Eicon Networks C21 Guia de Instalação descarregar pdf (Página 186)

Line Speeds and Performance 186

X.25 Window Size

Window Size specifies the packet interval at which information transfer stops

while the sending node awaits acknowledgment from the receiver. Windowing

allows more than one packet to be transmitted before an acknowledgment is

received from the nearest node. X.25 windowing is designed to reduce waiting

time for acknowledgments between nodes, as well as end-to-end.

If the Window Size is 10, an application can send ten packets before it must

wait for an acknowledgment of receipt from the remote computer.

Transmission of packets stops only when the maximum number of packets

allowed by the transmit window has been sent and no acknowledgment has yet

been received from the remote computer. When the remote computer

acknowledges packets quickly, the transmission of packets flows continuously.

One acknowledgment may confirm the receipt of several packets.

The Eiconcard allows window sizes ranging from 1 to 127 packets depending

on the Eiconcard type and memory capacity. Increase Window Size for

networks with larger delays.

Note

Few public X.25 networks offer windowing of more than 2 packets.

When packet sizes are small, increasing the size of X.25 windows can increase

effective throughput by as much as 20 percent. The ideal Window Size is one

that allows continuous data flow without ever having the window closed

waiting for an acknowledgment.

Note

X.25 allows negotiation of Window Size on a connection basis,

depending on your subscription to the X.25 network.

Satellite X.25 Networks

If you are transmitting data on an X.25 network that uses satellites, you may

need a larger X.25 window. Satellite networks experience greater delays as the

signals are relayed into orbit and back to earth.

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Eicon Networks C21 Guia de Instalação Página 186