Apache Bench: SSL handshake failing directly related to concurrency level

Question

I ran some tests on ab and when I use a concurrency level of over 155 I get the following:

SSL handshake failed (5).
SSL handshake failed (5).
SSL handshake failed (5).
SSL handshake failed (5).
SSL handshake failed (5).
SSL handshake failed (5).
SSL handshake failed (5).
SSL handshake failed (5).
SSL handshake failed (5).
Completed 100 requests
Completed 200 requests
Finished 200 requests

The requests still succeed:

Concurrency Level:      200
Time taken for tests:   14.481 seconds  
Complete requests:      200
Failed requests:        0

I have tested it numerous times and the SSL handshake only fails once the concurrency exceeds 155. Can anybody explain to me how they could be directly related?

Answer 1

I asked my question on Server Fault and I got a pretty good answer. I'll refrain from deleting the question in the hope it will help people get re-directed to a viable answer.

Link to answer
Apache Bench: SSL handshake failing directly related to concurrency level