Abstract:
The method involves transmitting plural endpoint probes to produce plural endpoint probe results indicating the preparedness of the endpoints for calls routed thereto; identifying similarly situated endpoints; and representing each of the similarly situated endpoints by a reduced number of recorded endpoint probe results that substantially represent the inter-connective preparedness of each of the similarly situated endpoints. The apparatus includes a mapping mechanism for mapping the probe results for the similarly situated endpoints into a reduced number of endpoint probe results that substantially represent the inter-connective preparedness of each of the similarly situated endpoints, and a recording mechanism for recording the reduced number of endpoint probe results. Such mapping permits an Internet operating system (IOS) router/gateway to act as an real-time responder/service assurance agent (RTR/SAA) proxy on behalf of non-RTR/SAA capable voice over Internet protocol (VoIP) endpoints.

Description:
BACKGROUND OF THE INVENTION 
   This application is a continuation of prior U.S. Ser. No. 09/606,824, filed Jun. 28, 2000, now abandoned entitled “METHOD AND APPARATUS FOR CALL SETUP WITHIN A VOICE FRAME NETWORK”. 

   This invention relates to Internet protocol (IP) network systems in which voice or other data are sent in packets from a server to a client or vice versa. More specifically, it concerns method and apparatus for endpoint source and destination call setup within a voice over Internet protocol (VoIP) or similar voice frame network. 
   Detecting, and optionally routing around, voice frame network congestion typically is performed by a method that is similar to Internet protocol (IP) pinging. Those of skill in the art will appreciate that pinging is a method by which real-time responder (RTR) or service assurance agent (SAA) endpoint probes are transmitted and echoed across the network at call setup time to determine the inter-connective preparedness of endpoints for incoming calls. 
   A network endpoints coordination protocol (NECP) may measure network latency between network endpoints, as described in co-pending U.S. patent application Ser. No. 09/346,080 entitled A PROTOCOL TO COORDINATE NETWORK END POINTS TO MEASURE NETWORK LATENCY, filed Jul. 1, 1999, the disclosure of which is incorporated herein by reference. Network endpoints metrics such as data packet delay, jitter and loss may be obtained, as described in co-pending U.S. patent application Ser. No. 09/434,845 entitled METHOD AND APPARATUS FOR MEASURING NETWORK DATA PACKET DELAY, JITTER AND LOSS, filed Nov. 4, 1999, the disclosure of which also is incorporated herein by reference. These protocol, method and apparatus rely on RTR/SAA endpoint probe transmission and echoing with or without content modification. Both patent applications are subject to common ownership herewith by assignee Cisco Technology, Inc. 
   One recently proposed VoIP congestion detection method permits the endpoint probe to emulate a burst of actual voice packets. This provides improved fidelity to the probe results compared with a simple IP ping. The mechanism involves sending an RTR/SAA probe to the IP address of the far-end voice gateway prior to attempting a call setup to the gateway. To increase efficiency, and to reduce post-dialing delay, the voice gateway that originates the call keeps a cache of recent RTR/SAA probe results. 
   The cache allows the gateway to consolidate probe requests from plural voice ports and associated call attempts, so that a single probe test and results is shared by all voice ports and call attempts on a voice gateway. This reduces the volume of IP network traffic and congestion generated by the RTR/SAA probes themselves. This is particularly useful in conjunction with network maintenance techniques that continuously send probes to a far-end gateway to confirm connectivity on a pre-emptive basis, rather than simply at call setup time. 
   This probe result caching scheme suffers from the limitation that the number of IP addresses available as targets for VoIP calls is likely to be larger than any reasonable RTR/SAA cache size. The cache entries typically store an RTR/SAA probe result for each IP address corresponding with each distant voice gateway or VoIP endpoint. When this mechanism is used with an IP private branch exchange (PBX), each individual IP phone as part of the IP PBX may have an individual IP address. Accordingly, each individual IP phone may contribute an individual IP probe cache entry, which requires an unreasonable amount of caching time and resource, e.g. memory. 
   Moreover, not all IP targets or VoIP endpoints support RTR/SAA probe/response queries. In these cases, it is not possible to perform either initial or periodic connectivity confirmation. 
   SUMMARY OF THE INVENTION 
   This invention recognizes that the RTR/SAA probes for a group of IP phones or voice gateways situated on the same IP sub-net are likely to have almost identical RTR/SAA probe results. A significant saving in the RTR/SAA probe cache size may be obtained by consolidating the RTR/SAA probe results for a group of similarly situated IP phones or voice gateways and consolidating such probe results into a single cache entry. This mechanism also greatly increases the cache hit rate, since a call to a single phone within the distant IP PBX will provide a cached RTR/SAA result to other phones within the same IP PBX group. Cache consolidation is obtained by mapping of individual IP addresses obtained during the normal VoIP call setup process into a single IP address that is designated to represent the IP phone/gateway group. Moreover, such mapping permits an Internet operating system (IOS) router/gateway to act as an RTR/SAA responder proxy on behalf of any non-RTR capable VoIP endpoints. Accordingly, the invention may be thought of as involving both destination-consolidation, e.g. consolidating VoIP endpoint probe results, and source-consolidation, e.g. consolidating gateway endpoint probe results. 
   Preferably, the method involves transmitting plural endpoint probes to produce plural endpoint probe results indicating the preparedness of the endpoints for calls routed thereto; identifying similarly situated endpoints; and representing each of the similarly situated endpoints by a reduced number of recorded endpoint probe results that substantially represent the inter-connective preparedness of each of the similarly situated endpoints. Preferably, the apparatus includes a mapping mechanism for mapping the probe results for the similarly situated endpoints into a reduced number of endpoint probe results that substantially represent the inter-connective preparedness of each of the similarly situated endpoints, and a recording mechanism for recording the reduced number of endpoint probe results. 
   The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment which proceeds with reference to the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a system block diagram illustrating a voice frame network of which the invented method and apparatus of the invention are a part. 
       FIG. 2  is a more detailed schematic diagram of the apparatus in accordance with a preferred embodiment of the invention. 
       FIG. 3  is a flowchart illustrating the method in accordance with a preferred embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a network  10  such as the world-wide web or Internet operatively connecting one or more Internet protocol (IP) phones  12   a ,  12   b  via a voice gateway  14  and a WAN or PBX  16 . Those of skill in the art will appreciate that plural paths such as paths  18   a ,  18   b  extend through network  10 , providing alternative routing of voice or data through the network. In accordance with the invention, RTR/SAA one or more probes  20   a ,  20   b  are routed through network  10  over such paths  18   a ,  18   b  between what will be referred to herein as IP endpoints. IP endpoints, as used herein, refers broadly to IP phones  12   a ,  12   b , gateway  14 , WAN or PBX  16 , or to routers (not shown) connected thereto. Such routing of RTR/SAA probes may take the form of an IP ping mechanism, or, more preferably, may take the form of the SAA probe mechanism described and illustrated in the above-referenced co-pending patent applications. Such may be referred to herein broadly as pinging, which will comprehend both the simple IP ping echo and the more sophisticated performance metric techniques, and any such pinging or endpoint probing method and apparatus whereby a query packet is transmitted and a response packet is returned from a remote endpoint are within the spirit and scope of the invention. 
     FIG. 1  shows a probe pair, which will be understood to represent two different periods of time, wherein a first probe Pa is transmitted from voice gateway  14  to WAN/PBX  16  and a second, responsive, probe Pa is transmitted from WAN/PBX  16  back to voice gateway  14 . The invented method and apparatus recognize that WAN/PBX may stand in for IP phones  12   b  as representative of the readiness of IP phones  12   b  to respond to a call from IP phones  12   a . The invented method and apparatus also recognize that voice gateway  14  may stand in for IP phones  12   a  as representative of the readiness of IP phones  12   a  to respond to a call from IP phones  12   b . Thus, the invention involves mapping the IP address of any or all of plural IP phones  12   a  into the IP address of voice gateway  14  and of any or all or plural IP phones  12   b  into the IP address of WAN/PBX  16 , for purposes of testing interconnectivity. 
   It will be understood that such mapping for representation purposes is a very useful way to save cache space. This is because heretofore the IP address of each and every IP phone or endpoint required an individual cache entry in memory to maintain the interconnectivity status of the IP phones or endpoints. Prior to the present invention, memory requirements tended to grow without bounds. This lowered the likelihood of a cache hit when a router was attempting to determine the status of a particular IP endpoint, since only a limited number of IP endpoint status blocks could be represented as a cache entry at any particular point in time. With the present invention, the total number of IP endpoint status blocks is greatly reduced, by the mapping of plural ones of such IP endpoint addresses into a reduced number of representative IP endpoint addresses. Thus, cache size is greatly reduced and the likelihood of a cache hit is greatly increased. 
   Interconnective readiness of a particular IP endpoint is represented accurately, in accordance with the invention. This is because the mapping, in accordance with the invention, is of a particular IP address into a different IP address that is substantially representative of the particular IP address. Network proximity between the targeted IP address and the representative IP address ensures the high fidelity of the representation. For example, most of the network voice data packet delay, jitter and loss occurs at the nodes along circuitous paths  18   a ,  18   b  between voice gateway  14  and WAN/PBX  16 . In other words, very little occurs at the endpoint nodes themselves, e.g. in the routers directly coupled with gateway  14  or WAN/PBX  16 , so that the delay, jitter and loss between the IP phones themselves may be accurately represented by the delay, jitter and loss between the associated gateway and WAN/PBX. 
   Those of skill in the art will appreciate that the invention preferably takes the form of software routines that reside in voice gateway  14  and WAN/PBX  16 . This renders the invention relatively low cost and easily provided to enhance the value of the installed base of gateway and WAN/PBX endpoints. Thus, no hardware is needed and no modifications other than the installation, e.g. downloading, of software is required to realize the advantages of the invention. 
     FIG. 2  shows apparatus  22  in schematic block diagram form. Apparatus  22  preferably includes a pinging mechanism  24 , which may take any suitable form as discussed above. Apparatus  22  further includes a mapping mechanism  26  capable of mapping plural IP addresses into a reduced number of plural IP addresses representative thereof for pinging purposes. Mapping mechanism  26  may have associated therewith a database  28 , indicated in  FIG. 2  as a disk drive. It will be appreciated that the database may take any suitable form, and simply provides an associated between two or more IP phone addresses and a representative endpoint IP address. Alternatively, mapping mechanism may rely on the basic rule set forth above, or any other suitable mapping rule or rules. 
   Apparatus  22  preferably further includes a recording mechanism  30 , e.g. a memory, for storing the result of the mapping produced by mapping mechanism  26 . Recording mechanism may be operatively connected, in accordance with the invention, to a caching mechanism  32  as described by which fewer than all such IP phone addresses are stored in non-volatile, random access memory for instant access. Recording mechanism also may be operatively connected, in accordance with the invention, to a proxy reporting mechanism  34  as described. Thus, endpoint probe results such as voice data packet delay, jitter and loss may be reported to supervisory or performance assurance software based upon the stored, representative probe results. Proxy refers to the fact that an IP endpoint such as voice gateway  14  or WAN/PBX acts for reporting purposes as representative of an IP phone  12   a  or  12   b  for purpose of reporting endpoint probe results indicative of interconnectivity preparedness. 
   Individual IP addresses obtained during a normal VoIP call setup process that includes pinging are mapped to a single IP address designed to represent the IP phone/gateway group. In many cases, the mapping may replace the IP address of any individual distant IP phone/gateway with the IP address of a wide-area network (WAN) access router that connects the IP phone/gateway group to the WAN. The IP mapping can be performed in any suitable way. For example, a list of IP phone/gateway IP addresses accessible through the WAN access router may be maintained in memory. Alternatively, an IP sub-net may be identified using the following mapping rule: Any IP phone/gateway contained within the IP sub-net is represented (for RTR/SAA probe purposes) by the IP address of the WAN access router associated with the IP sub-net. 
   Yet other alternatives are possible, and are within the spirit and scope of the invention. For example, a database server may identify group membership, i.e. groups of individual members may be identified as representative of those members, thereby defining the mapping in accordance with the invention. The mapping mechanism then would simply do a database look-up, e.g. using database  28 , to determine the representative, or proxy, IP address for the individual members. Thereafter, unless the membership definition changed, the RTR/SSA responder for the individual members would be represented by the RTR/SSA responder for the IP address of the group to which the members are assigned by the database. 
     FIG. 3  illustrates the invented method in accordance with a preferred embodiment in the form of a flowchart. At  100 , plural endpoint probes are transmitted to remote IP phone addresses to produce plural endpoint probe results indicating the preparedness of the endpoints for calls routed thereto. At  102 , similarly situated ones of the plural endpoints are identified, as described above, preferably by their individual network addresses. At  104 , each of the similarly situated ones of the plural endpoints is represented by a reduced number of recorded endpoint probe results that substantially represent the preparedness of each of the similarly situated endpoints. Preferably, such representation is performed by mapping the network addresses of the identified ones of the similarly situated endpoints into a network address that is representative of the similarly situated endpoints. Optionally, such representation also involves recording the endpoint probe results for the network address of the group as representative of the preparedness of the similarly situated endpoints. 
   At  106 , the reduced number of stored endpoint probe results for each group of similarly situated endpoints is cached, so that representative probe results are readily accessible to supervisory or performance assurance software without undue latency or overhead. At  108 , the reduced number of recorded endpoint probe results are proxy-reported as representative of one or more of the similarly situated endpoints. Those of skill in the art will appreciate that typically at least one of the endpoints includes an IP phone such as any one of IP phones  12   a ,  12   b , which IP phone typically may be connected with WAN/PBX  16 . Those of skill in the art also will appreciate that typically at least one of the endpoints includes an IP voice gateway  14 . 
   Finally, those of skill in the art will appreciate that the invented method and apparatus described and illustrated herein may be implemented in software, firmware or hardware, or any suitable combination thereof. Preferably, the method and apparatus are implemented in software, for purposes of low cost and flexibility. Thus, those of skill in the art will appreciate that the method and apparatus of the invention may be implemented by a computer or microprocessor process in which instructions are executed, the instructions being stored for execution on a computer-readable medium and being executed by any suitable instruction processor. Alternative embodiments are contemplated, however, and are within the spirit and scope of the invention. Having illustrated and described the principles of my invention in a preferred embodiment thereof, it should be readily apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. We claim all modifications coming within the spirit and scope of the accompanying claims.