Watchguard Firebox X1000 Reference Manual page 101

Pppd requests Deflate compression in preference to BSD-Compress if the
peer can do either.
Reference Guide
values give better compression but consume more kernel memory
for compression dictionaries. Alternatively, a value of 0 for nr or
nt disables compression in the corresponding direction. Use
nobsdcomp or bsdcomp 0 to disable BSD-Compress compression
entirely.
debug
Enables connection debugging facilities. When this option is
given, pppd logs the contents of all control packets sent or
received in a readable form.
default-asyncmap
Disables asyncmap negotiation, forcing all control.
default-mru
Disables Maximum Receive Unit (MRU) negotiation. With this
option, pppd uses the default MRU value of 1,500 bytes for both
the transmit and receive direction.
deflate nr,nt
Requests that the peer compress packets that it sends, using the
Deflate scheme with a maximum window size of 2**nr bytes, and
agree to compress packets sent to the peer with a maximum
window size of 2**nt bytes. If nt is not specified, it defaults to the
value given for nr. Values in the range 8 to 15 can be used for nr
and nt; larger values give better compression but consume more
kernel memory for compression dictionaries. Alternatively, a
value of 0 for nr or nt disables compression in the corresponding
direction. Use nodeflate or deflate 0 to disable Deflate
compression entirely.
idle n
Specifies that pppd should disconnect if the link is idle for n
seconds. The link is idle when no data packets (that is, IP packets)
are being sent or received. Note: It is not advisable to use this
option with the persist option without the demand option. If the
PPP Initialization Strings
N
OTE
89