tokens: ['For', 'PDP', 'ContextsEPS', 'bearers', 'used', 'to', 'carry', 'IMS', 'media', 'flows', 'specific', 'policies', 'may', 'be', 'applied', 'The', 'policy', 'includes', 'packet', 'filtering', 'which', 'enables', 'a', 'specific', 'charging', 'for', 'these', 'PDP', 'ContextsEPS', 'bearers', 'see', 'GPP', 'TS', '', '', 'The', 'creation', 'of', 'a', 'PDP', 'ContextEPS', 'bearer', 'to', 'be', 'used', 'to', 'carry', 'media', 'flows', 'involves', 'interaction', 'between', 'the', 'MSUE', 'and', 'the', 'GGSNPGW', 'and', 'between', 'the', 'GGSNPGW', 'and', 'the', 'PCRF', 'The', 'interaction', 'between', 'the', 'GGSNPGW', 'and', 'the', 'PCRF', 'ie', 'the', 'Gx', 'interface', 'is', 'described', 'in', 'detail', 'in', 'GPP', 'TS', '', '', 'The', 'interaction', 'between', 'the', 'MSUE', 'and', 'GGSNPGW', 'is', 'described', 'in', 'GPP', 'TS', '', '', 'If', 'Gx', 'is', 'enabled', 'for', 'the', 'APN', 'the', 'GGSNPGW', 'contacts', 'the', 'PCRF', 'selected', 'during', 'the', 'establishment', 'of', 'the', 'APN']