Link Control Protocol options

The following options are used to configure the Link Control Protocol for a link device:

Asynchronous control character map

The asynchronous control character map. This is a 32-bit mask that represents control characters with ASCII values 0 through 31. If a bit is set to 1, PPP encodes the corresponding control character before sending it over the link. For example, the transmission of binary data could cause a link to hang if the value 19 (XOFF) is sent on a link that uses software (XON/XOFF) flow control. A map with a value 0xa0000 causes PPP to encode for data values corresponding to both XON and XOFF. The value 0xffffffff encodes all control characters. You can set the value of the map to 0 if the link is configured to use hardware flow control. The final value of the map that is negotiated for use on a link is a combination of the maps requested by each side.

Maximum receive unit size

The maximum receive unit (MRU) size in bytes for this end of the PPP link. Increasing this value will generally improve performance on non-interactive sessions as it reduces the percentage of header bytes transmitted. The suggested value is 1500 bytes.

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NOTE: If the links are to be used in a multilink bundle, it is suggested that the MRU should be at least 6 bytes greater than the maximum received reconstructed unit (MRRU) that is configured in the bundle for outgoing connections, or in the global bundle for incoming connections. This will prevent fragmentation over a single link.

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Use address and control field compression

Whether address and control field compression is enabled.

Use protocol field compression

Whether protocol field compression is enabled.

Negotiate magic number

Whether magic number negotiation is enabled. The magic numbers generated by each end of a link should be different. If they are the same, it is probable that the host is trying to create a PPP link to itself. The usual reason for this is that the UUCP chat script (see Systems(4bnu)) has failed to log in, or PPP on the remote system has failed to start correctly.

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NOTE: Magic number negotiation should normally be enabled.

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Send LCP identification messages

Whether LCP identification messages are enabled.