US 6091720

I'll search for authoritative information on US 6091720, including any 2026 CAFC activity.

US Patent 6,091,720 — Analysis

Sourcing note

I searched for the patent on the open web (Google Patents, FreePatentsOnline, Justia, patentimages PDF). I did not find any 2026 CAFC docket, IPR, or Federal Circuit appeal activity tied to this patent number. Given the patent's legal status (expired 2014), that absence is expected, but I want to be explicit: I could not confirm any 2026 CAFC docket entry for 6,091,720, and I have no authoritative PACER/CourtListener docket record for it. Treat any 2026 litigation claim as unverified. I also did not retrieve a direct USPTO PatentCenter/PAIR record; the bibliographic data below is from the patent front page as reproduced on Google Patents, FreePatentsOnline, and the USPTO-printed PDF, which agree with each other.

Bibliographic data

Abstract

A DCR telecommunications network has switching elements interconnected by circuit groups, plus a network processor. If a direct route is unavailable, a switch uses a routing table of alternate routes updated periodically by the network controller. The network is modeled as nodes and links, with routing on a node-to-node basis. At least one node is a virtual destination node — a logical entity corresponding to a group of two or more components (physical network elements). A link to a virtual destination node is the set of circuit groups connecting to its components. Final destinations outside the network can be associated with the virtual destination node as an intermediate destination node, so a call can exit via any component rather than a single Unique Exit Gateway. Where such a link has multiple circuit groups, the switch stores proportions for those groups and attempts them according to those proportions. Proportions may be fixed (off-line) or updated by the network processor from call-completion information reported periodically by the switches.

Independent claims (plain language)

Claim 1 — Network apparatus. A telecom network of nodes and links, where nodes are origin nodes (a switch that can route calls) and destination nodes, some nodes being transit nodes (both origin and destination). Each link directly interconnects an origin and a destination node and contains one or more circuit groups. Each switch stores routing information: (i) a list of destination nodes; (ii) the corresponding link for each destination, where one exists; (iii) the outgoing circuit group(s) for each link; and (iv) a list of zero or more transit nodes per destination. Each switch translates call address data to determine a destination node, then (a) tries the direct link if one exists, or (b) if no link is available, selects a transit node and tries the link to that transit node.

The inventive core: for at least one origin switch, the destination list includes a virtual destination node representing a group of two or more components, each a distinct physical network element, with distinct circuit group(s) per component. The link to that virtual destination node is the set of circuit groups from the origin switch to all those components. That link has multiple circuit groups, and the switch's storage holds a specified proportion for each; the switch attempts circuit groups based on those proportions. Specifically, the switch:

1. determines set S of all circuit groups with a non-zero proportion;
2. checks whether S is empty;
3. overflows the call if S is empty;
4. otherwise makes a weighted random selection from S and attempts that circuit group;
5. if no idle circuit is found there, removes that group from S; and
6. repeats until the call is carried or S is exhausted (then overflow).

Claim 16 — Method. The method counterpart. At each origin-node switch: (i) attempt the direct link if it exists; (ii) if no link is available, consult the routing information, pick a transit node, and attempt the link to it. The destination list of at least one origin switch includes a virtual destination node of two or more components (each a distinct physical network element) with distinct circuit groups; the link to that virtual node is the set of circuit groups to those components; and the switch attempts the circuit groups in dependence upon the stored proportions, using the same steps 1–6 (build set S of non-zero-proportion groups, test emptiness, overflow if empty, weighted random selection and attempt, remove failed group from S, repeat).

Dependent claims 2–15 (from claim 1) and 17–27 (from claim 16) add: the network processor and its periodic update cycle; full-availability treatment of multi-circuit-group links; protective allowance / safe idle circuits (SIC) computation with per-circuit-group reservations; dynamic updating of the proportions; component reporting of "completion capability"; and the centralized weighting formulas (idle-circuit weight W1, completion-capability weight W2, combined weight W, transformed and blended proportions).

Confidence and caveats

• Bibliographic fields above are consistent across three independent reproductions of the front page; I rate them high confidence.
• Claim numbering (claim 1 independent apparatus, claim 16 independent method, 27 claims total) is inferred from the claim text reproduced in the search results; the final claims 22–27 were visible, and claim 27 appears to be the last. High confidence, but I did not read the full printed claim set end-to-end.
• I could not verify 2026 CAFC activity. No such docket surfaced, and none is expected given the 2014 expiration.
• I did not verify whether any litigation ever asserted this patent, nor any reexamination/reexam certificate; I have no authoritative record on that and am not asserting either way.

I'll search for litigation involving US Patent 6,091,720.

Let me search more targeted litigation databases and patent-specific sources.

Summary of Findings

I could not find any litigation specifically identifying U.S. Patent No. 6,091,720. Based on the searches run against publicly indexed litigation and patent sources, there is no complaint, docket, or reported decision that asserts or adjudicates this particular patent number.

What the patent is (context relevant to litigation)

• Patent: US 6,091,720 B1, "Dynamically controlled routing using dynamic management of intra-link traffic to virtual destination nodes"
• Inventors: François Bedard, Jean Regnier, France Caron
• Original assignee: Nortel Networks Corp. (assignment from Bell-Northern Research Ltd.); current listed assignee Nortel Networks Ltd.
• Priority: 1994-10-26 (CIP of Ser. No. 08/329,716, now US 5,526,414); filed (PCT/CA95/00600) 1995-10-26; granted 2000-07-18.
• Status: Expired – Fee Related (anticipated expiration 2014-10-26).

Candidate leads I checked that do NOT involve this patent

The searches surfaced several well-known Nortel-related patent suits, but on inspection none asserts US 6,091,720:

I also flagged and excluded numerous false-positive hits for different patents that merely share a similar "…172" or "…220" suffix (e.g., US 10,557,172, US 10,731,220, US 5,904,172, US 10,741,172, "05-MDL-1720"), per your instruction not to return similar numbers.

Important caveats

1. No affirmative litigation found, but this is not proof of none. I do not have direct authenticated access to the Unified Patents litigation portal, PACER, or Docket Navigator in this session; my findings rest on web-indexed sources (Google Patents, CourtListener/Justia, RPX, news). A patent that is expired and was never asserted in a public district-court or ITC action would leave little to no public trace, which is consistent with what I see.
2. Nortel's portfolio context. Because US 6,091,720 was part of the Nortel portfolio sold to Rockstar in 2011, it is possible it was included in license-demand or portfolio-enforcement activity that was never filed as a public suit. I found no such public record tying this number to a case.
3. No PTAB proceedings identified. I found no IPR/PGR/CBM referencing this patent.

Conclusion

Based strictly on the available search results, no litigation involving US 6,091,720 is known — no plaintiff(s), defendant(s), jurisdiction, case number, filing date, or outcome can be reported for this patent. If you need a definitive negative, the authoritative next steps would be a direct PACER/Docket Navigator search on the patent number and a Unified Patents portal lookup, which I was unable to query directly here. I'd rather flag that gap explicitly than assert an unverified "none."

I'll start by checking the structured data (which reports no AIA proceedings) against live web sources, since the task asks me to flag any proceedings ODP may not have indexed.

The initial searches surfaced only unrelated "609" patents (the '609 fluoropolymer and '609 vehicle-state patents). Let me run targeted checks on the specific patent number and its inventors, plus a check for defensive-aggregator activity.

One more check — the patent title plus "IPR," and a check for related litigation that would typically trigger PTAB activity.

Proceedings overview

Total AIA trial proceedings on file: 0. The structured "PTAB proceedings on file" block — sourced from the USPTO Open Data Portal and treated here as canonical — returns no IPR, no PGR, and no CBM for US 6,091,720. My live web searches (Google Patents, FreePatentsOnline, Justia, CourtListener-adjacent sources, PTAB petition repositories) turned up no proceeding number, no institution decision, no Final Written Decision, and no Federal Circuit appeal for this patent. Every "609" hit in the results was a different patent — U.S. 7,122,609 (Chemours/Daikin fluoropolymer, IPR2018-00992/-00993) or U.S. 9,152,609 (Allstate vehicle-state, IPR2021-01209) — none of which is this patent.

Because the canonical list is empty, there are no per-proceeding sections to write, and I will not invent proceeding numbers to fill the template. The honest answer is: no PTAB activity exists, and there is nothing to quote.

Bottom-line defensive posture: This is not a "hardened by surviving IPRs" patent and not a "claims already canceled" patent. It is a claimed-but-untested, long-expired patent. The dominant defensive fact is not PTAB at all — it is that US 6,091,720 expired on 2014-10-26 (listed status: "Expired – Fee Related"; "Anticipated expiration 2014-10-26" per the Google Patents record). An expired patent cannot be infringed going forward, and the damages window under 35 U.S.C. § 286 closed years ago. Any demand letter asserting current infringement of this patent is baseless on its face, independent of any invalidity theory.

Proceedings detail

(No proceedings to enumerate. Per the required format, a "most-impactful proceeding first" ordering is inapplicable — the list is empty.)

For completeness, the following confirms what does not exist:

• No IPR. No petitioner ever challenged claims 1–27 (or any subset) of US 6,091,720 under §§ 102/103 at the Board.
• No PGR. Not available in any event — the patent's 1994-10-26 priority predates the AIA's first-inventor-to-file regime, and the PGR window is long closed.
• No CBM. The CBM transitional program sunset on 2020-09-15 (37 C.F.R. § 42.300(d)), and this call-routing/circuit-group patent is in any case not directed to a "financial product or service" — it would not have qualified.
• No FWD, no settlement, no termination, no § 315(e)(2) estoppel, no CAFC appeal of a PTAB decision.

I could not fully render Google Patents' "Litigation" and "PTAB" sidebar panels from the fetched page text, so I am stating this as "no proceeding surfaced and the canonical ODP list is empty," not as an absolute negative that I verified character-by-character. If a defendant needs a belt-and-suspenders confirmation, the definitive check is a name/patent search in PTAB E2E (https://ptacts.uspto.gov/ptabweb/) and LexMachina/Docket Navigator for PTAB dockets, which run ahead of ODP ingest.

Patent identity (context for the absence)

• Patent: US 6,091,720 — "Dynamically controlled routing using dynamic management of intra-link traffic to virtual destination nodes"
• Inventors: François Bédard, Jean Regnier, France Caron
• Original assignee: Nortel Networks Corp / Northern Telecom Ltd (via Bell-Northern Research Ltd); current listed assignee Nortel Networks Ltd
• Priority: 1994-10-26 · PCT filed: 1995-10-26 (PCT/CA95/00600; WO96/13945) · Granted: 2000-07-18
• Family: Continuation-in-part of Ser. No. 08/329,716, now U.S. 5,526,414 ("Dynamically controlled routing using virtual nodes") — the '414 parent is the broader virtual-node disclosure; the '720 patent adds the dynamic intra-link traffic management (proportion/weight/completion-capability) subject matter in claims 5–15 and 22–27.
• Source of record: https://patents.google.com/patent/US6091720/en · https://www.freepatentsonline.com/[6091720](/patent/6091720).html

Strategic summary

Claim status: nothing is CANCELED, nothing is SUSTAINED through IPR, and the entire claim set is UNTESTED at the Board. Claims 1 and 16 are the independent claims (apparatus and method respectively), with dependents running through claim 27. No tribunal has ever adjudicated any of them. So a defendant gets no short-circuit — there is no FWD canceling claim 1 to hand a court, and correspondingly no estoppel estate to mine. The invalidity fight, if one were ever joined, would start from zero at the district court under clear-and-convincing evidence.

Estoppel landscape: none. § 315(e)(2) estops no one. Because no IPR/PGR reached a final written decision on this patent, there are no petitioners and no privies barred from raising § 102/§ 103 grounds on these claims. Every prior-art ground is still on the table — for whoever wants it. (Note the asymmetry: that cuts against a defendant too, because the patent owner has no adverse PTAB record to overcome either.)

Pattern signals: none. No repeat petitioner (no petitioner at all), no patent-owner PTAB-appeal aggressiveness (nothing to appeal), and no defensive aggregator (Unified Patents, RPX, etc.) has ever touched this patent. That silence is itself the signal the prompt asks about: well-asserted patents attract IPRs — this one was apparently never asserted hard enough post-2012 to draw a single petition. Combined with the 2014-10-26 expiration, the most likely explanation is that the patent was effectively dead weight in Nortel's portfolio well before the AIA trial regime mattered.

Recommended next steps

1. If you are facing a demand letter citing US 6,091,720: lead with expiration, not invalidity. The patent's term ended 2014-10-26 (Google Patents: "Expired – Fee Related"; anticipated expiration 2014-10-26). Under 35 U.S.C. § 271, there is no infringement of an expired patent, and § 286 caps the damages look-back at six years — which here ran out around 2020. A licensing demand premised on ongoing or recent infringement is meritless on its face; ask the sender to state the specific accused acts and dates and watch them fail to do so.
2. There is no FWD to cite. Because no proceeding exists, do not represent to a court or opposing counsel that any claim "has been canceled" or that any IPR "invalidated" this patent — that would be a sanctionable misstatement. The correct statement is: "No PTAB proceeding has ever been filed against US 6,091,720; the patent expired on 2014-10-26."
3. Confirm the negative before relying on it. Run the patent number through PTAB E2E (https://ptacts.uspto.gov/ptabweb/) and a commercial PTAB docket tool, and pull the USPTO Patent Center maintenance-fee / expiration record, so your "no PTAB activity + expired" position is documented rather than inferred.
4. If a live assertion somehow exists against pre-2020 conduct, treat it as an ordinary district-court invalidity case — § 282 clear-and-convincing burden, no PTAB estoppel, full § 102/§ 103 prior-art runway including the two references the patent itself distinguishes (U.S. 4,284,852; the Cameron/Hurtubise Telesis 1986 DCR article) and the sibling PCT/EP family art (WO96/13945, EP0789974). But exhaustion/expiration is the cheaper, faster out and should be the first move.

Confidence note: I have high confidence that no AIA trial proceeding is on file or publicly indexed for US 6,091,720 as of 2026-09-27 — the canonical ODP block is empty and independent web searches corroborate. I could not retrieve a full Google Patents "PTAB/Litigation" sidebar render, so if absolute certainty matters for a filing, verify via PTAB E2E as in step 3.

I'll research the assignment record for US 6,091,720 before writing up. Let me run several targeted searches.

Let me dig further for the assignment reel/frame records and any post-Nortel transfer.

Assignment & Ownership Analysis — US 6,091,720

Sourcing note (read first). I could not retrieve the USPTO Assignment Center abstract-of-title record for this patent. My tool access to assignmentcenter.uspto.gov / assignment.uspto.gov returned no direct record page for US 6,091,720, so I have no reel/frame numbers and no correspondent-of-record data for any link in this chain. The timeline below is built from the Google Patents legal-events block embedded in the authoritative full text provided for this patent (fetched 2026-09-27), which reproduces the recorded assignment events (type, assignor, assignee, date) but not the reel/frame or the filing correspondent. Where a field is missing I say so rather than guess. One illustrative Nortel chain-of-title from a different patent is discussed below and is explicitly flagged as not verified for 6,091,720.

Inventors

Pattern assessment. BNR was the research subsidiary of Northern Telecom (later Nortel). The chain inventors → BNR → Northern Telecom Ltd. is the standard BNR-originated invention protocol, not an unusual event. I found no evidence of inventors departing the assignee within 12 months of filing; I could not determine departure dates from the sources available, so the "inventor-flight precedes fire-sale" pattern is not assessable here (neither confirmed nor refuted).

Original assignee

• As issued (2000-07-18): Northern Telecom Limited, by then renamed Nortel Networks Limited (Google Patents lists "Original Assignee: Nortel Networks Corp"; the recorded events show the operative assignee at issue was Nortel Networks Limited following the 2000-08-30 change of name — the naming difference reflects the 1998–2000 renames, not a transfer).
• Primary line of business: Public telecommunications switching equipment. Nortel/Northern Telecom shipped the DMS-100/DMS-200 family of stored-program-control switches, and DCR (Dynamically Controlled Routing) was a real, deployed Nortel feature with a Network Processor — i.e., the assignee did ship product embodying the claimed subject matter. This is an operating-company patent, not a paper patent at grant.
• Current status: Bankrupt / in wind-down. Nortel filed for creditor protection in January 2009 (U.S. Chapter 11, Bankr. D. Del. No. 09-10138; Canadian CCAA proceedings) and liquidated its assets, including its patent portfolio, which was auctioned in 2011.

Assignment timeline

Every entry below is a recorded event per the Google Patents legal-events data for US 6,091,720. Reel/frame, execution date and correspondent were not retrievable through my access, so those fields are marked "not retrieved." (The Google Patents "Assigned to / Assignors" events are recording-date-level entries.)

• 1997-04-24 (recorded) — Reel not retrieved

  • Conveyance: Assignment of assignors' interest
  • Assignor: France Caron; François Bedard; Jean Regnier (inventors)
  • Assignee: Bell-Northern Research Ltd.
  • Correspondent: not retrieved — cannot assess recurrence.
  • Context: Initial inventor-to-employer assignment (standard BNR protocol).

• 1997-04-24 (recorded) — Reel not retrieved

  • Conveyance: Assignment of assignors' interest
  • Assignor: Bell-Northern Research Ltd.
  • Assignee: Northern Telecom Limited
  • Correspondent: not retrieved
  • Context: Internal corporate transfer (BNR research arm → operating parent).

• 1997-11-12 (recorded) — Reel not retrieved

  • Conveyance: Assignment of assignors' interest
  • Assignor: Bell-Northern Research Ltd.
  • Assignee: Northern Telecom Limited
  • Correspondent: not retrieved
  • Context: Internal re-recordation — appears to duplicate the 1997-04-24 BNR→Northern Telecom link. Whether this is a true duplicate recording, a gap/"corrective" re-recording, or a distinct reel is not determinable without the reel/frame detail. Flagging as an anomaly, not as a second transfer of ownership.

• 1999-12-02 (recorded) — Reel not retrieved

  • Conveyance: Change of name
  • Assignor: Northern Telecom Limited
  • Assignee: Nortel Networks Corporation
  • Correspondent: not retrieved
  • Context: Change of name only (Northern Telecom → Nortel Networks).

• 1999-12-23 (recorded) — Reel not retrieved

  • Conveyance: Change of name
  • Assignor: Northern Telecom Limited
  • Assignee: Nortel Networks Corporation
  • Correspondent: not retrieved
  • Context: Change of name only — apparent duplicate of the 1999-12-02 entry; same non-determinable-duplicate caveat as above.

• 2000-08-30 (recorded) — Reel not retrieved

  • Conveyance: Change of name
  • Assignor: Nortel Networks Corporation
  • Assignee: Nortel Networks Limited
  • Correspondent: not retrieved
  • Context: Change of name only.

There is no recorded post-2000 event in the authoritative legal-events data for this patent. In particular, the legal-events block shows no assignment of US 6,091,720 to Rockstar Bidco LP, Rockstar Consortium US LP, Rockstar Technologies LLC, Constellation Technologies LLC, Bockstar Technologies LLC, or RPX Clearinghouse LLC, and Google Patents still lists the current assignee as Nortel Networks Ltd.

Important cross-reference (do not misattribute). In an unrelated IPR (IPR2014-01192, Bockstar Technologies LLC, concerning US 6,069,895 — a different patent), the patent owner recited the generic Nortel chain-of-title reels: 010567/0001 (Northern Telecom→Nortel Networks Corp), 101626/0654 (same), 011195/0706 (Nortel Networks Corp→Nortel Networks Ltd), 027164/0356 (Nortel Networks Ltd→Rockstar Bidco LP), 030094/0370 (Rockstar Bidco→Rockstar Consortium US LP), 031761/0016 and 032399/0116 (Rockstar Consortium→Rockstar Technologies LLC), then onward to RPX Clearinghouse. This is the pattern that Nortel's 2011 bankruptcy sale and the 2014 RPX purchase followed, but I have not verified that any of these reels cover US 6,091,720, and the absence of a Rockstar-recording event in this patent's own legal events is affirmative (if weak) evidence that it may have been excluded from, or handled differently in, that sale. I am therefore not attributing these reels to 6,091,720.

Timeline diagram

timeline
    title Ownership of US 6091720
    1994 : Priority application filed
         : Inventors at Bell Northern Research
    1995 : PCT application filed
    1997 : Inventors assign to Bell Northern Research Ltd
         : Bell Northern assigns to Northern Telecom Ltd
    1999 : Northern Telecom renamed Nortel Networks Corp
    2000 : Patent issued on Jul 18
         : Renamed Nortel Networks Limited
    2009 : Nortel enters bankruptcy protection
    2011 : Nortel portfolio sold at auction

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. The only recorded transfers are internal (inventors→BNR, BNR→Northern Telecom) plus two changes of name. No licensing-only LLC appears in the recorded chain for this patent.

2. Known asserter in the chain — Unclear. Rockstar Consortium US LP and its progeny (Rockstar Technologies, Constellation, Bockstar) are public privateering vehicles that asserted Nortel patents, and RPX Clearinghouse is a defensive aggregator. But no recorded assignment of 6,091,720 to any of them is present in the authoritative legal-events data, and Google Patents lists Nortel Networks Ltd as current assignee. I cannot place a known asserter in this patent's chain on the evidence available.

3. Repeat correspondent across the chain — Unclear / not assessable. Correspondents of record were not retrieved for any link, so I cannot test recurrence. This is a data limitation, not a negative finding — the signal simply cannot be evaluated.

4. Cascading transfers — Not present (as recorded). The chain shows no run of consecutive post-issuance assignments through chained LLCs. The 1997 and 1999 paired entries look like duplicate/re-recordation events, not distinct cascading transfers.

5. Pre-litigation transfer — Not present / not applicable. No infringement suit naming this patent surfaced, and no assignment dated within 6 months of any such suit exists in the record I could obtain.

6. Bankruptcy fire-sale — Present as to the original assignee; unclear as to this asset. Nortel's Chapter 11/CCAA proceedings (2009) and the 2011 auction of its patent portfolio to Rockstar ($4.5B) are established facts. Whether US 6,091,720 was in the sold estate is not verified — the patent's recorded legal events stop in 2000.

7. Privateering — Unclear. The Rockstar Consortium was a textbook privateering structure (Apple/Microsoft/RIM/Ericsson/Sony/Sony buying a bankrupt operating company's patents to assert against Google/Android and Cisco customers). But without a reel/frame tying this patent to Rockstar, I cannot call the signal present for 6,091,720.

8. Defensive aggregator (anti-NPE) — Unclear. RPX Clearinghouse acquired Rockstar's remaining assets in December 2014. If this patent was among the RPX-purchased tranche, the chain would terminate non-assertingly. That is not verified here.

Verdict

Insufficient data.

The only ownership events I can verify for US 6,091,720 are the 1997 inventor→Bell-Northern Research and Bell-Northern Research→Northern Telecom Limited assignments plus the 1999 and 2000 change-of-name entries ending at Nortel Networks Limited; there is no recorded transfer to any NPE or defensive aggregator. That is consistent with a patent that simply remained in the Nortel estate and was disposed of — if at all — in proceedings that did not produce a discrete recorded assignment I can cite. Because I could not retrieve reel/frame numbers, correspondents, or any Rockstar/RPX record for this specific patent, I cannot responsibly classify it as NPE-driven, defensively aggregated, or operating-company-asserted. (Context worth stating plainly: the original assignee was a genuine operating company that did ship DCR switches, and it later went bankrupt — a fact pattern that often feeds NPE chains, but "often" is not evidence for this patent.)

Verify at: USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (search patent number 6091720) and the Google Patents legal-events tab — https://patents.google.com/patent/US6091720/en (which is where the dated events above come from and which currently shows current assignee = Nortel Networks Ltd).

Caveats on internal consistency

• No contradiction with the previously generated summary; the "Assignee (as granted)" line there (Northern Telecom Limited / Nortel Networks) is consistent with the recorded events above.
• The duplicate-dated entries (two 1997-04-24 events; two 1999-12-02/23 change-of-name events) are flagged as anomalies. I have not established whether they are duplicate recordings or distinct reels — that determination requires the reel/frame data I could not obtain.
• I did not fabricate any reel/frame number. Where the task's template asks for one and I lack it, I marked it "not retrieved."

I'll research the prior art citations for US 6,091,720. Let me run several targeted searches.

I have the full cited-reference list. Now let me research each reference to describe it accurately and assess relevance.

Prior-Art Analysis — US 6,091,720 ("Dynamically Controlled Routing Using Dynamic Management of Intra-Link Traffic to Virtual Destination Nodes")

A. Sourcing note and method (read this first)

I retrieved the patent's own front-page "References Cited" list from two independent reproductions that agree:

• Google Patents, US6091720A — https://patents.google.com/patent/US6091720
• Justia Patents, US 6,091,720 — https://patents.justia.com/patent/[6091720](/patent/6091720) (and the USPTO-printed PDF at patentimages.storage.googleapis.com/.../US6091720.pdf)

Important honesty caveats, stated up front:

1. The instruction asked me to search the USPTO database. I could not open an authenticated PatentCenter/PAIR "References Cited" view in this session. The reference list below is the one printed on the patent's own face and reproduced by Google/Justia/FPO. That is authoritative for what was cited, but it does not tell me the examiner's category tags (…cited by examiner vs. cited by applicant) — the sources I retrieved do not preserve that distinction.
2. I hit my search/tool budget partway through reference-by-reference verification. I obtained solid descriptive detail for US 4,284,852, US 4,669,113, and US 4,788,721. For several of the later references I could not retrieve a verified abstract in this session, and I will not invent one — those are explicitly flagged "not verified."
3. All references below are cited on the face of US 6,091,720. Because none of them discloses a "virtual destination node," none of them anticipates independent claim 1 or independent claim 16 as a whole (explained in Section D). They are relevant chiefly to the preamble and to the dependent claims.

The full claim set runs to 30 claims as printed (claim 1 independent apparatus, claim 16 independent method), which is a correction/refinement of the "27 claims" figure in the earlier-generated summary — see the flag at the end.

B. Complete cited-reference list (as printed on the patent)

Non-patent literature also cited on the face (all DCR/DNHR foundational papers):

• N1. Cameron & Hurtubise, "Dynamically Controlled Routing," Telesis, 1986, pp. 33–37 (Bell-Northern Research). (This is also the article the patent's own Background cites for "a general discussion of FHR and DCR networks.")
• N2. Régnier & Cameron, "State-Dependent Dynamic Traffic Management for Telephone Networks," IEEE Communications Magazine, Oct. 1990, pp. 42–53.
• N3. Ash, Cardwell & Murray, "Design and Optimization of Networks With Dynamic Routing," Bell System Technical Journal, Vol. 60, No. 8, Oct. 1981, pp. 1787–1820.
• N4. Ash, Kafker & Krishnan, "Servicing and Real-Time Control of Networks With Dynamic Routing," Bell System Technical Journal, Vol. 60, No. 8, Oct. 1981, pp. 1821–1845.
• N5. Coan et al., "A Distributed Protocol to Improve the Survivability of Trunk Networks," International Switching Symposium, Session C6, Paper 2, Vol. 4, May 28, 1990, Stockholm, SE, pp. 173–179, XP 000130915.

Note the discrepancy in the patent body text itself: the incorporated-by-reference Regnier/Cameron article is described in the specification as "IEEE Communications, November 1991," while the face citation renders it as IEEE Communications Magazine, Oct. 1990. Same authors, two different issue attributions — I flag it rather than silently correcting it, per the operating rules.

C. Reference-by-reference analysis

1. US 4,284,852 — Szybicki et al., "Alternate routing for a telephone system," Aug. 18, 1981 (Northern Telecom Ltd.)

Status: verified. Source: Google Patents / SumoBrain full text.

• What it discloses: Switching offices are grouped in clusters, each office having direct trunks to the others so each office can act as its own tandem. A logic device ("suitable equipment") monitors the busy status of the offices and trunk groups, determines the most likely alternate route for each office, stores it at that office, and periodically updates it (the specification gives 5–15 second update cycles). Claim 4 selects the alternate route by the maximum of min(Mop−2, Mpt−2) across candidate tandem offices; claim 5 selects the alternate route "according to a random method, the probability of which route is to be chosen is based upon the positive R values," where R depends on remaining idle trunks and a term for idle trunks "needed for other than alternately routed calls."
• Significance to '720: This is the reference the '720 specification itself cites as "an early version of dynamically controlled routing." It is the closest structural ancestor of the DCR concept.
• §102 relevance — potential anticipation of, at most:
  • the generic alternate-routing preamble of claim 1 / claim 16 (direct first, then a recommended transit/tandem office);
  • the periodic-update feature relied on by claim 2 (network processor / logic device periodically refreshing transit-node data);
  • the weighted-random route-selection step of claim 1(step iv) — claim 5 of '852 uses probability-of-selection proportional to an availability-derived quantity R.
• Not anticipatory of claims 1 or 16 as a whole: it has no virtual destination node, no notion of a destination representing a group of two or more physical components, and no "set S of non-zero-proportion circuit groups → weighted random pick → remove-on-no-idle → repeat." It also has no per-circuit-group "specified proportion" stored at the switch for a multi-circuit-group link to a single destination logic entity.

2. US 4,669,113 — Ash et al., "Integrated network controller for a dynamic nonhierarchical routing switching network," May 26, 1987 (AT&T Bell Labs)

Status: verified. Source: Google Patents / lexdana.ai / SumoBrain.

• What it discloses: A non-hierarchical (DNHR-type) network with an Integrated Network Controller (INC) that (a) computes first-choice and subsequent-choice routing sequences per origin-terminating switch pair, (b) gathers traffic and idle-trunk information, and (c) issues near-real-time "least-loaded-path" updates to the switches. Its disclosed route-update process (Figs. 7–8) computes a reservation level (trunk reservation) for each trunk group in each link, discounts idle trunks, computes path capacity, and selects/installs least-loaded paths.
• §102 relevance — potential anticipation of the dependent claims that import network-processor / reservation machinery:
  • Claim 2 (network processor coupled to all switching elements via a data network, periodically receiving local network-condition information and returning recommended transit nodes) — '113's INC does exactly this functionally (INC, data network, periodic idle-trunk/least-loaded updates).
  • Claim 3 (recommendations take account of full availability of links) — the least-loaded-path computation is an availability-based selection.
  • Claims 4–5 (protective allowance / reservation value computed per circuit group; safe idle circuits; SIC-based recommendations) — '113's trunk-reservation level per trunk group is the same genus of mechanism the '720 specification calls its "protective allowance." This is the single closest anticipation candidate for the SIC/reservation dependent claims (4, 5, and the corresponding method claims).
• Not anticipatory of claims 1 / 16: no virtual destination node; routing is switch/trunk-group based, not "origin node → virtual destination node whose link is the set of circuit groups to its components," and no "specified proportion per circuit group of a single link" distribution algorithm.

3. US 4,788,721 — Krishnan et al., "Routing of network traffic," Nov. 29, 1988 (Bell Communications Research, Inc.)

Status: verified. Source: Google Patents / FPO / SumoBrain.

• What it discloses: State-dependent, separable routing — generating sets of routes (routes of at most two trunk groups between a switch and each other switch), computing occupancy factors from network configuration, past/present traffic, and estimates of future blocking, and routing a call over the least-occupancy route below a threshold, else blocking. Uses "policy-iteration" occupancy factors.
• §102 relevance: directed to the alternate-route selection / blocking-avoidance preamble of claim 1 and claim 16; illustrates the two-link alternate-route model that '720's FIG. 3 assumes. Not anticipatory of claims 1 / 16 (no virtual destination, no proportion-based intra-link distribution).

4. US 5,526,414 — Bedard et al., "Dynamically controlled routing…," Jun. 11, 1996

Status: identified as the parent, not verified as to content independently.

• The '720 specification states: "This application is a 371 of PCT/CA95/00600 filed Oct. 26, 1995 which is a c-i-p of application Ser. No. 08/329,716 filed Oct. 26, 1994 now U.S. Pat. No. 5,526,414." So '414 is the priority/parent application of '720, by the same inventor group and assignee lineage.
• §102 relevance: it is the natural §102 subject matter overlap (same disclosure family), but it is not anticipatory prior art to '720 in the substantive sense because it is the same inventive entity's own earlier work forming the CIP priority chain. Its citation is procedural/family-driven rather than a hostile-art citation. I did not independently read '414's claims in this session, so I will not assert what '720 limitations it discloses.

5–7, 9–10. US 5,142,570 (Chaudhary); US 5,297,137 (Ofek et al.); US 5,311,585 (Armstrong et al.); US 5,377,262 (Bales et al.); US 5,844,981 (Pitchford et al.); US 5,898,673 (Riggan et al.)

Status: NOT VERIFIED in this session. My searches for these numbers returned other documents (including unrelated patents sharing suffix patterns, and several PTAB petitions for different patents), and I ran out of search budget before confirming each one's subject matter. I decline to fabricate abstracts or §102 mappings for them.

What I can say with confidence from the face of '720 alone:

• US 5,377,262 (Dec. 27, 1994) and US 5,844,981 (Dec. 1, 1998) and US 5,898,673 (Apr. 27, 1999) are dated after the Oct. 26, 1994 priority date and (for the latter two) even after the Oct. 26, 1995 PCT filing. If they are properly cited art, they would have to qualify as §102(e) art (US applications filed before the relevant '720 date) — not as §102(a)/(b) printed publications. Whoever validates anticipation must confirm their filing dates.
• US 5,142,570 (Aug. 25, 1992), US 5,297,137 (Mar. 22, 1994), US 5,311,585 (May 10, 1994), and US 5,377,262 (Dec. 27, 1994) all predate the Oct. 26, 1994 priority date and are therefore potential §102(a)/(b) art on timing alone.

Recommended next step to close this gap: open the PatentCenter / USPTO "References Cited" view for 6,091,720 and read the examiner's classification for each of items 4–7, 9–10 (e.g., "2.1.1" examiner-cited vs. applicant-cited), then pull each reference's abstract from its own front page. I was unable to complete that here.

11–12. EP 0 372 270 (June 1990) and EP 0 538 853 (April 1993)

Status: NOT VERIFIED. Both publication dates precede the '720 priority date, so both are potential §102(a)/(b) art on timing. EP 0 372 270 (June 1990) is contemporaneous with the Szybicki/AT&T dynamic-routing literature; EP 0 538 853 (April 1993) sits in the same window as the AT&T real-time-network-routing work (cf. EP 0 449 480, "Real-time network routing," published Oct. 2, 1991, which explicitly discusses 2-link route selection and per-trunk-group reservation thresholds). I flag EP 0 449 480 only as context — it is not a cited reference of '720 and I am not asserting it as such. I did not retrieve the contents of EP 0 372 270 or EP 0 538 853 and will not characterize them further.

N1–N5. Non-patent literature

• N1 (Telesis 1986, Cameron & Hurtubise, "Dynamically Controlled Routing") — the patent's own Background cites this as the general DCR discussion. Anticipates only the DCR context/preamble, not the virtual-destination-node invention.
• N2 (Régnier & Cameron, IEEE Comm. Mag., Oct. 1990) — state-dependent dynamic traffic management; the '720 specification expressly incorporates this by reference for dynamic protective allowances. Relevant to claim 4's PA/SIC limitations; not to the virtual-destination-node core.
• N3 & N4 (Ash et al., BSTJ Vol. 60 No. 8, Oct. 1981) — the foundational DNHR design and real-time-control papers (same family as US 4,669,113). Relevant background for dynamic routing with central control; N3/N4 predate the priority date and are potential §102(b) art for the network-processor/alternate-route aspects.
• N5 (Coan et al., ISS 1990) — distributed protocol for trunk-network survivability; squarely on point for the survivability motivation recited in '720's Background (the "Unique Exit Gateway" failover problem), but not for the claimed structure.

D. Overall §102 conclusion for the independent claims

Claim 1 (apparatus) and claim 16 (method) are not anticipated by any reference of record. The reason is that anticipation under 35 U.S.C. § 102 requires a single reference disclosing every limitation, and no cited reference discloses the combination that defines the invention:

1. a virtual destination node representing a group of two or more components, each a distinct physical network element, in the switch's destination-node listing;
2. a link to that virtual destination node defined as the set of circuit groups to all its components;
3. a specified proportion stored per circuit group of that multi-circuit-group link; and
4. the set-S algorithm — build S = {circuit groups with non-zero proportion}; test empty → overflow; else weighted-random selection; attempt; if no idle circuit, remove from S; repeat until carried or S exhausted.

The closest items of record (US 4,284,852's weighted-random tandem choice and periodic updates; US 4,669,113's central controller with per-trunk-group reservations and least-loaded updates; US 4,788,721's state-dependent two-link routing) supply at most single limitations and are properly cited as §102 art against the dependent claims and as §103 art in combination — not as anticipatory art against claims 1 or 16.

Where §102 anticipation is most plausibly arguable (dependent claims only)

E. Ranking of most relevant prior art of record

1. US 4,669,113 (Ash/Oliver, AT&T Bell Labs, 1987) — closest functional match to the network-processor + reservation/SIC dependent claims.
2. US 4,284,852 (Szybicki, Northern Telecom, 1981) — the acknowledged "early DCR" ancestor; source of periodic-update and weighted-random-selection concepts.
3. US 4,788,721 (Krishnan et al., Bellcore, 1988) — state-dependent two-link alternate routing; closest to the preamble.
4. US 5,526,414 (Bedard et al., 1996) — the CIP parent; family/priority overlap, not hostile art.
   5–8. The remaining US patents and the two EP documents — unassessed here; must be verified before any §102 assertion.

F. Caveats and corrections to flag

• Claim-count correction: the earlier-generated summary stated "27 claims total." The printed claim text I retrieved shows dependent claims numbering well past 27 (claim 27, claim 28, claim 29, claim 30 all appear in the Justia reproduction of the claim set). The correct total appears to be 30 claims, with claim 1 independent (apparatus) and claim 16 independent (method). I flag this as a contradiction with the prior section rather than silently overriding it.
• Date discrepancy, not corrected: US 4,788,721 is rendered as "November 1988" on the Justia face list and as issued Nov. 29, 1988 in corroborating sources. I preserve both.
• Reference-category gap: I could not confirm which citations were examiner-cited vs. applicant-cited for '720. This matters for assessing the strength of the record and should be resolved via PatentCenter.
• Unverified references: items 4–7, 9–12 (including both EP documents) were not content-verified in this session. Any §102 mapping for them here would be speculation, so I have deliberately supplied none.
• No invalidity/litigation dimension asserted: as noted in the earlier litigation section, I found no public assertion or PTAB proceeding involving '720, and nothing in this prior-art review changes that.

I'll ground this obviousness analysis in the actual cited prior art for US 6,091,720. Let me pull the reference lists.

Good — that confirms the foundational reference (US 4,284,852, Szyloki et al., Northern Telecom). Let me pull the parent patent and the cited-reference list.

I now have the full "References Cited" list from the patent front page. Let me characterize the key cited references.

I hit the tool-use cap mid-verification, so this analysis rests on (a) the authoritative full text you supplied, (b) the References Cited list I pulled from the patent's printed front page, and (c) the corroborating EP counterpart. I flag explicitly below where I could not verify a reference's disclosure.

Obviousness Analysis — US 6,091,720 under 35 U.S.C. § 103

0. Two contradictions to flag first (per your cross-reference instruction)

1. Claim count. The printed front page of US 6,091,720 (patentimages PDF) states "30 Claims, 5 Drawing Sheets." The previously generated Patent summary section states "27 claims total," with claim 16 as the sole independent method claim. These conflict. I did not read the complete printed claim set end-to-end; treat the "27" figure as unverified and the "30" figure as the front-page recital. This matters to the analysis below because the dependents beyond the ones I can verify are where the strongest §103 art sits.
2. Continuation vs. CIP. The front page says "[63] Continuation of application No. 08/329,716, Oct. 26, 1994, Pat. No. 5,526,414," while the specification text says the PCT application "is a c-i-p of application Ser. No. 08/329,716." A continuation and a CIP have different § 120/priority consequences, and this directly affects which references qualify as prior art (§ 3 below). The inconsistency is in the document itself.

Also note a minor citation inaccuracy: the specification cites Régnier & Cameron as "IEEE Communications, November 1991," but the front page lists it as "IEEE Communications Magazine Oct. 1990 pp. 42–53" (and EP 0 789 974 agrees: vol. 28, no. 10, Oct. 1990). The 1990 date is correct.

1. The prior art actually on the face of this patent ("Prior Art section")

From the printed front page (https://patentimages.storage.googleapis.com/78/ec/22/57859353fbf495/US6091720.pdf), cross-checked against EP 0 789 974 B1 (https://patentimages.storage.googleapis.com/d9/68/9a/55c5a908b0cd29/EP0789974B1.pdf):

US patents cited

Foreign

• EP 0 372 270 (6/1990), H04Q 3/00
• EP 0 538 853 (4/1993), H04Q 3/00

Other publications

• Cameron & Hurtubise, "Dynamically Controlled Routing," Telesis, Vol. 1, 1986, pp. 33–37.
• Régnier & Cameron, "State-Dependent Dynamic Traffic Management for Telephone Networks," IEEE Communications Magazine, Oct. 1990, pp. 42–53.
• Ash, Cardwell & Murray, "Design and Optimization of Networks With Dynamic Routing," BSTJ, Vol. 60, No. 8, Oct. 1981, pp. 1787–1820.
• Ash, Kafker & Krishnan, "Servicing and Real-Time Control of Networks With Dynamic Routing," BSTJ, Vol. 60, No. 8, Oct. 1981, pp. 1821–1845.
• Coan et al., "A Distributed Protocol to Improve the Survivability of Trunk Networks," ISS, Session C6, Paper 2, Vol. 4, 28 May 1990, Stockholm, pp. 173–179, XP 000130915.

Verified content of the two key references:

• US 4,284,852 (Szylöcki et al.) — DCR "Alternate Routing for a Telephone System." Switching offices joined by trunk groups; switching-office storage device 54 holding route data addressed by destination; central logic device 39 (the network-processor ancestor) reached over data links 53; periodic transfer of updated alternate-route data; alternate-tandem selection by M_c = min(M_op, M_pt) − Z; and — critically — a parameter X = "the expected number of idle trunk lines needed … for other than alternately routed calls," predeterminable manually or "determined automatically from actual traffic parameters." (https://patents.google.com/patent/US4284852, https://lexdana.ai/patent/4284852)
• US 5,526,414 (Bedard et al., the parent) — expressly discloses "each switching element may include specified proportions for those circuit groups and, when attempting to route a call via the link to the virtual node, the switching element may attempt the circuit groups randomly and in dependence upon the specified proportions." (https://patents.google.com/patent/US5526414)

I additionally confirmed a corroborating DCR reference not on the '720 face: US 5,295,183, "Congestion control system for telecommunications," Northern Telecom Limited, filed 1991-11-21, issued 1994-03-15, which recites the DCR network processor, direct/alternate trunk groups, the periodic 5–15 s update, and a per-trunk-group "expected number of idle trunk lines needed … for other than alternately routed calls."

2. Level of ordinary skill and the claim-1 delta

PHOSITA (as of 1994/1995): an engineer with an EE/CS degree and ~2–4 years in stored-program-controlled telephony switching (CCS7/SS7 call processing) and dynamic/non-hierarchical routing — i.e., someone fluent in DCR (Northern Telecom), DNHR (AT&T), and DAR (BT).

Decomposing claim 1 (and its method twin):

Delta = F + (G/H formalized as a weighted no-replacement hunt). Everything else is the admitted DCR art.

3. Threshold problem: the parent '414 is not § 103 prior art

The examiner listed US 5,526,414 under "References Cited," but it cannot be used for obviousness:

• Not § 102(a)/(e) art — it shares the same inventive entity (Bédard, Régnier, Caron) and the same family; it is not "by another."
• Not § 102(b) art — it issued 6/11/1996, after both the 10/26/1995 PCT filing and the 4/24/1997 § 371 date. The one-year bar never ran.

So the single reference that discloses F, G and H on the face of the file is unavailable, and the § 103 case must be built from the other listed art. That is a real hurdle, and I want to be candid: on the record I verified, claim 1's virtual-destination-node limitation is the hardest element to reach.

4. The obviousness combinations

Combination 1 — Claims 2, 3, 4 and the PA/reservation dependents: very strong

US 4,284,852 (Szylöcki) + Régnier & Cameron, IEEE Comm. Mag. Oct. 1990 (+ Ash BSTJ 1981).

• '852 supplies the NP, the data links, the per-office route store, periodic updates, and the X reservation for direct traffic.
• Régnier & Cameron supplies exactly what the '720's own specification points to for dynamic protective allowances — the '720 incorporates this paper by reference and concedes: "The protective allowance can be dynamic. For details of dynamic protective allowances, the reader is directed to [Cameron ICC 1981] and [Régnier & Cameron, IEEE Communications]." That is an admission that the dynamic-PA subject matter of claim 4 (and the SIC computation) is prior art.
• Motivation: identical problem — protect direct traffic, deflect overflow, prevent cascade blocking; same field; both directed to the same measurement/reporting cycle. Result predictable (higher completion rate). Claims 2 and 4 are, on this record, close to § 102 for claim 4's PA/SIC concept.

Combination 2 — Claim 1 / claim 16 core: moderate–strong, contingent

US 4,284,852 + Cameron/Hurtubise Telesis 1986 + Coan et al. ISS 1990 + [a multi-trunk-group distribution reference from the cited list — US 5,297,137 (Ofek), US 5,142,570 (Chaudhary), US 5,377,262 (Bales), US 5,311,585 (Armstrong), or EP 0 372 270 / EP 0 538 853].

Argument chain:

1. Virtual destination node (F). Once DCR is modeled node-and-link rather than switch-and-trunk-group ('852; Telesis 1986), treating a destination code as an abstraction — homed to a route list / trunk-group aggregate spanning several switches — is ordinary telephony translation practice, not an invention. The "Unique Exit Gateway" the patent attacks is a policy, not a technical constraint. Coan et al. is the motivator: it is expressly about improving the survivability of trunk networks around node failure — precisely the '720's stated problem ("congestion or failure at its switch would result in failure to complete the call"). A POSITA seeking survivable egress would obviously distribute a code's traffic over multiple exit switches.
2. Proportional / weighted random distribution (G/H). Distributing a route list's traffic across member trunk groups by assigned percentages is a stock SPC-switch traffic-engineering function; randomizing attempt order is a known anti-bias measure; "remove the failed group and retry" is textbook trunk hunting with overflow.
3. KSR killer admission. The specification itself states: "Other traffic distribution algorithms can be devised to distribute calls according to the proportions. For example 'round robin' techniques could be used." That is a judicial admission that the specific selection mechanism is "a finite number of identified, predictable solutions" — the KSR fact pattern (KSR Int'l v. Teleflex, 550 U.S. 398 (2007)).

Strongest form of this combination would be a single reference disclosing multi-switch destination grouping. The EP 0 372 270 / EP 0 538 853 / US 5,311,585 trio is where I would look first — the EP examiner carried all three forward into the EP search report alongside '852, which signals they were considered material. I could not retrieve or verify their disclosures in this session, so I have not asserted what they teach.

Combination 3 — Dynamic/centralized proportions and "completion capability": strong

US 4,284,852 + Régnier & Cameron 1990 + Coan et al. 1990 + routine arithmetic.

• '852 already teaches the NP gathering per-trunk idleness from all offices and rewriting route tables on a cycle; Régnier & Cameron teaches dynamic, state-dependent recomputation of reservations; Coan teaches per-node status exchange for survivability.
• The "completion capability" measure is nothing more than a per-component idle-capacity scalar (the '720's own worked example is literally "the total number of idle circuits"). Feeding a monotone idle-capacity scalar into a weight, summing weights, and normalizing to 100% is arithmetic. Motivation: load-balance overflow toward the exit with the most spare capacity, and blend updates (the PWF exponential filter) to damp oscillation — a recognized problem in the art (the Internet-RFC literature flags dynamic metrics causing "traffic magnets"/oscillation).

Combination 4 — Distributed (switch-side) updating via RWC monitoring: strong

US 4,284,852 + Telesis 1986 + the CCS7 RWC message as known signalling + routine arithmetic.

• '852 and Telesis have the switches measuring and reporting overflows already; the '720 merely moves the arithmetic to the switch. Release-With-Cause is a standard CCS7 ISUP primitive, and the '720 itself tells you the design rationale: "the alternative procedure … is simpler … and may yield cost savings because the switches do not need to communicate with the network processor." A POSITA optimizing signalling load would obviously move the computation to where the data is.

5. Effective-date traps (which references even qualify)

Because of the continuation-vs-CIP contradiction (§ 0):

• If a given claim is supported by the '414 disclosure (which does recite proportions + random selection — verified above), it may reach 10/26/1994. Then US 5,377,262 (issued 12/1994) and US 5,295,183 (issued 3/1994) are not § 102(b) art, and § 102(a)/(e) treatment turns on inventorship.
• If a claim depends on CIP-added matter (the weighting formulas, completion capability, the LASTCG/LASTOVF/CGCTR algorithm), its date is 10/26/1995, and references published in the Oct. 1994–Oct. 1995 window become § 102(b)/(e) candidates.
• US 5,844,981 (12/1998) and US 5,898,673 (4/1999) were cited by the examiner despite post-dating the '720 filing — that citation pattern implies they were treated as pre-AIA § 102(e) art (application filed before the '720's date, patent granted after). That is worth confirming if a validity opinion is ever papered.

6. Secondary considerations (Graham factor 4) — essentially absent

• No evidence of unexpected results, copying, or a licensing program with a nexus to the CIP limitations.
• Any commercial success of Nortel DCR accrues to the family ('852 / '414), not to the weighted-selection loop; the required nexus would be weak.
• The previously generated sections confirm no litigation and no PTAB record — so there is no adjudicated secondary-considerations record either way, and no § 315(e)(2) estoppel constraining the art a challenger may use.

7. Bottom line

The honest weak link is the virtual-destination-node limitation in claim 1 — the only reference on the face of the patent that clearly discloses it is the parent '414, which is barred as prior art by same-inventorship and its post-filing issue date. A challenger either (i) finds the multi-switch-destination grouping in one of the ten references I could not verify (EP 0372270, EP 0538853, US 5,311,585 and US 5,377,262 are the four best candidates given their class and the EP examiner's carry-forward), or (ii) proves it as the routine aggregation of multiple exit gateways — supported by Coan's survivability motivation and by the applicant's own "round robin" admission. I would not represent that a complete § 103 case on claim 1 is established on the record I retrieved; I would represent that the dependent claims and the PA/SIC subject matter are very vulnerable.