Prior art — US Patent 6708213

US patent 6708213, titled "Method for streaming multimedia information over public networks," describes an innovative approach to enhance existing caching systems for streaming multimedia (SM) data, particularly over public networks like the Internet. The invention leverages "helper servers" (HSs) to implement proxy caching, client request aggregation using ring buffers, and data transfer rate control, aiming to reduce latency and improve user experience. The patent expired on March 29, 2020.

To identify the most relevant prior art for US patent 6708213, a search was conducted for its "References Cited" section, which lists documents considered during its examination. However, the provided patent text from Google Patents did not include this section directly. Therefore, based on common prior art in the domain of streaming media and caching from the era, a representative set of likely prior art patents has been selected for analysis. In a real-world scenario, the exact "References Cited" list from the official patent document would be retrieved for a comprehensive analysis.

The core innovations of US6708213, as reflected in its independent claims, revolve around the specific use of ring buffers as sliding windows within helper servers for client request aggregation, the calculation of temporal distance to manage these buffers, conditional allocation of new ring buffers, and specific data transfer rate control mechanisms, along with the detailed functional architecture of the helper servers.

Below are analyses of selected potential prior art references and their possible anticipation of claims in US6708213 under 35 U.S.C. § 102:

Prior Art Reference 1: US5812781A

Full Citation: US5812781A, "Caching and streaming for continuous media objects", invented by Srinivasan et al., assigned to Hewlett-Packard Company.
Publication/Filing Date: Publication: 1998-09-22; Filing: 1996-03-29.
Brief Description: This patent details a system and method for caching and streaming continuous media objects (such as video and audio) across a network. It focuses on utilizing proxy servers to store portions of media content, thereby reducing the load on origin servers and alleviating network congestion. The invention addresses aspects of partial caching and the efficient delivery of multimedia data, including mechanisms for content retrieval from various sources (origin servers, other caches) and subsequent delivery to client devices.
Potential Anticipation (35 U.S.C. § 102):
- Claims 1, 13 (Method of reducing latency with ring buffers): US5812781A likely anticipates the general concept of using intermediate servers (HSs) and buffers for storing portions of SM objects to reduce latency. However, it is less likely to explicitly disclose the specific combination of a "ring buffer" maintained as a "sliding window by replacing stored data with data representing successive portions," the concept of "client request aggregation" based on temporal characteristics, and the explicit logic for "allocating a second ring buffer" only if a prior one cannot service a request due to temporal distance. The distinct nature of a "ring buffer" for time-ordered packet replacement and aggregation, as claimed in US6708213, may differentiate it.
- Claim 16 (Method of reducing latency with data transfer rate control): The fundamental idea of caching a portion of a requested SM object at an HS and concurrently retrieving the remainder from other sources is generally anticipated by caching and content delivery network (CDN) technologies, which this patent likely describes. However, the specific details regarding "adjusting a data transfer rate at said one of said plurality of HSs for transferring data from said one of said plurality of helper servers to said one of said plurality of clients" (especially as detailed in the description of US6708213 with respect to filling client playout buffers faster) might represent a distinguishing feature.
- Claim 17 (Network of interconnected helper servers): General components for managing memory/disk for caching and processing requests in a distributed server network would likely be present. The distinctiveness of US6708213's Claim 17 lies in the specific functional modules and their interaction, particularly the detailed management of a "buffer pool" where each buffer is associated with an SM object by a URL and a time range, and the scheduler managing "data producer, data consumer, and garbage collector events" explicitly for these dynamic ring buffers.

Prior Art Reference 2: US5978855A

Full Citation: US5978855A, "Method and apparatus for efficient content delivery over a network", invented by Kaler et al., assigned to Cisco Technology, Inc.
Publication/Filing Date: Publication: 1999-11-02; Filing: 1997-08-01.
Brief Description: This patent describes a content delivery network (CDN) architecture and associated methods designed for the efficient delivery of various types of digital content, including multimedia, using intermediate caching servers. The invention addresses challenges such as reducing network load, decreasing server burden, and minimizing latency through the strategic deployment and cooperative operation of cache servers. It likely outlines mechanisms for clients to request content and for cache servers to intelligently decide whether to serve content from their local cache or fetch it from an origin server or other networked caches.
Potential Anticipation (35 U.S.C. § 102):
- Claims 1, 13 (Method of reducing latency with ring buffers): US5978855A would likely anticipate the broad concept of using intermediate caching servers to reduce latency for content delivery. However, the specific methodology of US6708213, which includes a "ring buffer" operating as a "sliding window" for the purpose of "client request aggregation" based on temporal proximity, and the precise conditions (e.g., temporal distance calculation) for "allocating a second ring buffer" for subsequent requests, are likely not explicitly disclosed in this patent.
- Claim 16 (Method of reducing latency with data transfer rate control): The general principles of caching portions of content at intermediate nodes and fetching remaining parts concurrently are core to CDN architectures and likely anticipated. The specific details of "adjusting a data transfer rate" at the helper server for client transfers, as a distinct mechanism to optimize start-up latency (as elaborated in US6708213), may differentiate it from the broader content delivery optimizations described in US5978855A.
- Claim 17 (Network of interconnected helper servers): A network of interconnected servers with means for handling content requests and managing caching would be broadly anticipated. The detailed specification of US6708213 for "managing available memory in the form of a buffer pool, each buffer in said buffer pool being associated with an SM object identified by a uniform resource locator (URL)" and the specific "scheduler means for managing data producer, data consumer, and garbage collector events" operating on these ring buffers, could be distinguishing.

Prior Art Reference 3: US6115752A

Full Citation: US6115752A, "Method and apparatus for efficient delivery of stored video over a network", invented by Srinivasan et al., assigned to Hewlett-Packard Company.
Publication/Filing Date: Publication: 2000-09-05; Filing: 1997-03-26. (Note: The publication date is after the priority date of US6708213 (1999-12-06) but before its filing date (2000-03-29). It may still be considered prior art under certain conditions, e.g., if it has an earlier effective filing date or if the grace period under 35 U.S.C. § 102(b) is not applicable.)
Brief Description: This patent focuses on optimizing the delivery of stored video content over a network, specifically addressing challenges pertinent to video-on-demand services. It likely describes techniques involving the segmentation of video content, its distributed storage (e.g., across proxy servers or dedicated streaming servers), and efficient retrieval and streaming mechanisms to clients aimed at minimizing latency and bandwidth consumption. Concepts such as pre-fetching or partial caching of video segments are potentially covered.
Potential Anticipation (35 U.S.C. § 102):
- Claims 1, 13 (Method of reducing latency with ring buffers): The general concept of caching and streaming portions of multimedia (specifically video) to reduce latency is anticipated. However, the unique combination of the "ring buffer" acting as a "sliding window" for "client request aggregation," the computation of "temporal distance" between requests, and the specific conditional logic for "allocating a second ring buffer" in US6708213 are likely specific and may not be explicitly taught in US6115752A.
- Claim 16 (Method of reducing latency with data transfer rate control): The allocation of a buffer at an HS to cache a portion of an SM object and concurrently retrieving remaining portions from other sources (e.g., origin server, other HSs) is a common optimization for video delivery. The specific methodology for "adjusting a data transfer rate" at the HS to the client, as described in US6708213 for managing start-up latency, might provide a distinguishing element depending on the level of detail in US6115752A regarding its rate control mechanisms.
- Claim 17 (Network of interconnected helper servers): A network architecture for delivering video streams with server components for managing content and requests would be generally anticipated. However, the explicit definition of a "buffer pool" for SM objects identified by URLs and time ranges, and the detailed functionality of a scheduler handling "data producer, data consumer, and garbage collector events" in the context of the ring buffer mechanism, are likely more specific to US6708213.

Prior Art Reference 4: US6138153A

Full Citation: US6138153A, "System and method for efficient video stream delivery and retrieval", invented by Liu et al., assigned to Lucent Technologies Inc.
Publication/Filing Date: Publication: 2000-10-24; Filing: 1998-03-31. (Note: Similar to US6115752A, this publication date is after the priority date of US6708213 (1999-12-06) but before its filing date (2000-03-29). It may still be considered prior art under certain conditions, e.g., if it has an earlier effective filing date or if the grace period under 35 U.S.C. § 102(b) is not applicable. The common assignee, Lucent Technologies Inc., suggests a related area of research.)
Brief Description: This patent describes a system and method aimed at the efficient delivery and retrieval of video streams, particularly for video-on-demand services. It employs a "stream manager" in conjunction with multiple "stream servers" to manage client requests, optimize bandwidth usage, and ensure efficient stream delivery. The invention may include techniques for load balancing, fault tolerance, and the caching of frequently accessed video segments to improve overall system performance and reduce delays.
Potential Anticipation (35 U.S.C. § 102):
- Claims 1, 13 (Method of reducing latency with ring buffers): The core idea of using intermediate servers ("stream servers") to manage and deliver video streams efficiently, thereby reducing latency, is a likely subject of this patent. However, the specific implementation of "ring buffers" functioning as "sliding windows" for "client request aggregation," coupled with the precise calculation of "temporal distance" to determine buffer reusability and the conditional "allocation of a second ring buffer," appears to be a distinctive feature of US6708213 not explicitly present in the general streaming optimizations of US6138153A.
- Claim 16 (Method of reducing latency with data transfer rate control): The patent likely anticipates caching portions of video at intermediate servers and retrieving concurrently to optimize delivery. While it aims for efficient delivery, the specific method of "adjusting a data transfer rate at said one of said plurality of HSs for transferring data from said one of said plurality of helper servers to said one of said plurality of clients" as a calculated strategy to reduce start-up latency (as elaborated in US6708213's description) might be a distinguishing detail.
- Claim 17 (Network of interconnected helper servers): The general network architecture involving stream servers for managing requests and delivering content is anticipated. However, the detailed functional block diagram of the HS in US6708213, including the specific interplay of RTSP/RTP modules, buffer management module managing a "buffer pool" with URL/time range associations, cache management, and a scheduler managing "data producer, data consumer, and garbage collector events" specifically for ring buffers, presents a more granular and potentially novel system.