Patent Application
20160094427
When multiple applications on a computing device share the same limited network resources on or external to the computing device, various techniques have been used to attempt to balance the networking needs of those applications. Computer users and applications usually prefer certain trade-offs and prioritizations among applications consuming network resources. However, in practice, prior techniques for sharing network access often have not optimally realized those preferences and priorities. For example, a user of a device may prefer that Voice over IP (VoIP) calls on their device have low network latency and that web browsing on the device be snappy and responsive. The user also may prefer that background bulk network transfers, such as cloud synchronizations and operating system updates, yield their consumption of the device's network resources in a way that enables satisfactory foreground performance and maintains reasonable progress.
In addition to often failing to satisfactorily share network access, prior access-sharing techniques have often not been convenient for software developers to access or implement. For example, while Quality of Service (QoS) facilities can be helpful, they are often not available or are not implemented in a uniform manner. Most QoS technology occurs below the application level and therefore may not be reliably manipulable by applications. Most QoS approaches, Differentiated Services for instance, depend on the behavior and support of the network between two endpoints. Such support may not exist on all network paths. Regarding convenience, network sharing behavior has also been implemented within applications, but this has usually required complex network programming with little or no direct coordination between applications. Not only is it duplicative for different applications to implement their own network-sharing logic, but the different resource-sharing behaviors of applications may conflict.
While there are protocols such as LEDBAT (Low Extra Delay Background Transport) that are implemented by operating systems to allow applications to implement specific types of network-consuming behavior, coding to leverage such a protocol may increase the cost and overhead of developing an application and may make a developer less likely to use such a protocol. In addition, widely deployed low-priority TCP (Transport Control Protocol) mechanisms like LEDBAT have shortcomings and often do not provide an ideal user experience (see Internet Engineering Task Force Request for Comments 6297 for other examples). The LEDBAT protocol, for instance, only restricts TCP send windows and has no effect on the receive stream, yet most client-side Internet traffic is inbound. Even when a mechanism like LEDBAT is available without requiring complex developer coding, it may not be possible for an operating system or network stack to determine that an application should use such a mechanism. In other words, user and application intent regarding network resource conflicts has been difficult to infer and applications have rarely specified their network priorities. Nor has sharing of a device's network resources been implemented in a way that is consistent among competing applications without being susceptible to problems such as the “latecomer” phenomena (e.g., see Request For Comments 6817, section 4.4).
Techniques related to implementing and leveraging classified network streams are discussed below.
The following summary is included only to introduce some concepts discussed in the Detailed Description below. This summary is not comprehensive and is not intended to delineate the scope of the claimed subject matter, which is set forth by the claims presented at the end.
Embodiments described herein relate to classifying network streams and regulating behavior of the streams based on their respective classes. One technique for managing streams involves analyzing applications, obtaining indicia of features of the applications, and using those features to infer classes to which streams of the applications may be assigned. Another technique involves deploying beacon nodes at the edge of a network. The beacon nodes inform a stream manager about network conditions such as latencies with regard to network boundaries or regions. Another embodiment for facilitating management of streams involves a subscription service for UDP applications. A UDP application may subscribe to the service, which may be provided by an operating system hosting the application. Events are published to any subscribed UDP applications to inform the UDP applications of changes in networking conditions. The UDP applications, in turn, may adapt their internal transmission control logic.
Many of the attendant features will be explained below with reference to the following detailed description considered in connection with the accompanying drawings.
The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein like reference numerals are used to designate like parts in the accompanying description.
The related patent application referenced in the Background section describes techniques for classifying network streams and regulating use of network resources accordingly. Described herein are related methods for managing classified streams. This description will begin with an explanation of how an application's streams may be implicitly classified when the application does not explicitly classify its streams. A technique of using network-edge signals to improve network resource allocation is discussed next. Various other techniques are then discussed, including how to provide a notification service for UDP (User Datagram Protocol) applications, how to use send and receive windows to assist with regulating streams, and others.
The above-referenced patent application describes how streams for carrying network traffic may be explicitly classified by applications, for instance by using an application programming interface (API) provided by an operating system. While the approach of having an application explicitly classify its network streams is effective for aligning the application's preferences with the operating system's management of network resources, this explicit classification approach may not always be practical. For example, an application or program that has already been coded and compiled without taking advantage of stream classification facilities would, absent a shim or other work-around, most likely need to be rewritten, recompiled, retested, and redistributed. For many reasons, modifying an application may not be possible or practical.
The application profiler 102 may have a static analyzer 114 and/or a dynamic runtime analyzer 116. Either or both of these components may be used to determine which API calls 104 are issued by the application 100. Runtime API calls 104 may be identified by hooks, event listeners, or other run-time intercepts, and the runtime analyzer 116 is notified. API calls 104 may also be identified by static analysis performed by the static analyzer 114, either just prior to executing the application, at a time of installing the application, during a periodic maintenance procedure, etc. The static analysis may involve identifying linked-to libraries 106 (perhaps identified in an application manifest or in a special section of an executable file), dependencies on known operating system files, parsing configuration files or settings, etc.
Other features of the application 100 may also be collected by the application profiler 102. For example, the application profiler 102 may determine: whether the application is configured to run as a background or foreground process, for example, based on whether a terminal is associated with the application; whether the application access multimedia hardware available on its host computing device (thus suggesting a streaming class); types of content flowing into the application (e.g. hypertext markup language (HTML) code that includes a multimedia hyperlink or content), registration with a multimedia scheduler of the operating system, a network port or protocol associated with a stream, etc. Any pieces of information ascertainable about the application 100 may serve as hints about what network classifications, if any, would be appropriate for the application. In one embodiment, a remote network service may be able to provide classifications. For example, the application profiler 102 may send an identifier of an application to the service and may receive, in response, a classification provided based on metadata about the application obtained from a managed software distribution service (i.e., an online software “store”). In any case, the collected application features 118 are received by the application profiler 102 and used to attempt to determine a class for the application 100.
In one embodiment, the application profiler 102 may perform an algorithm to determine a most likely network stream class that is to be associated with the application 100. The application profiler 102 may have a set of profile-class mappings 120 that map application features to a set of predefined classes. That is, the profile-class mappings 120 may indicate which features correspond to which classes.
At step 180, the application-class mappings 122 are referenced to determine if the target application is already associated with a particular class, then at step 182 that class is used as a default class for streams of the target application. That is, streams of the target application will be managed by a stream manager (in particular, with respect to regulation of consumption of local network resources) according to the class that is already associated with the target application as indicated in the application-class mappings 122.
If, at step 180, it is determined that the target application is not already associated with a stream class, then additional steps are performed to implicitly classify the target application. At step 184, application features are collected as described above. At step 186, the profile-class mappings 120 are consulted to identify any features therein that are features of the target application. For example, if the target application uses TCP (transmission control protocol) port 8080, then the first row of the profile-class mappings may be used. In one embodiment, a running score is maintained for each of the potential classes that could be selected from a classification model. As features of the target application are matched in the profile-class mappings, the corresponding weights are added to the corresponding class scores. When all of the target application's features have been processed, at step 190 the class having the highest resulting score is selected as a default class for the target application. The class with the highest score is presumably the class that best matches the behavior or performance preferences of the target application. In other words, the scores of the respective classes indicate how well the target application's features fit the profiles of the various stream classes provided by the operating system. Approaches other than scoring may be used. For instance, a system of prioritizing features may be used (e.g., “use of libraryZ is always class C”), a combination of scoring and Boolean logic rules, may be used, etc. Regardless of how one or more target application features or traits are mapped to a class, the default class selected for the application may, at step 192, be stored in the application-class mappings 122. The next time the target application is processed, the application-class mappings 122 will cause the application profiler 102 to again use the same default class.
Other methods for implicit application or stream classification may be used. For example, a list of user settings may be maintained by the operating system, and a user interface may allow a user to associate classes with specific applications. In another embodiment, network behavior of applications may be tracked and analyzed to determine classes that applications should have. For instance communication patterns (e.g., bursty, long-duration) may be matched to particular classes. In yet another embodiment, if implicit class-application associations are stored and re-used, such associations may be re-evaluated or deleted after a period of time has passed. Moreover, if a previously classified application begins to use an explicit API for stream classification, then any previous implicit association with a class may be removed or overridden.
In one embodiment, it may be helpful for a stream manager to have information about local network conditions, and in particular the “last mile” of connectivity. In other words, the stream manager might regulate streams and contention between streams with improved efficiency or results by throttling streams based on edge network information. In this embodiment, a network, for instance a first network 222 operated by a large entity, may have beacon nodes 220 at the edge of the first network 222. The beacon nodes 220 may be implemented as new processes running on border gateways or on servers residing near a network edge, as dedicated server machines near the network edge, etc. The beacon nodes 220 may record network conditions and report those conditions back to a collecting service 224. In particular, latencies between nodes within the first network 222 may be observed and reported, as well as latencies to nodes outside the first network 222. In embodiment, known external nodes may be polled to estimate the added latency caused by communication with nodes on external networks. Moreover, the latency information may indicate different latencies at different edges of the first network 222. It may also be helpful to help identify which traffic is crossing the Internet. Non-Internet may have low latency, whereas Internet traffic may have high latency.
The edge-provided latency information may be used in various ways by a local stream manager to regulate streams. A local stream manager may obtain latency information from the collecting service 224 and use that latency information to regulate streams. In particular, when a new stream is initiated, a baseline network latency (or other property) may be obtained. The edge-related latency information may be used to set initial stream baselines to values that facilitate better stream management. The latency information may also be used for setting initial or ongoing sizes of congestion windows or send and receive windows. To elaborate on how edge-related latency information can be used in LEDBAT-like protocols, consider that the LEDBAT protocol, for example, depends on a global base latency, or the minimum latency possible through a network. The LEDBAT protocol does not mix information between streams; all streams are managed based on the base latency. Edge latency information can be used to disambiguate streams going through different networks or gateways, since the streams may have significantly varying base latencies. The edge-provided latency information can help with the disambiguation by providing a stream with a known remote endpoint and gateway (such as an Internet server going through the local machine's Internet Service Provider).
The event publication service 252 may perform a process 256. The process 256 may involve receiving signals about network resource conditions. In effect, any type of information that a stream manager 258 might use for managing streams can potentially be passed on to the event publication service for publication. In one embodiment, the event publication service 252 may collect network performance information from a network stack 254 and make its own determinations about when network conditions have changed in a way that merits notifying the subscribed applications 254. In another embodiment, the stream manager 256 may periodically push out updates about current latency and bandwidth performance of the computing device 250.
In turn, an application 254 may have custom logic 258 to handle notifications from the event publication service. For instance, after subscribing to the event publication service, an application may receive an event. The event, which might be conveyed by some form of interprocess-communication, might indicate merely that network conditions have changed and a recalibration is called for. The event might also have specific information about network conditions, such as current bandwidth or latency performance, current congestion levels, recommended window sizes, etc. The receiving application will then invoke custom code for recalibrating its network behavior. For instance, if the event indicates that one or more stream classes are underperforming or overperforming, the application may correspondingly decide to increase or decrease its current traffic throughput, suspend communication, or make other adjustments designed to improve its own behavior or to help allow better management of streams by the stream manager 256. In cases where an application implements its own transport-type features, such as a send window, a receive window, a congestion window, etc., the application may adjust those features in response to a published event.
Specifically, the stream manager 256, when managing a stream, may perform a process 280 of receiving indications of a network resource requirement or a change in local conditions. For instance, the stream may be in a high priority latency class and the stream manager 256 might determine that the stream is at or approaching a latency requirement or threshold. To assure that a latency priority or a latency floor for the stream's class is maintained, the stream manager then adjusts both the send and receive windows 272, 274 of other streams, according to their classes. This can enable the stream manager 256 to rapidly throttle those other streams (in particular, streams in a low priority class) and allow the stream in the high priority latency class to quickly operate with low latency. In one embodiment, the sizes of the send and receive windows 272, 272 may be determined according to information about delay. For example, one-way delay may be measured using TCP timestamps. Note that the size of the congestion window 274 may also be manipulated to regulate streams according to their classes. Note also that the stream manager 256 need not directly manage windows. The stream manager 256 may communicate with the network stack and inform the network stack what the window sizes should be, and then the network stack implements those sizes.
An algorithm for window manipulation can be implemented as follows. First, a stream's window size may be resized more quickly the farther away the stream is from the latency goal of its stream class. For example, if a streams' class targets a latency of under 100 ms and the current measured latency is 400 ms, then window sizes of other streams (perhaps prioritized by class) are rapidly lowered. If the current measured latency is 150 ms, then the windows sizes are gradually decreased. In other words, rate of window size modification may be a function of the difference between the current latency and the stream's target latency. A simpler resizing approach, for instance changing windows sizes by static amounts, may cause extreme fluctuations that overshoot the target latency.
Second, a previously advertised window size is not rescinded. The remote sender is allowed to fully use any window size previously advertised, but future window size advertisements may be restricted. This may help avoid any compatibility issues with the remote sender not conforming to changes that have been previously advertised.
Third, a hard minimum window size may be maintained. In some scenarios this may be relevant for several reasons. First, if a TCP stream's window size becomes lower than 2 MSS (maximum segment size), then the TCP stream can encounter delayed ACKs and subsequent increased latency. In addition, minimum throughput logic can be implemented to avoid disconnects by either end of a stream's connection due to low throughput. For example, the some HTTP (hypertext transfer protocol) servers will disconnect an HTTP session if throughput is extremely low for several minutes, even if forward progress is being made. This is partially to avoid denial of service achieved by keeping resources utilized. To achieve this minimum throughput, a heuristic may be used to keep a moving average of throughput, and network impairment may be disabled while the throughput is below the specified minimum throughput. This may allow window sizes to grow gradually rather than instantly reverting to some former values.
Other techniques may also be used in conjunction with embodiments described herein and in the above-referenced related patent application. Concerning traffic regulation, to help with freeing up latency capacity (increasing responsiveness of streams), longer delays may be induced in low-class streams by introducing wait times before sending TCP acknowledgements (ACKs). That is, ACK delays for some streams may be intentionally extended to improve responsiveness (latency) for other streams. Similarly, for upstream traffic, the ACK-receive threshold may be extended, thereby providing longer waits before timing-out on the ACKs and potentially avoiding TCP re-transmits.
In addition, application network usage contracts may be supported by exposing a manifest of one or more tiered network requirements. Examples include an application declaratively specifying a manifest with network bandwidth and latency requirements (or classes) for a Standard Definition video tier and a different set of bandwidth and latency requirements (or classes) for a High Definition video tier for video streaming applications, as well as different fidelity levels in VOIP (voice over Internet Protocol) calls so a central controller can throttle (up and down) through different tiers according to changing network conditions.
It may also be possible to expose stream priority hints to broadband providers. Providers may use the hints to offer lower cost if an application traffic allows longer delays, and conversely may fast track traffic that has been marked appropriately.
Finally, network traffic priority (per stream classes) may be used for power management. Lower priority traffic may be delayed/dropped to save power. That is, traffic may be scheduled for delayed transmission, which may allow battery power to be saved. For example, the stream manager may inform a power management module that it need not maintain power to, or start powering, a radio specifically for a particular stream's connection.
Embodiments and features discussed above can be realized in the form of information stored in volatile or non-volatile computer or device readable apparatuses, with such information able to configure the computing device 298 to perform the embodiments described herein. These apparatuses may include apparatuses such as optical storage (e.g., compact-disk read-only memory (CD-ROM)), magnetic media, holographic storage, flash read-only memory (ROM), or other devices for storing digital information. The stored information can be in the form of machine executable instructions (e.g., compiled executable binary code), source code, bytecode, or other information that can be used to enable or configure computing devices to perform the embodiments described herein. This is also deemed to include at least volatile memory such as random-access memory (RAM) and/or virtual memory storing information such as central processing unit (CPU) instructions during execution of software carrying out an embodiment, as well as non-volatile devices storing information that allows a program or executable to be loaded and executed.
This application is related to U.S. patent application Ser. No. ______, attorney docket no. 355491.01, titled “NETWORK CLASSIFICATION FOR APPLICATIONS”, filed Sep. 25, 2014, which is incorporated herein by reference.
