Difference between RRCResumeRequest and RRCResumeRequest1

There are two messages has been defined on 38.331 related to rrc resume request.
1. RRCResumeRequest 
2. RRCResumeRequest1

Only difference between this two message is the resumeIdentity used in it.

RRCResumeRequest  uses shortI-RNTI-Value as  resumeIdentity.
Where as RRCResumeRequest1 uses I-RNTI-Value as resumeIdentity. 

Selection of this messages while resuming the rrc connection depends on SIB1 content.
In SIB1 there is an IE - useFullResumeID
If this IE is present then UE shall use useFullResumeID (I-RNTI-Value) as  resumeIdentity  - which means it shall trigger RRCResumeRequest1.


5.3.13.3 Actions related to transmission of RRCResumeRequest or RRCResumeRequest1 message

The UE shall set the contents of RRCResumeRequest or RRCResumeRequest1 message as follows:
1> if field useFullResumeID is signalled in SIB1:
      2> select RRCResumeRequest1 as the message to use;
      2> set the resumeIdentity to the stored fullI-RNTI value;
1> else:
      2> select RRCResumeRequest as the message to use;

      2> set the resumeIdentity to the stored shortI-RNTI value;



SuspendConfig ::= SEQUENCE {
                           fullI-RNTI I-RNTI-Value,
                          shortI-RNTI ShortI-RNTI-Value,
                          ran-PagingCycle PagingCycle,
                          ran-NotificationAreaInfo RAN-NotificationAreaInfo OPTIONAL, -- Need M
                          t380 PeriodicRNAU-TimerValue OPTIONAL, -- Need R
                          nextHopChainingCount NextHopChainingCount,
...

}

UE will receive fullI-RNTI -> I-RNTI-Value and shortI-RNTI ->ShortI-RNTI-Value in RRCRelease message.