Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-02-24
2001-05-29
Olms, Douglas (Department: 2732)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S328000, C370S401000
Reexamination Certificate
active
06240089
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of multicasting for a mobile host which is used in a network including a plurality of sub-networks connected to one another.
A network includes a plurality of sub-networks which are connected to one another and serves multicast service that a multicast packet is delivered from an originator to a set of destinations. A scope of the multicast transmission is limited by the originator on the basis of a physical network topology to form a multicast group.
The sub-networks have nodes called agents to accept a mobile host in the network and to assist the mobile host. The mobile host is related to one of the agents, this relationship determines the mobile host's home agent. The mobile host has a specific identifier called a home address which is used by the home agent to manage the mobile host.
In a conventional multicasting method, the mobile host is permitted to participate in the multicast group when the home agent is located in the scope.
However, this method has a defect that the mobile host located in the scope is not permitted to participate in the multicast group when the home agent is located outside scope. Moreover, the method has another defect that the originator can not exclude the mobile host located outside the scope from the multicast group when the home agent is located in the scope.
In another conventional multicasting method, the mobile host is permitted to participate in the multicast group when it is located in the scope.
However, this method has a defect that the mobile host located outside the scope is not permitted to participate in the multicast group though the home agent is located in the scope. Moreover, the method has another defect that the originator can not exclude the mobile host located in the scope from the multicast group even though the home agent is located outside the scope.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a multicasting method capable of forming various multicast groups having different characteristics.
It is another object of this invention to provide a multicasting system which adopts a multicasting method of the type described.
Other objects of this invention will become clear as the description proceeds.
On describing the gist of this invention, it is possible to understand that a method multicasting a multicast packet from an originator to destinations belonging to a multicast group is formed in a network by the originator. The network includes a plurality of sub-networks which are connected to one another and which include hosts and nodes. The sub-networks accept a mobile host by the use of the nodes. One of the nodes is related to the mobile host and is called a home agent. Any one of the hosts becomes the originator to form the multicast group. The destinations are all of the hosts which belong to the multicast group except the originator.
According to a gist of this invention, there is provided a method of multicasting comprising the steps of selecting at least one from the sub-networks to decide a scope of the multicast group at the originator and multicasting a group characteristic information including a specific group identifier from the originator to the scope before multicasting the multicast packet.
The method further comprises the steps of receiving said group characteristic information at said mobile host, and judging at said mobile host whether or not it is admitted said mobile host to participate said multicast group on the basis of said group characteristic information.
In the method, the group characteristic information is directly sent from originator.
The group characteristic information includes a member restriction/unrestriction attribute which shows whether or not the originator demands that the home agent is located in the scope.
The mobile host has a direct participation group table. The method further comprises the step of registering the specific group identifier into the direct participation group table when the member restriction/unrestriction attribute shows that the originator does not demand that the home agent is located in the scope.
The method further comprises the steps of inquiring of the home agent about whether or not the home agent is located in the scope from the mobile host when the mobile host receives the group characteristic information and the member restriction/unrestriction attribute shows that the originator demands that the home agent is located in the scope, and replying from said home agent to said mobile host whether or not said home agent is located in said scope.
The mobile host has a direct participation group table. The method further comprises the step of registering the specific group identifier into the direct participation group table when the home agent replies to the mobile host that the home agent is located in the scope.
The mobile host has a nonparticipation group table. The method further comprises the steps of registering the specific group identifier into the nonparticipation group table when the home agent replies to the mobile host that the home agent is not located in the scope.
In the method, the group characteristic information includes a transfer approval/disapproval attribute which shows whether or not it is approved to transfer the group characteristic information to the mobile host located out of the scope by the originator. The method further comprises the step of transferring the group characteristic information as a transferred group characteristic information to the mobile host when the transfer approval/disapproval attribute shows that it is approved to transfer the group characteristic information to the mobile host located out of the scope.
The home agent has a group characteristic table. The method further comprises the step of registering the specific group identifier into the group characteristic table when the home agent receives the group characteristic information and the group identifier is not registered in the group characteristic table.
The method further comprising the step of inquiring of the mobile host about whether or not the mobile host receives the group characteristic information identified by the specific group identifier when the transfer approval/disapproval attribute shows that it is approved to transfer the group characteristic information to the mobile host located out of the scope before the transferring step.
The home agent having a group characteristic transfer table shows whether or not it is necessary to transfer the group characteristic information to the mobile host, wherein the method further comprising the steps of registering a transfer unnecessary flag into the group characteristic transfer table when the mobile host replies to the home agent that it is unnecessary to transfer the group characteristic information to the mobile host, and registering a transfer necessary flag into the group characteristic transfer table when the mobile host replies to the home agent that it is necessary to transfer the group characteristic information to the mobile host.
The method comprises the step of referring to the group characteristic transfer table to carry out the transferring step.
The method further comprises the steps of changing the transfer necessary flag registered in the group characteristic transfer table into the transfer unnecessary flag when the home agent receives a transfer unnecessary message which shows that it is unnecessary to transfer the group characteristic information to the mobile host from said mobile host.
The method further comprises the steps of receiving the transferred group characteristic information at the mobile host, and judging whether or not the mobile host participate the multicast group on the basis of the transferred group characteristic information.
The mobile host has a transfer participate group table. The method further comprises the steps of judging whether or not the mobile host receives the group characteristic information having the specific group identifier from the origina
Okanoue Kazuhiro
Osawa Tomoki
NEC Corporation
Olms Douglas
Scully Scott Murphy & Presser
Vanderpuye Kenneth
LandOfFree
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