ZERO DOWNTIME SERVER UPGRADE

1 . A method for upgrading a first server, comprising:

causing the first server to initiate a deny new service mode;

migrating an endpoint networked to the first server to be networked to a second server; and

in response to the endpoint being networked to the second server, performing an upgrade on the first server.

2 . The method of claim 1 , wherein migrating the endpoint networked to the first server to be networked to the second server comprises:

generating a Session Initiation Protocol (SIP) PUBLISH message comprising an identifier of the endpoint, an action set to “ReHome”, and an identifier of the second server; and

sending the SIP PUBLISH message to a session manager; and

wherein the session manager processes the SIP PUBLISH message, and in response to receiving a call for the endpoint, generates a SIP INVITE message for the endpoint and sends the SIP INVITE message to cause the second server to connect to the endpoint.

3 . The method of claim 1 , further comprising, upon completion of the upgrade on the first server, migrating the endpoint networked to the second server to be networked to the first server.

4 . The method of claim 3 , wherein migrating the endpoint networked to the second server to be networked to the first server comprises:

generating a Session Initiation Protocol (SIP) PUBLISH message comprising an identifier of the endpoint, an action set to “ReHome”, and an identifier of the first server; and

sending the SIP PUBLISH message to a session manager; and

wherein the session manager processes the SIP PUBLISH message, and in response to receiving a call for the endpoint, generates a SIP INVITE message for the endpoint and sends the SIP INVITE message to the first server to cause the first server to connect to the endpoint.

5 . The method of claim 1 , further comprising:

generating a SIP OPTIONS message and sending the SIP OPTIONS message to the first server;

in response to the SIP OPTIONS message, receiving a SIP 503 SERVICE UNAVAILABLE message from the first server; and

in response to the SIP 503 SERVICE UNAVAILABLE message, causing a session manager to reroute new calls for the endpoint to the second server.

6 . The method of claim 5 , wherein generating the SIP OPTIONS message and sending the SIP OPTIONS message is performed while at least one call is ongoing and comprising a customer communication device, an agent communication device and therebetween the first server.

7 . The method of claim 5 , further comprising:

receiving a second call addressed to an agent communication device; and

in response to the SIP OPTIONS message, routing the second call to the agent communication device via the second server.

8 . The method of claim 1 , wherein at least one of the first server or the second server comprises a communication manager server.

9 . A session manager, comprising:

at least one processor coupled to a computer memory, the computer memory comprising instructions that, when read by the at least one processor, cause the at least one processor to perform:

cause a first server to initiate a deny new service mode;

migrate an endpoint networked to the first server to be networked to a second server; and

in response the endpoint networked to the second server, perform an upgrade on the first server.

10 . The session manager of claim 9 , wherein migrating the endpoint networked to the first server to be networked to the second server comprises:

generating a Session Initiation Protocol (SIP) PUBLISH message comprising an identifier of the endpoint, an action set to “ReHome”, and an identifier of the second server; and

sending the SIP PUBLISH message to the session manager; and

wherein the session manager processes the SIP PUBLISH message, and in response to receiving a call for the endpoint, generates a SIP INVITE message for the endpoint and sends the SIP INVITE message to cause the second server to connect to the endpoint.

11 . The session manager of claim 9 , further comprising, upon completion of the upgrade on the first server, migrating the endpoint networked to the second server to be networked to the first server.

12 . The session manager of claim 11 , wherein migrating the endpoint networked to the second server to be networked to the first server comprises:

generating a Session Initiation Protocol (SIP) PUBLISH message comprising an identifier of the endpoint, an action set to “ReHome”, and an identifier of the first server; and

sending the SIP PUBLISH message to a session manager; and

wherein the session manager processes the SIP PUBLISH message, and in response to receiving a call for the endpoint, generates a SIP INVITE message for the endpoint and sends the SIP INVITE message to the first server to cause the first server to connect to the endpoint.

13 . The session manager of claim 9 , further comprising:

before completion of the upgrade on the first server, generating a SIP OPTIONS message and sending the SIP OPTIONS message to the first server;

in response to the SIP OPTIONS message, receiving a SIP 503 SERVICE UNAVAILABLE message from the first server; and

in response to the SIP 503 SERVICE UNAVAILABLE message, causing a session manager to reroute new calls for the endpoint to the second server.

14 . The session manager of claim 13 , wherein generating the SIP OPTIONS message and sending the SIP OPTIONS message are performed while at least one call is ongoing and comprising a customer communication device, an agent communication device and the first server is a portion of the at least one call therebetween.

15 . The session manager of claim 13 , further comprising:

receiving a second call addressed to an agent communication device; and

in response to the SIP OPTIONS message, routing the second call to the agent communication device via the second server.

16 . The session manager of claim 9 , wherein at least one of the first server or the second server comprises a communication manager server.

17 . A computer-readable medium maintained in a non-transitory computer memory that, when read by a processor, causes the processor to perform:

causing a first server to initiate a deny new service mode;

migrating an endpoint networked to the first server to be networked to a second server; and

in response to the endpoint networked to the second server, performing an upgrade on the first server.

18 . The computer-readable medium of claim 17 , wherein migrating the endpoint networked to the first server to be networked to the second server comprises:

generating a Session Initiation Protocol (SIP) PUBLISH message comprising an identifier of the endpoint, an action set to “ReHome”, and an identifier of the second server; and

sending the SIP PUBLISH message to a session manager; and

wherein the session manager processes the SIP PUBLISH message, and in response to receiving a call for the endpoint, generates a SIP INVITE message for the endpoint and sends the SIP INVITE message to cause the second server to connect to the endpoint.

19 . The computer-readable medium of claim 17 , further comprising instructions to, upon completion of the upgrade on the first server, migrate the endpoint networked to the second server to be networked to the first server.

20 . The computer-readable medium of claim 19 , wherein migrating the endpoint networked to the second server to be networked to the first server comprises:

generating a Session Initiation Protocol (SIP) PUBLISH message comprising an identifier of the endpoint, an action set to “ReHome”, and an identifier of the first server; and

sending the SIP PUBLISH message to a session manager; and

wherein the session manager processes the SIP PUBLISH message, and in response to receiving a call for the endpoint, generates a SIP INVITE message for the endpoint and sends the SIP INVITE message to the first server to cause the first server to connect to the endpoint.