US 5526414

I'll search for authoritative information on this patent number, including any 2026 CAFC activity.

Let me run a couple of targeted checks for any litigation or 2026 CAFC docket activity.

US 5526414 — Summary

Title: Dynamically controlled routing using virtual nodes

Patent number (as given): US 5,526,414 (grant; application US 08/329,716)

Inventors: François Bédard, Jean Régnier, France Caron

Original assignee: Northern Telecom Ltd. Current listed assignee: RPX Clearinghouse LLC (Google Patents recorded chain: Northern Telecom Ltd → Nortel Networks Corporation → Nortel Networks Limited → Rockstar Bidco, LP → Rockstar Consortium US LP → Constellation Technologies LLC → RPX Clearinghouse LLC)

Filing date: 1994-10-26 · Priority date: 1994-10-26 · Issue/publication date: 1996-06-11

Status: Expired – Lifetime; anticipated expiration 2014-10-26 (per Google Patents). The record shows no live term beyond 2014.

Abstract (verbatim, condensed): A dynamically controlled routing (DCR) telecommunications network of switching elements interconnected by circuit groups, with a network processor connected by data links. Each switching element determines a neighbouring network element for each call by accessing a routing table containing alternate routes to be used if a direct route does not exist or cannot be used; routing tables are updated periodically by the network controller. The network functions as a group of nodes interconnected by links, and routing is on a node-to-node basis. At least one node is a logical entity ("virtual node") that does not necessarily correspond to a single physical network element, but rather to a group of at least one physical component (a network element, part of one, or a plurality of them). A link to the virtual node does not necessarily correspond to a single circuit group; it is the set of direct circuit groups connecting to the virtual node's components. Among the claimed benefits: external final destinations can be associated with a virtual node as an intermediate destination node, so a call may exit the DCR network via any component of the virtual node instead of only one Unique Exit Gateway.

Independent claims (plain language)

The patent has 6 claims, and only claim 1 is independent. Claims 3–6 depend from claim 1 (or 3/5); claim 2 is defective on its face — it recites "A network as claimed in claim 2" (a self-reference), which appears to be a typographical error, but I am reading it literally per your instructions.

• Claim 1 — A telecommunications network made of nodes and links. Nodes include origin nodes (each with a switching element able to route calls), destination nodes, and tandem nodes (which act as both origin and destination). Each link directly joins an origin node and a destination node and contains one or more circuit groups. Each switching element has storage for routing information that includes: (i) a list of destination nodes; (ii) the corresponding link for each destination node where one exists; (iii) for each link, the outgoing circuit group(s); and (iv) for each destination node, a list of zero or more tandem nodes. The network also has means for updating the routing information. Each switching element translates a call's address data to determine a destination node and then (i) tries a direct link if one exists, or (ii) if no link is available, consults its routing table to pick a tandem node and tries that link. The key limitation: the destination-node listing of at least one switching element includes a virtual destination node representing a group of two or more components, each component being a distinct physical network element, with one or more distinct circuit groups associated with each component — and each link from a given origin node to that virtual destination node is a set of circuit groups from that origin's switching element to the two or more components.

• Claims 3 and 5 (dependent) — Specify that the updating means is a network processor communicating with the switching elements over a data communications system, computing alternate routing information from information reported by all switching elements and periodically updating the tandem-node identifications / recommendations (claim 5 adds that the NP updates tandem-node recommendations involving the virtual destination node based on switch-reported information).

• Claims 2, 4, 6 (dependent) — (2) intra-link routing: where the virtual-node link has multiple circuit groups, the storage means holds specified proportions and the switch attempts the circuit groups randomly in dependence on those proportions; (4) and (6) the network processor, when computing alternate-route recommendations, takes into account full availability of each link, including links composed of a plurality of circuit groups.

Note on your CAFC 2026 request

I ran targeted searches for any 2026 (or earlier) Court of Appeals for the Federal Circuit docket activity involving 5526414, including litigation-related searches for the successor assignees (Rockstar/Constellation/RPX) and general Federal Circuit references. I found no CAFC docket entry, appeal, or 2026 litigation activity for this patent, and I could not directly query the CAFC/PACER docket system to confirm a null result. Given the recorded 2014-10-26 expiration, no forward-looking infringement action would appear viable on this record, but I cannot state affirmatively that no litigation or appeal has ever existed. Treat that as an explicit uncertainty rather than a confirmed negative.

Sources

• Full patent text: https://patents.google.com/patent/US5526414/en (retrieved 2026-09-30)
• USPTO/Google patents record including status and prosecution-history events (above URL)
• PDF of granted patent: https://patentimages.storage.googleapis.com/60/28/f6/df69ea5fe831ba/US5526414.pdf
• Justia patent page: https://patents.justia.com/patent/5526414
• Related family member (continuation): US 6,091,720 — https://patents.justia.com/patent/[6091720](/patent/6091720)
• EP family member: EP 0 789 974 B1 (PCT/CA1995/000600)

I'll search for litigation involving US patent 5526414 across patent litigation databases and news sources.

Let me search more targeted litigation databases.

Search Results: Litigation Involving US Patent 5,526,414

Summary finding: I was unable to locate any litigation (district court, CAFC, ITC, or PTAB) in which US Patent 5,526,414 was asserted or challenged as a patent-in-suit. Below is what the searches did and did not establish.

---

What I searched and what I found

I searched patent-litigation aggregators and general web sources, including Unified Patents' litigation portal (portal.unifiedpatents.com), Justia, CourtListener, PlainSite, and news coverage of the relevant patent-holder campaigns (Rockstar Consortium / Constellation Technologies / RPX). Key observations:

1. No case identifies US 5,526,414 as an asserted patent. Search hits for the number "5526414" resolved only to the patent document itself (Google Patents, Justia citations) or to unrelated records (an attorney/assignment record on PlainSite, and foreign company-registration lists where "5526414" appears as an unrelated reference number — e.g., a Lithuanian registry and a Brazilian JUСEC document). None of these are litigation.

2. The likely litigation context — the Rockstar/Nortel campaigns — does not name this patent. US 5,526,414 passed through the Nortel portfolio chain (Northern Telecom → Nortel Networks → Rockstar Bidco, LP (2011) → Rockstar Consortium US LP (2014) → Constellation Technologies LLC (2014) → RPX Clearinghouse LLC (2015)), so it belonged to the same portfolio that produced the well-known Rockstar/Constellation suits. However, the patents actually asserted in those campaigns were different:

   • Rockstar Consortium US LP v. Google Inc., No. 4:13-cv-05933 (N.D. Cal.), and the parallel E.D. Tex. actions against ASUSTeK, HTC, LG, Pantech, Samsung, and ZTE (Nos. 13-0894 through 13-0901) asserted U.S. Patent Nos. 6,765,591; 6,172,973; 5,838,551; 7,236,937; 6,961,558; and 6,560,131 — not 5,526,414.
   • Constellation Technologies LLC v. Time Warner Cable and related cable-industry suits asserted the '649, '389, '048, '879, '917, and '299 patents — not 5,526,414.
   • Cisco's Delaware counterclaim (2014) and the Charter/WOW!/CableONE/Knology/Cequel/Suddenlink Delaware action addressed a set of ~24–28 Rockstar patents — none identified as 5,526,414.

3. No PTAB proceeding (IPR/PGR) referencing US 5,526,414 appeared in Unified Patents' PTAB caselist or in the docket searches. (The PTAB hits returned for "2041"/IPR2020-series cases involved entirely different patents owned by other parties.)

---

Case-by-case table

I cannot populate a row here without fabricating a case, which the operating rules forbid.

---

Important caveats on this conclusion

• Negative search results are not proof of no litigation. My search tools surface web-indexed and public-aggregator content; they may miss cases that (a) settled before a public docket entry naming the patent, (b) were filed in venues or formats not well indexed, or (c) are older paper-era filings with limited online records.
• The patent is expired. Per the Google Patents record, US 5,526,414 had an anticipated expiration of 2014-10-26 and is now marked "Expired – Lifetime." Its family member (the continuation US 6,091,720) is separately noted in the record. An expired patent can still be the subject of past-infringement litigation, but the practical window for assertion closed around 2014.
• Verify directly before relying on this answer. For a definitive litigation history, I would recommend querying:
  • Lex Machina or Docket Navigator (patent-level litigation databases),
  • Unified Patents Portal — https://portal.unifiedpatents.com/litigation/caselist (filter by patent number 5526414),
  • PACER (all district courts, searched by patent number),
  • USPTO PTAB docket search,
  • RPX Insight (which, given RPX Clearinghouse's ownership of the patent, may show defensive or portfolio activity).

If you can tell me a jurisdiction or party you suspect (e.g., a specific cable operator or equipment vendor), I can run a narrower search. I should also note explicitly: I do not know with high confidence whether any non-public or settlement-only assertion of this specific patent exists — I can only report that nothing surfaced in the public sources I searched.

I'll verify the ODP-sourced list against public records before writing anything up.

Let me check PTAB dockets directly and probe the litigation/assertion history.

Proceedings overview

Zero AIA trial proceedings are on file against US 5,526,414. The USPTO Open Data Portal returns no IPR, PGR, or CBM proceeding for this patent, and my independent searches of PTAB dockets, Docket Alarm, and PTAB decision repositories turned up no petition, institution decision, or Final Written Decision naming it. Breakdown: 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denied. The bottom-line defensive posture is unusual and, for a defendant, better than any IPR outcome: the patent expired on 2014-10-26 and every one of its six claims is UNTESTED and UNCHALLENGED at the PTAB — the absence of PTAB activity here is not a sign of a hardened patent but of a dead one.

---

Proceedings on file

None. There is no proceeding to write up. The structured USPTO ODP block in the prompt is authoritative and returns an empty set, and nothing in the public record contradicts it. For completeness, here is what I checked and what I found instead:

What did surface are only ordinary third-party citations of the patent as prior art — e.g., the PCT search report for WO2000013400A3 lists "US 5526414 A (FRANCOIS BEDARD ET AL), 11 June 1996" as a category-"A" (background art) reference, and Justia's reference list for US 10,491,748 cites it. Neither is a validity challenge.

I also could not confirm that 5,526,414 was ever asserted in the Rockstar/Constellation campaigns against cable MSOs. The asserted-patent lists I retrieved from those D. Del. pleadings enumerate the '474, '862, '197, '990, '649, '893, '397, '253, '389, '048, '879, '917, '299, and '999 patents — 5,526,414 is not among them. If a defendant is receiving a demand letter citing this patent, that is a material irregularity worth challenging directly.

---

Strategic summary

Claim status. All six claims — independent claim 1 plus dependents 2–6 — are UNTESTED at the PTAB and SUSTAINED only in the trivial sense that no one has ever challenged them there. No claim has been canceled, disclaimed, or narrowed by any AIA proceeding. Exposure risk instead comes from the term, not the claims: Google Patents records the application as filed 1994-10-26 and lists "Anticipated expiration" as 2014-10-26, with legal status "Expired - Lifetime." Every claim lapsed on that date. The continuation in the family, US 6,091,720 (from application US08/817,786, filed 1995-10-26 under PCT/CA1995/000600), takes its § 120 benefit from the same 1994-10-26 priority date and is likewise expired. Caveat, stated plainly: the 2014-10-26 date is an anticipated expiration of the 20-year term. I have not verified whether any patent term adjustment under 35 U.S.C. § 154(b) or a certificate of correction extended it, and I cannot rule out a modest PTA extension without the file wrapper. Any defendant should pull the face of the printed patent and the reexamination/certificate record before relying on the expiration date. A second document-integrity flag: claim 2 as printed reads "A network as claimed in claim 2" — a self-referential dependency that is almost certainly a typographical error for claim 1, but I have not confirmed a certificate of correction, and any invalidity or infringement theory that leans on claim 2 must account for it.

Estoppel landscape. There is no § 315(e) estoppel to speak of, because there has been no IPR/PGR petitioner. No party is barred from raising any ground. A defendant today could theoretically file an IPR on any § 102/§ 103 art it liked. In practice that right is worthless: the patent is expired, so a defendant's real exposure is back damages, and 35 U.S.C. § 286 bars recovery for infringement more than six years before the complaint is filed. A complaint filed on 2026-09-30 reaches back only to 2020-09-30 — entirely after the 2014-10-26 expiration. That arithmetic, not the PTAB, is the defense.

Pattern signals. No repeat-petitioner pattern exists (there are no petitioners). No patent owner PTAB appeal exists. There is a notable ownership signal: the chain runs Northern Telecom Limited → Nortel Networks → Rockstar Bidco, LP (2011-10-28) → Rockstar Consortium US LP (2014-01-31) → Constellation Technologies LLC (2014-02-05) → RPX Clearinghouse LLC (2015-02-09). RPX is a defensive aggregator, and the assignment swept in Bockstar, Constellation, MobileStar, NetStar, and Rockstar Consortium entities — consistent with RPX's 2015 acquisition of the Constellation/Nortel assertion vehicles. A defensive aggregator holding an expired 1994-vintage routing patent is a strong signal that this asset is inert. The absence of PTAB activity is therefore not the usual "well-asserted patent eventually attracts IPRs" signal — patents of this vintage that were never asserted through trial simply never get challenged.

---

Recommended next steps

1. Establish the expiration date conclusively before anything else. Pull the front page of US 5,526,414, the file wrapper, and the USPTO patent term adjustment record. Confirm whether the term ran to 2014-10-26 or was extended by PTA. Everything below depends on that date.
2. Run the § 286 arithmetic. If expiration is confirmed at 2014-10-26, a complaint filed today can reach no pre-expiration acts, and no damages are recoverable. Demand a damages model with dates. Section 286 is a hard statutory bar, not an equitable one.
3. If the demand letter cites specific claims, call it out. The letter likely cites claim 1 or claim 3/5 (the network-processor claims). If it cites claim 2, note the self-referential "as claimed in claim 2" dependency and ask whether a certificate of correction exists — an uncorrected dependency defect is itself a vulnerability.
4. No IPR is warranted, and none should be filed. Filing an IPR on an expired patent buys nothing: the Board cannot cancel a claim to provide prospective relief, and the § 286 bar already does the work. An IPR here would be cost without benefit, and could even revive interest in the asset.
5. Do not assume the same for siblings. The '720 continuation shares the family but is a separate patent with separate claims; if it is being asserted, evaluate it on its own terms rather than treating this family as uniformly dead.
6. If you want the emptiness on the record, the authoritative sources are PTAB E2E and the PTAB Decisions page at USPTO; for the litigation history discussed above, CourtListener and the D. Del. Rockstar/Constellation pleadings (e.g., Dkt. in gov.uscourts.deb.115708). The patent itself is at patents.google.com/patent/US5526414/en.

Confidence note: I am highly confident there is no AIA trial proceeding involving this patent — the ODP block is empty and multiple independent searches corroborate. I am highly confident about the 1994-10-26 filing and 1996-06-11 grant dates. I am not fully confident that 2014-10-26 is the operative legal expiration date to the day, because I have not inspected the file wrapper for patent term adjustment or terminal disclaimers; treat that date as well-supported but verify it before relying on it in a filing.

I'll reconstruct the assignment record. Let me first verify the recorded assignments and try to retrieve reel/frame and correspondent data.

Let me try to locate the specific assignment records and correspondents.

Good — I found correspondent and some reel/frame leads. Let me dig deeper for the full chain-of-title reel/frame numbers.

Assignment & Ownership Analysis — US 5,526,414

Data-quality preface. The USPTO Assignment Center / assignment.uspto.gov record for this patent could not be opened during this session (the interface is not directly queryable here, and my search budget was exhausted). The chain below is therefore reconstructed from (a) the Google Patents legal-events record for US 5,526,414 (authoritative text supplied in this analysis), (b) recording documents surfaced in PTAB filings for sibling Rockstar/Nortel patents, (c) SEC filings by RPX Corporation, and (d) an attorney-of-record index. Reel/frame numbers are given only where I actually observed them, and are flagged when they come from a sibling patent in the same bulk recording rather than from US 5,526,414 itself. I have not fabricated any reel/frame, correspondent, or date.

---

Inventors

All three are named on the face of the patent and all three appear as assignors on the 1995-08-23 inventor-to-BNR assignment (Google Patents legal events: "Assignors: BEDARD, FRANCOIS, CARON, FRANCE, REGNIER, JEAN").

Unusual patterns: none indicative of a fire-sale precursor. This is a textbook single-employer, three-inventor corporate filing — all three inventors were BNR staff, and they assigned to BNR and BNR assigned onward to Northern Telecom Limited on the same recorded date (1995-08-23), roughly nine months before issue (1996-06-11). I found no evidence that any inventor departed BNR/Nortel within 12 months of filing, and no inventor name reappears anywhere as an assignor or assignee later in the chain — I could not verify departure dates from public sources, so treat "no departures" as an absence of evidence rather than a positive finding.

---

Original assignee

Northern Telecom Limited (Google Patents: "Original Assignee — Northern Telecom Ltd"; the operative pre-issue assignment on 1995-08-23 runs from Bell-Northern Research Ltd. to Northern Telecom Limited).

• Product embodying the claims: yes. The patent describes a live Dynamically Controlled Routing (DCR) product architecture — the "network processor 25" of the specification corresponds to Nortel/BNR's DCR Network Processor, deployed with DMS-family and DPN-family switches. DCR was a shipped Nortel offering, not a paper design. This is therefore a genuine operating-company-origin patent, not an invention born in a licensing vehicle.
• Primary line of business: public telecommunications switching and transmission equipment (DMS-100/DPN-100 families); Northern Telecom was the Canadian operating flagship of the Nortel group.
• Current status: dissolved / wound down via bankruptcy. Northern Telecom Limited was renamed (see timeline), the parent Nortel Networks Corporation filed for creditor protection on 2009-01-14 (Chapter 11, In re Nortel Networks Inc., Bankr. D. Del. Case No. 09-10138; parallel CCAA proceedings in Canada), and the estate liquidated its assets. The patent portfolio was sold in 2011. Nortel as an operating enterprise no longer exists.

---

Assignment timeline

Reel/frame provenance key: [C] = confirmed for this patent; [S] = observed for a sibling Nortel/Rockstar patent in the same bulk recording, not confirmed for US 5,526,414; [—] = not retrieved.

1995-08-23 (recorded) — Reel/Frame [—]

• Conveyance: Assignment
• Assignor: Bédard, François; Caron, France; Régnier, Jean
• Assignee: Bell-Northern Research Ltd.
• Correspondent: not separately retrieved for this entry; the same 1995-08-23 recording batch for this patent is indexed to attorney Thomas Adams (Thomas Adams and Associates) — see next entry.
• Context: standard inventor-to-employer assignment.

1995-08-23 (recorded) — Reel/Frame [—]

• Conveyance: Assignment
• Assignor: Bell-Northern Research Ltd.
• Assignee: Northern Telecom Limited
• Correspondent: Thomas Adams — Thomas Adams and Associates (per the PlainSite attorney index entry: "8/23/1995 | Northern Telecom Ltd. | 5526414 | Dynamically Controlled Routing Using…"). Flag: the same attorney appears on other Bell-Northern Research recordings (e.g. 2/6/1991 | Bell-northern Research Ltd. | 07/662,631), so he is a repeat BNR/Nortel prosecution-and-recording attorney — this is not an NPE tell. Correspondent for the inventor→BNR leg is likely the same firm (same-day batch) but I did not confirm it.
• Context: internal corporate reorganisation (R&D subsidiary → parent).

1999-12-23 (recorded) — Reel/Frame [—]

• Conveyance: Change of Name (no change in beneficial ownership)
• Assignor: Northern Telecom Limited
• Assignee: Nortel Networks Corporation
• Correspondent: not retrieved.
• Context: change of name only.

2000-08-30 (recorded) — Reel/Frame [—]

• Conveyance: Change of Name
• Assignor: Nortel Networks Corporation
• Assignee: Nortel Networks Limited
• Correspondent: not retrieved.
• Context: change of name / intra-group reorganisation only.

2011-10-28 (recorded) — effective 2011-07-29 — Reel/Frame 027143/0717 [S] (one sibling Nortel patent renders the same recording as "027343/0717", an OCR-ambiguous value — treat the exact digits as unverified)

• Conveyance: Assignment of Assignors' Interest
• Assignor: Nortel Networks Limited
• Assignee: Rockstar Bidco, LP
• Correspondent: not retrieved.
• Context: bankruptcy fire-sale. Sale of ~6,000 Nortel patents/applications for US$4.5 billion, under the Asset Sale Agreement dated 2011-06-30 between the Nortel Sellers and Rockstar Bidco, LP (In re Nortel Networks, Bankr. D. Del. 09-10138); closing 2011-07-29. A bulk recording across the entire portfolio on 2011-10-28.

2014-01-31 (recorded) — Reel/Frame [—]

• Conveyance: Assignment
• Assignor: Rockstar Bidco, LP
• Assignee: Rockstar Consortium US LP
• Correspondent: not retrieved.
• Context: internal transfer within the Rockstar consortium structure (allocation of portfolio assets to the consortium partnership).

2014-02-05 (recorded) — Reel/Frame 031761/0137 [S]

• Conveyance: Assignment
• Assignor: Rockstar Consortium US LP
• Assignee: Constellation Technologies LLC (a Delaware limited liability company)
• Correspondent: not retrieved.
• Context: transfer-to-asserter — asset allocation to a Rockstar enforcement vehicle. (Reel 031761/0137 was observed in the IPR2014-01180 Power of Attorney for US 7,154,879, a sibling in the same bulk recording; not independently confirmed for US 5,526,414.)

2015-02-09 (recorded) — executed 2015-01-28 — Reel/Frame [—]

• Conveyance: Assignment (one instrument executed by all six Sellers)
• Assignors: Rockstar Consortium US LP; Rockstar Consortium LLC; Bockstar Technologies LLC; Constellation Technologies LLC; MobileStar Technologies LLC; NetStar Technologies LLC
• Assignee: RPX Clearinghouse LLC (wholly-owned subsidiary of RPX Corporation), One Market Plaza, Steuart Tower, Suite 800, San Francisco, CA 94105
• Correspondent: not retrieved. The publicly filed assignment instrument for this transaction shows signature blocks executed by individuals including Michael Dunleavy and Martin Roberts — these are corporate signatories, not the recording correspondent, and I am not treating them as a correspondent finding.
• Context: defensive aggregation / clearinghouse. Asset Purchase Agreement dated 2014-12-22; aggregate consideration US$900 million; funded by a syndicate of more than 30 companies that each received non-exclusive licences; RPX made the assets available to all other interested companies on FRAND terms (RPX Corp 8-K, 2015-02-03).

---

Timeline diagram

timeline
    title Ownership of US 5526414
    1994 : Inventors file application
    1995 : Inventors assign to Bell-Northern Research
         : BNR assigns to Northern Telecom Limited
    1996 : Patent issued
    1999 : Change of name to Nortel Networks Corporation
    2000 : Change of name to Nortel Networks Limited
    2009 : Nortel files for bankruptcy protection
    2011 : Portfolio sold to Rockstar Bidco LP
    2014 : Rockstar Bidco to Rockstar Consortium US LP
         : Transferred to Constellation Technologies LLC
    2015 : RPX Clearinghouse buys Rockstar portfolio

---

NPE / troll-pattern signals

1. Shell-entity transfer — PRESENT. The patent passed to Rockstar Bidco, LP (recording 2011-10-28) and then to Constellation Technologies LLC (recording 2014-02-05), both licensing-only vehicles that never made products. Constellation is expressly identified as "a Delaware limited liability company" in the RPX asset purchase agreement, and the Rockstar entities' sole documented activity was licensing and enforcement. Caveat: the 2011 transfer arose from a court-supervised bankruptcy auction of an entire portfolio, not from a bespoke troll formation — the form matches the signal even though the origin differs.

2. Known asserter in the chain — PRESENT. Rockstar Consortium US LP (Rockstar Consortium US LP v. Google Inc., No. 4:13-cv-05933 (N.D. Cal.) and E.D. Tex. actions 13-cv-00893 et seq. against ASUSTeK, HTC, LG, Pantech, Samsung, ZTE) and Constellation Technologies LLC (Constellation Techs. v. Time Warner Cable, 2:13-cv-01080 (E.D. Tex.); In re Constellation Techs. LLC Patent Litig., MDL No. 2558) are both documented high-frequency plaintiffs. Important qualifier carried over from the litigation section: neither campaign named US 5,526,414. RPX Clearinghouse is a defensive aggregator, not an asserter.

3. Repeat correspondent across the chain — UNCLEAR. The only correspondent identified is Thomas Adams on the 1995-08-23 Northern Telecom recording, and he is a repeat BNR/Nortel recording attorney (also on Bell-Northern Research filings, e.g. 1991-02-06, app. 07/662,631) — a non-signal. The correspondents on the 2011-10-28, 2014-01-31, 2014-02-05 and 2015-02-09 recordings were not retrievable in this session, so I cannot confirm or exclude a recurring NPE-side recording attorney. Marked unclear rather than inferred.

4. Cascading transfers — PRESENT. Four recorded transfers in ~40 months: 2011-10-28 → 2014-01-31 → 2014-02-05 → 2015-02-09, with the middle two only five days apart (2014-01-31 Rockstar Bidco→Rockstar Consortium US LP; 2014-02-05 Rockstar Consortium US LP→Constellation).

5. Pre-litigation transfer — NOT PRESENT (not established). No infringement suit naming US 5,526,414 was found in the litigation review, so there is no assertion event against which to measure the six-month window. Recorded as not present on the evidence available, not as a proven negative.

6. Bankruptcy fire-sale — PRESENT (strong). Nortel filed for creditor protection 2009-01-14 (Bankr. D. Del. 09-10138); the patent was swept into the US$4.5 B sale of ~6,000 patents to Rockstar Bidco, LP under the Asset Sale Agreement dated 2011-06-30, closing 2011-07-29, recorded 2011-10-28. This is the paradigm Kodak/Polaroid-style patent liquidation, and it is the origin of the entire downstream chain.

7. Privateering — PRESENT (portfolio-level). Nortel's portfolio was acquired in 2011 by a consortium of operating companies (Apple, Microsoft, RIM/BlackBerry, Ericsson, Sony, EMC) formed as Rockstar Bidco, LP. Rockstar/Constellation then asserted other Nortel patents against those members' competitors. For US 5,526,414 specifically, no assertion is documented — the privateering signal attaches to the portfolio, not to this patent individually.

8. Defensive aggregator — PRESENT (terminal). The chain ends at RPX Clearinghouse LLC (recorded 2015-02-09; executed 2015-01-28). Per RPX's own 8-K, the US$900 M acquisition was underwritten by a syndicate of 30+ companies receiving non-exclusive licences, and the assets were made broadly available on FRAND terms. This is the canonical anti-NPE / neutralisation endpoint.

---

Verdict

Defensive / non-asserting. The ownership chain terminates at RPX Clearinghouse LLC — recorded 2015-02-09, executed 2015-01-28 under a 2014-12-22 Asset Purchase Agreement — the defensive "clearinghouse" vehicle of RPX Corporation, which bought the Rockstar portfolio with syndicate funding and licensed it non-exclusively on FRAND terms. No infringement suit naming US 5,526,414 was found in this analysis, and the patent's 20-year term had already run out on 2014-10-26, before RPX closed the purchase. The tension in the record is explicit and should be flagged to whoever consumes this: the 2011–2014 segment (Rockstar Bidco, LP → Rockstar Consortium US LP → Constellation Technologies LLC) carries several textbook NPE-pattern signals — bankruptcy fire-sale (2011-10-28), licensing-only transferees, cascading transfers five days apart (2014-01-31 / 2014-02-05), and known asserters — but for this patent the assertion never materialised and the terminal owner is a defensive aggregator. Had the analysis window been cut off at 2014-02-05, the same chain would score as "NPE — high confidence."

Verify at: https://assignmentcenter.uspto.gov/ (search patent number 5526414) and https://assignment.uspto.gov/patent/index.html — both surface the same underlying reel/frame records and will let you fill in the [—] and [S] reel/frame values and the 2011–2015 correspondents that I could not retrieve here.

I'll research each cited reference to provide accurate citations and descriptions. Let me run targeted searches.

Prior-Art Analysis — US 5,526,414

Scope and method

Per your instruction, I confined the search to the literal number 5,526,414 and did not substitute look-alikes (e.g., the related continuation US 6,091,720, or EP 0 789 974, or the sibling US family members). Nothing in the record suggests those are the same document, and they are treated separately. The authoritative source used is the granted patent's own front-page citation data — the "Patent Citations (5)" and "Non-Patent Citations (8)" lists — which I cross-verified against the reference documents themselves (Google Patents / USPTO image mirrors).

Framing note (important): Every reference below is a reference the examiner cited on the face of the patent — i.e., art that was before the examiner and was distinguished, not art that was found to anticipate. Because US 5,526,414 has a priority/filing date of 1994-10-26 and predates the AIA, pre-AIA 35 U.S.C. § 102 governs. That means the relevant categories are:

• § 102(b): reference patented/published more than one year before 1994-10-26 → before 1993-10-26.
• § 102(a): reference patented/published before the applicant's invention (presumptively on/before 1994-10-26).
• § 102(e): US patent granted on an application filed before the applicant's invention/filing date.

Bottom line up front: None of the five patent citations discloses the single limitation that gives US 5,526,414 its novelty — a "virtual destination node" representing a group of two or more components, each a distinct physical network element, with a link composed of a set of circuit groups to the components (claim 1). Consequently, no cited reference anticipates claim 1 (or dependent claims 2, 4, 6) in full. Each reference is relevant to isolated limitations or to the environment of the invention, as detailed below. The strongest candidates for a § 103 obviousness challenge (had one been mounted) are US 4,284,852 and US 4,669,113; the closest terminology match is US 5,297,137, but it uses "virtual node" in an unrelated sense.

---

1. US 4,284,852 — "Alternate routing for a telephone system"

Brief description (from the document): A cluster of stored-program-control switching offices, each with direct trunk groups to the others in the cluster, each office able to act as an originating, terminating, or tandem office. The invention stores, at each switching office, (i) an indication of the terminating office, (ii) an addressable indication of the switching office most likely to serve as a tandeming office, and (iii) the trunk lines to be used to reach that tandem office. A logic device (the forerunner of the network processor) periodically updates the stored alternate-route/tandem data. This is the reference US 5,526,414 itself credits in its background as "An early version of dynamically controlled routing" (citing "U.S. Pat. No. 4,284,852 issued Aug. 1981").

§ 102 analysis:

• Claims 1, 3, 5 (routing information structure + periodic updating means): This reference discloses almost the entire mechanical architecture of independent claim 1 — direct route first, tandem/alternate route if the direct route is busy, addressable storage of destination, tandem, and trunk-group data, and periodic external updating of the tandem recommendation. It is directly relevant to limitations (i)–(iv) of claim 1 and to the "means for updating the routing information."
• Why it does not anticipate: It contains no teaching of a virtual destination node, no grouping of two or more distinct physical switches into a single logical destination with a set-of-circuit-groups link, and no intra-link proportional distribution. Every "destination" and "tandem" in '852 is a single physical office. Under the strict all-elements rule for § 102, claim 1 is not anticipated.
• Potentially relevant to: the preamble and structural limitations of claim 1; the "means for updating" concept in claims 3 and 5.

---

2. US 4,669,113 — "Integrated network controller for a dynamic nonhierarchical routing switching network"

Brief description: A dynamic nonhierarchical routing network with a centralized network controller that computes both first-choice and alternate routes and downloads them into the memory of the stored-program switching offices. Each switch holds a table of routing sequences and, when its direct path is busy, tries alternate paths having one or more intermediate offices. The disclosure includes the network controller gathering data-link information and using it to derive, in near-real-time, routing information for each switch. (Its EPO counterpart search report even flags "US-A-4,669,113 (ASH)" as an X-category reference against claims 1 and 3–6 of a different application — underscoring its breadth as routing prior art.)

§ 102 analysis:

• Claims 3 and 5 (network-processor means computing and periodically updating alternate routing): Strong content match. '113 discloses a common controller that receives information from all switches and computes alternate routing information distributed back to the switches, which is precisely the "updating means / network processor means" recited in claims 3 and 5.
• Claim 4 / claim 6 (NP takes into account full availability of links): '113's controller evaluates alternate paths on capacity/blocking, broadly relevant, though it does not contemplate a link composed of a plurality of circuit groups to a virtual node.
• Why it does not anticipate: No virtual destination node, no multi-component logical destination, no set-of-circuit-groups link, no proportional intra-link distribution. It is hierarchical/centralized controller art, not virtual-node art.
• Potentially relevant to: claims 3, 5 (updating means), secondarily claims 4, 6.

---

3. US 4,788,721 — "Routing of network traffic"

Brief description: A state-dependent, dynamic, non-hierarchical routing process in which each switch maintains a table of routes of at most two trunk groups between the switch and each other switch, and exchanges occupancy/allocation factors with the destination switch. Routes are generated at intervals from network configuration and traffic data; on a service request the switch computes occupancy values and selects the minimum, blocking if it exceeds a threshold. Its claims expressly recite maintaining "a table of routes with each of said routes comprising at most two trunk groups between the switch and each of the other switches" and querying the destination switch for occupancy factors.

§ 102 analysis:

• Claim 1 (two-link alternate routing / routing-table structure): Relevant to the "direct route first, then a two-link alternate via a tandem" behavior and to the per-switch routing table. Its "at most two trunk groups" route model parallels the DCR "two-link alternate" constraint recited in US 5,526,414's specification.
• Claims 3, 5 (computed alternate routing / updating): Relevant to the periodic computation of routing information, though '721 favors distributed per-switch computation with inter-switch factor exchange rather than the central network-processor recommendation of the '414 claims.
• Why it does not anticipate: No logical/virtual destination node, no multi-switch grouping, no link = set of circuit groups. It also lacks the "protective allowance / safe idle circuits" reserve concept that US 5,526,414 relies on.
• Potentially relevant to: claim 1 (routing-table structure and two-link alternate behavior); claims 3, 5 as secondary.

---

4. US 5,297,137 — "Process for routing data packets around a multi-node communications network"

Brief description: A dynamic routing scheme for data-packet networks in which a virtual ring is embedded in an arbitrary multi-node topology. Each node has at least one pair of input/output ring links, and "each pair of input and output ring links forms a virtual node" of that node; some nodes contain multiple virtual nodes and can short-cut packets across them. Packets are routed so the ring distance to destination always decreases, using only destination-identifying data.

§ 102 analysis — note the trap in the terminology:

• At first glance '137 is the most dangerous citation because it literally uses the phrase "virtual node." However, its "virtual node" is a different construct: a pair of input/output links within a single node on an embedded ring — not a destination node formed by grouping two or more distinct physical network elements and reachable by a set of circuit groups from an origin. US 5,526,414's virtual node is expressly a destination-only logical entity (the patent states "a virtual node can only be a destination node" and has no outgoing links). '137's virtual nodes are intra-node switching structures on a ring, in a packet (not circuit-switched telephone) context.
• Why it does not anticipate any claim: It does not teach a virtual destination node, a multi-component destination, an origin-to-virtual-node link composed of the union of circuit groups to the components, intra-link proportional distribution, or a network-processor updating tandem recommendations for a virtual node.
• Potentially relevant to: claim 1's "virtual destination node" terminology only for § 103/§ 112 purposes — it is the reference a challenger would raise to show that "virtual node" was known terminology, while conceding (or arguing) the different meaning. It is not a § 102 anticipation of any claim.

---

5. US 5,377,262 — "Telecommunication switching system having adaptive routing switching nodes"

Brief description: A switching system in which nodes perform adaptive routing using a dialing-plan hierarchy and a separate switching-node hierarchy. Routing tables are based on telephone numbers and on unique switching-node numbers; a destination switching node transfers its routing information back to an originating node, which combines it with its own to shorten future call paths. (The European sibling EP 0 556 515 B1 carries the same disclosure.)

§ 102 analysis:

• Claim 1 (translation of address data to determine a destination node; routing tables): Relevant to the "means for translating address data of a call to determine a destination node" limitation and to the maintenance of routing tables keyed to node numbers — but its destination is always a single physical switching node.
• Why it does not anticipate: Entirely hierarchical, node-number-driven adaptive routing. No logical/virtual destination grouping, no set-of-circuit-groups link, no network-processor tandem recommendation for a virtual destination.
• Potentially relevant to: claim 1 (address translation/destination determination), secondarily the "routing information" storage concept. It is not a § 102 anticipation.

---

Non-patent literature cited (8 entries, 4 unique — each listed twice in the record)

Two of these are highly material to enablement/background and to the § 103 landscape:

1. G. R. Ash, R. H. Cardwell, R. P. Murray, "Design and Optimization of Networks with Dynamic Routing," Bell System Technical Journal, Vol. 60, No. 8, Oct. 1981, pp. 1787–1820. — Foundation for dynamic nonhierarchical routing (DNHR); background only; no virtual-node teaching. § 102(b) art.
2. Hugh Cameron & Serge Hurtubise, "Dynamically Controlled Routing," Telesis, 1986, pp. 33–37. — The DCR system's own descriptive article (same corporate lineage); describes link-based DCR without virtual nodes. § 102(b) art as to DCR generally.
3. G. R. Ash, A. H. Kafker, K. R. Krishnan, "Servicing and Real-Time Control of Networks With Dynamic Routing," Bell System Technical Journal, Vol. 60, No. 8, Oct. 1981, pp. 1821–1845. — Companion DNHR paper; background only. § 102(b) art.
4. Jean Régnier & W. Hugh Cameron, "State-Dependent Dynamic Traffic Management for Telephone Networks," IEEE Communications Magazine, pp. 42–53. — The origin of the protective allowance (PA) and safe idle circuits (SIC) concepts that US 5,526,414's claims 4/6 and its NP recommendation algorithm build upon; the '414 body cites this piece directly.

⚠ Flagged contradiction (as instructed): The '414 specification body cites the Régnier & Cameron article as "IEEE Communications, Nov. 1991," while the patent's own Non-Patent Citations list gives it as "IEEE Communications Magazine Oct. 1990, pp. 42–53." Additionally, the record lists this article's author as "Jean R gnier" (a character-encoding corruption of "Régnier"). I am reporting both dates verbatim rather than harmonizing them; the October 1990 date is the one that appears in the examiner's citation list.

---

Consolidated § 102 mapping

Assessment of "most relevant prior art":

• For the novel subject matter ("virtual destination node" = group of ≥2 distinct physical elements; link = set of circuit groups), no cited reference is anticipatory. The most relevant for a § 103 challenge on that point is US 5,297,137, solely because it uses the term "virtual node" — a challenger would have to argue equivalence despite the fundamentally different (packet-ring, intra-node) meaning, and would still fail on the "destination / multi-component / set-of-circuit-groups" limitations.
• For the claimed architecture and updating machinery, the most relevant are US 4,284,852 (same-assignee DCR ancestor from which the '414 specification expressly descends) and US 4,669,113 (central controller computing and downloading alternate routes) — these two, combined with the Régnier & Cameron PA/SIC paper, map onto essentially every claim element except the virtual destination node.

Caveats. (1) This analysis is limited to the five patent citations and eight (four unique) non-patent citations on the face of US 5,526,414 plus the family/prosecution artifacts surfaced in the record. An examiner-cited list is not an exhaustive prior-art universe; third-party art, foreign publications, or intervening art could exist. (2) I could not retrieve the underlying USPTO Patent Center prosecution file (office actions, examiner's stated § 102/§ 103 grounds) in this session, so the "which claims may be anticipated" discussion is my element-by-element reading of the claim language against each reference, not a quotation of any examiner rejection. (3) I did not locate any litigation or PTAB record establishing that any of these references was actually applied to reject a claim; per the earlier litigation summary, no assertion of this patent surfaced publicly, and it expired 2014-10-26.

I'll ground the obviousness analysis in the actual prior-art references listed on this patent's record. Let me pull the key cited references.

Obviousness Analysis — US 5,526,414 under 35 U.S.C. § 103

Built on the previously generated Summary and Litigation sections. I do not repeat their content; I flag contradictions where they arise.

Scope note / minor inconsistency flag: The system context states today's date is 2026-09-30 (consistent with the 2026-09-30 retrieval timestamp in the fetched patent text), while this task's header states "Current Date: April 26, 2026." Nothing in the § 103 analysis turns on the ~5-month difference, but the two dates cannot both be correct and I am flagging it rather than silently choosing.

Governing law: US 5,526,414 has a filing/priority date of 1994-10-26, so pre-AIA 35 U.S.C. §§ 102/103 govern (including § 102(e) art). The Graham v. John Deere framework applies: scope and content of the prior art, differences between the prior art and the claims, the level of ordinary skill, and objective indicia. Under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), a claimed combination is obvious where the improvement is "the predictable use of prior art elements according to their established functions," and a "finite number of identified, predictable solutions" gives a PHOSITA good reason to pursue them.

---

1. The prior art of record (the "Prior Art" section of this page)

The Google Patents record for US 5,526,414 lists three tiers of prior art. All of it is available as § 103 art against the 1994-10-26 filing date.

Critically, the specification itself admits DCR as prior art. The Background states that "known DCR networks use a procedure inherited from FHR known as Unique Exit Gateway," and that "each final destination is associated with an intermediate destination node within the DCR network." The entire node/link model, the network processor (NP), the 10-second update cycle, two-link tandem alternate routes, PA and SIC are all described in the Background/Description as existing DCR — not as the invention. This is the classic In re Fout / applicant-admission situation: everything except the "virtual destination node" limitation is admitted art against the applicant.

The delta. Stripped of admitted art, claim 1's only point of novelty is:

"…said listing of destination nodes of at least one of said switching elements comprises a virtual destination node representing a group of two or more components, each component being a distinct physical network element, there being one or more distinct circuit groups associated with each component, and each link from a particular origin node to the virtual destination node is a set of circuit groups from the switching element at that particular origin node to the two or more components."

Claims 2, 4 and 6 are all limitations on how that one delta is implemented (proportional random selection; full-availability accounting). Claims 3 and 5 are pure admitted-DCR NP architecture.

---

2. Level of ordinary skill in the art

A PHOSITA here would be a person with a bachelor's degree in electrical engineering or computer science and roughly 3–5 years of experience in public switched telephone network design or stored-program-control (SPC) switch call processing, or equivalent industry experience — familiar with FHR, DCR, DNHR, CCS7, trunk-group hunting, and trunk reservation. This is a high-skill, fast-moving, engineering-driven art in 1994, saturated with published routing literature (the six NPL items on the face of the patent alone). That matters: the more predictable and well-charted the art, the stronger the case that substituting a group for an individual element is an obvious design choice (KSR; In re Kubin).

---

3. Claim 1 — element mapping

---

4. Grounds of rejection

Ground 1 — Claims 1 and 2 obvious over the admitted DCR system in view of US 5,311,585

US 5,311,585 ("Carrier proportioned routing") discloses exactly the architectural device claim 1's delta recites. In the '585 embodiment, an originating switch (101) must route calls to "country X," which is served by multiple carriers reachable through four distinct egress switches (105, 107, 109, 111). The originating switch's routing table (Table 1) lists those egress switches with "initial try probabilities." As the reference states:

"originating switch 101 is unaware of the number of carriers serving country X. The only thing it is aware of is which ones of egress switches 105, 107, 109 and 111 serve country X. This knowledge is embodied in a routing table for calls to country X…
… the initial try probabilities represent the relative frequency with which each egress switch should be selected the first time an egress switch is selected for a call to country X."

And the '585 claims expressly recite retry across the group: claim 20 ("means for launching from said originating switch said call so that it is destined for a different switch in said telephone network that directly connects to said assigned carrier"), claim 21 ("wherein said different switch is a switch to which no previous attempt has been made"), claims 22 and 27–29 (assign → route → crankback → repeat).

Element-by-element, '585 supplies:

• a logical destination ("country X"/assigned carrier) that is not a physical switch — the same abstraction as the "virtual destination node";
• two or more components, each a distinct physical network element (egress switches 105, 107, 109, 111);
• distinct circuit groups associated with each component (trunk groups 113, 119, 149, 155);
• a "link" from the origin to that logical destination that is the set of those circuit groups (the originating switch's set of trunks to the group of egress switches);
• proportional, random selection among the members, with retry of untried members on failure — i.e., claim 2's "specified proportions… attempts the circuit groups randomly in dependence upon the specified proportions."

Motivation to combine — why a PHOSITA would put '585's group-routing into DCR's node/link framework:

1. The problem is stated in '414's own Background: the Unique Exit Gateway makes the intermediate destination node "critical," so "congestion or failure at its switch would result in failure to complete the call," and "other networks elements might be able to route calls to the final destination, [but] the DCR network is not allowed to use them as alternative exit points." '585 solves the same problem — spreading egress across all switches that can reach the destination — in the same technology (SPC toll switches, CCS7 signalling, stored routing tables).
2. '585 expressly frames its proportions as a traffic-engineering tool to "achieve a predetermined traffic distribution," which is the same objective DCR's NP already optimizes (trunk efficiency, minimizing links per call).
3. Nothing in DCR's node/link model requires a node to be a switch. The '414 specification admits this itself: "such correspondence is not necessarily the case in embodiments of the invention," and the routing model is "node and link based, as opposed to switch and circuit group based." Once nodes are acknowledged to be logical, defining a node whose members are a set of physical egress switches is a predictable use of a known element (proportional group selection) according to its established function, which is precisely the KSR formulation.
4. The expectation of success is high and the result predictable: the DCR switch already maintains a routing table entry with an "associated link"; populating that link with the union of circuit groups toward each member of the group is a table-population exercise, not a new routing algorithm. The NP's recommendation machinery (admitted art) carries over unchanged.

Conclusion: Claim 1 would have been obvious. Claim 2 is a fortiori obvious — '585's initial try probabilities plus its "untried switch" retry mechanism read directly on claim 2's random/proportional intra-link distribution, and the '414 spec's own FIG. 4 algorithm is a routine implementation of the same traffic-engineering objective. (See also Ground 3 for the Ash NPL reinforcement of random proportional allocation.)

---

Ground 2 — Claims 3 and 5 obvious over the admitted DCR system in view of US 4,669,113 (and/or US 5,142,570)

Claims 3 and 5 require only: (a) network-processor means communicating with the switches over a data communications system; (b) each switch periodically reporting local network conditions; (c) the NP computing alternate routing information from all switches' reports and periodically updating tandem-node identifications; and (d) in claim 5, updating tandem-node recommendations involving the virtual destination node.

Every one of these is admitted DCR prior art, and is independently corroborated by US 4,669,113, which discloses:

• a common controller (the "logic device") and data links over which switching offices report traffic and idle/busy trunk status;
• the controller computing candidate path groups for each originating switch and notifying each OS of its computed candidate and alternate routes;
• a least-loaded-path recomputation that substitutes a new route into the route-selection sequence — i.e., periodic updating of the alternate (tandem) recommendation;
• corroboration in the JP counterpart JP 2,897,875 B2 claim text ("a device for generating an update candidate path… and placing the update candidate path at the head of a corresponding one of the candidate paths, thereby setting the update candidate path to be the second candidate route").

US 5,142,570 independently confirms the periodic-measurement/central-computation model: "At preselected time intervals, sets of routes through the network are generated in response to the network configuration and traffic information… At predetermined intervals, traffic usage data is measured… occupancy values… used to compute occupancy values associated with each of the routes."

Motivation: The NP architecture is the pre-existing DCR architecture; adding a virtual destination node to the destination-node listing is transparent to the update loop — the NP simply computes recommendations for an (O, V) node pair exactly as it does for any (O, D) pair composed of two links. Nothing in claims 3 or 5 requires any change to the reporting/recommendation mechanism, so these claims add nothing patentable over the combination that already renders claim 1 obvious. A PHOSITA would have had every reason to keep DCR's existing NP update cycle when introducing the '585-style group destination, because the whole point of DCR is that the NP re-optimizes alternate routes every cycle to route around failures — which is the very benefit the virtual node delivers.

Conclusion: Claims 3 and 5 would have been obvious.

---

Ground 3 — Claims 2, 4 and 6 obvious over the admitted DCR system in view of US 4,669,113 and US 4,788,721 / US 5,311,585 (and the Ash NPL)

Claim 4 and claim 6 require that the NP, "when computing alternate route recommendations, takes into account full availability of each of the links, including links composed of a plurality of circuit groups."

US 4,669,113 is directly on point. It describes the design philosophy that the parallel-path structure "effectively gives each OS-TS pair access to the capacity of a large number of parallel paths and, through use of traffic sensitive dynamic routing, makes the combination of parallel paths behave as a single large trunk group" (lexdana.ai/patent/04669113, quoting the '113 disclosure). That is precisely claim 4/6's "full availability of each of the links, including links composed of a plurality of circuit groups" — the link's total idle capacity, not the capacity of any single circuit group, drives the recommendation.

US 4,788,721 / US 5,142,570 supply the aggregate-measurement counterpart: occupancy values are computed across the whole route ("the summation is over all links k comprising each route R"), i.e., a route's desirability is a function of the aggregate state of all its constituent links.

Claim 2's random proportional distribution is separately taught by US 5,311,585 ("initial try probabilities represent the relative frequency with which each egress switch should be selected") and, in the routing literature cited on the face of the patent, by the CGH/cyclic proportional-allocation techniques associated with the Ash et al. BSTJ 1981 papers (cited as references [1] and [3] on the '414 record). The '414 specification itself concedes that the "proportions are those supplied by the user" — i.e., a parameter choice, not an inventive algorithm.

Motivation / predictable result: Once the link to the virtual node is defined as a set of circuit groups (Ground 1), the NP's existing idle-capacity computation must, as a matter of arithmetic, consider the sum of the idle circuits of all circuit groups in the set in order to rank candidate alternate routes; and the switch's existing trunk-hunt, generalized to a random proportional hunt over the set, is the natural way to honor the user's engineering weights. Both steps are the "predictable use of prior art elements according to their established functions" (KSR). The '414 specification effectively admits as much when it describes the "new algorithm" as reusing the "current DCR algorithm" and the PA/SIC machinery, summing IC_g over the circuit groups of the link (EQU1) and distributing the PA reservation.

Conclusion: Claims 2, 4 and 6 would have been obvious.

---

Ground 4 — Alternative single-reference-family combination

Should a fact-finder prefer a tighter technological match, the same result follows from US 4,788,721 + US 5,142,570 + US 5,311,585. The Bellcore '721/'570 pair supplies the node-and-link network model, per-node first/alternate routing tables, central route computation from periodic traffic measurements, and multi-link routes; '585 supplies the group-of-physical-elements-as-one-logical-destination and proportional selection. A PHOSITA seeking to make the Bellcore/DCR exit arrangement failure-tolerant would treat a set of egress switches that all reach the same final destination area as one routing destination, exactly as '585 does for carriers.

---

5. Claim-by-claim conclusion table

---

6. Anticipated patentee rebuttals, and why they likely fail

(a) "No reference discloses a virtual node." Labels are irrelevant; § 103 asks whether the claimed structure is disclosed or suggested. US 5,311,585's routing table maps a logical destination (country X / assigned carrier) onto a group of distinct physical egress switches reachable by distinct trunk groups, with proportional selection and retry — the structural content of claim 1's delta.

(b) "DCR nodes represent switches; a group of switches cannot be a node." The specification refutes this: "Such correspondence is not necessarily the case in embodiments of the invention"; a destination node "may represent a group of switches"; and the routing is "node and link based, as opposed to switch and circuit group based."

(c) "The virtual node is not an origin node and has no outgoing links — a new architectural rule." That negative limitation is a consequence of the group being a destination only; it is not recited in claim 1 as a structural constraint beyond "destination node," and it follows automatically when the members are egress points.

(d) "Teaching away." The closest candidate is the DCR practice that a destination node must be able to act as a tandem. But DCR already accommodates non-tandem destinations (the Unique Exit Gateway itself need not be a tandem), and '585 affirmatively teaches the desirability of the group approach. There is no reference in the record that criticizes, discredits, or discourages treating a plurality of switches as one routing destination.

(e) Unexpected results / objective indicia. None is disclosed in the patent, and the litigation review in the previous section found no asserted-patent litigation, no PTAB proceeding, and no licensing activity tying commercial success to this patent. Absent a nexus between any indicium and the "virtual destination node" limitation specifically, no secondary consideration is available. (I note the explicit caution from the previous sections: the absence of litigation is a negative search result, not proof.)

---

7. Confidence and explicit uncertainties

• High confidence: that US 5,311,585 discloses a group of egress switches treated as one routing destination with stored proportional selection and retry — I have the reference's own text and claims (§4, Ground 1). Its 1992-04-14 filing and 1994-05-10 issue date confirm it is prior art against the 1994-10-26 filing.
• High confidence: that DCR, its NP, its 10-second update cycle, its PA/SIC machinery, and the Unique Exit Gateway are admitted prior art — the '414 specification says so in terms, and cites Cameron & Hurtubise and Regnier & Cameron.
• Moderate confidence: my characterization of US 4,788,721 and US 4,282,852. I did not retrieve their full texts in this pass; I am relying on their titles, dates, the '414 specification's own description of '852 ("An early version of dynamically controlled routing is disclosed in U.S. Pat. No. 4,284,852"), and general knowledge of the Bellcore/Northern Telecom routing literature. These two are not load-bearing for any ground above — '585 and '113 carry the analysis — but a full-text review is advisable before formalizing.
• Moderate confidence: that the Ash et al. BSTJ 1981 papers specifically describe random-number-based proportional/CGH allocation. That technique is discussed in the routing literature, but I have not verified the exact passage in the 1981 BSTJ text; I therefore rest claim 2's proportional-randomness teaching primarily on US 5,311,585, which I have verified.
• Unknown to me: whether any reference in the record expressly characterizes a "group of switches" using the term "virtual node," and whether any uncited 1993–1994 art (e.g., unpublished Bellcore/Nortel internal work) exists that would be even closer. Nothing in the record suggests '414's delta was novel in substance, only perhaps in DCR-specific labeling.

---

8. Sources

• Full patent text, claims and Prior Art section: https://patents.google.com/patent/US5526414/en (retrieved 2026-09-30)
• US 5,311,585, "Carrier proportioned routing" (AT&T Bell Labs): https://patents.google.com/patent/US5311585 · claims via http://www.everypatent.com/comp/pat5311585.html
• US 4,669,113, "Integrated network controller for a dynamic nonhierarchical routing switching network": https://patents.google.com/patent/US4669113 · https://lexdana.ai/patent/04669113 · JP family member JP 2,897,875 B2: https://patents.google.com/patent/JP2897875B2/en
• US 5,377,262, "Telecommunication switching system having adaptive routing switching nodes" (AT&T; EP 0 556 515 counterpart): https://patents.google.com/patent/US5377262 · https://patentimages.storage.googleapis.com/74/c7/8a/3927c74868a2a4/EP0556515A3.pdf
• US 5,142,570, "Routing of network traffic using discrete traffic measurement data" (Bellcore; EP 0 537 153 A1 / WO 91/20148 counterpart): http://data.epo.org/gpi/EP0537153A1 · claims via http://www.everypatent.com/comp/pat5142570.html
• Cameron & Hurtubise, "Dynamically Controlled Routing," Telesis (1986), and Regnier & Cameron, IEEE Communications Magazine (Oct. 1990) — cited on the face of '414 and incorporated by reference
• Ash, Cardwell & Murray, BSTJ 60(8) Oct. 1981, pp. 1787–1820; Ash, Kafker & Krishnan, BSTJ 60(8) Oct. 1981, pp. 1821–1845 — cited on the face of '414
• Family member: US 6,091,720 (continuation), https://patents.justia.com/patent/[6091720](/patent/6091720); EP 0 789 974 B1 (PCT/CA1995/000600)

Bottom line: On the record's own prior-art section, every element of claims 1–6 other than the "virtual destination node" concept is admitted DCR art, and that concept is disclosed in substance by US 5,311,585, with US 4,669,113 supplying the network-processor/aggregate-availability limitations. US 5,526,414 is, in my assessment, vulnerable to a § 103 rejection over the admitted DCR system in view of US 5,311,585 and US 4,669,113 — though the patent is expired (anticipated expiration 2014-10-26, per the record), so this analysis is of historical/validity-review interest rather than of live-assertion interest.