Asynchronous transfer mode traffic shapers

Details Asynchronous transfer mode traffic shapers Asynchronous transfer mode traffic shapers

1998-04-14

2001-03-06

Nguyen, Chau (Department: 2663)

Multiplex communications

Data flow congestion prevention or control

Control of data admission to the network

C370S395430, C370S412000

Reexamination Certificate

active

06198723

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to digital data networks. More particularly, the present invention relates to an apparatus and method for improving communication among devices that are coupled to Asynchronous Transfer Mode (ATM) digital data networks.
Asynchronous Transfer Mode is an emerging technology in the fields of telecommunication and computer networking. ATM permits different types of digital information (e.g., computer data, voice, video, and the like) to intermix and transmit over the same physical medium (i.e., copper wires, fiber optics, wireless transmission medium, and the like). ATM works well with data networks, e.g., the Internet, wherein digital data from a plurality of communication devices such as video cameras, telephones, television sets, facsimile machines, computers, printers, and the like, may be exchanged.
To facilitate discussion,
FIG. 1
illustrates a prior art data network
3
, including ATM switches
5
and
10
and a plurality of communication devices
22
-
24
,
32
,
42
-
44
,
52
,
62
-
63
,
72
-
74
and
82
-
85
. ATM switches
5
and
10
may represent a digital switch for coupling, for either bidirectional or unidirectional transmission, two or more of the communication devices together for communication purpose and may represent a data network such as a local area network (LAN), a wide area network (WAN), or the global data network popularly known as the Internet.
Each communication device
22
-
24
,
42
-
44
,
52
,
62
-
63
,
72
-
74
and
82
-
85
can be part of smaller networks
21
,
41
,
51
,
61
,
71
and
81
, and coupled to ATM switch
5
or
10
through input and output ports and physical connections
20
,
40
,
50
,
60
,
70
or
80
. A communication device, such as video server
32
, can also be connected directly to the ATM switch through a physical connection
30
. The smaller networks or the ATM switches may include circuitry to translate data from the communication devices into an ATM data format for transmission via the ATM switches, and to translate ATM data transmitted via the ATM switches into data formats compatible with the communication devices.
Irrespective of the source, data is transformed into an ATM data format prior to being transmitted via an ATM-enabled network. As is well known, a typical ATM data cell
2
includes a header portion and a data portion. Cell header portion may include information regarding the type of information being encapsulated in the ATM data cell, e.g., the destination for that information, and the like. Cell data portion typically includes the information being sent. By standardizing the format of the ATM cells, information from different communication devices may be readily intermixed and transmitted irrespective of its original format.
In the implementation of ATM technology in a data network, the challenge has been to improve the efficiency with which ATM switches
5
and
10
handle multiple simultaneous connections among the multiple communication devices. For peak efficiency, it is generally desirable to have an ATM switch transmit at the highest bandwidth that the network can handle, while at the same time minimizing delay and maximizing data integrity. Unfortunately, the high bandwidth demanded by such a design generally results in a prohibitively expensive ATM switch.
The standards for ATM networks have required that ATM switches be capable of a certain level of quality of service (QoS). For example, the ATM Forum Technical Committee has published a Traffic Management Specification, version 4.0, April 1996, which lays out the specifications for quality of service, which is incorporated herein by reference for all purposes. Some of the criteria of QoS include Peak-to-Peak Cell Delay Variation (peak-to-peak CDV), Maximum Cell Transfer Delay (maxCTD), Cell Loss Rate (CLR), Cell Error Ratio (CER), Severely Errored Cell Block Ratio (SECBR) and Cell Misinsertion Rate (CMR), as well as other characteristics of a connection. Additionally, each connection may be classified as certain types of connections, including constant bit rate, real time variable bit rate, non-real time variable bit rate, unspecified bit rate and available bit rate. Each type of classification requires a certain QoS criteria.
The QoS criteria must be met by all ATM networks and switches. At the same time it is recommended that traffic shaping be performed in order to maximize the efficiency of any given connection. Traffic shaping alters the characteristics of a stream of cells to best fully utilize the capabilities of the connection.
Referring back to
FIG. 1
, a user may wish to use telephone
22
to communicate with telephone
85
. Telephone
22
begins to transmit cells
2
with the appropriate header and body. Among the cells
2
are resource management (RM) cells
2
′ (not shown). Resource cells
2
′ are sent out through the ATM network
3
and is eventually returned to either ATM switch
5
or network
21
, which ever is sending the cells in an ATM format. The resource cell informs the switch, in this case ATM switch
5
, about the characteristics of the connection between telephone
22
and telephone
85
. The connection formed between the telephones
22
and
85
is a virtual circuit (VC) since it is formed from a myriad of potential circuits throughout the vast network and is not a permanent physical connection. The physical pathway, or a logical grouping of virtual circuits, used to form the virtual connection are virtual paths (VP).
The VC from telephone
22
consists partly of network
21
, physical connection
20
and ATM switch
5
. ATM switch
5
and ATM switch
10
are linked through physical connections
12
and
13
. Between these connections
12
and
13
there can be any number of other switches, networks and connections through which the VC is connected. From ATM switch
10
the VC continues through physical connection
80
, network
81
and finally to telephone
85
.
Traffic shaping is desired because the characteristics of the VC should be considered in order to fully utilize the particular VC. For example, telephone
22
may need to communicate with telephone
85
at 64 kbps at a constant bit rate since voice communication is typically constant. Connections
12
and
13
between ATM switches
5
and
10
are typically capable of handling high bandwidth communications in the order of 45 Mbps or more. However, connections
20
and
80
may be more limited. In many cases, connections between a network and an ATM switch may be 1.544 Mbps. Still, 1.544 Mbps is great enough to handle the virtual connection between telephone
22
and telephone
85
. But, one reason for traffic shaping is to fully utilize the 45 Mbps connections
12
and
13
rather than tying up the high bandwidth connections with only the 64 kbps transmissions.
In another example, video server
32
may wish to communicate with television
82
at a non-real time variable bit rate. The video server and connection
30
may be capable of transmitting at up to 30 Mbps. However, connection
80
may be only capable of handling 1.544 Mbps, and cannot handle 30 Mbps communications. Thus, the output of the video server should be shaped to communicate at 1.544 Mbps.
A bottleneck may occur when both telephone
22
and video server
32
are communicating with telephone
85
and television
82
at the same time, respectively. Therefore, traffic shaping is required to ensure that only a maximum of 1.544 Mbps is being transmitted to network
81
, otherwise information may be corrupted or lost, and thus QoS standards not met.
In the prior art, many ATM techniques of traffic shaping have been proposed to efficiently use the ATM network while still meeting QoS criteria. One practice condoned by the ATM forum has been to not utilize any traffic shaping, and simply ensure that QoS criteria have been met. As can be appreciated, this approach while simplistic and less expensive than traffic shaping, fails to properly utilize the full potential of an ATM network.
FIG. 2
is a block diagram of a prior art m

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