Abstract:
Methods, systems, and computer readable media system for collecting and distributing session initiation protocol (SIP) event watcher entity subscription information in a communications network are disclosed. According to one aspect, a system includes one or more notifier servers for receiving subscription requests for SIP event information associated with a plurality of watched entities from a plurality of watcher entities. The system further includes a watcher information (WINFO) server for receiving, from the notifier servers, SIP event subscription information that includes, for each watcher entity, an association between the watcher entity to each of the watched entities in which a subscription for SIP event information was requested by the watcher entity, for storing the SIP event subscription information in the WINFO server, for receiving, from one of the watched entities, a request for watcher entity subscription information associated with the requesting watched entity from one of the watched entities, and for accessing the SIP event subscription information to locate the watcher entity subscription information associated with the requesting watched entity.

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/292,843, filed Jan. 6, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The subject matter described herein relates to session initiation protocol (SIP) event subscription and notification. More particularly, the subject matter described herein relates to systems, methods, and computer readable media for providing SIP event watcher entity information in a communications network. 
     BACKGROUND 
     A session initiation protocol (SIP) event notification system as disclosed in Request for Comments (RFC) 3265 includes a network architecture that permits SIP nodes to request notifications from remote nodes which indicate whether certain events (e.g., change in state information) have occurred in a given end node. Namely, SIP entities may subscribe to the state of a resource associated with a remote node (e.g., a watched subscriber or resource entity), and a notifier node/server associated with the remote node can send a notification if a state change occurs. For example, a SIP entity may send a SIP SUBSCRIBE message to request a SIP event subscription (e.g., a presence state subscription) to a notifier node that services the end node. A notifier node associated with the end node may then be configured to return the current state information (e.g., presence state information) of the node (and updates to the state information) up until the subscription expires. Notably, the SIP events model is a “softstate” model where subscriptions are not permanent and are configured to expire after a predefined amount of time and must be renewed by subsequent subscription (e.g., SIP SUBSCRIBE) messages. 
     In addition to providing SIP event information associated with watched subscribers or resources, a notifier node/server can also be adapted to provide watcher information (WINFO) to the watched subscriber or resource entity. Problems arise, however, in scenarios where multiple SIP event servers (e.g., presence state servers) are deployed to handle subscription request transactions related to a watched subscriber entity. Namely, responding to watcher information requests become difficult because there isn&#39;t a single SIP event server (e.g., a presence server) that has a complete view of all watcher entities that are subscribed to a particular watched entity. In short, multiple SIP event servers may be handling the subscription request transactions related to a single watched subscriber entity. This is particularly problematic because current specifications typically do not allow a watched subscriber entity to discover and contact the full set of servicing SIP event servers in order to acquire all of the watcher subscriber information associated with that requesting watched subscriber entity. 
     Accordingly, there exists a need for improved methods, systems, and computer readable media for providing SIP event watcher entity information in a communications network. 
     SUMMARY 
     According to one aspect, the subject matter described herein includes a system for collecting and distributing session initiation protocol (SIP) event watcher entity subscription information in a communications network are disclosed. In one embodiment, the system includes one or more notifier servers for receiving subscription requests for SIP event information associated with a plurality of watched entities from a plurality of watcher entities. The system further includes a watcher information (WINFO) server for receiving, from the notifier servers, SIP event subscription information that includes, for each watcher entity, an association between the watcher entity to each of the watched entities in which a subscription for SIP event information was requested by the watcher entity, for storing the SIP event subscription information in the WINFO server, for receiving, from one of the watched entities, a request for watcher entity subscription information associated with the requesting watched entity from one of the watched entities, and for accessing the SIP event subscription information to locate the watcher entity subscription information associated with the requesting watched entity. 
     The subject matter described herein for collecting and distributing session initiation protocol (SIP) event watcher entity subscription information in a communications network may be implemented in hardware, software, firmware, or any combination thereof. As such, the terms “function” or “module” as used herein refer to hardware, which may also include software and/or firmware components, for implementing the feature being described. In one exemplary implementation, the subject matter described herein may be implemented using a computer readable medium having stored thereon computer executable instructions that when executed by the processor of a computer control the computer to perform steps. Exemplary computer readable media suitable for implementing the subject matter described herein include non-transitory computer-readable media, such as disk memory devices, chip memory devices, programmable logic devices, and application specific integrated circuits. In addition, a computer readable medium that implements the subject matter described herein may be located on a single device or computing platform or may be distributed across multiple devices or computing platforms. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the subject matter described herein will now be explained with reference to the accompanying drawings, wherein like reference numerals represent like parts, of which: 
         FIG. 1  is block diagram illustrating an exemplary system for providing SIP event watcher entity information in a communications network according to an embodiment of the subject matter described herein; 
         FIG. 2  is a flow chart illustrating an exemplary process for providing SIP event watcher entity information in a communications network according to an embodiment of the subject matter described herein; 
         FIG. 3  is a signaling flow diagram illustrating a resource list server receiving a request for presence information according to an embodiment of the subject matter described herein; 
         FIG. 4  is a signaling flow diagram illustrating a watcher information server receiving presence subscription information according to an embodiment of the subject matter described herein; 
         FIG. 5  is a block diagram illustrating an exemplary watcher information database according to an embodiment of the subject matter described herein; 
         FIG. 6  is a signaling flow diagram illustrating a watcher information server receiving a request for watcher subscription information associated with the watched entity via a resource list server according to an embodiment of the subject matter described herein; 
         FIG. 7  is a signaling flow diagram illustrating a watcher information server receiving a request for watcher subscription information associated with a watched entity directly from the watched entity according to an embodiment of the subject matter described herein; 
         FIG. 8  is a signaling flow diagram illustrating a presence server receiving a request for presence information according to an embodiment of the subject matter described herein; 
         FIG. 9  is a signaling flow diagram illustrating a watcher information server receiving presence subscription information according to an embodiment of the subject matter described herein; 
         FIG. 10  is a block diagram illustrating an exemplary watcher information database according to an embodiment of the subject matter described herein; 
         FIG. 11  is a signaling flow diagram illustrating a watcher information server receiving a request for watcher subscription information associated with the watched entity via a presence server according to an embodiment of the subject matter described herein; and 
         FIG. 12  is a signaling flow diagram illustrating a watcher information server receiving a request for watcher subscription information associated with a watched entity directly from the watched entity according to an embodiment of the subject matter described herein. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts an exemplary communications network  100  that facilitates the collection and distribution of session initiation protocol (SIP) event watcher entity information. In one embodiment, communications network  100  may include watcher entity clients  101 - 102 , watched entity clients  103 - 105 , a plurality of notifier servers (e.g., resource list servers  107 - 109 ), a watcher information (WINFO) server  110 , and a plurality of SIP event servers  111 - 117 . In general, watcher information (WINFO) server  110  is configured to collect SIP event subscription information from the plurality of notifier servers, such as resource list servers  107 - 109 . Similarly, each of RLS servers  107 - 109  may be configured to interface with a common event server or a pool of event servers, such as SIP event servers  111 - 117 . In one embodiment as shown in  FIG. 1 , SIP event servers  111 - 117  may be presence state service servers, which are responsible for receiving and maintaining presence state information associated with watched entities clients  103 - 105 . Although the present specification primarily uses presence service as an exemplary SIP event service, other SIP event services may be handled in a similar fashion by communications network  100  without departing from the scope of the present subject matter. Other SIP event subscription services may include presence subscription service, dialog subscription service, voice mail subscription information, automatic callback subscription service, PSTN and Internet Internetworking (PINT) subscription service, conference state information, cryptographic certificates, pending consent information, http resource information, keypad markup language information, push-to-talk settings, registration state information, REFER operation progress information, policy documents, intelligent networking (IN) detection point information, user agent profile information, media statistics information, XCAP document change information, or any other event packages as that term is defined by RFC 3625 and its successor documents (if any). 
     In one embodiment, each of watcher entity client  101  and a watcher entity client  102  may comprise a computer, mobile device, or similar client machine configured to run a user agent or client software program, function, or module for accessing network servers. In one embodiment, watcher entity client  101  is associated with a watcher subscriber entity (e.g., watcher subscriber entity D) and is configured to create and send SIP SUBSCRIBE requests to a notifier server entity (e.g., a resource list server or a presence server, depending on the embodiment). The SIP SUBSCRIBE requests are subscription messages that request a SIP event subscription for change in state notifications related to one or more watched entities. In one embodiment, the SIP event subscriptions may include presence state service subscriptions (e.g., a SIP request to add a watched subscriber entity to a watcher subscriber entity&#39;s “buddy list”). In a SIP event notification architecture, these subscription requests require approval from watched entity clients. As shown in  FIG. 1 , a watcher entity client (e.g., client  101 ) may have a direct association or connection to a SIP event server (e.g., event server  113 ). It should also be noted that network  100  may include watcher clients that are subscribed to RLSs and SIP event servers, concurrently. 
     Similarly, each of watched entity client  103 , watched entity client  104 , and watched entity client  105  may comprise a computer, mobile device, or similar client machine configured to run a user agent or client software program, function, or module for accessing network servers. In one embodiment, watched entity client  103  is associated with a watched subscriber entity (e.g., watched subscriber A) and is configure to provide SIP event information (e.g., presence state information and updates) to a designated event server  113  (e.g., presence server). Although not explicitly shown in  FIG. 1 , watched entity client  103  may be configured to send SIP messages to a notifier server (e.g., RLS  107 ) that requests watcher entity information associated with watched entity A (e.g., watched entity client  103  requests a list of watcher entities that are either receiving the presence state information related to watched entity A or have requested to subscribe to watched entity A&#39;s presence information). 
       FIG. 1  also depicts a plurality of SIP event servers  111 - 117 . AS shown in  FIG. 1 , each of SIP event servers  111 - 117  may be communicatively coupled to an RLS server. In one embodiment, a SIP event server may be a presence server that is configured to collect and manage the presence state information of a watched subscriber entity and provide current presence state information and present state updates to one or more RLSs. In an alternate embodiment, communications network  100  may not employ RLSs  107 - 109 . In such a case, SIP event servers  111 - 117  may function as notifier servers and directly communicate with watcher and watched entities. SIP event severs  111 - 117  may also be configured to provide watcher entity subscription information to WINFO server  110  when RLS servers are not employed in network  100 . 
     In one embodiment, SIP event servers  111 - 117  collect SIP event state data from a plurality of watched subscriber or resource entities (e.g., watched entities  103 - 105 ). In one embodiment, a SIP event server may be a presence server that receives presence state information from one or more watched entities. For example, watched entity  103  may provide presence state information by publishing its current presence state using a status string and providing this information to SIP event server  113  (which in this case is a presence service server). In response to receiving the presence state information, SIP event server  113  may serve a “presence state document” to presence subscribers (i.e., watcher entities) of watched subscriber entity  103  or to RLSs. Presence server  103  is also configured to receive XML based presence rules from watched subscriber entity A. In one embodiment, SIP event server  113  maintains a set of presence rules for each subscription to each resource. For example, the presence rules associated with watched subscriber entity  103  may be modified such that a unique set of presence rules may exist for each of the watcher entities of watched subscriber entity A. For example, subscription refresh rules and/or the type of presence state information provided to one watcher entity client may differ from what is provided to a second watcher entity client. Moreover, a presence server may also be configured to receive publication information from different presence sources associated with the same watched subscriber entity. For example, presence server  113  may receive presence state updates related to watched subscriber A&#39;s client devices in the form of GPS location data, a text string, or a Web server connected to a calendar. 
       FIG. 1  also depicts a plurality of resource list servers (RLSs)  107 - 109  that function as notifier server entities in communications network  100 . Although only three RLSs are depicted in  FIG. 1 , any number of RLSs may be employed without departing from the scope of the present subject matter. In an alternate embodiment, network  100  may also utilize zero RLS entities and instead only employ presence servers. In one embodiment, RLS  107  functions as a notifier server in communications network  100  that receives SIP SUBSCRIBE requests sent by one or more watcher entity clients, e.g., watcher client  101 . Similarly, RLS  107  may also generate SIP NOTIFY messages for the purpose of informing watcher entity client  101  or any other watcher subscriber or resource entity of the state (or change in state) of a watched resource (e.g., the current presence state of a watched subscriber entity). 
     Typically, a resource list server (RLS) is used to store a list of watched subscriber or resource entities in which a watcher entity is interested in knowing “change in state” information. For example, an associated watcher entity client may create a resource list (e.g., a buddy list) of watched entities that is stored in an RLS. The watcher entity client may then subscribe to the list in order to obtain SIP event information (e.g., presence state information) and updates regarding the watched subscribers on the list. Upon receiving the resource list from the watcher client, the RLS attempts to acquire the SIP event information by communicating with the SIP event servers that maintain the requested SIP event information. After obtaining the SIP event information, the RLS sends a SIP NOTIFY message to the watcher entities with the current SIP event states of the different watched entities. Also, prior to the SIP event subscription expiring, an RLS may also be configured to send SIP event state updates to the watcher entities as the RLS receives them from the event servers. In the present subject matter, however, an RLS is used to provide SIP event subscription information to WINFO server  110 . The RLS creates the SIP event subscription information from receiving subscription requests from watcher entities requesting a subscription to change in state information pertaining to one or more watched entities. An RLS server may also be configured to request watcher entity subscription information on behalf of a requesting watched entity. For example, RLS  107  may receive a request for watcher information from a watched entity client  103  associated with a watched subscriber A. RLS  107  may then subsequently forward that request to WINFO server  110 . 
     In one embodiment, watcher information (WINFO) server  110  is a designated server, network element, or node that is configured to receive SIP event subscription information from notifier servers, such as an RLS or SIP event server depending on the embodiment. As mentioned above, the SIP event subscription information is generated by an RLS and may include which watcher entities are subscribed, or have requested a subscription, to the SIP event information and updates pertaining to one or more watched entities. In one embodiment, the SIP event subscription information communicated to WINFO server  110  includes watcher entity identifiers, watched subscriber entity identifiers, and subscription details. Upon receipt, WINFO server  110  provisions a database  118  with the communicated SIP event subscription information. An exemplary WINFO database is shown in  FIG. 3  (see description of  FIG. 3  below). 
     WINFO server  110  may also be configured to distribute a specific portion of the SIP event subscription information (as watcher entity subscription information) to requesting watched entities. Specifically, after being provisioned with the SIP event subscription information, WINFO server  110  may receive requests for watcher entity identification information from watched entities via an RLS server. For example, RLS server  107  receives requests for watcher information from a watched subscriber entity. RLS server  107  then forwards the watcher entity information request from the watched subscriber entity to WINFO server  110  (which is authoritative for the requesting subscriber). 
     In one embodiment, watcher information (WINFO) server  110  may be configured to handle WINFO SIP metadata event packages. A WINFO event package allows a watched entity client (e.g., watched entity client  103 ) associated with a watched subscriber (e.g., watched subscriber A) to subscribe and obtain watcher entity subscription information that identifies one or more watcher entities that are subscribed to receive (or have made a request to receive) the watched subscriber&#39;s presence information. Notably, a WINFO event package or “WINFO document” is created and sent to the requesting watched entity client so as to notify the associated watched subscriber of the watcher entities that are subscribed to the presence state information related to the watched subscriber entity or attempting to add that watched subscriber entity to a buddy list. In one embodiment, the WINFO document includes a list of subscribed watcher entities and further indicates 1) which watcher entities are presently “online” and/or have associated watcher entity clients running, 2) a list of watcher entities that have issued a subscription request to the watched subscriber entity&#39;s presence information, 3) the amount of time remaining for all outstanding presence state subscriptions, 4) and a list of all SIP event subscriptions that are currently in a pending state (i.e., not approved). 
     The advantage of using a WINFO server in a communications network is that subscription permissions may be eased. Furthermore, the use of different overload queuing techniques may be employed since the amount of subscription traffic at the WINFO server is considerably smaller as compared to a SIP event server (e.g., only the watched entity will be subscribing to a WINFO server for watcher information that is associated with the requesting watched subscriber). Furthermore, the logic associated with accepting and enforcing subscriptions may be generated and supported with greater ease. Although  FIG. 1  only depicts a single WINFO server  110  that is authoritative of watched entities  103 - 105 , additional WINFO servers authoritative of additional watched entities may be utilized in communications network  100  without departing from the scope of the present subject matter. 
       FIG. 2  is a flow chart illustrating an exemplary method  200  for providing watcher entity information according to an embodiment of the subject matter described herein. In block  202 , event servers are provisioned with SIP event status information from one or more clients associated with watched entities. In one embodiment, the events servers may include presence service servers, each of which is provisioned with presence status information from the plurality of watched subscriber entities over a period of time. In one embodiment, a presence server receives presence information when the client of a watched subscriber entity publishes its current state with a status string. 
     In block  204 , a subscription request for SIP event information associated with one or more watched entities is received at a notifier server, such as an RLS, or alternatively, a presence server if an RLS is not utilized in the network. In one embodiment, an RLS server may receive a presence service subscription request message from a client associated with a watcher entity. For example,  FIG. 3  depicts a signaling diagram in which watcher entity client  101  sends a presence service subscription request message (i.e., a SUBSCRIBE message) to RLS  107 . Namely, the presence service subscription request message sent to RLS  107  indicates that watcher entity client  101  wants to subscribe to presence status information for watched entities A and C. In one embodiment, the SUBSCRIBE message includes a list of identifiers associated with watched entities A and C. Similarly,  FIG. 3  also depicts a watcher entity client  102  that sends, to RLS  109 , a presence service subscription request message (i.e., a SUBSCRIBE message) for subscribing to presence status information for watched entities A and B.  FIG. 3  also shows RLS  107  replying to the SUBSCRIBE message with a NOTIFY message, which indicates the presence status of watched entities A and C. RLS  107  may send the NOTIFY message to watcher entity client  101  if RLS  107  already has the current present state information for watched entities A and C stored locally. Otherwise, RLS  107  must obtain the presence state information from the appropriate presence servers. 
     Returning to  FIG. 2 , in block  206 , SIP event subscription information associated with the subscription request is received at a WINFO server. In one embodiment, a WINFO server  110  receives presence subscription information associated with a subscription request sent to RLS  107 . For example,  FIG. 4  depicts RLS  107  communicating presence subscription information to WINFO server  110 , which may be authoritative for watcher entity A. Although  FIG. 4  depicts an RLS  107  sending a SIP PUBLISH message to communicate the presence subscription information, it should be understood that any other similar mechanism or message may be utilized without departing from the scope of the present subject matter. Specifically,  FIG. 4  illustrates that the presence subscription information received by WINFO server  110  includes a watcher entity identifier (for watcher entity D), a watched entity identifier (for watched subscriber A), and subscription details. In one embodiment, the subscription details may include the SIP subscription dialog information (i.e., To and From header field values including tags, Call-ID, remote and local CSeq values, remote and local Contact values, and route-set), the current subscription status, the most recent event affecting the subscription status, and the remaining subscription duration. Similarly,  FIG. 4  also depicts RLS  109  communicating a SIP PUBLISH message that includes second set of presence subscription information to WINFO server  110 . Specifically, the presence subscription information from RLS  109  is shown to include a watcher entity identifier (for watcher entity E), watched entity identifier (for watched entity A), and subscription details. Notably,  FIG. 4  shows that WINFO server  110  may receive presence service subscription information related to watched subscriber entity A from more than one notifier server source (e.g., an RLS or presence server). 
     Returning to  FIG. 2 , in block  208 , the SIP event subscription information is stored in a WINFO server. In one embodiment, the presence service subscription information received by WINFO server  110  is stored in a database  118 . For example,  FIG. 5  depicts an exemplary database  500  (which is represented in  FIG. 1  as database  118 ) which includes a column  502  that contains watched entity identifiers (i.e., watched subscriber identifiers), a column  504  that includes watcher entity identifiers (i.e., watcher subscriber identifiers), and a column  506  that includes identifiers corresponding to the RLSs serving the respective watcher entities. Although only three columns are shown in  FIG. 5 , additional columns may be included in database  500  without departing from the scope of the present subject matter. 
     Returning to  FIG. 2 , in block  210 , a request for watcher entity subscription information associated with a watched entity is received. In one embodiment, WINFO server  110  receives a request for watcher entity subscription information from the watched subscriber entity either directly or via an RLS. For example,  FIG. 6  depicts RLS  107  receiving a request for watcher entity subscription information from watched entity client  103 .  FIG. 6  further shows that the received request message is forwarded from RLS  107  to WINFO server  110 . Alternatively,  FIG. 7  depicts WINFO server  110  directly receiving, from watched entity client  103  (and not via an RLS), a request for watcher entity subscription information associated with watched entity A. 
     Returning to  FIG. 2 , in block  212 , the SIP event subscription information is accessed in order to locate the requested watcher entity subscription information. In one embodiment, WINFO server  110  accesses database  118  (as shown in  FIG. 1 ) to locate stored watcher entity subscription information that is associated with the requesting watched entity. For example, WINFO server  110  queries database  118  in order to obtain an identifier for each of the watcher entities that have subscribed to the presence information for the requesting watched entity. 
     Returning to  FIG. 2 , in block  214 , the watcher entity subscription information is provided to the requesting watched entity client. As shown in  FIG. 6 , WINFO server  110  may respond to the watcher entity subscription request from watched entity client  103  with a response message including identifiers associated with watcher entity D and watcher entity E (i.e., watcher entities that have subscribed to watched entity A&#39;s presence information). A similar response message is also depicted in  FIG. 7  where the response message is sent in response to a request message sent directly from watched entity client  103  to WINFO server  110 . In one embodiment, the response message may include a NOTIFY message that states which watcher entities are currently subscribed to the watched entity&#39;s presence information and the expiration times of those subscriptions and/or which entities have requested a subscription to the watched entity&#39;s presence information (i.e., pending requests awaiting approval). 
     As mentioned above with regard to at least one embodiment, communications network  100  may employ notifier servers that include presence servers instead of utilizing RLSs. For example,  FIG. 8  depicts a signaling diagram in which watcher entity client  101  sends a presence service subscription request message (i.e., a SUBSCRIBE message) to presence server  801 . Namely, the presence service subscription request message sent to presence server  801  indicates that watcher entity client  101  wants to subscribe to presence status information for watched entity A. In one embodiment, the SUBSCRIBE message includes an identifier associated with watched entity A. Similarly,  FIG. 8  also depicts a watcher entity client  102  that sends, to RLS  803 , a presence service subscription request message (i.e., a SUBSCRIBE message) for subscribing to presence status information for watched entity A.  FIG. 8  also shows presence server  801  replying to the SUBSCRIBE message using a NOTIFY message, which indicates the presence status of watched entity A. 
       FIG. 9  depicts presence server  801  communicating presence subscription information to WINFO server  110 , which may be authoritative for watched entity A. Although  FIG. 9  depicts presence server  801  sending a SIP PUBLISH message to communicate the presence subscription information, it should be understood that any other similar mechanism or message may be utilized without departing from the scope of the present subject matter. Specifically,  FIG. 9  illustrates that the presence subscription information received by WINFO server  110  includes a watcher entity identifier (for watcher entity D), a watched entity identifier (for watched subscriber A), and subscription details. Similarly,  FIG. 9  also depicts presence server  803  communicating a SIP PUBLISH message that includes second set of presence subscription information to WINFO server  110 . Specifically, the presence subscription information from presence server  803  is shown to include a watcher entity identifier (for watcher entity E), watched entity identifier (for watched entity A), and subscription details. Notably,  FIG. 9  shows that WINFO server  110  may receive presence service subscription information related to watched subscriber entity A from more than one notifier server source (e.g., a presence server). 
     In one embodiment, the presence service subscription information received by WINFO server  110  from the presence server is stored in database  118 . For example,  FIG. 10  depicts an exemplary database  1000  (which is represented in  FIG. 1  as database  118 ) which includes a column  1002  that contains watched entity identifiers (i.e., watched subscriber identifiers), a column  1004  that includes watcher entity identifiers (i.e., watcher subscriber identifiers), and a column  1006  that includes identifiers corresponding to the presence servers serving the respective watcher entities. Although only three columns are shown in  FIG. 5 , additional columns may be included in database  1000  without departing from the scope of the present subject matter. 
     In one embodiment, WINFO server  110  receives a request for watcher entity subscription information from the watched subscriber entity either via a presence server. For example,  FIG. 11  depicts presence server  801  receiving a request for watcher entity subscription information from watched entity client  103 .  FIG. 11  further shows that the received request message is forwarded from presence server  801  to WINFO server  110 . Alternatively,  FIG. 12  depicts WINFO server  110  directly receiving, from watched entity client  103  (and not via an RLS), a request for watcher entity subscription information associated with watched entity A. 
     It will be understood that various details of the subject matter described herein may be changed without departing from the scope of the subject matter described herein. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation.