US patent 6,188,756 (‘756) -- “Efficient communication through networks.” This patent describes routing a communication between a calling party and a called party through a central control location, selecting the “best” path based on a particular criterion.

Claim for which is

  1. A method of use of a communication network, comprising the steps of:

(a) receiving a calling party access number and a called party access number at a control location;

(b) determininng which service providers service connections between said calling party access number and said called party access number;

(c) comparing said service providers based on criteria;

(d) selecting appropriate ones of said service providers that satisfy said criteria as a result of the step of comparing;

(e) instructing said selected service providers to provide service between said connections for establishing contact between said calling party access number and said called party access number;

(f) receiving a status signal at said control location indicating if said called party access number is available for taking an incoming communication;

(g) if said status signal indicates an available status, initiating a first communication from said control location to said called party access number and a second communication from said control location to said calling party access number;

(h) bridging said first and second communications.

Have you seen anything that was published before October 11th, 1994 that discusses claim 1.

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3 Answers 3


The Routing Informatino Protocol (RIP) [1] that is used to analyze a distribution network, cope with change and find the best routes seems close. The original specification [2] for the protocol itself is from 1988.

And I suppose the Romans already chose the faster runners over the slower runners when delivering messages, which qualifies for half the points in the claim.

[1] https://en.wikipedia.org/wiki/Routing_Information_Protocol
[2] https://www.rfc-editor.org/rfc/rfc1058

  • The specification doesn't clearly talk about "(f) receiving a status signal at said control location indicating if said called party access number is available for taking an incoming communication;" That needs to be checked I think.
    – Zero
    Commented Jul 30, 2013 at 16:06

This sounds like a TokenRing - Ethernet bridge. I used to buy them from Nortel in 1995ish, though I imagine they were some years older.

Bridging is a method of communicating between devices at OSI layer 2, the data link layer. A bridge connects two networks together and acts as a traffic director. If traffic is destined to the other network, the bridge allows the traffic to pass. If the traffic is local to a single network, the bridge does not pass the traffic unnecessarily to the other connected network.

The bridge makes this determination based on the Media Access Control (MAC) address of the workstations on the network. The bridge keeps an updated list of everyone active on the network, and uses this list to direct traffic from one network to another.

Read more: http://stason.org/TULARC/networking/lans-token-ring/3-2-What-is-used-to-convert-between-Ethernet-and-Token-Ring.html#.UfhLe2RUr4A#ixzz2aZgL4GiA


This also sounds like what is called "Automated Callback" in Federal Standard 1037C

Date of Publication: August 7, 1996

So it's too late, but I bet the NTIA didn't invent the idea. They don't cite any references :(

automatic callback: A service feature that permits a user, when encountering a busy condition, to instruct the system to retain the called and calling numbers and to establish the call when there is an available line. Note 1: Automatic callback may be implemented in the terminal, in the switching system, or shared between them. Note 2: Automatic callback is not the same as camp-on.

The Wikipedia page for Automated Callback lists several systems which implemented the feature, but no dates or citations.

edit: this assumes the automatic callback feature is implemented in the PBX which then satisfies the other parts of the claim regarding provider routing

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