Question

Being curious, I wonder why HTTP, by design, can only handle one pending request per socket.

I understand that this limitation is because there is no ‘Id’ to associate a request to its response, so the only way to match a response with its request is to send the response on the same socket that sent the request. There would be no way to match a response to its request if there was more than one pending request on the socket because we may not receive the responses in the same order requests were sent.

If the protocol had been designed to have a matching ‘Id’ for requests and responses, there could be multiple pending requests on only one socket. This could greatly reduce the number of socket used by internet browsers and applications using web services.

Was HTTP designed like this for simplicity even if it’s less efficient or am I missing something and this is the best approach?

Thanks.

Answer 1

It’s basically for simplicity; various proposals have been made over the years that multiplex on the same connection (e.g. SPDY) but none have taken off yet.