Abstract:
A method for communication employs a plurality of gatekeepers and involves receiving at a first gatekeeper a request for information. If the information is not known by the first gatekeeper, a request is sent via a second gatekeeper to a third gatekeeper for the information. If the information is known by the third gatekeeper, it is returned to the first gatekeeper, illustratively via the second gatekeeper. The gatekeepers are at a single gatekeeper hierarchical level.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of U.S. patent application Ser. No. 09/328,667 filed Jun. 9, 1999, now U.S. Pat. No. 6,965,591 which claimed the benefit of U.S. Provisional Application No. 60/100,130, filed Sep. 14, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention involves network communication. In particular, the present invention introduces systems and methods for gatekeeper-to-gatekeeper communication for any combination of inter-zone and inter-domain gatekeepers. 
     BACKGROUND 
     The International Telecommunication Union-Telecommunication (ITU-T) has developed a recommended standard for Packet-Based Multimedia Communications Systems. The standard is called H.323. The recommendation envisions that there can be one or more zones in a given H.323 communications system. A zone can contain H.323 functional entities such as terminals, gateways, multipoint control units (MCUs), communications networks, and their resources including bandwidth, ports, buffers, and others. 
     H.323 mandates that a functional entity, which is called a gatekeeper, manages the resources within a given zone. A gatekeeper is an intelligent functional entity used to transfer signaling messages into and out of zones and domains, and contains the intelligence necessary to establish communication between communicating entities. Typically, the gatekeeper manages a single zone. 
     H.323 systems, however, are not limited to single zones. In fact, a large H.323 system can consist of multiple zones with a boundary between the zones. The zone boundary can be physical or logical. 
     While the H.323 standard defines certain requirements, the standard does have some gaps. For example, typically, certain H.323 signaling messages are transmitted between H.323 entities and the gatekeeper in a given zone only. These signaling messages include location, zone admission, bandwidth, discovery, registration, and/or other signaling messages. These messages, however, may have to travel between multiple gatekeepers in their respective source-destination paths because the first receiving gatekeeper may not be able to process the signaling message. If the first gatekeeper cannot process the signaling message, it is sent for processing to another zone&#39;s gatekeeper. The H.323 standards do not specify how these signaling messages can be sent between the gatekeepers in a multiple-gatekeeper environment. 
     Further gaps exist in H.323 requirements. For example, H.323 does not specify the possible logical architectural relationships between the gatekeepers for communications. If the gatekeepers are arranged in a hierarchical relationship, a hierarchical gatekeeper architecture may not even maintain a zone. Rather, the gatekeeper may manage a number of gatekeepers that maintain the respective zones. In a distributed non-hierarchical gatekeeper architecture, there are no specified mechanisms for signaling between gatekeepers. 
     In addition, H.323 does not provide any caching management mechanisms for the information to be acquired dynamically between the gatekeepers. Moreover, there is no notion of gatekeeper-level routing so that messages can be sent between the gatekeeper for resolving the required information where multiple gatekeepers are involved. These signaling messages lack the required fields that will facilitate the notion of routing between the gatekeepers considering the multiple gatekeepers either in multiple zones of the giving domain and/or in multiple domains where a domain consists of one or more zones. 
     SUMMARY OF THE INVENTION 
     To alleviate the problems in the prior art, the present invention introduces systems and methods for communication using gatekeeper-to-gatekeeper communication, using both inter-zone and inter-domain protocols and architectures. The invention facilitates inter-gatekeeper communications among the zones either in a given domain, or between domains, in a distributed, hierarchical, or hybrid (distributed and hierarchical) architecture. This can be done in several ways. For example, but not the only example, intergatekeeper communication can be facilitated by dynamically acquiring knowledge of the destinations served by other gatekeepers, or resources, quality-of-service, security features, pricing, traffic, and other information. As another example, but not the only example, intergatekeeper communication can be facilitated by various types of cache management and extension of the existing H.323 signaling messages. 
     In one embodiment of the present invention, a method for communication is disclosed, the method comprising the steps of receiving at a first gatekeeper a request for information and determining whether the information is known by the first gatekeeper. If the information is not known by the first gatekeeper, the request is sent via a logical gatekeeper-level path to a second gatekeeper. If the second gatekeeper knows the information, it sends the information, via a logical gatekeeper-level path, to the first gatekeeper. 
     It should be noted that a gatekeeper is an application-level entity. The lower network (e.g., routers) or link (e.g., switches) layer entities perform actual routing of messages among themselves to send the signaling messages between the gatekeepers at the instantiation of the application-layer gatekeeper request. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system overview of an embodiment of the present invention for inter-zone communications in which one gatekeeper in a given zone is communicating with other gatekeepers in a distributive-gatekeeper-architecture requirement. 
         FIG. 2  is a system overview of an embodiment of the present invention for inter-domain communications in a hierarchical-gatekeeper-architecture environment. 
         FIG. 3  is a system overview of an embodiment of the present invention for inter-domain communications in a layered hierarchical-gatekeeper-architecture environment. 
         FIG. 4  is a system overview of an embodiment of the present invention for inter-domain communications in a hybrid gatekeeper-architecture environment. 
         FIG. 5  is a flow chart depicting an embodiment of the present invention. 
         FIG. 6  is a block diagram of an embodiment of the present invention comprising a processor and a memory. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention provides systems and methods for efficient inter-zone or inter-network communication using a gatekeeper-to-gatekeeper protocol. 
       FIG. 1  is a system overview of a distributed gatekeeper system in which each gatekeeper manages and controls to its zone. Note that each gatekeeper does not have to be tied to a specific zone based on a physical boundary. The zone boundary can be logical, as well. Additionally, each gatekeeper can manage and control entry into a distinct domain or network, or there can be a combination of gatekeepers controlling any combination of zones and networks. Thus, for the purposes of the present invention, the gatekeepers are not necessarily inter-zoned gatekeepers. The gatekeepers can be inter-networked gatekeepers such that each gatekeeper is connected to a different network or domain. 
     In  FIG. 1 , subscriber terminal  101  and other entities of zone  103   a  can communicate with gatekeeper  102   a  for sending, receiving and resolving information. Similarly, subscriber terminal  105  ( 106 ) and other entities of zone  103   b  ( 103   c ) can communicate with gatekeeper  102   b  ( 102   c ). Gatekeeper  102   a  can also interact with gatekeeper  102   b . Thus, gatekeeper  102   a  can receive a request for information from subscriber  101 . Gatekeeper  102   a  can pass the query along to gatekeeper  102   b . Gatekeeper  102   a  can also contain a database in which gatekeeper  102   a  stores the requested information. Gatekeeper  102   b  and  102   c  in this embodiment can receive and send queries, and can contain a database in which various information can be stored. This information includes, but is not limited to, addresses, pricing, quality of service, resources, security features, and other information. Note that  FIG. 1  portrays gatekeepers  102   a  through  102   c , although in general there can be an arbitrary number of gatekeepers. 
     In one embodiment of the present invention, gatekeeper  102   a  can receive from subscriber  101  a query for some kind of information. This information can be any network address, the address of an application-layer resource, middleware-layer resource, transport-layer resource, and/or a network-layer resource. These resources can include, but are not limited to, bandwidth, ports, buffers, links/trunks, control processing units (CPUs) capacity, and quality-of-service parameters. 
     After receiving the query, gatekeeper  102   a  can attempt to resolve the query by searching its database for the network address. If gatekeeper  102   a  cannot resolve the query, for example, if gatekeeper  102   a  does not contain a requested IP address in its database, then gatekeeper  102   a  can query the next gatekeeper, in this case gatekeeper  102   b . Gatekeeper  102   b  receives the query from gatekeeper  102   a , and again attempts to resolve the query by searching its database. If gatekeeper  102   b  cannot resolve the query, then gatekeeper  102   b  passes the query along to the next gatekeeper, in this case gatekeeper  102   c . This process continues until a gatekeeper can resolve the query. 
     When gatekeeper  102   c  resolves the query, that is, when gatekeeper  102   c  searches its database and finds the requested network address, for example, gatekeeper  102   c  can send the network address back to gatekeeper  102   a  along the reverse path that the query was originally sent through gatekeeper  102   b . As each gatekeeper in the path receives the network address, it can store the information so that, in the future, the query can be resolved along a shorter path. Gatekeeper  102   a , the originating gatekeeper, can pass the network address on to subscriber  101  so that subscriber  101  can attempt to connect to the person using the known network address. In another embodiment of the present invention, gatekeeper  102   a  can route the call itself using the received network address. 
     Zones  103   a ,  103   b  and  103   c  are bound by communication-system entity  104 . For the purposes of this application, a communication-system entity can be a local area network, an Internet protocol network, an asynchronous transfer mode network, a frame relay network, and/or any other network. Additionally, a communication-system entity like a gatekeeper can be a middleware- or application-layer communication entity embedded above the network layer. Routers or switches, however, are lower network-layer, or link-layer, entities. These lower-layer entities will actually route the message between themselves to send the messages at the instantiation of the application-layer entity like the gatekeeper. In this way, the messages can be send between gatekeepers via the logical gatekeeper path. 
     Because the reply returns along the original path, all the intermediate gatekeepers can cache the information for some predetermined amount of time. The next time a subscriber requests that information, a gatekeeper can respond directly without forwarding the requests. Note that the reply does not have to traverse the original path, but can return along some variant of the original path. Additionally, the information does not necessarily have to be cached along the return path. 
       FIG. 2  is a system overview of a centralized gatekeeper system in which gatekeepers are arranged in a hierarchical form. In this embodiment, gatekeeper  202   a  is a centralized gatekeeper through which gatekeepers  202   b ,  202   c  and  202   d  interact. Gatekeepers  202   b ,  202   c  and  202   d  manage, in this Figure, zones  203   a ,  203   b  and  203   c , respectively. As in the distributed architecture, these gatekeepers can manage domains rather than zones. In this embodiment, gatekeeper  202   a  does not manage any one zone or domain. Gatekeeper  202   a &#39;s function is to tie together the various gatekeepers that are lower in the hierarchy (e.g.,  202   b ,  202   c  and  202   d ). In another embodiment of the present invention, a gatekeeper can be a centralized gatekeeper (connecting other gatekeepers together) while, at the same time, managing a zone or domain of its own. Note that the communication paths between the gatekeepers are always predefined. 
     In the embodiment represented by  FIG. 2 , gatekeeper  202   b  can receive a request for information from terminal  201   a . Gatekeeper  202   b  can determine whether it has the requested information. If it does, it can send the information to terminal  201   a.    
     If gatekeeper  202   b  does not contain the requested information, it can send a query to other gatekeepers through centralized gatekeeper  202   a . Gatekeeper  202   a  can receive a request for information from gatekeeper  202   b  (or any gatekeeper) and can send that request to any gatekeeper beneath it in the hierarchy. Alternatively, gatekeeper  202   a  can know which gatekeeper to contact for the information, and the request will be sent to the corresponding gatekeeper by gatekeeper  202   a . Central gatekeeper  202   a  can keep all information of all gatekeepers in its memory (but this is not necessary), and sends the response to the requesting gatekeeper of the lower hierarchy. 
       FIG. 3  is an embodiment of the present invention in which the gatekeepers are arranged in a centralized or hierarchical form that contains multiple domains and multiple levels of hierarchical gatekeepers. In this embodiment of the present invention, gatekeeper  301   a  is a centralized gatekeeper in the sense that it functions only to connect other gatekeepers with one another, and does not manage any domain or zone. In this embodiment, gatekeeper  301   a  is logically connected to gatekeepers  302   a ,  302   b , and  302   c , all of which are centralized or hierarchical gatekeepers in the same sense as gatekeeper  301   a . Gatekeeper  302   a , for example, functions only to connect logically gatekeepers  303   a  and  303   b  with each other; it does not manage any domain or zone. 
     In another embodiment of the present invention, gatekeeper  301   a ,  302   a ,  303   b  and  303   c , or any combination thereof, can each manage a domain or zone while connecting other gatekeepers lower down in the hierarchy. 
     For example, gatekeeper  302   a  manages domain  312   a , while domain  312   a  consists of two zones (not shown in  FIG. 3 ) managed by gatekeepers  303   a  and  303   b . This is, hierarchical gatekeeper  302   a  has the knowledge of the domain to resolve information while the zonal gatekeepers can resolve information that is resident to their respective zones. The same is true for domains  312   b  and  312   n . Gatekeeper  301   a , however, has the knowledge to resolve information of all domains such as  312   a ,  312   b , and  312   n . If gatekeepers  302   a ,  302   b  and  302   n  are considered at hierarchical level  1 , gatekeeper  301   a  can be considered at hierarchical level  2 . Clearly, one can create many hierarchical levels of gatekeepers. Conceptually, the communication between gatekeepers  301   a ,  302   a ,  302   b  and  302   n  can be considered as inter-domain communications. For the sake of generality, one can consider that gatekeeper  301   a  maintains its own domain. 
       FIG. 4  is a system overview of an embodiment of the present invention featuring gatekeepers arranged in a hybrid architecture consisting of both distributed and centralized (or hierarchical) architecture. In this embodiment, gatekeepers  420   a  and  420   b  communicate in a distributed environment with domain  423   a , each managing zones  422   a  and  422   b , respectively. Centralized gatekeeper  420   c , in the meantime, manages communication between gatekeepers  420   d ,  420   e , and  420   f  in domain  423   b , while gatekeepers  420   d ,  420   e  and  420   f  manage zones  422   c ,  422   d , and  422   e , respectively. 
     In this Figure, communications between domains  423   a  and  423   b  occur via gatekeepers  420   b  and  420   c.    
     The communication between gatekeepers within domain  423   a  occurs in a distributed manner while gatekeepers in domain  423   b  communicate in a hierarchical manner. The communication flow for requesting and receiving information in domain  423   a  will take place as in a distributed gatekeeper architecture that has been described in the case of  FIG. 1 , while the communications in domain  423   b  will take place in a hierarchical manner that has been described in the case of  FIG. 2 . Gatekeeper  420   b , however, will communicate with centralized gatekeeper  420   c , and this form of communication will constitute inter-domain communication between domains  423   a  and  423   b.    
       FIG. 5  is a flow chart of a method of practicing the present invention according to at least one embodiment of the present invention. It should be appreciated that the flow chart and the claims are not intended to imply a mandatory order to the invention. Rather, the steps of the flow chart and the steps of the claims can be performed in any practicable order. 
     At step  501 , a gatekeeper receives a request for information. This request for information can include a request to resolve a network address, or a request for resource information such as application-layer, middleware-layer, transport-layer and/or network-layer resources such as bandwidth, ports buffers, links/trunks, CPU capacity, and/or quality of service and performance parameters. The query can also contain registration, admission, and status signaling messages. These signaling messages can be used by a gatekeeper to handle the query. 
     At step  502 , it is determined whether the requested information is known by the first gatekeeper. If the information is known by the first gatekeeper, then at step  503  the information is retrieved from the database and the network address is returned to the querying entity in response to the query at step  504 . If the information is not known by the first gatekeeper, then at step  505  the query is passed to a second gatekeeper. The choice of the second gatekeeper can be based on the decision that will provide the best possible gatekeeper-level logical path through which the signaling message will be routed between the gatekeepers. At step  506 , the information is received from the second gatekeeper. The response to the query will always be received from the second gatekeeper (if the second gatekeeper is queried). This is because, even if the second gatekeeper cannot resolve the query, the resolved query will be returned to the first gatekeeper along a reverse path that the query originally travels. 
     At step  507 , the received information is stored in the first gatekeeper&#39;s database. At step  508 , the address is returned by the first gatekeeper in response to the originally-received query. 
     The gatekeeper serving the destination of the request for information (i.e., the last gatekeeper in the chain) can cache all resolution requests to which it has responded. The cache can help this gatekeeper to issue a “deregistration” or “parameter change” (e.g., bandwidth change) request if the information from all resolution requests to which it has responded in the reply has the possibility of changing during its lifetime. 
     In a multiple gatekeeper environment, a maximum limit can be provided for how many gatekeepers that a request can traverse before being discarded. This field can be defined as a hop count. The hop count indicates the maximum number of hop counts between the gatekeepers that a signaling message is allowed to traverse before being discarded. This field is set based on a design parameter beyond the scope of this invention, and its value depends on the specific implementation scheme of the underlying transport networking technologies. 
     In one embodiment of the present invention, each gatekeeper decrements the hop count by a quantity depending on the value that is being allocated for a path as the signaling message transits the gatekeeper on its way to the next gatekeeper along the logical-gatekeeper-routed path to the destination. If a gatekeeper receives a message that should be forwarded to another gatekeeper, and that message contains a hop count set to zero, then the gatekeeper sends an error-indication message back to the source entity, and the message is dropped. If a responding gatekeeper replies to the request, then a gatekeeper places a value in hop count as if it were sending a request of its own. 
     Using this hop count, each gatekeeper can decrement this hop-count field as a signaling message transits the gatekeeper on the way to the next gatekeeper along the path to the destination. The gatekeeper-level hop count is only considered in the context of the number of gatekeepers. Between any two gatekeepers, however, there can be one or many network (e.g. routers) or link (e.g., switches) layer entities that actually route the packets or calls among themselves. This application-layer hop count can be translated into the corresponding lower networking-layer hop count or other functional entities as appropriate depending on the corresponding transport networking technologies. In other words, the hop count is not limited to counting gatekeepers; the hop count can measure counting other entities as well. 
     In another embodiment of the present invention, the response to the query is assigned a time-to-live field. This field specifies the holding time for which the response to the query is considered valid. In this context, if the response to the query is cached, the cached information is valid up to the time specified in the time-to-live field. Thus, a transit gatekeeper lying along the path between the source entity and the responding gatekeeper can cache source binding information contained in the resolution message that it can then forward if the time-to-live value is greater than zero. 
     There are a number of other fields that can be sent in the request for information from one gatekeeper to another. These fields include, but are not limited to, a field keeping track of the various gatekeeper identifiers (i.e., a way of using data to refer to the various gatekeepers) and a field relating to end of the query chain at which the information is known. 
     In one embodiment of the present invention, when an entity desires information, it can use the corresponding registration, admission and status signaling message with an extension of the hop count, gatekeeper identifier and the last entity in the query chain. These additional three fields facilitate routing signaling messages between gatekeepers using the notion of the gatekeeper-level path to avoid looping and other associated problems. 
     If a determination is made that no gatekeeper in the system can reply to the request for the destination address, then a negative reply is returned. 
       FIG. 6  is a block diagram of an apparatus according to an embodiment of the present invention. In this embodiment, processor  601  is coupled to said port  602 . Port  602  can receive a query and send a response to a query. Memory  603  is coupled to said processor  601 . Memory  603  stores the instructions adapted to run on said processor to perform any method embodiment of the present invention. For example, memory  603  can store instructions adapted to be run on processor  601  to receive a request for information, determine whether the information is known by the gatekeeper, and if not, passing the query to another gatekeeper. In response the information can be received from the other gatekeeper, stored in memory  602   a , and returned to querying entity. Memory  603  can contain database  603   a . Database  603   a  can store network addresses that can be retrieve and passed along to processor  601  for transmission through port  602 . 
     For the purposes of this application, memory includes any medium capable of storing instructions adapted to be executed by a processor. Some examples of such media include, but are not limited to, RAM, ROM, floppy disks, CDROM, magnetic tape, hard drives, optical storage units, and any other device that can store digital information. In one embodiment, the instructions are stored on the medium in a compressed and/or encrypted format. As used herein, the phrase “adapted to be executed by a processor” is meant to encompass instructions stored in a compressed and/or encrypted format, as well as instructions that have to be compiled or installed by an installer before being executed by the processor. 
     The present invention has been described in terms of several embodiments solely for the purpose of illustration. Persons skilled in the art will recognize from this description that the invention is not limited to the embodiments described, but may be practiced with modifications and alterations limited only by the spirit and scope of the appended claims.