KR100492137B1 - Method for fast handover in mobile IP network - Google Patents

Abstract

Each cache agent has a routing cache table. In the routing cache table, a terminal that is performing packet communication through a corresponding cache agent and a lower cache agent or an access router to forward packets for the terminal are registered. When the terminal enters the overlapping area of the network that is currently being serviced and the network to be moved forward, the terminal sends a pre-registration message. The cache agent receiving the preregistration message updates the routing cache table, and if the corresponding terminal is already registered in its routing cache table, sends the response to the preregistration message down, otherwise it sends the preregistration message to the upper cache agent. send. According to the updated routing cache table, packet communication with the terminal is performed through two paths, a previous path and a newly established path. If the terminal is completely out of the previous network in the state of pre-registration, the terminal sends a binding update message to the access router of the new network. When the cache agent receives the binding update message, if two paths are recorded for the terminal in its routing cache table, the packet is transmitted only through the new path by deleting the old path.

Description

Fast handover method in mobile IP network {Method for fast handover in mobile IP network}

The present invention relates to a fast handover method in a mobile IP network, and more particularly, to a method for reducing packet loss by pre-registration before a UE moves to a new network.

In a mobile IP network, a terminal, that is, a mobile node, generally accesses the Internet through a single access router. However, when the mobile node moves out of the area of the current access router, it is necessary to change to another access router and access the Internet network. In this case, you must be able to change the access router while maintaining the connection to the Internet. This process is called handover.

The IETF Mobile Working Group is proposing a fast handover process. The purpose of this protocol is to enable a new CoA (Care of Address) to be used immediately when the UE moves to a new network. The operation of this protocol is as follows.

1) The mobile node (MN) sends an RtSolPr (Router Solicitation for Proxy) message to perform a handover to an old access router (oAR).

2) In response to the RtSolPr message, oAR sends PrRtAdv (Proxy Router Advertisment) message that contains three layers of information needed to configure a new CoA in a new network.

3) oAR sends a Handoff Intitiate (HI) message to the new Access Router (nAR). This message contains the new CoA (nCoA) and the old CoA (oCoA) requested in the new network. nAR receives HI message nAR allocates nCoA if there is no nCoA in the HI message and checks if there is nCoA.

4) nAR sends a handoff acknowledgment (HACK) message to oAR indicating whether nCoA has been allocated or nCoA received from HI message is valid.

5) Send Fast Binding Update (F-BU) to oAR before MN moves to new network.

6) When the oAR receives the F-BU, it responds to the MN and nAR with a fast binding update acknowledgment (F-BACK) message.

7) oAR forwards the packet to nAR by forming a temporary tunnel during the F-BACK's lifetime upon receipt of the F-BU.

8) The MN moves to a new network and sends a Fast Neighbor Advertisement (F-NA) message to nAR requesting to send a forwarded packet from oAR.

9) The nAR receiving the F-NA message transmits a packet to the MN.

In the above handover method, when the UE enters the overlapping area and receives the advertisement message from the new network, registration is completed to the new access router that sends the advertisement message through the above operation process, and the handover is sent by sending the buffered packet from the previous access router. Ends. However, this method has the disadvantage that the packet may arrive late at the wireless terminal entering the new network by sending a buffered packet from the previous access router. In addition, this method defines six new messages for fast handover.

Meanwhile, a hierarchical MIPv6 mobility management method having a hierarchical structure has also been proposed.

In this hierarchical Mobile IPv6 structure, a new node called MAP (mobility anchor point) is defined. The MAP is a top node of the hierarchy, and handles handover in accordance with the movement of UEs in all access routers in the MAP domain. Therefore, the method reduces the delay due to handover by reducing the signal due to the movement of the terminal and reducing unnecessary overhead and time. The operation of the protocol is as follows.

1) When the MN moves to a new network and receives a Binding Advertisment (BA) message from the new access router, the MN sends a Binding Update (BU) message to the new access router.

2) The new access router sends the BU to the MAP and registers the mobile node in the binding cache.

3) The MAP sends a Binding Update Acknowledgment (BU ACK) message to the new access router as a response message to the BU.

4) The new access router sends a BU ACK message to the MN.

In this protocol, a packet transmitted from a CN (Correspondent Node) is sent to a MAP. The registration process to the home agent (HA) is only performed once when the MN first enters the network managed by the MAP, and thereafter, an additional HA registration process is not required due to the occurrence of a handoff. However, since MAP has to process all the messages in the domain, there is a drawback that MAP can incur overhead and degrade network performance.

An object of the present invention is to provide a method for handover without packet loss when a wireless terminal moves to a new network in a mobile IP environment.

Another object of the present invention is to provide a method for distributing overhead that may occur by managing the location of a terminal in a top router in hierarchical mobility management.

In the present invention, hierarchical cache agents each have a routing cache table. In the routing cache table, a terminal that is performing packet communication through a corresponding cache agent and a lower cache agent or an access router to forward packets for the terminal are registered. When a packet for a specific terminal reaches the cache agent, the cache agent forwards the packet to a subordinate cache agent or an access router assigned to the terminal with reference to the routing cache table. By repeating this process, the packet descends along the hierarchy of cache agents and finally reaches the access router to which the terminal belongs.

When the terminal enters the overlapping area of the network currently being serviced and the network to be moved forward, the terminal receives the advertisement message from the access router of the new network, the terminal sends a pre-registration message in response. The access router receiving the preregistration message sends the preregistration message to the upper cache agent. The cache agent receiving the preregistration message updates the routing cache table, and if the terminal is a terminal that is already registered in its routing cache table, sends the response to the preregistration message to the lower level; otherwise, preregisters with the upper cache agent. Send a message. According to the updated routing cache table, packet communication with the terminal is performed through two paths, a previous path and a newly established path.

If the terminal is completely out of the previous network in the state of pre-registration, the terminal sends a binding update message to the access router of the new network. When the cache agent receives the binding update message, if two paths are recorded for the terminal in its routing cache table, the packet is transmitted only through the new path by deleting the old path.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the hierarchical structure as shown in FIG. 1, each cache agent has a routing cache table. The routing cache table stores a terminal for which packet communication is performed through a corresponding cache agent and a lower cache agent or an access router for forwarding packets for the terminal. For example, if the mobile node MN2345 is connected to the cache agent CA6 through the access router AR2, and the mobile node MN2347 is connected through the access router AR3, the contents of Table 1 are stored in the routing cache table of the cache agent CA6.

Mobile node Lower layer MN2345 AR2 MN2347 AR3 ... ...

On the other hand, for the mobile node MN2345 connected through the access router AR2, the contents shown in Table 2 are stored in the cache agent of each layer.

Routing cache table Mobile node Lower layer GWR MN2345 CA1 CA1 MN2345 CA3 CA3 MN2345 CA6 CA6 MN2345 AR2

Therefore, when a packet for the mobile node MN2345 arrives at the gateway router GWR in the Internet network, the gateway router GWR refers to its routing cache table, and thus, a next hop assigned to the mobile node, that is, a cache. Forward the packet to agent CA1. Similarly, the cache agent CA1 receiving the packet searches for an item related to the mobile node in its routing cache table and delivers the packet to the next hop assigned to the mobile node, that is, CA3. By repeating this process, the cache agent CA6 forwards the packet to the access router AR2, and the access router AR2 forwards the packet to the mobile node MN2345 so that the packet from the Internet network is delivered to the mobile node MN2345.

The handover procedure when the mobile node MN in packet communication moves from the area of the access router AR2 to the area of the access router AR3 will be described with reference to FIG. 4.

When the mobile node MN is in the region of the access router AR2, the contents of Table 3 are stored in the routing cache table of the cache agents belonging to the packet communication path with the mobile node MN.

Routing cache table Mobile node Lower layer GWR MN CA1 CA1 MN CA3 CA3 MN CA6 CA6 MN AR2

When the mobile node MN moves from the area A of the access router AR2 to the overlap area B of the access router AR2 and the access router AR3, the mobile node MN sends a Binding Advertisement message from the access router AR3. (①).

The mobile node MN receiving the advertisement message BM sends a pre-registration binding update message to the new access router AR3 in response thereto (2). Pre-registration message (PBU) is a message proposed in the present invention, for example, in the conventional binding update (Binding Update) message as shown in Figure 2, or created by defining a new bit P indicating that as shown in Figure 3 , Or you can define a separate message.

The new access router AR3 receiving the pre-registration message PBU registers the terminal in its binding list, and sends the pre-registration message PBU to the cache agent CA6 located above (③).

The cache agent CA6 receiving the pre-registration message PBU checks whether the corresponding mobile node MN is registered in its routing cache table. If the mobile node (MN) is registered in its routing cache table, it means that the packet communication is already made through itself. Therefore, the cache agent passes a path for packet communication with the mobile node (MN) to the upper cache agent. There is no need to ask to make.

In the case of FIG. 4, since the mobile node MN is already registered in the routing cache table of the cache agent CA6, as shown in Table 3, the routing cache table of the cache agent CA6 does not transmit the pre-registration message (PBU) to the upper cache agent. Update as shown in Table 4. That is, the access router which has transmitted the pre-registration message PBU is added to the record of the corresponding mobile node MN in its routing cache table.

Mobile node Lower layer MN AR2, AR3

Then, subsequent packets to the mobile node MN are delivered to both the access router AR2 and the access router AR3 according to the routing cache table of the cache agent CA6.

The cache agent CA6, which has updated the routing cache table, sends a binding acknowledgment message to the new access router AR3 (4). The access router AR3 receiving the binding response message BACK sends the message to the corresponding mobile node MN to inform that the pre-registration is completed (⑤).

In this state, when the mobile node MN moves to the area C of the new access router AR3, the mobile node MN transmits a binding update message BU to the new access router AR3 (6). ).

Upon receiving the binding update message, the access router AR3 transmits it to the cache agent CA6 (⑦). Receiving the binding update message, the cache agent CA6 updates its routing cache table as shown in Table 5.

Mobile node Lower layer MN AR3

Then, subsequent packets to the mobile node MN will be delivered only to the access router AR3 according to the routing cache table of the cache agent CA6, thereby ending the handover process.

Next, a handover process occurring between different cache agents will be described with reference to FIG. 5.

When the mobile node MN is in the area of the access router AR3, the contents of Table 6 are stored in the routing cache table of the cache agents belonging to the packet communication path with the mobile node MN.

Routing cache table Mobile node Lower layer GWR MN CA1 CA1 MN CA3 CA3 MN CA6 CA6 MN AR3

On the other hand, the new access router AR4 to which the mobile node MN will move is assigned to a different cache agent CA7 than the current access router AR3. Therefore, the mobile node MN is not registered in the routing cache table of the cache agent CA7 until the mobile node MN moves to the area of the access router AR4.

When the mobile node MN moves from the area D of the access router AR3 to the overlapping area E of the access router AR3 and the access router AR4, the mobile node MN sends a Binding Advertisement message from the access router AR4. (①).

The mobile node MN receiving the advertisement message BM sends a pre-registration binding update message to the new access router AR4 in response thereto.

The new access router AR4, which has received the pre-registration message PBU, registers the terminal in its binding list, and sends the pre-registration message PBU to the cache agent CA7 located above (③).

The cache agent CA7 receiving the pre-registration message PBU checks whether the corresponding mobile node MN is registered in its routing cache table. If the mobile node (MN) is not registered in its routing cache table, it means that no packet communication is made through itself. Therefore, the cache agent transmits a packet to the upper cache agent for packet communication with the mobile node (MN). You need to ask to create a route.

In the case of FIG. 5, since the mobile node MN is not registered in the routing cache table of the cache agent CA7, the cache agent CA7 registers the mobile node MN in its routing cache table as shown in Table 7 below. The pre-registration message PBU is transmitted to the upper cache agent CA3 (④).

Mobile node Lower layer MN AR4

The cache agent CA3 receiving the pre-registration message PBU checks whether the corresponding mobile node MN is registered in its routing cache table. Since the mobile node MN is already registered in the routing cache table of the cache agent (CA3), as shown in Table 6, instead of sending a pre-registration message (PBU) to the parent cache agent, the routing cache table is displayed as shown in Table 8. Update That is, the subordinate cache agent that has transmitted the pre-registration message PBU is added to the record of the corresponding mobile node MN in its routing cache table.

Mobile node Lower layer MN CA6, CA7

Then, subsequent packets to the mobile node MN are delivered to both the access router AR3 and the access router AR4 according to the routing cache tables of the cache agents CA3, CA6, and CA7.

The cache agent CA3 that has updated the routing cache table sends a binding acknowledgment message to the lower cache agent CA7 (⑤). The cache agent CA7 receiving the binding response message BACK sends it back to the access router AR4 (6).

The access router AR4 receiving the binding response message BACK informs that the pre-registration is completed by sending it to the corresponding mobile node MN (⑦).

In this state, when the mobile node MN moves to the area F of the new access router AR4, the mobile node MN transmits a binding update message BU to the new access router AR4 (8). ).

Upon receiving the binding update message, the access router AR4 transmits it to the cache agent CA7 (9). Receiving the binding update message, the cache agent CA7 sends it back to the parent cache agent CA3 (⑩).

Receiving the binding update message, the cache agent CA3 updates its routing cache table as shown in Table 9.

Mobile node Lower layer MN CA7

Then, subsequent packets to the mobile node MN are delivered only to the access router AR4 according to the routing cache tables of the cache agents CA3 and CA7, thereby ending the handover process.

On the other hand, the cache agent CA3 receiving the binding update message sends a message indicating the end of packet transmission to the previous cache agent CA6 registered in its routing cache table so that the previous cache agent CA6 receives its own. Delete the mobile node MN from the routing cache table.

As mentioned above, although this invention was demonstrated to the several example, this invention is not limited to a specific Example. Those skilled in the art will understand that various changes and modifications can be made without departing from the scope of the present invention.

As described above, according to the present invention, when the wireless terminal moves to a new network in the mobile IP environment, the time required for handover is reduced through pre-registration, thereby preventing packet loss.

In addition, it is possible to distribute the overhead of the top level router by having the cache agent set the routing cache table and updating the routing cache table only in the corresponding cache agent without having to involve the top router in handover.

1 illustrates a hierarchical structure of a mobile IP network.

2 is a diagram illustrating a structure of a binding update message.

3 is a diagram illustrating a structure of a binding update message to which a pre-registration field defined in the present invention is added.

4 is a diagram illustrating a message delivery flow in a handover process according to the present invention.

5 is a diagram illustrating a message delivery flow in a handover process occurring between different cache agents.

Claims (3)

Transmitting a pre-registration message to the new access router by the mobile node entering the overlapping area of the two access routers; Receiving, by the access router receiving the pre-registration message, a pre-registration message to the higher cache agent; The cache agent receiving the preregistration message checks if the mobile node is already registered in its routing cache table, and if it is not registered, adds a record for that mobile node to its routing cache table and adds the parent cache. Sending a pre-registration message to the agent and, if registered, adding a sub-cache agent or access router that sent the pre-registration message to a record about that mobile node in its routing cache table; Sending a binding update message to the new access router when the mobile node in the overlapping area of the two access routers completely enters the area of the new access router; Sending the binding update message to the parent cache agent by the access router receiving the binding update message; The cache agent receiving the binding update message has its current access router and new access router or current subcache agent and new subcache agent registered in its routing cache table in the record for that mobile node. Delete the router or current child cache agent, and if not, send a binding update message to the parent cache agent. Fast handover method in a mobile IP network comprising a. The fast handover of claim 1, wherein the routing cache table stores a mobile node having packet communication through a corresponding cache agent and a subordinate cache agent or an access router for forwarding packets for the mobile node. Way. The method of claim 1, The pre-registration message is a fast handover method, characterized in that the specific bit of the binding update message is set.