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ncp...
bcp Sets the Bridging Control Protocol (BCP) parameters.
Example:
set bcp
TINYGRAM COMPRESSION [no]:
Tinygram Compression
Specifies whether or not Tinygram Compression is used. This
option is useful for protocols that are prone to problems when
bridged over low-speed (64 Kbps and below) lines. These protocols
add zeroes between the data and the frame checksum to pad the
Protocol Data Unit (PDU) to the minimum size. Tinygram
compression removes the zeroes and preserves the frame
checksum at the transmitting end. At the receiving end, it restores
the packet to the minimum length.
ccp options
Prompts you for the configurable options of the compression algorithms.
Some of the options may be modified later by PPP negotiations with the
peer router on the WAN link. For additional information, see “Using the Data
Compression Subsystem” in
Using and Configuring Features
.
Example:
set ccp options
STAC: # histories [1]?
STAC: check mode (0=none, 1-LCB, 2=CRC, 3=Seq) [3]?
STAC: # histories
This sets the number of compression “contexts” or “histories” that
are used by the STAC compression engine.
A nonzero value means that the compression engine maintains the
specified number of histories where it keeps information about
previous data sent in packets. This historical data is used to
improve the effectiveness of the compression.
The receiver maintains a similar history and as long as the
transmitter and receiver keep their histories in sync, the receiver
can properly decompress the packets it receives. If the histories get
out of sync, packets are discarded as unusable data. Normally, you
should set the number of histories to 1 unless the link quality is
very poor.
A value of zero means that each packet sent is compressed without
regard to any past packets sent and may always be reliably
decompressed by the receiver. However, because the compressor
cannot exploit any information derived from examining prior
packets, the effectiveness of the compression usually is not as
good.
Some implementations support more than one history, subdividing
the data stream into separate streams that are compressed
independently. The router does not support the use of more than
one history on a PPP link.
STAC: check mode (0=none, 1=LCB, 2=CRC, 3=Seq)
STAC compressed datagrams normally include a check value used
by the two ends of the link to recognize when a compressed packet
has been lost or corrupted, and some action is needed to
re-synchronize the sender’s and receiver’s histories.
Configuring PPP Interfaces (Talk 6)
Chapter 33. Configuring and Monitoring Point-to-Point Protocol Interfaces 475