Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1998-07-02
2001-11-27
Vu, Huy D. (Department: 2733)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S395430
Reexamination Certificate
active
06324166
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a call setup control apparatus equipped in an ATM (Asynchronous Transfer Mode) switch capable of providing a plurality of services with different QoS (Quality of Service) requirements.
DESCRIPTION OF THE RELATED ART
In ATM networks, priority control and CAC (Call Admission Control) are indispensable traffic management methods to guarantee QOS requirements for different types of traffic, such as voice, video and data. In addition, recent various demands for communication make difficult to previously calculate required bandwidths in the networks which will satisfy the QoS requirements by estimating cell traffic characteristics of the ATM connections of each type in each priority class.
In order to flexibly respond to the various demands for communication and to effectively utilize network resource, it is necessary to correctly grasp the amount of current resource depending upon connection state for calls and to evaluate whether a fresh call is acceptable or not. However, according to the conventional priority control method, influences of higher priority calls over QoS requirements of lower priority calls are not sufficiently considered for providing a plurality of services with the different QOS requirements. Thus, it is impossible to precisely estimate current bandwidth and required bandwidth for accepting a fresh call.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a call setup control apparatus equipped in an ATM switch, whereby the amount of bandwidth occupied by a plurality of calls with different QoS requirements can be correctly grasped and whether a fresh call is acceptable or not can be suitably evaluated.
The present invention concerns a call setup control apparatus, equipped in an ATM switch with a plurality of buffers for respective priority classes of calls, for providing priority control of calls of a plurality of types with different quality of service requirements. Particularly, according to the present invention, the apparatus has a first calculation unit for calculating an objective value of cell loss ratio P
B
(u) of a buffer B
u
in priority class u which is equal to or lower than a priority class k (u=k to K), based upon parameters of an average cell rate R(k,j), an objective value of cell loss ratio Q(k,j), and the number of calls N(k,j) for calls of each type j (j=1 to J
k
) in each class k (=1 to K), with considering a cell rate of calls in priority class which is higher than the class k (class 1 to k−1), when a fresh call is arrived, a unit for obtaining a bandwidth &agr;(k,u,j) required for calls of type j in class k in the buffer B
u
to make a cell loss ratio in the buffer B
u
to be equal to or less than the objective value P
B
(u), a second calculation unit for calculating a required bandwidth C(u) for the buffer B
u
, based upon the obtained bandwidth &agr;(k,u,j), and a unit for judging whether the fresh call is acceptable or not by comparing the calculated bandwidth C(u) with a link capacity C
p
.
It is preferred that the first calculation unit includes a third calculation unit for calculating a summation S(k) of the average cell rates R(k,j) of all types 1 to J
k
(j=1 to J
k
) class k (k=1 to K), based upon the parameters of the average cell rates R(k,j) and the number of calls N(k,j), and a determination unit for determining an objective value of cell loss ratio P
Q
(k) for calls in the class k to one with the minimum value among the objective value of cell loss ratio Q(k,j) of the type j in the class k, and wherein the objective value of cell loss ratio P
B
(u) of class k buffer is calculated in accordance with the summation S(k) of the average cell rates and the objective value of cell loss ratio P
Q
(k) for calls in the class k.
The summation S(k) of the average cell rates may be calculated from
S
(
k
)
=
∑
j
=
1
J
k
N
(
k
,
j
)
R
(
k
,
j
)
.
Equation (2)
The objective value of cell loss ratio P
Q
(k) for calls in the class k may be calculated from
P
Q
(
k
)
=
min
j
{
Q
(
k
,
j
)
}
.
Equation (1)
The objective value of cell loss ratio P
B
(u) may be calculated from
P
B
(
u
)
=
S
(
u
)
∑
i
=
1
u
S
(
i
)
P
Q
(
u
)
[
u
=
k
,
…
,
K
]
.
Equation (3)
The required bandwidth C(u) for the buffer B
u
may be calculated from
C
(
u
)
=
∑
i
=
1
u
∑
j
=
1
J
i
N
(
i
,
j
)
α
(
i
,
u
,
j
)
.
Equation (4)
It is also preferred that the apparatus further has control parameter tables for storing the average cell rate R(k,j), the objective value of cell loss ratio Q(k,j), and the number of calls N(k,j) for calls of each type j in each class k, the objective value of cell loss ratio P
Q
(k) for calls in the class k, the summation S(k) of the average cell rates R(k,j) in all classes, the objective value of cell loss ratio P
B
(u) of the buffer B
u
, the bandwidth &agr;(k,u,j) required for calls of type j in class k in the buffer B
u
, and the required bandwidth C(u) for the buffer B
u
.
The call setup control apparatus of the present invention calculates a required bandwidth for satisfying QoS requirements with respect to calls under priority control by using an effective bandwidth method described in for example F. P. Kelly, “Effective bandwidth at multi-class queues”, Queuing Syst.
9
, pp.5-15, 1991 so as to enable an optimum call acceptance check for an arbitrary combination of priority of calls, call type and the number of calls in progress.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.
REFERENCES:
patent: 5280483 (1994-01-01), Kamoi et al.
patent: 5583857 (1996-12-01), Soumiya et al.
patent: 5745478 (1998-04-01), Van Der Wal
patent: 5872771 (1999-02-01), Park et al.
“Effective Bandwidths at Multi-Class Queues”, Kelly,Queueing Systems, 9, 1991, pp. 5-15.
Nakamura Hajime
Yokoyama Hiroyuki
Arent Fox Kintner & Plotkin & Kahn, PLLC
Kokusai Denshin Denwa Co. Ltd.
Vu Huy D.
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