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LANCOM Reference Manual LCOS 3.50 ̈ Chapter 7: Routing and WAN connections
94
Routing and WAN
connections
to begin output of the PPP protocol frames exchanged during a terminal ses-
sion. You can perform a detailed analysis once the connection has been bro-
ken if this terminal session has been logged in a log file.
7.6.2 Everything o.k.? Checking the line with LCP
The devices involved in the establishment of a connection through PPP nego-
tiate a common behaviour during data transfer. For example, they first decide
whether a connection can be made at all using the security procedure, names
and passwords specified.
The reliability of the line can be constantly monitored using the LCP once the
connection has been established. This is achieved within the protocol by the
LCP echo request and the associated LCP echo reply. The LCP echo request is
a query in the form of a data packet which is transferred to the remote station
along with the data. The connection is reliable and stable if a valid response
to this request for information is returned (LCP echo reply). This request is
repeated at defined intervals so that the connection can be continually mon-
itored.
What happens when there is no reply? First a few retries will be initiated to
exclude the possibility of any short-term line interference. The line will be
dropped and an alternative route sought if all the retries remain unanswered.
If, for example, the high-speed connection refuses to work, an existing ISDN
port can open the way to the Internet as a backup.
During remote access of individual workstations with Windows oper-
ating systems, we recommend switching off the regular LCP requests
since these operating systems do not reply to LCP echo requests.
The LCP request behaviour is configured in the PPP list for each indi-
vidual connection. The intervals at which LCP requests should be
made are set by the entries in the 'Time' and 'Retr.' fields, along with
the number of retries that should be initiated without a response
before the line can be considered faulty. LCP requests can be switched
off entirely by setting the time at '0' and the retries at '0'.
7.6.3 Assignment of IP addresses via PPP
In order to connect computers using TCP/IP as the network protocol, all par-
ticipating computers require a valid and unique IP address. If a remote station
does not have its own IP address (such as the individual workstation of a