, the user experience greatly benefits from the combination of HTTP over SCTP and progressive jpeg images. Note that, although the page loading time using a combination of SCTP streams and progressive images appears to be much shorter than the corresponding TCP page loading operation, the page loading times are, in fact, very similar. (See progress bar in lower right corner of each page.)

Firefox 3.0.11 with SCTP support
NSPR 4.7.6 and 4.8.1 with SCTP support
Apache httpd-2.0.55 with SCTP support