Electrical computers and digital processing systems: multicomput – Computer-to-computer session/connection establishing – Session/connection parameter setting
Reexamination Certificate
1999-07-28
2003-05-20
Sheikh, Ayaz (Department: 2155)
Electrical computers and digital processing systems: multicomput
Computer-to-computer session/connection establishing
Session/connection parameter setting
C709S203000, C709S231000, C709S223000, C709S238000, C709S245000, C709S220000, C370S312000, C370S388000, C370S390000
Reexamination Certificate
active
06567851
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to multicast-session-control devices used in a network which is comprised of servers for transmitting flow of data such as multimedia data, clients for receiving a multicast data flow, and network-transit devices such as routers adapted for multicast transmission. Such multicast-session-control devices are used for controlling allocation of multicast addresses, for example.
In recent years, intra-organization information-system networks (intranets) have become widely used due to a significant market progress of personal computers, and, also, networks which connect computers together have been experiencing a significant enhancement in their functions and performance.
As use of intranets and the Internet increases, transmission of multimedia data such as moving pictures and audio data is increased. Against this background, there is a demand for technologies that make possible an efficient transfer of large size data. In order to achieve this objective, efficient use of multicast transmission is regarded as a viable solution.
The present invention particularly relates to a multicast-session-control device used in a network such as an intranet for the purpose of achieving an efficient multicast transmission where the network is equipped with multicast-adapted network elements that permit use of multicast transmission.
2. Description of the Related Art
A multicast technology makes it possible to transmit data to a group of communication devices selected from communication devices connected to a network such as the Internet or an intranet. Multicast is different from broadcast which transmits data to all the communication devices connected to the network in that multicast transmits data only to a selected group of communication devices.
In the following, a description will be given with regard to a multicast technology that employs an IP multicast based on internet protocols, and is implemented via the Ethernet serving as transfer media.
IP multicast uses IP multicast addresses which are defined by an address system that is called a class D in the IP address system. By attaching an IP multicast address to transmission data, the IP multicast attends to simultaneous transmission directed to a plurality of destinations.
FIGS. 7A through 7C
are illustrative drawings for explaining multicast addresses.
FIG. 7A
shows a class-D IP-address system, and
FIG. 7B
shows allocation of IP multicast addresses.
FIG. 7C
demonstrates a multicast physical address used in the Ethernet.
As shown in
FIG. 7A
, a class-D IP address is an IP address that has four upper bits thereof set to “1110”. These four upper bits are used for identifying a given address as an IP multicast address. The remaining bits of the IP multicast address are used for indicating a multicast group.
The class-D IP address covers an address range from 224.0.0.0 to 239.255.255.255 based on decimal representation. Some IP multicast addresses within this range are reserved for special use.
As shown in
FIG. 7B
, an IP address of 224.0.0.0 is reserved, and is not assignable, and IP addresses from 224.0.0.1 to 224.0.0.255 are assigned for routing-protocol purposes. Further, IP addresses from 224.0.1.0 to 238.255.255.255 are assigned for public media services.
Only the remaining IP addresses from 239.0.0.0 to 239.255.255.255 are available for local sites, and can be used as addresses for intranets or the like.
Conversion from an IP multicast address to a multicast physical address is defined in the Request For Comments 1700, which is published by IETF (Internet Engineering Task Force) that sets forth internet standards.
According to this definition, conversion from a class-D IP address to a physical address is performed by inserting 23 lower bits of the class-D IP address into 23 lower bits of a multicast physical address “01.00.5E.00.00.00(HEX)”.
For example, an IP multicast address “239.133.130.34” is converted into a multicast physical address “01:00:5E:05:82:22(HEX)”.
When multimedia data or the like is to be transmitted as multicast, a server for multicast transmission selects a usable IP multicast address, and transmits data after attaching the selected IP multicast address to the data flow. In the field of this technological art, however, there is no established procedure or method for selecting an IP multicast address.
Namely, an IP multicast address to be used is either arbitrarily selected by each server or determined by a server administrator or the like after the server administrator inquires a network administrator about usable IP multicast addresses. Here, the network administrator is in charge of assignment of IP multicast addresses.
Further, a client for receiving multimedia data via multicast transmission needs to register in multicast-adapted network-transit devices (i.g., routers) in order to arrange receipt of transmitted multimedia data. To achieve this, a client needs to report an IP multicast address of multimedia data that the client wishes to receive.
Namely, a client has to register an IP multicast address of desired multimedia data so as to join a corresponding IP-multicast group. Information about what multimedia data are available at what IP multicast addresses is announced to a client via E-mail or by posting the information on an electronic bulletin board. Such arrangement for informing clients is made by a server administrator through a manual procedure.
As described above, there is no established procedure for automatically assigning a usable multicast address to a multicast data flow without making duplicate use of the same multicast address. This makes it troublesome to select a usable multicast address, and may end up using the same multicast address for different multicast transmissions.
In order to avoid duplicate use of the same multicast address in a network comprised of a plurality of servers, a multicast address used by a given server needs to be announced to all the other servers that may conduct multicast transmission of their own. Such a process leads to an increase of a data processing burden on the servers and an increase in the traffic load on the network.
Further, since guide information about the multicast multimedia data and/or the introduction thereof need to be announced via E-mail or electronic bulletin boards by server administrators thorough a manual procedure, a process of announcement takes time and labor. In this manner, handling of multimedia-data transmission via a multicast operation is quite burdensome.
Inconvenience in multicast-session management such as allocation of multicast addresses as described above has been one of the factors that prevent the multicast transmission technology to be widely used despite the fact that the multicast technology is effective in transmitting large-size multimedia data such as moving pictures to a large number of clients.
Accordingly, there is a need for a multicast-session-management device which can select a usable multicast address while avoiding duplicate use of the same address as that used by another server so as to achieve easier multicast-session management, and can allow easier use of multicast services by transmitting to clients guide information about multimedia data such as moving pictures and audio data.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a multicast-session management device which can satisfy the need described above.
It is another and more specific object of the present invention to provide a multicast-session-management device which can select a usable multicast address while avoiding duplicate use of the same address as that used by another server so as to achieve easier multicast-session management, and can allow easier use of multicast services by transmitting to clients guide information about multimedia data such as moving pictures and audio data.
In order to achieve the above objects according to the present invention, a device for multicast-session management
Nguyen Thu Ha
Sheikh Ayaz
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