Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-03-31
2001-01-16
Ngo, Ricky (Department: 2731)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S463000, C370S477000
Reexamination Certificate
active
06175572
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a bandwidth allocation method; and, more particularly, to a hierarchical bandwidth allocation method by using sub-tables in an ATM network interface card.
DESCRIPTION OF THE PRIOR ART
An ATM (Asynchronous Transfer Mode) communication network is implemented by using hierarchical protocols so as to support a various kinds of services. While the conventional public telephone network and packet switching network are exclusive networks for providing a voice service and data service, respectively, the ATM network is constructed to provide a voice service, a data service, a video service and so on, as an integrated network.
In order to provide the various kinds of services, the ATM network statistically multiplexes and transmits information in unit of a limited size, i.e., packets or cells through virtual channels. To each of the virtual channels, a bandwidth is allocated by using a bandwidth allocation table in a control memory of an ATM network interface card.
Referring to
FIG. 1
, there is provided a block diagram of a host system
10
and an ATM network interface card
20
. The host system
10
includes a host memory
11
, a processor
12
and bus controller
13
and is connected with the ATM network interface card
20
through an I/O(Input/Output) bus
30
. At the processor
12
of the host system
10
, application programs for use in providing users with services are executed and a network interface card driver(not shown) for use in providing ATM communication capability is implemented therein. The network interface card driver sets up various kinds of tables and rings associated with ATM communication and updates data of the tables in response to a request of the application programs.
The ATM network interface card
20
is directly controlled by the network interface card driver; divides packets to be transmitted into ATM cells and transmits the ATM cells to the ATM network in response to a request of an application program; and forms packets by reassembling received ATM cells and delivers the packets to the application program.
As is shown in
FIG. 1
, the ATM network interface card
20
includes an AAL(ATM Adaptation Layer) processor
21
, a SONET(Synchronous Optical NETwork)/ATM line adapter
22
, a transceiver
23
, an EPROM
24
and a control memory
25
. The AAL processor
21
is connected to the control memory
25
via a 32 bit local memory bus
27
and to the EPROM
24
via an 8 bit local slave bus
26
. The EPROM
24
is also connected to the SONET/ATM line adapter
22
via the local slave bus
26
. Further, the AAL processor
21
can directly access the host memory
11
in the host system
10
via the I/O bus
30
and read from the control memory
25
and write data thereon. The processor
12
in the host system
10
can also read from the control memory
25
and write data thereon by directly accessing it via the I/O bus
30
.
When an application program applied at the host system
10
requests a service associated with ATM, the network interface card driver of the host system
10
provides the service to the application program. For example, if an application program stores certain message data in the host memory
11
and requests the host system
10
to transmit the message data, the network interface card driver requests, via the I/O bus
30
, the AAL processor
21
to transmit the message data.
The AAL processor
21
reads the message data stored in the host memory
11
in a fixed length unit, for example, 48-byte; forms ATM cells according to an AAL protocol format; and delivers the ATM cells to the SONET/ATM line adapter
22
. The SONET/ATM line adapter
22
maps the ATM cells into a predetermined format suitable for optical transmission and the transceiver
23
converts the formatted serial data into an optical signal and transmits it to the ATM network.
Meanwhile, data received by the transceiver
23
from the ATM network is divided into ATM cells and then inputted to the AAL processor
21
via the SONET/ATM line adapter
22
. The AAL processor
21
separates headers and payloads from the ATM cells; restores a message by reassembling the payloads; notifies the host system
10
of the completion of reassembling the message by using interrupt. When the interrupt notifying the completion of reassembling the message is received from the AAL processor
21
is, the network interface card driver of the host system
10
transmits the received message to the application program according to a predetermined procedure.
At the bandwidth allocation table of the control memory
25
, indices designating virtual channels assigned for transmitting or ATM cells are stored at entries thereof, thereby allowing a bandwidth to be allocated to each virtual channel. When the size of the bandwidth allocation table, i.e., the number of entries constituting the bandwidth allocation table, and a transmission rate or a bandwidth of a physical link are determined, a transmission rate for one entry of the bandwidth allocation table maybe calculated as:
C
v
=V/N
(bps) Eq. (1)
wherein C
v
is the transmission rate for one entry of the bandwidth allocation table; V is an overall transmission rate of the physical link; and N is the number of entries constituting the bandwidth allocation table, the physical link representing the virtual channels designated by the entries of the bandwidth allocation table.
For instance, if the transmission rate of a physical link is 100 Mbps and the number of the entries constituting the bandwidth allocation table is 100, the transmission rate for one entry of the bandwidth allocation table is 1 Mbps.
A bandwidth is allocated to a virtual channel depending on the frequency of the index of the virtual channel recorded at the entries of the bandwidth allocation table. If the transmission rate of one entry of the bandwidth allocation table is 1 Mbps and a required bandwidth of a virtual channel is 4.5 Mbps, the index indicating the virtual channel is recorded at 5 entries of the bandwidth allocation table.
FIG. 2
represents an exemplary bandwidth allocation table, wherein indices of virtual channels are recorded at entries constituting the bandwidth allocation table, each of the indices being of 8 bits representing one of the virtual channels
0
-
255
.
The AAL processor
21
sequentially accesses the entries of the bandwidth table and transmits data through the virtual channels indicated by indices recorded at entries of the bandwidth allocation table.
In the conventional bandwidth allocation scheme described above, a significant loss of bandwidth may be incurred if the bandwidth for one entry is large. For instance, if the bandwidth of a channel
1
is 1.5 Mbps, the bandwidth of a channel
2
is 64 Kbps and the bandwidth of one entry of the bandwidth allocation table is 1 Mbps, the index of the channel
1
is recorded at 2 entries and the index of the channel
2
is recorded at 1 entry. The bandwidth loss for this case is 0.5 Mbps for the channel
1
and 936 Kbps for the channel
2
, respectively.
Accordingly, it is necessary to reduce the bandwidth of each entry of the bandwidth allocation table by increasing the number of entries constituting the bandwidth allocation table. However, the reduction of the allocated bandwidth for each entry of the table by a certain degree results in the number of entries increased by the identical degree, causing the operational inefficiency due the increased number of entries.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the invention to provide a method for efficiently allocating a bandwidth to a virtual channel by using sub-tables.
In accordance with an aspect of the present invention is to provide a method f or allocating bandwidths to virtual channels by using a bandwidth allocation table in an ATM network, wherein the bandwidth allocation table is divided into a multiplicity of entries and each of the entries has a plurality of hierarchically structured sub-tables, comprising the steps of: (a) checking a flag of an entry of the
Anderson Kill & Olick PC
Daewoo Electronics Co. Ltd.
Ngo Ricky
LandOfFree
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