SPDY Proxy via SSL NPN
The added benefit of supporting HTTPS proxies is that we can use SSL’s Next Protocol Negotiation (NPN) to upgrade our connection to speak SPDY! Once the tunnel is established, the browser and the proxy can multiplex multiple SPDY streams over the same connection, allowing us to minimize latency and optimize throughput – especially useful on mobile device. In fact, this is precisely how Amazon’s Silk browser operates: single SPDY connection to an AWS proxy!
If your browser needs to fetch an HTTP resource, it uses the same SPDY connection, but in its SPDY frame it allocates a new “Stream ID”, which indicates to the proxy that this is an independent request. The proxy can then fetch the HTTP resource on your behalf and stream it back over SPDY. Best of all, this same workflow also works for HTTPS, which means that we can tunnel SSL over SSL, and hence we can tunnel SPDY over SPDY:
If we inspect chrome://net-internals#spdy,