System for supporting communications among atm devices, device for supporting data transmission, method for sending data, and computer program product

Abstract

A first communication device receives an ATM cell bound for a second ATM device from a first ATM device via an ATM interface, and then the first communication device sends a data frame including the ATM cell to the second ATM device via wide area Ethernet. In addition, the first communication device sends a synchronization frame to the second ATM device via the wide area Ethernet continuously at a predetermined time interval in accordance with a clock frequency of the first ATM device. A second communication device receives the synchronization frame and measures a clock frequency of the first ATM device in accordance with a time interval of receiving the synchronization frame so as to reproduce a clock having the same frequency as the measured clock frequency. After that, the second communication device sends the clock to the second ATM device via an ATM interface.

1 . A communication device configured to be placed between a first communication network and a second communication network to send data received from the first communication network to the second communication network, the first communication network using a first protocol and the second communication network using a second protocol different from the first protocol, the communication device comprising:
 a receiving portion that receives a data cell from the first communication network;   a conversion portion that converts the data cell to a data frame supporting the second protocol;   a data frame transmission portion that sends the data frame; and   a control frame transmission portion that sends a control frame to the second communication network at a time interval corresponding to a frequency of a clock of the data cell.   
   
   
       2 . A communication device configured to be placed between a first communication network and a second communication network to send data received from the second communication network to the first communication network, the first communication network using a first protocol and the second communication network using a second protocol different from the first protocol, the communication device comprising:
 a receiving portion that receives a data frame from the second communication network;   a conversion portion that converts the data frame to a data cell supporting the first protocol;   a data cell transmission portion that sends the data cell to the first communication network;   a control frame receiving portion that receives, from the second communication network, a control frame sent at a time interval corresponding to a frequency of a first clock;   a clock reproducing portion that reproduces the first clock based on a time interval between when the control frame is received and when the subsequent control frame is received; and   an informing portion that informs the first communication network of the first clock thus reproduced.   
   
   
       3 . The communication device according to  claim 2 , wherein the clock reproducing portion reproduces the first clock based on plural time intervals between when the control frame is received and when the subsequent control frame is received, the first clock having a frequency identical to a frequency of a clock of a party that sends the data frame. 
   
   
       4 . The communication device according to  claim 2 , wherein the clock reproducing portion reproduces the first clock based on data used when the clock having the frequency of the party was reproduced, the first clock having a frequency identical to a frequency of a clock of a party that sends the data frame. 
   
   
       5 . The communication device according to  claim 2 , further comprising
 a transmission side clock characteristics measuring portion that measures characteristics of a second clock based on the time interval between when the control frame is received and when the subsequent control frame is received, the second clock being used for communication of a party that sends the data frame, and   a reproduced clock measuring portion that measures characteristics of the first clock,   wherein the clock reproducing portion reproduces the first clock based on a differential between the latest characteristics measured by the transmission side clock characteristics measuring portion and the latest characteristics measured by the reproduced clock measuring portion.   
   
   
       6 . A communication device configured to be placed between a first communication network and a second communication network to send a data cell received from the first communication network to the second communication network, the first communication network using a first protocol and the second communication network using a second protocol different from the first protocol, the communication device comprising:
 a receiving portion that receives the data cell from the first communication network;   a first conversion portion that converts the data cell to a first data frame supporting the second protocol, and, if there are no cells to be converted, converting an empty cell to the first data frame;   a data frame transmission portion that sends the first data frame to the second communication network; and   a control frame transmission portion that sends a first control frame to the second communication network at a time interval corresponding to a frequency of a first clock of the data cell.   
   
   
       7 . The communication device according to  claim 6 , wherein the first control frame includes a sequence number indicating an issue order of the first control frame. 
   
   
       8 . The communication device according to  claim 6 , wherein operation of the control frame transmission portion takes precedence over operation of the data frame transmission portion. 
   
   
       9 . The communication device according to  claim 6 , further comprising an accumulation portion that accumulates the data cell,
 wherein the data frame transmission portion sends the first data frame to the second communication network based on a control signal for controlling a transmission period.   
   
   
       10 . The communication device according to  claim 6 , wherein the control frame transmission portion changes a time interval between when the first control frame is sent and when the subsequent first control frame is sent based on traffic on the second communication network. 
   
   
       11 . The communication device according to  claim 6 , further comprising
 a data frame receiving portion that receives a second data frame from the second communication network;   a second conversion portion that converts the second data frame to a second data cell supporting the first protocol;   a data cell transmission portion that sends the second data cell to the first communication network;   a control frame receiving portion that receives, from the second communication network, a second control frame sent at a time interval corresponding to a frequency of a second clock;   a clock reproducing portion that reproduces a third clock having a frequency based on a time interval between when the second control frame is received and when the subsequent second control frame is received; and   an informing portion that informs the first communication network of the third clock.   
   
   
       12 . The communication device according to  claim 11 , further comprising
 a time information accumulation portion that accumulates time information on the received second control frame, and   a clear portion that clears the time information when receiving the second control frame is stopped.   
   
   
       13 . The communication device according to  claim 6 , wherein the first communication network is an ATM network and the second communication network is an Ethernet network. 
   
   
       14 . A communication device configured to be placed between a first communication network using a first protocol and a second communication network using a second protocol for use, the communication device comprising:
 a receiving portion that receives a data frame from the first communication network;   a transmission portion that sends data corresponding to the data frame to the second communication network;   a frequency obtaining portion that obtains a frequency of a clock of the data frame when the first protocol is a protocol used to send a data frame at a time interval corresponding to a predetermined clock frequency; and   a control frame transmission portion that sends a control frame to the second communication network at a time interval corresponding to the frequency of the clock obtained by the frequency obtaining portion.   
   
   
       15 . The communication device according to  claim 14 , wherein the data sent by the transmission portion to the second communication network is data conforming to the second protocol.