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Aeron MDC vs Unicast – Key Differences

When it comes to the UDP protocol, you can either use Unicast, which sends messages one to one, or multicast, which sends messages to many

Overview

This guide compares Aeron's two main communication patterns for UDP-based messaging, helping you choose the right approach for your use case.

Comparison Table

Feature Aeron Unicast Aeron MDC (Multi-Destination-Cast)
Protocol UDP UDP
Communication Type 1 Publisher → 1 Subscriber 1 Publisher → N Subscribers
Control Mode Not required manual or dynamic control mode required
Subscriber Registration Static (hardcoded endpoints) Dynamic or manual registration of subscribers
Publisher Setup Uses endpoint=... Uses control-mode=dynamic + control=host:port
Subscriber Setup Uses endpoint=... Uses endpoint=...|control=...|control-mode=dynamic
Multicast Needed? ❌ No ❌ No (achieves fanout via unicast)
Dynamic Join/Leave ❌ No (fixed peer) ✅ Yes (subscribers can join/leave dynamically)
Number of Subscribers 1 only Multiple
Efficiency Very efficient (1 send) Less efficient (N sends for N subscribers)
Flexibility Low High
Typical Use Case Point-to-point communication Broadcast-like use case, clusters, logs, market data

Channel Configuration Examples

Unicast Channel

1
aeron:udp?endpoint=localhost:40123

MDC (Publisher)

1
aeron:udp?control-mode=dynamic|control=localhost:40123

MDC (Subscriber)

1
aeron:udp?endpoint=localhost:40124|control-mode=dynamic|control=localhost:40123

Key Points

MDC Implementation

MDC uses unicast UDP under the hood, but gives multicast-like fan-out. This approach avoids the complexity of multicast infrastructure while providing broadcast capabilities.

When to Use MDC

  • Pub/sub patterns without relying on multicast infrastructure
  • Aeron Cluster and high-availability systems
  • Market data distribution scenarios
  • Log replication across multiple nodes

See Also