Multiplex communications – Diagnostic testing – Determination of communication parameters
Reexamination Certificate
1998-11-10
2003-10-07
Jung, Min (Department: 2663)
Multiplex communications
Diagnostic testing
Determination of communication parameters
C370S468000
Reexamination Certificate
active
06631118
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to computer networks. In particular, the present invention relates to adjusting connection speed dynamically to provide desired bandwidth.
BACKGROUND OF THE INVENTION
The ability to request bandwidth on demand cost effectively has been an area of study for several years. Services like ATM (asynchronous-transfer-mode) SVC (switch-virtual-circuit) allow customers to buy bandwidth at fixed bandwidth increments. With these services, users can purchase the ability to transmit and receive at some maximum bandwidth, and users are allowed to burst (i.e., temporarily increase transmission and/or reception rates) to the maximum port speed they purchase. The performance at burst rate, however, is not guaranteed because the network is allowed to discard cells above the purchased sustained rate under conditions of high network load. This is a harmful drawback because in many applications, service suppliers need to guarantee service performance. For example, a service supplier may, for a certain application, require a 5 second response time but be unable to guarantee that level of performance.
The challenge of providing guaranteed response time is particularly difficult with applications that send and/or receive images because the requirements for bandwidth can vary in these applications from as low as 64 kilobits per second (“kbps”) to as high as 155 million bits per second (“mbps”) within the same imaging application. Table 1 shows typical uncompressed and compressed image sizes and image display times with a 56 kbps transport pipe (i.e., 56 kbps channel bandwidth). Response times can vary dramatically depending upon the size of the image.
TABLE 1
Un-
Example (time
Image
compressed
Compressed
Response
@ 56 kbps)
Dimension
Size
Size (JPEG)
Time
Typical image
400 ×
240 kbytes
24 kbytes
3.5 sec
640 × 480 screen
300 × 16
Full page color
2400 ×
15 Mbytes
1.5 Mbytes
3.5 min
image
3150 ×16
High resolution
10 K ×
200 Mbytes
20 Mbytes
48 min
photograph
10 K × 16
Various ways exist in the prior art to avoid the need for dynamic bandwidth. One of the more widely utilized ways is called Flashpix, developed by Kodak and Hewlett Packard. Flashpix is an image file format that stores images in a square-tile hierarchical file format. Imaging Internet Protocols defined by Hewlett Packard and Kodak, and widely used in the industry, allow application developers to display a defined number of the square tiles at any time in a window at any level within the hierarchy. The applications display only a fixed number of tiles which consume a fixed amount of bandwidth. If a user desires to display the entire image there is no way in the prior art to adjust the bandwidth dynamically to allow the whole image to be downloaded within a guaranteed response time.
For example, Table 2 contains a typical pricing for SVC service. Users are required to pay for a port speed, for example a 45 mbps port, and the per minutes charges shown in Table 2. For a screen image from Table 1, an end user could select a 64 kbps SVC at a variable bit rate of $0.03 per minute. The 24 kbytes screen image would download in 3.5 seconds. If during the session the user wanted to print the 1.5 Mbyte image, current ATM technology allows the application to burst up to the full port speed of 45 mbps for no additional charge. If the network is not congested, the bits will flow at 45 mbps and the 1.5 Mbyte image will be downloaded in less than 3.5 seconds. But if the network is congested, the ATM service will disregard the bits above the contracted 64 kbps SVC rate and the end-user response time is not guaranteed.
TABLE 2
BANDWIDTH
VARIABLE BIT
CONSTANT BIT
(kbps)
RATE ($/min.)
RATE ($/min.)
64
$0.03
$0.05
1,024
$0.69
$1.15
2,048
$0.95
$1.61
10,240
$10.00
$17.00
Thus, for many applications, the inability to adjust bandwidth dynamically to guarantee performance is a severe disadvantage.
SUMMARY OF THE INVENTION
The present invention provides a system and method of dynamically provisioning bandwidth that will substantially guarantee response time.
In one embodiment of the present invention, a network connection is established at some initial speed. The bandwidth usage through the connection is monitored, and when the connection becomes congested with data as defined by some predetermined parameters, the connection is dropped and a higher-speed connection is established. By provisioning the bandwidth dynamically, a substantially-guaranteed response time is provided that is economically attractive.
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AT&T Corp.
Jung Min
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