Fault routing of an emergency communication

A method, comprising:

• delivering, from a first network node to a second network node, a first session initiation protocol (SIP) message to establish a communication session with a user device that originated the communication session, the first SIP message comprising an emergency service routing number (ESRN) and a first trunk group number associated with a public safety answering point (PSAP), the first trunk group number being related to the ESRN;
• receiving a second SIP message from the second network node, the second SIP message having a second trunk group number different from the first trunk group number;
• determining, based on the second SIP message having the second trunk group number different from the first trunk group number, the second network node is unavailable for the ESRN;
• in response to the second network node being unavailable, querying, at the first network node, a database for data associated with the communication session;
• in response to the second network node being unavailable for the ESRN, generating, at the first network node, a first identifier associated with the data;
• updating, at the first network node, the first identifier with a second identifier of the user device that originated the communication session;
• and
• delivering, by the first network node, the updated first identifier to a third network node.

An apparatus, comprising:

• one or more processors;
• and
• a memory storing processor executable instructions that, when executed by the one or more processors, cause the apparatus to:
• deliver a first session initiation protocol (SIP) message to a first network node to establish a communication session with a user device that originated the communication session, the first SIP message comprising an emergency service routing number (ESRN) and a first trunk group number associated with a public safety answering point (PSAP), the first trunk group number being related to the ESRN;
• receive a second SIP message from the first network node, the second SIP message having a second trunk group number different from the first trunk group number;
• determine, based on the second SIP message having the second trunk group number different from the first trunk group number, the first network node is unavailable for the ESRN;
• query a database for data associated with the communication session;
• in response to the second network node being unavailable for the ESRN, generate a first identifier associated with the data;
• update the first identifier with a second identifier of the user device that originated the communication session, wherein the update yields an updated identifier;
• and
• deliver the updated identifier to the first network node.