Abstract:
A system and method for programming applications to respond to slow links. The programming may be done during configuration of a system, or it may be implemented dynamically in response to a recently-detected change in network performance. The method includes the steps of continually monitoring links in a network, periodically calculating runtime link speeds for the links, and identifying slow links based on the monitoring and calculating. The method may additionally include the preliminary step of predefining so-called original link speed factors for the links. Runtime determination of runtime link speed factors for the respective links and comparison of the original link speed factors to the real-time link speed factors will then be used for the identification of slow links. A variety of application responses may be programmed as slow link responses.

Description:
FIELD OF THE INVENTION 
   This invention relates to distributed networks and more particularly to the identification and handling of slow network links by distributed kernel services. 
   BACKGROUND OF THE INVENTION 
   Communications in computing systems are restricted by the limitations of the available components, including not only the computing capacity but also the limitations along the communications media. Single closed systems are bound by the CPU speed and the size of the memory. In client-server systems having a single server, the transactions are bounded by the bandwidth of the network along with the CPA and memory of the server. In multi-server distributed networks, where distributed kernel services (DKS) and object request brokers are provided to handle requests, the factors influencing communications are multiplied. Not only are there endpoint restrictions (i.e., capacity of the hardware or software at an endpoint) multiplied by the number of endpoints, which may be in the millions, but also link speed restrictions multiplied by the number of links in the route for a given communications, and influenced by the amount of traffic over the route. 
   In distributed networks, the link speed between endpoints necessarily affects the speed of transmissions between the endpoints as well as the quality of those transmissions. In anticipation of slow links, some applications are preset to “assume” that the links are slow and the application&#39;s requests and transmission rates are scaled accordingly. Such is a typical practice in local area networks (LANs). In other point-to-point systems, the link speed (e.g., based on the modem speed at a client endpoint) is requested at the outset of communications and the application&#39;s responses are dynamically adapted to optimize usage of the anticipated link speed. In still other point-to-point systems, such as in the case of streaming audio and video players, the bandwidth of the connection, along with the capacity of the equipment at the receiving endpoint, are factored in to anticipate the link speed for communications and hence the streaming rate. On a point-to-point basis some applications (specifically those with SNMP device drivers) can poll to obtain the interface speed at an endpoint or can apply “ping” tests to measure the response time across a link between two endpoints. Those measurements can then be considered when tailoring the transaction to the available link speed. While the foregoing solutions are realistic for small scale point-to-point systems, they are not scalable for use in vast distributed networks where there may be one million endpoints. Moreover, those applications which can obtain interface speeds may have “stale” information; and, those applications without the ability to gather interface speed must blindly program with only InetAddresses. Often, a local server is required in each part of a network which is connected by a slow link to other distributed kernel services of the network. Since a local server is provided, all reads are done locally, with the slow link only being used for writes. 
   Delays caused by high network traffic are exacerbated by applications which continually poll for the status of the interface or link speed and the status of their pending requests, thereby further reducing overall network performance. In addition, when system administrators learn of system outages, the ability to limit traffic, for example by creating slow or time sensitive links, must be done automatically by automatic programming interfaces (APIs). When events occur, whether due to volume or outages, applications continue to poll the link and do not gracefully quit using a network resource. As a result, an error prone system of tuning each application&#39;s use of the network must be implemented, rather than providing a way for an application to determine link speed, by query or by automatic notification of a significant change in link speed, and then respond accordingly (e.g., decide whether or not to attempt to perform a task). 
   What is desirable, therefore, and what is an object of the present invention is to provide a system and method of application programming to define responses to the existence of a slow link or system outage. 
   It is another object of the invention to provide a system and method for comparing link speeds in a network for use in tailoring network usage to optimize network performance. 
   Still another object of the invention is to provide a system and method for dynamically modifying application programming to respond to a detected change in network conditions. 
   SUMMARY OF THE INVENTION 
   The foregoing and other objects are realized by the present invention which includes a system and method for programming applications to respond to slow links. The programming may be done during configuration of a system, or it may be implemented dynamically in response to a recently-detected change in network performance. The method includes the steps of continually monitoring links in a network, periodically calculating runtime link speeds for the links, and identifying slow links based on the monitoring and calculating. The method may additionally include the preliminary step of predefining so-called original link speed factors for the links. Runtime determination of runtime link speed factors for the respective links and comparison of the original link speed factors to the real-time link speed factors will then be used for the identification of slow links. A variety of application responses may be programmed as slow link responses. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in greater detail with specific reference to the appended drawings wherein: 
       FIG. 1  provides a schematic diagram of a network in which the present invention can be implemented; 
       FIG. 2  provides a schematic diagram of the components of a network server entity for implementing the present invention; 
       FIG. 3  provides a representative process flow for one aspect of the invention; and 
       FIG. 4  provides a representative process flow for another aspect of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The present invention can be implemented in any network with multiple servers and a plurality of endpoints; and is particularly advantageous for vast networks having hundreds of thousands of endpoints and links there between.  FIG. 1  provides a schematic illustration of a network for implementing the present invention. Among the plurality of servers,  101   a - 101   n  as illustrated, at least one of the servers,  101   a in  FIG. 1 , which already has some of the distributed kernel services (DKS) is designated as one of the control servers for the purposes of implementing the invention. A network has many endpoints, with endpoint being defined, for example, as one Network Interface Card (NIC) with one MAC address, IP Address which may be found in one of the servers  101   b - 101   n  or other computers  102   a - 102   c . The control server  101   a in accordance with the present invention has the components illustrated in  FIG. 2 , as part of the distributed kernel services, for providing a method including the steps of: defining link speed factors for links in the network topology; using link speed factors to identify slow links; and, defining and implementing application-based responses to detected slow links. The link speed factors may be simply endpoint data such as NIC speed, link data such as link speed, route data for a plurality of links, or some factor which is calculated from the foregoing and other network performance indicators. 
   As shown in  FIG. 2 , the server  200  includes the already available DKS core services at component  202 , which services include the object request broker (ORB)  212 , service manager  222 , and the Administrator Configuration Database  232 , among other standard DKS services. The DKS Internet Points of Presence (IPOP) Manager  203  provides the functionality for gathering network data, as is detailed in the co-pending patent application entitled “METHOD AND SYSTEM FOR MANAGEMENT OF RESOURCES LEASES IN AN APPLICATION FRAMEWORK SYSTEM”, Ser. No. 09/738,307, filed Dec. 15, 2000, the teachings of which are incorporated by reference herein. In accordance with the functionality of the DKS IPOP, endpoint and link data are gathered for use by the DKS Slow Link Manager  204 , the functions of which are further detailed below. The endpoint and link information gathering may include existing functionality such as SNMP queries for Network Interface Card (NIC) speed which will return speed data from NICs such as Ethernet cards or the like having the capability to respond to such queries. Another feature of existing network components includes the ability to generate and register responses from so-called “pings” between multiple links or endpoints to gauge the response time between two links. A Network Objects database  213  and an Endpoint Status database  223  are provided at the DKS IPOP Manager  203  for storing the information which has been gathered. Additional information which will be stored, for example at the Endpoint Status database  223 , includes notifications of device failure and the like. 
   Another existing service of the DKS is the topology polling engine at  233  of block  203  which is provided, in the form of an Internet Protocol (IP) driver, to discover the physical network as a service of DKS. The topology engine discovers the endpoints, links between endpoints, and routes comprising a plurality of links, and provides the topology map for storage in the DKS link object database  205 . While storage of topology data had been available in the past, the illustrated system includes the storage at the DKS Link Object Database  205  purely for simplicity of description, although clearly existing storage can be accessed for use by the present invention. Specifically illustrated are a storage location for the Topology Routes between Endpoint ORBS at  215  and the Traceroute of other Native Operating System (OS) route generator for non-ORB Endpoints at  225 . Clearly the location of the physical storage is not critical to the functionality of the inventive process, provided that the information is made available for use by the Slow Link Identifier Engine  214  of the DKS Slow Link Manager  204 . 
   The DKS Slow Link Manager  204  uses the topology maps, along with the link and endpoint information gathered by the DKS IPOP Manager  203  to arrive at Link Speed Factors (LSFs) and Route Speed Factors (RSFs) for each of the links and routes in the network topology. The LSFs and RSFs are also stored at the DKS Link Object Database for comparative use, as will be discussed below with reference to  FIGS. 3 and 4 . As stated above, the terms LSF and RSF are intended to encompass a plurality of measures. 
   Finally, the DKS server components at  200  include a DKS Slow Link Administrative Graphical User Interface (GUI) which can create displays in response to input from the DKS Slow Link Manager  204  in order to display for a system administrator a slow link topology map for the network. The GUI will not only be able to display the slow link information, but will also be adapted to receive user (i.e., system administrator) input for directing applications responses to slow link detection both during network configuration and dynamically during network operations. 
   The process flow for a first aspect of the present invention is provided in  FIG. 3 . When configuring a network, the DKS IP Network Object Database  213  will be initialized at  301  by discovering all the network entities which comprise a physical network. Next, the network interconnections are analyzed in order to discovery and store the network topology in the physical network topology database  233  at  303 . When all endpoints have been identified, the operational status for each of the endpoints is stored in the Endpoint Status Database  223  at step  305 . Next, the DKS Link Object Database is initialized at  307 , followed by step  308  wherein the links between endpoints are established using the physical network topology database  224 . The so-called “original” or predicted speed of each link is established by the DKS Slow Link Manager  204  and Link Speed Factors (LSFs) and Route Speed Factors (RSFs) are assigned at step  309  using the aforementioned NIC speed queries, ping responses and/or a combination of the foregoing and other network performance indicators. The LSFs and RSFs are stored at  311  in the DKS Link Object Database  205  for later use. 
   Pseudo-code for implementing the foregoing is set forth below: 
   
     
       
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
             
           
             
           
             
             
           
             
           
             
             
           
             
             
             
           
             
             
           
             
             
             
           
             
             
           
             
             
             
           
             
             
           
             
             
             
           
             
             
           
             
           
         
             
                 
             
           
           
             
               Initialize DKS IP Object Database with Network Objects 
             
           
        
         
             
                 
               Get Discovery Seed Endpoint 
             
             
                 
               Loop through all Seeds to Discovery Active Endpoints 
             
           
        
         
             
                 
               Do Snmp Get for Seed 
             
             
                 
               Get All Endpoints Seed has communicated With 
             
             
                 
               Perform Loop with all seeds and endpoints seed has communicated with: 
             
             
                 
               IS Seed active (check with ping) and Not already in IPOP ? 
             
           
        
         
             
                 
               If yes: 
             
           
        
         
             
                 
               Get Network for Endpoint 
             
             
                 
               Is Network Stored in IPOP? 
             
           
        
         
             
                 
               If no → store Network Object in IPOP 
             
             
                 
               If yes → continue 
             
           
        
         
             
                 
               GetSystem for Endpoint 
             
             
                 
               Is System Stored in IPOP? 
             
           
        
         
             
                 
               If no → store System Object in IPOP 
             
           
        
         
             
                 
               Get Link Speed for Endpoints NIC (SNMP IF Table) 
             
             
                 
               Store IF Speed for Endpoint&#39;s NIC 
             
           
        
         
             
                 
               If yes → continue 
             
           
        
         
             
                 
               If no: continue with next seed or endpoint 
             
           
        
         
             
                 
               Store Endpoints in IPOP Database 
             
           
        
         
             
               Initialize DKS Link Object Database with Network Objects 
             
           
        
         
             
                 
               Get Discovery Seed Endpoint 
             
             
                 
               Get all Endpoints 
             
             
                 
               Enter Endpoint Loop 
             
             
                 
               Get First Endpoint (EP1) 
             
           
        
         
             
                 
               Does Topology Have EP1 ? 
             
           
        
         
             
                 
               If yes: Get all Endpoints (EPn) connected to EP1 
             
           
        
         
             
                 
               Create Link using EP1 and each N Endpoint 
             
           
        
         
             
                 
               If no: Get connections from other OS native source 
             
           
        
         
             
                 
               Get all Endpoints (EPn) connected to EP1 
             
             
                 
               Create Link using EP1 and each N Endpoint 
             
           
        
         
             
                 
               Continue to next Endpoint 
             
           
        
         
             
               Class LinkSpeed { 
             
           
        
         
             
                 
               //constants Example Only 
             
             
                 
               long FASTLINKPINGRESPONSE = 5; 
             
             
                 
               long SLOWLINKPINGRESPONSE = 100; 
             
             
                 
               long FASTNIC = 100; //bps 
             
             
                 
               long SLOWNIC = 10; 
             
           
        
         
             
               } 
             
             
               Class Link { 
             
           
        
         
             
                 
               //data 
             
             
                 
               Endpoint Ep1; 
             
             
                 
               Endpoint Ep2; 
             
             
                 
               //Speed of NIC card in Endpoint 
             
           
        
         
             
                 
               Long 
               EP1NICSpeed; 
             
             
                 
               Long 
               EP2NICSpeed; 
             
           
        
         
             
                 
               //Ping from Know Endpoint within same Network as Endpoint 
             
             
                 
               //Typically represent local network speed between a local endpoint 
             
           
        
         
             
                 
               Long 
               baselinePingEP1Test; 
             
             
                 
               Long 
               baselinePingEP2Test; 
             
             
                 
               Long 
               lastPingLinkTest; 
             
           
        
         
             
                 
               //store all endpoints between EP1 and Ep2 
             
             
                 
               //For Example (EP1→EP3→EP4→Ep2) where EP3 and Ep4 are gateways 
             
           
        
         
             
                 
               Vector 
               linkRoute; 
             
           
        
         
             
                 
               //linkSpeed for all links in Route 
             
             
                 
               //For Example (EP1→EP3, EP3→EP4, EP4→EP2) where EP2 and Ep4 are gateways 
             
           
        
         
             
                 
               Vector 
               linkSpeedsforlinkRoute 
             
           
        
         
             
                 
               //get, set methods for above data 
             
             
                 
               // ..... 
             
           
        
         
             
               } 
             
             
                 
             
           
        
       
     
   
   Knowing the network topology and the LSFs and RSFs for the network, the DKS Slow Link Manager can solicit input from the system administrator to identify and implement appropriate responses to a future event comprising slow link detection. The DKS Slow Link GUI will invite system administrator input to either predefine or dynamically define network application responses to slow link events. For example, an application may be programmed to adapt its operations to the slow link by either stopping polling or at least slowing its polling activity when notified of the detection of a slow link. Another programmed application response may be to limit the transaction types, such as having the application only perform read operations until notified that the link speed has improved. Still another response which the system administrator may dictate is to limit which applications may use the link once it has been declared to be a slow link. The step  311  of programming predefined responses in  FIG. 3  is denoted as optional at the configuration stage since the responses could be dynamically determined at runtime, if so desired. It is suggested that predefining system and application responses will, however, ameliorate the speed problem much more quickly than will a runtime approach. 
   Having arrived at the LSFs and RSFs, the DKS Slow Link Manager can characterize link speed at any time during operation by measuring the runtime link speeds, arriving at runtime LSFs, and comparing the runtime values to the stored original values.  FIG. 4  provides a runtime process flow for identifying slow links in accordance with the present invention. The process of monitoring link speeds may be conducted continually, rotating among links, or may be conducted selectively based on the network topology, expected applications&#39; usage of specific links, and other criteria as may be established by the system administrator. Regardless of the criteria and timing, the process flow will comprise selecting links to be evaluated at  401  followed by monitoring runtime network performance indicators at  403 . Once the runtime network performance indicators have been measured, runtime LSFs are calculated at  404  and compared to original LSFs. If the comparison does not result in a determination that the link speed is slow, the system moves on to select another link for evaluation. If, however, the comparison shows that the link is slow, as determined at decision box  406 , a response is invited at  407 . The response which may be invited includes displaying the network condition to a system administrator and prompting runtime input to address the performance condition; notifying applications of the detected slow link to prompt their automatic response (which have been pre-programmed by the system administrator); or, the DKS Slow Link Manager automatically changing network behaviors (e.g., by denying application access for some applications; by selectively advertising links based on LSF and RSF thresholds; by rerouting application requested to use endpoint which result in the use of another endpoint in order to avoid the slow link; or by presenting the ranked links, slow to fast, so as to help an application choose the best suited link for the task at hand) to address the slow link condition. 
   Pseudo code for the foregoing is shown below: 
                                                                                                                                                       Runtime Execution to Identify Slow Links                Admin identifies Eps (EP1, EP2) of interest           GetLinkRoute for (EP1, EP2)                //Check NIC Speeds           Is EP1NICSPEED = or &gt; SLOWNIC ?                If yes return LINK is Slow to Admin           If no continue                Is EP2NICSPEED = or &gt; SLOWNIC ?                If yes return LINK is Slow to Admin           If no continue                //Check Pings within the network           Is baselinePingEP1Test = or &gt;SLOWLINKPINGRESPONSE ?                If yes return LINK is Slow to Admin           If no continue                Is baselinePingEP2Test = or &gt;SLOWLINKPINGRESPONSE ?                If yes return LINK is Slow to Admin           If no continue                //Check EP1 to EP2 ping           Is lastPingLinkTest = or &gt; SLOWLINKPINGRESPONSE ?                If yes return LINK is Slow to Admin           If no continue                Return LINK is FAST to Admin GUI                        
ADD RunTime Execution of response to slow links
 
And calculation of this factor
 
   As disclosed herein, the present invention provides for dynamic detection of slow links and for a plurality of automatic responses to the detection of a slow link condition. The invention has been described with reference to several specific embodiments, including for example the use of link speed for detection of slow links. One having skill in the relevant art will recognize that modifications may be made to the teachings which are provided by way of example without departing from the spirit and scope of the invention as set forth in the appended claims.