Method for building-up of routing addresses in a digital telecommunication network

A method of building-up a routing address for transmission of digitally addressed packets from a first to a second subscriber's station of a transmission network having a plurality of switching nodes,

• there being a plurality of subscriber's stations, including said first and second subscriber's stations, and
• a plurality of lines connecting each switching node to at least one other switching node and each subscriber's station to one switching node, routing words being individually assigned to the lines, all routing words assigned to those lines which are connected to the same switching node being distinguishable from each other;
• the subscriber's stations having individual call-numbers distinguishable from each other but without an indication of the switching node to which the respective subscriber's station is connected,
• the method comprising the steps of:
• (1) transmitting from the first subscriber's station to the switching node connected to it a build-up packet including the call-number of at least the second subscriber's station and the routing word assigned to the line which connects the first subscriber's station to the said switching node;
• (2) receiving the said build-up packet incoming at the said switching node and retransmitting it to all other switching nodes and to all subscriber's station connected to said switching node, and
• continuing such receiving and retransmitting at each of said other switching nodes and from all further switching nodes to which retransmitted build-up packets arrive;
• (3) before each of said retransmissions adding to the received build-up packet the routing word assigned to the line to which the received build-up packet is retransmitted.
• thereby obtaining and retransmitting along different routes of the network an increasing number of different build-up packets each containing the call-number of the second subscriber's station and a build-up routing address consisting of the sequence of the routing words assigned to the lines successively passed along the respective route by each respective build-up packet, the lengths of the routing addresses increasing from switching node to switching node along the routes;
• (4) excluding from said retransmissions build-up packets exceeding a predetermined packet length corresponding to a route length which is sufficient for transmission from any subscriber's station to any other subscriber's station of the network;
• (5) comparing at each subscriber's station the second subscriber's call-number of each incoming build-up packet with the call-number of the respective subscriber's station and, when the compared call-numbers are identical, receiving the incoming build-up packet received by the second subscriber's station;
• and
• (6) storing said routing address in the first subscriber's station.