Cyclades User's Guide manual Parity, Port

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maximum length of a packet depends on the communication

 

medium. As an example, in Ethernet networks the maximum

 

length is1500 bytes. A data packet can be divided into two parts:

 

the header part and the data part. The header contains information

 

needed for communication between nodes; the data is the body of

 

the packet that is ultimately received by the application.

Parity

In serial communications, the parity bit is used in a simple error

 

detection algorithm. As a stream of data bits is formed, an extra

 

bit, called the parity bit, is added. This bit is set on (1) or off (0),

 

depending on the serial communications parameters set in the

 

UART chip.

 

The following lists the available parity parameters and their

 

meanings:

 

Odd – Parity bit set so that there is an odd number of 1 bits

 

Even – Parity bit set so that there is an even number of 1 bits

 

None – Parity bit is ignored, value is indeterminate

PCMCIA

Personal Computer Memory Card International Association – An

 

organization that supports standards for a compact hardware

 

interface that accepts a variety of devices such as modems,

 

storage, and other devices.

Port

A port is a 16-bit number (the allowed range being 1 through

 

65535) used by the TCP and UDP protocols at the transport layer.

 

Ports are used to address applications (services) that run on a

 

computer. If there was only a single network application running

 

on the computer, there would be no need for port numbers and the

 

IP address only would suffice for addressing services. However,

 

several applications may run at once on a particular computer and

 

we need to differentiate among them. This is what port numbers

 

are used for. Thus, a port number may be seen as an address of an

 

application within the computer.

PPP

Point-to-Point Protocol. This protocol is a way to connect your

 

computer to the Internet over telephone lines. PPP is replacing an

 

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Page 481
Image 481
Cyclades User's Guide manual Parity, Port