Method and apparatus for implementing a presence-based universal camp-on feature in packet-based telephony systems

A method comprising:

• a first packet-based device subscribing to a line status of each of multiple packet-based devices, wherein the first packet-based device is not one of the multiple packet-based devices, such that each of the multiple packet-based devices responsively notifies the first packet-based device of (i) a current line status of the respective packet-based device and (ii) any changes to the line status of the respective packet-based device;
• the first packet-based device receiving a first notification from a second packet-based device, wherein the second packet-based device is one of the multiple packet-based devices, when the line status of the second packet-based device is in a busy state;
• after receiving the first notification, the first packet-based device receiving a second notification from the second packet-based device when the line status of the second packet-based device is in an idle state;
• responsive to receiving the sequence of the first notification followed by the second notification, the first packet-based device prompting a first user of the first packet-based device to establish a communication session with the second packet-based device;
• and
• after prompting the first user, the first packet-based device receiving an accept-call command from the user, and responsively establishing the communication session with the second packet-based device.

A packet-based telephone, comprising:

• a user interface;
• a network interface;
• a processor;
• and
• a data storage;
• wherein the data storage comprises a computer usable medium having control logic stored therein, the control logic comprising computer readable program code executable by the processor for causing the packet-based telephone to:
• subscribe the packet-based telephone to a line status of a packet-based device, such that the packet-based device responsively notifies the packet-based telephone of (i) a current line status of the packet-based device and (ii) any changes to the line status of the packet-based device;
• receive via the network interface a first notification from the packet-based device when the line status of the packet-based device is in a busy state;
• after receiving the first notification, receive via the network interface a second notification from the packet-based device when the line status of the packet-based device is in an idle state;
• responsive to receiving the sequence of the first notification followed by the second notification, prompt a user of the packet-based telephone via the user interface to establish a communication session with the packet-based device;
• and
• after prompting the user, receive an accept-call command from the user, and responsively establish the communication session with the packet-based device.

A method, comprising:

• a first Session Initiation Protocol (SIP) telephone transmitting a first SIP message, offering a SIP device an invitation to engage in a first communication session with the first SIP telephone;
• the first SIP telephone receiving a camp-on command from a user of the first SIP telephone to camp-on the SIP device;
• responsive to receiving the camp-on command, the first SIP telephone transmitting a second SIP message to the SIP device, subscribing the first SIP telephone to a line status of the SIP device, such that the SIP device responsively notifies the first SIP telephone of (i) a current line status of the SIP device and (ii) any changes to the line status of the SIP device;
• the first SIP telephone receiving a third SIP message from the SIP device, notifying the first SIP telephone that the line status of the SIP device is in a busy state;
• after receiving the third SIP message, the first SIP telephone receiving a fourth SIP message from the SIP device, notifying the first SIP telephone that the line status of the SIP device is in an idle state;
• responsive to receiving the sequence of the third SIP message followed by the fourth SIP message, the first SIP telephone prompting the user of the first SIP telephone to establish a second communication session with the SIP device;
• after prompting the user, the first SIP telephone receiving an accept-call command from the user of the first SIP telephone to establish the second communication session with the SIP device;
• and
• the first SIP telephone establishing the second communication session with the SIP device in response to receiving the accept-call command.

A method, comprising:

• a first Session Initiation Protocol (SIP) telephone transmitting a first SIP message, offering a second SIP telephone an invitation to engage in a first communication session with the first SIP telephone;
• the first SIP telephone receiving a camp-on command from the user of the first SIP telephone to camp-on the second SIP telephone;
• responsive to receiving the camp-on command, the first SIP telephone transmitting a second SIP message to the second SIP telephone, subscribing the first SIP telephone to a line status of the second SIP telephone, such that the second SIP telephone responsively notifies the first SIP telephone of (i) a current line status of the second SIP telephone and (ii) any changes to the line status of the second SIP telephone;
• the first SIP telephone canceling the invitation offered by the first SIP message;
• the first SIP telephone receiving a third SIP message from the second SIP telephone, notifying the first SIP telephone that the line status of the second SIP telephone is in a busy state;
• after receiving the third SIP message, the first SIP telephone receiving a fourth SIP message from the second SIP telephone, notifying the first SIP telephone that the line status of the second SIP telephone is in an idle state;
• responsive to receiving the sequence of the third SIP message followed by the fourth SIP message, the first SIP telephone prompting the user of the first SIP telephone to establish a second communication session with the second SIP telephone;
• after prompting the user, the first SIP telephone receiving an accept-call command from the user of the first SIP telephone to establish the second communication session with the second SIP telephone;
• and
• the first SIP telephone establishing the second communication session with the second SIP telephone in response to receiving the accept-call command.

A method, comprising:

• a first Session Initiation Protocol (SIP) telephone transmitting a first SIP message, offering a second SIP telephone an invitation to engage in a first communication session with the first SIP telephone;
• initiating a second communication session between the first SIP telephone and a messaging system, wherein the messaging system maintains an account associated with the second SIP telephone;
• the first SIP telephone receiving a camp-on command from the user of the first SIP telephone to camp-on the second SIP telephone;
• responsive to receiving the camp-on command, the first SIP telephone transmitting a second SIP message from the first SIP telephone to the second SIP telephone, subscribing the first SIP telephone to a line status of the second SIP telephone, such that the second SIP telephone responsively notifies the first SIP telephone of (i) a current line status of the second SIP telephone and (ii) any changes to the line status of the second SIP telephone;
• the first SIP telephone terminating the second communication session;
• the first SIP telephone receiving a third SIP message from the second SIP telephone, notifying the first SIP telephone that the line status of the second SIP telephone is in a busy state;
• after receiving the third SIP telephone, the first SIP telephone receiving a fourth SIP message from the second SIP telephone, notifying the first SIP telephone that the line status of the second SIP telephone is in an idle state;
• responsive to receiving the sequence of the third SIP message followed by the fourth SIP message, the first SIP telephone prompting the user of the first SIP telephone to establish a third communication session with the second SIP telephone;
• after prompting the user, the first SIP telephone receiving an accept-call command from the user of the first SIP telephone to establish the third communication session with the second SIP telephone;
• and
• the first SIP telephone establishing the third communication session with the second SIP telephone in response to receiving the accept-call command.

A method, comprising:

• a first Session Initiation Protocol (SIP) telephone transmitting a first SIP message, offering a second SIP telephone an invitation to engage in a first communication session with the first SIP telephone;
• the first SIP telephone receiving a second SIP message, notifying the first SIP telephone that the second SIP telephone is unavailable to engage in the first communication session, wherein the second SIP telephone is in a logged-out state;
• the first SIP telephone receiving a camp-on command from the user of the first SIP telephone to camp-on the second SIP telephone;
• responsive to receiving the camp-on command, the first SIP telephone transmitting a third SIP message a SIP proxy, subscribing the first SIP telephone to a registration status and a contact information of the second SIP telephone;
• the first SIP telephone receiving a fourth SIP message from the SIP proxy, notifying the first SIP telephone of the registration status and the contact information of the second SIP telephone, wherein the fourth SIP message indicates that the second SIP telephone is in the logged-out state;
• the first SIP telephone receiving a fifth SIP message from the SIP proxy, notifying the first SIP telephone of the registration status and the contact information of the second SIP telephone, wherein the fifth SIP message indicates that the second SIP telephone is in a logged-in state;
• responsive to receiving the fifth SIP message, the first SIP telephone transmitting a sixth SIP message to the second SIP telephone, subscribing the first SIP telephone to a line status of the second SIP telephone, such that the second SIP telephone responsively notifies the first SIP telephone of (i) a current line status of the second SIP telephone and (ii) any changes to the line status of the second SIP telephone;
• the first SIP telephone receiving a seventh SIP message from the second SIP telephone, notifying the first SIP telephone that the line status of the second SIP telephone is in a busy state;
• after receiving the seventh SIP message, the first SIP telephone receiving an eighth SIP message from the second SIP telephone, notifying the first SIP telephone that the line status of the second SIP telephone is in an idle state;
• responsive to receiving the sequence of the seventh SIP message followed by the eighth SIP message, the first SIP telephone prompting the user of the first SIP telephone to establish a second communication session with the second SIP telephone;
• after prompting the user, the first SIP telephone receiving an accept-call command from the user of the first SIP telephone into the first SIP telephone to establish the second communication session with the second SIP telephone;
• and
• the first SIP telephone establishing the second communication session with the second SIP telephone in response in response to receiving the accept-call command.

A method, comprising:

• a first Session Initiation Protocol (SIP) telephone transmitting a first SIP message, offering a second SIP telephone an invitation to engage in a first communication session with the first SIP telephone;
• the first SIP telephone receiving a camp-on command from the user of the first SIP telephone to camp-on the second SIP telephone;
• responsive to receiving the camp-on command, the first SIP telephone transmitting a second SIP message, subscribing the first SIP telephone to a registration status and a contact information of the second SIP telephone;
• the first SIP telephone receiving a third SIP message, notifying the first SIP telephone of the registration status and the contact information of the second SIP telephone;
• the first SIP telephone transmitting a fourth SIP message to the second SIP telephone, subscribing the first SIP telephone to a line status of the second SIP telephone, such that the second SIP telephone responsively notifies the first SIP telephone of (i) a current line status of the second SIP telephone and (ii) any changes to the line status of the second SIP telephone;
• transmitting a fifth SIP message to the second SIP telephone, canceling the invitation offered by the first SIP message;
• the first SIP telephone receiving a sixth SIP message, notifying the first SIP telephone of the registration status and the contact information of a third SIP telephone, wherein a user of the second SIP telephone is logged in to both the second SIP telephone and the third SIP telephone;
• responsive to receiving the sixth SIP message, the first SIP telephone transmitting a seventh SIP message to the third SIP telephone, subscribing the first SIP telephone to a line status of the third SIP telephone, such that the third SIP telephone responsively notifies the first SIP telephone of (i) a current line status of the third SIP telephone and (ii) any changes to the line status of the third SIP telephone;
• the first SIP telephone receiving an eighth SIP message from the third SIP telephone, notifying the first SIP telephone that the line status of the third SIP telephone is in a busy state;
• after receiving the eighth SIP message, the first SIP telephone receiving a ninth SIP message from the third SIP telephone, notifying the first SIP telephone that the line status of the third SIP telephone is in an idle state;
• responsive to receiving the sequence of the eighth SIP message followed by the ninth SIP message, the first SIP telephone prompting the user of the first SIP telephone to establish a second communication session with the third SIP telephone;
• after prompting the user, the first SIP telephone receiving an accept-call command from the user of the first SIP telephone to establish the second communication session with the third SIP telephone;
• and
• the first SIP telephone establishing the second communication session with the third SIP telephone in response to receiving the accept-call command.

A method, comprising:

• a first Session Initiation Protocol (SIP) telephone establishing a first communication session with a second SIP telephone;
• the first SIP telephone receiving a camp-on command from the user of the first SIP telephone to camp-on the second SIP telephone;
• responsive to receiving the camp-on command, the first SIP telephone transmitting a first SIP message from the first SIP telephone to the second SIP telephone, subscribing the first SIP telephone to a line status of the second SIP telephone, such that the second SIP telephone responsively notifies the first SIP telephone of (i) a current line status of the second SIP telephone and (ii) any changes to the line status of the second SIP telephone;
• the first SIP telephone receiving a second SIP message from the second SIP telephone, notifying the first SIP telephone that the line status of the second SIP telephone is in a busy state;
• the first SIP telephone terminating the first communication session;
• after receiving the fourth SIP message, the first SIP telephone receiving a third SIP message into the first SIP telephone from the second SIP telephone, notifying the first SIP telephone that the line status of the second SIP telephone is in an idle state;
• responsive to receiving the sequence of the second SIP message followed by the third SIP message, the first SIP telephone prompting the user of the first SIP telephone to establish a second communication session with the second SIP telephone;
• after prompting the user, the first SIP telephone receiving an accept-call command from the user of the first SIP telephone to establish the second communication session with the second SIP telephone;
• and
• the first SIP telephone establishing the second communication session with the second SIP telephone in response to receiving the accept-call command.