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Chapter 11: AI2524 Sync PPP Configuration Steps
August 1997 Page 11-7
2524UM
Configure
Automatic
Detection of
Encapsulation
Type
You can enable a serial or ISDN interface to accept calls and dynami-
cally change the encapsulation on the interface when the remote de-
vice does not signal the call type. For example, if an ISDN call does
not identify the call type in the Lower Layer Compatibility fields and
is using an encapsulation that is different from the one configured on
the interface, the interface can change its encapsulation type on the fly.
This feature enables interoperation with ISDN terminal adapters that
use V.120 encapsulation but do not signal V.120 in the call setup mes-
sage. An ISDN interface that, by default, answers a call as synchro-
nous serial with PPP encapsulation can change its encapsulation and
answer such calls.
Automatic detection is attempted for the first 10 seconds after the link
is established or for the first 5 packets exchanged over the link, which-
ever is first.
In interface configuration mode, enable automatic detection of encap-
sulation type:
autodetect encapsulation
encapsulation-type
You can specify one or more encapsulations to detect. Cisco IOS soft-
ware currently supports automatic detection of PPP and V.120 encap-
sulations.
Configure
Compression of
PPP Data
You can configure point-to-point software compression on serial inter-
faces that use PPP encapsulation. Compression reduces the size of a
PPP frame via lossless data compression. The compression algorithm
used is a predictor algorithm (the RAND algorithm), which uses a
compression dictionary to predict the next character in the frame.
PPP encapsulations support both predictor and Stacker compression
algorithms.
Compression is performed in software and might significantly affect
system performance. Disable compression if the router CPU load ex
ceeds 65%. To display the CPU load, use th
show process cpu
EXEC command.
If the majority of your traffic is already compressed files, do not us
compression.
In interface configuration mode, configure compression over PPP:
1. Enable encapsulation of a single protocol on the serial line.
encapsulation ppp