Get the timing and delayed ACKs right(er)
This commit is contained in:
Keith Winstein
+110
-46
@@ -16,7 +16,9 @@ Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState
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received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
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last_receiver_state( initial_remote ),
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fragments(),
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verbose( false )
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verbose( false ),
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next_ack_time( timestamp() ),
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next_send_time( timestamp() )
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{
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/* server */
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}
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@@ -32,7 +34,9 @@ Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState
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received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
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last_receiver_state( initial_remote ),
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fragments(),
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verbose( false )
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verbose( false ),
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next_ack_time( timestamp() ),
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next_send_time( timestamp() )
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{
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/* client */
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}
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@@ -40,7 +44,7 @@ Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState
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template <class MyState, class RemoteState>
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unsigned int Transport<MyState, RemoteState>::send_interval( void )
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{
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unsigned int SEND_INTERVAL = connection.timeout() / 10;
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int SEND_INTERVAL = lrint( ceil( (connection.get_SRTT() - ACK_DELAY) / 2.0 ) );
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if ( SEND_INTERVAL < SEND_INTERVAL_MIN ) {
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SEND_INTERVAL = SEND_INTERVAL_MIN;
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} else if ( SEND_INTERVAL > SEND_INTERVAL_MAX ) {
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@@ -50,56 +54,105 @@ unsigned int Transport<MyState, RemoteState>::send_interval( void )
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return SEND_INTERVAL;
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}
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/* Returns the number of ms to wait until next (possible) event */
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template <class MyState, class RemoteState>
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int Transport<MyState, RemoteState>::tick( void )
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int Transport<MyState, RemoteState>::wait_time( void )
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{
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/* Determine if a new diff or empty ack needs to be sent */
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if ( timestamp() - sent_states.back().timestamp >= send_interval() ) {
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/* Update assumed receiver state */
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update_assumed_receiver_state();
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/* Cut out common prefix of all states */
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rationalize_states();
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/* Send diffs or ack */
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send_to_receiver();
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return send_interval();
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}
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int64_t wait = sent_states.back().timestamp + send_interval() - timestamp();
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if ( wait < 0 ) {
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wait = 0;
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if ( connection.pending_timestamp() && ( next_ack_time > timestamp() + ACK_DELAY ) ) {
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next_ack_time = timestamp() + ACK_DELAY;
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}
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uint64_t next_wakeup = next_ack_time;
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if ( !(current_state == sent_states.back().state) ) { /* pending data to send */
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if ( next_send_time > timestamp() + SEND_MINDELAY ) {
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next_send_time = timestamp() + SEND_MINDELAY;
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}
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if ( next_send_time < sent_states.back().timestamp + send_interval() ) {
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next_send_time = sent_states.back().timestamp + send_interval();
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}
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if ( next_send_time < next_wakeup ) {
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next_wakeup = next_send_time;
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}
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}
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if ( !connection.get_attached() ) {
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return -1;
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}
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if ( next_wakeup > timestamp() ) {
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return next_wakeup - timestamp();
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} else {
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return 0;
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}
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return wait;
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}
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/* Send data or an ack if necessary */
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::send_to_receiver( void )
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void Transport<MyState, RemoteState>::tick( void )
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{
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wait_time();
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if ( !connection.get_attached() ) {
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return;
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}
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string diff = current_state.diff_from( assumed_receiver_state->state );
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if ( diff.empty() ) {
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/* send empty ack */
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if ( (!connection.pending_timestamp())
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&& (timestamp() - sent_states.back().timestamp < int64_t( ACK_INTERVAL ))
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&& (sent_states.back().num > 0) ) {
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return;
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}
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uint64_t new_num = sent_states.back().num + 1;
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send_in_fragments( diff, new_num, false );
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sent_states.push_back( TimestampedState<MyState>( timestamp(), new_num, current_state ) );
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if ( (timestamp() < next_ack_time)
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&& (timestamp() < next_send_time) ) {
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return;
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}
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/* Determine if a new diff or empty ack needs to be sent */
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/* Update assumed receiver state */
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update_assumed_receiver_state();
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/* Cut out common prefix of all states */
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rationalize_states();
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string diff = current_state.diff_from( assumed_receiver_state->state );
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if ( diff.empty() && (timestamp() >= next_ack_time) ) {
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/*
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if ( verbose )
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fprintf( stderr, "Sending empty ack (ts=%d, next_send=%d, next_ack=%d)\n",
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(int)timestamp() % 100000,
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(int)next_send_time % 100000,
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(int)next_ack_time % 100000 );
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*/
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send_empty_ack();
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return;
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}
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if ( !diff.empty() && ( (timestamp() >= next_send_time)
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|| (timestamp() >= next_ack_time) ) ) {
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/* Send diffs or ack */
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/*
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if ( verbose )
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fprintf( stderr, "Sending packet (ts=%d, next_send=%d, next_ack=%d)\n",
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(int)timestamp() % 100000,
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(int)next_send_time % 100000,
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(int)next_ack_time % 100000 );
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*/
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send_to_receiver( diff );
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}
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::send_empty_ack( void )
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{
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assert ( timestamp() >= next_ack_time );
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uint64_t new_num = sent_states.back().num + 1;
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send_in_fragments( "", new_num, false );
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sent_states.push_back( TimestampedState<MyState>( sent_states.back().timestamp, new_num, current_state ) );
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next_ack_time = timestamp() + ACK_INTERVAL;
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::send_to_receiver( string diff )
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{
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uint64_t new_num;
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if ( current_state == sent_states.back().state ) { /* previously sent */
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new_num = sent_states.back().num;
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@@ -138,6 +191,8 @@ void Transport<MyState, RemoteState>::send_to_receiver( void )
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/* ("probably" because the FIRST size-exceeded datagram doesn't get an error) */
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assumed_receiver_state = sent_states.end();
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assumed_receiver_state--;
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next_ack_time = timestamp() + ACK_INTERVAL;
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next_send_time = -1;
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}
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template <class MyState, class RemoteState>
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@@ -149,16 +204,19 @@ void Transport<MyState, RemoteState>::update_assumed_receiver_state( void )
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transmitted recently enough ago */
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assumed_receiver_state = sent_states.begin();
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for ( typename list< TimestampedState<MyState> >::iterator i = sent_states.begin();
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i != sent_states.end();
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i++ ) {
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typename list< TimestampedState<MyState> >::iterator i = sent_states.begin();
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i++;
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while ( i != sent_states.end() ) {
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assert( now >= i->timestamp );
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if ( int(now - i->timestamp) < connection.timeout() ) {
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if ( int(now - i->timestamp) < connection.timeout() + ACK_DELAY ) {
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assumed_receiver_state = i;
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} else {
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return;
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}
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i++;
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}
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}
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@@ -229,6 +287,11 @@ void Transport<MyState, RemoteState>::recv( void )
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return;
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}
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}
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/*
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if ( verbose )
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fprintf( stderr, "[%d] Received state %d [ack %d]\n",
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(int)timestamp() % 100000, (int)new_state.num, (int)inst.ack_num );
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*/
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received_states.push_back( new_state );
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}
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}
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@@ -318,10 +381,11 @@ void Transport<MyState, RemoteState>::send_in_fragments( string diff, uint64_t n
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connection.send( s, send_timestamp );
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if ( verbose ) {
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fprintf( stderr, "Sent [%d=>%d] frag %d, ack=%d, throwaway=%d, len=%d, frame rate=%.2f\n",
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(int)inst.old_num, (int)inst.new_num, (int)inst.fragment_num,
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fprintf( stderr, "[%d] Sent [%d=>%d] frag %d, ack=%d, throwaway=%d, len=%d, frame rate=%.2f, timeout=%d\n",
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(int)(timestamp() % 100000), (int)inst.old_num, (int)inst.new_num, (int)inst.fragment_num,
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(int)inst.ack_num, (int)inst.throwaway_num, (int)inst.diff.size(),
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1000.0 / (double)send_interval() );
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1000.0 / (double)send_interval(),
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(int)connection.timeout() );
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}
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} while ( !diff.empty() );
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}
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