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USER’S GUIDE
346 CyberSWITCH
configuration. If this option is disabled, the system will not negotiate compression with any remote
device. The default value is enabled.
Note that enable/disable applies to all protocols which support compression.
D
EFAULT PER-DEVICE COMPRESSION SETTING
You may enable or disable the per-device compression setting. This is in addition to the global
compression enable/disable state described above. The Default Per-Device Compression setting
defines the initial value for the per-device state when you add a new device to the on-node device
table. Or, if the device is authenticated via an off node server, the device will be given its
compression enable/disable state based on this value when no value is delivered by the off-node
database.
You may later change a specific device’s enable/disable state.
The per-device compression enable/disable state is only supported for connections using the PPP
protocol. The default value is enabled.
S
TARTING PPP STAC-LZS SEQUENCE NUMBER
Default value is 1. When using PPP Compression with the STAC-LZS protocol, a sequence
numbering scheme can be used whose initial value is required to be 1 by the protocol specification.
Some devices from other vendors do not start with 1. This results in a resynchronization sequence
on the first frame which is exchanged. When the user device fully supports the CCP protocol’s
Reset mechanism, this will only result in the minor inconvenience of a lost frame at the beginning
of a session. However, if such a device’s resynchronization mechanism is to completely renegotiate
CCP, this sequence will repeat infinitely.
This option provides an escape mechanism to allow interworking with such devices by modifying
the initial PPP STAC sequence number.
The Starting PPP STAC Sequence Number is maintained for each device. The value which appears
on this configuration screen provides the default value for the per-device value. When you add a
new device to the on-node device table, that device’s starting sequence number option will be
assigned the value which appears on this screen. You can then change this for each individual
device. Or, if the device is authenticated via an off node server that does not deliver a value for this
configuration item, the device will be given its starting sequence number from the value on this
menu
As its name implies, this option only applies to connections which utilize the PPP protocol with
STAC-LZS compression and sequence numbers checking.
COMPRESSION OPTIONS BACKGROUND INFORMATION
The system data compression capability allows the system to negotiate compression algorithms
with a remote device. This compression can be done using some proprietary bridging protocols and
also the PPP CCP protocol.
After successfully negotiating compression, data is compressed by a peer and transmitted to the
system. The system decompresses the data, processes the addressing information contained in the
device data, and transmits the data as required. The converse is also true, the system can receive
data coming from a WAN or LAN, compresses the data before transmitting it to a peer. The net