Methods, systems, and computer readable media for preserving network bandwidth during network address translation (NAT) device unavailability or after NAT device reboot

A system for preserving network bandwidth during network address translation (NAT) device unavailability or after NAT device reboot, the system comprising:

• a session initiation protocol (SIP) proxy including at least one processor and a memory;
• a NAT device to SIP endpoint correlation manager implemented by the at least one processor for receiving messages from SIP endpoints, determining that at least some of the SIP endpoints are located behind a NAT device, determining that the NAT device is potentially unavailable or has potentially rebooted, testing reachability of the at least some of the SIP endpoints located behind the NAT device and determining that the at least some of the SIP endpoints are unreachable, in response to determining, from the testing, that the at least some of the SIP endpoints are unreachable, determining that the NAT device is unavailable or has rebooted and classifying all of the SIP endpoints located behind the NAT device as unreachable, and rejecting SIP messages directed towards the SIP endpoints located behind the NAT device, wherein rejecting the SIP messages directed towards the SIP endpoints located behind the NAT device includes:
• receiving the SIP messages directed towards the SIP endpoints located behind the NAT device;
• refraining from forwarding the SIP messages directed towards the SIP endpoints located behind the NAT device;
• and
• transmitting, to originators of the SIP messages directed towards the SIP endpoints located behind the NAT device, error response messages with Retry-After headers that each include a time value that defines a time interval that a receiving entity should wait before sending SIP message traffic to one of the SIP endpoints located behind the NAT device and a value indicating that the one of the SIP endpoints located behind the NAT device is unreachable and/or that the NAT device has rebooted or is unavailable.

A non-transitory computer readable medium having stored thereon executable instructions that when executed by a processor of a computer control the computer to perform steps comprising:

• receiving, by a session initiation protocol (SIP) proxy, messages from SIP endpoints;
• determining, by the SIP proxy, that at least some of the SIP endpoints are located behind a network address translation (NAT) device;
• determining, by the SIP proxy, that the NAT device is potentially unavailable or has potentially rebooted;
• testing, by the SIP proxy, reachability of the at least some of the SIP endpoints located behind the NAT device and determining that the at least some of the SIP endpoints are unreachable;
• in response to determining, from the testing, that the at least some of the SIP endpoints are unreachable, determining that the NAT device is unavailable or has rebooted and classifying, by the SIP proxy, all of the SIP endpoints located behind the NAT device as unreachable;
• and
• rejecting, by the SIP proxy, SIP messages directed towards the SIP endpoints located behind the NAT device, wherein rejecting, by the SIP proxy, the SIP messages directed towards the SIP endpoints located behind the NAT device includes:
• receiving, by the SIP proxy, the SIP messages directed towards the SIP endpoints located behind the NAT device;
• refraining, by the SIP proxy, from forwarding the SIP messages directed towards the SIP endpoints located behind the NAT device;
• and
• transmitting, by the SIP proxy and to originators of the SIP messages directed towards the SIP endpoints located behind the NAT device, error response messages with Retry-After headers that each includes a time value that defines a time interval that a receiving entity should wait before sending SIP message traffic to one of the SIP endpoints located behind the NAT device and a value indicating that the one of the SIP endpoints located behind the NAT device is unreachable and/or that the NAT device has rebooted or is unavailable.