KR100363943B1 - Hand off algorithm for mobile hosts in the IP/multicast network - Google Patents

Abstract

The present invention relates to a handoff control method for supporting a mobile terminal in an Internet multicast environment.

The present invention is based on a method of re-subscribing to a multicast group so that a router of a corresponding network maintains location information of a mobile terminal whenever the terminal moves to another network. In this case, mobility of a mobile terminal, characteristics of a moving network, and multi Since the multicast service may be frequently disconnected according to the characteristics of the cast routing method, the loss of multicast data due to the temporary disconnection (called a hand off) is minimized. Whenever you move to a new network and check the network characteristics and environment, if the multicast service disconnection is expected, do not rejoin the multicast group, and register your location with the network router assigned the first Internet address. To reduce A room, and it expected to contribute to this by providing a better quality of the multicast service according to support the mobile terminal from the Internet multicast environment.

Description

Handoff algorithm for supporting mobile terminal in internet multicast environment {Hand off algorithm for mobile hosts in the IP / multicast network}

The present invention relates to a technique for minimizing data loss due to handoff that occurs when a mobile terminal moves to an external network in an internet multicast environment based on a TCP / IP multicast network. When the network characteristics and environment are checked every time they move to the network, and the multicast service is expected to be disconnected, the network side that is assigned the first Internet address without rejoining the multicast group to maintain the location information of the mobile terminal The present invention relates to a handoff control method for supporting a mobile terminal in an internet multicast environment that can reduce the possibility of disconnection of a multicast service by selectively using a method of registering its own location in a router.

In the conventional handoff control method for supporting a mobile terminal, a mobile support router of a network (home network) to which the mobile terminal is initially assigned an address is called a home agent (HA), and supports mobility of a newly moved network (external network). A router is referred to as a foreign agent (FA), and a mobile terminal (MH) transmits and receives all data packets through HA by establishing a bidirectional tunnel between them. This scheme applies the mobility support scheme in unicast environment to multicast environment. It can handle both the transceiver's mobility, guarantee the continuity of packet to some extent, and support mobile multicast support with minimal modification. Although possible, it has tunneling problems, packet redundancy problems, scalability problems, and routing inefficiencies. The tunnel centralization problem refers to a phenomenon in which mobile terminals distributed in different networks in the same group are concentrated in one FA as the end points of the tunnel are concentrated in one FA, which may cause packet duplication problems in the FA side. In addition, when the FA of the newly moved network is already joined to the multicast group, a case may occur in which data transfer by the tunnel from the HA and transfer by the FA from the upper router of the multicast tree overlap. The routing inefficiency problem is caused by the triangle when the FA side of the newly moved network has a shorter routing path from the sender than the HA. It is similar to the unicast environment. As the number of mobile terminals belonging to the same multicast group in the HA increases, scalability is greatly reduced by performing unicast transmissions as many as the number of mobile terminals through a tunnel despite being multicast data.

As another conventional technology, there is a method of transmitting and receiving data by resubscribing to a multicast router of a moved subnetwork whenever a mobile terminal moves to an external network. While this method is simple and efficient in routing, it does not work when the mobile terminal stays in each external network for shorter time than joining a new multicast routing tree. If it does not support new subscription to the multicast routing tree, the multicast service may be disconnected until the terminal moves to another network. In addition, if the moved network is not subscribed to the multicast group, a new subscription is required, which creates a burden of regenerating the multicast tree according to the multicast routing protocol.

Accordingly, an object of the present invention is to check the mobility or mobile network characteristics and environment of the terminal to minimize the frequent data loss and service disconnection that may occur whenever the mobile terminal moves to a new network router of the newly moved network The path of the multicast data can be selectively or temporarily used in combination with a method of re-subscribing to a multicast group to maintain the location information of the mobile terminal and registering its location with a network router assigned an initial Internet address. An object of the present invention is to provide a handoff control method for supporting a mobile terminal in an Internet multicast environment that can efficiently handle configuration, improve scalability, and enhance service robustness.

According to an aspect of the present invention, a mobile terminal transmits a subscription request message specifying an option from a user to a mobility support router of an external network, and from the mobile terminal. And receiving and receiving a subscription request message including options based on characteristics of the mobile network to determine and determine a router to manage location information of the mobile terminal using the currently maintained multicast group information. If the mobile station wants to receive the multicast service through the router of the network to which the mobile station is initially assigned due to the fact that it does not support the multicast function or the user requests, the mobile station moves to the network to which the first address is assigned. Register your location information on the support router And receiving a response therefrom, and if the mobile support router of the moved external network is already subscribed to the multicast group, informing the mobile terminal that the handoff procedure is completed by sending a subscription response message immediately; If the mobility support router of the moved external network is not subscribed to the multicast group, the response delay time may be longer after sending the JOIN / GRAFT message to join the routing tree depending on the multicast routing method being used. In order to minimize the multicast loss due to handoff as possible, by temporarily performing the above process of requesting registration to the router of the network to which the first address is allocated, and for the JOIN / GRAFT from the upper router supporting the multicast. Receive a response message and sign up By notifying the mobile station, the multicast data is then directly transmitted and received with the upper router of the multicast routing tree, receiving a registration request message from the mobile support router of the external network, and storing the location information of the mobile station. After the response by the registration response message to receive a subsequent registration cancellation message characterized in that it comprises the step of performing the relay function of the multicast data until the location information of the mobile terminal is deleted.

The present invention also provides a method for a mobile terminal to transmit a subscription request message specifying options according to mobility characteristics and characteristics of a mobile network from a user to a mobility support router of a corresponding external network, characteristics of mobility from a mobile terminal, and characteristics of a mobile network. Receiving a subscription request message including an option according to the above, and determining and determining a router to manage location information of the mobile station using the currently maintained multicast group information. If the mobile station wants to receive multicast service through the router of the network to which the mobile station is initially assigned due to a lack of support or a request from a user, the mobile station should contact the mobile support router side of the network to which the mobile station is initially assigned an address. Register location information from and reply from In step S, if the mobile support router of the moved external network is already subscribed to the multicast group, the mobile terminal sends a subscription response message to inform the mobile terminal of the handoff procedure. If the mobility support router is not subscribed to the multicast group, it may send a JOIN / GRAFT message to join the routing tree depending on the multicast routing scheme in use. Temporarily minimizing the loss of multicast due to handoff by temporarily registering the registration request with a router of the allocated network; receiving a response message for JOIN / GRAFT from an upper router supporting multicast Notify the mobile terminal that registration is complete From now on, the multicast data is directly transmitted and received with the upper router of the multicast routing tree, receives the registration request message from the mobile support router of the external network, stores the location information of the mobile terminal, and responds with the registration response message. Then, after receiving the registration cancellation message, the computer-readable recording medium recording a program for performing the step of performing the function of relaying the multicast data until the position information of the mobile terminal is deleted.

1 is a block diagram illustrating the relationship between network components for supporting a mobile terminal in an Internet multicast environment according to the present invention.

Figure 2 is a block diagram showing the structure of a mobile support router according to FIG.

3 is a flowchart illustrating an operation process at a mobile terminal (MH) side according to the present invention;

4 and 5 are flowcharts illustrating an operation process at a mobility support router (MSR) side according to the present invention;

<Description of Signs of Major Parts of Drawings>

10: mobile terminal 20: wireless communication controller (Aceess Point)

30: mobility support router 40: router with multicasting function

Below. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing the relationship between network components for carrying out the method of the present invention, including one or more local area networks (LANs). As shown in FIG. 1, reference numeral 10 denotes a mobile terminal connected to a wireless network through an AP 20, and reference numeral 20 is connected to fixed wired network nodes in a predetermined area called a cell. A wireless communication controller provides a wireless communication function to a mobile terminal, and reference numeral 30 stores and maintains location information of the mobile terminal through the AP 20, and enables communication between hosts including the mobile terminal 10. It is assumed that each LAN includes at least one mobile support router 30 for the mobile terminal, and may be integrated into one system with the AP 20 or exist separately from the AP 20 as shown in FIG. have. In addition, reference numeral 30 may support a multicast function or may not be a router. Reference numeral 40 denotes a router that follows a specific multicast routing scheme invented to support a multicast function in an existing wired network (Internet). The multicast routing method is a routing method for efficiently delivering multicast data to a plurality of hosts joined to an arbitrary multicast group. Representatively, the distance vector multicast routing protocol (DVMRP) and the multicast routing extensions (MOSPF). for OSPF), Protocol Independent Multicast (PIM), and Core Based Trees Multicast Routing (CBT). The mobile terminal 10 is capable of multicast communication with remote hosts of a wired network through the multicast support router 40. FIG. 2 is a block diagram illustrating the structure of the mobile support router 30 according to FIG. The mobile support router 30 is composed of a main processing module S10, a registration processing module S20, and a multicast routing processing module S30. The main processing module S10 is a main module for processing a handoff generated whenever a mobile terminal 10 belonging to an external or sub network moves, and joins via the AP 20 from the mobile terminal 10. When the request message is received, the registration processing module S20 and the subscription processing module S30 are called with reference to the user request and the multicast group information storage device S12 on the mobile terminal 10 side, respectively. When the registration processing module S20 is requested by the main processing module S10, the information of the mobile terminal 10 is stored in the visitor list S21, and the mobile terminal 10 of the network to which the mobile terminal 10 is initially assigned a network address. When the mobile support router 30 transmits a registration request message and receives a response therefrom, it notifies the main processing module S10 of the result thereof again. In addition, when the multicast routing processing module S30 is requested by the main processing module S10, the nearest multicast supporting router 40 is found and a procedure for subscribing to the routing tree depends on the currently used multicast routing scheme. And the result thereof is notified back to the main processing module (S10). At this time, if the joining procedure of the routing tree is successfully performed, then the multicast data is transferred from the upper multicast support router 40 to the mobile terminal 10 via the mobile support router 30 directly. The main processing module S10 takes additional necessary measures by combining the results returned from the respective modules S20 and S30 and then informs the mobile terminal 10 of the final result. On the other hand, when the mobile terminal receives the registration request message from the main processing module S10 of the mobile support router 30 to which the mobile station is initially assigned an address, the mobile terminal records the information in the mobile terminal location information storage device S11 and registers a response. Respond via a message. At this time, the stored location information is maintained until the registration cancellation message is received. Thereafter, the multicast data received by the mobile support router 30 is not only multicasted to the hosts in the subnetwork, but also transmitted to the mobile support routers of the network recorded in the location information storage of the mobile terminal. 1 is a flowchart illustrating the operation of the mobile terminal 10 side according to FIG. 1. When the mobile terminal 10 moves to an external network, the mobile terminal 10 first locates a mobile support router in the external network and transmits a subscription request message. (S103). In this case, when the user designates the permanent tunnel registration option, the TFLAG field in the subscription request message is designated as 1 (S102). Thereafter, when the T1 timer is operated (S104), and the subscription response message is received from the MSR 30 before the operated timer expires (S105), the T1 timer is stopped (S108) and the execution procedure is terminated. Thereafter, the terminal can transmit and receive multicast data in the newly moved network. On the other hand, if there is no response from the mobile support router 30 (MSR) until the timer expires, the subscription request is considered to have failed and ends (S107). FIG. 4 is a mobile terminal moved from an external network according to FIG. The operation procedure of the mobile support router 30 (MSRF) when receiving the subscription request message from (10) will be described by a flowchart. In this case, operations of S311-S316 are performed by the main processing module S10 of FIG. 2, and S321-S329 is the registration request processing module S20 of FIG. 2, and operations of S331-S41 are multicast routing subscription processing modules ( When the mobile support router 30 receives the subscription request message from the mobile terminal 10 belonging to the external network, it checks whether the TFLAG value included in the message is set (S311). If TFLAG is set to 1, only the registration request processing module S20 is performed. Even if the TFLAG is not set to 1, even if the mobile support router 30 does not support the multicast function, only the registration request processing module S20 is performed. The registration request processing module S20 transmits a registration request message (S321), updates the visitor list (S323) (S322), and receives a response message therefrom (S324), indicating that the registration process is completed. Notifies the mobile terminal 10 through the (S325). In addition, the T1 timer is stopped (S326), and the state is shifted to the OPEN_TUN state (S327). On the other hand, if the TFLAG is not specified as 1 and the router supports the multicast function, the message received from the mobile terminal is multiplied. The multicast group member is checked in the subnetwork with reference to the cast group information storage device S315 (S313). At this time, if the group member already exists in the sub-network, it notifies that the handoff procedure is completed by sending a subscription response message to the mobile terminal (S314). If the group member does not exist, the multicast routing subscription processing module S30 and the registration processing module S20 are temporarily performed in parallel, and the state is transmitted to the mobile terminal 10 side according to the execution result from each processing module. The multicast routing subscription processing module S30 stores information of the multicast group (S331), transmits a message for joining an adjacent multicast router (S332), and operates a timer (S333). After receiving the JOIN_ACK or GRAFT_ACK response message from the upper multicast router MR (S334), it checks whether the state is OPEN_TUN (S335), and if it is in the OPEN_TUN state, sends a deregistration message to the MSRH (S336), and joins the MH. The response message is transmitted (S337). If it is not in the OPEN_TUN state, the T1 and T2 timers are immediately stopped without passing through the steps S336 and S337 (S338), deleted from the visitor list (S340), and the state transitions to OPEN (S339, S341) Return the subscription completion result to the main processing module. If the main processing module (S10) has been informed of the result from the reference numeral S30, if the registration process was completed on the side of the registration request module (S20), which was previously performed in parallel, after performing a registration cancellation procedure for canceling it ( S317), and transmits a subscription response (subscription completion) message to the mobile terminal (S318). FIG. 5 shows a registration request from a mobile support router 30 (MSRF) of an external network for a mobile terminal belonging to a subnetwork according to FIG. The operation of the home network mobility support router 30 (MSRH) when receiving a message will be described by a flow chart. When a registration request message is received from the mobility support router 30 of the external network (S401), After recording the location information of the terminal in the mobile terminal location information storage (S405) (S402), and responds to the MSRF by a registration response message (S403), the state transitions to TUNNEL_ON_STATE (S401). Subsequently, the multicast data arrives not only to the subnetwork but also to the router of the network where the mobile terminal is located by referring to the mobile terminal location information storage device (S411). This multicast relay service continues until a deregistration message arrives from the MSRF. After receiving the deregistration message (S406), the MH related information is deleted in the mobile terminal location information storage, and the deregistration message is transmitted (S408). The present invention described above is conventional in the art to which the present invention pertains. It is not limited to the above-described embodiment and the accompanying drawings as those skilled in the art can make various substitutions, modifications, and changes without departing from the spirit of the present invention.

As described above, the present invention is a method for first re-subscribing to a multicast group to maintain the location information of the mobile terminal by checking the network characteristics and environment whenever the mobile terminal moves to a new network. By providing a method that can selectively use the method of registering its own location in the network-side router assigned the Internet address, it can efficiently handle the routing of multicast data, and it has excellent scalability and robustness to mobile terminals. This has the effect of providing a multicast service.

Claims (3)

Receives the subscription request message including the option based on the user's request or the multicast function support from the mobile terminal and determines the router to manage the location information of the mobile terminal using the current multicast group information Doing; If the mobile support router of the newly moved network does not support the multicast function according to the above conditions, or if the user wants to receive the multicast service through the mobile support router of the home network, the mobile terminal initially moves to the network to which the address is assigned. Requesting registration of a location information of the support router and receiving a response; If the mobile support router of the moved external network is already subscribed to the multicast group, if the mobile terminal sends a subscription response message, and the mobile support router of the moved external network is not subscribed to the multicast group. Temporarily performing the above process of transmitting a JOIN / GRAFT message to join a routing tree depending on the multicast routing scheme being used and then requesting registration with a router of a network to which an address has been initially assigned; Receiving multicast data directed to a mobile terminal through a tunnel of a mobile support router of a home network; And Receiving a response message for JOIN / GRAFT from an upper router supporting multicast, if a tunnel is temporarily set, after canceling the tunnel, notifying the mobile terminal that the subscription is completed; A multicast data handoff control method for supporting a mobile terminal in an internet multicast environment. Receives the subscription request message including the option based on the user's request or the multicast function support from the mobile terminal and determines the router to manage the location information of the mobile terminal using the current multicast group information Doing; If the mobile support router of the newly moved network does not support the multicast function according to the above conditions, or if the user wants to receive the multicast service through the mobile support router of the home network, the mobile terminal initially moves to the network to which the address is assigned. Requesting registration of a location information of the support router and receiving a response; If the mobile support router of the moved external network is already subscribed to the multicast group, if the mobile terminal sends a subscription response message, and the mobile support router of the moved external network is not subscribed to the multicast group. Temporarily performing the above process of transmitting a JOIN / GRAFT message to join a routing tree depending on the multicast routing scheme being used and then requesting registration with a router of a network to which an address has been initially assigned; Receiving multicast data directed to a mobile terminal through a tunnel of a mobile support router of a home network; And When receiving a response message for JOIN / GRAFT from an upper router supporting multicast, if a tunnel is temporarily set, the program for executing the step of notifying the mobile terminal that the subscription is completed after canceling the tunnel. A computer-readable recording medium that records the data. The method of claim 1, Processing the registration request message, Receiving a registration request message from a mobility support router of the external network, storing location information of the mobile terminal and responding with a registration response message; And And receiving the multicast data destined for the mobile terminal registered in the location information storage device, and transmitting the data to the mobile support router of the external network through the established tunnel.