ssrs barcode image The ATM cell and header in Software

Drawer QR-Code in Software The ATM cell and header

15.4.3 The ATM cell and header
Read QR Code In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
Painting QR In None
Using Barcode drawer for Software Control to generate, create QR image in Software applications.
The standard ATM cell is made up of 53 octets, where an octet is a sequence of 8 bits. The 8-bit sequence is also known as a byte, but it should be noted that in computer terminology a byte can consist of other than 8 bits (see also Sec. 15.7). The cell structure shown in Fig. 15.3a is seen to consist of a 5 octet header, and a 48 octet payload. The header contains a number of fields which provide the information necessary to guide the cell through the network. These fields are described later, but as seen in Fig. 15.3, the header for cells at the point of entry to a network (at a UNI) differs slightly from the header for cells traversing a NNI. The header fields are: GFC. This is the generic flow control field. Its function is to provide control and metering of the data flow before it enters the network. No flow control is exercised once the cell has entered the network. The 4 bits in the header are reallocated as described under VPI.
QR Code JIS X 0510 Decoder In None
Using Barcode reader for Software Control to read, scan read, scan image in Software applications.
Paint Denso QR Bar Code In Visual C#.NET
Using Barcode generation for .NET framework Control to generate, create QR Code 2d barcode image in .NET framework applications.
Fifteen
Print QR In Visual Studio .NET
Using Barcode drawer for ASP.NET Control to generate, create QR-Code image in ASP.NET applications.
QR Generation In .NET Framework
Using Barcode maker for .NET framework Control to generate, create QR Code JIS X 0510 image in .NET applications.
Header (5 octets)
QR Code Printer In VB.NET
Using Barcode encoder for VS .NET Control to generate, create QR-Code image in .NET framework applications.
Painting GTIN - 12 In None
Using Barcode generation for Software Control to generate, create UPC Code image in Software applications.
Payload (48 octets) (a)
EAN 13 Drawer In None
Using Barcode generator for Software Control to generate, create EAN 13 image in Software applications.
Paint Code-128 In None
Using Barcode generation for Software Control to generate, create Code 128 Code Set B image in Software applications.
7 GFC VPI
Data Matrix Printer In None
Using Barcode encoder for Software Control to generate, create Data Matrix 2d barcode image in Software applications.
Paint Code 39 Extended In None
Using Barcode creator for Software Control to generate, create Code 39 image in Software applications.
3 VPI VCI
Universal Product Code Version E Creator In None
Using Barcode drawer for Software Control to generate, create UPC - E0 image in Software applications.
Bar Code Creation In .NET
Using Barcode creator for Reporting Service Control to generate, create bar code image in Reporting Service applications.
VCI VCI HEC (b) PT CLP
Encode UPC A In Java
Using Barcode printer for Java Control to generate, create UPC-A Supplement 2 image in Java applications.
ANSI/AIM Code 39 Generation In None
Using Barcode generation for Font Control to generate, create Code-39 image in Font applications.
Bit No. Octet No.1 2 3 4 5
Painting Linear In C#
Using Barcode drawer for .NET framework Control to generate, create 1D image in VS .NET applications.
Making EAN 13 In .NET Framework
Using Barcode encoder for Reporting Service Control to generate, create EAN / UCC - 13 image in Reporting Service applications.
7 VPI
UCC - 12 Printer In Java
Using Barcode generation for BIRT reports Control to generate, create GTIN - 128 image in Eclipse BIRT applications.
Scanning UPC Symbol In .NET Framework
Using Barcode decoder for .NET Control to read, scan read, scan image in VS .NET applications.
5 VPI
3 VCI
VCI VCI HEC (c) PT CLP
Bit No. Octet No.1 2 3 4 5
PT CLP
HEC (d)
Payload
(a) ATM cell structure; (b) UNI header; (c) NNI header; (d) header and payload bit stream.
VCI. This is the virtual channel identifier field. A virtual channel carries a single stream of cells, which may be a mixture of voice, video, image, and data. From the point of view of the users, the different signals appear to have their own channels, and hence these are called virtual channels. Each channel is identified by its VCI. VPI. This is the virtual path identifier field. Virtual channels can be bundled together to form what is termed a virtual path. With binary coding it should be kept in mind that all the information forms a single serial bit stream, which is transmitted over a physical link (e.g., optical fiber and satellite). The VPI enables the cells to be grouped into separate (but virtual) paths over the physical link. Switching within the network can be carried out by switching the virtual paths, without the need to switch the channels separately. As shown in Fig. 15.3, the GFC field is not required for cells once they are in the network, and the 4 bits for this field are reassigned to the VPI field, which enables the number of virtual paths within the network to be increased.
Satellites in Networks
CLP. This is the cell loss priority field. It consists of a single bit, a 1 for a low priority cell, meaning that the cell can be discarded in the event of congestion. A 0 indicates high priority, meaning that the cell should only be discarded if it cannot be delivered. HEC. This is the header error control field. The HEC field enables single bit errors in the header (including the HEC field) to be corrected, and double bit errors to be detected (but not corrected). The receiver is normally in the error correction mode, and if a single error is detected it will be corrected and the cell transmitted onward. However, after detection and correction of a single error the receiver automatically switches to the error detection mode, and of course if more than one error is detected to start with, it will automatically switch to error detection mode and the cell will be discarded. In error detection mode, no errors are corrected, and cells with errors are discarded. Once a cell with an error-free header is detected, the receiver automatically switches back to error-correction mode. The rationale behind this approach is discussed at length in Goralski (1995). Error control is applied only to the header (the data in the payload may have its own error-control coding). ATM was originally used for transmission over low bit error rate (BER) links such as optical fiber, where the bit error probability can be as low as 10 11 compared to a BER that 2 can be as high as 10 over satellite links. Furthermore, bit errors in satellite links often occur in bursts which require special error-control coding (see Secs. 11.3.3 and 11.6). The HEC field is placed at the end of the header as shown in Fig. 15.3d where it functions also as a marker for cell position.
Copyright © OnBarcode.com . All rights reserved.