US 6021439

I'll search for litigation and docket information on this specific patent number, then summarize.

Let me run a few more targeted searches to check for litigation, PTAB proceedings, and current ownership.

Search result: no litigation found

Before the summary, an important negative finding:

No USPTO post-grant proceeding and no CAFC 2026 docket activity involving US 6,021,439 was found. My searches returned:

• 2026 Federal Circuit activity exists (e.g., Fed. Cir. No. 2026-2012, Contour IP Holding LLC v. GoPro, Inc., docketed July 8, 2026; Ascendis Pharma A/S v. BioMarin Pharm. Inc., No. 2026-1026, decided March 26, 2026) — none of these involve this patent.
• No PTAB/IPR/reexam record, no infringement complaint, and no invalidity contention chart identifying US 6,021,439.
• Caution on identifier collisions: searching the bare string "6021439" is dominated by an unrelated JP 6021439 B2 (Canon K.K., "固体撮像装置" / solid-state image pickup device, filed 2012-05-25, registered 2016-11-09) and by stray table rows in district-court documents (e.g., N.D. Cal. 5:2011-cv-01846) where "6021439" appears only as an artifact of a keyword-search-string list, not as an asserted patent. I did not treat any of those as hits for US 6,021,439.

I have no authoritative evidence that this patent has ever been litigated. State that as uncertainty, not as proof of absence.

Summary of US 6,021,439

Abstract (verbatim): "A method of identifying quality-of-service problems associated with a given Web server in a computer network. The Web server includes a Web page having a token declaring that quality-of-service information is to be collected. When the Web page is received at a Web client having the capability to collect the information, an indication is provided to the Web client user that the information is being collected. The collected quality-of-service information is then uploaded, preferably without any information identifying the user, either to the Web server that served the page or to a management server."

Core technical disclosure: the "instrumented" Web server / "instrumented" client architecture. A Q-o-S-enabled page carries a token (an embedded markup tag, optionally encoded or encrypted) that signals the browser to collect Q-o-S data. Metrics are derived from the timing model r = x + y + z (x = request transit, y = server processing time, z = response transit), with "Internet delay" = x + z. Exception events include broken links, server response time over threshold, Internet delay over threshold, and applet byte-code verification over threshold. Q-o-S data is uploaded anonymously to the serving Web server or to a management/proxy server, which stores, evaluates, notifies, and supports central scaling. Collection may be built into the browser, or delivered as a plug-in, standalone Java application, or Java applet; server-side components include a database, an evaluation mechanism, a correction mechanism, and a notification mechanism. The specification incorporates by reference copending application Ser. No. 08/924,986, filed Aug. 8, 1997, "WORLD WIDE WEB END USER RESPONSE TIME MONITOR," for the sequential-HTTP-request upload technique.

Plain-language overview of each independent claim

Claim 1 — the Web page itself (product claim). The claim covers a Web page formatted in a markup language on a content host in a network. It has a base HTML document plus a token that restricts given information from being divulged to a third party without the content host's consent — that "given information" being data about a quality-of-service metric tied to the content host, collected as the page is pulled across the network. The distinctive limitation is the consent/restriction function of the token, not merely the collection flag.

Claim 2 — the basic Q-o-S measurement method. Download a Web page from a server to a browser-running client, where the page includes a token declaring to the browser that Q-o-S information is to be collected; in response to receiving that page/token, collect Q-o-S information at the client; then upload the collected information from the client to a given location for later use. This is the broadest method claim — the three-step download / collect / upload loop.

Claim 13 — the managed/notification method. Like claim 2, but the upload goes specifically to a management server, and the management server then provides a notification about a given quality-of-service (e.g., alerts the served site to an outage or exception). Note this claim contains a drafting inconsistency — it recites "downloading an object" but then recites collecting in response to "receipt of the Web page including the token." I quote it literally; I am not correcting it.

Claim 16 — the client-side computer program product. A program on a computer-readable medium for a browser-equipped Web client, with three means: (a) means for determining, upon receipt of a page from the server, whether Q-o-S information is to be collected; (b) means for collecting that information responsive to the determining means; and (c) means for uploading it to a given network location. This is the software-product counterpart to claim 2.

Claim 20 — the client computer (apparatus). A computer usable as a network client, having a processor with an operating system, a Web browser, and Q-o-S monitoring means associated with the browser: means, upon the browser receiving the token-bearing page, for collecting the Q-o-S information, and means for uploading it to a given network location. Notably, claim 20's independent scope omits the notifying/displaying element (that appears only in dependent claim 21).

Claim 26 — the management server. A server in a network of instrumented Web servers (at least one serving a page with a Q-o-S-declaring token), comprising: means for storing Q-o-S information uploaded from client(s); means for evaluating that information to determine whether a Q-o-S problem occurred for the page; and means, responsive to the evaluation, for providing a notification of a given quality-of-service.

Claim 27 — the instrumented Web server. A Web server supporting a page with a Q-o-S-declaring token, comprising: means for storing uploaded Q-o-S information from client(s); means for evaluating that information to determine whether a Q-o-S problem occurred; and means, responsive to the evaluation, for taking a predetermined action to rectify the problem. The "rectify" element distinguishes it from claim 26's "notification."

Claim 28 — the overall system. A Q-o-S monitoring system: a first instrumented Web server supporting a Q-o-S-enabled page, plus at least one instrumented Web client with a browser that includes means, responsive to receiving the Q-o-S-enabled page, for collecting the Q-o-S information and for uploading it back onto the network. Claim 28's independent scope again does not require user notification; that is added by dependent claim 29, and anonymity by dependent claim 30.

Representative dependents: 3–6 add exception-event logging (broken link; Internet response time above threshold; applet download time above threshold); 7 and 15 add displaying an indication to the user; 8, 14, 19, 22, and 30 add anonymity / masking of user-identifying data; 9 vs. 10 route the upload to the serving server vs. a management server; 11 adds management-server notification of an exception event; 12 specifies the Internet; 17–18 add token identification and display; 23–25 specify a browser plug-in, a browser-running applet, and exception events; 31 adds a second instrumented Web server plus a server that notifies one of the first and second servers.

Uncertainty notes

• Assignee history: the authoritative record I have shows IBM as original and current assignee. One third-party aggregator (Unified Patents portal) surfaced an "Assignee: Microsoft Technology Licensing LLC" string adjacent to the US-6021439-A entry, but the surrounding text is a badly jumbled list of cited-by references, so I do not treat that as evidence of an assignment of this patent. I have not verified any later IBM assignment or transfer chain beyond the original assignment recorded 1997-11-14.
• Litigation: I found no authoritative evidence of any lawsuit, appeal, or PTAB challenge on US 6,021,439. Absence of search hits is not proof of absence, and my searches were not a complete docket sweep.
• Claim 13 is quoted as issued, including its apparent antecedent-basis inconsistency, per the instruction not to auto-correct patent text.