HTTP Keep-Alive aka Persistant Connection with Apache httpd

HTTP Keep-Alive is also known as persistent connection. In the HTTP response you have

Connection:Keep-Alive
Keep-Alive:timeout=5, max=100

And to configure this in Apache httpd

#
# KeepAlive: Whether or not to allow persistent connections (more than
# one request per connection). Set to "Off" to deactivate.
#
KeepAlive On

#
# MaxKeepAliveRequests: The maximum number of requests to allow
# during a persistent connection. Set to 0 to allow an unlimited amount.
# We recommend you leave this number high, for maximum performance.
#
MaxKeepAliveRequests 100

#
# KeepAliveTimeout: Number of seconds to wait for the next request from the
# same client on the same connection.
#
KeepAliveTimeout 5

NOTE: MaxKeepAlive is a counter that counts down for each request and after that is a new HTTP session renegotiated, that can be costly if HTTPS is used, but is necessary to clean up lingering HTTP sessions.