Patent ID: 6438107
Filing Date: 2002-08-20
Classification: H04L,H04Q

Abstract:
A cell transfer rate control apparatus, comprising:a plurality of quality class buffers QCP(i) provided for each quality class i (i=1, 2, . . . , n) to guarantee communications quality declared by a user; congestion determination means for determining whether a quality class buffer QCP(i) is in a congestion state or in a non-congestion state based on a predetermined first threshold set in the quality class buffer QCP(i); input rate observation means for observing an input cell rate (BWI_QCP(i)) of each quality class buffer QCP(i), and an input cell rate (BWI_ALL) of a link accommodating the quality class buffer QCP(i) in each predetermined observation period; first load factor computation means for computing, depending on a determination result from said congestion determination means, a load factor (OLF1_QCP(i)) of the quality class buffer QCP(i) in the non-congestion state based on OLF1_QCP(i)=BWI_QCP(i)/BWO1_QCP(i), which is a ratio of the BWI_QCP(i) of the quality class buffer QCP(i) observed by said input rate observation means to a target output band (BWO1_QCP(i)) in the non-congestion state predetermined for the quality class buffer QCP(i), when the quality class buffer QCP(i) is in the non-congestion state, and for computing a load factor (OLF2_QCP(i)) of the quality class buffer QCP(i) in the congestion state based on OLF2_QCP(i)=BWI_QCP(i)/BWO2_QCP(i), which is an input cell rate (BWI_QCP(i)) of the quality class buffer QCP(i) observed by said input rate observation means to a target output band (BWO2_QCP(i)) in the congestion state predetermined for the quality class buffer QCP(i) when the quality class buffer QCP(i) is in the congestion state; second load factor computation means for computing, depending on a determination result from said congestion determination means, a load factor (OLF1_ALL) of a link accommodating the quality class buffer QCP(i) in the non-congestion state based on OLF1_ALL=BWI_ALL/BWO1_ALL, which is a ratio of an input cell rate (BWI_ALL) of a link observed by said input rate observation means to a target output band (BWO1_ALL) in the non-congestion state predetermined for the link, when the quality class buffer QCP(i) is in the non-congestion state, and for computing a load factor (OLF2_ALL) of the link in the congestion state based on OLF2_ALL=BWI_ALL/BWO2_ALL, which is an input cell rate (BWI_ALL) of the link observed by said input rate observation means to a target output band (BWO2_ALL) in the congestion state predetermined for the link when the quality class buffer QCP(i) is in the congestion state; average cell rate computation means for computing, when a forward RM cell arrives, a new average value (MACR_QCP(i)_NEW) of a CCR of the quality class buffer QCP(i) using CCR_QCP(i) and MACR_QCP(i)_OLD when the quality class buffer QCP(i) E is in the congestion state, and a CCR value (CCR_QCP(i)) set in a CCR field of the forward RM cell is smaller than the MACR_QCP(i)_OLD, which is an average value of the CCR computed through a predetermined algorithm set in the CCR field of the forward RM cell which previously arrived at the above described quality class buffer QCP(i), or when the quality class buffer QCP(i) is in the non-congestion state, and the CCR value set in the CCR field of the forward RM cell is larger than the MACR_QCP(i)_OLD, and also for computing a new average value (MACR_QCP(i)_NEW) of the CCR of the link accommodating the above described quality class buffer QCP(i) based on the CCR value (CCR_ALL) set in the CCR field of the forward RM cell which arrives at the link, and the MACR_ALL_OLD, which is an average value of the CCR computed through a predetermined algorithm set in the CCR field of the forward RM cell which previously arrived at the link; and ER computation means for setting a first explicit cell rate (ER1) to a value obtained by dividing the MACR_QCP(i)_NEW obtained by said average cell rate computation means by the OLF1_QCP(i) obtained by said first load factor computation means, or to a value obtained by dividing the MACR_ALL_NEW obtained by said average cell rate computation means by the OLF_ALL obtained by said second load factor computation means whichever is larger when the quality class buffer QCP(i) is in the non-congestion state, for setting, when the quality class buffer QCP(i) is in the congestion state, a first explicit cell rate (ER1) to a value obtained by dividing the MACR_QCP(i)_NEW obtained by said average cell rate computation means by the OLF2_QCP(i) obtained by said first load factor computation means, or to a value obtained by dividing the MACR_ALL_NEW obtained by said average cell rate computation mens by the OLF_ALL obtained by said second load factor computation means whichever is larger when the quality class buffer QCP(i) is in the non-congestion state, and for setting, depending on a determination result of said congestion determination means, a second explicit cell rate (ER2) to the first explicit cell rate (ER1) or a minimum cell rate set in a connection of the quality class buffer QCP(i), whichever is larger.