tokens: ['Figure', '', '', 'Message', 'sequence', 'chart', 'for', 'offline', 'charging', 'of', 'CONF', 'service', '', 'User', 'creating', 'a', 'conference', '', 'The', 'communication', 'is', 'initiated', 'by', 'UE', 'by', 'sending', 'an', 'SIP', 'INVITE', 'request', 'to', 'SCSCF', 'And', 'SCSCF', 'sends', 'back', '', 'Trying', 'reponse', 'to', 'inform', 'UE', 'to', 'wait', 'for', 'a', 'while', 'because', 'the', 'request', 'is', 'being', 'treated', '', 'SCSCF', 'transfers', 'SIP', 'INVITE', 'request', 'from', 'UE', 'to', 'CONF', 'AS', 'and', 'the', 'CONF', 'AS', 'sends', 'back', '', 'Trying', 'response', 'to', 'inform', 'SCSCF', 'to', 'wait', 'for', 'a', 'while', 'because', 'the', 'request', 'is', 'being', 'treated', '', 'The', 'CONF', 'AS', 'allocates', 'the', 'conference', 'URI', '', 'After', 'the', 'media', 'resource', 'negociation', 'process', 'the', 'CONF', 'AS', 'sends', 'back', 'SIP', '', 'OK', 'response', '', 'The', 'CONF', 'AS', 'sends', 'Charging', 'Data', 'Request', 'StartCharging', 'Data', 'Request', 'Event', 'to', 'CDF', 'then', 'the', 'CDF', 'openscreates', 'an', 'AS', 'CDR', 'for', 'the', 'conference', 'with', 'CONF', 'indication', 'on', 'the', 'AS', 'CDR', 'and', 'returns', 'Charging', 'Data', 'Response', 'to', 'the', 'CONF', 'AS']