Bytes column

NOTE The Size and Bytes columns can also be shown in the Workspace browser simply by modifying what to show in the browser via right clicking on any column heading (name) where a shortcut menu pops up and the selection can be made of what entries to show in the Workspace browser. 

Migrating only the raw data - the characters, numbers, bits, and bytes - forward is not enough to ensure usability. The meta data and the context for the application or database must also be migrated forward. Meta data are the code to the machine-stored bits and bytes. Meta data are the data about the data. They describe the data in the database. The meta data documentation describes the method of data capture, the application used to access the data, security rules for the tables and columns, and other descriptive and procedural information. For derived or calculated data, the algorithm or protocol that was used must be known. The documentation then becomes something else that must be preserved. Without the meta data, the reader will only see a series of alphabetic characters. Without the entire described context associated with the data, the data have no meaning. 

Traditionally data, properties, information etc has been stored in files on computer disks. More recently, it has become common practice on Macintosh computers, when using Microsoft software or some UNIX applications, to use either extensions to the file name or the first few bytes in the file (or another file) to indicate some aspects of the data, for example that it is suitable for Microsoft Excel. While this approach is practical to indicate something about files containing columns of data, it is not appropriate to store information about the values in cells in spreadsheet or how it relates to data in other columns. This requires a relational database such as ORACLE, and for performance reasons the values in the cells may only be accessed via the ORACLE API (Application Programming Interface) or SQL (Standard Query Language), in other words, it is suggested that relational databases such as ORACLE should be viewed as sophisticated file systems which allow the values to be organised, efficiently stored, rapidly retrieved etc. 

Let b be the block length in bits. Throughout the encryption process, a matrix of bytes containing containing a partial result is maintained. It is called the State, and has b/ il columns and four rows. The State initially consists of a block of plaintext, written vertically into the arrays, column by column. At the end, the ciphertext for the block wiU be taken by reading the State in the same order. 

Figure 15.6(b) shows an example of the SONET STS-1 fi ame that corresponds to a frame in Fig. 15.6(a). In this example, each VT1.5 path carried on the payload of this STS-1 frame represents a channel (time slot) in Fig. 15.6(a). The STS-1 frame is divided into two portions transport overhead and information payload, where the transport overhead is further divided into line and section overheads. The STS frame is transmitted every 125 ixs. The first three columns of the STS-1 frame contain transport overhead and the remaining 87 columns and 9 rows (a total of 783 bytes) carry the STS-1 synchronous payload envelope (SPE). The SPE contains a 9-byte path overhead that is used for end-to-end service performance monitoring. Optical carrier level-1 (OC-1) is the lowest level optical signal used at equipment and network interfaces. An OC-1 is obtained fi om a STS-1 after scrambling and electrical-to-optical conversion. 

The 810 bytes of an STS-1 frame are most conveniently represented as a matrix consisting of 9 rows and 90 columns as shown in Fig. 15.22. The intersection of a row and a column is one byte. The order of transmission is from left to right and from top to bottom. 

The STS-1 SPE has its own frame consisting of 9 rows and 87 columns. The first column of the SPE is path overhead, which is allocated to support path layer functionality. The remainder of the SPE is available for payload. Although the SPE fits within the STS-1 SPE capacity, the first byte of the SPE does not necessarily occupy the first byte position within the SPE capacity. Thus, the SPE is represented as being offset from the STS-1 frame. 

An STS-N or OC-N is created by byte-interleaving JV frame-aligned STS-Is as shown in Fig. 15.25. Since the STS-1 s are frame aligned, the transport overheads from each individual STS-1 will come out as a block occupying the first 3 x JV columns of the STS-N, effectively becoming the transport overhead for the STS-N. 

The STS-1 SPE can be subdivided into virtual tributaries (VTs) to allow bandwidth management at finer granularities ranging from approximately 1.5 up to 6 Mb/s. There are four sizes of VT defined, the VT1.5, VT2, VT3, and VT6. These sizes correspond roughly to rates of 1.7,2, 3, and 6 Mb/s, respectively. The sizes are all multiples of 9 bytes so that they will occupy an integer number of columns in the 9 row structured STS-1 SPE frame. 

The SCREEN BITS column, which is effectively 48 bytes long, contains a bit... 

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