Server assignment method for clients distributed in more than one networks and client for the server assignmend method

Modern communication or data processing systems are often across multiple subnets, eg so-called local area networks (LAN) distributed, networked turn to larger networks, eg wide area networks (WAN). An important principle of such distributed architecture communication or data processing systems is the so-called client-server principle. As server this means is designated, the central services for multiple network distributed in a distributed system service user, offering so-called clients. Clients and servers generally operate autonomously, that is, a server offers its services regardless of the client. A client can only take such services that offers an available server, wherein the client to a use of a service has no influence on the processing by the server.

To use the services offered by a server by clients, it is necessary that the server the client or the client know the server and can address. That is the basis of an interaction between client and server, the clients in question are allocated to the server.

In many cases, especially in Internet Protocol based networks, the allocation of a server to clients by manual configuration of the corresponding client or the server is performed. Usually this will be in the server Internet Protocol addresses of the individual clients or configured in the client's Internet Protocol address of the server. In this way, the client and server each other a priori are assigned. However, such manual configuration requires especially in large networks with egg ner high number of potential clients considerable expense. In addition, any change in the assignment, for example, by switching to a new server or adding new clients to do a manual configuration is required.

Due to the high cost of manual configuration automated assignment process, so-called auto-discovery methods are used increasingly. A commonly used method is based on that so-called DHCP server (DHCP: Dynamic Host Configuration Protocol) are configured such that they can make available on request client or server addresses. Such a method assumes that appropriately configured DHCP servers are available in each subnet and coordinated subnetworks. This configuration data in the DHCP servers need to be updated in accordance with any change in the client-server mapping. DHCP servers are, for example, from the Internet document "Request for Comments: 2131, Dynamic Host Configuration Protocol" by R. Droms, dated March 1997, known.

US 2003/061315 A1 discloses the Plug and Play Host Protocol PPHP said subnet relay agents to pass on the search.

It is an object of the present invention to provide a method for allocating distributed across multiple subnets client to a server that requires less configuration effort. It is another object of the invention to provide a client for performing the method.

This object is achieved by a method having the features of claim 1 and by a client with the features of patent claim 7.

In the present process multiple subnets, including local area networks, distributed client is selected to a server in a particular subnet one of the clients to allocate over. According to the invention is sought by a respective selected client subnetworks for other ausgewähl th clients and to the server, wherein the selected client in locating the server stores a these identifying server address information and queries in finding another selected client from this server address information and preservation stores. The stored server address information is transmitted from the selected client to one or more other selected or unselected clients.

The inventive method can be performed by several selected clients different subnets parallel search for the server. Due to the parallel search of the server usually can be quickly retrieved from one of the selected clients. The are not modified to search server needs to perform the method. A respective selected client can the server, eg, through visits of a service to be used associated server ports. Once the server is found by one of the selected clients that in this way the server found, the server address information, starting from this selected client, be spread over other selected or unselected clients cascade and thus very quickly, subnetworks to the clients, be assigned.

The invention allows for a decentralized and essentially self-organizing client-server mapping. In particular, no central information services such as DHCP or manual configuration or reconfiguration of clients, the server and other network components are required.

Another advantage of the invention is that the implementation of the active search for the server can be restricted to selected clients, producing a significantly lower network load than if all clients were the server.

The inventive method is further characterized by low latency or reconfiguration at a Neuankopplung of clients or a new server, since it is already sufficient for newly coupled clients to obtain the server address information, instead of the server itself, a selected client, the server address information has been obtained to find. If the selected client's own subnet has already received the server address information, a subnet on this newly coupled client can be supplied in a particularly simple manner with the server address information.

Advantageous embodiments and developments of the invention are indicated in the dependent claims.

The transmission of the stored server address information to the other client at least one selected or not selected can be especially encouraged by a emanating from this client query. Preferably, the server address information from selected client will be assigned to all the server client received its own subnet and / or to all known him selected clients outside its subnet, each on their own initiative or as a result of a query. A transmission of the server address information to as many other clients allows very rapid subnetworks cascading distribution server address information.

Preferably, the selected client in finding another selected clients can store an identifying this client address information. Such client address information can to others, possibly interested clients are passed. Through inter-subnet distribution of client address information to selected clients this can create a topology image of their Subnetzumgebung and used for an inter-subnet communication. Furthermore, the selected client can transmit them to one or more by one or more stored client address information identified, selected clients as a result of receipt of the server address information.

According to an advantageous embodiment of the method the client selection can be made in a subnet by its clients. The clients on a subnet can preferably autonomously choose among themselves or with clients on other subnets a client. To select a client thus no external configuration is required.

According to a further advantageous embodiment of the invention, a selected, the first client can at finding located one in a different subnet, not selected clients, this encourage them to forward to the client in the subnet selected, the second query the server address information. To this end, the non-selected client can inform the second client accordingly so that it takes to answer the query with respect to the first client and transmits it to the first client with knowledge of the server address information. Alternatively, the non-selected client can even query the second client and forward an optionally obtained server address information to the first client. According to another alternative, the non-selected client can transmit a second client identifying client address information for the first client, so that it can retrieve the second client directly.

An embodiment of the invention is explained in greater detail using the drawing, in each case showing in schematic representation:<ul><li>1 shows a client according to the invention and</li><li>Figures 2-5 a multiple subnets extensive network in various stages of the procedure</li></ul>

In the <b>figures 2-5</b> is respectively a multiple subnetworks SNA, SNB, SNC and SND comprehensive network shown schematically. For the present embodiment, it is assumed that the subnetworks SNA ...., SND through internet protocol-based local area networks, so-called LANs (LAN: Local Area Network) are realized via a wide area network (not shown), such as the Internet coupled together are. The subnet SND in this case has to a server SRV, one communications, data processing and / or information service provides a service, for example, over a predetermined or dynamically assigned server port on the network. Further, each includes the subnet SNA clients C1, C2, C3 and CSA, the subnet SNB clients CL and COD, as well as the subnet SNC clients CL and CSC. The clients CSA, CSB, CSC, C1, C2, C3 and CL need the service provided by the server SRV and are attributable to him in this sense. To assign the client CSA, ..., CL to the server SRV, it is necessary that the clients CSA, ..., CL a server SRV identifying address information SA, in the present embodiment, an Internet Protocol address of the server SRV know. The Internet Protocol address of the server SRV SA, hereinafter generally referred to as IP address, the clients CSA, ..., CL received by the inventive method.

In <b>figure 1</b> is shown schematically an inventive configuration of the clients CSB. The client CSB has to be coupled to the subnet SNB over a network interface NS. Furthermore, the client CSB a selection module CSEL on to select a client from all or a predetermined group of to the same subnet, here SNB, as the client CSB connected clients CL and CSB. The selection is made by an interaction selecting modules CSEL all clients involved in the selection CSB and CL by known, so-called selection process. Such a selection process, for example, from the 7.8.2003 on the Internet at the address "http://www.cs.cornell.edu/home/rvr/papers/ProbLeaderElection.pdf" freely accessible document "A Probalbilistically Correct Leader Election Protocol for Large Groups "by Gupta, van Renesse and Birman, dated known April 2000th

For the present embodiment, it is assumed that the client CSB is selected by the jointly executed by the client CSB and CL choice on the subnet SNB. Similarly, assume that the subnet SNA client CSA is selected by the clients C1, C2, C3 and CSA and the subnet SNC client CSC by the client CL and CSC. Thus exactly one client CSA, CSB and CSC is selected in each of the subnetworks SNA, SNB and SNC. Accordingly, the client CSA, CSB and CSC as the selected clients and the clients C1, C2, C3 and CL are designated as non-selected client in the following. A respective selected client CSA, CSB and CSC is the unselected clients its subnet SNA, SNB or SNC after his selection - as in<b>figure 2</b> indicated by dashed double arrows - assigned. A respective selected client CSA, CSB and CSC may transmit non-selected clients of its subnet SNA, SNB or SNC information preferably by means of a so-called. Broadcast message after his selection other components, for example.

The illustrated in Figure 1 client CSB also has a search module SM for subnet searches for the server SRV and after in other subnets, here SNA and SNC, selected clients, here CSA and CSC. Furthermore, the COD client to a memory MEM for storing the IP address of the server SRV SA, if the server SRV is found or the IP address SA is transmitted from a found, selected client. Furthermore, the client CSB includes an output module OUT to transmit any stored server IP address SA to selected clients CSA, CSC other subnets SNA, SNC and to the clients CL unselected its own subnetwork SNB. The clients CSA and CSC have substantially the same structure as the client shown in Figure 1 CSB.

<b>figure 3</b> illustrates the processing performed by the selected clients CSA, CSB and CSC to their respective selection-subnet search. In this embodiment, the search module SM client CSB initiated under whose looking for a transmission of a first interrogation message QMB1 in the subnet SNA and a second query message QMB2 in the subnetwork SND. Regardless of the selected client CSA received a query message QMA1 in the subnet SNC. The query messages QMA1, QMB1 and QMB2 can preferably be addressed to the port number of the above-mentioned server ports over which the server SRV provides its service. At the same time monitor the selected clients CSA, CSB and CSC itself this port number to properly operate analog queries from other clients.

A selected client, eg COD can take in his search outside its own subnetwork to different types of clients. Using the example of QMB1 and QMB2 examined by transmission of Abfragmeldungen clients CSB the further procedure will now depend on the type of the found, ie a respective inquiry message stated QMB1 or QMB2 receiving clients:<ul><li>1. A method of the invention is not supportive client is found (not shown in the drawing), it recognizes the searching client CSB by the absence of an expected response and continues his search.</li><li>2. If an unselected but the inventive method of supporting client, eg C3 is found, it does not respond to the searching client CSB in the present embodiment, but informs the selected in its own subnet SNA client CSA on the query. The informed client CSA accepts then answering. This case is<b>figure 4</b> further illustrated. According to Figure 4, the selected client CSB QMB1 transmitted addressed to the above-mentioned port number query message to the non-selected client C3 subnet SNA. The client C3 transmitted consequently an informational message IM for selected client CSA its subnet SNA, through which the client is informed of the CSA polling the client CSB. The client then CSA answered the query by sending a response message to the client CSB AM. If the client CSA already knows the server IP address SA based on its own queries, he received the server IP address SA with the response message AM to the client CSB. If the client CSA hand does not know the server IP address, this is communicated to the client CSB by a correspondingly negative response message AM. With a negative response message of seeking client CSB continues its search.</li><li>3. If another selected client, such as CSA or CSC is found, answered this directly query the client CSB. If the selected client found CSA or CSC, already knows the server IP address SA based on its own queries, this is transmitted to the interrogating client CSB. If the client found CSA or CSC server IP address SA does not yet know, is transmitted in accordance with a negative response message. With a negative response message of seeking client CSB continues its search. Preferably, between the investigation and found selected client more information to be exchanged, for example, to create a topology diagram of a network environment of the selected clients. Advantageously, the searching client CSB stores the IP addresses of all found, selected and / or unselected clients in its memory MEM.</li><li>4. If the selected client CSB finds the server SRV itself, it recognizes this on the basis of the response of the server SRV to its port scanning and consequently stores the IP address of the SA found server SRV in the memory MEM from. The discovery of the server SRV is illustrated in FIG. 3 In Figure 3, the interrogation message QMB2 is transmitted to the server SRV in subnetwork SND, whereupon the server SRV a response message SAM received back, with reference to the requesting client CSB the server SRV recognize. After the server SRV recognizing the client CSB stores the IP address of the found server SRV as server IP address SA in its memory MEM from.</li></ul>

Once a selected client, here CSB who knows server IP address SA, it can transmit them to other clients, in turn, distribute the transmitted server IP address SA to other clients. In this way, the server IP address SA is distributed in cascade on the subnets SNA, SNB and SNC.

In <b>figure 5</b> is exemplified as the server IP address SA from the selected client CSB by means of its output module OUT to the clients CL its own subnet SNB and is subnetworks transmitted to the selected client CSA, known its IP address in the client CSB due to the previous query is. The client CSA then transmits the server IP address SA to the clients C1, C2 and C3 on its own subnet SNA and subnetworks to the selected client CSC, who eventually further transmits the server IP address SA to the clients CL its own subnet CNC. A transmission of the server IP address SA can for example take place by means of a so-called. Notify message.

In this way, all clients CSA, CSB, CSC, C1, C2, C3 and CL of the network that require access to the server SRV, received its required to access IP address SA. These clients CSA, ..., CL are thus the server SRV allocated in terms of a client-server relationship.

The invention allows for a decentralized controlled and largely self-organized running assigning distributed across multiple subnets clients to their server. A manual configuration or establishment of central information services, such as DNS (Domain Name System) or DHCP therefore unnecessary. But if such a central information services such as DNS or DHCP already exist on the network, they can be included advantageously in the inventive concept in a simple way. So can be set up in such example, the selected clients that they can check out other selected clients also central DNS servers and / or DHCP server for the IP address of the server you want to SA SRV. According to one embodiment, a DNS or DHCP server can be set up so that it behaves like a selected client in the sense of the inventive method. By the inclusion of existing central information services, such as DNS or DHCP, the time period for searching for the server, and the distribution of the IP address can be further reduced.

An implementation of the method does not require any modification to the server to be searched, but only to the method supporting clients. According to the present embodiment is a method of supporting the client to the selection module CSEL for selecting a client's own subnet supplement. Furthermore, a method of supporting client is preferably to design such that it supports the exchange of information with the selected client's own subnet, and that it can forward requests of selected clients on other subnets on the selected client's own subnet. With a selectable client is in accordance with the present embodiment, in addition, a search engine, here SM, here MEM, provide for subnet searches for selected clients as well as a memory for storing the server IP address SA. Furthermore, in a selectable client is also an output module, here OUT to provide to transmit the stored server IP address SA to inquiring selected clients outside its own subnet and to the requesting client's own subnet.