tokens: ['SIP', 'is', 'a', 'core', 'protocol', 'in', 'IMS', 'used', 'for', 'initiating', 'managing', 'and', 'terminating', 'realtime', 'sessions', 'involving', 'voice', 'video', 'and', 'messaging', 'In', 'TS', '', 'SIP', 'is', 'vital', 'for', 'managing', 'communication', 'sessions', 'between', 'the', 'UE', 'and', 'the', 'IMS', 'core', 'via', 'the', 'PCSCF', 'ICSCF', 'and', 'SCSCF']