US 5790522

I'll search for authoritative information on US 5,790,522, including any CAFC litigation activity.

Let me verify details and check specifically for any 2026 CAFC activity.

Let me make one more targeted attempt to find any litigation or CAFC activity, since the record already shows the patent expired in 2015.

US 5,790,522 — Analyst Summary

Verification / provenance note

I was able to confirm the record two ways: the full granted text hosted on Google Patents (https://patents.google.com/patent/US5790522/en) and the Justia/FPO mirror of the same grant (https://patents.justia.com/patent/5790522). I could not directly query USPTO PatentCenter or the CAFC docket system, and my searches returned no CAFC 2026 docket activity for 5,790,522. Treat the litigation portion below as "no evidence found," not proof of absence.

Bibliographic data (all identifiers taken literally)

Discrepancies to flag (not auto-corrected):

• One aggregator (Unified Patents) rendered a date of "1994-10-06" for this record, versus the 1994-10-07 priority date shown on Google Patents and in the EP family entry. I cannot resolve which is authoritative without the EP register, and I am reporting both literally.
• Searches surfaced a number of near-miss numbers (e.g., 5,790,520 to Iwamoto et al.; 5,788,220; 5,488,496), none of which is the patent in question. The 5,790,522 citations that did appear are genuine third-party citations to this patent (e.g., in BT's US 7,349,343 reference list), not substitutes.

Abstract (verbatim substance)

Traffic congestion control is provided for a network node multiport switch capable of switching data packets of different priorities from input lines, via receive adapters, to output lines via transmit adapters. A spacing function limits the rate of data transfers through the switch in the absence of high priority data at the input lines and in the absence of a backpressure signal indicating the switch is congested at its output. If high priority data is detected or a backpressure signal has been generated, the data transfer rate is increased to deal with possible congestion.

Plain-language overview of the independent claims

Claim 1 — Method (spacing controlled by high-priority detection).
In a network node whose multiport switch has receive adapters with multiple priority-based input buffers, transmit adapters, and a switch fabric that moves packets at a predetermined transfer rate, the improved congestion-control method is:

1. Monitor the input buffers for packets at a predetermined priority level;
2. Enable a "spacing function" when no such packets are present — spacing forces non-predetermined-priority packets into the fabric at a rate lower than the switch's predetermined rate;
3. Disable spacing as soon as packets of the predetermined priority are detected, restoring transfer to the full predetermined rate.

Claim 5 — Method (throttle-only-when-idle variant).
In a network whose multiport switch can transfer up to a maximum rate: cause the switch to transfer below maximum only while no high-priority packets are detected at the switch input; raise the rate back to maximum if one or more high-priority packets appear at the input. This is the same concept as claim 1 stated at a higher level of generality, without the buffer-monitoring machinery.

Claim 6 — Apparatus (the switch itself).
An improved multiport switch comprising: receive adapters with multiple priority-ordered input buffers; transmit adapters; a switch fabric; and a manager module that drives enqueued packets from the buffers into the fabric at no more than a first rate when no high-priority packets are enqueued, and at a second, higher rate when high-priority packets are detected in the buffers.

Dependent claims (for context, from the granted claim set):

• 2 — the predetermined priority level is real-time data (voice/video).
• 3 — at least three priority levels, two below the predetermined one, with at least two sub-maximum transfer rates.
• 4 — adds per-buffer threshold levels: monitor buffer occupancy and allow spacing only while below threshold, otherwise disable spacing (this is the threshold-controlled spacing of Figs. 7–9: TH1–TH4 at 10/15/20/25 Mbps mapping to spacing codes 4/3/2/1/0, i.e., 1/5, 2/5, 3/5, 4/5, full 266 Mbps).
• 7 — at least two distinct low-priority levels, with the number of selectable transfer rates equal to the number of priority levels.
• 8 — adds buffer registers holding threshold values, a threshold detector emitting a limit signal, and means responsive to the limit signal to increase the transfer rate from receive adapter to switching fabric.

Practitioner-relevant observations

1. The backpressure override is described but not claimed. The specification and abstract both recite that a switch-generated backpressure (BP) signal overrides spacing to raise the transfer rate, and the specification adds timer values T1 (NRT, ~1–10 switch cell cycles) and T2 (NR, larger than T1). However, none of independent claims 1, 5, or 6 recites a backpressure signal as a positive limitation in the granted text. The claim scope is anchored on high-priority-packet detection as the trigger to disable spacing. This is a meaningful scope gap worth noting for any invalidity or infringement analysis.
2. Claim 5 is broader than claim 1 in that it omits the buffer-monitoring and fabric-rate framework, but it is still tied to a multiport switch and to "high priority packets … at the input."
3. The claimed mechanism is counter-intuitive: spacing is on by default (throttling low-priority traffic to protect the fabric), and the switch is speeded up — not slowed — when high-priority traffic arrives or backpressure occurs.

Litigation / CAFC status

• No CAFC 2026 docket entry, appeal, or Federal Circuit proceeding referencing 5,790,522 was found in my searches.
• The patent's recorded legal status is Expired – Lifetime, with anticipated expiration 2015-06-23 (20 years from the 1995-06-23 filing). A 2026 appeal involving this number would be anomalous given expiration, though I cannot rule out a collateral proceeding (e.g., a PTAB/IPR or an appeal of an earlier district-court judgment) that my searches simply did not surface.
• The patent is, however, heavily cited: 127 "cited by" entries in the Google Patents listing (including Cisco, Ericsson, Nokia, Lucent, AT&T, Mellanox, Avaya families) and 6 examiner-cited references — notably US 5,268,900 (Hluchyj et al., Codex), US 5,475,682 (Choudhury et al., AT&T), US 5,550,823 (Irie et al., NEC), US 5,570,348 (Holden, Integrated Telecom Technology), WO 93/20637 (Stratacom), and EP 0609114 (Thomson-CSF).

Uncertainty disclosure: I am highly confident about the bibliographic data and claim text because they come from the authoritative grant text supplied above. I am not in a position to assert authoritatively that no 2026 CAFC matter exists — my tooling returned no results, which is evidence of absence only. Anyone relying on the litigation point should re-check the CAFC docket and PACER directly.

I'll research litigation involving US patent 5790522 across patent litigation databases.

Let me search more targeted litigation sources.

Let me try more targeted litigation database queries.

Litigation Search Results: US Patent 5,790,522

Bottom line: I found no evidence of any litigation involving US Patent 5,790,522.

What I searched and what came back

I ran targeted queries against patent-litigation-oriented sources (including patent database aggregators surfaced via search, court-records aggregators like CourtListener/RECAP, and PTAB materials), using the exact identifiers:

• US patent 5790522 litigation
• "5790522" patent lawsuit infringement
• "5,790,522" patent infringement complaint
• Cisco "5790522" patent lawsuit
• US5790522 infringement suit ... asserted

Every result was either:

1. False-positive numeric matches — unrelated uses of the string "5790522" (e.g., a Lithuanian company-registry notice number, a Brazilian JUCEG filing number, an ASICS Brasil entry). These are not patent-identifier matches and I have not treated them as such.
2. Unrelated litigation — cases involving different patents (e.g., Contour IP Holding v. GoPro, Linksmart Wireless v. T-Mobile, Cadence v. Narwal, ABC IP v. 80Mills). None of these involve US 5,790,522.
3. Bibliographic/reference entries for US 5,790,522 itself (Justia, Google Patents, Patent Leaderboard inventor listings), which show the patent being cited by later patents but do not evidence any suit.

No complaint, docket entry, PACER filing, CAFC appeal, or PTAB proceeding referencing US 5,790,522 was located.

Patent ownership context (relevant to why a suit might exist)

Per the authoritative patent text:

• Original assignee: International Business Machines Corp. (IBM)
• Inventors: Aline Fichou, Claude Galand, Ilias Iliadis, Xavier Jacquart, Philippe Louis, Victor Spagnol, Edward Suffern
• Priority date: 1994-10-07; Filed: 1995-06-23; Granted: 1998-08-04
• Reassignment trail: Assigned to Cisco Systems, Inc. (2000-06-14), then to Cisco Technology, Inc. (2000-04-27)
• Legal status: Expired – Lifetime (anticipated expiration 2015-06-23)

Because the patent expired in 2015, any infringement action would necessarily have been filed before that date (assuming the patent was not extended or the suit involved pre-expiration damages).

Caveats and confidence level

• Confidence: moderate-to-high that no litigation exists, but I cannot certify this. My searches did not return a unified "litigated patents" dataset page (e.g., a direct Unified Patents caselist entry) for this number, and one later query hit a tool limit before completion.
• PACER and the CAFC docket were not directly queried in this session; I relied on search-engine-indexed results that reference those sources. A definitive negative would require running the patent number directly through PACER's docket search and the Unified Patents litigation portal.
• Recommendation to confirm the negative: search PACER (https://pacer.uscourts.gov / CourtListener RECAP) for "5,790,522," and the Unified Patents case list (https://portal.unifiedpatents.com/litigation/caselist), filtering exactly on patent number 5,790,522 and excluding the similar numbers I encountered.

If you can share a specific litigation-driven dataset or docket source you want me to prioritize (e.g., a particular district's records), I can narrow further — but on the record available here, the answer is: no known litigation.

PTAB / AIA Trial Landscape — US 5,790,522

Proceedings overview

Total AIA trial proceedings on file: ZERO. The structured "PTAB proceedings on file" block (USPTO Open Data Portal) returns no IPR, PGR, or CBM for US 5,790,522, and independent web searches on 2026-09-28 surfaced no petition, institution decision, Final Written Decision, or PTAB-appeal docket entry bearing this patent number. The breakdown by status is therefore: active — 0; claims invalidated — 0; claims sustained — 0; settled — 0; institution denied — 0. Defensive posture: the patent has never been tested at the Board — it is neither "hardened" nor "killed" by PTAB; it is un-adjudicated. No claim of the patent has been canceled, and no claim has been confirmed either. A defendant today gets no free PTAB win from the record, but also faces no § 315(e) estoppel and no adverse Board claim construction — the whole invalidity fight is still open on a blank slate in district court. The dominant practical fact is not the PTAB history but the calendar: the patent expired 2015-06-23 (recorded status "Expired – Lifetime"), so any live dispute would be damages-only over pre-expiration conduct.

No proceeding entries to list

There are no proceeding numbers to report. I will not manufacture any. For completeness, the closest things to "PTAB-adjacent" activity that searches turned up are all false positives and are flagged here so they are not mistaken for this patent's trial history:

Verification path a practitioner should use given I cannot query the ODP API directly: PTAB E2E / PTAB Center at https://ptacts.uspto.gov/ptabweb/ (search by patent number and by application 08/494,135), and CourtListener's docket search at https://www.courtlistener.com/?q=%225790522%22 for any Federal Circuit appeal.

Strategic summary

Claim status: all 8 claims UNTESTED. Independent claims 1, 5, 6 and dependent claims 2, 3, 4, 7, 8 stand exactly as granted on 1998-08-04. Nothing has been canceled by the Board, nothing has been confirmed by the Board, and no patentable-weight finding exists to cite. Anyone characterizing this patent as "survived IPRs" would be overstating the record — it has never been in an IPR at all. Conversely, anyone treating it as weak because it was never challenged should recall that an un-challenged patent retains the full pre-AIA § 282 presumption of validity and has had zero claim-construction exposure in an AIA forum.

Estoppel landscape: essentially virgin territory. Because no IPR/PGR/CBM was ever instituted, 35 U.S.C. § 315(e)(2) estoppel does not attach to any party — no petitioner is barred, no privy is barred, and no "reasonably could have raised" ground has been foreclosed. There is also no IPR certificate to point at and no Board-issued claim construction under Phillips to influence the district court. Every § 102/§ 103 ground — including the six examiner-cited references (US 5,268,900 Hluchyj; US 5,475,682 Choudhury; US 5,550,823 Irie; US 5,570,348 Holden; WO 93/20637 Stratacom; EP 0609114 Thomson-CSF) and the non-patent literature on ATM input/output buffering and ON-OFF source shaping — remains available without an estoppel cloud. On the other side, a CBM route is effectively foreclosed for the future: CBM review under AIA § 18 was limited to patents claiming a "financial product or service," and this patent claims packet-switch congestion control; § 18(a)(1)(B)'s "technological invention" exclusion would almost certainly have applied, and the CBM program sunset on 2020-09-16 in any event.

Pattern signals: none. No petitioner appears twice (no petitioner appears at all); no defensive aggregator (e.g., Unified Patents, RPX) has a filing on this number; the patent owner (Cisco Technology, Inc., via the IBM → Cisco Systems → Cisco Technology chain completed in 2000) has never pursued a PTAB appeal on this patent because it has never had a Board decision to appeal. That silence is itself informative: 5,790,522 appears never to have been asserted in a campaign. A patent this heavily cited (127 third-party "cited by" entries spanning Cisco, Ericsson, Nokia, Lucent, AT&T, Avaya, and Mellanox families) that nonetheless attracted no IPR over a 17-year post-AIA window is consistent with a patent that was never worth an accused infringer's $100k+ petition — a supply-side rather than merits-side explanation.

One nuance on timing, stated carefully: expiration does not itself bar an IPR petition — the Board has accepted petitions against expired patents (claims are construed under the Phillips framework on the preponderance standard, and the Board issues FWDs on expired claims). So the absence of an IPR on 5,790,522 is not explained by expiration. If an IPR were filed today it would be theoretically available, but it would be a low-value exercise against an expired patent that can no longer be asserted for prospective relief.

Recommended next steps

1. If you are a defendant facing an assertion of 5,790,522: treat the absence of PTAB history as no shortcut and no handicap. There is no FWD to quote and no canceled claim to lean on; I cannot give you a disposition to link because none exists. Your invalidity case must be built from scratch under § 282 in district court, and the first-line threshold question is whether any asserted act post-dates 2015-06-23, the recorded expiration date — if not, damages exposure is time-barred.
2. Do not file an IPR reflexively. Given expiration and the absence of any track record of assertion, an IPR would likely be a net cost with no § 315(e) or stay benefit; and because no prior IPR exists, there is no estoppel windfall to capture.
3. Verify before relying on this page. The ODP-returned list is empty and web search corroborates it, but I could not query ODP or PTAB E2E live. Re-run the patent number and application number (08/494,135) through PTAB E2E (https://ptacts.uspto.gov/ptabweb/), and check the CAFC docket and CourtListener for any appeal bearing this number, before memorializing "no PTAB activity" in a brief or an opinion.
4. Cite the file you have, not one you wish you had. The strongest documented facts about this patent's defensive posture remain bibliographic and claim-level — 8 claims with 3 independents, the backpressure override recited in the specification but absent from the granted claim scope, and the 1998-08-04 grant with a 2015-06-23 expiration — not any Board outcome.

Uncertainty disclosure: I am reporting the absence of proceedings as a faithful reflection of the structured ODP block plus independent searches; that is evidence of absence, not proof of it. I have deliberately declined to name any proceeding number for this patent, because naming one would require fabricating it.

I'll research the USPTO assignment record for this patent before writing anything.

I could not retrieve reel/frame numbers or correspondent data — see the note in the Assignment timeline section. Here is the reconstruction on the record available.

Inventors

All seven named inventors were IBM employees at the time of filing, based on their recorded residences, which track IBM's routing/switching development sites:

Employer attribution is my inference from residence geography, not a verified personnel record — the grant text does not state employers.

Unusual-pattern check:

• No evidence of inventors departing the original assignee within 12 months of filing. The earliest inventor-side assignment is dated 1995-08-22, i.e. ~2 months after the 1995-06-23 filing, which is normal administrative practice (assignment being recorded shortly after filing), not a defection signal.
• The relevant labour event is institutional, not individual: IBM wound down the Networking Hardware Division from 1999 onward and executed the 1999 asset sale to Cisco. That is a division-level divestiture, which is a different and much weaker NPE precursor than an inventor walk-out.
• Inventors are geographically clustered (six of seven in the Alpes-Maritimes, France), consistent with a single captive R&D lab rather than a distributed consortium — again a normal IBM pattern.

Original assignee

International Business Machines Corporation (Armonk, NY) — the entity named on the issued patent, per the 1995-08-22 assignment of inventors' rights to "IBM CORPORATION" in the Google Patents legal-events record.

• Products embodying the claims: Yes, in substance. The patent is directed at priority-based input queuing, a "spacing" throttle into the switch fabric, and backpressure override in a multiport ATM/variable-length switch — i.e. the data path of IBM's Networking Hardware Division (NHD) switch and router line, which the specification's own framing (multimedia, ATM cell switching, reserved-bandwidth connection set-up) reflects. This is a core-technology patent for a shipping product family, not a paper patent.
• Primary line of business at filing: Diversified IT — mainframes, software, services, and (then) a captive routing/switching hardware business. Networking was a small slice: roughly $1B of IBM's $81.7B revenue in the prior year per analyst commentary in the 1999 coverage.
• Current status: Operating. IBM has never been in bankruptcy; there is no Chapter 7/11 event anywhere near this asset. IBM exited the relevant product line by agreement with Cisco rather than through insolvency.

Note on the family: the priority application EP 94480097 / EP0706297A1 is recorded as not_active – Withdrawn. The EP counterpart never granted; the US patent is the only member that issued.

Assignment timeline

Critical sourcing limitation — read this before relying on the below. The USPTO Assignment Center index (https://assignmentcenter.uspto.gov/, mirrored at https://assignment.uspto.gov/patent/index.html) exposes reel/frame numbers and the recorded correspondent (the filing attorney of record). I was not able to retrieve the reel/frame numbers or correspondent names for this patent in this session; my queries returned the Google Patents legal-events digest and third-party mirrors, which record only the event date, assignor and assignee, and I do not have a working direct query against the Assignment Center. I am therefore reporting the three recorded events without reel/frame identifiers rather than inventing them. The anchor for each entry is the Google Patents legal-events record, cross-checked against the party names in https://patents.justia.com/patent/5790522.

• 1995-08-22 (executed) / recorded 1995-08-22 — Reel NOT RETRIEVED

  • Conveyance: Assignment (inventors → employer)
  • Assignor: Iliadis, Ilias; Fichou, Aline; Galand, Claude; Jacquart, Xavier; Louis, Philippe; Spagnol, Victor; Suffern, Edward (as listed in the assignment record)
  • Assignee: IBM CORPORATION
  • Correspondent: not retrieved
  • Context: routine pre-issuance inventor-to-employer assignment; no commercial transfer of the asset.

• 2000-06-14 (executed/recorded) — Reel NOT RETRIEVED

  • Conveyance: Assignment
  • Assignor: INTERNATIONAL BUSINESS MACHINES CORPORATION
  • Assignee: CISCO SYSTEMS, INC. (a California corporation)
  • Correspondent: not retrieved
  • Context: strategic divestiture of a business line — not a fire-sale. This is the closing of the IBM/Cisco alliance announced 1999-08-31 (https://newsroom.cisco.com/c/r/newsroom/en/us/a/y1999/m08/cisco-and-ibm-announce-technology-networking-and-strategic-services-alliance.html), under which Cisco acquired IBM's routing/switching IP. The transaction is independently corroborated by two antitrust filings: the Greek Competition Commission, Decision 103/1999 (10 Dec 1999), which describes a contract dated 1999-08-30 between Cisco Systems Inc. and IBM for the purchase of patents and IP in routing and switching products, and the Turkish Competition Authority, Decision 00-16/160-82 (2 May 2000), which states the transfer covered 144 US patents and 58 pending US applications. US DOJ/FTC clearance was reported 1999-12-08.

• 2000-04-27 (executed/recorded) — Reel NOT RETRIEVED

  • Conveyance: Assignment
  • Assignor: CISCO SYSTEMS, INC. (a California corporation)
  • Assignee: CISCO TECHNOLOGY, INC., a Corporation of California
  • Correspondent: not retrieved
  • Context: internal corporate reorganisation / intra-group IP consolidation. Cisco Technology, Inc. is the Cisco group entity that holds and enforces Cisco's patent estate; the transfer is not a change in ultimate control.

Ordering anomaly — flagged, not auto-corrected. The Google Patents legal-events list shows the Cisco Systems → Cisco Technology step dated 2000-04-27 and the IBM → Cisco Systems step dated 2000-06-14, i.e. the downstream intra-group transfer appears dated earlier than the upstream acquisition. This is only resolvable against the underlying reel/frame records and execution dates, which I could not retrieve. The commercially necessary sequence is IBM → Cisco Systems → Cisco Technology.

No other assignments exist in the chain. There is no post-2000 assignment, no security agreement, no license recorded, and no transfer to any third party. The chain terminates at Cisco Technology, Inc.

Timeline diagram

timeline
    title Ownership of US 5790522
    1994 : EP priority application filed
    1995 : US application filed
         : Inventors assign to IBM
    1998 : Patent issued to IBM
    1999 : IBM Cisco alliance announced
         : DOJ and FTC clearance
    2000 : IBM assigns to Cisco Systems
         : Cisco Systems assigns to Cisco Tech
    2015 : Patent expires

NPE / troll-pattern signals

Verdict

Operating-company assertion — with an explicit caveat on the "assertion" prong.

Justification: Every recorded link in the chain is an operating-company transaction. The patent moved from IBM (original assignee, granted 1998-08-04, inventor assignment recorded 1995-08-22) to Cisco Systems, Inc. (recorded 2000-06-14) and then to Cisco Technology, Inc. (recorded 2000-04-27) as part of one announced 1999 corporate divestiture — the two antitrust clearances (Greek Decision 103/1999, 10 Dec 1999; Turkish Decision 00-16/160-82, 2 May 2000) confirm the transaction covered 144 US patents and 58 pending applications of IBM routing/switching IP, and the price was a reported ~$300M, i.e. a premium, not a distressed, valuation. No NPE signal is present on any of the eight tests, the chain terminates at a Cisco group operating entity that ships switches and routers embodying the claimed priority-queuing and backpressure mechanisms, and the patent expired 2015-06-23 with no successor assignment.

Caveat, stated plainly: the "Operating-company assertion" branch of the rubric requires the current assignee to be suing actual competitors. I found no litigation naming US 5,790,522, so the assertion element is not evidenced — the correct reading is "operating-company ownership with no demonstrated assertion activity," and I am selecting this bucket only because the other three (NPE high/moderate, defensive aggregator, insufficient data) are affirmatively excluded. I did not retrieve reel/frame numbers or correspondent names, so signal 3 is unresolved rather than cleared.

Verify directly at: https://assignmentcenter.uspto.gov/ (patent-number lookup) and https://assignment.uspto.gov/patent/index.html — the reel/frame, execution dates and the correspondent of record for the three events above are retrievable there and would close the one open gap in this analysis.

I'll research the prior art references for US 5,790,522, starting with the examiner-cited references.

Let me research the remaining examiner-cited references.

Prior-Art Analysis — US 5,790,522 (Fichou et al.)

Scope and method note

This analysis builds on the verified record already established above (bibliographic data, claim set, assignee chain) and does not repeat it. Two process disclosures:

1. I could not query USPTO PatentCenter or the examiner's file wrapper directly in this session. The citation data below comes from the authoritative grant text supplied in the task (Google Patents, https://patents.google.com/patent/US5790522/en) cross-checked against independent mirrors (uspto.report, everypatent.com, EPO publication PDFs). Where I could retrieve a cited reference's own full text I did so; where I could not, I say so explicitly.
2. I did not substitute any near-miss number. Every reference below is one of the six (6) references actually listed in the "Patent Citations (6)" examiner-cited table of US 5,790,522, plus the three Non-Patent Citations. The 127 "Cited By" entries are later documents and therefore are not §102 prior art against this patent; I have not treated them as such.

Two date conventions matter here (pre-AIA applies; effective filing 1995-06-23, priority 1994-10-07):

• §102(a)/(b) critical date for a statutory bar (publication) = 1994-06-23 (one year before the US filing date; foreign priority under §119 does not remove a §102(b) bar).
• §102(e) date = the US filing date of a reference patent granted on an application filed before the 5,790,522 filing date.

The six examiner-cited references — summary table

Note a discrepancy to flag literally: Google Patents lists US 5,570,348 with a priority date of 1994-04-28, while its own front-page data shows Appl. No. 439,078 filed 1995-05-11 (the 1994-04-28 date belongs to related US 5,583,861, filed Apr. 28, 1994). I report both; for §102(e) the controlling US filing date is 1995-05-11.

Per-reference detail

1. US 5,268,900 A — Hluchyj & Bhargava (Codex Corporation)

• Full citation: US 5,268,900 A, "Device and method for implementing queueing disciplines at high speeds," Michael G. Hluchyj (Wellesley, MA) and Amit Bhargava (Somerville, MA), assignee Codex Corporation (Mansfield, MA). Appl. No. 726,065, filed 1991-07-05, issued 1993-12-07; 33 claims. Primary Examiner Olms.
• Disclosure: A high-rate queueing discipline for an integrated fast-packet network carrying several traffic classes (CBR, voice, framed data). Uses per-class prioritizers (head-of-line priority, packet discarders) feeding a precomputed scan-table dequeuer implementing weighted round-robin bandwidth allocation. Priority/discard decisions are made by comparing queue length against a per-class watermark.
• §102 mapping: Discloses the structural preamble elements of claim 1 and claim 6 — multiple traffic classes enqueued by priority and a prioritized dequeue discipline. It does not disclose the claim-defining limitation: a "spacing function" that holds the receive-adapter-to-fabric transfer rate below the fabric's predetermined rate and that is disabled on detection of a predetermined (real-time) priority. It also lacks the switch-fabric "predetermined transfer rate" framing. Assessment: does not anticipate claims 1, 5, 6, 7, or 8 as a single reference. Best characterized as §103 background on priority queuing/scheduling. (Source: https://patents.google.com/patent/US5268900A; http://www.everypatent.com/comp/pat5268900.html.)

2. WO 93/20637 A1 — Stratacom, Inc. (Bustini, Daley, Corballs)

• Full citation: WO 93/20637 A1, "Congestion control for cell networks," Stratacom, Inc. (San Jose, CA), PCT filed 1992-04-01, published 1993-10-14; US counterpart US 5,313,454 A (issued 1994-05-17).
• Disclosure: A feedback congestion-control system. Intermediate nodes monitor buffer queue lengths and set an "incipient congestion indicator"; the destination node interprets it and returns a 2-bit rate-control signal to the source node, which regulates its bursty-data transmission rate (additive increase / multiplicative decrease between a guaranteed-minimum and a maximum rate). The background expressly describes a "spacer that introduces a suitable delay" for peak-rate control, token-bucket/leaky-bucket rate controllers, and threshold-based cell discard (CLP/DE bit).
• §102 mapping: This is the conceptually closest of the six to the "spacing" idea, because it teaches (a) deliberately throttling bursty (delay-insensitive) traffic below available capacity and (b) a spacer to limit the transfer rate. However, its rate throttling is driven by network-feedback congestion signals at the source, not by a receive-adapter spacing function that is automatically disabled when a predetermined high-priority (RT) packet is detected at the input. It therefore appears to lack the claimed trigger ("disabling the spacing function upon detection of … packets having the predetermined priority level"). Assessment: does not anticipate independent claims 1, 5, or 6 as a single reference (an anticipation rejection requires disclosure of every element, and the high-priority-detection override is missing). It is, however, strong §103 art on the rate-limiting/spacer element. Published 1993-10-14 — a §102(b) statutory bar. (Source: https://patents.google.com/patent/WO1993020637A1; https://www.freepatentsonline.com/5313454.html.)

3. EP 0 609 114 A1 — Thomson-CSF

• Full citation: EP 0 609 114 A1 (priority 1993-01-22), "Method and device for bit rate management in an ATM network" (Procédé et dispositif de gestion de débit dans un réseau ATM), applicant Thomson-CSF; published 1994-08-03.
• Disclosure: I was not able to retrieve the full text or the search-report passage mapping for this reference in this session (my queries returned the Google Patents citation entry but not the EP document body). Based on the title and the CPC placement, it concerns ATM bit-rate (rate) management — i.e., a rate-control/spacing-type disclosure.
• §102 mapping (hedged): If, as its title indicates, it discloses holding a transfer/bit rate at a managed value in an ATM node, it would be relevant art against the "transfer at a rate lower than the predetermined rate" element. It does not, on the face of the available metadata, disclose the priority-triggered disabling of that rate management. Because it published 1994-08-03 (before the 1994-10-07 priority date but after the 1994-06-23 §102(b) critical date), it would be §102(a) art only, not a §102(b) bar. Assessment: I cannot responsibly state that it anticipates any claim without the text; flag as unverified. I recommend pulling the EP/US family document (Thomson-CSF) before relying on it. (Source: Google Patents citation table for US 5,790,522.)

4. US 5,550,823 A — Irie & Yamada (NEC Corporation)

• Full citation: US 5,550,823 A, "Method and apparatus for performing priority control for cells in output buffer type ATM switch," Yasuhito Irie and Kenji Yamada, assignee NEC Corporation (Tokyo). Appl. No. 430,385, filed 1995-04-28 (JP priority 1994-04-28, JP 6-111819), issued 1996-08-27. EP counterpart EP 0 681 385 A2 (published 1995-11-08).
• Disclosure: Adds a loss quality class and a delay quality class to each ATM cell; virtually sets logical queues by delay class and routing info; changes (transitions) a queue's delay quality class up or down depending on the cell storage amount relative to a threshold ("cell storage threshold Vn"), and reads cells from the queue having the uppermost delay class. An output-buffer "threshold exceeding signal" can force a queue to the lowest (read-inhibited) class.
• §102 mapping: Relevant to the threshold-controlled spacing of 5,790,522's claims 4 and 8 in that it senses buffer/storage occupancy against a threshold and changes forwarding behavior accordingly. But its control variable is the read priority class of queues, not the rate at which a receive adapter drives the switch fabric, and it has no spacing function disabled on RT detection. Assessment: does not anticipate claims 1, 5, or 6; potential §103 art against the threshold elements of claims 4 and 8 (but note the opposite polarity — threshold exceedance disables spacing in 5,790,522 vs. downgrades priority here). §102(e) art as of its 1995-04-28 US filing. (Source: https://patents.google.com/patent/US5550823; http://www.everypatent.com/comp/pat5550823.html.)

5. US 5,570,348 A — Holden (Integrated Telecom Technology, Inc.)

• Full citation: US 5,570,348 A, "Method and apparatus for enqueueing data cells in an ATM switch fabric architecture," Brian D. Holden (Sunnyvale, CA), assignee Integrated Telecom Technology, Inc. (Gaithersburg, MD). Appl. No. 439,078, filed 1995-05-11, issued 1996-10-29. (Google additionally lists a 1994-04-28 priority; see note above.)
• Disclosure: A switch-fabric ATM architecture with a shared cell-memory pool. Independent claims recite generating back-pressure to a plurality of inputs and a plurality of priorities: a cell-count indicator is compared to a predetermined threshold, and upon a positive indication a back-pressure signal associated with one input and one priority level is asserted. A marked-interrupt linked list flags congested virtual channels.
• §102 mapping: Directly relevant to the back-pressure and per-priority queue-count-vs-threshold aspects referenced in the 5,790,522 specification (the BP signal and the NO_RT_Level counter). It does not disclose a spacing function, a receive-adapter-to-fabric transfer-rate reduction, or the high-priority-detection override that disables spacing. Assessment: does not anticipate claims 1, 5, 6, or 8 as a single reference; §103 art on the per-priority back-pressure/threshold element. §102(e) art as of 1995-05-11. (Sources: https://patents.google.com/patent/US5570348; http://www.everypatent.com/comp/pat5570348.html.)

6. US 5,475,682 A — Choudhury & Hahne (AT&T Corp.)

• Full citation: US 5,475,682 A, "Method of regulating backpressure traffic in a packet switched network," Abhijit Kumar Choudhury and Ellen Louise Hahne, assignee AT&T Corp. Appl. No. 259,261, filed 1994-06-10, issued 1995-12-12. EP counterpart EP 0 687 091 A2/B1.
• Disclosure: A downstream switching element with a congested local buffer sends a back-pressure signal to the upstream element, which queues data destined downstream. A predetermined occupancy threshold is set in the upstream element; when the upstream buffer occupancy exceeds the threshold, the upstream element ignores the back-pressure signal and transmits the queued data anyway. Also couples this with intrastage buffer-management (pushout/allocation/limit) schemes.
• §102 mapping: This is the most structurally resonant of the six for the threshold-override concept (see 5,790,522 claims 4 and 8): both compare a buffer/queue occupancy against a stored threshold and change transfer behavior when the threshold is crossed, and both involve a back-pressure signal. But the direction and trigger differ decisively — in Choudhury, threshold exceedance causes the upstream node to ignore back-pressure and release data; in 5,790,522, buffer occupancy crossing a threshold causes spacing to be disabled so that packets are transferred at the full rate, and separately, an RT/BP condition overrides spacing. Choudhury does not disclose a "spacing function" nor priority-based rate selection. Assessment: does not anticipate any claim as a single reference; relevant §103 art against the threshold-and-override structure of claims 4 and 8. §102(e) art as of its 1994-06-10 US filing (note: filed just 13 days before the 1994-06-23 §102(b) critical date, so it is not a §102(b) bar); EP 0 687 091 published 1995-12-13, after the priority date. (Sources: https://patents.google.com/patent/US5475682A; https://uspto.report/patent/grant/5475682.)

Non-patent literature (examiner-cited)

These three are printed publications and are all §102(b) art (published more than one year before the 1995-06-23 US filing, and before the 1994-10-07 priority date). They are, notably, the references whose subject matter most overlaps the "spacing / rate control" concept:

1. H. Badran et al., "ATM switch architecture with input-output buffering: effect of input traffic correlation, contention resolution policies, buffer allocation strategies and delay in backpressure signal," Computer Networks and ISDN Systems, vol. 26, No. 9, May 1994, pp. 1187–1213 (XP-445890). Directly addresses delay in the backpressure signal and buffer-allocation strategies in input-output-buffered ATM switches — relevant to the back-pressure and buffer-threshold limitations, not to a spacing function.
2. H. Inai et al., "Analysis of ON-OFF Source Shaping for ATM Multiplexing," IEEE INFOCOM '93, vol. 3, 1993-03-28, San Francisco, pp. 1330–1336 (XP-336076). Source shaping — i.e., deliberate rate limiting of bursty sources, conceptually the "spacing" idea, but applied at the source, not as a switch-adapter function disabled by RT detection.
3. H. Inai et al., "Rate-based Congestion Control in High-Speed Packet-Switching Networks," IEICE Transactions, vol. E75-B, No. 11, Nov. 1992, Tokyo, pp. 1199–1207. Rate-based congestion control — relevant background on transfer-rate regulation.

§102 assessment for the NPL: None of the three, on the titles/abstracts available and their described scope, discloses the combination of (i) receive-adapter priority queues, (ii) a default spacing function reducing the adapter→fabric rate, and (iii) disabling spacing upon detecting a predetermined high-priority packet. They are best treated as §102(b) art on the rate-limiting backdrop and as §103 combination candidates.

Family member that is not prior art

• EP 0 706 297 A1 (priority 1994-10-07, from EP 94480097; status withdrawn) is the European counterpart of this same invention, not prior art against US 5,790,522.

Bottom line

• No single one of the six examiner-cited references appears to anticipate independent claim 1, 5, or 6. Anticipation under §102 requires that one reference disclose every claimed element, including the spacing-then-disable-on-high-priority mechanism, and none of these six does.
• The strongest §102 candidates on the "spacing/rate-control" element are WO 93/20637 (Stratacom) and EP 0 609 114 (Thomson-CSF), with the Inai NPL as corroborating printed publications — but each throttles rate for different reasons/at a different point in the network and lacks the claimed high-priority-detection disable.
• The strongest §102 candidates on the threshold-and-override element are US 5,475,682 (Choudhury/AT&T) and US 5,550,823 (Irie/NEC), with US 5,570,348 (Holden) on per-priority back-pressure — again without the spacing-function and RT-override limitations.
• US 5,268,900 (Hluchyj/Codex) is background on multi-priority queuing/scheduling and does not reach the claim-defining spacing limitation.
• Most probable use of this art set: as §103 combination art (e.g., Stratacom or Inai rate-spacing in view of a QoS-priority scheme such as Hluchyj or Irie) rather than as §102 anticipatory art.

Uncertainty disclosures: I verified references 1, 2, 4, 5, and 6 against their own patent texts. Reference 3 (EP 0 609 114) I could not retrieve in full — treat its §102 mapping as unverified. I did not directly access USPTO PatentCenter in this session, so the examiner's precise rejection rationale (which claims each reference was applied against) is inferred from the granted claim language, not read from the file wrapper. A definitive anticipation/obviousness opinion should be confirmed against the USPTO file history and the EP 0 609 114 document itself.

I'll ground this analysis in the prior-art references actually listed on the patent page, and try to verify what those references disclose.

Good material. Let me verify the remaining examiner-cited references.

Obviousness Analysis — US 5,790,522 under 35 U.S.C. § 103

Scope note. This builds on the prior sections (bibliographic data, claim summary, no-ligation finding) without repeating them. The prior art used here is exactly the set listed in the "Prior Art" / "Patent Citations" and "Non-Patent Citations" sections of the record supplied — six patent documents and three distinct non-patent works. The later "Cited By" / "Families Citing" documents are not prior art to the '522 patent (they post-date it) and are not relied on as such.

1. Procedural framework

• Governing law. The '522 patent has an effective filing date of 1995-06-23 (priority 1994-10-07), so pre-AIA § 103 applies. The Graham v. John Deere factors (scope/content of prior art; differences; PHOSITA level; secondary considerations) control, and KSR Int'l v. Teleflex supplies the legal rationales for combining references. No rigid "teaching, suggestion, or motivation" test survives KSR; the question is whether the claimed subject matter as a whole would have been obvious to a PHOSITA, including "a combination of familiar elements according to known methods [yielding] predictable results."
• Prior-art status of the cited documents (all pre-AIA):

• Record discrepancy (flagged, not corrected): the page labels the non-patent list "Non-Patent Citations (6)," but only three distinct works appear (each printed twice). I treat the three works as the NPL prior art.
• Posture caution. As noted in the prior section, the patent expired 2015-06-23 and no litigation or PTAB record was found. A § 103 analysis is therefore retrospective — i.e., it is relevant only if the patent is asserted for pre-expiration damages, or as an invalidity defense in some collateral proceeding. It is presented as a technical/legal assessment, not as a live challenge.

2. Level of ordinary skill (PHOSITA)

A PHOSITA at the 1994–1995 priority date would hold a bachelor's degree in electrical engineering or computer science (or equivalent) with 2–3 years' experience in packet/cell switching traffic management, and would be familiar with: (i) ATM/fast-packet switch fabrics with shared-memory or output-buffer architectures; (ii) priority and weighted-round-robin queuing disciplines for multiplexing traffic classes; (iii) rate-based congestion control (choke/loosen, explicit-rate, leaky-bucket, spacers); and (iv) backpressure flow control. All six patent references and three NPL works are in the same field of endeavor (USPC 370/…; CPC H04L 12/56 — the same class assigned to the '522 patent), i.e., analogous art as a matter of law.

3. Construction of the key limitations

4. The primary combination

4.1 The references, as verified

• Stratacom (WO 93/20637 / US 5,313,454). A cell-switch congestion-control system that "control[s] the transmission rate of bursty traffic in the presence of high priority, voice, low speed statistical, high speed deterministic and multicast data" and expressly reasons that "bursty traffic is relatively insensitive to delay" so buffer/loss can be traded against rate. It discloses monitoring buffer queue lengths at nodes to generate congestion signals, a 2-bit feedback rate-control code, and — crucially for the "spacing" term — that "peak rate control is accomplished by means of a spacer that introduces a suitable delay proportional to the length of the prior transmitted packet." It also discloses rate increase messages ("loosen"/"increase rate") when congestion abates.
• Hluchyj (US 5,268,900). A high-speed queueing discipline device for a fast-packet switch that buffers packets by traffic class ("groups" per class), applies head-of-line priority (HOLP) across classes and weighted round-robin (WRR) bandwidth allocation via per-group credit counters, and states that "the server examines Q1, Q2, … Qn until a packet is found" for HOLP. The WRR credit counter "decrement[s] … by the number of bytes in the transmitted packet," so it caps each class to a fraction of trunk bandwidth — a per-class rate limit. The reference states the very problem the '522 patent addresses: "a long busy period … could affect the quality of the voice connections because voice packets could be blocked."
• Irie (US 5,550,823). An output-buffer ATM switch with logical queues per delay-quality class, threshold comparisons of cell storage amounts, and a controller that changes a queue's class (raise/lower) based on buffer occupancy, including a read-inhibit state when an output-buffer threshold is exceeded.
• Choudhury (US 5,475,682). Backpressure flow control in which each upstream element stores a backpressure threshold; when its local-buffer occupancy exceeds that threshold, the upstream element ignores the backpressure signal and transmits the queued data downstream (i.e., increases the transfer rate in response to a buffer-threshold/limit condition).
• Inai (1992, rate-based control). Source-node rate control: the source "initiates transmission with a low rate and increases the rate slowly," a choke packet throttles the rate and a loosen packet allows increase of the rate; the paper studies queue-length thresholds for declaring congestion.
• Inai (1993, ON-OFF source shaping); Badran et al.; Thomson-CSF EP 0609114 supply the remaining building blocks explicitly named in the claim vocabulary: shaping of bursty sources, input/output buffering with backpressure delay, and bit-rate management in an ATM network respectively. (Contents of these three inferred from titles/venue; see §9.)

4.2 The combination and the § 103 rejection

Proposed rejection — Claim 1: obvious over Stratacom in view of Hluchyj, further in view of Irie.
Claim 5: obvious over Stratacom in view of Hluchyj (and Inai 1992).
Claim 6: same combination, applied to Hluchyj's claimed device / Irie's output-buffer switch apparatus.
Claims 4 and 8: further in view of Irie and Choudhury.

Element mapping for claim 1:

4.3 Why a PHOSITA would have combined them (KSR rationales)

1. Same field / analogous art. All references address ATM/fast-packet switch traffic management; Hluchyj, Irie, Choudhury, Stratacom and the '522 patent share CPC H04L 12/56 / H04L 2012/5635–5636. Combineable by definition.
2. Known technique to improve a similar device. "Spacing"/rate shaping of delay-tolerant traffic was a known technique (Stratacom spacer; Inai shaping; Inai low-rate start). Applying a known traffic-shaping technique to the known per-class input queues of a switch (Hluchyj) is the paradigm KSR case of "a technique … used to improve one device … applied to improve similar devices in the same way."
3. Predictable result. The combination does exactly what each reference individually promises: it protects delay-sensitive (real-time) traffic from a low-priority "busy period." Hluchyj expressly identifies the blocking problem ("voice packets could be blocked") and Stratacom expressly names the solution (throttle the delay-insensitive class). The result — reducing RT delay/jitter at the expense of delay-tolerant throughput — is predictable.
4. Design incentive / market forces. The '522 specification admits the whole architecture (CPs, equivalent-capacity reservation, Bellman-Ford routing, three-priority scheduling) is known and that the staying problem was switch-fabric contention from large low-priority packets. A PHOSITA facing that admitted problem had a finite, predictable set of options, two of which (throttle the low-priority class; prioritize the RT class) are the two references.
5. Both references suggest the combination explicitly. Hluchyj: HOLP is needed and WRR can allocate bandwidth as fractions of the trunk to each class; Stratacom: rate control should target the bursty/delay-insensitive class. A motivation to combine is literally stated in each.

5. Claim-by-claim § 103 conclusions

Observation on claim 8 / backpressure. The prior section correctly notes that backpressure is in the '522 specification but not in independent claims 1/5/6. That gap does not help validity: Choudhury and Stratacom, both examiner-cited, disclose the backpressure/feedback machinery in the spec, so even the unclaimed BP+timer feature (T1/T2) would be an obvious design detail over Choudhury (backpressure threshold) + Inai (rate-recovery after choke).

6. Counter-arguments a patentee would raise (and responses)

(a) "The claims are counter-intuitive — the art teaches slowing low-priority traffic on congestion, but the claims increase its rate on high-priority detection."
This is the strongest nonobviousness theme; the '522 mechanism speeds up the very traffic that threatens the switch. Response: (i) the "increase" is only up to the switch's own predetermined transfer rate — i.e., removing an artificial, self-imposed throttle, not accelerating beyond capability; (ii) Stratacom and Inai both disclose rate-increase actions ("loosen"/"increase-rate") in response to a sensed condition, so "increase on condition" is known; (iii) the patent's own rationale for the increase (a large NRT/NR packet at a single-user interface blocks the later RT packet until the packet finishes) is a recognized problem in Hluchyj ("voice packets could be blocked"), so the benefit was known and predictable — the definition of KSR obviousness. Weight: this argument has some traction but is unlikely to survive on its own given the express disclosures of both rate-increase and priority-based blocking.

(b) "Rate-based control (Inai/Stratacom) lives at the source node, whereas the claims put spacing in the receive adapter."
Response: Hluchyj's mechanism (WRR credit counters, class queues) is in the switch, and Stratacom's node-level rate control is in the network. Moving a rate limiter to the switch ingress where the contention actually occurs is an obvious architectural choice with predictable benefit; no reference teaches away.

(c) "Teaching away."
I found no reference teaching away from throttling delay-insensitive traffic or from speeding it up when urgent traffic appears. Choudhury in fact teaches increasing flow past a backpressure threshold, which supports the claimed increase-on-condition direction rather than discouraging it.

(d) Secondary considerations.
No evidence in the record of unexpected results, copying, industry praise, or long-felt need tied specifically to the default-on-spacing feature (as opposed to the separate-queue jitter benefit, which the specification attributes to known multiple queuing — see Hluchyj/Irie). Any Cisco commercial-success argument would fail for lack of nexus to the claimed spacing feature. The patent's own "factor of 50" jitter comparison is attributed to three separate priority queues, which is disclosed by Hluchyj/Irie — not to the spacing mechanism.

7. Bottom line

• Every element of claims 1, 2, 3, 4, 6, and 8 is disclosed or suggested by the examiner-cited art. The single most efficient combination is Stratacom (spacer/rate control of delay-insensitive bursty traffic + rate-increase messages) as primary, Hluchyj (per-class queues + HOLP detection + WRR per-class bandwidth cap) for the switch/adapter architecture and the priority-detection element, and Irie / Choudhury for the threshold-triggered rate change of claims 4 and 8.
• Claim 5 is a higher-abstraction restatement of claim 1 and falls to the same combination (with Inai 1992 supplying rate-control motivation).
• Claim 7 ("number of rates = number of priority levels") is a routine design choice over Hluchyj's WRR weights / Stratacom's four-state rate code.
• The only material vulnerability in the rejection is the counter-intuitive direction of the control (speed-up on high-priority detection). It is a legitimate argument but is answerable by (i) the express rate-increase teachings of Stratacom/Inai, (ii) Hluchyj's identification of the priority-blocking problem, and (iii) KSR's "predictable result" rationale. My assessment: claims 1–8 are, more likely than not, obvious over the cited combination, with claim 1 the closest question and claims 3, 4, 7, and 8 the clearest.

8. Materials I verified vs. could not

• Verified by search (contents confirmed): US 5,268,900 (Hluchyj) — claims/abstract/description; US 5,475,682 (Choudhury) — abstract/description; WO 93/20637 / US 5,313,454 (Stratacom) — abstract + claim set + spacer language; US 5,550,823 / EP 0681385 (Irie) — abstract + threshold/class-transition description; Inai 1992 — abstract via IEICE.
• Not independently verified in this session (tool limits reached): the full text of US 5,570,348 (Holden), EP 0609114 A1 (Thomson-CSF), Badran et al., and Inai 1993 (ON-OFF source shaping). My characterizations of those four rest on their titles, venues, and the examiner's citation context and are marked accordingly. None of them is load-bearing for the primary combination in §4 — that combination rests on Stratacom, Hluchyj, Irie, Choudhury and Inai 1992, all of which I verified.
• Legal-status caution (carried over): the patent is Expired – Lifetime (anticipated 2015-06-23), and no CAFC/PTAB/litigation record was found in the prior section. This is an "evidence of absence" statement, not proof; confirm against PACER/CAFC and the PTAB docket before relying on it. All dates and identifiers are reproduced literally from the supplied record and search results, with the one non-patent-citation-count discrepancy flagged in §1.