Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1998-09-16
2002-05-14
Olms, Douglas (Department: 2731)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S395400, C370S412000, C370S428000, C370S468000
Reexamination Certificate
active
06388994
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a taffic rate controller in a packet switching network and, more particularly, to an improvement of a traffic rate controller for controlling the traffic rate in a packet switching network by monitoring the data cells transmitted from a transmitting station.
(b) Description of the Related Art
A transmitting station in a packet switching network generally forwards data for transmission from a transmitting node to a receiving node after converting the data for transmission into packet cell data each having a fixed length. A relay node in the packet switching network relays the packet cell data based on the address of the receiving station attached to the packet cell data. In this configuration, the data can be transmitted at the traffic rates based on the respective species of the data transmitted.
On the other hand, with the increase in the amount and diversification of the transmission data, a high-quality processing of the transmission data has been demanded, which highlights the importance of avoidance or cancellation of congestion in the data traffic. A tic rate control in the packet transmission is known as one of the measures for avoiding or canceling the congestion.
A conventional traffic rate control technique in the packet switching network is described hereinafter with reference to an available bit rate (ABR) service technique used in an asynchronous transfer mode (ATM switching system. It should be noted, however, that another traffic rate control technique may be also used in the ATM switching system.
The ABR service technique used in the ATM switching system is recommended in an ATM forum, “Traffic Management Specification”, Version 4.0 R11, March 1961 (hereinafter, referred to as TM4.0). A traffic rate controller implementing the ABR service technique uses an allowed cell rate (ACR) specified at the transmitting node and resource management cells. The traffic rate controller monitors the resource management cells to detect the congestion in the traffic, thereby controlling the traffic rate on the transmitting side by implementing a closed loop control.
FIG. 1
shows a block diagram of a packet switching network implementing a typical traffic rate control technique conformed with TM4.0, which operates based on the ABR service technique, in an ATM switching system. The packet switching network includes a transmitting station
401
, a receiving station
402
and an ATM switching system
403
. The transmitting station
401
is coupled to the receiving station
402
through one of ATM switches
404
distributed in the ATM switching system
403
.
When the transmitting station
401
is to forward data
405
for transmission toward the receiving station
402
, the transmitting station
401
first stores the data
405
temporarily in the transmission buffer
406
, then forwards the stored data in the form of data cells
407
. The data cells
407
are transferred by the ATM switches
404
to the transmitting station
402
based on the address attached to each data cell. The receiving station
402
stores the data cells thus transferred in the receiving buffer
408
and takes out the stored data as effective, received data
409
to complete the data transmission.
In the ABR technique as described above, the data cell
407
is forwarded from the transmitting station
401
together with a forward resource management (FRM) cell
410
attached thereto. The receiving station
402
, after receiving the FRM cell
410
attached to the data cell
407
, sends back the FRM cell as a backward resource management (BRM) cell
411
to the transmitting station
401
.
An explicit rate calculating section
412
calculates an explicit rate (ER) which represents information of congestion in the traffic installed between the transmitting station
401
and the receiving station
402
. ER adding sections
413
and
414
add the explicit rate, supplied from the ER calculating section
412
, to the FRM cell
410
supplied from the transmitting station
401
, and to the BRM cell
411
supplied from the receiving station
402
, when the FRM cell
410
and the BRM cell
411
pass the ATM switches
404
.
The explicit rate thus supplied is the maximum cell rate allowed by the ATM switching system
403
to the transmitting station
401
at that time for the transmission without involving a congestion in the connection effected by the ATM switch
404
. The explicit rate thus includes a congestion information in the connection in the ATM switching system
403
. If the present load on the connection is light, the ATM switching system
403
allows a higher traffic rate to the transmitting station
401
, resulting in a higher explicit rate. On the other hand, if the present load on the connection is heavy, the ATM switching system
403
allows a lower traffic rate to the transmitting station
401
, resulting in a lower explicit rate in the transmitting station
401
.
The allowed cell rate (ACR) as mentioned before is the maximum traffic rate in the transmitting station
401
, whereas the explicit rate is the maximum traffic rate determined by the ATM switching system
403
. The transmitting station
401
controls the transmission rate thereof by the function of the traffic rate controller with reference to the explicit rate attached to the BMR cell by the ATM switch
404
. That is, the transmitting station
401
transmits the data at the transmission rate obtained either by increasing/decreasing the ACR value in the transmitting station
401
based on the received explicit rate or by setting the received explicit rate on the ACR value itself.
The transmitting station
401
also operates for a time-out processing wherein the transmitting station
401
deceases its ACR value in a case other than the congestion in the ATM switching system
403
. This case occurs when FRM cells are not forwarded at a threshold time interval therebetween, which is called ACR decrease time factor (ADTF). The FRM cells are not forwarded at the threshold time interval ADTF in an idle state or a light-load state of the transmitting station
401
, wherein the transmitting station
401
has a smaller number of available data cells for transmission per unit time length.
The threshold ADTF is introduced for the purpose of not applying an excessive sudden load to the network at the restart of the transmission after the transmitting station
401
stays in an idle state, for example, in view that a higher tic rate is not generally required at the restart due to the prior buffering of the data for transmission in the transmission buffer
406
. Immediately after the time-out processing, the transmitting station starts for transmission of data at an initial cell rate (ICR), which is provided in the specification as an initialization of ACR for the operation of the transmitting station
401
.
It is provided in the specification as the condition for the cell transmission that a FRM cell be attached with a fixed number “G” of data cells. That is, if there is only a small number of available data cells for transmission in the transmitting station
401
, the rate of FRM cells is low The transmitting station effects initialization of ACR value at ICR based on the lower rate of FRM cells.
In the conventional traffic rate controller as described above, there is a problem in that the ACR value initialized in the transmitting station lowers the throughput of the traffic, especially in the case of a low-load state of the packet switching network, because the initial traffic rate ICR is extremely low.
There is another problem in the case of an application software specifying that a transmission be conducted at a time interval (jj) which is larger than the specified ADTF time (tt). In this case, even if the time interval is only slightly larger than the ADTF, (for example, even in the case of jj=101 for tt=100), the time-out procedure is conducted without fail to set the ICR on the ACR value, thereby starting the transmission at the low ICR value. Especiall
Hom Shick
NEC Corporation
Olms Douglas
Whitham Curtis & Christofferson, P.C.
LandOfFree
Traffic rate controller in a packet switching network does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Traffic rate controller in a packet switching network, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Traffic rate controller in a packet switching network will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2874130