KR20050075645A - Multicast service method for fast handoff in mobile ip network - Google Patents

Abstract

The present invention provides a mobile communication system using a mobile IP network including a plurality of access routers for providing data to a mobile host, wherein the mobile host is provided with a multicast service in a high-speed handoff to a new access router. Receiving information for the fast handoff from a previous access router as the mobile host moves to receive a message from the new access router, and performs fast binding update message on the newly set multicast information through the received information. And transmitting the multicast information to the new access router through the old access router, and transmitting the multicast information to the new access router through the old access router. Receiving a verification result of whether or not a network is supported, transmitting to the new access through a fast neighbor advertisement message indicating that the multicast information is connected to the new access router according to the verification result; And receiving data received from the previous access router through the access router.

Description

Multicast service method for mobile IP network {Multicast service method for fast handoff in mobile IP network}

The present invention relates to a method for handoff in a mobile IP network. In particular, the present invention relates to a multicast service method for minimizing data loss and delay time by a mobile host during high-speed handoff in mobile IPv6.

Recently, due to the development of the mobile communication network and the increase of the wireless LAN service, the number of users using the mobile host is increasing. Accordingly, there has been a growing interest in how mobile hosts handoff. The technique used in the Internet to manage the location of the mobile host and provide seamless communication even during handoff is the Mobile IP provided by the Internet Engineering Task Force (IETF) as a Request For Comment (RFC). IP) technology. There are two types of mobile IP technologies, Mobile IPv4 and Mobile IPv6 technologies, depending on the version of the IP (Internet Protocol, hereinafter abbreviated as IP).

In Mobile IPv4, a home agent (hereinafter referred to as HA and abbreviated as HA) and a visitor agent (hereinafter referred to as FA and abbreviated as FA) are defined to support a mobile host and location management of the mobile host is performed. Here, the HA exists in the home network of the mobile host, and the FA exists in the network that the mobile host has handed off. In Mobile IPv4, whenever a handoff is performed, the mobile host informs the HA of its current location information. At this time, the HA records the location information of the mobile host, and when there is data destined for the mobile host, the HA intercepts and encapsulates the data and delivers the data to the FA through the tunnel. Pass the data received from the mobile host. In this case, since the data delivered to the mobile host is always delivered via HA, there is a problem that the delivery path is not optimized. Thus, a route optimization (RO) technique is applied to improve the problem.

Mobile IPv6 has been proposed to accept the advantages of IPv6, to support mobile hosts in IPv6 networks, and basically adopts the RO optimization technique, so that FA is not the end of the tunnel and the mobile host takes over the role. Done. The Mobile IP protocol causes a large delay time when the mobile host performs handoff, and thus, data loss occurs when the mobile host performs the handoff. In order to compensate for this, a fast handoff technique is applied.

Fast handoff can reduce the time it takes to know that a mobile host is moving to a new network by providing subnet prefix information for the new access network while still connected to the old access router. Therefore, the mobile host can reduce a lot of delay time for handoff. In addition, a tunnel is established between the access router of the current network and the access router of the mobile network, and the access router of the current network passes the data delivered to the mobile host to the access router of the network to which the mobile host moves to minimize the loss of data. do.

If a mobile host is provided with multicast service in Mobile IPv6, the access router of the network where the mobile host is located must join the multicast tree and the access router must deliver the received data to the mobile host. However, when the mobile host performs a handoff, the access router of the new network does not know that the mobile host is receiving multicast service. Therefore, after performing the handoff, the mobile host should request the access router to subscribe to the multicast tree and deliver the multicast data in order to receive the multicast service. This allows the access router to join the multicast tree and forward the data. In this process, the mobile host, along with the delay time for handoff, suffers more delay until the access router joins the multicast tree and delivers the data, so that the multicast data transmitted during that time cannot be received.

However, high-speed handoff in Mobile IPv6 is a protocol related to general data transfer, and even if high-speed handoff is used to reduce the delay time caused by handoff of the mobile host, it is difficult to provide a multicast service. In addition, although the mobile host reduces the delay time caused by the handoff by using the fast handoff, a delay time is inevitably caused by restarting the process for the multicast service after performing the handoff.

Accordingly, an object of the present invention is to provide a method for a mobile host to receive a multicast service in an environment in which fast handoff of mobile IP version 6 is performed.

It is another object of the present invention to provide a method for minimizing loss of data together with a delay time for a multicast service request by an access router of a network to be moved during a high speed handoff in advance.

Another object of the present invention is to multicast through a tunnel established between the access router of the previous network and the access router of the current network even if the access router has not completed the procedure of joining the multicast after the mobile host has completed the handoff. The present invention provides a method for receiving a service.

The above method for achieving the object of the present invention is a mobile communication system using a mobile IP network including a plurality of access routers for providing data to a mobile host, the mobile host is multicast on a high-speed handoff to a new access router A method for receiving a service, the method comprising: receiving information for the fast handoff from a previous access router as the mobile host moves and receives a message from the new access router; Including cast information in the fast binding update message to the previous access router, transmitting the multicast information to the new access router through the old access router, and through the old access router Receiving a verification result of whether a new access router supports the multicast service, and performing a fast neighbor advertisement message indicating that the multicast information is connected to the new access router according to the verification result. And transmitting data received from the previous access router through the new access router.

 And another method for achieving the objects of the present invention is a mobile communication system using a mobile IP network including a plurality of access routers for providing data to a mobile host, the mobile host is multi- A method for receiving a cast service, the method comprising: receiving information for the fast handoff from a previous access router as the mobile host moves and receives a message from the new access router, and newly established through the received information. Sending a fast binding update message including multicast information to the new access router, if a response to the fast binding update message is not received from the previous access router, or transmitting a fast binding update message. If the mobile host moves without moving, the fast binding update message is included in a fast neighbor advertisement message indicating that the new access router is connected to the new access router, and the new access router supports the multicast service. And receiving data received from the previous access router through the new access router.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

It should be noted that the present invention described below can be applied to the proposed fast handoff without much modification in order to reduce the delay time in the handoff of the mobile host. The present invention should assume that an access router of a new network to which a mobile host moves to provide a multicast service to a mobile host joins a multicast tree for the mobile host.

And, as a protocol for managing multicast groups, multicast listener discovery (hereinafter referred to as MLD) is basically used. MLD is a protocol for managing multicast groups in an IPv6 network. The basic role of MLD as an extension protocol of Internet Control Message Protocol version 6 (ICMPv6) is to use Internet Group Management Protocol (hereinafter referred to as IGMP). similar. The IGMP defines three messages: Query, Report, and Done. Using this, the multicast router can determine whether a host to receive multicast service exists in the current network. have.

In addition, in order to perform the fast handoff of the present invention, each access router (AR) needs to know information about ARs existing in its neighbor network in advance, and in order for the AR to provide a multicast service, the AR can access its neighbors. Information on whether or not multicasts are provided by ARs in the network should also be known.

Hereinafter, an embodiment of the present invention provides a protocol for providing a multicast service in a high speed handoff environment, for example, by using predictive fast handoff and reactive fast handoff. The description will be made separately.

1 is a diagram illustrating a structure of a mobile network system according to embodiments of the present invention.

In the mobile network system, as shown in FIG. 1, a mobile host (or mobile node: MN) 10a is connected to a multicast server 40 to receive multicast data. . The mobile host 10a is connected to access routers AR1 and AR2 20a and 20b connected to the multicast server 40. The access routers 20a and 20b are connected to the router 30a, which is connected to other routers and the multicast server 40 through the Internet. Although only one router 30a is shown in FIG. 1, a plurality of routers may be hierarchically connected between the multicast servers 40.

An operation of the mobile network system having such a structure will be described with reference to FIG. 1.

In step 100, the current mobile host 10a is located in the network of the access router 20a and receives multicast data from the multicast server. The access router 20a is an access router supporting Mobile IPv6, supports fast handoff, and accepts the multicast service requested by the mobile host 10a.

The mobile host 10a finds that it needs to handoff, and in step 102, a router request message for proxying with the access router 20a (hereinafter, referred to as a router solicitation for proxy, abbreviated as "RtSolPr") / proxy router advertisement message (hereinafter abbreviated as "PrRtAdv") in exchange of messages, the link layer address of the access router 20b, the IP address, the subnet prefix of the neighboring router, and the new care-of address (NCoA: New Care). of Address). In addition, the mobile host 10a finds out that the access router 20b supports multicast through the M bit included in the "PrRtAdv" message. Thereafter, in step 104, the mobile host 10a adds a M bit to the mobility header and includes a fast binding update message (hereinafter, abbreviated as FBU) including a mobility header multicast option. After forwarding to the access router 20a, fast handoff is started. Accordingly, in step 106, the access router 20a receives the FBU message, and then accesses the multicast option included in the FBU message with the ICMPv6 multicast option in the handoff initiation (Handoff Initiate or shorter term, HI) message. 20b).

In step 108, the access router 20b starts a multicast group joining procedure for the mobile host 10a before sending a handover acknowledgment (hereinafter, abbreviated as HAck) message in response to the handoff initiation. In step 110, the Mck is added to the HAck message ICMPv6 Header, which is a response to the HI message, to transmit a response to the access router 20a whether to provide or reject a service for the transmitted multicast address. Accordingly, in step 112, the access router 20a receives the HAck message, transmits a fast binding acknowledgment message (hereinafter, abbreviated as FBack) message, and sends data destined for the mobile host 10a to the access router 20b. To pass. After that, when the mobile host 10a reaches the network of the access router 20b by handing off, the mobile host 10a accesses using a fast neighbor advertisement message (FNA) in step 114. Inform the router 20b that it is connected to the network.

If the multicast subscription in step 116 is completed after the FNA message delivery in step 114, the access router 20b forwards the message forwarded from the access router 20a to the mobile host 10a in step 118. When the multicast data is delivered as time passes and the multicast subscription of the access router 20b is completed, the access router 20b transfers the data delivered from the multicast server 40 to the mobile host in step 118. Pass it to (10a). At this time, the mobile host 10a is delivered from the previous access host (PAR) 20a until the MLD query message is received from the new access host (NAR) 20b. Respond to a query message with an MLD report message. After this operation, when a query message arrives from the new mobile host 20b, the mobile host 10a responds to the query message of the previous mobile host 20a with a done message, thereby responding with the previous host. The multicast service from 20a is stopped. The mobile host 10a then sends a report message for the query message of the new mobile host 20b.

On the other hand, if the multicast subscription procedure is completed before the multicast subscription in step 116 rather than the FNA message transmission in step 114, the access router 20b completes the multicast subscription procedure in step 130 and multicasts the FNA message of the mobile host 10a. The data starts arriving first. In this case, in step 132, the mobile host 10a sends an FNA message, and in step 134, the access router 20b transmits multicast data to the mobile host 10a.

A procedure for a mobile host to receive a high speed multicast service in a mobile network system performing such an operation will be described with reference to the accompanying drawings.

2 is a flowchart illustrating a procedure for a mobile host to receive a fast multicast service according to a first embodiment of the present invention.

In step 200, the mobile host starts a basic operation. In step 202, the mobile host determines whether it is receiving a multicast service. If not receiving the multicast service, the mobile hose performs a normal fast handoff operation in step 204. On the other hand, if receiving a multicast service, in step 206, it is determined whether a new access router (NAR) supports multicast through the M bit of the PrRtAdv message. If the determination result does not support multicast, in step 212, multicast data is transmitted from the previous access router (PAR). On the contrary, if the result determined in step 206 supports multicast, in step 208, multicast-related information is set in the FBU message and transmitted.

Thereafter, in step 210, the mobile host determines whether the multicast process is successful through a fast binding acknowledgment (Fback) message. If the NAR does not provide a service for the multicast address, the mobile host continues to receive multicast data from the previous access router (PAR) in step 212 and terminates the operation. On the other hand, if the NAR provides a service for the multicast address, in step 214, the mobile host forwards to the new access router (NAR) including the multicast option in the previous FNA message after the handoff.

Then, in step 216, the mobile host determines whether the multicast subscription is completed in the new access router (NAR). Here, the mobile host must receive data from the previous access router (PAR) before the multicast subscription is completed in the new access router (NAR). Therefore, until the multicast group join of the new access router (NAR) is completed, service continues from the previous access router (PAR) in step 216. If the determination result in step 216 is complete, in step 218, the mobile host transmits an MLD done message to the previous access router PAR, and then ends the operation. Accordingly, the previous access router PAR stops forwarding multicast data to the mobile host after receiving the completion message. A message flow in a procedure for receiving such a multicast service will be described in detail with reference to the accompanying drawings.

3 is a flowchart illustrating a message flow according to a first embodiment of the present invention. 3 illustrates the message contents changed from the existing fast hand off message.

 In step 300, the mobile host (MN) 10a sends a router request message (RtSolPr) for proxy, which is a message requesting information for fast handover, to the previous access router (PAR) 20a. Accordingly, in step 302, the previous access router 20a delivers the access router information to the mobile host 10a through the proxy router advertisement message PrRtAdv. At this time, the M bit of the "PrRtAdv" message indicates whether the new access router (NAR) 20b supports multicast.

 In step 304, the mobile host 10a forms a prospective new care of address (NcoA) and transmits a fast binding update message (FBU) to the previous access router 20a. Here, the FBU is a message indicating that the mobile host 10a needs to redirect traffic to the old access router 20a to the new access router 20b. Therefore, the FBU gives the previous access router 20a the authority to bind the old referral address (PcoA valid CoA) and the new referral address NCoA (CAR valid NAR) to the previous access router 20a. Allow tunnel to location. At this time, the mobile host 10a sets the M bit bit in the mobility header of the FBU, and transfers the old access router through the mobility header multicast option, which is a new mobility header option. Tell 20a of its own multicast information (multicast address).

 In step 306, the previous access router 20a receiving the FBU from the mobile host 10a transmits a handoff initiation (HI) message to the new access router 20b. HI is a message for initiating a handoff from the old access router 20a to the new access router 20b. At this time, the previous access router 20a transfers the contents of the mobility header multicast option included in the FBU to the new access router 20b as the ICMP multicast option of HI. This means that the mobile host 10a informs the new access router 20b of its multicast information (multicast address) via the old access router 20a.

Meanwhile, in step 308, the new access router 20b starts the joining procedure to join the multicast group. In step 310, the new access router 20b receives the handover initiation message HI from the previous PAR and transmits a handover response message (Hack) message to the previous access router 20a in response thereto. In this case, the handover initiation message HI in step 306 and the handover response message in step 310 are transmitted to verify whether the expected NCoA can be used. The new access router 20b sets M bits in the ICMPv6 header of the handoff response Hack in response to the handoff initiation message HI and forwards them to the previous access router 20a. Alternatively, when receiving multiple forwarded multicast services, an ICMPv6 multicast option, such as a handover initiation (HI) message, is added to respond whether to provide or reject a service for a specific multicast service address.

In step 312, the previous access router 20a transmits the fast binding response message FBack to the mobile host 10a and the new access router 20b in response to the FBU. The mobile host 10a must then use the available NCoA, that is, sent to HI and verified by the new access router 20b or assigned by the new access router 20b when connecting to the new access router 20b. . At this time, the previous access router 20a sets the mobility header of the FBack to M bits or adds a mobility header multicast option to the FBack to the mobile host 10a and the new access router 20b. To pass.

 In step 314, the previous access router 20a transfers data destined for the mobile host 10a to the new access router 20. In step 316, the mobile host 20a transmits a fast neighbor advertisement (FNA) to a new access router (NAR). The Fast Neighbor Advertisement Message (FNA) is a message sent from the MN to the NAR. When the MN receives the fast binding response message (FBACK), it establishes a new care of address (NcoA) and connects to the new access router (NAR). It is to inform that. At this time, the mobile host 10a adds a mobility header multicast option to the fast neighbor advertisement message (FNA), and transmits the same to the new access router 20b. Informs you that you are connected to the network. In operation 318, the mobile host 10a determines whether joining the multicast group is completed.

Then, in step 320, the new access router 20b transmits the data received from the previous access router 20a to the mobile host 10a after receiving the FNA.

In the first embodiment of the present invention, a method for providing a multicast service in a predictive fast handoff environment has been described, but in the second embodiment of the present invention, a reactive fast handoff environment is provided. It will be described how to provide a multicast service. Hereinafter, the structure and operation of the mobile network system in the case where reactive fast handover occurs will be described with reference to steps 400 to 430 as shown in FIG.

In the mobile network system, as illustrated in FIG. 1, a mobile host (MN) 10b is connected to a multicast server 40 to receive multicast data. . The mobile host 10b is connected to access routers AR1 and AR2 20c and 20d connected to the multicast server 40. The access routers 20c and 20d are connected to the router 30b, and the router 30b is connected to other routers and the multicast server 40 through the Internet. Although only one router 30b is illustrated in FIG. 1, a plurality of routers may be hierarchically connected between the multicast servers 40.

An operation of the mobile network system having such a structure will be described with reference to FIG. 1.

In step 400, the mobile host 10b is located in the network of the current access router AR3 20c and wants to hand off to the network of the new access router AR4 20d. The mobile host 10b receives a multicast data from the multicast server 40.

Thereafter, if the mobile host 10b finds that it needs to handoff to the new access router AR4 20d, the mobile host 10a determines the link layer address, IP of the new access router 20d in step 402. The RtSolPr / PrRtAdv message is exchanged with the access router 20c of the current network to obtain the address and prefix information of the neighboring router. Thereafter, in step 404, the mobile host 10b performs handoff, encapsulates the FBU message in the FNA message, and transmits the FBU message to the network of the new access router 20d. In this case, the FBU adds an M bit to the mobility header and includes a mobility header multicast option.

In step 406, the new access router 20d may obtain information on the multicast group to which the mobile host 10a wants to subscribe through the FBU message, and thus start the corresponding multicast group joining procedure. In addition, in step 408, the new access router 20d receiving the FBU message establishes a tunnel through the FBU / FBack message exchange with the previous access router 20c. In this case, if the multicast service joining procedure is completed in step 412, the previous access router 20c transmits the multicast data to the mobile host 10b through a tunnel established with the new access router 20d in step 410. To the new access router 20d.

In step 414, the new access router 20d delivers the received multicast data to the mobile host 10b. In this case, the mobile host 10b responds to the previous access router 20c with an MLD report message for the MLD query message sent from the previous access router 20c.

On the other hand, when the multicast service subscription procedure of the new access router 20d ends in step 430, the new access router 20d directly transmits the multicast data to the mobile host 10b. Accordingly, the mobile host 10b responds with an MLD done message to the MLD query message sent from the previous access router 20c.

A procedure for a mobile host to receive a high speed multicast service in a mobile network system performing such an operation will be described with reference to the accompanying drawings.

4 is a flowchart illustrating a procedure for a mobile host to receive a fast multicast service according to a second embodiment of the present invention.

In step 500, the mobile host starts a basic operation. In step 502, the mobile host determines whether it is receiving a multicast service. If the multicast service is not provided, the mobile host performs a general handoff process in step 504. In contrast, if a multicast service is provided, the mobile host determines whether a new access router (NAR) of a network to be handed off supports multicast using the M bit of the PrRtAdv message in step 506. If the new access router (NAR) does not support multicast in step 506, the process proceeds to step 512 to transfer multicast data from the previous access router (PAR). This process is done in the same way as described for predictive fast handoff. That is, the previous access router (PAR) periodically transmits the MLD query message through the tunnel, and the mobile host terminates the operation after transmitting the MLD report message in response. At this point, the previous access router continues to forward the multicast data to the mobile host. However, in a reactive handoff, since the handoff is already performed before transmitting the FBU message, the FBU message is encapsulated in the multicast FNA message and transmitted to the new access new access router 20d. That is, if the result determined in step 506 supports multicasting, the process proceeds to step 508 and adds a multicast option to the FBU included in the FNA message and delivers it.

Thereafter, in step 510, the mobile host determines whether the new access router 20D has completed the multicast subscription. When the multicast subscription is completed, the mobile host transmits an MLD complete message to the previous access router 20c in step 516. The operation ends after no longer receiving the multicast data from the previous access router 20c. A message flow in a procedure for receiving such a multicast service will be described in detail with reference to the accompanying drawings.

5 is a flowchart illustrating a message flow according to a second embodiment of the present invention.

In step 600, the mobile host 10b sends a router solicitation for proxy (RtSolPr), which is a message requesting information for fast handover, to the previous access router. Then, in step 602, the previous access router 20c transmits the access router information to the mobile host 10b through the received proxy router advertisement (PrRtAdv) message. At this time, the M bit of the ICMPv6 header of the proxy router advertisement message (PrRtAdv) is set to inform whether the new access router 20d supports multicast.

 If the mobile host 10b does not receive the fast binding response message (FBACK) from the previous access router 20c in step 604, for example, it does not send a fast binding update message (FBU), or sends an FBU message and receives a FBACK message. If the previous access router 20c was previously left, the mobile host 10b encapsulates the FBU message to the new access router 20d to transmit a fast neighbor advertisement message (FNA). This is a process for the new access router (NAR) to verify that a new care of address (NcoA) can be used. If a new referral address (NcoA) is in use, discard the FBU message packet inside and send an alternative new referral address (NcoA) to the Router Advertisement with the NAack (Neighbor Advertisement acknowledge) option set. do. In this case, the fast neighbor advertisement message (FNA) is a message sent from the mobile host 10b to the new access router 20d, and establishes a new care of address (NcoA) and sends a new care of address (NcoA) to the new access router 20d. Informs you that you are connected. At this time, the mobile host 10b sets the M bit of the mobility header of the FBU and transmits its multicast information (multicast) to the new access router 20d through the mobility header multicast option. Address). In operation 606, the new access router 20d performs a group joining procedure to join the multicast group.

 In step 608, the mobile host 10b connects to the new access router 20d and transmits an FBU message to the old access router 20c. Here, the FBU is a message informing that the mobile host 10b should redirect traffic to the new access router 20d to the old access router 20c. Therefore, the FBU gives the previous access router 20c the right to bind the old care-of address (PcoA: valid CoA in PAR) and the new care-of address (NcoA: CoA valid in NAR) to move the packet. To be tunneled to the desired location.

 In step 610, the previous access router 20c transmits a fast binding response (FBACK) message to the new access router 20d in response to the FBU, and transmits data destined for the mobile host to the new access router 20d in step 612. forward. Accordingly, in step 614, it is determined whether the joining of the multicast group is completed in the mobile host 10b.

Then, in step 616, the new access router 20d transmits the data received from the previous access router 20c to the mobile host 10b.

In the fast handoff according to the above-described embodiments, the proxy router advertisement message PrRtAdv, the handover initiation message HI, and the handover response message use an ICMPv6 header. The fast binding update message FBU, the fast binding response message Fback, and the fast neighbor advertisement message FNA use a mobility header. In addition, embodiments of the present invention indicate whether a new access router (NAR) can provide a multicast service by adding an M bit to an ICMPv6 header in a proxy router advertisement message (PrRtAdv).

In the Predictive Fast Handover of the first embodiment of the present invention, a handover initiation / handover response (HI / Hack) message using an ICMPv6 header may use an expected new care-of address (NcoA). Message to verify whether or not. In addition to this purpose, HI adds a newly defined ICMPv6 multicast option to pass multicast information (multicast address information) from the old access router (PAR) to the new access router (NAR).

On the other hand, a handover response message (Hack) sent from a new access router (NAR) to an old access router (PAR) adds an M bit to an ICMPv6 header to determine whether to service or reject a forwarded multicast address. Answer the question. In this case, when receiving multiple multicast services, an ICMPv6 multicast option may be added, such as handover initiation (HI), to transmit only information on a specific multicast service.

In the Predictive fast handover, a fast binding update message (FBU) using a mobility header is used by a mobile host to send traffic to a previous access router (PAR) to a new access router (NAR). This message tells you that you should. In the case of the fast binding update message (FBU), the MN is added to the mobility header to indicate that the mobile host (MN) requests a multicast service. If the M bit is set, the mobile host (MN) Must add a mobility header multicast option to inform the previous access router (PAR) of multicast information (multicast address).

The fast binding response message (FBack) is a response to the fast binding update message (FBU), and in the case of predictive fast handover, the previous access router (PAR) is the M of the handover response (Hack) message The M bit is set in the mobility header of the fast binding response message (FBack) and transmitted to a new access router (NAR) and a mobile host (MN). In this case, when the mobile host (MN) is receiving a plurality of multicast services, the mobility header multicast option may be added to transmit only information on a specific multicast.

In Predictive Fast Handover, the Fast Neighbor Advertisement Message (FNA) conveys information (multicast address) about the multicast requested by the mobile host (MN) through the mobility header multicast option so that the mobile host (MN) has new access. This message enables to receive a service after connecting to the router 20d.

On the other hand, in the case of reactive fast handoff, the multicast option of the mobility header is multiplied at the time of encapsulating a fast binding update (FBU) message in a fast neighbor advertisement message (FNA). Except for passing cast information, there is no particular difference from the existing reactive fast handoff and message formats.

Each message format of these messages will be described in detail. The field size of each message is indicated by the number of bits.

FIG. 6 is a diagram illustrating the format of a header of a router advertisement message (PrRtAdv) message for proxy according to embodiments of the present invention.

Referring to 6, the router advertisement message PrRtAdv for proxy further defines the first bit as a M bit in the reserved field. The M bit indicates whether the new access router can provide a multicast service through the router request message (RtSolPr) for proxy of the mobile host (MN). If the service can be provided, the M bit is set to 1, otherwise it is set to 0. The mobile host (MN) does not consider the M bit unless it wants to receive a multicast service.

By using the M bit included in the Router Advertisement Message (PrRtAdv) message for such a proxy, the mobile host can know whether the mobile host can receive the multicast service. If a mobile host wants a multicast service and the new access router (NAR) can also support it, the mobile host includes its multicast information in a fast binding update message (FBU) as follows. Let's pass it together.

7A and 7B illustrate a multicast option of a mobility header and a mobility header of a fast binding update message according to embodiments of the present invention.

Referring to FIG. 7A, the FBU adds M bits to the mobility header portion in addition to the existing A, H, L, and K bits. The M bit means that the mobile host requests a multicast service. Therefore, if the M bit is set, information of a multicast service as shown in FIG. 7B should be included as an option. The currently defined multicast service information indicates a multicast address currently being serviced by a mobile host. A mobile host may be receiving multiple multicast services as well as one multicast. Accordingly, as shown in FIG. 7B, the multicast option includes a number field in addition to the type and length fields to determine how many multicast addresses are currently included. The multicast option is delivered to the mobility header option in the FBU.

When the previous access router (PAR) receives such a fast binding update message (FBU) from the mobile host, it knows that the mobile host will perform a handoff and sends this information to the handover initiation message HI. The exchange of handover response messages (HAck) informs the new access router (NAR). In order to deliver multicast information to the HI / HAck message exchange, the HI message adds ICMPv6 multicast option information as shown in FIG. 8.

As shown in FIG. 8, the previous access router PAR transmits the HI message with the newly defined ICMPv6 multicast option. The information contained in the option indicates a multicast address that the mobile host informs the previous access router (PAR) in the FBU. In addition, since multiple addresses can be delivered, a number field is provided in the multicast option to indicate how many addresses are delivered. Here, the sub-type field is set to zero.

If a new access router (NAR) receiving the above HI message can provide a multicast service for such a multicast service request, a handover acknowledgment message (Hack: Hand over acknowledgement) as shown in FIG. Set and transmit M bit. The M bit indicates whether the new access router NAR accepts or rejects the multicast address delivered by the previous access router PAR.

In the HI message, as shown in FIG. 8, all information on the multicast service desired by the mobile host is delivered, but the result of the handover response message (Hack) as shown in FIG. 9 is one M bit. Is defined. In this case, when a new access router (NAR) accepts only a part of the multicast service delivered as a handover initiation message (HI) and rejects a part of the multicast service, the M bit alone cannot inform the result. Accordingly, the Hack message as shown in FIG. 9 can extend the M bit to express the acceptance and rejection for each multicast information transmitted in the handover initiation message HI.

The method of extending the M bit may be defined in two ways. The first method is a method of extending a reserved field, as shown in FIG. 9. That is, instead of using only one M bit, M bits are set as many as the number of multicast services delivered in the handover initiation message (HI). For example, if five multicast information is transmitted in the handover start message HI, five M bits are set. In this case, since the reserved field is limited to 13 bits, only up to 13 multicast services can be processed. However, since the reserved field becomes 7 bits in the fast binding response message (FBack) to be described later, only up to 7 multicast services can be processed.

The second method is to add an ICMPv6 multicast option such as a handover initiation message (HI) message to a handover response message (Hack). This may inform acceptance and rejection of all multicast service information delivered in the handover initiation message (HI), and may only convey information about the multicast service accepted by the new access router (NAR).

The new access router (NAR) informs the previous access router (PAR) of the multicast service by accepting the result of the acceptance or rejection of the multicast service through a handover response message (Hack) as described above. You will follow the procedure for signing up for.

In primitive fast handover, the previous access router (PAR) sees the M bit of the handover response message (Hack) and adds this information to the mobility header of the fast binding response message (FBack), as shown in FIG. 10A. Transmit by setting the same in one M bit. Then, in the case of primitive fast handover, the mobile host can check the M bit to know whether the desired multicast service request is successful. The M bit of the FBback message copies and pastes the M bit of the handover response message (Hack) received from the new access router (NAR), and thus can inform the result of up to seven multicast services.

 If a multicast option is used without using the M bit in the Hack message, it is necessary to define a new option that can be included in the mobility header. This option may use the mobility header multicast option defined in the present invention, as shown in FIG. 10B.

If the mobile host succeeds in the multicast request, it should inform the new access router (NAR) of its arrival after performing the handoff. Therefore, when transmitting a fast neighbor advertisement (FNA) to a new access router (NAR), it must also convey information about which multicast service it wants. Otherwise, when a new access router joins a multicast address contained in a handover initiation message (HI), it must have a care of address (CoA) of the HI message requesting it and information about each multicast address. However, since CoA is changeable, it cannot be an accurate value. Therefore, the safest method is to inform the new access router (NAR) of the multicast information it wants after the mobile host has completed the handoff. To this end, as shown in FIG. 10B, the mobile host defines a mobility header multicast option in a fast neighbor advertisement message (FNA) and transmits information on a multicast address together.

 Then, the new access router NAR starts to deliver multicast data to the mobile host for the multicast requested by the mobile host MN among the currently subscribed multicast services.

As described above, the present invention provides a multicast service of the mobile host to the current access router of the current network to provide the multicast service of the mobile host in a high speed handoff environment using mobile IPv6. The information is exchanged between the access router of the current network and the access router of the network to be handed off. This allows the mobile host to be provided with a multicast service immediately after performing a fast handoff without any additional delay or data loss irrelevant to the handoff. The access router of the network to which the mobile host will hand off may subscribe to the multicast service in advance for the mobile host, and the mobile host may prevent the loss of multicast data that may occur during the handoff. In addition, the present invention can be implemented without significant modification to the existing protocol for fast handoff, it is easily applicable to the existing protocol.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention reduces the delay time during handoff by reducing the preparation time for receiving the multicast using the messages of the fast handoff to receive the multicast service during the fast handoff. Since the loss of multicast data can be reduced, the mobile host can use the multicast service more efficiently, and the performance of the network can be improved.

1 is a diagram showing the structure of a mobile network system according to embodiments of the present invention;

2 is a flowchart illustrating a procedure for a mobile host to receive a fast multicast service according to a first embodiment of the present invention;

3 is a flowchart showing a message flow according to a first embodiment of the present invention;

4 is a flowchart illustrating a procedure for a mobile host to receive a fast multicast service according to a second embodiment of the present invention;

5 is a flowchart illustrating a message flow according to a second embodiment of the present invention;

FIG. 6 is a diagram illustrating a format of an Internet Control Message Protocol version 6 (ICMPv6) header of a Router Advertisement Message (PrRtAdv) message for proxy according to embodiments of the present invention; FIG.

7A and 7B illustrate multicast options of a mobility header and a mobility header of a fast binding update message according to embodiments of the present invention;

8 illustrates an ICMPv6 multicast option of a handover initiation message (HI) message according to embodiments of the present invention;

9 illustrates a format of a header of a handover response message (Hack) message according to embodiments of the present invention;

10A illustrates the format of a mobile header of a fast binding response message (FBack) according to embodiments of the present invention;

10B illustrates a multicast option of a mobility header of a Fast Neighbor Advertisement Message (FNA) or a Fast Banging Response Message (FBack) in accordance with embodiments of the present invention.

Claims (2)

A mobile communication system using a mobile IP network including a plurality of access routers for providing data to a mobile host, the method for receiving a multicast service when the mobile host receives a high speed handoff to a new access router, Receiving information for the fast handoff from a previous access router as the mobile host moves and receives a message from the new access router; Transmitting the newly set multicast information to the previous access router by including the newly set multicast information in the fast binding update message through the received information; Transmitting the multicast information to the new access router through the old access router; Receiving a verification result of whether the new access router supports the multicast service through the old access router; Transmitting the multicast information to the new access through a fast neighbor advertisement message indicating that the multicast information is connected to the new access router according to the verification result; Receiving the data received from the previous access router via the new access router. A mobile communication system using a mobile IP network including a plurality of access routers for providing data to a mobile host, the method for receiving a multicast service when the mobile host receives a high speed handoff to a new access router, Receiving information for the fast handoff from a previous access router as the mobile host moves and receives a message from the new access router; Transmitting a fast binding update message including newly set multicast information to the new access router through the received information; A fast neighbor indicating that the fast binding update message is connected to the new access router when the response to the fast binding update message is not received from the previous access router or when the mobile host moves without transmitting the fast binding update message. Sending it in the advertisement message to the new access router, Verifying whether the new access router supports the multicast service, Receiving the data received from the previous access router via the new access router.