Abstract:
The invention relates to a method for data transmission with a local network, the local network comprising a plurality of local network entities for connecting mobile entities to the local network and at least one local network entity for connecting the local network to a data network. The method comprises receiving, by a first local network entity of the local network entities of the local network, a data packet, the network address of the first mobile entity on the basis of the data packet, determining, by the first local network entity on the basis of the network address of the first mobile entity, the second local network entity, via which the first mobile entity is connected to the local network, and forwarding, by the first local network entity, the data comprised by the data packet to the first mobile entity via the second local network entity.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of International Application No. PCT/CN2011/077770, filed on Jul. 29, 2011, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to the field of communication networks and in particular to mobile communication networks. 
       BACKGROUND 
       [0003]    In current communication networks it is possible to connect to a packet data network, for example the Internet, by means of a mobile terminal. To this end, a mobile communication provider usually deploys several network entities like gateways that establish a connection to the packet data network for the mobile terminal. 
         [0004]    The mobile terminal is connected to a local network by means of, for example, an access point and has a network address allocated by a respective entity in the packet data network. Furthermore, a mobile anchor point is allocated for the mobile terminal, for example a Gateway GPRS Support Node (GGSN) or a packet data network gateway, which is usually on the data path for all data traffic from and to the mobile terminal. Hence, all data packets of a data connection or to the mobile terminal are routed through the mobile anchor point. 
         [0005]    However, data traffic is routed through the mobile anchor point even if mobile terminals are connected to the same local network and data are to be transmitted between two mobile terminals of this same local network. The local network is a subset of the packet data network and it provides more local connectivity from topological point of view. Voice-over-IP (VoIP) traffic between two mobile terminals may have a more local nature, for example being traffic between users of the same local network, e.g. within a corporate network. However, if such traffic is routed via the mobile anchor point as in conventional solutions, bandwidth resources or other resources are wasted because the data path between the mobile terminals that are in the same local network has to traverse the mobile anchor point(s) of the packet data network. 
       SUMMARY 
       [0006]    It is the object of the present invention to provide a concept for resource efficient data transmission between mobile terminals connected to a local network. 
         [0007]    This object is achieved by the features of the independent claims. Further embodiments are apparent from the dependent claims. 
         [0008]    The invention is based on the finding that data traffic, in particular data packets, can be differentiated, whether they have a final destination in the local network, although the default routing would be to an entity in a data network, which is outside the local network. If the differentiation process finds a local address, in particular an address within the local network, a more direct route to the final destination can be determined, such that the differentiated data packet can be sent to the final destination in the local network in a more efficient way. In particular, routing from the local network over the routing entity of the data network can be omitted, thus saving bandwidth between the local network and the routing entity. 
         [0009]    According to a first aspect, the invention relates to a method for data transmission within a local network. The local network comprises a plurality of local network entities, e.g. routers, for connecting mobile entities to the local network and at least one local network entity for connecting the local network to a data network. The data network comprises at least a routing entity. A first mobile entity is connected to the local network via a first local network entity, e.g. a local access router, of the plurality of local network entities and has a first network address allocated. A second mobile entity is connected to the local network via the same or a second local network entity of the plurality of local network entities and has a second network address allocated. The method comprises receiving, by a first local network entity of the local network entities of the local network, a data packet from the first mobile entity being addressed to the second mobile entity, in particular to the network address of the second mobile entity. The default routing of all data packets originated by the mobile entities is via the local network entity for connecting the local network to a data network because the default data path traverses the mobile anchor point. This is gained, e.g. by encapsulating the data packets originated by the mobile entities in other data packet with the destination address of the mobile anchor point. The first local network entity determines, whether the data packets originated by the first mobile node have a destination network address that is allocated to an entity within the local network. If, for example, data packets originated by the first mobile node address the second mobile node the first local network entity forwards that data packets to the second local network entity. And the second local network entity forwards the data packets to the second mobile node. The approach is the same when one or both of the mobile nodes are fixed nodes, e.g. for communication between a mobile node and a server with both in the same local network. 
         [0010]    A network address is particularly allocated unambiguously to the first mobile entity and to the second mobile entity according to some implementation forms. The network address can for example be allocated by an entity of the data network that is external to the local network. The data network may be a packet data network, for example the Internet, or a core network of a mobile communications system. 
         [0011]    The data packet received by a first local network entity may originate from within the local network, for example from another mobile entity which is connected to the local network via the first local network entity or a second local network entity of the plurality of local network entities. However, the data packet may also originate from outside the local network, wherein the first local network entity can for example be a gateway to a further local network. Accordingly, instead of forwarding the data packet to the routing entity as in conventional solutions, the routing of the data packet is performed within or between the local network entities, if the second local network entity and/or a gateway to a further local network can be determined by the first local network entity. The local network entity can for example be a local network router. 
         [0012]    According to a first implementation form of the first aspect, the invention relates to the method for data transmission, wherein mapping information between the first local network entity and the first mobile entity is stored, and determining the first local network entity comprises using the stored mapping information. If the mapping between the first mobile entity and the first local network entity is once determined by a second local network entity on the basis of the network address of the first mobile entity, the second local network entity can for example cache this mapping information and use it when receiving a further data packet destined for the first mobile entity. According to some implementation forms, the mapping information between a first mobile entity and a first local network entity is stored in a specific network entity within the local network and may be retrieved by a respective request from a second local network entity for receiving the mapping information. 
         [0013]    According to a second implementation form of the first aspect, the invention relates to the method for data transmission, wherein determining the first local network entity comprises sending a request from a second local network entity to the plurality of local network entities, in particular a broadcast request, for receiving the mapping information between the first local network entity and the first mobile entity, the request comprising the network address of the first mobile entity. Hence, the second local network entity resolves the mapping between the first local network entity and the first mobile entity by sending the request to one or more or all local network entities of the local network. The request can for example be sent according to an Address Resolution Protocol (ARP), e.g., according to RFC 826 “An Ethernet Address Resolution Protocol”, in particular as an ARP request. The entity of the local network having the requested mapping information, typically the first local network entity, responds with the mapping information, for example by an ARP response. 
         [0014]    According to some implementation forms, the first local network entity sends the requested mapping information in response to the request of the second local network entity. In general, at least one or each local network entity of the plurality of local network entities may respond to a respective request for mapping information, if the request comprises the network address of the mobile entity that the respective local network entity connects to the local network. 
         [0015]    According to some further implementation forms, the local network comprises a network entity, e.g. a local resolution server, for storing mapping information between the network address of each mobile entity connected to the local network and the corresponding local network entity via which the mobile entity is connected to the local network. The local resolution server sends the stored mapping information between the first local network entity and the first mobile entity in response to the request of the second local network entity. If a connection of a first mobile entity to the data network is established by means of one of the plurality of local network entities, the respective mapping information is sent from the connecting first local network entity to the local resolution server when the first mobile entity associates with the first local network entity, such that the mapping information is registered with the local resolution server. 
         [0016]    According to a third implementation form of the first aspect, the invention relates to the method for data transmission wherein the first local network entity sends a further data packet(s) originated by the first mobile node to the local network, in particular before receiving a data packet from the second local network entity originated by the second mobile node and addressed to the first mobile node. The second local network node determines and remembers the mapping between the first mobile node and the first local network entity from further data packet(s) belonging to other short-cuts, e.g. between the first mobile node and a third mobile node that is also associated with the second local network entity. The further data packet can for example also be regular data traffic within the local network, in particular originating from the first mobile entity and forwarded via the second local network entity to a third local network entity. The further data packet(s) may be sent any time before the reception of a data packet from the second mobile node addressed to the first mobile node by the second local network entity, such that the mapping information may be known to the second local network entity at the time of the reception of the data packet addressed to the first mobile node. The mapping information determined from the further data packet(s) can for example be stored in the second local network entity. 
         [0017]    According to some implementation forms, the further data packet is included in a broadcast message to the local network entities of the local network. The broadcast message may be sent as an update message for announcing the mapping information. The first mobile entity may undergo a hand-over from another local network entity to the second local network entity, such that a former mapping information for the first mobile entity becomes invalid and the new, valid mapping information is sent as an update message in the form of a broadcast message to the local network entities. 
         [0018]    According to some implementation forms, the further data packet is included in a unicast message to the first local network entity. Data traffic from the first mobile entity may be directed to the first local network entity and sent via the second local network entity, such that the mapping information between the first mobile entity and the second local network entity is included in the unicast message. The final destination address of the unicast message is not limited to the first local network entity itself, but can also include further destinations reached via the first local network entity, for example a mobile entity connected to the local network via the first local network entity. 
         [0019]    According to a fourth implementation form of the first aspect, the invention relates to the method for data transmission, wherein forwarding comprises sending the data comprised by the data packet from the first local network entity to the second local network entity and from the second local network entity to the first mobile entity. In particular, the data path for the data comprised by the data packet comprises a direct connection from the first local network entity to the second local network entity and a direct connection from the second local network entity to the first mobile entity. And here we have the model where first mobile connects to second node. 
         [0020]    According to a fifth implementation form of the first aspect, the invention relates to the method for data transmission, wherein the routing entity is further comprised by the local network, in particular by one of the local network entities of the local network. The routing entity may be a gateway and may be a part of both the local network and the data network. 
         [0021]    According to a sixth implementation form of the first aspect, the invention relates to the method for data transmission, wherein the data packet is forwarded to the first local network entity by the second local network entity. 
         [0022]    The mapping information according to the implementation forms described above may comprise the network address of the first mobile entity and an address of the second local network entity. The network address of the first mobile entity may be an IP address. The address of the second local network entity may be an IP address of the second local network entity or a media access control (MAC0 address of the second local network entity or, in general, the local network entity which connects the mobile entity to the local network. Hence a data packet forwarded from the first local network entity to the first mobile entity via the one local network entity may include the IP address of the first mobile entity and the MAC address of the one local network entity. 
         [0023]    According to a second aspect, the invention relates to a local network entity for a local network. The local network comprises a plurality of local network entities for connecting mobile entities to the local network and at least one local network entity for connecting the local network to a data network. The data network comprises a routing entity having a router network address allocated. A first local network entity is configured to receive a data packet being addressed to the router network address and comprising data addressed to a first mobile entity, which is connected to the local network via a second local network entity of the plurality of further local network entities and has a network address allocated. The first local network entity is further configured to retrieve the network address of the first mobile entity on the basis of the data packet. On the basis of the network address of the first mobile entity, the first local network entity determines the second local network entity, via which the first mobile entity is connected to the local network, and forwards the data comprised by the data packet to the first mobile entity via the second local network entity. 
         [0024]    Accordingly, the local network entity according to some implementation forms makes it possible to forward data or data packets, respectively, directly to the corresponding local network entity that connects the first mobile entity to the network without using the routing entity of the data network. 
         [0025]    According to a first implementation form of the second aspect, the invention relates to a local network entity, wherein the local network entity is configured to store mapping information between the second local network entity and the first mobile entity, and to determine the second local network entity using the stored mapping information. 
         [0026]    According to a second implementation form of the second aspect, the invention relates to a local network entity which is configured to connect at least one mobile entity to the local network and to send a mapping information between the local network entity and the at least one mobile entity connected to the local network via the local network entity in response to a request for the mapping information, the request being received from the local network. Hence, the local network entity can also serve as a connecting point for mobile entities to the local network and to provide respective mapping information between itself and the respective connected mobile entity to other local network entities requesting such mapping information. 
         [0027]    A local network can for example comprise a plurality of local network entities according to the second aspect of the invention. 
         [0028]    Further implementation forms of the second aspect of the invention become apparent from the various implementation forms described in conjunction with the first aspect of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Further embodiments of the invention will be described with reference to the following figures, in which: 
           [0030]      FIG. 1  shows a communication network according to an implementation form; 
           [0031]      FIG. 2  shows a flowchart of a method according to an implementation form; 
           [0032]      FIG. 3  shows a communication network according to an implementation form; 
           [0033]      FIG. 4  shows a flowchart of a method according to an implementation form; 
           [0034]      FIG. 5  shows a communication network according to an implementation form; 
           [0035]      FIG. 6  shows a flowchart of a method according to an implementation form; and 
           [0036]      FIG. 7  shows a flowchart of a method according to an implementation form. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]      FIG. 1  shows a communication network according to an implementation form. The communication network comprises a local network  110  and a core network  120 . The core network  120  may be a network provided by a mobile communications provider and for example comprises a serving gateway (SGW)  122 , a packet data network gateway (PGW)  124 , and a mobility management entity (MME)  126 . 
         [0038]    The local network  110  comprises a local transport network (LTN)  130 , to which several local network entities  141 ,  142 ,  143 ,  144 ,  145  are connected for communicating with each other. The local network entities  141 ,  142 ,  143  serve as connection points for mobile entities  151 ,  152 ,  153 , which may be mobile terminals such as user equipments (UE). The local network entities  141 ,  142 ,  143  may be local access points (LAP), E-node B, home eNodeB, WiFi access point or similar entities which perform a routing function for the mobile entities in the local network. The local network entity  144  may be an interworking gateway (IGW), which is connected to the Internet  160 . The local network entity  145  serves as a gateway to the core network  120  and is connected to the serving gateway  122 . 
         [0039]    Accordingly, all traffic originating from or targeting at the mobile entities  151 ,  152 ,  153  respectively, are routed over their respective connecting points, namely the local network entities  141 ,  142 ,  143 , respectively. Further entities can be connected to the local transport network  130 , but are not shown here for the reasons of a better overview. 
         [0040]    Although only one mobile entity is connected to each of the local network entities  141 ,  142 ,  143 , more than one mobile entity can be connected to each of the local network entities  141 ,  142 ,  143 . Furthermore, the local network entities  141 ,  142 ,  143  may be provided by the same or by different physical entities. 
         [0041]    The local transport network  130  may be a physical network like an Ethernet network or a logical network like an IP network or a virtual private network (VPN). 
         [0042]    In the following, a short overview over various embodiments of communication scenarios is given, which will be explained in more detail with respect to  FIG. 2  to  FIG. 6 . One of the local network entities  141 ,  142 ,  143 ,  144 ,  145  receives a data packet, which is finally targeted at one of the mobile entities  151 ,  152 ,  153 , for example the mobile entity  151 . However, the data packet is addressed to a routing entity of the core network  120 , for example the serving gateway  122 . Within the data packet, an address, in particular an IP address of the mobile entity  151 , is included or encapsulated. The local router, which received the data packet, for example local network entity  142 , retrieves the IP address of the mobile entity  151  and resolves the local router, via which the mobile entity  151  is connected to the local network  110 , namely the local network entity  141 , wherein the resolution is based on the network address of the mobile entity  151 . The resolution can be made by sending a broadcast request within the local transport network  130 , or by using mapping information from a message received earlier from the local network entity  141 , or by querying a local resolution server in the local network  110 . The data packet can then be forwarded from the local network entity  142  as an originating local network entity to the local network entity  141  as a destination local router, based on the results of the resolution, namely the address of the local network entity  141 . The mapping information between the local network entity  141  and the mobile entity  151  can be stored in the local network entity  142  in order to forward subsequent packets based on the stored mapping information. 
         [0043]      FIG. 2  shows a flowchart of a method according to an implementation form. In this embodiment, mobile entities  151  and  152 , local network entities  141  and  142  and a packet data network gateway or local gateway (PGW/LGW)  200  are part of the communication environment. In a step  210 , a packet data network (PDN) connection is established for the first mobile entity  151  via the first local network entity  141  over PGW/LGW  200 . During the establishment a network address, for example an IP address, is allocated to the first mobile entity  151  by the PGW/LGW  200 . In step  212 , the IP address of the first mobile entity  151  is stored in the local network entity  141 . Similar to steps  210  and  212 , in steps  214  and  216 , a PDN connection is established for the second mobile entity  152  via the second local network entity  142  with the PGW/LGW  200 , and an IP address allocated to the second mobile entity  152  is stored in the second local network entity  142 . The local network entities  141 ,  142  are local routers according to an implementation form. 
         [0044]    In step  218 , an IP packet is sent from the first mobile entity  151  to its corresponding local network entity  141 . The IP packet has a destination IP of the PGW/LGW  200 , for example a router network address. However, the IP packet is finally targeted at the second mobile entity  152  such that the IP address of the second mobile entity  152  is comprised by the IP packet. This IP address of the second mobile entity  152  is retrieved from the IP packet by the first local network entity  141  in step  220 . In step  222 , a mapping between the second mobile entity  152  and the corresponding local network entity  142  is resolved based on the IP address of the second mobile entity  152  retrieved before. Accordingly, the first local network entity  141  knows that packets for the second mobile entity  152  are to be routed via the second local network entity  142 . Hence, in step  224 , the IP packet is sent from the first local network entity  141  to the second local network entity  142  and, in step  226 , from the second local network entity  142  to the second mobile entity  152 . 
         [0045]    The mapping between the second mobile entity  152  and the second local network entity  142  is stored by the first local network entity  141  in step  228 . Hence, following, subsequent packets targeted at the second mobile entity  152  and originating from the first mobile entity  151  can be routed from the first mobile entity  151  to the first local network entity  141  in step  230 , from the first local network entity  141  to the second local network entity  142  in step  232 , and finally from the second local network entity  142  to the second mobile entity  152  in step  234 . 
         [0046]      FIG. 3  shows a further embodiment of a communication network, which is based on the communication network shown in  FIG. 1 . In this embodiment, the local transport network  130 , for example, is an Ethernet-based network. The local network entity  144  is a local gateway to the Internet  160 . The local network entity  145  is an access gateway (AGW) to the core network  120 . 
         [0047]      FIG. 4  shows a flowchart of a method according to a further implementation form. Similar to steps  210 ,  212 ,  214  and  216 , in steps  410 ,  412 ,  414 ,  416 , a PDN connection with the core network  120  is established for the first mobile entity  151  via the first local network entity  141  and for the second mobile entity  152  via the second local network entity  142 . Respective IP addresses of the mobile entities  151 ,  152  are stored in the local network entities  141 ,  142 . 
         [0048]    In step  418 , the first mobile entity  151  sends an IP packet to the local network entity  141 , which is addressed to the IP address of the serving gateway  122 , but includes, encapsulated, the final IP address of the second mobile entity  152 , which is retrieved by the first local network entity  141 . Accordingly, in steps  420  and  422 , the first local network entity  141  sends ARP requests to the second local network entity  142  and the third local network entity  143 , each of the ARP requests comprising the IP address of the second mobile entity  152 . As the third local network entity  143  is not connected with the second mobile entity  152 , no response is sent from the third local network entity  143 . However, in step  424 , the second local network entity  142  sends an ARP response to the first local network entity  141  including the MAC address of the second local network entity  142 . 
         [0049]    From the communication so far, the second local network entity  142  knows that the first mobile entity  151  is connected to the local network via the first local network entity  141  and stores this mapping information in step  426 . Based on the ARP response, in step  428 , the first local network entity  141  stores the mapping information between the second mobile entity  152  and the second local network entity  142 . In particular, the mapping information stored in steps  426  and  428  comprises the IP address of the respective mobile entity and the MAC address of the corresponding local router. Based on the mapping information retrieved, in step  430 , the first local network entity  141  sends the IP packet targeted at the second mobile entity  152  to the second local network entity  142 , which forwards this packet to its final destination, namely the second mobile entity  152 , in step  432 . A response packet from the second mobile entity  152  to the first mobile entity  151  is sent to the second local network entity  142  in step  434  from the second local network entity  142  to the first local network entity  141  in step  436  and from the first local network entity  141  to the first mobile entity  151  in step  438 , based on the previously stored mapping information. 
         [0050]    Subsequent IP traffic between the first and the second mobile entity  151 ,  152  is transmitted via the local network entities  141 ,  142  in steps  440 ,  442 ,  444 , also based on the previously stored mapping information. 
         [0051]    In step  450 , a handover for the first mobile entity  151  from the first local network entity  141  to the third local network entity  143  is initiated. To this end, in step  452 , the IP address of the first mobile entity  151  is removed from the first local network entity  141  and the same, unchanged IP address of the first mobile entity  151  is stored in the third local network entity  143 . 
         [0052]    In steps  456  and  458 , the third local network entity  143  announces the new mapping information to the remaining local network entities  141 ,  142  by respective FreeARP requests. In response to this updated information, the second local network entity  142  updates its mapping information between the IP address of the first mobile entity  151  and the MAC address of the third local network entity  143  in step  460 . 
         [0053]    In step  462 , the second mobile entity  152  sends an IP packet to its corresponding local network entity  142 , the IP packet having a final destination being the first mobile entity  151 . As the second local network entity  142  has the corresponding mapping information for the first mobile entity  151  stored, the IP packet can immediately be forwarded to the corresponding local network entity  143  in step  464 . As the IP packet originates from the second mobile entity  152  and is routed via the second local network entity  142 , the third local network entity  143  retrieves the corresponding mapping information between the IP address of the second mobile entity  152  and the MAC address of the second local network entity  142 . This mapping information is stored in step  466  in the local network entity  143 . The IP packet is finally forwarded to the first mobile entity  151  from the third local network entity  143  in step  468 . In step  470 , a return IP packet is sent from the first mobile entity  151  targeted at the second mobile entity  152  to the corresponding local network entity  143 , forwarded to the local network entity  142  in step  472  and finally forwarded to the second mobile entity  152  in step  474 , based on the previously stored mapping information. In a similar way, subsequent IP traffic is routed between the first and the second mobile entity  151 ,  152  via the respective local network entities  152 ,  153  in steps  476 ,  478  and  480 . 
         [0054]      FIG. 5  shows a further implementation form of a communication network. The communication network of  FIG. 5  is based on the communication network of  FIG. 1 , but further includes a local resolution server (LRS0  500  which is connected to the local transport network  130  and the local network  110 , respectively. The local resolution server is adapted to store mapping information between each mobile entity connected to the local network  110 , and the corresponding local network entity via which the mobile entity is connected to the local network. The local resolution server  500  can send stored mapping information in response to respective requests, for example including the IP address of the mobile entity, for which the mapping information is requested. 
         [0055]      FIG. 6  shows a flowchart of a method according to a further implementation form. In step  610 , a PDN connection is established for the first mobile entity  151  via the first local network entity  141  with the core network  120 , wherein an IP address for the first mobile entity  151  is allocated by the core network  120 , for example by the serving gateway  122 . The IP address of the first mobile entity  151  and the address of the corresponding local network entity  141  are sent to the local resolution server  500  in step  612 . In a similar fashion, in step  614 , a PDN connection is established for the second mobile entity  152  via the second local network entity  142  with the core network  120 . In step  616 , the IP address allocated for the second mobile entity  152  and the address of the corresponding local network entity  142  are also sent to the local resolution server  500 . In step  618 , the mapping information provided for the first and the second local network entity  141 ,  142  is stored in the local resolution server  500 . 
         [0056]    In step  620 , the first mobile entity  151  sends an IP packet having a destination IP of the serving gateway  122  to the corresponding local network entity  141 , wherein the target IP address of the second mobile entity  152  is encapsulated in this IP packet and retrieved by the first local network entity  141 . Hence, in step  622 , the local network entity  141  sends a resolution request containing the IP address of the second mobile entity  152  to the local resolution server  500 , which provides a respective response with the requested mapping information to the first local network entity  141  in step  624 . In step  626 , the mapping information received from the local resolution server  500  is stored in the local network entity  141 . Similar to the previous embodiments, the IP packet is forwarded to the local network entity  142  in step  628 , and from there to the final destination, the second mobile entity  152  in step  630 . 
         [0057]    In step  632 , a response packet targeted at the first mobile entity  151  is sent from the second mobile entity  152  to its corresponding local network entity  142 , which sends a respective resolution request containing the IP address of the first mobile entity  151  to the local resolution server  500  in step  634 . A corresponding response to the second local network entity  142  containing the address of the local network entity  141  is provided by the local resolution server  500  in step  636 . 
         [0058]    The IP packet originating from the second mobile entity  152  is then forwarded to the first local network entity  141  in step  638  and from there to the first mobile entity  151  in step  640 . The mapping information between the first mobile entity  151  and the first local network entity  141 , which is received from the local resolution server  500 , can be stored in the second local network entity  142 . 
         [0059]    Based on the stored mapping information, IP traffic can be routed between the first and the second mobile entity  151 ,  152  via the corresponding local network entities  141 ,  142  in steps  642 ,  644 ,  646 . 
         [0060]      FIG. 7  shows a flowchart of a further implementation form of a method. Steps  710 ,  712 ,  714 ,  176  correspond to the steps  210 ,  212 ,  124 ,  216  of the method of  FIG. 2  respectively. 
         [0061]    In step  718 , an IP packet is received from the core network  120  by the AGW  145 , having a final destination IP encapsulated, namely the IP address of the second mobile entity  152 . In steps  720  and  722 , the AGW  145 , which is a local network entity of the local network, sends an ARP request to the remaining local network entities  141 ,  142  including the IP address of the second mobile entity  152 . In step  724 , the second local network entity  142 , which connects the second mobile entity  152  to the local network, sends an ARP response to the AGW  145 , including the MAC address of the second local network entity  142 . This mapping information between the IP address of the second mobile entity  152  and MAC address of the second local network entity  142  is stored in the AGW  145  in step  726 . Based on this mapping information, in step  728 , the AGW  145  forwards the IP packet to the local network entity  142 , which then further forwards the IP packet to the final destination, the second mobile entity  152  in step  730 . 
         [0062]    The second mobile entity  152  sends a response packet to its corresponding local network entity  142  including a final destination IP of the former originating address IP-X, which may be located in the core network or outside the core network  120 , but in this embodiment not within the local network  110 . The local network entity  142  sends respective ARP requests in steps  734  and  736  including the IP address IP-X to the other local network entities  141 ,  145 , but, in step  738 , gets no ARP reply, because no mobile entity with IP-X is present in the local network  110 . In consequence, the local network entity  142  sends the IP packet to the remote server via the AGW  145  in steps  740  and  742 . The remote server may be the routing entity within the core network  120 . 
         [0063]    Following IP traffic is routed between the mobile entity  152  and the core network  120  via the local network entity  142  and the AGW  145  in steps  744 ,  746  and  748 . 
         [0064]    The embodiments described above can be combined and, in particular, respective resolution of the mapping information can be interchanged between the embodiments. The kind of LTN described or used in the embodiments should not be understood limiting but include any kind of logical or physical transport network.