The invention relates to a method for saving subscriber data in a restart-resistant manner according to the pre-characterizing clause of claim 1.
From here on the specific technical terms and conventional acronyms for the telecommunication areas known as access technology (or simply “access”), transport (or “core network”) and Internet protocol will be used in order to explain the subject matter concisely and accurately. These acronyms are listed at the end as an integral part of this document. In most cases therefore, no special explanation of the said terms and acronyms will be given in the course of the text. Moreover when used in the telecommunication sense, and therefore in the context of this document, the term “subscriber” does not refer to a person.
The transmission mode known as xDSL is used for high bit-rate access to the subscriber. In this mode a plurality of ADSL or xDSL modems ATU-R are connected to a multiplexer DSLAM from the connection point of a telecommunications operator.
In order to communicate, a client computer (subscriber-side) needs an IP address. In most cases an IP address is dynamically allocated from a pool for a certain time using DHCP protocol. The operator frequently sets the validity of this address at less than 24 hours. This is done for two reasons:
Reference will now be made to
The problem that therefore arises is how to store the subscriber-related IP address, MAC address and lease time data in a restart-resistant memory and quickly reconstruct said data in a simple manner.
This problem can be solved by the following alternative approaches:
A Searching for data in a memory field;
B Storing fixed data in restart-resistant memories.
Approach A
Subscriber data such as MAC address, subscriber index, etc. are stored in a memory module and retrieved using a fast access method. For this purpose there are machine-intimate solutions such as CAM components, which are designed for fast search accesses so that when a search term is entered (such as subscriber index) they return the required data set (e.g. MAC address). In principle this method can also be used as a software solution. For this purpose it is always necessary to re-store the data in the CAM component each time there is a new entry. Furthermore in most cases CAM components are not restart-resistant.
Approach B
B.1 WO 2004./038979 A2
Document WO 2004/038979 A2 [2] proposes a passive optical network PON for restoring an address allocation in which said address allocation is stored in a non-volatile memory and the original state is restored by means of appropriate queries.
B.2 EP 1 260 907 A1
Document EP 1 260 907 A1 [1] discloses a method for persistent storing of data in which parts of the operating system are copied from a Flash PROM read-only memory into the read-write memory during power-up. The Flash PROM read-only memory can be provided with a new version of the said operating system parts afterwards if need be. Flash PROM read-only memories are restart-resistant, but rewriting is possible only after deletion block-by-block. For this reason this technique cannot be used for the problem mentioned above. In the context of this document the term “restart-resistant” is synonymous with the term “new-start resistant”.
The object of the present invention is therefore to specify a method for saving in a restart-resistant manner the subscriber data of subscribers connected to a connection multiplexer so that subscriber data can be obtained when a connection multiplexer is restarted and after the restart said data can be allocated in a simple manner to the subscribers of the said connection multiplexer and the data can be reconstructed.
This object is achieved by means of the method specified in claim 1. Advantageous embodiments of the invention are specified in further claims.
The inventive method permits the reconstruction of the dynamic data in a simple manner when a connection multiplexer has been restarted, without said data having to be re-stored. This is achieved by a restart-resistant memory that contains the subscriber connection data records and additionally by the storage of an index for each subscriber connection data record, said index identifying the relevant subscriber.
In this way a method is provided for saving and reconstructing the vitally important subscriber connection data. At this point it should be noted that in the context of this document the terms saving, back-up and data back-up subsume not only the storage but also the reconstruction of the data (or subscriber data). This is also how the concept is understood colloquially, since the term data back-up always implies that the data can also be restored to the original location.
The invention will be explained in greater detail with the aid of the accompanying drawing and figures. These show the following:
The exemplary embodiment relates to a DSLAM, also known as a DSLAM connection multiplexer or connection multiplexer 1. The invention can however be used for any type of connection technology in which it is intended to manage restart-resistant subscriber data for subscribers 8. As mentioned,
The method will now be explained with the aid of FIGS. 2 to 5. The explanations and definitions listed at the end of this document under the heading “List of the reference characters and variables used” form an integral part.
The sequence in which the subscriber data sets for the number M of subscribers need to be stored is arbitrary. The principle used for the inventive method is the obvious one of “first come first served”. In particular this means that the data sets are stored in as efficient a way as possible without being re-sorted. Aging of the “lease time”, that is to say the time-limited validity of a connection, as explained in the introduction, represents a problem for the further management and/or administration of these data sets. It is also intended that re-sorting shall not be carried out when the validity of a data set expires. Instead it shall be possible for data sets that are no longer valid to be overwritten by a new, current data set.
A restart-resistant memory RRM with a capacity of N data sets is available for storing the restart-resistant subscriber data sets containing a MAC address, an IP address, the period of validity and the allocation to the subscriber concerned (index vcxindex). Information is stored in this memory RRM, with the reference characters DHCP-RRM (see FIGS. 2 to 5), in the sequence in which it occurs. A dynamic memory DHCPStack monitors the occupancy of said memory RRM. This is achieved with the aid of a stack pointer StackCnt that indicates which of the elements in the memory DHCP-RRM is the very next free element. If a data set needs to be stored in the memory DHCP-RRM, the element at the location StackCnt in the memory DHCPStack specifies the next free element in the memory DHCP-RRM. When the data set has been stored, the value zero is written to the location StackCnt. This means that the location concerned in the memory DHCPStack is occupied by a valid entry. The pointer StackCnt is then incremented by 1. From the viewpoint of the numbered/indexed subscribers, a further read-write memory DHCPIndex is provided, of which the location rrmindex in the memory DHCP-RRM contains the data set of the subscriber with connection index vcxindex. In this instance the subscribers are listed in linear fashion. This situation is illustrated in
The removal of a subscriber data set will now be explained with the aid of
In the memory DHCPIndex the index rrmindex is read from the location vcxindex. The content of the data set concerned in the memory DHCP-RRM is made invalid by overwriting with zeros in the previously mentioned manner. The stack pointer is decremented by 1 and the value zero(=occupied) in the memory DHCPStack is overwritten with the index rrmindex of the now freed memory location in the memory DHCP-RRM. In the present case according to the figure this information consists of:
rrmindex=3
StackCnt=5
vcxindex=12, being subscriber 12.
Zero for occupied was entered at the old location StackCnt=5, then the StackCnt was incremented by 1, now at stackindex=6. By means of a scan from rrmindex=1 onwards a free memory location was found in the memory DHCP-RRM at the location rrmindex=3. The data set for the subscriber 14 is now entered here. The term scan refers to an efficient search of a memory area. Preferably an instruction SCAN_EQUAL or SCAN_NOT_EQUAL, of the type known as a machine-oriented instruction, will be used for this purpose on implementation.
If the connection multiplexer undergoes a restart, the data in the memories DHCPStack and DHCPIndex will be reconstructed as follows:
On implementation, the restriction N<M makes it essential that cases of failure are detected and accordingly notified by means of overflow buffering routines. Preferably the values for N and M are adjusted to an average traffic volume.
However, the idea behind the invention makes it possible to provide exactly the same number of memory locations for subscriber data sets as the number of subscribers connected to the connection multiplexer 1.
Only the minimum subscriber data that needs to be stored per subscriber connection data record has been listed here.
Number | Date | Country | Kind |
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04026792.4 | Nov 2004 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP05/10354 | 9/24/2005 | WO | 4/5/2007 |