Patent Publication Number: US-11025542-B2

Title: Routing packets in overlapping address spaces

Description:
TECHNICAL FIELD 
     The present invention relates generally to a method, system, and computer program product for correctly routing data packets. More particularly, the present invention relates to a method, system, and computer program product for routing packets in overlapping address spaces. 
     BACKGROUND 
     Transmission Control Protocol (TCP) is a commonly used communication protocol used for communicating packet data from one data processing system to another over a data network. Internet Protocol (IP) is an addressing protocol to handle the addressing of the TCP data packets. Together, the layers of the two protocols are implemented as a TCP/IP stack for constructing, sending, and receiving the packets from one data processing system to another data processing system across data networks. 
     IP version 4 (IPv4) is the fourth version of IP which sets out internet addresses in the form of four octets. An octet is eight bits (each bit capable of representing a binary 0 value or a binary 1 value). The 32-bit IPv4 address takes the form of “A.B.C.D”, where A, B, C, and D are each an octet. Each octet is capable of representing 256 Base 10 values, 0-255. The Base 10 value 0 is a reserved value of an octet and usually indicates a group of other Base 10 numbers of a subnet that are permissible in that octet. A subnet is a part of a network in which at least one octet of the addressing is common with other parts of the network, and a differing octet takes on different values within the part. 
     Hereinafter, a reference to a first octet is a reference to the “A” octet in the above IPv4 representation. Similarly, a reference to a second octet is a reference to the “B” octet, a reference to a third octet is a reference to the “C” octet, and a reference to a fourth octet is a reference to the “D” octet in the above IPv4 representation. For example, in an example IP address 192.168.1.2, the first octet has the value 192 in Base 10, the second octet has the value 168 in Base 10, the third octet has the value 1 in Base 10, and the forth octet has the value 2 in Base 10. Hereinafter, unless an octet is represented in binary, or unless expressly distinguished where used, a value of an octet refers to a Base 10 value represented in the octet. 
     Some IPv4 address spaces are reserved for internal use within a local area network (LAN). For example, 192.0.0.0 and 10.0.0.0 are two address spaces which are supposed to be configured for uniqueness within only a LAN, and are not supposed to be unique across Wide Area Networks (WAN). Internet Engineering Task Force (IETF) document ‘Request for Comments-1918’ (RFC-1918) identifies that the following IPV4 address ranges have been reserved by Internet Assigned Numbers Authority (IANA) for private Internets: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Therefore, as an example, two different LANs can each implement 10.x.y.z address, e.g., 10.2.3.4, such that 10.2.3.4 will be uniquely associated with a network interface of a target system or application, the uniqueness being valid only with each respective LAN. 
     SUMMARY 
     The illustrative embodiments provide a method, system, and computer program product. An embodiment includes a method that analyzes, at an outbound end of a tunnel from a first data network, a packet to determine whether the packet is to be directed to a local target in the first data network or to be sent over the tunnel to a remote target in a second data network, wherein a target address of the packet is present in both the first data network and the second data network. The embodiment changes, responsive to the packet being directed to the remote target in the second data network, an octet in the target address of the packet from a first value to a second value, the changing forming a modified packet. The embodiment causes, responsive to storing the second value of the octet, the modified packet to be sent to the tunnel for delivery to the second data network. 
     An embodiment includes a computer usable program product. The computer usable program product includes one or more computer-readable storage devices, and program instructions stored on at least one of the one or more storage devices. 
     An embodiment includes a computer system. The computer system includes one or more processors, one or more computer-readable memories, and one or more computer-readable storage devices, and program instructions stored on at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of the illustrative embodiments when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  depicts a block diagram of a network of data processing systems in which illustrative embodiments may be implemented; 
         FIG. 2  depicts a block diagram of a data processing system in which illustrative embodiments may be implemented; 
         FIG. 3  depicts a block diagram of an example configuration for routing packets in overlapping address spaces in accordance with an illustrative embodiment; 
         FIG. 4  depicts a block diagram of an application for routing packets in overlapping address spaces in accordance with an illustrative embodiment; 
         FIG. 5  depicts a flowchart of an example process in routing packets in overlapping address spaces in accordance with an illustrative embodiment; and 
         FIG. 6  depicts a flowchart of another process in routing packets in overlapping address spaces in accordance with an illustrative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An application or system that sends a packet is hereinafter referred to as a “source” system, or simply a “source”. A LAN within which the source system operates is hereinafter referred to as a “local” network. An application or system that receives a packet is hereinafter referred to as a “target” system, or simply a “target”. A LAN within which the target system operates is hereinafter referred to as a “remote” network. 
     A reference to a “network” is a reference to a physical LAN or a virtual LAN unless specifically distinguished where used. A “gateway” is a suitable type of system that routes packets originating from a source within a network, arriving for a target inside the network, or both. Generally, a gateway can be implemented using one or more routers, one or more firewalls, or a combination of similarly functioning networking components. In the illustrative embodiments, the gateway is a physical or virtual device that is operating as a virtual private network (VPN) endpoint, which sends outbound packets from a source to a VPN for delivery to a target on the remote end of the VPN. 
     A source within one network (local-1 network) often has to send a data packet to a target in another network. Sometimes the other network (local-2 network) is also on the same side of the gateway as the local-1 network in which the source is operating. At other times, the other network (remote-1 network) may be on the opposite side of the gateway from the local-1 network of the source. The illustrative embodiments recognize that in some cases, the local-2 network and the remote-1 network may both have implemented IPv4 addressing that overlaps for at least some addresses. For example, the local-2 network may have implemented a 10.55.104.10 address and the remote-1 network may also have implemented a 10.55.104.10 address. 
     When a source in local-1 network sends a packet to 10.55.104.10 address, a confusion arises as to whether the packet should go to the 10.55.104.10 target in local-2 network or the 10.55.104.10 target in remote-1 network. A gateway receiving the packet from local-1 network may misroute the packet to local-2 target when the packet was supposed to go to remote-1 target and vice-versa, or drop the packet. Both such situations are problematic and a solution is needed to allow the gateway to correctly route the packet to the packet&#39;s intended destination. 
     The illustrative embodiments recognize that the presently available tools or solutions do not address these needs/problems or provide adequate solutions for these needs/problems. The illustrative embodiments used to describe the invention generally address and solve the above-described problems and other related problems by routing packets in overlapping address spaces. 
     An embodiment can be implemented as a software application. The application implementing an embodiment, or one or more components thereof, can be configured as a modification of an existing gateway—i.e., a native application in the gateway, as an application executing in a data processing system—such as a central cloud controller device—communicating with an existing gateway over a local area network (LAN)—i.e., a local application on the LAN, as an application executing in a data processing system communicating with an existing gateway over a wide area network (WAN)—i.e., a remote application on the WAN, as a separate application that operates in conjunction with an existing gateway in other ways, a standalone application, or some combination thereof. 
     An embodiment operates to process an outbound packet. The embodiment operates in conjunction with a gateway that can route a packet from a source in a local network (local-1) to a VPN for a target in a remote network on the other end of the VPN, and route a packet from the source in local-1 to a target in another local network (local-2) which is on the same side of the gateway. 
     The embodiment detects an outbound packet from a source in local-1 network. The embodiment determines whether the target address in the packet is in a sub-domain of the remote network. When the target address in the packet is an address in the remote network, the embodiment swaps an octet—i.e. changes an existing value of the octet—in the target address with a new value of the octet. 
     The determination whether a target address is in a remote network is governed by a set of address records. An address record is configured to inform the gateway whether a subnet is on the local side of the gateway or the remote side of the gateway. 
     For example, when the source cannot be modified, an address record uses a port number to distinguish between a subnet on the local side and a subnet on the remote side of the gateway. For example, in one example address record, if the source sends the packet to 10.55.104.10:222, where 222 is a port number, the address 10.55.104.10 is deemed to be on the remote side whereas if the source sends the packet to 10.55.104.10:80, where 80 is a port number, the address 10.55.104.10 is deemed to be on the local side. Any number of address records can similarly be configured for port-number based distinguishing method according to the illustrative embodiments. 
     As another example, when the source can be modified, the source can be programmed to use different source identifiers, e.g., different source IP addresses when sending to a target address in an overlapping address space. In such a case, an address record uses a source identifier to distinguish between a subnet on the local side and a subnet on the remote side of the gateway. For example, in one example address record, if the source sends the packet to 10.55.104.10 using a source identifier 10.2.1.1, where 10.2.1.1 is a source address, the address 10.55.104.10 is deemed to be on the remote side, whereas if the source sends the packet to 10.55.104.10 using a source identifier 10.2.1.2, where 10.2.1.2 is a different source address for the same source, the address 10.55.104.10 is deemed to be on the local side. 
     Any other identifier can be used instead of a source address in this manner so long as the source identifier can be carried in the packet and is readable by the gateway. Any number of address records can similarly be configured for source identifier based distinguishing method according to the illustrative embodiments. 
     The swap of an octet—i.e., changing the octet value from one value to another—in a target address is governed by a set of swapping rules. A swapping rule provides the gateway a replacement or swap value if the gateway finds a particular value in an octet of the target address in a packet. 
     In one embodiment, a single rule can be configured to determine whether a subnet of the target address is in a remote network, and the replacement octet value to use, if so. 
     For example, the target address may be 10.2.15.34 in the packet arriving from the source. An address record might provide that 10.2.0.0 subnet is in a remote network. Accordingly, a swapping rule might provide that the first octet should be replaced with a value 2. Using the address record and the swapping rule, the gateway changes the target address from 10.2.15.34 to 2.2.15.34. 
     The modified target address formed as a result of the swapping now allows the packet to be routed to a path that leads from the gateway to the VPN. This routing of the packet with the modified target address is performed using the presently available routing methods, e.g., using a routing table. 
     If the target address in the packet is not in a subnet on a remote network, then the embodiment causes no swapping of the octet. Accordingly, the gateway causes the packet to be routed to the same side of the gateway as the local-1 network, e.g., by sending the packet to a backend router that facilitates communication between various local networks such as between local-1 network and local-2 network. 
     When the packet reaches the backend router, the backend router delivers the packet to the target in the local-2 network. Thus, the packet is correctly routed to a target in a local network on the same side of the gateway or on a remote network the opposite side of the gateway from the source even though the local network and the remote network might have overlapping address spaces. 
     Another embodiment operates to process an inbound packet. The embodiment operates in conjunction with a gateway that can route a received packet to a target in the remote network. For example, such an embodiment operates to allow a gateway operating in conjunction with the remote network to receive the packet that was transmitted over the VPN with the modified target address described earlier. 
     The embodiment determines that a received packet has a swapped octet. The embodiment makes this determination using a swap-back rule. A swap-back rule is configured to change a value of an octet in the target address of a received packet from the value contained in the octet in the received packet to an octet value that was originally configured by the source of the received packet. 
     For example, suppose that the modified target address in the received packet is 2.2.15.34 for the reasons described above. A swap-back rule determines that if the first octet has a value “2”, the value of that octet should be changed to “10”. Accordingly, the swap-back rule causes the receiving gateway to change the target address from 2.2.15.34 back to 10.2.15.34. the receiving gateway can now route the modified received packet to the intended target in the remote network. The routing to the target inside the remote network can be accomplished using existing routing methods, such as a routing table. 
     In another embodiment, the octet swapping functions and the octet swap-back functions are implemented together. Such a combined implementation allows for the correct routing of packets in both directions of the data traffic when overlapping address spaces exist on both sides of a VPN. 
     The manner of routing packets in overlapping address spaces described herein is unavailable in the presently available methods. A method of an embodiment described herein, when implemented to execute on a device or data processing system, comprises substantial advancement of the functionality of that device or data processing system in correctly routing packets when the packet address has an octet that is used by at least one network on the local side of the gateway and at least one network on the remote side of the gateway. 
     The illustrative embodiments are described with respect to certain types of addresses, subnets, octet values, records, rules, gateways, networks, sources, targets, devices, data processing systems, environments, components, and applications only as examples. Any specific manifestations of these and other similar artifacts are not intended to be limiting to the invention. Any suitable manifestation of these and other similar artifacts can be selected within the scope of the illustrative embodiments. 
     Furthermore, the illustrative embodiments may be implemented with respect to any type of data, data source, or access to a data source over a data network. Any type of data storage device may provide the data to an embodiment of the invention, either locally at a data processing system or over a data network, within the scope of the invention. Where an embodiment is described using a mobile device, any type of data storage device suitable for use with the mobile device may provide the data to such embodiment, either locally at the mobile device or over a data network, within the scope of the illustrative embodiments. 
     The illustrative embodiments are described using specific code, designs, architectures, protocols, layouts, schematics, and tools only as examples and are not limiting to the illustrative embodiments. Furthermore, the illustrative embodiments are described in some instances using particular software, tools, and data processing environments only as an example for the clarity of the description. The illustrative embodiments may be used in conjunction with other comparable or similarly purposed structures, systems, applications, or architectures. For example, other comparable mobile devices, structures, systems, applications, or architectures therefor, may be used in conjunction with such embodiment of the invention within the scope of the invention. An illustrative embodiment may be implemented in hardware, software, or a combination thereof. 
     The examples in this disclosure are used only for the clarity of the description and are not limiting to the illustrative embodiments. Additional data, operations, actions, tasks, activities, and manipulations will be conceivable from this disclosure and the same are contemplated within the scope of the illustrative embodiments. 
     Any advantages listed herein are only examples and are not intended to be limiting to the illustrative embodiments. Additional or different advantages may be realized by specific illustrative embodiments. Furthermore, a particular illustrative embodiment may have some, all, or none of the advantages listed above. 
     With reference to the figures and in particular with reference to  FIGS. 1 and 2 , these figures are example diagrams of data processing environments in which illustrative embodiments may be implemented.  FIGS. 1 and 2  are only examples and are not intended to assert or imply any limitation with regard to the environments in which different embodiments may be implemented. A particular implementation may make many modifications to the depicted environments based on the following description. 
       FIG. 1  depicts a block diagram of a network of data processing systems in which illustrative embodiments may be implemented. Data processing environment  100  is a network of computers in which the illustrative embodiments may be implemented. Data processing environment  100  includes network  102 . Network  102  is the medium used to provide communications links between various devices and computers connected together within data processing environment  100 . Network  102  may include connections, such as wire, wireless communication links, or fiber optic cables. 
     Clients or servers are only example roles of certain data processing systems connected to network  102  and are not intended to exclude other configurations or roles for these data processing systems. Server  104  and server  106  couple to network  102  along with storage unit  108 . Software applications may execute on any computer in data processing environment  100 . Clients  110 ,  112 , and  114  are also coupled to network  102 . A data processing system, such as server  104  or  106 , or client  110 ,  112 , or  114  may contain data and may have software applications or software tools executing thereon. 
     Only as an example, and without implying any limitation to such architecture,  FIG. 1  depicts certain components that are usable in an example implementation of an embodiment. For example, servers  104  and  106 , and clients  110 ,  112 ,  114 , are depicted as servers and clients only as example and not to imply a limitation to a client-server architecture. As another example, an embodiment can be distributed across several data processing systems and a data network as shown, whereas another embodiment can be implemented on a single data processing system within the scope of the illustrative embodiments. Data processing systems  104 ,  106 ,  110 ,  112 , and  114  also represent example nodes in a cluster, partitions, and other configurations suitable for implementing an embodiment. 
     Device  132  is an example of a device described herein. For example, device  132  can take the form of a smartphone, a tablet computer, a laptop computer, client  110  in a stationary or a portable form, a wearable computing device, or any other suitable device. Any software application described as executing in another data processing system in  FIG. 1  can be configured to execute in device  132  in a similar manner. Any data or information stored or produced in another data processing system in  FIG. 1  can be configured to be stored or produced in device  132  in a similar manner. 
     Application  105 A implements an embodiment described herein. Application  105 B implements another embodiment described herein. As an example, assume that within environment  100 , application  103  is a source that exists in a local-1 network  102 A and application  107  is a local target exists in a local-2 network  102 B. As an example, networks  102 A and  102 B may be different virtual LANs within environment  100  and communication between networks  102 A and  102 B is enabled by a backend router (not shown). Source  103  sends packets out of local-1 network  102 A via local endpoint  142 . Local endpoint  142  can be implemented using a gateway as described herein. Application  105 A need not necessarily be implemented within local endpoint  142  but may operate in conjunction therewith in any suitable manner as described herein. 
     Repository  108  stores data  109 . Data  109  comprises a set of address records (for port-based distinction or source id based distinction, or both), and a set of swapping rules. Local endpoint  142  with the functionality imparted by application  105 A uses data  109  to route a packet from source  103  correctly in a manner described herein. Data  109  in repository  108  may also include a set of swap-back rules for use when local endpoint  142  receives a packet in which an octet has been swapped. 
     Within environment  101 , application  152  is a remote target in remote network  148 . Further assume that local-2 network in environment  100  and remote network  148  have an overlap in their address-spaces in at least one octet. Target  152  in system  150  on remote network  148  receives data packets over VPN  144  via remote endpoint  146 . Remote endpoint  146  can be implemented using a gateway as described herein. Application  105 B need not necessarily be implemented within remote endpoint  146  but may operate in conjunction therewith in any suitable manner as described herein. 
     Repository  154  stores data  156 . Data  156  comprises a set of swap-back rules for use when local endpoint  146  receives a packet in which an octet has been swapped as described herein. Remote endpoint  146  with the functionality imparted by application  105 B uses data  156  to route a packet to target  152  correctly in a manner described herein. Data  156  in repository  154  may also include a set of address records (for port-based distinction or source id based distinction, or both), and a set of swapping rules for use when application  152  has to send a packet to one of the targets in one of the networks that have an address space overlap. 
     Servers  104  and  106 , storage unit  108 , and clients  110 ,  112 , and  114 , and device  132  may couple to network  102  using wired connections, wireless communication protocols, or other suitable data connectivity. Clients  110 ,  112 , and  114  may be, for example, personal computers or network computers. 
     In the depicted example, server  104  may provide data, such as boot files, operating system images, and applications to clients  110 ,  112 , and  114 . Clients  110 ,  112 , and  114  may be clients to server  104  in this example. Clients  110 ,  112 ,  114 , or some combination thereof, may include their own data, boot files, operating system images, and applications. Data processing environment  100  may include additional servers, clients, and other devices that are not shown. 
     In the depicted example, data processing environment  100  may be the Internet. Network  102  may represent a collection of networks and gateways that use the Transmission Control Protocol/Internet Protocol (TCP/IP) and other protocols to communicate with one another. At the heart of the Internet is a backbone of data communication links between major nodes or host computers, including thousands of commercial, governmental, educational, and other computer systems that route data and messages. Of course, data processing environment  100  also may be implemented as a number of different types of networks, such as for example, an intranet, a local area network (LAN), or a wide area network (WAN).  FIG. 1  is intended as an example, and not as an architectural limitation for the different illustrative embodiments. 
     Among other uses, data processing environment  100  may be used for implementing a client-server environment in which the illustrative embodiments may be implemented. A client-server environment enables software applications and data to be distributed across a network such that an application functions by using the interactivity between a client data processing system and a server data processing system. Data processing environment  100  may also employ a service oriented architecture where interoperable software components distributed across a network may be packaged together as coherent business applications. Data processing environment  100  may also take the form of a cloud, and employ a cloud computing model of service delivery for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g. networks, network bandwidth, servers, processing, memory, storage, applications, virtual machines, and services) that can be rapidly provisioned and released with minimal management effort or interaction with a provider of the service. 
     With reference to  FIG. 2 , this figure depicts a block diagram of a data processing system in which illustrative embodiments may be implemented. Data processing system  200  is an example of a computer, such as servers  104  and  106 , or clients  110 ,  112 , and  114  in  FIG. 1 , or another type of device in which computer usable program code or instructions implementing the processes may be located for the illustrative embodiments. 
     Data processing system  200  is also representative of a data processing system or a configuration therein, such as data processing system  132  in  FIG. 1  in which computer usable program code or instructions implementing the processes of the illustrative embodiments may be located. Data processing system  200  is described as a computer only as an example, without being limited thereto. Implementations in the form of other devices, such as device  132  in  FIG. 1 , may modify data processing system  200 , such as by adding a touch interface, and even eliminate certain depicted components from data processing system  200  without departing from the general description of the operations and functions of data processing system  200  described herein. 
     In the depicted example, data processing system  200  employs a hub architecture including North Bridge and memory controller hub (NB/MCH)  202  and South Bridge and input/output (I/O) controller hub (SB/ICH)  204 . Processing unit  206 , main memory  208 , and graphics processor  210  are coupled to North Bridge and memory controller hub (NB/MCH)  202 . Processing unit  206  may contain one or more processors and may be implemented using one or more heterogeneous processor systems. Processing unit  206  may be a multi-core processor. Graphics processor  210  may be coupled to NB/MCH  202  through an accelerated graphics port (AGP) in certain implementations. 
     In the depicted example, local area network (LAN) adapter  212  is coupled to South Bridge and I/O controller hub (SB/ICH)  204 . Audio adapter  216 , keyboard and mouse adapter  220 , modem  222 , read only memory (ROM)  224 , universal serial bus (USB) and other ports  232 , and PCI/PCIe devices  234  are coupled to South Bridge and I/O controller hub  204  through bus  238 . Hard disk drive (HDD) or solid-state drive (SSD)  226  and CD-ROM  230  are coupled to South Bridge and I/O controller hub  204  through bus  240 . PCI/PCIe devices  234  may include, for example, Ethernet adapters, add-in cards, and PC cards for notebook computers. PCI uses a card bus controller, while PCIe does not. ROM  224  may be, for example, a flash binary input/output system (BIOS). Hard disk drive  226  and CD-ROM  230  may use, for example, an integrated drive electronics (IDE), serial advanced technology attachment (SATA) interface, or variants such as external-SATA (eSATA) and micro-SATA (mSATA). A super I/O (SIO) device  236  may be coupled to South Bridge and I/O controller hub (SB/ICH)  204  through bus  238 . 
     Memories, such as main memory  208 , ROM  224 , or flash memory (not shown), are some examples of computer usable storage devices. Hard disk drive or solid state drive  226 , CD-ROM  230 , and other similarly usable devices are some examples of computer usable storage devices including a computer usable storage medium. 
     An operating system runs on processing unit  206 . The operating system coordinates and provides control of various components within data processing system  200  in  FIG. 2 . The operating system may be a commercially available operating system for any type of computing platform, including but not limited to server systems, personal computers, and mobile devices. An object oriented or other type of programming system may operate in conjunction with the operating system and provide calls to the operating system from programs or applications executing on data processing system  200 . 
     Instructions for the operating system, the object-oriented programming system, and applications or programs, such as application  105 A and  105 B in  FIG. 1 , are located on storage devices, such as in the form of code  226 A on hard disk drive  226 , and may be loaded into at least one of one or more memories, such as main memory  208 , for execution by processing unit  206 . The processes of the illustrative embodiments may be performed by processing unit  206  using computer implemented instructions, which may be located in a memory, such as, for example, main memory  208 , read only memory  224 , or in one or more peripheral devices. 
     Furthermore, in one case, code  226 A may be downloaded over network  201 A from remote system  201 B, where similar code  201 C is stored on a storage device  201 D. in another case, code  226 A may be downloaded over network  201 A to remote system  201 B, where downloaded code  201 C is stored on a storage device  201 D. 
     The hardware in  FIGS. 1-2  may vary depending on the implementation. Other internal hardware or peripheral devices, such as flash memory, equivalent non-volatile memory, or optical disk drives and the like, may be used in addition to or in place of the hardware depicted in  FIGS. 1-2 . In addition, the processes of the illustrative embodiments may be applied to a multiprocessor data processing system. 
     In some illustrative examples, data processing system  200  may be a personal digital assistant (PDA), which is generally configured with flash memory to provide non-volatile memory for storing operating system files and/or user-generated data. A bus system may comprise one or more buses, such as a system bus, an I/O bus, and a PCI bus. Of course, the bus system may be implemented using any type of communications fabric or architecture that provides for a transfer of data between different components or devices attached to the fabric or architecture. 
     A communications unit may include one or more devices used to transmit and receive data, such as a modem or a network adapter. A memory may be, for example, main memory  208  or a cache, such as the cache found in North Bridge and memory controller hub  202 . A processing unit may include one or more processors or CPUs. 
     The depicted examples in  FIGS. 1-2  and above-described examples are not meant to imply architectural limitations. For example, data processing system  200  also may be a tablet computer, laptop computer, or telephone device in addition to taking the form of a mobile or wearable device. 
     Where a computer or data processing system is described as a virtual machine, a virtual device, or a virtual component, the virtual machine, virtual device, or the virtual component operates in the manner of data processing system  200  using virtualized manifestation of some or all components depicted in data processing system  200 . For example, in a virtual machine, virtual device, or virtual component, processing unit  206  is manifested as a virtualized instance of all or some number of hardware processing units  206  available in a host data processing system, main memory  208  is manifested as a virtualized instance of all or some portion of main memory  208  that may be available in the host data processing system, and disk  226  is manifested as a virtualized instance of all or some portion of disk  226  that may be available in the host data processing system. The host data processing system in such cases is represented by data processing system  200 . 
     With reference to  FIG. 3 , this figure depicts a block diagram of an example configuration for routing packets in overlapping address spaces in accordance with an illustrative embodiment. Endpoint  302  in configuration  300  is an example of local endpoint  142  in  FIG. 1  and has been enabled by the functionality of application  105 A in a manner described herein. Endpoint  304  is an example of remote endpoint  146  in  FIG. 1  and has been enabled by the functionality of application  105 B in a manner described herein. VPN  306  provides a path for data packets to travel from endpoint  302  to endpoint  304 . 
     Application server  308  is an example of source  103 . Source  308  operates in private VLAN 1, which will be referred to a local-1  310 . Local-1  310  has, for example an address space of 26 addresses starting from 10.42.192.128. many other private VLANs might exist on the same side as local-1  310 , as shown. Suppose that private VLAN 2, referred to as local-2  312  has a local target  314  operating therein. Local-2  312  has, for example an address space of 26 addresses in subnet 10.55.104.0, and local target  314  has the IP address 10.55.104.10. backend router  316  facilitates communication between local-1  310 , local-2  312 , and possibly other local side networks. 
     Endpoint server  318  is an example of remote target  152 . Remote target  318  operates in a private network, which will be referred to a remote network  320 . Remote network  320  has, for example an address space of 26 addresses in subnet 10.55.104.0, and remote target  318  has the IP address 10.55.104.10. 
     In an example problematic operation that improved endpoints  302  and  304  solve as described herein, source  308  sends a packet with a target address 10.55.104.10. endpoint  302  resolves whether the packet should reach local target  314  or remote target  318  by using an address record (or port-based differentiation type or source id based differentiation type). If the packet should reach local target  314 , endpoint  302  routes the packet to backend router  316 , which routes the packet to local target  314  in local-2  312 . 
     If the packet should reach remote target  318 , endpoint  302  swaps an octet using a swapping rule. When the packet with the swapped octet reaches endpoint  304 , endpoint  304  uses a swap-back rule to change the octet back to the original value and routing the packet to remote target  318  in remote network  320 . 
     With reference to  FIG. 4 , this figure depicts a block diagram of an application for routing packets in overlapping address spaces in accordance with an illustrative embodiment. Application  402  can be completely or partially implemented at each endpoint of a VPN to impart a selected functionality of an embodiment to each endpoint. For example, in one installation, application  402  can be implemented as a whole to form improved endpoint  302 ; and application  402  can be implemented as a whole to form improved endpoint  304 . Alternatively, in another installation, only components  406 ,  408 , and  412  can be implemented to form improved endpoint  302 ; and only components  410  and  412  can be implemented to form improved endpoint  304 . 
     When application  402  is implemented on the outbound side of a VPN, input  404  to application  402  comprises an outbound packet having a target IP address. When packet  404  has a target IP address that is available in a local-side network as well as a remote-side network, component  406  performs subnet identification using repository  422  operating on the outbound side of the VPN. Particularly, component  406  uses an address records  420  in repository  422 —which may be of the port distinction type, source id distinction type, or a combination thereof) to decide whether the target IP&#39;s subnet is located on the local-side or the remote side of the endpoint where packet  404  is received. 
     If component  406  determines that packet  404  is directed to a target in a local-side network, component  412  routes unchanged packet  404  via a backend router, such as backend router  316  in  FIG. 3 . Packet  414  is an unchanged version of packet  404 . 
     If component  406  determines that packet  404  is directed to a target in a remote-side network, component  408  extracts or selects a suitable swapping rule  418  from repository  422 . Component  408  applies selected swapping rule  418  to packet  404  and modifies an octet in the target address of packet  404 . 
     Component  412  routes the modified version of packet  404 —where an octet of the target address has been swapped—via a VPN, such as VPN  306  in  FIG. 3 . Packet  416  is the modified version of packet  404 . 
     When application  402  is implemented on the inbound side of a VPN, input  404  to application  402  comprises an inbound packet having a target IP address. Component  410  determines whether a swap-back rule  424  in repository  422  (repository  422  now operating on the inbound side of the VPN) applies to the target address of packet  404 . For example, a swap-back rule applies if the target address has a swapped octet. 
     If a swap-back rule  424  applies, component  410  causes a swap-back, i.e., reversion or overwriting of the swapped octet to the value of the octet that would be needed for routing the packet in the network on the inbound side of the VPN. Component  412  then routes the packet with the swapped-back target address to the destination. 
     With reference to  FIG. 5 , this figure depicts a flowchart of an example process in routing packets in overlapping address spaces in accordance with an illustrative embodiment. Process  500  can be implemented in application  402  in  FIG. 4 , such as when application  402  is used on the outbound side of the VPN. 
     The application receives a packet that has a target address (block  502 ). The application determines whether the target address is for a local-side target (block  504 ). For example, the determination of block  504  uses an address record in a manner described herein. 
     If the target address is not for a local-side target (“No” path of block  504 ), the application extracts a swapping rule corresponding to an aspect of the packet—e.g., a target port number, a source identifier, or both (block  506 ). The application changes or swaps an octet value in the target address with a different octet value according to the extracted swapping rule (block  508 ). The application then routes the packet with the (modified) target address (block  510 ). 
     If the target address is for a local-side target (“Yes” path of block  504 ), the application proceeds to block  510 . The application routes the packet according to the unchanged target address at block  510 . 
     In order to route the packet, the application determines whether the target address is one that is to be routed using a VPN to a remote network (block  514 ). If the packet has to be routed to a VPN, e.g., when the target address has a swapped octet (“Yes” path of block  514 ), the application sends the packet to the VPN selected according to the modified target address (block  516 ). If the packet does not have to be routed to a VPN, e.g., when the target address is unchanged (“No” path of block  514 ), the application sends the packet to the local-side network, e.g., via a backend router (block  518 ). The application ends process  500  thereafter. 
     With reference to  FIG. 6 , this figure depicts a flowchart of another process in routing packets in overlapping address spaces in accordance with an illustrative embodiment. Process  600  can be implemented in application  402  in  FIG. 4 , such as when application  402  is used on the inbound side of the VPN. 
     The application receives an inbound packet (block  602 ). The application determines whether the packet has a swapped octet in the target address, e.g., by determining whether the target address satisfies any of the swap-back rules (block  604 ). If a swapped octet exists (“Yes” path of block  604 ), the application swaps back the octet to a value, e.g., a value according to the matching swap-back rule, which allows the packet to be routed to the intended target (block  606 ). The application sends the packet with the swapped back octet to the destination (block  608 ). The application ends process  600  thereafter. 
     If a swapped octet does not exist in the packet (“No” path of block  604 ), the application sends the unmodified inbound packet to the destination (block  608 ). The application ends process  600  thereafter. 
     Thus, a computer implemented method, system or apparatus, and computer program product are provided in the illustrative embodiments for routing packets in overlapping address spaces and other related features, functions, or operations. Where an embodiment or a portion thereof is described with respect to a type of device, the computer implemented method, system or apparatus, the computer program product, or a portion thereof, are adapted or configured for use with a suitable and comparable manifestation of that type of device. 
     Where an embodiment is described as implemented in an application, the delivery of the application in a Software as a Service (SaaS) model is contemplated within the scope of the illustrative embodiments. In a SaaS model, the capability of the application implementing an embodiment is provided to a user by executing the application in a cloud infrastructure. The user can access the application using a variety of client devices through a thin client interface such as a web browser (e.g., web-based e-mail), or other light-weight client-applications. The user does not manage or control the underlying cloud infrastructure including the network, servers, operating systems, or the storage of the cloud infrastructure. In some cases, the user may not even manage or control the capabilities of the SaaS application. In some other cases, the SaaS implementation of the application may permit a possible exception of limited user-specific application configuration settings. 
     The present invention may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. 
     The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
     Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. 
     Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. 
     Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. 
     These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.