Many years ago I did programmeing on a telephony application which communicated using the old SS7 network. In here you, as a layer 4 protocol entity, can send a

Many years ago I did programmeing on a telephony application which communicated using the old SS7 network. In here you, as a layer 4 protocol entity, can send a "link selection" key in the protocol messages. It's just a 4 bit number (or 8 if it's ANSI SS7 instead of ITU , iirc) per message, and the switches maps this number to a physical downstream link, often in a configurable fashion. This is pretty neat, as the application can default to a round robin distribution and dynamically weigth the link selection key based on detected congestion/overload to shift the load to other links - since then I've often wished the TCP/IP world offered something similar.