The Care and Feeding of ISDN4BSD
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6.1.2 The Controller Configuration 6.1 The isdnd.rc Configuration 6.1.4 Idletime Calculation for

6.1.3 The Entry Configuration Section

The configuration statements in an entry section are used to setup one particular link between you and a remote site and to configure and customize the various ways such a link can be operated.

The first configuration statement of every entry section should be:

The ISDN controller and B-channel to be used must be configured:

Then the interface the B-channel data shall be routed to must be specified:

The ``telephone'' numbers (or MSN's Multiple Subscriber Numbers) must be specified for the local and the remote sites:

Because this all is a bit confusing, lets look at an example of an incoming call from a remote site:


The D-channel layer 3 message signaling an incoming call contains the telephone number of the site which is calling us (040556677) and the telephone number which it wants to connect to (030112233). When isdnd gets this message, it searches its entry section configurations for a match. In our example, one of the entry sections contains the configuration remote-phone-incoming=040556677 and local-phone-incoming=030112233 which matches the numbers from the message of the incoming call and a connection is (when other parameters are matched as well) possible.

In case we have configured an outgoing link, for example:


In the corresponding entry configuration, the local number is configured as local-phone-outgoing=030112233 and the number of the site we want to connect to as remote-phone-outgoing=040123456. This two numbers will then become part of the outgoing D-channel layer 3 message to the exchange as the Calling Party Number and the Called Party Number.

Some remarks to telephone numbers:

Some configuration entries are only used for the telephone answering facility:

Currently only one B-channel protocol is supported, which is selected by:

Next, general characteristics of the connection are configured:

Another part to configure is the dialing and the recovery from dialing failures:

In case we are called back from the remote end or we call the remote back, times to wait for this two modes have to be configured:

One of the most complex parts to configure is the area of idle timeouts and short hold mode:

Sometimes it is desirable to run programs or shell-scripts when a connection is established and/or when a connection is shut down. This seems to be helpful especially for PPP connections using the isp driver. Two entry-keywords are provided to support this:

For the ipr - interfaces, two special entry keywords are provided to delay transmitting data on the B-channel after a connection is established for incoming and/or outgoing calls. They are needed, because the B-channel is usually (due to the nature of the protocol handshake used on the D-channel to establish a connection) switched through asymmetrically. This means, that one side is able to send data on the B-channel a bit more earlier than the other side is able to receive data which results in data loss (my observation is, that the first 200...500 bytes are lost). In case of the ipr - interface, this means that the very first 2 or 3 packets of a TCP connection get lost resulting in a long TCP connection setup time of 10 to 30 seconds. Using the following keywords to delay transmission in this case results in a very fast connection setup because no packets are lost:

Sometimes it is desirable to limit the number of possible outgoing calls within a certain amount of time. For this reason, the concept of a callout budget was introduced. Two types of budget combinations may be specified: one budget for locally initiated outgoing calls and another for remotly initiated outgoing calls as a result of a callback trigger operation:

The following feature is closely related to budgets because it allows you to specify time frames in which an entry is valid. With other words, with this keyword you are able to create several entries for one and the same connection but with different budget- or other parameters for different times of the day or week.

A new feature is that it is now possible to configure the isp - interfaces driectly from an entry in isdnd.rc instead of using ispppcontrol, the following keywords are used for that purpose:

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Hellmuth Michaelis 2001-08-16