NewConn establishes a session and talks KCP protocol over a packet connection.

NewKCP create a new kcp state machine 'conv' must be equal in the connection peers, or else data will be silently rejected.

NewTimedSched creates a parallel-scheduler with given parallelization.

need to send IKCP_CMD_WASK.

need to send IKCP_CMD_WINS.

cmd: ack.

cmd: push data.

cmd: window probe (ask).

cmd: window size (tell).

7 secs to probe window size.

up to 120 secs to probe window.

normal min rto.

no delay min rto.

DefaultSnmp is the global KCP connection statistics collector.

SystemTimedSched is the library level timed-scheduler.

KCP defines a single KCP connection.

Snmp defines network statistics indicator.

TimedSched represents the control struct for timed parallel scheduler.