Technical data

4. Packages
• ISDN_CIRC_1_BANDWIDTH=’10000 30’
This is intended to add a second channel after 30 seconds if 10000 B/s were reached
during that timespan. This won’t work because ISDN has a maximum tranfer rate
of 8 kB/s.
If ISDN_CIRC_x_BUNDLING=’no’ is set the value in variable
ISDN_CIRC_x_BANDWIDTH is irrelevant.
Default setting: ISDN_CIRC_x_BANDWIDTH=”
ISDN_CIRC_x_LOCAL This variable holds the local IP address on the ISDN side.
This value should be empty if using dynamical address assignment. The IP address will
be negotiated during connection establishment. In most cases internet providers hand
out dynamic addresses. If a fixed IP address is used specify it here. This variable is
optional and has to be added to the config file.
ISDN_CIRC_x_REMOTE This variable holds the remote IP address and netmask on the
ISDN side. Classes Inter-Domain routing (CIDR) notation has to be used. Details for
CIDR (Page 39) can be found in the base documentation for IP_NET_x.
With dynamic address negotiation this should empty. The IP address will be negoti-
ated on connection establishment. In most cases internet providers hand out dynamic
addresses. If a fixed IP address is used specify it here. This variable is optional and has
to be added to the config file.
The netmask provided will be used for interface configuration after dial-in. A route to
the dial-in host itself will be generated as well. As you most probably won’t need this
route it is best to generate a direct route to the dial-in host by setting the netmask to
/32. For details see Chapter: Technical Details For Dialin (Page 366).
ISDN_CIRC_x_MTU ISDN_CIRC_x_MRU With this optional variable the so-called MTU
(maximum transmission unit) and MRU (maximum receive unit) can be set. Optional
means that the variable has to be added manually to the configuration file by the user!
Usually MTU is 1500 and MRU 1524. This settings should only be changed in rare
special cases!
ISDN_CIRC_x_CLAMP_MSS Set this to ’yes’ when using synchronous ppp
(ISDN_CIRC_x_TYPE=’ppp’) and one of the following symptoms occurs:
• Webbrowser connects to the webserver without error messages but no pages are
displayed and nothing happens,
• sending of small E-mails is working but bigger ones trigger problems or
• ssh works but scp hangs after initial connection.
Default setting: ISDN_CIRC_x_CLAMP_MSS=’no’
ISDN_CIRC_x_HEADERCOMP ISDN_CIRC_x_HEADERCOMP=’yes’ activates Van-Jacobson com-
pression or header compression. Not all providers are supporting this. If activated com-
pression leads to problems while dialing in set this to ’no’.
Default setting: ISDN_CIRC_x_HEADERCOMP=’yes’
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