1. Field of the Invention
The invention relates to a communication system and, more particularly, to a system for transmitting and receiving data in a real-time manner by using the internet.
2. Description of the Related Art
The internet based on TCP/IP is rapidly being spread. The worldwide information communication system such as WWW (World Wide Web) further promotes the spread of the internet. It becomes a common sense that multimedia data including audio and video data is transmitted on the internet. In association with it, a protocol such as RSVP (Resource reSerVation Protocol) or ST-11 to reserve a bandwidth has also been proposed. The RSVP has been disclosed in xe2x80x9cRSVP: A New Resource ReSerVation Protocolxe2x80x9d, (IEEE Network 93/9, p. 8) and xe2x80x9cResource ReSerVation Protocol (RSVP), Ver. 1, Functional Specificationxe2x80x9d, (""97/9). By the bandwidth reservation, a data communication at a rate corresponding to the reserved bandwidth is guaranteed without being influenced by the other traffic.
Under such a background, a communication system called an internet telephone such that a communication terminal is connected to the internet, audio data is transmitted or received in a real-time manner, and a communication similar to a telephone is provided is being spread. A motion to unify a communication onto the internet is becoming active. Particularly, attention is paid to an internet telephone of the type such that the user accesses from a general telephone to an access point in the internet, the internet is used for an interval from the access point to an access point near a partner whom the user wants to call, and the other access point calls a partner telephone using a public telephone network. Thus, for example, now assuming that access points are located in Tokyo and Osaka, if the telephone user calls from Tokyo to Osaka by internet telephone, he pays both of a telephone charge from his telephone to the access point in Tokyo and a telephone charge from the access point in Osaka to a partner""s telephone, so that he can call from Tokyo to Osaka cheaper than the case of the telephone communication using the public telephone network. Particularly, such an advantage remarkably appears in case of the international telephone. It is known that the total telephone charge is equal to or less than about {fraction (1/10)}of the present international telephone charge. The internet telephone has also been disclosed in xe2x80x9cReal-Time Voice Over Packetxe2x80x94Switched Networks (""98/2)xe2x80x9d. It is demanded that the internet telephone conforms with ITU (International Telecommunication Union)xe2x80x94T Recommendation H.323.
In the conventional communication system disclosed in the above literatures, when a plurality of access points have been established, no consideration is taken with respect to whether the selected access points (gateway: GW) provide the minimum costs or an enough bandwidth can be obtained between those access points. In a communication using the selected access points, there is also a problem such that an actual telephone charge which is required for the communication cannot be known when the system is used but can be known only after a debit or the like of such a communication is sent to the user.
It is an object of the invention to realize a real-time performance of a communication by assuring a necessary bandwidth onto a communication path in case of performing the communication through the internet.
Another object of the invention is to manage costs for communication, select a communication route of the minimum costs, and inform the user of a charge.
A communication system according to the invention comprises: an internet; a telephone network; a plurality of GW(Gateway)s which are connected to the internet and the telephone network; and a routing server which is connected to the internet. Each of the GWs accepts an internet relay request of a communication and a destination telephone number from a telephone.
The routing server has a GW location table for registering a set of each GW and a telephone number of an area where each GW takes charge in a relay and a bandwidth reservation information storage table for managing all of the bandwidths which the GWs have and the reservation bandwidth. The routing server receives the destination telephone number and the reservation bandwidth from the source GW, selects a GW which can cover the telephone number at the minimum costs and can reserve the bandwidth with reference to the table, and notifies the source GW of the selected GW. The source GW establishes a connection to the notified GW while making the bandwidth reservation and executes a data relay. A fact that the bandwidth has been reserved is notified from the destination GW to the routing server. The routing server updates information in the bandwidth reservation information storage table.