The header frame is a fixed size and currently it is possible to put more data in to it than the AMQP specification says should be allowed.
In Qpid this does not matter as the Broker will read these extra large header frames. However, other brokers may not be so gracious.
We should throw an execption to the user when their data addition to the headers will put their current message over the defined framesize.
Quite what the impact this would be on the broker if it receives a message from a client with a large frame size and has to send to a client with a small frame size.
As a result this should be a configurable option for when we are running Qpid-Qpid.