Communications system having enhanced fault tolerance
View Patent ↗The invention relates to communications systems, and particularly to enhancing tolerance to failures in network elements and transmission systems. The fault tolerance is achieved by providing two or more active ATM permanent virtual channel (PVC) connections between a core network element and an access network element, and providing a separate ATM interface unit for each such ATM PVC connection in the core network element. The user and signalling traffic is distributed among these active connections and interface units. In case of a failure in one of the ATM PVC connections or interface units, the communication is maintained over the other connection(s) and interface unit(s). Thus, only part of the transport capacity is lost, and a total block of communication is avoided. Any new communication will be setup over the other connections.
1. A core network element in form of serving packet radio support node for a communication system including at least one access network element in form of a radio network controller and a transport network providing Asynchronous Transfer Mode (ATM) permanent virtual channel (PVC) connections between the core network element and said at least one access network element, said core network element comprising:
two or more ATM interface units;
means for providing two or more active ATM PVC connections between said core network element and each of said at least one access network element, such that different ATM PVC connections from any one of said at least one access network element are arranged to be connected to different ones of said two or more ATM interface units, and
means for spreading an ATM traffic over said different ATM PVC connections in order to improve tolerance of the communications system to failures in the ATM PVC connections or in the ATM interface units.
2. A core network element as claimed in claim 1 , wherein said core network element is configured to, responsive to a failure in one of said two or more ATM PVC connections, route the traffic to other one or ones of said two or more ATM PVC connections.
3. A core network element as claimed in claim 1 , wherein said core network element is configured to, responsive to a failure in one of said two or more ATM PVC connections, drop said failed connection or let the failed connection to hang until higher level system protocols release the connection.
4. A core network element as claimed in claim 1 , wherein said core network element is configured to detect a failure in the ATM PVC connection by performing a predetermined link test procedure.
5. A core network element as claimed in claim 4 , wherein said link test protocol includes periodical sending of ATM loop-back cells.
6. A core network element as claimed in claim 1 , wherein said core network element is arranged to select one of the interface units for establishing, rerouting or re-establishing the call based on traffic loading and capacity of the interface units.
7. A core network element as claimed in claim 1 , wherein said core network element is responsive to a packet data context request from a user terminal for selecting the one of the interface units into which the packet data context is placed.
8. A core network element as claimed in claim 1 , wherein said core network element comprises a third generation serving general packet radio service support node.
9. An access network element in form of a radio network controller for a communications system including at least one access network element, a core network element and a transport network providing Asynchronous Transfer Mode (ATM) permanent virtual channel (PVC) connections between the core network element and said access network element, said access network element comprising:
means for providing two or more active ATM PVC connections between said access network element and two or more ATM interface units of said core network element, such that different ATM PVC connections from said at least one access network element are arranged to be connected to different ones of said two or more ATM interface units of said core network element, and
means for spreading an ATM traffic over said different ATM PVC connections in order to improve tolerance of the communications system to failures in the ATM PVC connections or in the ATM interface units.
10. An access network element as claimed in claim 9 , wherein said at least one access network element is configured to, responsive to a failure in one of said two or more ATM PVC connections, route the traffic to other one or ones of said two or more ATM PVC connections.
11. An access network element as claimed in claim 9 , wherein said at least one access network element is configured to, responsive to a failure in one of said two or more ATM PVC connections, drop said failed connection or let the failed connection to hang until higher level system protocols release the connection.
12. An access network element as claimed in claim 9 , wherein said at least one access network element is configured to detect a failure in the ATM PVC connection by performing a predetermined link test procedure.
13. An access network element as claimed in claim 9 , wherein said link test protocol includes periodical sending of ATM loop-back cells.