Congestion Control¶

MafiaNet implements adaptive congestion control to maximize throughput while avoiding network congestion. Understanding and tuning these settings is essential for optimal game networking performance.

Overview¶

The congestion control system:

Monitors packet loss and round-trip times
Adjusts send rate dynamically
Prioritizes reliable over unreliable traffic
Supports different algorithms for different use cases

Basic Configuration¶

Setting bandwidth limits:

MafiaNet::RakPeerInterface* peer = MafiaNet::RakPeerInterface::GetInstance();

// Limit outgoing bandwidth (bytes per second)
peer->SetPerConnectionOutgoingBandwidthLimit(50000);  // 50 KB/s

// Set unlimited (default)
peer->SetPerConnectionOutgoingBandwidthLimit(0);

Checking connection quality:

MafiaNet::RakNetStatistics stats;
peer->GetStatistics(remoteAddress, &stats);

printf("RTT: %d ms\n", peer->GetAveragePing(remoteAddress));
printf("Packet loss: %.2f%%\n", stats.packetlossLastSecond * 100.0f);
printf("Bandwidth: %d bytes/sec\n", stats.BPSLimitByCongestionControl);

Algorithm Selection¶

Configure in RakNetDefinesOverrides.h:

// Sliding window (TCP-like, recommended for most games)
#define USE_SLIDING_WINDOW_CONGESTION_CONTROL 1

// Fixed rate (no congestion control)
#define USE_SLIDING_WINDOW_CONGESTION_CONTROL 0

Priority and Reliability¶

Message priorities:

// Immediate send (highest priority)
peer->Send(&bs, IMMEDIATE_PRIORITY, RELIABLE_ORDERED, 0, addr, false);

// High priority (game state)
peer->Send(&bs, HIGH_PRIORITY, RELIABLE_ORDERED, 0, addr, false);

// Medium priority (player updates)
peer->Send(&bs, MEDIUM_PRIORITY, UNRELIABLE_SEQUENCED, 0, addr, false);

// Low priority (chat, non-critical)
peer->Send(&bs, LOW_PRIORITY, RELIABLE, 0, addr, false);

Reliability types:

RELIABLE - Guaranteed delivery, any order
RELIABLE_ORDERED - Guaranteed delivery, in order
RELIABLE_SEQUENCED - Guaranteed, newest only
UNRELIABLE - No guarantee, lowest overhead
UNRELIABLE_SEQUENCED - No guarantee, newest only

Tuning Parameters¶

// MTU discovery (finds optimal packet size)
peer->SetMTUSize(1492);  // Default, good for most networks

// Timeout settings
peer->SetTimeoutTime(10000, remoteAddress);  // 10 seconds

// Packet ordering channels (0-31)
// Use different channels for independent data streams
peer->Send(&bs, HIGH_PRIORITY, RELIABLE_ORDERED, 0, addr, false);  // Channel 0
peer->Send(&bs2, HIGH_PRIORITY, RELIABLE_ORDERED, 1, addr, false); // Channel 1

Statistics Monitoring¶

MafiaNet::RakNetStatistics stats;
peer->GetStatistics(addr, &stats);

// Key metrics
stats.messageInSendBuffer;        // Pending messages
stats.bytesInSendBuffer;          // Pending bytes
stats.packetlossLastSecond;       // Recent packet loss
stats.BPSLimitByCongestionControl; // Current bandwidth limit