A packet switching network (VoIP) with communication components (A1 - A4, B1 - B11), with which addresses are associated and which are arranged to communicate with each other using these addresses, wherein a) several of the communication components (A1 - A4, B1 - B11) comprise resources which contain usable gateways in the network (VoIP) for connecting the packet switching network (VoIP) to a circuit-switched network (ISDN), wherein search function means for determining the addresses of other communication components (A1 - A4, B1 - B11) comprising the resources are integrated in several of the communication components (A1 - A4, B1 - B11), b) each of these search function means is designed for determining the addresses for transmitting a first query which contains, in addition to the address of the communication component, whose search function means transmits the first query, information about the fact that other communication components (A1, A2, A4, B1 - B11) are sought which support the search function means, c) each reached communication component which supports the search function means is designed to return a query hit with its address in the sequence of the first query, d) the search function means is subsequently arranged to transmit at least one second query comprising information about the sought resource type in the form of the gateway to at least one of the communication components (A1, A2, A4, B1 - B11) which responded to the first query with the query hit and at least one of the communication components (A1 - A4, B1 - B11) which can make available the sought resource type in the form of the gateway is arranged to respond to the second query, wherein e) the response to the second query contains specific information about the gateway, f) even the communication components (A1 - A4, B1 - B11) that respond to the second query are designed to forward the second query to other communication components (A1 - A4, B1 - B11), and g) the addresses of the communication components (A1 - A4, B1 - B11) obtained using the query hit and using the response from the second query can be used to construct communication connections. a) several of the communication components (A1 - A4, B1 - B11) comprise resources which contain usable gateways in the network (VoIP) for connecting the packet switching network (VoIP) to a circuit-switched network (ISDN), wherein search function means for determining the addresses of other communication components (A1 - A4, B1 - B11) comprising the resources are integrated in several of the communication components (A1 - A4, B1 - B11), b) each of these search function means is designed for determining the addresses for transmitting a first query which contains, in addition to the address of the communication component, whose search function means transmits the first query, information about the fact that other communication components (A1, A2, A4, B1 - B11) are sought which support the search function means, c) each reached communication component which supports the search function means is designed to return a query hit with its address in the sequence of the first query, d) the search function means is subsequently arranged to transmit at least one second query comprising information about the sought resource type in the form of the gateway to at least one of the communication components (A1, A2, A4, B1 - B11) which responded to the first query with the query hit and at least one of the communication components (A1 - A4, B1 - B11) which can make available the sought resource type in the form of the gateway is arranged to respond to the second query, wherein e) the response to the second query contains specific information about the gateway, f) even the communication components (A1 - A4, B1 - B11) that respond to the second query are designed to forward the second query to other communication components (A1 - A4, B1 - B11), and g) the addresses of the communication components (A1 - A4, B1 - B11) obtained using the query hit and using the response from the second query can be used to construct communication connections.