Experiencing slowness for using HTTP1 Cronet vs Android http client

[Cheng Han]

Hi Cronet experts,

We've run some experiments on Android using Cronet library for download and upload. 

Overall the results for latency improvements are huge when using QUIC!

However, I am seeing noticeable slowness when comparing Cronet HTTP1 vs our android http client(just HTTPUrlConnection etc) for download metrics.

The way we setup the CronetEngine is to use QUIC as much as possible, and if QUIC is unknown for the first request, use Http1(since our current network stack is using Http1, this is easier for us to compare the metrics).

Some of the latency metrics for >= P75 even slower for 100%. I am trying to understand why. 

There are couple of reasons I can think of:

1. We send IP directly for current network stack while Cronet has to use hostname as there is an issue for certs, and this adds extra DNS lookup, not sure how much time added though - But Cronet HTTP1 upload also use DNS lookup which is still slightly faster than current network stack.

2. Small volume might cause biased results (takes up 7% of traffic for HTTP1)

Question:

Would it be any other possible reasons that I can look into? Could you please comment on the 2 points mentioned above if they make sense or not?

Thanks in advance!

Cheng