ZeroMQ from a high level

Regular Sockets
Point to Point
Stream of bytes
Buffering
Multiple transports, tcp, udp, …

Messaging
Messages are atomic
Messages can be routed
Messages can sit around
Messages are delivered

Rise of Big MQ
App ------   ------ App
AMQP Broker
App ------ ------ App

Drawbacks of Big MQ
Lots of Complexity
HA is a challenge

Speed is also a challenge
ZeroMQ is much faster, its wire protocol is simpler than AMQP, just a framing protocol
Higher throughput than raw sockets
due to Intelligent message batching and edge case optimizations

ZeroMQ lacks a directory service
DNS isn't dynamic enough
Zookeeper or Doozer could work
https://github.com/ha/doozerd