Avaya Configuring PPP Services Bedienungsanleitung PDF herunterladen (Seite 52)

Configuring PPP Services

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During LCP negotiation, both peers negotiate the characters that they will

recognize as modem control characters. PPP calculates and displays a map value

based on this negotiation. Each end of the link maintains an asynchronous control

character map for both sending and receiving.

When sending data, PPP inserts the escape character 0x7D in front of the control

character and does a logical XOR operation, combining the control character with

the value 0x20. When the receiving peer encounters these characters in the data

stream, it strips off the escape character and converts the next character to the

original asynchronous modem control character.

The async control character map consists of 32 bits. Each bit corresponds to one

control character, 0x00 (the right end of the map) through 0x1F (the left end of the

map); that is, 0 through 31, decimal. The actual map is a value used essentially as

a mask. For example, the default map value, 0xA0000 (655360 decimal) allows

the escaping of the control characters 0x11 (XON) and 0x13 (XOFF) if they occur

in the data stream. Almost all modems need only this default value. The characters

0x7D and 0x7E are special characters that are always escaped in asynchronous

data transmission. Chapter 3 describes how to build a customized async control

character map.

PPP Line Parameters

When you enable PPP on a circuit (the default), PPP automatically sets the line

parameters shown in Table 2-4

. These parameters are the same for both

synchronous and asynchronous connections.

Depending on the configuration, you may have to specify explicitly certain other

parameters. For more information on these parameters, refer to Configuring and

Managing Routers with Site Manager, depending on your platform.

Table 2-4. PPP Line Parameter Values

Parameter Value

BOFL Disable

Promiscuous Enable

Service Transparent

WAN Protocol PPP

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 151 152

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Avaya Configuring PPP Services Bedienungsanleitung Seite 52