Channels seem to stay open even after calls are over. They build up forever. I haven’t tested enough, but I am pretty sure that eventually this locks new calls out. This list is about a day since the last Asterisk restart. The first few are current ulaw calls, but the rest are not active calls. 172.22.9.3 is my voip gateway.
asterisk*CLI> sip show channels
Peer User/ANR Call ID Seq (Tx/Rx) Format Hold Last Message
172.22.9.101 (None) 7fdc5ea8-2f 00101/05680 0x0 (nothing) No Rx: REGISTER
172.22.12.148 448 678a18106e1 00102/00000 0x4 (ulaw) No Tx: ACK
172.22.9.3 +143567170 SEAMGC03200 00101/00001 0x4 (ulaw) No Rx: ACK
172.22.9.3 +120874730 5dfc527c2e5 00102/00000 0x4 (ulaw) No Tx: ACK
172.22.12.101 401 b55a3a4ae2f 00101/64069 0x4 (ulaw) No Rx: ACK
172.22.9.3 +180165328 28a21beb2c0 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120818016 5e6f606544b 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120818016 13d238543ce 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120818016 3f57996d083 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +180165328 04bfed4e2cb 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120874732 33e245f636a 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120885103 0c747a95680 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120885292 0da73f040ec 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120885292 67e78595218 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120824173 0b73e30424b 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120824173 5c0dbbea715 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120812084 2f26923a49a 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120833444 6ed334e3133 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120840768 50aa470039c 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120833984 5ceb86c6447 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120874731 101b0910720 00102/00000 0x0 (nothing) No Init: INVITE
172.22.9.3 +120874734 3aecbc3457d 00102/00000 0x0 (nothing) No Init: INVITE