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 common across multiple subnets, eg so-called local Networks (LAN) distributed, in turn, to a larger network, eg over wide area networks (WAN) are networked. An important Architecture principle of such distributed communication or Data processing systems is the so-called client-server principle. As server this means is referred to, centralized in a distributed system services multiple distributed network service users, so-called Clients offering. Clients and servers generally operate autonomous, that is, a server offers its services regardless of each client. A client can only such services in avail that offers an available server, the client for a use of a service does not affect has more on the processing by the server.

To use the services provided by a server through Clients, it is necessary that the server or the client the client know the server and can address. That as the basis for interaction between client and server, are the respective clients assigned to the server.

In many cases, particularly in Internet Protocol-based Networks, the assignment of a server to clients is manual configuration of that client or the server made. Usually here in the server Internet protocol addresses of each client or in the Clients configure the Internet Protocol address of the server. In this way, the client and the server are mutually assigned a priori. Such manual configuration but requires particularly in large networks with egg ner high number of potential clients a considerable Effort. In addition, at each change of the allocation, for example by switching to a new server or adding New clients do a manual configuration required is.

Due to the high cost of manual configuration be automated assignment process increasingly called autodiscovery process used. A frequently The method used is based on that so-called DHCP server (DHCP: Dynamic Host Configuration Protocol) in such a way be configured to or on request client can provide server addresses. Such a process presupposes that appropriately configured DHCP servers are available in each subnet and subnetworks be coordinated. Here, when any change the client-server mapping configuration data in the DHCP servers be updated accordingly. DHCP server example, from the Internet document "Request for Comments: 2131, Dynamic Host Configuration Protocol "by R. Droms, dated March 1997, known.

It is an object of the present invention, a method Mapping distributed across multiple subnets to clients Server indicate that a lower configuration effort requires. It is another object of the invention a Client for performing the method indicated.

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

In the present process is to allocate over multiple subnets, including local area networks, distributed clients to a server in a respective one of the clients subnet selected. According to the invention by a respective selected Client subnetworks for other ausgewähl th client and searches for the server, wherein the selected Client in locating the server an identifying these Server address information and stores in finding another selected client from this server address information polls and stores on receipt. The saved Server address information is selected from Client to one or more other selected or not selected clients received.

The inventive method, the search for the Server from multiple selected clients different subnets be executed in parallel. Due to the parallel search the server can usually very quickly from one of the selected clients are found. The server to be searched does not need to be modified for implementing the method will. A respective selected client can ask the server associated for example by querying a one-to-use service recognize server ports. Once the server through a the selected client is found, the server address information, Starting from this selected client, cascade over other selected or not selected clients and thus very quickly to the subnetworks Clients are distributed that in this way the found Servers are assigned.

The invention allows for a decentralized and essentially self-organizing client-server mapping. Especially No central information services such as DHCP or manual configuration or reconfiguration of clients, the Server, or other network components needed.

Another advantage of the invention is that the Implementation of active search for the server to selected Clients may be limited, resulting in a much lower Network load generated than if all clients the server searched.

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

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

The transfer of the stored server address information to the at least a selected or non-selected another client may be affected by one of this client outgoing query causes. Preferably, the Server address information from selected client to all the Server assigned clients on its own subnet and / or to all known him selected clients outside its subnet, each on their own initiative or following a Query received. A transmission of the server address information Allowed to as many other clients a very fast subnetworks cascading distribution the server address information.

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

According to an advantageous embodiment of the invention Method, the client selection in a subnet by its Clients are made. The clients on a subnet can preferably independently among themselves or with other clients Subnets choose a client. To select a Clients thus no external configuration is needed.

According to a further advantageous embodiment of the invention , a selected, first client in retrieving a located on a different subnet, unselected Clients, this cause to the in its subnet selected second client a query of the server address information to be transmitted. For this purpose, the unselected client notifies the second client accordingly, so this against answering the query the first client accepts and with knowledge of the server address information this the first client transmits. alternative to the non-selected client, even the second Check client and an optionally obtained server address information forward for the first client. After a further alternative, the non-selected client a the second client identifying client address information the first client communicate, so this second Client can query directly.

An embodiment of the invention is described below with reference to explained to the drawing, in each case schematically show illustration:<sl><li>1 shows a client according to the invention and</li><li>Figures 2-5 a multiple subnets comprehensive Network in different stages of the procedure</li></sl>

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 realized: networks, so-called LANs (Local Area Network LAN) are, via a wide area network (not shown), such as for example, the Internet coupled to each other. The subnet SND in this case has to a server SRV, one service, eg a communication, data processing and / or information service over a predetermined or dynamically allocated Server port provides the network. furthermore each includes the subnet SNA clients C1, C2, C3 and CSA, the subnet SNB clients CL and CSB, and 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 attributable to him in this sense. To as- Clients CSA, ..., CL to the server SRV, it is necessary that the clients CSA, ..., CL a to Serve r SRV identifying Address information SA, in the present embodiment, a Internet Protocol address of the server SRV, know. The Internet Protocol address SA the server SRV, hereinafter usually referred to as IP address, the clients CSA, ..., CL, by means of the inventive method received.

In <b>figure 1</b> is an inventive structure of the client CSB shown schematically. The client CSB has for coupling NS to the subnet SNB over a network interface. furthermore , the client CSB a selection module CSEL on the Select a client from all or a predetermined Group 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 on the selection participating clients CSB and CL by known, so-called Selection process. Such a selection process is, for example, from the on 7.8.2003 via the Internet http://www.cs.cornell.edu/home/rvr/papers/ at the address " ProbLeaderElection.pdf "freely accessible document" A Probalbilistically Correct Leader Election Protocol for Large Groups ", Gupta, van Renesse and Birman, dated April 2000 known.

For the present embodiment it is assumed that by jointly executed by the client CSB and CL Choice on the subnet SNB client CSB is selected. Analogous to assume that the subnet SNA client CSA by the clients C1, C2, C3 and CSA and the subnet SNC client CSC is selected by the clients CL and CSC. In order in each of the subnetworks SNA, SNB and SNC exactly one client CSA, CSB and CSC selected. Accordingly, hereinafter the clients CSA, CSB and CSC as selected clients and the Clients C1, C2, C3 and CL called a non-selected client. 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> by dotted indicated double arrows - assigned. A respective selected client CSA, CSB and CSC may, at his choice other components, such as non-selected clients its subnet SNA, SNB or SNC information preferably communicate by means of a so-called. broadcast message.

The client shown in Figure 1 CSB also has a search module SM to-subnet search for the Server SRV as well as in other subnets, here SNA and SNC, selected clients, here CSA and CSC. Furthermore, the Client CSB a memory MEM to the IP address of the SA to save server SRV if the server SRV is found, or the IP address SA of a found, selected Client is received. Furthermore, the client includes a COD Output Module OUT, around the possibly memorized server IP address SA to selected clients CSA, CSC other subnets SNA, SNC and to the non-selected clients CL's own SNB subnet to be transmitted. The clients CSA and CSC have substantially the same structure as the in Figure 1 illustrated client CSB.

<b>figure 3</b> illustrated by the selected clients CSA, CSB and CSC conducted by their respective selection-subnet Search. In the present embodiment, prompted the search module SM client CSB under whose looking for a transmission of a first interrogation message QMB1 in the subnet SNA and a second query message QMB2 in the subnet SND. Regardless of the selected transmitted Client CSA an interrogation message QMA1 in the subnet SNC. The query messages QMA1, QMB1 and QMB2 can preferably the port number of the above-mentioned server ports over the server SRV provides its service addressed be. At the same time monitor the selected clients CSA, CSB and CSC itself this port number to analog visits other Clients suitable to use.

A selected client, eg COD can in his search outside its own subnetwork to different types of Clients meet. The example of the transmission through the Abfragmeldungen QMB1 and QMB2 browser client CSB hereinafter the further procedure depending on the type of the found, ie a respective inquiry message QMB1 or QMB2 receiving clients stated:<sl><li>1. A method of the invention is not supportive Client is found (not shown in the drawing), recognizes this the searching client CSB on absence an expected response and continues his search.</li><li>2. If an unselected but the invention The method of supporting the client, for example C3 is found it responds to the searching client CSB in the present Embodiment not, but informs his own subnet SNA selected client CSA on Query. The informed client CSA accepts thereupon the answer. This case is<b>figure 4</b> continue illustrated. According to Figure 4 transmits the selected Client CSB, addressed to the above-mentioned port number Query message to the client QMB1 unselected C3 the subnet SNA. The client C3 transmitted consequently an information message IM for selected client CSA SNA its subnet, by the client via the CSA Query the client CSB is informed. The client CSA answered then the query by sending a Response message AM to the client CSB. If the client the CSA Server IP address SA already based on own queries knows, he received the server IP address with the SA Response message AM to the client CSB. If the client CSA contrast does not know the server's IP address, it is the Client COD by a correspondingly negative response message AM communicated. With a negative response message sets the searching client CSB his search.</li><li>3. If another selected client, such as CSA or CSC is found, answered this directly querying the Clients CSB. If the selected client CSA found or CSC, the server IP address SA already based on its own knows queries this for interrogating client CSB transfer. If the client found CSA or CSC Server IP address SA does not yet know, will accordingly a negative response message transmitted. With a negative Reply message sets the searching client CSB his Search continues. Preferably, between the investigation and found selected client exchanged more information, to as a topology diagram of a network environment of selected clients create. Advantageously, stores the searching client CSB the IP addresses of all found, the selected and / or non-selected Clients in its memory MEM. </li><li>4. If the selected client CSB the server SRV itself finds he recognizes this on the basis of the response of the server SRV to its port scanning and stores as a result, 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 inquiry message to the server is QMB2 SRV transmits the subnet SND, whereupon the server SRV a response message SAM received back, based on the the requesting client CSB the server SRV recognize. After recognizing the server SRV stores the client IP address the COD the found server SRV as server IP address SA in its memory MEM.</li></sl>

Once a selected client, here CSB, the server IP address SA knows, he can forward this to other clients, the transmitted server IP address SA to turn distribute more clients. In this way, the server IP address SA cascaded over the subnetworks SNA, SNB and SNC distributed.

In <b>figure 5</b> is exemplified as the server IP address SA from selected client CSB by means of its output module OUT to the clients CL its own subnet SNB and subnetworks is transmitted to the selected client CSA is, its IP address in the client due to the CSB known previous query. The client received CSA Then, the server IP address SA to the clients C1, C2 and C3 on its own subnet SNA and subnetworks to the selected client CSC, the server IP address SA Finally, the client CL on its own subnet CNC transitting. 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, which required to access IP address SA received. These clients CSA, ..., CL are thus the server SRV assigned in terms of a client-server relationship.

The invention allows for a decentralized controlled and largely self-organized running allocation of over multiple subnets distributed client 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 are, they can advantageously easily in the inventive concept are included. For example, the selected clients are set up such that in addition other selected clients also central DNS servers and / or DHCP server for the IP address of the SA can this server SRV query. According to one embodiment , a DNS or DHCP server set up be that he is like a selected client within the meaning of Inventive method behaves. The inclusion existing central information services, such as DNS or DHCP, the time period for searching for the server and the distribution be reduced by its IP address on.

requires an implementation of the inventive method no modification to the server to be searched, but only supportive to the process client. According to the present Embodiment is a method of supporting Client to the selection module CSEL for selecting a Clients supplement its own subnetwork. Furthermore, a procedural supporting client preferably embody such he selected an exchange of information with the Client's own subnet support, and that he Requests of selected clients on other subnets to the selected can forward client's own subnet. at a selectable client is in accordance with the present embodiment, in addition, a search engine, here SM, the subnet Search for selected clients as well as a Memory, here MEM for storing the server IP address SA provide. Furthermore, in a selectable client is also an output module, here OUT to provide to the stored Server IP address SA to inquiring selected clients outside its own subnet and to requesting clients its own subnetwork to forward.