Lecture 7: Internet Applications #3.3: HTTP/1.1

HTTP/1.0 Performance Issues

HTTP/1.0 has been criticised for poor performance and lack of scalability. There are several aspects to this:

HTTP/1.0 opens a new TCP connection for every single transaction. For example, if a Web page contains 10 <img ...> images, HTTP/1.0 must open a total of 11 TCP connections -- one for the original page, and 10 for the images. Problems which arise from this include:
- There can be a moderately long overhead in initial connection establishment due to round-trip delays.
- TCP initiates connections using the so-called "slow start" algorithm. This is necessary for proper operation, but is very inefficient for short transfers -- TCP typically takes 10 to 20KB of transferred data to get "up to full speed". Both of these can cause HTTP/1.0 browsers to seem really slow.
TCP is required to maintain "state" information about closed connections for 240 seconds, to ensure that stray packets from old connections won't be interpreted as valid data by a later connection. When a server is handling a large number of connections, this can require huge buffer space, and is very inefficient.
HTTP/1.0 has very limited support for caching.

Because of these aspects, HTTP 1.0 is gradually being replaced by HTTP 1.1. (rfc2616).