Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data transfer regulating
Reexamination Certificate
1998-10-05
2001-01-09
Vu, Viet D. (Department: 2758)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data transfer regulating
C709S234000, C709S235000, C709S250000, C370S229000
Reexamination Certificate
active
06173331
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to connection-oriented networks and more specifically to a network node having a first-in-first-out buffer for multiple connections.
2. Description of the Related Art
Japanese Laid-Open Patent Specification Hei-8-274793 describes a connection-oriented communication system which ensures minimum bandwidth for established virtual connections using a plurality of buffers associated respectively with the established connections. Japanese Laid-Open Patent Specification Hei-9-83547 discloses a connection-oriented communication system in which a plurality of buffers are provided to ensure minimum bandwidth for each buffer. However, the use of individual buffers for multiple connections would require a significant number of buffers if a large number of connections must be supported This also results in a significant increase both in complexity and hardware for implementing circuitry for controlling the buffers. In contrast, a single-buffer approach is disclosed in Japanese Laid-Open Patent Specification Hei-7-95209 in which a single buffer is commonly shared by all virtual connections for admission control procedure. In this procedure, the transmission rate of each connection is compared with the contract value of the connection. If the transmission rate of a connection exceeds its contract value, the packets of this connection are discarded. However, if this approach were used in a network node, the output transmission medium of the node cannot be utilized to its maximum efficiency.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a network node for maximum utilization of a transmission medium by sharing a common first-in-first-out buffer among multiple virtual connections while ensuring minimum bandwidth for each connection.
According to a first aspect of the present invention, there is provided a network node comprising a first-in-first-out buffer connected to a transmission medium, detection circuitry for receiving an incoming packet and detecting a virtual connection of the received packet. Control circuitry is provided for calculating a value of delivery instant according to a minimum bandwidth assigned to the detected virtual connection so that vacancy of the transmission medium is reduced to a minimum if the received packet were delivered from the buffer onto the transmission medium at the instant of the calculated value. The calculated value is compared with a decision threshold assigned to the detected virtual connection. The received packet is stored into the buffer if the calculated value is smaller than the decision threshold or discarded if the calculated value is greater than the decision threshold.
According to a second aspect, the present invention provides a network node comprising first and second first-in-first-out buffers connected to a transmission medium, detection circuitry for receiving an incoming packet and detecting a virtual connection and a class of the received packet and control circuitry for calculating a value of delivery instant according to a minimum bandwidth assigned to the detected virtual connection so that vacancy of the transmission medium is reduced to a minimum if the received packet were delivered from either of the buffers onto the transmission medium at the instant of the calculated value, comparing the calculated value with a decision threshold assigned to the detected virtual connection, storing the received packet into one of the buffers depending on the detected class of the packet if the calculated value is smaller than the decision threshold, discarding the received packet if the calculated value is greater than the decision threshold, monitoring storage level of the first buffer and delivering packets from the second buffer onto the transmission medium if the first buffer is vacant and packets from the first buffer onto the transmission medium if the first buffer is not vacant.
According to a third aspect, the present invention provides a network node comprising a first-in-first-out buffer connected to a transmission medium, a memory, and an LSI chip including detection circuitry for receiving an incoming packet and detecting a virtual connection of the received packet, and control circuitry for reading a calculated value of delivery instant of the received packet from the memory, recalculating a value of delivery instant using the value read from the memory according to a minimum bandwidth assigned to the detected virtual connection so that vacancy of the transmission medium is reduced to a minimum if the received packet were delivered from the buffer onto the transmission medium at the instant of the recalculated value, comparing the recalculated value with a decision threshold assigned to the detected virtual connection, storing the received packet into the buffer if the recalculated value is smaller than the decision threshold, discarding the received packet and resetting the recalculated value to the read value if the recalculated value is greater than the decision threshold, and storing both of the recalculated and reset values of delivery instant into the memory.
According a fourth aspect, the present invention provides a method of controlling packets, comprising the steps of:
a) receiving a packer of a particular virtual connection or a packet of other virtual connection, detecting a time interval between a previous packet and the received packet, and setting an arrival time value V of every packet to a previous variable plus the detected time interval;
b) setting an arrival time value R of the packet of the particular virtual connection to the arrival time value V;
c) updating the previous variable with a minimum bandwidth value assigned to the particular virtual connection, the arrival time values V and R and a previous delivery time value F of the packet of the particular virtual connection;
d) updating the previous delivery time value F with the minimum bandwidth value and the arrival time value V;
e) comparing the updated delivery time value F with a decision threshold which is equal to the arrival time value V plus a threshold value assigned to the particular virtual connection;
f) storing the packet of the particular virtual connection into a first-in-first-out buffer if the updated delivery time value F is smaller than the decision threshold and resetting the updated delivery time value F to the previous delivery time value and discarding the packet of the particular virtual connection if the updated delivery time value F is greater than the decision threshold; and
g) repeating the steps (a) to (f)
According to a fifth aspect, the present invention provides a method of controlling packets, comprising the steps of:
a) setting an arrival time value V equal to a previous variable plus unity and updating the previous variable with a time interval T which is an integral multiple of a minimum interval between successive packets of any virtual connection;
b) receiving a packet of a particular virtual connection or a packet of other virtual connection and comparing the arrival time value V with a previous arrival time value R of the packet of the particular virtual connection;
c) if the arrival time value V is not equal to the previous arrival time value R, updating the previous variable with a previous delivery time value F of the packet of the particular virtual connection, the arrival time value V weighted by a coefficient assigned to the particular virtual connection and the previous arrival time value R weighted by the coefficient, and setting a current arrival time R of the packet of the particular virtual connection to the arrival time value V;
d) updating the previous delivery time value F with the weighted arrival time value V;
e) if the arrival time V is equal to the previous arrival time value R, repeating the step (d);
f) comparing the updated delivery time value F with a decision threshold which is equal to the weighted arrival time value V plus a threshold value assigned to the pa
NEC Corporation
Scully Scott Murphy & Presser
Vu Viet D.
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