The answer is that "Security Association Identifier, SAID".
The Security Association Identifier (SAID) refers to a 16-bit identifier that is shared between the BS and the SS that interestingly distinguishes an SA.There are three kinds of security affiliations:a) the SA for unicast associationsb) the Group Security Association (GSA) which is for multicast gatherings c) and the MBS Group Security Association (MBSGSA) which is for MBS administrations.