CHI G - Txn ID re-use before comp ack being sent in case of ExpCompAck transfers

Scenario: 

1. Requester sends a Read transaction with unique Src ID and TXN ID with Expcompack set to 1. 

2. The data flow continues, and the requester receives the comp data packet with same TXN ID and DBID. 

3. The requester sends back the compack response with received DBID as TXN ID. 

The question is can the TXN ID be re-used after #2 or #3 has to be completed before the TXN ID can be re-used.