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Each SIP Header which may contain "the" caller-id has follows the same structure:
- From: "FROM_DISPLAYNAME" <FROM_USER@SERVER>
- P-Asserted-Identity: "PAI_DISPLAYNAME" <PAI_USER@SERVER>
- P-Preferred-Identity: "PPI_DISPLAYNAME" <PPI_USER@SERVER>
In a pure SIP Environment, the DISPLAYNAME part contains the users name as text, the USER part contains either the username, but also often the extensions or caller-id. Most SIP providers use the following mapping:
| Header Part | Usage |
|---|---|
| FROM_USER | Authentication Username |
| PAI_USER | caller-id |
| PPI_USER | caller-id |
| FROM_DISPLAYNAME | not used |
| PAI_DISPLAYNAME | not used |
| PPI_DISPLAYNAME | not used |
The caller-id itself has also varying possibilities of formatting. The caller-id has typically the following structure:
(international-prefix) (international code) (national code) (base number) (extension)
the most varying element can be the "international-prefix", which is often just a plus "+" sometimes it may also be a double zero "00". The following examples show the varying options for the caller-id "+492593890"
| Name | International Prefix | International Code | National Code | Base Number | Extension |
|---|---|---|---|---|---|
| International Number with plus | + | 49 | 30 | 259389 | 0 |
| International Number with double zero | 00 | 49 | 30 | 259389 | 0 |
| International Number without prefix | 49 | 30 | 259389 | 0 | |
| National Number (note: 0 as National Prefix) | 030 | 259389 | 0 | ||
| Unknown Number / Local Number - without prefixes | 259389 | 0 |
Most providers do only accept one of the above variants, in order to display the correct caller-id or even to forward the call at all.
ISDN
The beroNet Gateway has also the ability to match dialplan rules against the caller id. It uses the Source in the dialplan for matching and the NewSource to generate the caller id for the outbound technology.
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