Section: 6.1.2 Grouped Information Elements
Content: Information elements can contain other IEs. This type of IE is called "Grouped IEs". Grouped IEs have a length value in the TLIV encoding, which includes the added length of all the embedded IEs. Overall coding of a grouped information element with 4 octets long IE header is defined in clause 8.2 "Information Element Format". Each information element within a grouped IE also shall also contain 4 octets long IE header. Grouped IEs are not marked by any flag or limited to a specific range of IE type values. The clause describing an IE in this specification shall explicitly state if it is grouped. NOTE 1: Each entry into each Grouped IE creates a new scope level. Exit from the grouped IE closes the scope level. The GTPv2 message level is the top most scope. This is analogous to the local scope of a subroutine/function. If more than one grouped information elements of the same type, but for a different purpose are sent with a message, these IEs shall have different Instance values. If more than one grouped information elements of the same type and for the same purpose are sent with a message, these IEs shall have exactly the same Instance value to represent a list. NOTE 2: For instance, all "Bearer Contexts Modified" IEs of the type "Bearer Context" in a "Modify Bearer Response" message shall have the Instance value of 0, while all "Bearer Contexts Marked for Removal" IEs of the type "Bearer Context" in the same message shall have the Instance value of 1.