When a message is received with a recognized information element that is not marked as comprehension required and is not defined to be contained in that message, the receiving entity shall(except as noted below) treat the information element as an unrecognized information element and follow the procedures defined in 5.8.7.1. When a message is received with a recognized information element that is marked as comprehension required and is not defined to be contained in that message, the receiving entity shall follow the procedures of 5.8.6.1.
Note - Some implementations may chose to process unexpected recognized information elements when the procedure for processing the information element is independent of the message in which it is received.