DISTRIBUTED IP-POOL IN GPRS

Abstract: This invention relates to an arrangement to distribute IP-addresses in a GPRS network. The GPRS system has a pool of IP-addresses to be used by subscribers. This pool is located on a global processor in the GPRS system which is distributing addresses to all other processors in the external networks. According to the invention there is configured one local pool per processor for each external network. Said local pool is supplied with a pack of addresses from the global pool. When a local pool is going empty, the pool is supplied with another pack of addresses from the global pool. If the local pool exceed a predefined limit in the number of contained addresses, a pack of addresses is released. The global pool can then distribute these addresses to other local pools.

Description: DISTRIBUTED IP-POOL IN GPRS TECHNICAL FIELD The present invention relates to the filed of mobile data communication, and in particular an arrangement for distributing IP-addresses in a GPRS network. TECHNICAL BACKGROUND The GPRS (General Packet Radio Service) offers a high- speed, packet-switched, mobile data communication network, where the subscribers can connect themselves to an external network from a mobile terminal. The subscribers need an IP- address to route packets to and from the external network. They can specify this address themselves, called static address, or receive an address from the external network or the GPRS-system. The last case is then called a dynamic address allocation. The GPRS system has an internal pool of IP-addresses to be used by the subscribers to get a dynamic IP-address. This pool is located on a global processor in the GPRS-system and is distributing addresses to all the other processors. The global processor will also keep track of which addresses are used and which are available for the subscribers . THE PROBLEM AREA The global processor has to keep track of which addresses that are in use, so that it will not give out the same address to two subscribers. The operator of the GPRS-system will only give in one IP-pool per external network, so the processor have to keep track of the dynamic addresses for the whole GPRS-network. This means that it will be generated a lot of unwanted traffic towards the global processor which holds the IP-pool. Each subscriber, possibly connected to another processor, have to obtain its address and release it through the global processor. POSSIBLE SOLUTIONS One way to solve the problem would have been to configure one IP-pool per processor for each external network. Two arguments show that this is a bad solution. The number of processors in the system should be highly dynamic, and there should be no need for configuration of the processor before start. This means that each processor could not have its own IP-pool. Also, the load could be unevenly distributed among the processors, with the result that one processor has run out of addresses, while the other processors have many unused addresses left. The address- resources would in this case have a low degree of utilisation. The other way to solve the problem is to allow for all the traffic generated by having only one global address-pool. The advantage with this solution is that all the addresses would be in use before one processor would that report that no addresses were available. PROBLEMS WITH THESE SOLUTIONS The above-mentioned solutions will either reguire a configuration of the processors before start, or result m unwanted traffic towards the global processors in the GPRS- system. OTHER PRIOR ART US-patent 5,093,912 describes a method for expanding and contracting a resource pool, mainly with respect to system storage. The patent has no global resource holder to keep track of the overall resource management, but uses an operating system to handle the deletion of a pool of resources. Moreover, the expansion of the pool by acquiring further resources also involves an external system, such as an operating system. Allocation of an IP address for an end user in a computer network could not directly be compared to allocation of system storage in a computer. The IP addresses will most likely be kept for several hours, possibly weeks in a GPRS system. Typical memory allocations in a computer system could last for seconds or minutes. The address should also be kept by the subscriber, even though one of the local processors in the GPRS node restarts. This is a very unlikely behaviour of a general computer resource. Thereby, a comparison of an IP-address pool and a typical computer resource pool is not absolutely adequate. An article from CISCO: New Features in Release 12.1 (1)T, http: //www .cisco . com...are/iosl21/121newft/121t/121tl /gprsl.htm, Aug 26, 1999, page 14, describes how one can use one DHCP server for all the external networks, instead of letting each external network connected to the GGSN include its own DHCP server. However, no distribution of addresses is done between the different DHCP servers, i.e. the global DHCP server and the local DHCP servers. THE INVENTION OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an arrangement for providing IP-addresses in a GPRS network which dramatically reduces the traffic towards the global processor that holds the pool of IP-addresses. Another object is to provide a such arrangement that secures a high and evenly degree of utilisation of the address resources. BRIEF DESCRIPTION OF THE INVENTION These objects are achieved in an arrangement for distributing IP-addresses in a GPRS network, which is characterized by the features of the enclosed claim 1. Additional embodiments of the invention appears from the subsequent dependant claims. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in detail in reference to the appended drawings, in which: Fig. 1 is a schematical overview of a system for distributing addresses using one global IP-pool (prior art) . Fig. 2 shows the system according to the invention using one local IP-pool per processor for each external network. DETAILED DESCRIPTION The new solution will still keep one IP-pool per external network for the whole GPRS-system. When a processor receives a request for a dynamic IP-address from a mobile- subscriber, it will signal the global processor that it needs an IP-address. The global processor will now give out a pack of addresses to the requesting processor instead of one address. The processor receiving the addresses will then give one of the addresses to the subscriber and keep the rest of the addresses in an internal storage. When a new subscriber asks for another address the processor now has its own, small IP-pool, from which it can give out an address. After a while, when the processor receives yet another request for an address, and its local IP-pool is empty, it requests the global processor again, and receives another pack of addresses. Regarding release of the addresses the system works the same way. The remote processor will not release an address before a whole group of addresses should be released. This assures that the addresses will be spread out between processors, which needs them. The size of the address-blocks are of crucial matter to make a fine balance between generated traffic to get and release address-blocks, and to distribute the addresses to those processors which needs them most. As an example, the central processor can have 100 addresses available. Of course, if the processor divides the pool into 50 addresses in each block, very little traffic will be generated after two external processes have received a block of addresses, but then the global pool would be empty, and no other processes can access any addresses. On the other hand, if the pool were split in blocks containing only five addresses, the external processes would have to ask the global processor about more IP-addresses, or release the addresses a lot more often. The size of the blocks should be dynamically adjusted to achieve as little traffic as possible, without being to liberal with the address resources. The system could with advantage comprise an arrangement which permit the release of addresses that not has been in use for a long time. E.g. the application processors could be adapted to report to the global processor with regular intervals. Should an application processor drop out and not report, the global processor is allowed to release the corresponding IP-addresses for other use. An overview of the messages that may be generated in Figure 1 can be seen in the table below. In the table it is three processors communicating with the global processor, each will have two subscribers attached, which needs one address each. Some of them will release their addresses after a while. The processors are described as AP' s (Application Processor) , and the one owning the IP-pool is defined as the global processor (AP-global) . The last column is showing the number of messages generated if the new invention is used. Table 1: Overview of number of messages Figure 2 shows the new set-up with one internal IP-pool per processor. From the table one can clearly see the stop of message flow towards the global processor after the local processors have received their own, small local IP-pool. No messages will be sent as long as the processors do not need more addresses, or have a free, local address-block, which can be released. The internal storage for each processor's temporary IP-pool could be in RAM. It should be aimed at a fast way to access the pool, but it should also be kept in mind that the pool must survive a crash of the node. One way to assure this is to regularly take copies of the local pools and store them persistent, while during traffic the pool is only modified in RAM. BROADENING This approach reduce intercommunication towards a central resource-handler, and can be used regardless of what kind of resources that should be distributed. As long as the receiving units can store spare resources for future use, and the global resource-pool is large enough to give out excessive resources

Claims: CLAIMS 1. Arrangement for distributing IP-addresses m a GPRS network, which network comprises a global processor holding a pool of available addresses, and a number of external networks comprising application processors, which processors are adapted to supply an address from the global pool to a user upon request, each application processor is arranged to hold an internal pool of IP-addresses, the application processor is adapted to request IP- addresses from the global processor when said internal pool is empty or nearly empty, whereupon the global processor is adapted to respond by transferring a group comprising a number of IP-addresses to the requesting application processor. 2. Arrangement according to claim 1, m which the groups of IP-addresses in said internal pool has a predefined static size. 3. Arrangement according to claim 2, in which said processor is adapted to release a group of addresses and notify the global processor thereof, if the number of addresses m the internal pool of an application processor exceeds a predefined limit. 4. Arrangement according to claim 3, in which said limit is equal to two times the size of the group of IP-addresses last received from the global processor . 5. Arrangement according to claim 1, in which the size of the groups of IP-addresses in said internal pool is dynamically adjusted to achieve as little traffic as possible, without being too liberal with the address resources. 6. Arrangement according to claim 5, in which said processor is adapted to release a group of addresses and notify the global processor thereof, if the number of addresses in the internal pool of an application processor exceeds a predefined limit. 7. Arrangement according to claim 6, in which said limit is equal to two times the size of the group of IP-addresses last received from the global processor. 8. Arrangement according to claim 1, in which the global processor is arranged to release addresses that not has been used in a preceding interval of time. 9. Arrangement according to claim 1, in which each application processor is arranged to store said internal pool of IP-addresses in RAM, and make back-up copies of this pool on a persistent storage medium with regular intervals. 10. Arrangement for distributing resources in a network, which network comprises a global processor holding a pool of available resources, and a number of external networks comprising application processors, which processors are adapted to supply a resource from the global pool to a user upon request, each application processor is arranged to hold an internal pool of resources, the application processor is adapted to request resources from the global processor when said internal pool is empty or nearly empty, whereupon the global processor is adapted to respond by transferring a group comprising a number of resources to the requesting application processor.

Inventors: AUNE LEIF-EINAR, AUNE, LEIF-EINAR
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 2000
Main classification: H04L29
IPC codes: H04L12, H04L29