COMMUNICATION CONNECTING DEVICE
ADAPTIVE TO AN IP NETWORK AND
COMMUNICATION RATE CONTROL
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication connecting device advantageously applicable to a gateway, which connects, e.g., a G3 (Group 3) facsimile apparatus to an IP (Internet Protocol) network, for controlling the transmission rate of packets from a real-time facsimile apparatus or terminal, and a communication rate control method for the same.
2. Description of the Background Art
For facsimile communication using an IP network, a gateway is usually situated between the IP network and an analog facsimile apparatus or communication terminal, e.g., a G3 facsimile apparatus. Serving as an Internet facsimile apparatus, the gateway allows the IP network and G3 facsimile apparatus to surely communicate with each other. A protocol defined by ITU-T (International Telecommunication Union, Telecommunication standardization sector) Recommendation T.30 is assigned to the G3 facsimile apparatus. On the other hand, the Internet facsimile apparatus communicates with a PSTN (Public Switched Telephone Network) in accordance with the above Recommendation T.30 and communicates with the IP network with a protocol defined by ITU-T Recommendation T.38.
Assume that data are sent from one G3 facsimile apparatus (sending apparatus) to another G3 facsimile apparatus (receiving apparatus) via Internet. Then, the sending apparatus first sends a calling tone (CNG) command to the receiving apparatus in accordance with the Recommendation T.30 protocol, requesting the receiving apparatus to return a called station identification (CED) signal. In response, the receiving station sends the CED signal and then sends a digital identification signal (DIS) to the sending apparatus. The DIS signal includes information representative of a communication rate available with the receiving apparatus.
On receiving the DIS signal, the sending apparatus determines a communication rate at which it can communicate with the receiving apparatus. The sending apparatus then sends a digital command signal (DCS) indicative of the determined communication rate to the receiving apparatus. Thereafter, the sending apparatus sends facsimile data to the receiving station.
Assume that the sending apparatus is implemented by a real-time Internet facsimile apparatus. Then, the sending real-time Internet facsimile apparatus also determines a communication rate at which it can communicate with the receiving G3 facsimile apparatus by the above-described procedure. Specifically, the receiving apparatus sends the DIS signal including the communication rate, which is defined by Recommendation T.30, to the sending apparatus. The sending apparatus, however, sends the DSC signal indicative of the communication rate defined by Recommendation T.38 to the receiving apparatus because it is directly connected to the IP network. Specifically, using a traffic capacity of 10 Mbps (megabits per second) or 100 Mbps as a standard, the DCS signal is indicative of a data transmission rate available with 10 BASE, 100 BASE or similar transmission media.
More specifically, a real-time Internet facsimile apparatus is capable of interchanging data even with, e.g., a computer
terminal of the type dealing with electronic mails, Internet telephony, video data and so forth. This is why the abovementioned communication rate is assigned to a real-time Internet facsimile apparatus.
5 As stated above, the communication rate available with the sending real-time Internet facsimile apparatus is far higher than the communication rate of the receiving G3 facsimile apparatus. Stated another way, the sending apparatus and receiving apparatus cannot negotiate with each
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a 15 communication connecting device capable of causing a transmitting terminal, which is connected to an IP network, to conform to the communication rate of an analog receiving terminal, and a communication rate control method for the same.
20 In accordance with the present invention, a communication connecting device includes the function of a sending communication terminal directly connected to an IP network. The communication connecting device controls the communication rate of data to send to a receiving commu
25 nication terminal via the IP network. A data storage stores the data to be sent. Apacketizer divides the data read out of the data storage into packets having a preselected size each. A size information storage stores information representative of the preselected size for providing the packetizer with the
30 information. A rate control circuit counts a preselected period of time after the start of transmission of the packets or a period of time up to the time when a preselected number of packets are fully sent. The rate control circuit then calculates a communication rate on the basis of the period of
35 time, compares the communication rate with a communication rate determined in accordance with a protocol assigned to the receiving communication terminal, and controls the packetizer in accordance with the result of comparison. An interface is connected to the IP network for sending the
40 packets while adjusting them.
Also, in accordance with the present invention, a communication rate control method for the above-described communication connecting device begins with a step of causing the device to send, at a preparatory stage for data
45 transmission, a first signal to the receiving communication terminal. The device then receives an answer signal output from the receiving communication terminal in response to the first signal and determine a communication rate on the basis of a communication rate, which is included in the
50 answer signal and a communication rate defined by a protocol assigned to the receiving communication terminal. Further, the device sends a second signal including the communication rate determined to the receiving communication terminal. Packet size information is provided for
55 dividing data into packets having a preselected size each. The data are read out and then packetized on the basis of the packet size information. A preselected period of time after a start of transmission of the packets or a period of time up to a time when a preselected number of packets are fully sent
60 is counted. A communication rate of the IP network is calculated on the basis of the above period of time, preselected number of packets and preselected packet size. If the communication rate of the IP network is higher than the communication rate included in the second signal, the trans
65 mission of the packets is inhibited. If the former is lower than the latter, a packet send request is generated while control for the transmission of the packets is executed.