Patent Publication Number: US-10778554-B2

Title: Latency measurement in resource requests

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/621,022, now U.S. Pat. No. 10,079,742, entitled “LATENCY MEASUREMENT IN RESOURCE REQUESTS” and filed on Sep. 15, 2012, which in turn is a divisional of U.S. patent application Ser. No. 12/892,852, now U.S. Pat. No. 9,407,681, entitled “LATENCY MEASUREMENT IN RESOURCE REQUESTS” and filed Sep. 28, 2010, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Generally described, computing devices and communication networks can be utilized to exchange information. In a common application, a computing device can request content from another computing device via a communication network. For example, a user at a personal computing device can utilize a software browser application to request a Web page from a server computing device via the Internet. In such embodiments, the user computing device can be referred to as a client computing device and the server computing device can be referred to as a content provider. 
     Content providers are generally motivated to provide requested content to client computing devices often with consideration of efficient transmission of the requested content to the client computing device and/or consideration of a cost associated with the transmission of the content. For larger scale implementations, a content provider may receive content requests from a high volume of client computing devices, which can place a strain on the content provider&#39;s computing resources. Additionally, the content requested by the client computing devices may have a number of components, which can further place additional strain on the content provider&#39;s computing resources. 
     With reference to an illustrative example, a requested Web page, or original content, may be associated with a number of additional resources, such as images or videos, which are to be displayed with the Web page. In one specific embodiment, the additional resources of the Web page are identified by a number of embedded resource identifiers, such as uniform resource locators (“URLs”). In turn, software on the client computing devices typically processes embedded resource identifiers to generate requests for the content. Often, the embedded resource identifiers reference computing devices associated with the content provider such that the client computing devices would transmit requests for resources to the referenced content provider computing devices. 
     Some content providers attempt to facilitate the delivery of requested content, such as Web pages and/or resources identified in Web pages, through the utilization of a content delivery network (“CDN”) service provider. A CDN service provider typically maintains a number of computing devices in a communication network that can maintain content from various content providers. In turn, content providers can instruct, or otherwise suggest to, client computing devices to request some, or all, of the content provider&#39;s content from the CDN service provider&#39;s computing devices. 
     CDN service providers are also generally motivated to provide requested content to client computing devices often with consideration of efficient transmission of the requested content to the client computing device or consideration of a cost associated with the transmission of the content. Typically, CDN service providers often consider factors such as latency of delivery of requested content in order to meet service level agreements or generally improve the quality of delivery service. In turn, the CDN service provider can utilize the considered factors in processing resource requests. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a block diagram illustrative of a content delivery environment including a number of client computing devices, a content provider, and a content delivery network service provider; 
         FIG. 2  is a block diagram of the content delivery environment of  FIG. 1  illustrating the registration of a content provider with a CDN service provider; 
         FIG. 3  is a block diagram of the content delivery environment of  FIG. 1  illustrating the generation of resource requests by a client computing device; 
         FIGS. 4A-4C  are block diagrams of the content delivery environment of  FIG. 1  illustrating the generation of multiple embedded resource requests by a client computing device based on the execution of executable code; 
         FIG. 5  is a flow diagram illustrative of resource identifier processing routine implemented by a client computing device; 
         FIG. 6  is a block diagram of the content delivery environment of  FIG. 1  illustrating the registration of a content provider with a CDN service provider; 
         FIG. 7  is a block diagram of the content delivery environment of  FIG. 1  illustrating the generation of resource requests by a client computing device; 
         FIG. 8  is a block diagram of the content delivery environment of  FIG. 1  illustrating the generation of resource requests by a client computing device responsive to a redirection command provided by a CDN service provider; 
         FIG. 9  is a flow diagram illustrative of a resource request processing routine implemented by a CDN service provider; 
         FIG. 10  is a block diagram of the content delivery environment of  FIG. 1  illustrating the generation of resource requests by a client computing device; 
         FIG. 11  is a block diagram of the content delivery environment of  FIG. 1  illustrating the protocol interaction between a client computing device and multiple Points of Presence associated with a CDN service provider; and 
         FIG. 12  is a flow diagram illustrative of a resource request processing routine implemented by a CDN service provider. 
     
    
    
     DETAILED DESCRIPTION 
     Generally described, the present disclosure is directed to managing resource requests for one or more resources associated with a content provider. Specifically, aspects of the disclosure will be described with regard to the management and processing resource requests by a service provider, such as a content delivery network (“CDN”) service provider, on behalf of a content provider. Illustratively, the CDN service provider can measure the performance associated with the delivery of resources to a requesting client computing devices from various computing devices associated with the CDN service provider. In one embodiment, client computing devices can be provided executable code, such as scripts, that cause the client computing device to transmit requests to different computing devices associated with the CDN service provider&#39;s domain. Information associated with the processing of the responses can be used to measure CDN service provider latencies. In another embodiment, the CDN service provider can utilize commands responsive to an initial request for a resource that causes the requesting client computing device to transmit one or more supplemental resource requests to computing devices associated with the CDN service provider&#39;s domain. Information associated with the processing of the sequence of resource requests can be used to measure CDN service provider latencies. In a further embodiment, the CDN service provider can utilize commands corresponding to communication protocols that cause the requesting client computing device to transmit or receive protocol information from multiple computing devices associated with the CDN service provider&#39;s domain. Information associated with the processing of the protocol responses can be used to measure CDN service provider latencies. 
     Although various aspects of the disclosure will be described with regard to illustrative examples and embodiments, one skilled in the art will appreciate that the disclosed embodiments and examples should not be construed as limiting. For example, the present disclosure may be described with regard to request routing services provided by a service provider, such as a CDN service provider, that may provide additional services and functionality including network-based storage services, caching services, application hosting, or other services. However, one skilled in the relevant art will appreciate that a service provider need not provide all, or any, of the additional services or functionality that may be associated with some service providers, such as a CDN service provider. Additionally, although various embodiments will be described with regard to the measurement of performance or latencies associated with the processing of resource requests, one skilled in the relevant art will further appreciate that the various embodiments may be practiced independently or combined in various manners. 
       FIG. 1  is a block diagram illustrative of content delivery environment  100  for the management and processing of content requests. As illustrated in  FIG. 1 , the content delivery environment  100  includes a number of client computing devices  102  (generally referred to as clients) for requesting content from a content provider and/or a CDN service provider. In an illustrative embodiment, the client computing devices  102  can correspond to a wide variety of computing devices including personal computing devices, laptop computing devices, hand-held computing devices, terminal computing devices, mobile devices, wireless devices, various electronic devices and appliances and the like. In an illustrative embodiment, the client computing devices  102  include necessary hardware and software components for establishing communications over a communication network  108 , such as a wide area network or local area network. For example, the client computing devices  102  may be equipped with networking equipment and browser software applications that facilitate communications via the Internet or an intranet. 
     Although not illustrated in  FIG. 1 , each client computing device  102  can utilize some type of local DNS resolver component, such as a DNS Name server, that generates the DNS queries attributed to the client computing device  102 . In one embodiment, the local DNS resolver component may be provided by an enterprise network to which the client computing device  102  belongs. In another embodiment, the local DNS resolver component may be provided by an Internet Service Provider (ISP) that provides the communication network connection to the client computing device  102 . However, for purposes of the present disclosure, communications facilitated through a network component, such as a DNS Resolver component, will be illustrated as transmitted directly from the client computing devices  102 . 
     The content delivery environment  100  can also include a content provider  104  in communication with the one or more client computing devices  102  via the communication network  108 . The content provider  104  illustrated in  FIG. 1  corresponds to a logical association of one or more computing devices associated with a content provider. Specifically, the content provider  104  can include a web server component  110  corresponding to one or more server computing devices for obtaining and processing requests for content (such as Web pages) from the client computing devices  102 . The content provider  104  can further include an origin server component  112  and associated storage component  114  corresponding to one or more computing devices for obtaining and processing requests for network resources from the CDN service provider. One skilled in the relevant art will appreciate that the content provider  104  can be associated with various additional computing resources, such as additional computing devices for administration of content and resources, DNS name servers, and the like. For example, although not illustrated in  FIG. 1 , the content provider  104  can be associated with one or more DNS name server components that would be authoritative to resolve client computing device DNS queries corresponding to a domain of the content provider. 
     With continued reference to  FIG. 1 , the content delivery environment  100  can further include a CDN service provider  106  in communication with the one or more client computing devices  102  and the content provider  104  via the communication network  108 . The CDN service provider  106  illustrated in  FIG. 1  corresponds to a logical association of one or more computing devices associated with a CDN service provider. Specifically, the CDN service provider  106  can include a number of Point of Presence (herein “POP”) locations  116 ,  122 ,  128  that correspond to nodes on the communication network  108 . Each POP  116 ,  122 ,  128  includes a DNS component  118 ,  124 ,  130  made up of a number of DNS server computing devices for resolving DNS queries from the client computing devices  102 . Each POP  116 ,  122 ,  128  also includes a resource cache component  120 ,  126 ,  132  made up of a number of cache server computing devices for storing resources from content providers and transmitting various requested resources to various client computers. The DNS components  118 ,  124  and  130  and the resource cache components  120 ,  126   132  may further include additional software and/or hardware components that facilitate communications including, but not limited, load balancing or load sharing software/hardware components. 
     In an illustrative embodiment, the DNS component  118 ,  124 ,  130  and resource cache component  120 ,  126 ,  132  are considered to be logically grouped, regardless of whether the components, or portions of the components, are physically separate. Additionally, although the POPs  116 ,  122 ,  128  are illustrated in  FIG. 1  as logically associated with the CDN service provider  106 , the POPs will be geographically distributed throughout the communication network  108  in a manner to best serve various demographics of client computing devices  102 . Additionally, one skilled in the relevant art will appreciate that the CDN service provider  106  can be associated with various additional computing resources, such as additional computing devices for administration of content and resources, and the like. 
     With reference now to  FIGS. 2-4 , one embodiment related to the interaction between various components of the content delivery environment  100  of  FIG. 1  will be illustrated. For purposes of the example, however, the illustration has been simplified such that many of the components utilized to facilitate communications are not shown. One skilled in the relevant art will appreciate that such components can be utilized and that additional interactions would accordingly occur without departing from the spirit and scope of the present disclosure. 
     With reference to  FIG. 2 , an illustrative interaction for the optional registration of a content provider  104  with the CDN service provider  106  for hosting content on behalf of the content provider  104  will be described. As illustrated in  FIG. 2 , the CDN service provider content registration process begins with registration of the content provider  104  with the CDN service provider  106 . In an illustrative embodiment, the content provider  104  utilizes a registration application program interface (“API”) to register with the CDN service provider  106  such that the CDN service provider  106  can provide content on behalf of the content provider  104 , or at least perform the processes described herein. Illustratively, the registration API can include the identification of the origin server  112  of the content provider  104  that may provide requested resources to the CDN service provider  106 . In addition or alternatively, the registration API can include the content to be stored by the CDN service provider  106  on behalf of the content provider  104 . Additionally, the content provider  104  can specify one or more network storage providers (not illustrated) that may act as an origin server for the content provider  104 . 
     With continued reference to  FIG. 2 , upon receiving the registration API, the CDN service provider  106  obtains the registration information and generates, or otherwise obtains, embedded resource identifiers that will be utilized in the mapping of client identifiers. In an illustrative embodiment, and as will be explained in greater detail below, the embedded resource identifiers correspond to data or instructions that are processed by the client computing devices  102  to cause the client computing devices  102  to request specific resources from the CDN service provider  106 . The resources may correspond to content, such as multi-media content, that is being hosted on behalf of the content provider  104 . Additionally, in this illustrative embodiment, the CDN service provider  106  generates, or otherwise obtains, executable code that causes the client computing device to transmit resource requests to one or more computing devices associated with the CDN service provider  106 . Unlike requests related to the embedded resource identifiers, the transmission of requests to the CDN service provider  106  based on the execution of the executable code may not result in the transmittal of actual content by the CDN service provider  106 . 
     The CDN service provider  106  returns the resource identifiers and executable code to the content provider  104  along with any additional information. In turn, the content provider  104  can then store for the embedded resource identifiers for embedding in requested content or otherwise embed (or associate) the embedded resource identifiers and executable code with requested content (such as Web page markup language). In an illustrative embodiment, the embedded resource identifiers can be applicable to multiple content providers  104 . Alternatively, the embedded resource identifiers can be unique to each particular content provider  104 . Still further, the CDN service provider  106  may provide additional logic to the content providers  104  that controls the circumstances or methodologies for processing the embedded resource identifiers and executable code provided in the requested content, such as executing the executable code. For example, the embedded resource identifiers can include instructions (or executable code) that defines that the type of content (e.g., specific Web pages) for which the embedded resource identifiers will apply. 
     With reference now to  FIG. 3 , after completion of the registration and embedding processes illustrated in  FIG. 2 , a client computing device  102  generates a content request that is received and processed by the content provider  104 , such as through the Web server  110 . In accordance with an illustrative embodiment, the request for content can be in accordance with common network protocols, such as the hypertext transfer protocol (“HTTP”). Upon receipt of the content request, the content provider identifies the appropriate responsive content. In an illustrative embodiment, the requested content can correspond to a Web page that is displayed on the client computing device  102  via the processing of information, such as hypertext markup language (“HTML”), extensible markup language (“XML”), and the like. As previously described, the requested content can include a number of embedded resource identifiers that corresponds to resource objects that should be obtained by the client computing device  102  as part of the processing of the requested content. The embedded resources can corresponds to multi-media content, such as images, videos, text, etc. that will be processed by the client computing devices  102  and rendered on output device. Additionally, the requested content will also include the additional executable code previously provided by the CDN service provider  106  ( FIG. 2 ). In an illustrative embodiment, the embedded executable code previously provided by the CDN service provider  106  can be arranged in a manner such that it is processed prior to processing any other of the content in the requested content or processed in the earlier stages of the processing of the requested content, as allowed. Alternatively, the embedded executable code previously provided by the CDN service provider  106  can also be arranged such that it is processed after all any other embedded resources are processed so as to mitigate any type of interference or delay in the processing of other embedded resources/identifiers. Examples of executable code that can be included in the content requests include scripts executable by a browser software application, stand-alone executable software code, intermediate software code requiring additional processing, and the like. 
     Generally, the identification of the embedded resources provided by the content provider  104  will be in the form of resource identifiers that can be processed by the client computing device  102 , such as through a browser software application. In an illustrative embodiment, the resource identifiers can be in the form of a uniform resource locator (“URL”). For purposes of an illustrative example, the URL can identify a domain of the content provider  104  (e.g., contentprovider.com) or CDN service provider  106  (e.g., CDNserviceprovider), a name of the resource to be requested (e.g., “resource.xxx”) and a path where the resource will be found (e.g., “path”). By way of an illustrative example, the URLs of the embedded resource have the form of:
         http://www.contentprovider.com/path/resource.xxx   or   http://www.CDNserviceprovider.com/path/resource.xxx       

     Additionally, in an illustrative embodiment, any additional embedded resource identifiers previously provided by the CDN service provider  106  during the registration process ( FIG. 2 ) will also be in the form of a resource identifier (e.g., URLs) that can be processed by the client computing device  102 , such as through a browser software application. For purposes of an illustrative example, the URL can identify a domain of the CDN service provider  106  (e.g., CDNserviceprovider.com), a name of a resource to be requested (e.g., “resource.xxx”) and a path where the resource will be found (e.g., “path”). As will be explained in greater detail, the additional embedded resource identifiers previously provided by the CDN service provider  106  will identify a special resource such that a request for the special resource may not result in the delivery of an actual resource to the requesting client computing device  102 . Accordingly, additional embedded resource identifiers can correspond to a different or the same domain as the other embedded resource identifiers included in the content request. In this illustrative example, the URLs of the additional embedded resource identifiers can have the form of:
         http://www.CDNservieprovider.com/path/resoure.xxx       

     With reference now to  FIG. 4A , upon receipt of the requested content, including the embedded resource identifiers and the executable code previously provided by the CDN service provider  106 , the client computing device  102  processes the received information in a manner that causes the client computing device  102  to request embedded resource previously provided by the CDN service provider  106  from the CDN service provider  106 . In accordance with an embodiment utilizing the hypertext transfer protocol (“HTTP”), the request of a resource can correspond to a GET request transmitted by the client computing device  102  to an IP address associated with CDN service provider  106 . Although not illustrated in  FIG. 4A , the client computing device  102  would first issue a DNS query for the embedded resource previously provided by the CDN service provider  102 , which if properly resolved, would include the identification of the above mentioned IP address associated with the CDN service provider  106 . One skilled in the relevant art will appreciate that the resolution of the DNS query may involve multiple DNS queries to either the content provider  104  or CDN service provider  106 . 
     With continued reference to  FIG. 4A , the client computing device  102  also processes the executable code, such as a script, that causes the client computing device to generate one or more resource requests, or other types of data exchange between the CDN service provider  106  and the client computing device. In one embodiment, the request of a resource can also correspond to a GET request transmitted by the client computing device  102  to an IP address associated with CDN service provider  106 . However, the resulting resource request generated by the client computing device  102  does not have to result in the transmission of resource from the CDN service provider  106 . Upon receipt of the resource request, the receiving POP, POP  116  processes the request and returns a response. Illustratively, the processing of the resource request can include the collection or logging of information associated with the resource request that will allow the CDN service provider  106  to determine performance metric information. The processing of the resource request can also include the generation of identifiers or other information that is returned to the client computing device  102  and that can be collected by the client computing device for purposes of determining performance metric information. 
     In an illustrative embodiment, based on the execution of the executable code, the client computing device  102  may transmit multiple resource requests for purposes of determining latency information. For example, a client computing device  102  may transmit two resource requests to different POPs to determine latency information associated with each POP. In another example, a client computing device  102  may transmit multiple resource requests to the same POP to verify latency information, conduct a series of latency tests for a single POP, test different software applications on the client computing device  102  or CDN service provider  106 , test various Internet Service Provider (“ISP”) functionality, and the like. With reference now to  FIG. 4B , the client computing device  102  processes the executable code included in the returned content, such as a script, that causes the client computing device to generate additional resource requests, or other types of data exchange between the CDN service provider  106  and the client computing device. As described above, in one embodiment, the request of a resource can also correspond to a GET request transmitted by the client computing device  102  to an IP address associated with CDN service provider  106 . However, the resulting resource request generated by the client computing device  102  may not necessarily correspond to any content that is to be generated by the client computing device and does not have to result in the transmission of resource from the CDN service provider  106 . Upon receipt of the resource request, the receiving POP, POP  122 , processes the request and, optionally, returns a response. Illustratively, the processing of the resource request can include the collection or logging of information associated with the resource request that will allow the CDN service provider  106  to determine performance metric information. The processing of the resource request can also include the generation of identifiers or other information that is returned to the client computing device  102  and that can be collected by the client computing device for purposes of determining performance metric information. 
     Finally, with reference now to  FIG. 4C , with continued reference to an embodiment in which the executable code results in multiple resource requests to various POPs, the client computing device  102  processes the executable code, such as a script, that causes the client computing device to generate additional resource requests, or other types of data exchange between the CDN service provider  106  and the client computing device. As described above, in one embodiment, the request of a resource can also correspond to a GET request transmitted by the client computing device  102  to an IP address associated with CDN service provider  106 . Similar to the description in  FIG. 4B , the resulting resource request generated by the client computing device  102  may not necessarily correspond to any content that is to be generated by the client computing device and does not have to result in the transmission of resource from the CDN service provider  106 . Upon receipt of the resource request, the receiving POP, POP  128 , processes the request and returns a response. Illustratively, the processing of the resource request can include the collection or logging of information associated with the resource request that will allow the CDN service provider  106  to determine performance metric information. The processing of the resource request can also include the generation of identifiers or other information that is returned to the client computing device  102  and that can be collected by the client computing device for purposes of determining performance metric information. 
     Turning now to  FIG. 5 , a routine  500  implemented by a client computing device  102  for the generation of resource requests based on the execution of executable code will be described. At block  502 , the client computing device  102  transmits the original request for content. As described above, the request for content may directed to a Web server  110  of the content provider  104 . At block  504 , the client computing device  102  obtains responsive content that includes the embedded executable code provided by the CDN service provider  106  to the content provider  104 . As described above, in an illustrative embodiment, the embedded executable code can correspond to script-based instructions that can be processed by a software application running on the client computing device  102 . Still further, the translation request code can be organized in the responsive content such that the translation request is the first data processed by the client computing device  102  in accordance with the limitations of the limitations/capabilities of the networking protocols and markup language. 
     At block  506 , the client computing device  102  executes the embedded executable code and, at block  508 , transmits a first request for embedded resources to the CDN service provider  106 . As previously described, the executable code may be configured such that the resource request transmitted by the client computing device  102  is directed to a specific CDN service provider  106  component. At decision block  510 , a test is conducted to determine whether the execution of the executable code results in additional resource requests. If so, the routine  500  returns to block  508  for the generation of one or more additional resource requests. The client computing device  102  can collect and store information associated with the transmission of each resource request and receipt of any response. Additionally, the client computing device  102  can process any returned information that facilitates a determination of performance metric information. For example, the returned information may include timing information, such as a time stamp, that can be utilized to determine network latency between the transmission and receipt of a response from the CDN service provider  106 . As previously described, the additional resource requests may be configured such that they are to be received by the POP receiving the first resource request (e.g., a repeat resource request) or by a different POP within the CDN provider&#39;s domain. 
     Returning to decision block  510 , once all the resource requests have been transmitted, at block  512 , the client computing device  102  can process all collected resource request information to assist in the determination of latencies in the receipt of resources from the various components of the CDN service provider  106 . In other embodiments, the processing of resource request information may correspond to the transmission of any collected information to the CDN service provider  106 . Illustratively, the executable code provided in the returned content can include logic and functions necessary to process the resource request information and provide it to the CDN service provider  106 . Alternatively, the client computing device  102  can include additional executable code or modules, software applications, etc. that facilitate the processing and reporting of the resource request information and provide it to the CDN service provider  106 . Additionally, in embodiments in which the CDN service provider  106  obtains all the relevant information upon receipt of the resource request (e.g., embedded timing information it the request), block  512  may be omitted. At block  514 , the routine  500  terminates. 
     With reference now to  FIGS. 6-8 , another embodiment related to the interaction between various components of the content delivery environment  100  of  FIG. 1  will be illustrated. For purposes of this illustrative example, however, the illustration has been simplified such that many of the components utilized to facilitate communications are not shown. One skilled in the relevant art will appreciate that such components can be utilized and that additional interactions would accordingly occur without departing from the spirit and scope of the present disclosure. 
     With reference now to  FIG. 6 , after completion of the registration and embedding processes illustrated in  FIG. 2 , a client computing device  102  generates a content request that is received and processed by the content provider  104 , such as through the Web server  110 . In accordance with an illustrative embodiment, the request for content can be in accordance with common network protocols, such as HTTP. Upon receipt of the content request, the content provider identifies the appropriate responsive content. As described above, in an illustrative embodiment, the requested content can correspond to a Web page that is displayed on the client computing device  102  via the processing of information, such as HTML, XML, and the like. The requested content can include a number of embedded resource identifiers that corresponds to resource objects that should be obtained by the client computing device  102  as part of the processing of the requested content. The embedded resources can corresponds to multi-media content, such as images, videos, text, etc. that will be processed by the client computing devices  102  and rendered on output device. 
     As described above, the identification of the embedded resources provided by the content provider  104  will be in the form of resource identifiers that can be processed by the client computing device  102 , such as through a browser software application. In an illustrative embodiment, the resource identifiers can be in the form of a URL. For purposes of an illustrative example, the URL can identify a domain of the content provider  104  (e.g., contentprovider.com) or CDN service provider  106  (e.g., CDNserviceprovider), a name of the resource to be requested (e.g., “resource.xxx”) and a path where the resource will be found (e.g., “path”). By way of an illustrative example, the URLs of the embedded resource have the form of:
         http://www.contentprovider.com/path/resource.xxx   or   http://www.CDNserviceprovider.com/path/resource.xxx       

     Additionally, in an illustrative embodiment, the additional embedded resource identifiers previously provided by the CDN service provider  106  during the registration process ( FIG. 2 ) will also be in the form of a resource identifier (e.g., URLs) that can be processed by the client computing device  102 , such as through a browser software application. For purposes of an illustrative example, the URL can identify a domain of the CDN service provider  106  (e.g., CDNserviceprovider.com), a name of a resource to be requested (e.g., “resource.xxx”) and a path where the resource will be found (e.g., “path”). As will be explained in greater detail, the embedded resource previously provided by the CDN service provider  106  will identify a special resource such that a request for the special resource may not result in the delivery of an actual resource to the requesting client computing device  102 . As previously discussed, the additional embedded resource identifiers can correspond to a different or the same domain as the other embedded resource identifiers included in the content request. In this illustrative example, the URLs of the embedded resource have the form of:
         http://www.CDNservieprovider.com/path/resoure.xxx       

     With reference now to  FIG. 7 , upon receipt of the requested content, including the embedded resource identifiers and the executable code previously provided by the CDN service provider  106 , the client computing device  102  processes the received information in a manner that causes the client computing device  102  to request embedded resource previously provided by the CDN service provider  106  from the CDN service provider  106 . In accordance with an embodiment utilizing HTTP, the request of a resource can correspond to a GET request transmitted by the client computing device  102  to an IP address associated with CDN service provider  106 . Although not illustrated in  FIG. 7 , the client computing device  102  would first issue a DNS query for the embedded resource previously provided by the CDN service provider  102 , which if properly resolved, would include the identification of the above mentioned IP address associated with the CDN service provider  106 . One skilled in the relevant art will appreciate that the resolution of the DNS query may involve multiple DNS queries to either the content provider  104  or CDN service provider  106 . 
     As also illustrated in  FIG. 7 , a receiving POP, POP  116 , obtains the resource request and processes the request. Illustratively, the processing of the resource request can include the collection or logging of information associated with the resource request that will allow the CDN service provider  106  to determine performance metric information. Additionally, in this embodiment, the processing of the resource request also includes the generation of at least one additional resource identifier and corresponding commands that will cause the client computing device  102  to issue one or more subsequent requests for resources. In accordance with an embodiment utilizing HTTP, the response can include a resource identifier in accordance with a REDIRECT command that causes the client computing device  102  to generate a subsequent resource request. 
     With reference now to  FIG. 8 , in an illustrative embodiment, upon receipt of the response (e.g., the at least one additional resource identifier and corresponding commands) from the CDN service provider  106 , the client computing device  102  issues a subsequent resource response corresponding to the at least one additional resource identifier. In one embodiment, the additional resource identifier is configured such that the subsequent request is received at a different POP, POP  122 . In another embodiment, the additional resource identifier can be configured such that the subsequent request is received at the same POP. Based on a series of commands, the client computing device  102  or CDN service provider  106  can collect performance metric information that facilitates the determination of latency information (or other information) associated with the transmission of resource requests. 
     Turning now to  FIG. 9 , a routine  900  implemented by a CDN service provider  106  for the processing of resource requests will be described. One skilled in the relevant art will appreciate that actions/steps outlined for routine  900  may be implemented by one or many computing devices/components that are associated with the CDN service provider  106 . Accordingly, routine  900  has been logically associated as being generally performed by the CDN service provider  106 , and thus the following illustrative embodiments should not be construed as limiting 
     At block  902 , the CDN service provider  106  obtains the original request for content. As described above, the client computing device  102  transmits the request for content based on one or more embedded resource identifiers. At block  904 , the CDN service provider  106  processes the resource request. In an illustrative embodiment, the CDN service provider  106  can utilize a variety of logic in determining how to process resource requests. For example, if the resource request corresponds to an actual resource to be delivered by the CDN service provider  106 , the CDN service provider  106  can utilize various criteria to determine which resource requests will result in the delivery of the resource and which resource requests will result in the return of a REDIRECT command. In another example, the CDN service provider  106  can maintain some type of count or other selection mechanism to determine how many REDIRECT commands to provide. In still another example, the CDN service provider  106  can provide REDIRECT commands for all requests for particular resources or all requests from particular types of requesting client computing devices  102  (e.g., all client computing devices associated with a particular ISP). Additionally, the CDN service provider  106  can collect and store information associated with the transmission of each resource request and receipt of any response. 
     Once the resource request has been processed, at decision block  906 , a test is conducted to determine whether there will be additional resource requests that will be processed. If so, the CDN service provider  106  transmits the alternative resource identifier and corresponding REDIRECT command (or similar command) and the routine  900  returns to block  902  to repeat the process for the alternative resource identifier. Accordingly, the routine  900  can be repeated a number of times for a set of successive resource requests and performance metric measures. 
     Returning to decision block  906 , once all the resource requests have been received, at block  910 , the CDN service provider  106  can process all collected resource request information to assist in the determination of latencies in the receipt of resources from the various components of the CDN service provider  106 . In other embodiments, the processing of resource request information may correspond to the receipt of any collected information and processing information provided by the client computing device  102 . At block  912 , the routine  900  ends. 
     With reference now to  FIGS. 10 and 11 , another embodiment related to the interaction between various components of the content delivery environment  100  of  FIG. 1  will be illustrated. For purposes of this illustrative example, however, the illustration has been simplified such that many of the components utilized to facilitate communications are not shown. One skilled in the relevant art will appreciate that such components can be utilized and that additional interactions would accordingly occur without departing from the spirit and scope of the present disclosure. 
     With reference now to  FIG. 10 , after completion of the registration and embedding processes illustrated in  FIG. 2 , a client computing device  102  generates a content request that is received and processed by the content provider  104 , such as through the Web server  110 . In accordance with an illustrative embodiment, the request for content can be in accordance with common network protocols, such as HTTP. Upon receipt of the content request, the content provider identifies the appropriate responsive content. As described above, in an illustrative embodiment, the requested content can correspond to a Web page that is displayed on the client computing device  102  via the processing of information, such as HTML, XML, and the like. The requested content can include a number of embedded resource identifiers that corresponds to resource objects that should be obtained by the client computing device  102  as part of the processing of the requested content. The embedded resources can correspond to multi-media content, such as images, videos, text, etc. that will be processed by the client computing devices  102  and rendered on output device. 
     Although not previously discussed, in an illustrative embodiment, the client computing device  102  and the receiving POP, illustratively POP  116 , may engage in a number of communication exchanges corresponding to the communication and networking protocols utilized to exchange information and request/receive the received. For example, with regard to an HTTP-based request, the client computing device  102  may first transmit a synchronization command (e.g., a SYNC command) that elicits an acknowledgement from the receiving POP. At that point, the client computing device  102  and POP can establish a communication channel and process the resource request in a manner described above. 
     As also illustrated in  FIG. 10 , a receiving POP, POP  116 , obtains the resource request and processes the request. Illustratively, the processing of the resource request can include the collection or logging of information associated with the resource request that will allow the CDN service provider  106  to determine performance metric information. 
     With reference now to  FIG. 11 , upon the transmission of the response to the CDN service provider  106 , the communication channel is typically closed or terminated by the transmission of a termination command, such as a FIN command in HTTP. In this embodiment, the receiving POP does not transmit the termination command. Rather, the POP  116  transmits a request to another CDN service provider  106  POP, such as POP  122 , to transmit one or more commands. The POP  122  obtains the request and transmits the protocol commands to the client computing device  102 . As illustrated in  FIG. 11 , the client computing device  102  may transmit additional protocol commands, such as an acknowledgement to the original POP, POP  116 , and can include performance metric information related to the latencies associated with the transmission of protocol commands from the other POP. In an illustrative embodiment, client computing device  102  may not be aware that any of the subsequent transmissions originated from another POP. One skilled in the relevant art will appreciate that while this embodiment is illustrated with regard to specific HTTP commands, the present disclosure is not limited to any particular networking or communication protocol or specific commands or type of commands within a networking or communication protocol. 
     Turning now to  FIG. 12 , a routine  1200  implemented by a CDN service provider  106  for the processing of resource requests will be described. One skilled in the relevant art will appreciate that actions/steps outlined for routine  1200  may be implemented by one or many computing devices/components that are associated with the CDN service provider  106 . Accordingly, routine  1200  has been logically associated as being generally performed by the CDN service provider  106 , and thus the following illustrative embodiments should not be construed as limiting. 
     At block  1202 , the CDN service provider  106  obtains the original request for content. As described above, the client computing device  102  transmits the request for content based on one or more embedded resource identifiers. At block  1204 , the CDN service provider  106  initiates protocol-based interactions related to the establishment of a communication channel and request for resources. Examples of protocol interactions can include various synchronization commands, acknowledgments and the identification of the requests. Additionally, the CDN service provider  106  can collect and store information associated with the transmission of each resource request and receipt of any response. 
     Once the resource request has been processed, at decision block  1206 , a test is conducted to determine whether there will be additional interaction between the POP and the client computing device  102 . If so, the routine  1200  returns to block  1204  for additional protocol interactions. Returning to decision block  1206 , once no additional interaction is required or the CDN service provider  106  determines that it wants another component to interact with the client computing device  102 , at block  1208 , the CDN service provider  106  (through the POP) transmits a request to another POP (or other component) to transmit additional protocol communications with the client computing device  102 . 
     At block  1210 , the CDN service provider  106  can process all collected resource request information to assist in the determination of latencies in the receipt of resources from the various components of the CDN service provider  106 . In other embodiments, the processing of resource request information may correspond to the receipt of any collected information and processing information provided by to the client computing device  102 . At block  1212 , the routine  1200  ends. 
     While illustrative embodiments have been disclosed and discussed, one skilled in the relevant art will appreciate that additional or alternative embodiments may be implemented within the spirit and scope of the present invention. Additionally, although many embodiments have been indicated as illustrative, one skilled in the relevant art will appreciate that the illustrative embodiments do not need to be combined or implemented together. As such, some illustrative embodiments do not need to be utilized or implemented in accordance with scope of variations to the present disclosure. 
     Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. 
     Any process descriptions, elements, or blocks in the flow diagrams described herein and/or depicted in the attached figures should be understood as potentially representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process. Alternate implementations are included within the scope of the embodiments described herein in which elements or functions may be deleted, executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those skilled in the art. It will further be appreciated that the data and/or components described above may be stored on a computer-readable medium and loaded into memory of the computing device using a drive mechanism associated with a computer readable storing the computer executable components such as a CD-ROM, DVD-ROM, or network interface further, the component and/or data can be included in a single device or distributed in any manner. Accordingly, general purpose computing devices may be configured to implement the processes, algorithms and methodology of the present disclosure with the processing and/or execution of the various data and/or components described above. 
     It should be emphasized that many variations and modifications may be made to the above-described embodiments, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.