Method and apparatus for establishing multicast groups

FIELD OF THE INVENTION

0001The invention relates to the field of communication networks and, more specifically, to establishing multicast groups.

BACKGROUND OF THE INVENTION

0002Internet Protocol (IP) multicast is a bandwidth-conserving technology that delivers IP traffic conveying a single stream of information from a transmitter to multiple receivers which form a multicast group. IP multicast may be used for numerous applications such as videoconferencing, distance learning, software distribution, and the like. IP multicast packets are replicated in the network by multicast routers supporting various multicast protocols for managing multicast group membership, replicating IP multicast packets, and performing like functions associated with IP multicast. Dynamic establishment of multicast groups is currently performed using the Session Announcement Protocol (SAP), including the associated Session Directory Tool (SDR), as defined in RFC2974, which uses a distributed session directory and session announcements to dynamically establish a multicast group.

SUMMARY OF THE INVENTION

0003Various deficiencies in the prior art are addressed through the invention of a method and apparatus for dynamically establishing a multicast group. The method includes receiving, from a first user device, a request to establish a multicast group including a plurality of parameters adapted for establishing the multicast group, obtaining a multicast address for the multicast group, and establishing the multicast group using the assigned multicast address and the parameters. The parameters include at least one multicast group definition parameter and at least one multicast session description parameter. The multicast address and at least a portion of the parameters are adapted for being provided to a second user device to enable the second user device to dynamically join the multicast group.

BRIEF DESCRIPTION OF THE DRAWINGS

0004The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> depicts a high-level block diagram of a communication network;</li><li><figref idref="f0002">FIG. 2</figref> depicts a high-level block diagram of a portion of the communication network of <figref idref="f0001">FIG. 1</figref> including signaling according to one embodiment of the present invention;</li><li><figref idref="f0003">FIG. 3</figref> depicts a high-level block diagram of a portion of the communication network of <figref idref="f0001">FIG. 1</figref> including signaling according to one embodiment of the present invention;</li><li><figref idref="f0004">FIG. 4</figref> depicts a high-level block diagram of a portion of the communication network of <figref idref="f0001">FIG. 1</figref> including signaling according to one embodiment of the present invention; and</li><li><figref idref="f0005">FIG. 5</figref> depicts a high-level block diagram of a general-purpose computer suitable for use in performing at least a portion of the functions described herein.</li></ul>

0005To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.

DETAILED DESCRIPTION OF THE INVENTION

0006The present invention enables dynamic establishment of multicast groups. The present invention enables dynamic establishment of multicast groups by user devices. The present invention enables signaling other than multicast protocol signaling (e.g., Session Initiation Protocol (SIP) signaling, Hypertext Transfer Protocol (HTTP) signaling, and the like, as well as various combinations thereof) to be used for establishing IP multicast groups. As such, the present invention supports robust, dynamic establishment of multicast groups.

0007<figref idref="f0001">FIG. 1</figref> depicts a high-level block diagram of a communication network. Specifically, communication network 100 of <figref idref="f0001">FIG. 1</figref> includes a plurality of user devices (UDs) 102₁ - 102₄ (collectively, UDs 102), a transport network (TN) 110, a SIP server (SS) 120, and a Multicast Manager (MM) 130. The UDs 102₁-102₄ communicate with TN 110 using respective communication paths which may include network elements and communication links for transporting signaling and bearer traffic between UDs 102 and TN 110. The SS 120 and MM 130 communicate with TN 110 using communication paths which may include network elements and communication links for transporting signaling traffic between SS 120 and MM 130, respectively, and TN 110.

0008The UDs 102 include devices operable for participating in multicast sessions. For example, UDs 102 may include wireline phones, wireless phones, computers, and the like, as well as various combinations thereof. The UDs 102 support multicast functions enabling participation in multicast sessions. The UDs may initiate establishment of multicast groups. The UDs 102 may invite other UDs 102 to join a multicast group and UDs 102 may request permission from other UDs 102 to join a multicast group. After joining a multicast group, UDs 102 may operate as sending UDs and/or receiving UDs. The UDs 102 may support various applications requiring multicast capabilities; such as video conferencing applications, instant messaging applications, and the like, as well as various combinations thereof.

0009The TN 110 includes a plurality of routers 112₁-112₄ (collectively, routers 112). The routers 112 may include multicast routers (i.e., routers including multicast functionality, including support for one or more multicast protocols (e.g., Protocol Independent Multicast (PIM), Internet Group Management Protocol (IGMP), and like multicast protocols, as well as various combinations thereof). The multicast functionality may include IP multicast functionality. The routers 112 communicate using a plurality of communication paths (CPs) 114 which may include network elements and communication links adapted for transporting traffic between various combinations of routers 112.

0010The SS 120 is a server supporting SIP signaling. The SS 120 may route SIP messages between UDs 102. For example, SS 120 may route SIP INVITE messages between UDs 102 and between UDs 102 and routers 112, thereby enabling UDs 102 to invite other UDs 102 to join a multicast group and enabling UDs 102 to request to join a multicast group <nplcit id="ncit0001" npl-type="b"><text>WITTMANN R AND ZITTERBART M: "Multicast Communication: Protocols and Applications" MORGAN KAUFMANN PUBLISHERS, SAN FRANCISCO, 12 May 2000</text></nplcit> describes such a server. The SS 120 may route messages between UDs 102 and MM 130. The MM 130 is a system adapted for managing multicast functions. The MM 130 may perform at least a portion of the functions described herein, including establishing a multicast group according to a request to establish a multicast group received from one of UDs 102.

0011Although primarily depicted and described with respect to specific numbers and configurations of UDs 102, routers 112, SSs 120, and MMs 130, the present invention may be implemented using various other numbers and configurations of UDs 102, routers 112, SSs 120, and MMs 130, and, in some embodiments, other network elements adapted to perform various functions depicted and described herein. The operation of UDs 102, routers 112, SS 120, and MM 130 in support of multicast establishment and communication functions of the present invention may be better understood with respect to <figref idref="f0002 f0003 f0004 f0005">FIG. 2 - FIG. 5</figref>.

0012<figref idref="f0002">FIG. 2</figref> depicts a high-level block diagram of a portion of the communication network of <figref idref="f0001">FIG. 1</figref> including signaling according to one embodiment of the present invention. The communication network portion 200 of <figref idref="f0002">FIG. 2</figref> includes UDs 102₁, 102₂, and 102₄. The communication network portion 200 of <figref idref="f0002">FIG. 2</figref> further includes MM 130. For purposes of clarity in describing functions of the present invention, routers 112 and SS 120 are omitted (although, as depicted and described herein with respect to <figref idref="f0003">FIG. 3</figref> and <figref idref="f0004">FIG. 4</figref>, routers 112 and SS 120 may support various functions of the present invention). The signaling depicted and described herein with respect to <figref idref="f0002">FIG. 2</figref> is performed in order to establish a multicast group including UDs 102₁, 102₂, and 102₄, and in order to support the associated multicast stream of the established multicast group.

0013At step 202, UD 102₁ creates a request to establish a multicast group and forwards the request to establish the multicast group to MM 130. The UD 102₁ forwards the request to establish the multicast group to MM 130. The UD 102₁ may forward the request to establish the multicast group to MM 130 using one or more of a plurality of protocols and associated message formats. In one embodiment, UD 102₁ forwards the request to establish the multicast group to MM 130, and other message and information may be exchanged, using SIP signaling. Use of SIP signaling for the present invention is depicted and described herein in more detail with respect to <figref idref="f0003">FIG. 3</figref>, <figref idref="f0004">FIG. 4</figref>, and <figref idref="f0005">FIG. 5</figref>.

0014The request to establish the multicast group includes one or more parameters. The one or more parameters included in the request to establish the multicast group include one or more parameters adapted to establish the multicast group. The one or more parameters included in the request to establish the multicast group include one or more parameters adapted to define the multicast group being established (denoted as multicast group definition parameters). The one or more parameters included in the request to establish the multicast group include one or more parameters adapted to describe the multicast session for the multicast group being established (denoted as multicast session description parameters). The one or more parameters included in the request to establish the multicast group may include various other parameters.

0015The multicast group definition parameters may include a time at which the multicast group is scheduled to be established, a list of network elements authorized to initiate an invitation to join the multicast group, a list of user devices authorized to join the multicast group, and the like, as well as various combinations thereof. In one embodiment, in which the multicast group definition parameters include a list of user devices authorized to join the multicast group, the multicast group definition parameters may further include one or more privileges associated with the user devices authorized to join the multicast group.

0016The time at which the multicast group is scheduled to be established may specify that the multicast group be established immediately or at a future date/time. The list of network elements authorized to initiate an invitation to join the multicast group may include one or more user devices (e.g., only UD 102₁ is authorized to invite other UDs 102 to join the multicast group), one or more management systems (e.g., MM 130), and the like, as well as various combinations thereof. The list of user devices authorized to join the multicast group may include any user devices (and, in some embodiments, may alternatively be provided as a list of users authorized to join the multicast group).

0017In one embodiment, the list of user devices authorized to join the multicast group may include, for each user device in the list, at least one parameter (attribute) adapted for indicating whether the user device should be automatically invited to join the multicast group in response to establishment of the multicast group. The parameter may be denoted as an invite parameter. In one embodiment, the invite parameter associated with a user device may indicate that the management system which established the multicast group (illustratively, MM 130) should automatically invite the user device to join the multicast group in response to establishment of the multicast group.

0018In one embodiment, the list of user devices authorized to join the multicast group may include, for each user device in the list, at least one privilege parameter (attribute) defining participation by the user device in the multicast session. In one embodiment, a privilege parameter associated with each user device authorized to join a multicast group may include an indication as to whether the user device may transmit multicast traffic to other members of the multicast group (i.e., operate only as a receiving UD or as both a receiving and sending UD). Although described with respect to one specific privilege parameter, various other privilege parameters associated with individual UDs or groups of UDs may be specified in the request to establish the multicast group.

0019In one embodiment, the request to establish the multicast group may specify that specific devices are authorized to invite specific sets of user devices (i.e., user devices authorized to join the multicast group) to join the multicast group. For example, the request to establish the multicast group may specify that UD 102₁ is authorized to invite UD 102₂ (and other user devices (not depicted)) to join the multicast group and MM 130 is authorized to invite UD 102₄ (and other user devices (not depicted)) to join the multicast group.

0020The multicast session description parameters may include any parameter adapted for defining the multicast session by which multicast traffic is multicasted to members of the multicast group. In one embodiment, for example, multicast session description parameters include at least one of an IP address (i.e., multicast address to be used by members of the multicast group), one or more ports (i.e., multicast ports to be used by members of the multicast group), one or more coder-decoders (codecs) (i.e., codecs to be used by members of the multicast group), and the like, as well as various combinations thereof. Although described with respect to specific multicast session description parameters, various other multicast session description parameters may be specified in the request to establish the multicast group.

0021In response to the request to establish the multicast group, MM 130 obtains a multicast address for the multicast group. The MM 130 may obtain the multicast address locally (e.g., from a list or range of available multicast addresses). The MM 130 assigns the multicast address to the multicast group. The MM 130 stores a mapping between the multicast group and the assigned multicast address. In one embodiment, MM 130 stores at least a portion of the parameters included in the request to establish the multicast group. The MM 130 stores the parameters included in the request to establish the multicast group in a manner for associating the stored parameters with the multicast group. In one embodiment, MM 130 stores at least a portion of the multicast group definition parameters included the request to establish the multicast group. In one embodiment, MM 130 stores at least a portion of the multicast session description parameters included in the request to establish the multicast group.

0022At step 204, MM 130 sends a multicast group response message to UD 102₁. The multicast group response message includes the multicast address assigned to the multicast group. The multicast group response message may include at least a portion of the parameters included in the request to establish the multicast group (e.g., for verification of the parameters used by MM 130 to establish the multicast group). In one such embodiment, the multicast group response message may include the multicast session description parameters accepted during establishment of the multicast group. The multicast group response message may include a multicast group identifier. At step 206, UD 102₁ begins transmitting multicast traffic to the multicast group using the assigned multicast address. The UD 102₁ begins transmitting multicast traffic using a multicast session in accordance with the multicast session description parameters.

0023At step 207, MM 130 initiates an invite to UD 102₄ to join the multicast group established by MM 130. In one embodiment, the invite to UD 102₄ to join the established multicast group may be initiated by MM 130 automatically in response to establishment of the multicast group. As described herein, in one embodiment, the request to establish the multicast group may include one or more parameters (denoted as an invite parameter(s)) adapted for identifying user device(s) 104 that should be automatically invited to join the multicast group in response to establishment of the multicast group.

0024At step 208, other user devices begin joining the multicast group dynamically requested by UD 102₁ and dynamically established by MM 130. There are several ways in which user devices may join the multicast group. A user device may be invited to join the multicast group (e.g., by a user device that dynamically requested establishment of the multicast group (illustratively, UD 102₁), by a management system associated with establishment of the multicast group (illustratively, MM 130), and the like, as well as various combinations thereof). A user device may request to join the multicast group (e.g., sending a request to a user device which dynamically requested establishment of the multicast group (illustratively, UD 102₁), sending a request to a management system associated with establishment of the multicast group (illustratively, MM 130), and the like, as well as various combinations thereof).

0025At step 208_A1, UD 102₁ sends an invitation to UD 102₂ inviting UD 102₂ to join the multicast group. In one embodiment, the invitation from UD 102₁ to UD 102₂ inviting UD 102₂ to join the multicast group may include the multicast address of the multicast group, as well as one or more multicast session description parameters required by UD 102₂ in order to participate in the multicast group. At step 208_B1, in response to the invitation to join the multicast group, UD 102₂ accepts the invitation from UD 102₁ to join the multicast group. The UD 102₂ may then begin receiving multicast traffic over the multicast address of the multicast group. Although omitted for purposes of clarity, in one embodiment, UD 102₂ (or other UDs 102) may initiate a request to UD 102₁ to be joined to the multicast group.

0026At step 208_A2, UD 102₄ initiates a request to MM 130 requesting to join the multicast group. At step 208_B2, in response to the request to join the multicast group, MM 130 accepts the request from UD 102₄ to join the multicast group. In one embodiment, the acceptance by MM 130 of the request by UD 102₄ to join the multicast group may include the multicast address of the multicast group, as well as one or more multicast session description parameters required by UD 102₄ in order to participate in the multicast group. The UD 102₄ may then begin receiving multicast traffic over the multicast address of the multicast group. Although omitted for purposes of clarity, in one embodiment, MM 130 may initiate a request to UD 102₄ (or other UDs 102) inviting UD 102₄ to join the multicast group.

0027Although described with respect to specific methods by which user devices join a multicast group, user devices may join a multicast group using various other methods. In one example, although omitted for purposes of clarity, a user device may join a multicast group through a router using standard multicast join capabilities. In another example, a user device may be joined to a multicast group by a management system (illustratively, MM 130) through communication between the manager and the router. These and other methods by which user devices may join an established multicast group may be better understood with respect to <figref idref="f0003">FIG. 3</figref> and <figref idref="f0004">FIG. 4</figref> depicted and described herein.

0028Upon joining the multicast group, at step 210, UD 102₂ begins receiving multicast traffic from UD 102₁ over the multicast address of the multicast group. Upon joining the multicast group, at step 212, UD 102₂ begins transmitting multicast traffic to UD 102₁ and 102₄ over the multicast group. Upon joining the multicast group, at step 210, UD 102₄ begins receiving multicast traffic from UD 102₁ over the multicast address of the multicast group. Upon joining the multicast group, at step 212, UD 102₄ begins receiving multicast traffic from UD 102₂ over the multicast address of the multicast group. Although omitted for purposes of clarity, UDs 102₂ and 102₄ may leave the multicast group using any means of leaving the multicast group.

0029<figref idref="f0003">FIG. 3</figref> depicts a high-level block diagram of a portion of the communication network of <figref idref="f0001">FIG. 1</figref> including signaling according to one embodiment of the present invention. The communication network portion 200 of <figref idref="f0002">FIG. 2</figref> includes UDs 102_1, 102₂, and 102₄, and routers 112₁, 112₂, and 112₄. The communication network portion 300 of <figref idref="f0003">FIG. 3</figref> further includes SS 120 and MM 130. The signaling depicted and described herein with respect to <figref idref="f0003">FIG. 3</figref> is performed in order to establish a multicast group including UDs 102₁, 102₂, and 102₄, and in order to support the associated multicast stream of the established multicast group.

0030At step 302, UD 102₁ initiates a request to establish a multicast group. The request to establish the multicast group is similar to the request to establish the multicast group described with respect to <figref idref="f0002">FIG. 2</figref> (i.e., the request to establish the multicast group may include various parameters adapted to establish the multicast group, including multicast group definition parameters, multicast session description parameters, and like parameters, as well as various combinations thereof).

0031As described herein, in one embodiment, the request to establish the multicast group may include a time at which the multicast group is scheduled to be established. If the multicast group is scheduled to be established immediately, MM 130 immediately establishes the multicast group (e.g., by assigning a multicast address to the multicast group and storing at least a portion of the parameters included in the request to establish the multicast group). If the multicast group is scheduled to be established at a later time, MM 130 stores the information received with the request to establish the multicast group for use in establishing the multicast group at the scheduled time. For purposes of clarity in describing the invention, assume that the request to establish the multicast group initiated by UD 102₁ indicates that the multicast group is scheduled to be established immediately.

0032The UD 102₁ forwards the request to establish the multicast group to SS 120. The SS 120 forwards the request to establish the multicast group to MM 130. In one embodiment, the request to establish the multicast group is conveyed using a SIP INVITE message. In one embodiment, at least a portion of the parameters included in the request to establish the multicast group may be conveyed using one or more existing SIP fields, including SIP header fields and SIP body fields. In one embodiment, for example, at least a portion of the multicast session description parameters may be conveyed using the SIP session description field. In one embodiment, at least a portion of the parameters included in the request to establish the multicast group may be conveyed using new SIP fields, including new SIP header fields and new SIP body fields. In one embodiment, MM 130 may be implemented as a SIP application server.

0033The MM 130 establishes the multicast group in response to the request to establish the multicast group. The MM 130 establishes the multicast group in a manner similar to establishment of the multicast group as described herein with respect to <figref idref="f0002">FIG. 2</figref>. The MM 130 assigns the multicast address to the multicast group. The MM 130 stores at least a portion of the parameters (e.g., multicast group definition parameters and multicast session description parameters) included in the request to establish the multicast group. The MM 130 stores the multicast address and the parameters included in the request to establish the multicast group in a manner for associating the multicast address and the parameters with the multicast group.

0034At step 304, MM 130 initiates a response to the request to establish the multicast group. The MM 130 forwards the response to SS 120. The SS 120 forwards the response to UD 102₁. The response includes the multicast address assigned for the multicast group. The response includes the multicast session description parameters associated with the multicast session for the multicast group. In one embodiment, the multicast session description parameters returned in the response are identical to the multicast session description parameters included in the request to establish the multicast group. The response to the request to establish the multicast group may be conveyed using a SIP OK message.

0035In one embodiment, in which at least a portion of the multicast session description parameters included in the request to establish the multicast session are not accepted by MM 130, the response may include multicast session description parameters accepted by MM 130 (a portion of which may be different than the requested multicast session description parameters). This response may be conveyed using a SIP OK message. In one embodiment, in which at least a portion of the multicast session description parameters included in the request to establish the multicast session are not accepted by MM 130, the response may be a negative response (e.g., a SIP 486 BUSY message).

0036At step 306, UD 102₁ begins transmitting multicast traffic to the multicast group. The UD 102₁ begins transmitting multicast traffic using the assigned multicast address. The UD 102₁ begins transmitting multicast traffic using a multicast session in accordance with the accepted multicast session description parameters (returned from MM 130 to UD 102₁ in the response to the request to establish the multicast group). As depicted in <figref idref="f0003">FIG. 3</figref>, UD 102₁ transmits multicast traffic to router 112₁, from which the multicast traffic may be transmitted to other UDs 102 which join the multicast group, as well as to other routers 112 supporting UDs 102 which join the multicast group. Although depicted as beginning prior to other UDs 102 joining the multicast group, in other embodiments, transmission of multicast traffic by UD 102₁ to the multicast group may occur before, contemporaneous with, or after one or more other UDs 102 begin joining the multicast group.

0037At step 308, other user devices begin joining the multicast group dynamically requested by UD 102₁ and dynamically established by MM 130. There are several ways in which user devices may join the multicast group. A user device may be invited to join the multicast group (e.g., by a user device which dynamically requested establishment of the multicast group (illustratively, UD 102₁), by a management system associated with establishment of the multicast group (illustratively, MM 130), and the like, as well as various combinations thereof). There are several ways in which a user device may respond to an invitation to join the multicast group.

0038In one embodiment, a user device may respond to an invitation to join the multicast group using standard multicast join mechanisms of existing multicast protocols (e.g., sending a join message to a router associated with the user device, such as an Internet Group Management Protocol (IGMP) join message, a Multicast Listener Discover (MLD) message, and the like). Although omitted for purposes of clarity, MM 130 is expected to be aware of such joins to (as well as leaves from) the multicast group through routers 112. The MM 130 may be made aware of such joins/leaves using periodic polling from MM 130 to routers 112, explicit signaling from routers 112 to MM 130, and the like, as well as various combinations thereof.

0039In one embodiment, in which the invitation to join the multicast group is sent using a SIP request message (e.g., SIP INVITE message), a user device may respond to an invitation to join the multicast group with a SIP response message (e.g., SIP OK). In this embodiment, the device which receives the SIP OK message may notify the appropriate router(s) that the user device is joining the multicast group. For example, if the SIP INVITE message originated from one of the UDs 102, that UD 102 may receive the SIP OK message and, in response to the SIP OK message, directly or indirectly (e.g., via SS 120 and/or MM 130) inform the appropriate router that the UD 102 is joining the multicast group. For example, if the SIP INVITE message originated from MM 130, MM 130 may receive the SIP OK message and, in response to the SIP OK message, inform the appropriate router that the UD 102 is joining the multicast group.

0040At step 308_A1. UD 102₁ sends a SIP INVITE message to UD 102₂ inviting UD 102₂ to join the multicast group. The UD 102₁ sends the SIP INVITE message to SS 120 which forwards the SIP INVITE message to UD 102₂. In one embodiment, the invitation from UD 102₁ to UD 102₂ inviting UD 102₂ to join the multicast group may include the multicast address of the multicast group, as well as one or more multicast session description parameters required by UD 102₂ in order to participate in the multicast group. At step 308₃₁, in response to the SIP INVITE message inviting UD 102₂ to join the multicast group, UD 102₂ accepts the invitation from UD 102₁ to join the multicast group by initiating a standard multicast join to router 112₂ (e.g., using IGMP, MLD, and like protocols).

0041At step 308_A2, MM 130 sends a SIP INVITE message to UD 102₄ inviting UD 102₂₄ to join the multicast group. The MM 130 sends the SIP INVITE message to SS 120 which forwards the SIP INVITE message to UD 102₄. In one embodiment, the invitation from MM 130 to UD 102₄ inviting UD 102₄ to join the multicast group may include the multicast address of the multicast group, as well as one or more multicast session description parameters required by UD 102₄ in order to participate in the multicast group. At step 308_B2, in response to the SIP INVITE message inviting UD 102₄ to join the multicast group, UD 102₄ accepts the invitation from MM 130 to join the multicast group by initiating a SIP OK message in response to the SIP INVITE message. The UD 102₄ sends the SIP OK message to SS 120. The SS 120 forwards the SIP OK message to MM 130. In response to the SIP OK message, MM 130 notifies router 112₄ that UD 102₄ is joining the multicast group.

0042At step 310, upon joining the multicast group, UDs 102₂ and 102₄ begin receiving multicast traffic from UD 102₁ over the multicast address of the multicast group. The UD 102₂ receives multicast traffic from UD 102₁ via routers 112₁ and 112₂: The UD 102₄ receives multicast traffic from UD 102₁ via routers 112₁, 112₂, and 112₄. At step 312, upon joining the multicast group, UD 102₂ begins transmitting multicast traffic to UDs 102₁ and 102₄ over the multicast group. The UD 102₁ receives multicast traffic from UD 102₂ via routers 112₁ and 112₂. The UD 102₄ receives multicast traffic from UD 102₂ via routers 112₂ and 112₄. Although omitted for purposes of clarity, UDs 102₂ and 102₄ may leave the multicast group using any means of leaving the multicast group, such as using standard multicast leaves (e.g., IGMP/MLD leaves), initiating SIP BYE messages to the device(s) which invited the UD 102 to join the multicast group (e.g., UD 102₁ or MM 130), and the like.

0043Although omitted for purposes of clarity, rather than being invited to join the multicast group, a user device may request to join the multicast group (e.g., sending a request to a user device which dynamically requested establishment of the multicast group (illustratively, UD 102₁), sending a request to a management system associated with establishment of the multicast group (illustratively, MM 130), and the like, as well as various combinations thereof). In one embodiment, a request by a user device to join the multicast group may be conveyed using one or more SIP messages (e.g., SIP INVITE messages). In one embodiment, MM 130 may periodically forward a current list of multicast group members to various combinations of non-member user devices which may be used by the non-member user devices as a basis for determining whether to request to join the multicast group (e.g., using SIP INVITE messages, SIP re-INVITE messages, and the like, as well as various combinations thereof).

0044In one embodiment, in which a user device initiates a request to join the multicast group to a user device which dynamically requested establishment of the multicast group, the user device to which the request is initiated may respond directly to the user device which initiates the request or, alternatively, may forward the request to the management system associated with establishment of the multicast group. If the user device to which the request is initiated responds directly, the direct response may include the multicast address and associated multicast session description parameters of the multicast session. The direct response may be conveyed using one or more SIP messages (e.g., SIP INVITE, SIP OK, and the like, as well as various combinations thereof).

0045If the request is forwarded to the management system associated with establishment of the multicast group, the management system (illustratively, MM 130) may respond to the request directly, or, alternatively, may instruct one or more routers associated with the joining user device that the user device is joining the multicast group. If the MM 130 responds to the request directly, the direct response may include the multicast address and associated multicast session description parameters of the multicast session. The direct response may be conveyed using one or more SIP messages (e.g., SIP INVITE, SIP OK, and the like, as well as various combinations thereof). The MM 130 may alternatively instruct one or more routers associated with the joining user device that the user device is joining the multicast group (which may be performed in a manner as described with respect to steps 308_B2).

0046<figref idref="f0004">FIG. 4</figref> depicts a high-level block diagram of a portion of the communication network of <figref idref="f0001">FIG. 1</figref> including signaling according to one embodiment of the present invention. The communication network portion 400 of <figref idref="f0004">FIG. 4</figref> includes UDs 102₁, 102₂, and 102₄, and associated routers 112₁, 112₂, and 112₄. The communication network portion 400 of <figref idref="f0004">FIG. 4</figref> further includes SS 120 and MM 130. The signaling depicted and described herein with respect to <figref idref="f0004">FIG. 4</figref> is performed in order to establish a multicast group including UDs 102₁, 102₂, and 102₄, and in order to support the associated multicast stream of the established multicast group.

0047At step 402, MM 130 registers with SS 120 using a SIP REGISTER message. The MM 130 registers using a pre-defined multicast signaling address known by a number of UDs 102 (e.g., each of UDs 102 depicted with respect to <figref idref="f0001">FIG. 1</figref>). The MM 130 may manage one or more multicast signaling groups and each multicast signaling group may include one or more multicast signaling addresses. A multicast signaling group including multiple multicast signaling addresses enables further grouping of UDs 102 included within the multicast signaling group, thereby enabling reductions in the number of signaling messages received by specific UDs 102.

0048For example, UDs 102, - 102₄ may belong to a multicast signaling group and, within the multicast signaling group, UDs 102₁ and 102₂ and UDs 102₃ and 102₄ may use different multicast signaling addresses. In this example, signaling may be directed to both UDs 102₁ and 102₂ without being directed to UDs 102₃ and 102₄ and, similarly, signaling may be directed to UDs 102₃ and 102₄ without being directed to UDs 102₁ and 102₂. In one embodiment, multicast signaling addresses may be hierarchically structured, thereby enabling MM 130 to determine multicast signaling of leaf addresses using the associated root address.

0049At step 404, a SIP OK message is multicasted to UDs 102 that have joined the multicast signaling group (potentially all user devices in the network). For purposes of clarity, an assumption is made that UDs 102₁,102₂, and 102₄ have joined the multicast signaling group (and UD 102₃ has not joined the multicast signaling group). In accordance with this assumption, SS 120 multicasts the SIP OK message to UDs 102₁ (via router 112₁), 102₂ (via routers 112₁ and 112₂), and 102₄ (via routers 112₁, 112₂, and 112₄). The signaling associated with steps 402 and 404 may be performed at any time prior to requests to establish multicast groups.

0050At step 406, UD 102₁ creates a request to establish a multicast group and forwards the request to establish the multicast group to MM 130. The UD 102₁ conveys the request to establish the multicast group as a SIP INVITE message, transmitting the SIP INVITE message to SS 120, which forwards the SIP INVITE message to MM 130. In one embodiment, the request to establish the multicast group is substantially similar to the request to establish the multicast group depicted and described herein with respect to steps 202 and 302 of <figref idref="f0002">FIG. 2</figref> and <figref idref="f0003">FIG. 3</figref>, respectively. In order to support establishment of multicast groups in which the multicast group is scheduled to be established at a future time, MM 130 may operate as a SIP application server (i.e., caching the request to establish the multicast group until the scheduled multicast group establishment time).

0051At step 408, the SIP INVITE message (i.e., the request to establish the multicast group) is multicasted by SS 120 to all devices that listen to SIP signaling on the multicast signaling address specified by MM 130 (i.e., to all devices which have joined the multicast signaling group). The SS 120 multicasts the SIP INVITE message to UDs 102_1, 102₂, and 102₄ which have joined the multicast signaling group and MM 130 which formed the multicast signaling group. The SS 120 multicasts the SIP INVITE message to UDs 102₁ (via router 112₁), 102₂ (via routers 112₁ and 112₂), and 102₄ (via routers 112₁, 112₂, and 112₄), and MM 130 (via router 112₁).

0052As described herein, in one embodiment, the request to establish the multicast group may include a time at which the multicast group is scheduled to be established. If the multicast group is scheduled to be established immediately, MM 130 immediately establishes the multicast group (e.g., by assigning a multicast address to the multicast group and storing at least a portion of the parameters included in the request to establish the multicast group). If the multicast group is scheduled to be established at a later time, MM 130 stores the information received with the request to establish the multicast group for use in establishing the multicast group at the scheduled time. For purposes of clarity in describing the invention, assume that the request to establish the multicast group initiated by UD 102₁ indicates that the multicast group is scheduled to be established immediately.

0053The MM 130 establishes the multicast group in response to the request to establish the multicast group. The MM 130 establishes the multicast group in a manner similar to establishment of the multicast group as described herein with respect to <figref idref="f0002">FIG. 2</figref> and <figref idref="f0003">FIG. 3</figref>. The MM 130 assigns the multicast address to the multicast group. The MM 130 stores at least a portion of the parameters (e.g., multicast group definition parameters and multicast session description parameters) included in the request to establish the multicast group. The MM 130 stores the multicast address and the parameters included in the request to establish the multicast group in a manner for associating the multicast address and the parameters with the multicast group.

0054At step 410, MM 130 initiates a SIP OK message in response to the request to establish the multicast group. The MM 130 forwards the SIP OK message to SS 120 which forwards the SIP OK message to UD 102₁. The SIP OK response message from MM 130 to UD 102₁ is not multicast by SS 120 using the multicast signaling group used to multicast the SIP INVITE message (i.e., the request to establish the multicast group). The response includes the multicast session description parameters associated with the multicast session for the multicast group, including the multicast address assigned to the multicast group. In one embodiment, the multicast session description parameters returned in the SIP OK message are identical to the multicast session description parameters included in the SIP INVITE message. In one embodiment, in which at least a portion of the multicast session description parameters included in the request to establish the multicast session are not accepted by MM 130, the response may include multicast session description parameters accepted by MM 130.

0055At step 412, UD 102₁ begins transmitting multicast traffic to the multicast group. The UD 102₁ begins transmitting multicast traffic using the assigned multicast address. The UD 102₁ begins transmitting multicast traffic using a multicast session in accordance with the accepted multicast session description parameters (returned from MM 130 to UD 102₁ in the response to the request to establish the multicast group). As depicted in <figref idref="f0004">FIG. 4</figref>, UD 102₁ transmits multicast traffic to router 112₁, from which the multicast traffic may be transmitted to other UDs 102 which join the multicast group, as well as to other routers 112 supporting UDs 102 which join the multicast group. Although depicted as beginning prior to other UDs 102 joining the multicast group, in other embodiments, transmission of multicast traffic by UD 102₁ to the multicast group may occur before, contemporaneous with, or after one or more other UDs 102 begin joining the multicast group.

0056At step 414, UD 102₂ responds to the SIP INVITE message (i.e., the request to establish the multicast group) with a SIP OK message. The UD 102₂ transmits the SIP OK message to SS 120, which forwards the SIP OK message to UD 102₁. Since the SIP INVITE message multicast by SS 120 includes the multicast session description parameters, UD 102₂ receives the multicast session description parameters required to participate in the multicast session as part of the SIP INVITE message multicast by SS 120. The UD 102₂, however, does not yet have the multicast address required to join the multicast group and participate in the multicast session.

0057At step 416, UD 102₁ responds to the SIP OK message with a SIP ACK message. The UD 102₁ transmits the SIP ACK message to SS 120, which forwards the SIP ACK message to UD 102₂. The SIP ACK message from UD 102₁ includes the multicast address assigned by MM 130 and provided by MM 130 to UD 102₁ (in the SIP OK message of step 410). Although omitted for purposes of clarity, after receiving the multicast address from UD 102₁, UD 102₂ may join the multicast group in one of several ways. In one embodiment, UD 102₂ may join the multicast group using one of the several methods depicted and described herein with respect to <figref idref="f0003">FIG. 3</figref>. At step 418, upon joining the multicast group, UD 102₂ begins receiving multicast traffic from UD 102₁ over the multicast address of the multicast group. The UD 102₂ receives multicast traffic from UD 102₁ via routers 112₁ and 112₂.

0058At step 420, at some later time (e.g., later than the time at which UD 1022 responds to the SIP INVITE message), UD 102₄ responds to the SIP INVITE message (i.e., the request to establish the multicast group) with a SIP OK message. The UD 102₄ transmits the SIP OK message to SS 120, which forwards the SIP OK message to UD 102₁. Since the SIP INVITE message multicast by SS 120 includes the multicast session description parameters, UD 102₄ receives the multicast session description parameters required to participate in the multicast session as part of the SIP INVITE message multicast by SS 120. The UD 102₄, however, does not yet have the multicast address required to join the multicast group and participate in the multicast session.

0059At step 422, UD 102₁ responds to the SIP OK message with a SIP ACK message. The UD 102₁ transmits the SIP ACK message to SS 120, which forwards the SIP ACK message to UD 102₄. The SIP ACK message from UD 102₁ includes the multicast address assigned by MM 130 and provided by MM 130 to UD 102₁ (in the SIP OK message of step 410). Although omitted for purposes of clarity, after receiving the multicast address from UD 102₁, UD 102₄ may join the multicast group in one of several ways. In one embodiment, UD 102₄ may join the multicast group using one of the several methods depicted and described herein with respect to <figref idref="f0003">FIG. 3</figref>. At step 424, upon joining the multicast group, UD 102₄ begins receiving multicast traffic from UD 102₁ over the multicast address of the multicast group. The UD 102₄ receives multicast traffic from UD 102₁ via routers 112₁, 112₂, and 112₄.

0060Although omitted for purposes of clarity, UDs 102₂ and 102₄ may leave the multicast group using any means of leaving the multicast group, such as using standard multicast leaves (e.g., IGMP/MLD leaves), initiating SIP BYE messages UD 102₁. The MM 130 will not receive such SIP BYE messages from UDs 102₂ and 102₄ unless MM 130 is in the signaling path (e.g., unless MM 130 is implemented as a SIP application server). Although omitted for purposes of clarity, the multicast session may be closed by UD 102₁ (e.g., by sending a SIP BYE message to all UDs 102 which joined the multicast signaling group established by MM 130). The SIP BYE message is multicasted to all UDs 102 which joined the multicast signaling group using the multicast signaling group.

0061In one embodiment, in which MM 130 is a SIP application server, the SIP OK message initiated by UD 102₁ (in step 404) and multicast to UDs 102 that have joined the multicast signaling group may be suppressed. In this embodiment, the SIP OK message would be received by MM 130, however, MM 130 would be able to suppress the multicasting of the SIP OK message to UDs 102₁, 102₂, and 102₄.

0062In one embodiment, in which MM 130 is a SIP application server, the SIP INVITE message (i.e., the request to establish the multicast group multicast by SS 120 to all devices that listen to SIP signaling on the multicast signaling address) may be modified, before the SIP INVITE message is multicasted by SS 120 to all devices that listen to SIP signaling on the multicast signaling address, by MM 130 to include the multicast address assigned by MM 130.

0063In one embodiment, in which MM 130 is a SIP application server, since MM 130 receives all SIP signaling, MM 130 could set up the multicast paths in the routers in response to SIP OK message received from UDs 102 attempting to join the multicast group, thereby obviating the need for specific multicast joins by each of the UDs 102 (as well as obviating the need for each UD 102 to support an associated multicast stack).

0064Although omitted from <figref idref="f0002 f0003 f0004">FIGS. 2 - 4</figref> for purposes of clarity, in one embodiment, the multicast session may be periodically re-announced (e.g., using a SIP RE-INVITE message which may be multicast to various combinations of UDs 102 using one or more multicast signaling groups established as described herein). Although omitted for purposes of clarity, in one embodiment, after the multicast session is established, the multicast session may be altered. The multicast session may be altered by a UD 102 which requested establishment of the multicast group (illustratively, UD 102₁) or by one or more other UDs 102 which join the multicast group and participate in the multicast session (illustratively, UDs 102₂ and 102₄).

0065The multicast session may be altered such that one or more of the parameters specified in the request to establish the multicast group (or one or more parameters altered in a previous request to alter the multicast session) may be altered. In one embodiment, at least a portion of the multicast group definition parameters may be altered (e.g., to change the list of UDs authorized to join the multicast group, to change permissions associated with one or more UDs authorized to join the multicast group, and the like, as well as various combinations thereof). In one embodiment, at least a portion of the multicast session description parameters may be altered (e.g., to change the ports used in the multicast session, to change the codec used in the multicast session, and the like, as well as various combinations thereof).

0066In one embodiment, the multicast session may be altered by initiating a SIP RE-INVITE message to MM 130. In one embodiment, the SIP RE-INVITE message may be multicast within the multicast group (i.e., so that only UDs 102 participating in the multicast session receive the SIP RE-INVITE message). For example, the SIP RE-INVITE message may be multicast to UDs 102₂ and 102₄. In one embodiment, the SIP RE-INVITE message may be multicast using a multicast signaling group (i.e., so that UDs 102 other than UDs 102 participating in the multicast session receive the SIP RE-INVITE message). For example, the SIP RE-INVITE message may be multicast to UDs 102₁, 102₂, 102₃, and 102₄.

0067Although primarily depicted and described herein with respect to user devices, in some embodiments, since end users may access communication networks from multiple user devices associated with one or more network access points, references herein to user device may alternatively refer to a specific user irrespective of the user device by which that user accesses communication networks. In such embodiments, user device may refer to the end user associated with the user device. For example, although primarily described herein with respect to privilege parameters associated with each user device authorized to join a multicast group, privilege parameters may in fact be associated with the respective users associated with the user devices.

0068Although primarily depicted and described herein with respect to an embodiment in which Any Source Multicast (ASM) is used, the present invention may be implemented in embodiments in which Source Specific Multicast (SSM) is used. For example, although primarily depicted and described herein with respect to multicast streams originating from multiple UDs 102, in one embodiment, only one of the UDs 102 may have permission to transmit to other members of the multicast group. Although primarily depicted and described herein with respect to embodiments in which SIP signaling is used to establish and manage multicast groups, in other embodiments, various other protocols may be used to establish and maintain multicast groups. In one such embodiment, for example, HTTP may be used to establish and maintain multicast groups.

0069<figref idref="f0005">FIG. 5</figref> depicts a high-level block diagram of a general-purpose computer suitable for use in performing the functions described herein. As depicted in <figref idref="f0005">FIG. 5</figref>, system 500 includes a processor element 502 (e.g., a CPU), a memory 504, e.g., random access memory (RAM) and/or read only memory (ROM), a multicast group establishment/management module 505, and various input/output devices 506 (e.g., storage devices, including but not limited to, a tape drive, a floppy drive, a hard disk drive or a compact disk drive, a receiver, a transmitter, a speaker, a display, an output port, and a user input device (such as a keyboard, a keypad, a mouse, and the like)).

0070It should be noted that the present invention may be implemented in software and/or in a combination of software and hardware, e.g., using application specific integrated circuits (ASIC), a general purpose computer or any other hardware equivalents. In one embodiment, the present multicast group establishment/management module or process 505 can be loaded into memory 504 and executed by processor 502 to implement the functions as discussed above. As such, multicast group establishment/management process 505 (including associated data structures) of the present invention can be stored on a computer readable medium or carrier, e.g., RAM memory, magnetic or optical drive or diskette and the like.