[gwright]

After working with 0MQ for a while I felt that this sort of summary was misleading.

I came to think of 0MQ as a multi-point data link abstraction (i.e. layer 2). The API abstracts over sockets, IPC message queues, and in-process message queues as the virtual layer-1 transports.

I say it is a layer-2 abstraction because 0MQ doesn't provide any mechanism for addressing or transparently routing over an internet of connected 0MQ networks. You can do source-based routing by explicitly naming the intermediate hops but this is more like intellegent layer-2 bridging than traditional layer-3 routing. There is no concept of a layer-3 address or naming scheme of any kind and there any important layer-4 features (re-transmissions, flow-control, out-of-order resequencing).

The message structure and fan-in/fan-out features are very useful but they are operating at a layer-2 level, not a 3, 4, 5, etc. layer, from my perspective.

It has been about a year since I spent time with 0MQ so perhaps it has evolved beyond what I experienced.