Some carrier(like QWEST) support D-channel sharing between several PRIs. Here is the paragraph from Qwest web site:
"With the NI-2 protocol, you have more flexibility when purchasing multiple ISDN PRI. The first ISDN PRI must be configured as a 23B+D. The additional ISDN PRI may be configured as 23B+Back-up D or 24B. One D channel can do the signaling for up to 479 B channels (20 facilities) if they all terminate at the same destination. "
Does asterisk libpri support this feature?
Any info will be appreciated. Thanks!