Abstract:
A method and a system for establishing a connection between a first computer of a first computer network and a resource of a second computer network via a third network through a gateway intervening between the second computer network and the third network. A requester issues a request for a connection from the first computer to the resource by specifying a name of the resource. A temporary IP number is returned to the first computer in answer to the request. The temporary IP number is mapped to a tunnel to the gateway. The gateway administrates the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource and data packets arriving from the resource destined to the first computer, are routed through the tunnel to the first computer.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to a method and a system for communicating between different networks, especially from one network to a host within a private network.  
         BACKGROUND TO THE INVENTION  
         [0002]    The Internet is a collection of networks that can interwork. Clients connected to one network can access resources on other networks because data packets are routed from one network to the other. The Internet Protocol (IP) makes this possible. The same protocol can also be used to create private networks that are not directly connected to the Internet. These networks are called intranets. These intranets can be extended over a large area to remote offices using private lines. They are in a way the same intranet because there is a single authority that controls the network. Instead of private lines, an intranet can also be extended using the public internet as a tunneling medium. Instead of coupling an intranet directly to the Internet, the data traffic for a remote office is encapsulated and encrypted before being forwarded over the internet to the remote office. At the remote office, the reverse is done and the data package is placed in the local network. This is usually called a Virtual Private Network (VPN). For the end users it looks like a single private network, but the public Internet is used to securely transport data traffic between remote places.  
           [0003]    In the Internet Protocol (IP) routing decisions are made on addresses. An address in IP is a 32-bit number. On the Internet, every host requires at least one unique number to be able to communicate. This unique number cannot be used by any other host on the Internet. A special official body allocates these IP numbers, and Internet routers all over the world must know how to map these IP numbers to the correct hosts. To simplify the routing and due to some original design choices the 4294967296 possible numbers are running out. For this reason there are a number of number ranges that are reserved which anybody can use privately in e.g. a private intranet. However, IP packets cannot be routed over the Internet with a number within these ranges, and consequently must remain within the private intranet. This creates a problem when users of such an intranet with host numbers in these number ranges want to access the Internet.  
           [0004]    There are two basic very close solutions to this problem, one is the use of a firewall and the other is using network address translation (NAT). Using a firewall, all access to the Internet is terminated at a firewall computer that is connected both to the Internet and to the intranet. This firewall then looks at the access from the intranet and acts as a proxy to the Internet using its own public IP number that is valid on the internet. However, a proxy requires a program that knows about the protocol. The other solution using NAT has a computer acting as a gateway between the Internet and the intranet. Every packet directed to the Internet is processed by a program that replaces/translates the address and port of the packet, and keeps a track of on who&#39;s behalf this translation is done. If the return packet comes, the address is translated back to the original address. NAT is a very transparent solution but unfortunately has some problems with some protocols, which then requires special measures.  
           [0005]    A user does not have to use IP numbers to address a packet. When a user uses a name as an address then a special application, a name server, is used to translate the name into an IP number. On the Internet the Domain Name System (DNS) is used for naming. This is a hierarchical scheme where a DNS server can provide the translation for a domain or it can look up the name via/in another name server. If a DNS server comprises tables for a domain, then it is authoritative for that domain. Each DNS server is registered in a parent DNS server, this is done recursively until the root DNS servers are reached. Private intranets also require special handling of the DNS. A host on the inside of the intranet should not be visible on the outside, i.e. on the Internet, because it has a private number. However, when NAT is used, hosts on the outside of the intranet are required to be present in the local intranet DNS. This is called a split universe DNS.  
           [0006]    The real problems start when someone on the Internet wants private access to a host on an intranet with a private numbering scheme, or when two intranets with private numbering schemes want to connect privately. For example, assume that two companies, each with their own private intranet, decide to co-operate on a project and that they therefore want to share a number of resources on their respective intranets. This will cause a number of problems. The intranets cannot directly be routed to each other because the IP numbers used potentially overlap. Most probably the respective DNS of both companies are set-up as split universe DNSs and thus have no knowledge of each other&#39;s hosts. The normal forwarding to the internet DNS does not help since the domain of the other company does not expose the internal hosts with private IP numbers. Thus, since the internal hosts cannot see each other, it is impossible to route anything between them.  
           [0007]    There have been a number of different solutions put forward. Unfortunately the known solutions either does not work for all protocols or they require complex administration or suffer from both disadvantages. For example, proxying is a solution to the problem. For each service that the companies want to share they have a publicly addressable host that contains a proxy for this service. This proxy does the mapping from the outside to the inside. A disadvantage of proxying is that it requires a significant amount of administration to set them up and then to keep them aligned with the original resources. Another disadvantage is that not all protocols are easy to proxy or have existing proxies. Another solution to the problem is to renumber the intranets so that a non-overlapping address space is created. A single DNS can then be used. However, this is a very complicated and heavy operation making it virtually impossible if the companies only co-operate on a project basis. This solution also requires a significant amount of trust between the parties in question.  
           [0008]    A suggestion has also been disclosed in U.S. Pat. No. 5,898,830 to Wesinger, Jr. et al. (Wesinger). The Wesinger patent discloses a method of setting up virtual hosts in firewalls and using name based routing. The solution allegedly provides a full transparency for the users. However, this solution also only forwards hosts and not networks and it also requires quite a bit of administration.  
           [0009]    There is thus a need to improve the methods of providing access to one or more hosts of a private intranet from the outside of the intranet with full transparency to users and a simple administration.  
         SUMMARY OF THE INVENTION  
         [0010]    An object of the invention is to define a method and a system for transparently accessing hosts within a private intranet.  
           [0011]    Another object of the invention is to define a method and a system for transparently accessing a host within private intranet by name.  
           [0012]    A further object of the invention is to define a method and a system for accessing hosts within a private intranet with minimal administration.  
           [0013]    A still further object of the invention is to define a method and a system for accessing hosts within a private intranet with security control and access control administration at the private intranet.  
           [0014]    The aforementioned objects are achieved according to the invention by a method and a system for establishing a connection between a first computer of a first computer network and a resource, such as a second computer, of a second computer network via a third network through a gateway, such as a firewall, intervening between the second computer network and the third network. A requester issues a request for a connection from the first computer to the resource by specifying a name of the resource. A temporary IP number is returned to the first computer in answer to the request. The temporary IP number is mapped to a tunnel to the gateway. The gateway administrates the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource and data packets arriving from the resource destined to the first computer, are routed through the tunnel to the first computer.  
           [0015]    The aforementioned objects are also achieved according to the invention by a method of establishing a connection between a first computer of a first computer network and a resource of a second computer network via a third network. The connection is established along a route through an intermediate system having an interface to the first computer network, and through a gateway intervening between the second computer network and the third network. The resource belongs to the domain of the gateway. According to the invention the method comprises a number of steps. A first step configuring the intermediate system with a tunnel from the intermediate system to the gateway. A second step mapping the tunnel with a requester and a domain name of the gateway. A third step wherein the requester issues a request for a connection from the first computer to the resource by specifying a name of the resource. A fourth step receiving the request at the intermediate system via the interface. A fifth step using a rule for matching the name of the resource with the gateway. A sixth step mapping the name of the resource to the tunnel. A seventh step returning a temporary IP number to the first computer in answer to the request. An eighth step mapping the temporary IP number to the name of the resource. A ninth step wherein the gateway administrates the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource. And a tenth step wherein the gateway administrating the handling of data packets such that data packets arriving from the resource destined to the first computer, are routed through the tunnel to the first computer via the intermediate system. It is to be understood that the steps according to the invention do not indicate any sequential execution, but is merely a manner to distinguish them.  
           [0016]    The method can advantageously further comprise the step of transmitting a message with the mapping of the temporary IP number to the gateway by means of the tunnel.  
           [0017]    Preferably the step of the gateway administrating the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource, comprises the substep of directing the intermediate system to translate source addresses of data packets addressed to the temporary IP number to be sent through the tunnel. The step of the gateway administrating the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource, can comprise the substep of directing the intermediate system to translate destination addresses of data packets addressed to the temporary IP number to be sent through the tunnel, by means of at least a partial DNS function in the intermediate system.  
           [0018]    Advantageously the step of the gateway administrating the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource, can comprise the substep of the gateway translating source addresses of data packets arriving through the tunnel addressed to the temporary IP number and routing these data packets to the resource. The step of the gateway administrating the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource, can comprise the substep of the gateway translating destination addresses of data packets arriving through the tunnel addressed to the temporary IP number and routing these data packets to the resource. The step of the gateway administrating the handling of data packets such that data packets arriving from the resource destined to the first computer, are routed through the tunnel to the first computer via the intermediate system, can comprise the substep of the gateway translating source and destination addresses of data packets arriving from the resource destined to the first computer, and routing these data packets through the tunnel to the first computer via the intermediate system.  
           [0019]    In some versions the step of the gateway administrating the handling of data packets such that data packets arriving from the resource destined to the first computer, are routed through the tunnel to the first computer via the intermediate system, can comprise the substep of directing the intermediate system to translate source and destination addresses of data packets arriving from the resource via the tunnel destined to the first computer.  
           [0020]    In some versions the third network is a telecommunications network, in other versions it is the Internet, i.e. a computer network.  
           [0021]    Advantageously the rule for matching the name of the resource with the gateway can be based on a mapping, and/or based on a list of hosts, and/or based on a regular or wildcard expression, and/or based on matching a domain name of the name of the resource with the domain name of the gateway.  
           [0022]    Preferably the method further comprises the step of authenticating the requester at the first computer for access to the tunnel.  
           [0023]    In some versions the name of the resource corresponds to a second computer within the second computer network, the second computer belonging to the domain of the gateway and comprising the resource. Then preferably the gateway administrates the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource residing on the second computer. Otherwise in other versions the gateway administrates the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel, are routed to the resource, the resource residing on a proxy of the second computer. Advantageously the proxy to which the gateway routes data packets addressed by the first computer to the temporary IP number, is in dependence on an identity of the requester.  
           [0024]    One or more of the features of the above described different methods according to the invention can be combined in any desired manner, as long as the features are not contradictory.  
           [0025]    The aforementioned objects are achieved in accordance with the invention also by a device arranged to establish a connection between a first computer of a first computer network and a resource of a second computer network via a third network. The connection being established along a route through the device having an interface to the first computer network, and through a gateway intervening between the second computer network and the third network. The resource belongs to the domain of the gateway. According to the invention the device comprises a number of means arranged to carry out the invention. A first means arranged to configure a tunnel from the device to the gateway. A second means arranged to map the tunnel with a requester and a domain name of the gateway. A third means arranged to receive a request, issued by the requester, via the interface for a connection from the first computer to the resource by specifying a name of the resource. A fourth means arranged to use a rule for matching the name of the resource with the gateway. A fifth means arranged to map the name of the resource to the tunnel. A sixth means arranged to return a temporary IP number to the first computer in answer to the request. A seventh means arranged to map the temporary IP number to the name of the resource. An eighth means arranged to cooperate with the gateway administrating the handling of data packets such that data packets addressed by the first computer to the temporary IP number, arriving through the tunnel at the gateway, are routed to the resource. A ninth means arranged to cooperate with the gateway administrating the handling of data packets such that data packets arriving from the resource destined to the first computer, are at the gateway routed through the tunnel to the first computer via the device.  
           [0026]    Different embodiments of the device according to the invention can be reached according to additional features mentioned above in connection with the description of the method according to the invention. The features of the above described different embodiments of a device according to the invention can be combined in any desired manner, as long as no conflict occurs.  
           [0027]    By providing a device and a method for accessing one or more hosts within a private intranet, a plurality of advantages over prior art systems are obtained. According to the invention a route process/connection is made within a requesters network, which could also be a private intranet. Complete transparency is achieved; there is no restriction as to what protocol is used. The requester/user does not have to have any understanding of the set-up, such as the use of special ports or hosts and other network issues. The routing is name based; a requester/user requests access to a name of a host and will get an IP number in return to be used for access to the requested host. A requester is totally unaware that the request was intercepted and a route was set-up to respond to the IP number that was returned to the requester. All authentication and security issues such as access control can be handled by the private intranet to which access is desired. All the set-up at the requester&#39;s side that is required is some means of intercepting DNS requests before they are transferred to the internet. This means can, for example, be located in a gateway to the internet or at some other point logically before the gateway. This intercept means will have one or more tunnels configured to one or more private intranets and will determine if a DNS request is for one of the private intranets or not. If it determines that the DNS request is for one of the private intranets then a route process is set-up with an arbitrary but for the requester valid IP number and a mapping to the corresponding tunnel is made. All access control can be handled at the other end of the tunnel, but in some embodiments some authentication and security is handled by the intercept means. Preferably all address translation is also done at the private intranet side of the tunnel, but in some embodiments at least some of the address translations can be handled directly by the intercept means, preferably under complete control of the private intranet side of the tunnel. Further advantages and variations of the invention will become apparent from the following.  
       
    
    
     DESCRIPTION OF THE FIGURES  
       [0028]    The invention will now be described in more detail for explanatory, and in no sense limiting, purposes, with reference to the following figures, in which  
         [0029]    [0029]FIG. 1 shows a diagram of communication situation to which the invention is suitable,  
         [0030]    [0030]FIG. 2 shows a diagram of an implementation of the invention,  
         [0031]    [0031]FIG. 3 shows a flow chart of an example of an intermediate system processing,  
         [0032]    [0032]FIG. 4 shows a flow chart of an example of a firewall/gateway processing when receiving from a tunnel,  
         [0033]    [0033]FIG. 5 shows a flow chart of an example of a firewall/gateway processing when transferring a data packet from a second computer to a first computer.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0034]    In order to clarify the system according to the invention, some examples of its use will now be described in connection with FIGS.  1  to  5 .  
         [0035]    [0035]FIG. 1 shows a diagram of a communication situation to which the invention is suitable. A user/requestor which is situated at a first computer  101  connected to a first computer network  103 , which network can comprise several computer networks, within a first domain  100 , which can be open or private, desires to communicate/gain access to a second computer  122 , a destination host, connected to a second computer network  124 , which network can also comprise several networks, which in turn is within a second domain  120  which is private. A private domain is a domain which uses a private numbering scheme, i.e. hosts within the domain are not visible from the outside and can thus have the same number as a host on the internet. The first computer  101  and the second computer  122  are interconnected via, for example, an internet  110 , a third computer network, a network, which will most likely comprise many networks, by means of a gateway/firewall  105  between the first computer network  103  and the third computer network  110 , and a firewall/gateway  126  between the second computer network  124  and the third computer network  110 . Other types of interconnections between the gateway/firewall  105  of the first computer network and the firewall/gateway  126  of the second computer network  124  are possible according to the invention. However, any direct ways of ordinary connection between the first computer  101  and the second computer  122  is not possible. The second computer  122  is not visible to the first computer  101  or to an internet  110 , and if it is not visible then it is not ordinarily possible to route data packages from the first computer  101  to the second computer  122 . Several known, less suitable, solutions to this situation have been discussed previously.  
         [0036]    [0036]FIG. 2 shows a diagram of an implementation of the invention. The set-up is the same as in FIG. 1 with a first computer  201 , with a user/requestor, connected to a first computer network  203 , which can comprise several computer networks, which in turn is connected to a gateway/firewall  205 , all  201 ,  203 ,  205  of a first domain  200  which can be open or private. The gateway/firewall  205  is connected between the first computer network  203  and a third computer network  210 . The third computer network  210 , for example the Internet, will most likely comprise many networks. There is also a second computer  222 , a desired destination, which is connected to a second computer network  224 , which can comprise several networks, which in turn is connected to a firewall/gateway  226 , all of a second domain  220  which is a private domain. The firewall/gateway  226  is connected between the third computer network  210  and the second computer network  224 .  
         [0037]    According to the invention there is also an intermediate system  230 , an intercept means, connected somewhere into the first computer network  203 . The intermediate system can be placed anywhere in the first domain  200 , as long as it can intercept any DNS request from the first computer  201  before the request reaches the third computer network  210 . To give a few examples, the intermediate system  230  can be a process running on the gateway/firewall  205 , an intelligent connection box logically connected between the first computer  201  and the gateway/firewall  205 , or even a process running on the first computer  201 . The intermediate system  230  is preferably implemented as close as possible to, if not within, the gateway/firewall  205  to enable as many users/computers in the first domain  200  to have access to it, and thus have the possibilities of the invention. The intermediate system  230  will configure at least one tunnel  231  from the intermediate system to the firewall/gateway  226  of the second domain  220 . A tunnel is a logical network connection between two processes, encapsulating the traffic during transport. Traffic over such a connection is traditionally encrypted to prevent eavesdropping. The tunnel or tunnels are preferably authenticated at regular, or irregular, intervals.  
         [0038]    The intermediate system  230  will intercept DNS requests at least from the user or users and associate connection points/connected computers for which the intermediate system is set-up, in this example the first computer  201 . The intermediate system must at least intercept DNS requests from the first computer  201  before the requests leave the domain  200 . A user wanting a permitted access from the first computer  201  to the second computer  222  requests this by naming the second computer  222 . The DNS request will then be intercepted by the intermediate system  230  which will determine if the requested name has any association with any tunnel  231  that is previously set-up. The determination can be based on a mapping, a list of hosts, or a regular or wildcard expression. In a preferred method the intermediate system  230  will try to match a domain name suffix of the second domain  220  to a domain name suffix of the DNS request for a match to the tunnel  231  of the example. As can be seen, the intermediate system does not have to be set-up with any details as to exactly which host or hosts are requested for within the second domain  220 . If there is a match the intermediate system will set-up a route to the second domain  220  via a tunnel  231  in view of the match, in this case the described tunnel  231 . An IP number, a temporary random IP number, will be generated/made and associated to the route. The generated/given temporary random IP number must at least be valid within the first domain  200  so that communication addressed to that temporary random IP number will be correctly routed to the associated tunnel  231  of the intermediate system  230 . The first computer  201  will get the temporary random IP number back as an answer to its DNS request and then use this temporary random IP number for all communication to the second computer  222 , at least during this session. The communication will end up at the route interface, which in turn will send it down the tunnel for correct routing to the desired destination, the second computer  222 . The temporary random IP number is mapped to the complete name of the DNS request and sent as a message to the gateway/firewall  226  at the other end of the tunnel. The gateway/firewall  226  at the other end of the tunnel  231  will deal with all the details of routing packages to and from the correct desired host, in this case the second computer  222 . Return communications will either have the correct destination, the first computer  201 , when they emerge from the tunnel  231 , or there has been some address translation in the intermediate system  230 , governed by the gateway/firewall  226  of the second domain  220 , in which case the intermediate system  230  will retranslate the communication so that it will be routed correctly within the first domain  200  to the first computer  201 .  
         [0039]    For an even better understanding of the invention, it will be explained in relation to flow diagrams of a specific implementation of the invention. Flow diagrams describe something as a string of events, one after another. The different processes according to the invention are mostly independent event-driven processes. The major difference is that the processes of the invention might not appear in the order described below, but it is believed that the flow diagrams can however provide an easier understanding of the invention.  
         [0040]    [0040]FIG. 3 shows a flow chart of an example of the processes of an intermediate system according to one specific implementation of the invention. In a first step  340  one or more predetermined tunnels are configured and tables/mappings are generated/set-up. A table can, for example, be set-up in a matrix where each line comprises; a user (optionally), a source IP number, a destination domain (e.g. *.ericsson.se), access time or times to the destination domain (optionally), a tunnel to the destination domain. The amount of information comprised in a table and the manner it is stored and mutually associated will vary in dependence of an implementation in question. A table/mapping can preferably be dynamically updated, i.e. information/entries added or deleted from for example a destination domain. In a second step  341  after the first step  340 , authentication of the configured tunnel(s) and of configured users/requesters is done, for example, from which source IP number(s), e.g. the first computer, when, and to which domains access is allowed. In a third step  342  after the second step  341  it is determined if there is any communication to intercept or not, if there is none then it simply returns to itself. If there is some communication to intercept, the procedure continues with a fourth step  343  after the third step  342 . The fourth step  343  determines if the communication was a DNS request or not. If the communication was determined to be a DNS request, then the procedure continues with a fifth step  344  after the fourth step  343 . The fifth step  344  determines if the DNS request is from a configured user, e.g. the first computer, or not. If the DNS request is determined to have originated from a configured user then the procedure continues with a sixth step  345  after the fifth step  344 . The sixth step  345  tries to match domains, in the configured user&#39;s map/table, with the domain of the DNS request. Thereafter the procedure continues with a seventh step  346  after the sixth step  345 . The seventh step  346  determines if there is a match or not. If there is a match, then the procedure continues with an eighth step  347  after the seventh step  346 . The eighth step  347  retrieves the entries of the user&#39;s map/table which correspond to the match of the seventh step  346  and also generates a temporary IP number, a temporary random IP number, which is a valid IP number in view of the place of the intermediate system. The intermediate system dynamically allocates a temporary IP number. Thereafter the procedure continues with a ninth step  348  after the eighth step  347 . The ninth step  348  maps the temporary random IP number to a tunnel according to the retrieved entries in the user&#39;s map/table. Thereafter the procedure continues with a tenth step  349  after the ninth step  348 . The tenth step  349  will send a message through the tunnel with a mapping of the temporary random IP number with the complete DNS request, i.e. the complete name of the desired destination, e.g. the second computer. Thereafter the procedure continues with an eleventh step  350  after the tenth step  349 . The eleventh step  350  returns the temporary random IP number to the requester, e.g. the first computer, in answer to the DNS request.  
         [0041]    If in the fourth step  343  it was determined that it was not a DNS request, then the procedure continues with a twelfth step  351  after the fourth step  343 . The twelfth step determines if the communication is a data packet or not. If it is determined to be a data packet then the procedure continues with a thirteenth step  352  after the twelfth step  351 . The thirteenth step  352  determines if the destination IP number of the data packet matches with any temporary random IP number which is mapped with the source IP number of the data packet. If there is a match, then the procedure continues with a fourteenth step  353  after the thirteenth step  352 . The fourteenth step  353  sends the data packet in a tunnel according to the match and corresponding mapping/table entry. If it was determined in the twelfth step  351  that it was not a data packet, then the procedure continues with a fifteenth step  354  after the twelfth step  351 . The fifteenth step  354  will ensure that the communication gets attention by means of some other processing. If it was determined in the thirteenth step  352  that there was no match, then the procedure continues with a sixteenth step  355  after the thirteenth step  352 . The sixteenth step  355  provides normal routing of the data packet. If it was determined in the fifth step  344  that the DNS request was not from a configured user or if it was determined in the seventh step  346  that there is no match in the users domain name table, then the procedure continues with a seventeenth step  356  after the fifth step  344  or after the seventh step  346 . The seventeenth step  356  provides a normal DNS request processing.  
         [0042]    What happens next? We have opened a route interface process at the intermediate system and are now sending data packets and messages down a tunnel. FIG. 4 shows a flow chart of an example of a second domain firewall/gateway processing when receiving from a tunnel. In a first step  460  the procedure waits for some communication received from a tunnel, and returns to itself as long as there is none. However when there is some communication received from a tunnel then the procedure continues with a second step  461  after the first step  460 . The second step  461  determines if the communication is a message with a mapping of a temporary random IP number with a DNS request, or not, e.g a message sent by the tenth step  349  of FIG. 3. If it determined that it is not a message with a mapping then the procedure continues with a third step  462  after the second step  461 . The third step  462  determines if the communication is a data packet to be routed or not. If it is determined that it is a data packet to be routed then the procedure continues with a fourth step  463  after the third step  462 . The fourth step  463  determines if there exists a mapping/table or not for the destination IP number, i.e. a temporary random IP number, of the data packet. If there exists a mapping/table for the destination IP number then the procedure continues with a fifth step  464  after the fourth step  463 . The fifth step  464  determines if security control of the tunnel through which the communication came is OK and still valid. If it is determined that the security of the tunnel is satisfactory, then the procedure continues with a sixth step  465  after the fifth step  464 . The sixth step  465  determines if, according to the table/map, the source IP number, e.g. the IP number of the first computer, of the data packet have allowed access to the destination IP number, i.e. the temporary random IP number, of the data packet. If it is determined that the data packet from the source IP number has access to the destination IP number then the procedure continues with a seventh step  466  after the sixth step  465 . The seventh step  466  translates/re-maps the source IP number, e.g. the IP number of the first computer, to a temporary locally valid IP number, a temporary local IP number. This is done so that the packet can be routed properly in the second domain. After the seventh step  466  the procedure continues with an eighth step  467  which lookups the real local IP number of the destination, e.g. the second computer, by doing a DNS request in the second domain on the name received with the mapping to the temporary random IP number. The procedure then continues with a ninth step  468  after the eighth step  467 . The ninth step  468  translates/re-maps the destination IP number, i.e. the temporary random IP number, of the data packet to the real local IP number of the destination, e.g. the second computer. Thereafter the procedure continues with a tenth step  469  after the ninth step  468 . The tenth step  469  routes the data packet in the second domain to the destination, e.g. the second computer, with the real local IP number as destination and the temporary local IP number as the source.  
         [0043]    If it was determined in the second step  461  that the communication was a map/table message then the procedure continues with an eleventh step  470  after the second step  461 . The eleventh step  470  receives a mapping of a temporary random IP number with a DNS name, e.g. the second computer, of the second domain, and adds this to its mapping. If it was determined in the third step  462  that it was not a data packet to be routed that was received through the tunnel, then the procedure continues with a twelfth step  471  after the third step  462 . The twelfth step  471  does other appropriate processing. If it was determined in the fifth step  464  that the security of the tunnel is not valid then the procedure could continue with a thirteenth step  472  after the fifth step  464 . The thirteenth step  472  will then try to authenticate the tunnel, and then return and continue with the fifth step. If it was determined in the fourth step  463  that there does not exist a mapping/table or if it was determined in the sixth step  465  that the source IP number is not allowed access to the destination IP number, then the procedure continues with a fourteenth step  473  after either the fourth step  463  or the sixth step  465 . The fourteenth will reject request, and not route the data packet, the “destination is unknown”. Preferably security will also be alerted of an attempted breach of security.  
         [0044]    As mentioned, packets must be able to be sent back to the original requester. FIG. 5 shows a flow chart of an example of firewall/gateway processing when transferring a data packet from a second computer to a first computer. In a first step  580  it is checked if there is any communication from within the second computer network, and if not then just return to itself. If there is communication from within the second computer network, then the procedure continues with a second step  581  after the first step  580 . The second step  581  determines if it is a data packet that should be routed. If it is a data packet to be routed then the procedure continues with a third step  582  after the second step  581 . The third step  582  determines if the destination IP number of the data packet is equal to any valid temporary local IP number. If the destination IP number is matched then the procedure continues with a fourth step  583  after the third step  582 . The fourth step retrieves the mapping/table that corresponds to the matched temporary local IP number to thereby find out where, which tunnel, to route the data package. After the fourth step  583  the procedure continues with a fifth step  584  which translates (re-maps) the source IP number, the IP number of the second computer, of the data packet to the temporary random IP number according to table (map). After the fifth step  584  the procedure continues with a sixth step  585  which translates (re-maps) the destination IP number, the temporary local IP number, of the data packet to the IP number of the first computer according to the table (map). Thereafter in a seventh step  586  after the sixth step  585  the data packet is transferred in an appropriate tunnel according to the table (map). If it was determined in the second step  581  that it is not a data packet that is to be routed then the procedure continues with an eighth step  587  after the second step  581  and does some other processing. If it was determined in the third step  582  that the destination IP number of the data packet is not equal to any valid temporary local IP number then the procedure continues with a ninth step  588  after the third step  582  and does a normal routing of the data packet.  
         [0045]    The present invention can be put into apparatus-form either as pure hardware, as pure software or as a combination of both hardware and software. If the method according to the invention is realized in the form of software, it can be completely independent or it can be one part of a larger program. The software can suitably be located in a general-purpose computer or in a dedicated computer.  
         [0046]    As a summary, the invention can basically be described as a method of accessing one or more hosts within a private network by means of a route interface process.  
         [0047]    The invention is not limited to the embodiments described above but may be varied within the scope of the appended patent claims.  
         [0048]    [0048]FIG. 1 a diagram of communication situation to which the invention is suitable,  
         [0049]    [0049] 100  open or private first domain  
         [0050]    [0050] 101  user/requestor, a first computer,  
         [0051]    [0051] 103  a first computer network, can comprise several computer networks,  
         [0052]    [0052] 105  gateway/firewall between the first computer network and a third computer network,  
         [0053]    [0053] 110  internet, the third network, will most likely comprise many networks  
         [0054]    [0054] 120  private second domain,  
         [0055]    [0055] 122  a second computer, a destination,  
         [0056]    [0056] 124  a second computer network, can comprise several networks,  
         [0057]    [0057] 126  a firewall/gateway between the second computer network and the third computer network.  
         [0058]    [0058]FIG. 2 a diagram of an implementation of the invention,  
         [0059]    [0059] 200  open or private first domain,  
         [0060]    [0060] 201  user/requestor, a first computer, a source,  
         [0061]    [0061] 203  a first computer network, can comprise several computer networks,  
         [0062]    [0062] 205  gateway/firewall between the first computer network and a third computer network,  
         [0063]    [0063] 210  internet, the third computer network, will most likely comprise many networks,  
         [0064]    [0064] 220  private second domain,  
         [0065]    [0065] 222  a second computer, a destination,  
         [0066]    [0066] 224  a second computer network, can comprise several networks, to which the second computer is connected,  
         [0067]    [0067] 226  a firewall/gateway between the third computer network and the second computer network, the second computer,  
         [0068]    [0068] 230  an intermediate system between the third computer network and the first computer, the source,  
         [0069]    [0069] 231  a tunnel from the intermediate system to the firewall.  
         [0070]    [0070]FIG. 3 flow chart of an example of intermediate system processing,  
         [0071]    [0071] 340  configure tunnels and generate tables/mappings  
         [0072]    [0072] 341  from  340 : authentication of tunnel(s) and of users/requesters, for example from which source IP number(s), e.g. the first computer, when, and to which domains,  
         [0073]    [0073] 342  from  341  or no from itself: any communication ?  
         [0074]    [0074] 343  yes from  342 : is it a DNS request ?  
         [0075]    [0075] 344  yes from  343 : is it from a configured user, e.g. the first computer ?  
         [0076]    [0076] 345  yes from  344 : try to match domains, in the configured user&#39;s table, with the domain of the DNS request,  
         [0077]    [0077] 346  from  345 : is there a match,  
         [0078]    [0078] 347  yes from  346 : get map/table and also generate a temporary IP number, a temporary random IP number, which is a valid IP number in view of the place of the intermediate system,  
         [0079]    [0079] 348  from  347 : map the temporary IP number to a tunnel according to the retrieved map/table,  
         [0080]    [0080] 349  from  348 : send message through tunnel with mapping of temporary random IP number with the DNS request,  
         [0081]    [0081] 350  from  349 : return temporary random IP number to requester, e.g. the first computer, in answer to the DNS request,  
         [0082]    [0082] 351  no from  343 : is it a data packet ?  
         [0083]    [0083] 352  yes from  351 : does destination IP number of the data packet match with any temporary random IP number which is mapped with the source IP number of the data packet,  
         [0084]    [0084] 353  yes from  352 : send data packet in a tunnel according to mapping/table entry,  
         [0085]    [0085] 354  no from  351 : other processing,  
         [0086]    [0086] 355  no from  352 : normal routing of data packet,  
         [0087]    [0087] 366  no from  344  or no from  346 : do a normal DNS request processing.  
         [0088]    [0088]FIG. 4 flow chart of an example of firewall processing when receiving from a tunnel,  
         [0089]    [0089] 460  no from itself: communication received from a tunnel?  
         [0090]    [0090] 461  yes from  460 : is the communication a map/table message?  
         [0091]    [0091] 462  no from  461 : is the communication a data packet to be routed?  
         [0092]    [0092] 463  yes from  462 : does there exist a mapping/table for the destination IP number, i.e. a temporary random IP number, of the data packet?  
         [0093]    [0093] 464  yes from  463  or from  472 : security control of tunnel, through which the communication came, is it OK, still valid ?  
         [0094]    [0094] 465  yes from  464 : does, according to the table/map, the source IP number, e.g. the IP number of the first computer, of the data packet have allowed access to the destination IP number, i.e. the temporary random IP number, of the data packet ?  
         [0095]    [0095] 466  yes from  465 : translate/remap source IP number, e.g. the IP number of first computer, to a temporary locally valid IP number, a temporary local IP number,  
         [0096]    [0096] 467  from  466 : lookup of real local IP number of destination, e.g. the second computer, by DNS in the second domain,  
         [0097]    [0097] 468  from  467 : translate/remap destination IP number, i.e. the temporary random IP number, of the data packet to the real local IP number of the destination, e.g. the second computer,  
         [0098]    [0098] 469  from  468 : route the data packet in the second domain to the destination, e.g. the second computer, with the real local IP number as destination and the temporary local IP number as the source,  
         [0099]    [0099] 470  yes from  461 : receive a mapping of a temporary random IP number with a DNS name, e.g. the second computer, of the second domain,  
         [0100]    [0100] 471  no from  462 : do other processing,  
         [0101]    [0101] 472  no from  464 : authenticate tunnel,  
         [0102]    [0102] 473  no from  463  or no from  465 : reject request, do not route data packet, “destination unknown”, alarm security of an attempted break in.  
         [0103]    [0103]FIG. 5 flow chart of an example of firewall processing when transferring a data packet from a second computer to a first computer,  
         [0104]    [0104] 580  no from itself: communication from within the second computer network ?  
         [0105]    [0105] 581  yes from  580 : is it a data packet that should be routed ?  
         [0106]    [0106] 582  yes from  581 : is the destination IP number of the data packet equal any valid temporary local IP number ?  
         [0107]    [0107] 583  yes from  582 : get mapping/table to find out where, which tunnel, to route the data package,  
         [0108]    [0108] 584  from  583 : translate (remap) the source IP number, the IP number of the second computer, of the data packet to temporary random IP number according to table (map),  
         [0109]    [0109] 585  from  584 : translate (remap) the destination IP number, the temporary local IP number, of the data packet to the IP number of the first computer according to the table (map),  
         [0110]    [0110] 586  from  585 : transfer data packet in appropriate tunnel according to table (map)  
         [0111]    [0111] 587  no from  581 : other processing,  
         [0112]    [0112] 588  no from  582 : normal routing.