Algo doorbel¶

The unit is not able to correctly terminate the calls when the next hop is a state-full SIP Proxy. A state-full SIP Proxy uses record route to maintain the same signaling path for all subsequent messages part of the same dialog. The unit does not handle this situation, which is standard setup of any VoIP provider that uses a SIP Proxy instead of using a VoIP switch like Asterisk or FreeSwitch, which behave like an end-point.

Secondly, the unit does not correctly send the BYE to the right next hop when there is more than one SIP server for the same domain (regardless of whether it is a SIP Proxy or not).

The log is below:

2013-01-01T00:41:05+01:00 xs4all phone: sip recv 85.17.186.7:5060, size = 2095
2013-01-01T00:41:05+01:00 xs4all phone: [truncated] INVITE sip:1972@192.168.1.9:5060 SIP/2.0#015#012Record-Route: <sip:85.17.186.7;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.a08d838>#015#012Record-Route: <sip:81.23.228.129;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.c5809b45>#015#012Record-Route: <sip:85.17.186.7;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.908d838>#015#012Record-Route: <sip:81.23.228.129;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>#015#012Record-Route: <sip:81.23.228.129;transport=tcp;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>#015#012Via: SIP/2.0/UDP 85.17.186.7:5060;branch=z9hG4bK0159.28ff94f5.0#015#012Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bK0159.338f5a74.0#015#012Via: SIP/2.0/UDP 85.17.186.7:5060;branch=z9hG4bK0159.18ff94f5.0#015#012Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bK0159.238f5a74.0;i=7db2#015#012Via: SIP/2.0/tcp 192.168.1.57:57428;received=82.161.39.123;rport=57428;branch=z9hG4bKPjkhvJ8eoLpQhZKMzod4XgVhJZrJxAEtUe#015#012Max-Forwards: 66#015#012From: "Adrian Georgescu" <sip:ag@ag-projects.c

Expanded messages below for clarity with the relevant headers, notice the Record-Route headers:

INVITE sip:1972@192.168.1.9:5060 SIP/2.0
Record-Route: <sip:81.23.228.129;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.c5809b45>
Record-Route: <sip:85.17.186.7;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.908d838>
Record-Route: <sip:81.23.228.129;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>
Record-Route: <sip:81.23.228.129;transport=tcp;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>
From: "Adrian Georgescu" <sip:ag@ag-projects.com>;tag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks
To: <sip:1972@ag-projects.com>
Contact: <sip:52138976@82.161.39.123:57428;transport=tcp>
Call-ID: YsTJTTdp5Kxb6eYrxDqViOkl2GaJUCd7

2013-01-01T00:41:06+01:00 xs4all phone: sip send 85.17.186.7:5060, size = 1193
2013-01-01T00:41:06+01:00 xs4all phone: [truncated] SIP/2.0 180 Ringing#015#012Via: SIP/2.0/UDP 85.17.186.7:5060;branch=z9hG4bK0159.28ff94f5.0#015#012Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bK0159.338f5a74.0#015#012Via: SIP/2.0/UDP 85.17.186.7:5060;branch=z9hG4bK0159.18ff94f5.0#015#012Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bK0159.238f5a74.0;i=7db2#015#012Via: SIP/2.0/tcp 192.168.1.57:57428;received=82.161.39.123;rport=57428;branch=z9hG4bKPjkhvJ8eoLpQhZKMzod4XgVhJZrJxAEtUe#015#012Record-Route: <sip:85.17.186.7;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.a08d838>#015#012Record-Route: <sip:81.23.228.129;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.c5809b45>#015#012Record-Route: <sip:85.17.186.7;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.908d838>#015#012Record-Route: <sip:81.23.228.129;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>#015#012Record-Route: <sip:81.23.228.129;transport=tcp;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>#015#012From: "Adrian Georgescu" <sip:ag@ag-projects.com>;tag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmk
2013-01-01T00:41:06+01:00 xs4all phone: sip send 85.17.186.7:5060, size = 1421
2013-01-01T00:41:06+01:00 xs4all phone: [truncated] SIP/2.0 200 OK#015#012Via: SIP/2.0/UDP 85.17.186.7:5060;branch=z9hG4bK0159.28ff94f5.0#015#012Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bK0159.338f5a74.0#015#012Via: SIP/2.0/UDP 85.17.186.7:5060;branch=z9hG4bK0159.18ff94f5.0#015#012Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bK0159.238f5a74.0;i=7db2#015#012Via: SIP/2.0/tcp 192.168.1.57:57428;received=82.161.39.123;rport=57428;branch=z9hG4bKPjkhvJ8eoLpQhZKMzod4XgVhJZrJxAEtUe#015#012Record-Route: <sip:85.17.186.7;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.a08d838>#015#012Record-Route: <sip:81.23.228.129;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.c5809b45>#015#012Record-Route: <sip:85.17.186.7;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.908d838>#015#012Record-Route: <sip:81.23.228.129;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>#015#012Record-Route: <sip:81.23.228.129;transport=tcp;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>#015#012From: "Adrian Georgescu" <sip:ag@ag-projects.com>;tag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks#015#012To
2013-01-01T00:41:07+01:00 xs4all phone: sip recv 85.17.186.7:5060, size = 706
2013-01-01T00:41:07+01:00 xs4all phone: ACK sip:1972@82.161.39.123:61031 SIP/2.0#015#012Via: SIP/2.0/UDP 85.17.186.7:5060;branch=z9hG4bK0159.18ff94f5.2#015#012Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bK0159.238f5a74.2#015#012Via: SIP/2.0/UDP 85.17.186.7:5060;branch=z9hG4bK0159.18ff94f5.2#015#012Via: SIP/2.0/UDP 81.23.228.129:5060;branch=z9hG4bK0159.238f5a74.2;i=7db2#015#012Via: SIP/2.0/tcp 192.168.1.57:57428;received=82.161.39.123;rport=57428;branch=z9hG4bKPj6Uyn5PV6pApqRSblxHYaZ-7P.0Aid2IR#015#012Max-Forwards: 66#015#012From: "Adrian Georgescu" <sip:ag@ag-projects.com>;tag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks#015#012To: <sip:1972@ag-projects.com>;tag=530668702#015#012Call-ID: YsTJTTdp5Kxb6eYrxDqViOkl2GaJUCd7#015#012CSeq: 31053 ACK#015#012User-Agent: Blink Pro 2.0.3 (MacOSX)#015#012Content-Length: 0#015#012#015
2013-01-01T00:42:05+01:00 xs4all phone: sip send 81.23.228.129:5060, size = 429
2013-01-01T00:42:05+01:00 xs4all phone: BYE sip:52138976@82.161.39.123:57428;transport=tcp SIP/2.0#015#012Via: SIP/2.0/UDP 192.168.1.9:5060;rport;branch=z9hG4bK688014405#015#012From: <sip:1972@ag-projects.com>;tag=530668702#015#012To: "Adrian Georgescu" <sip:ag@ag-projects.com>;tag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks#015#012Call-ID: YsTJTTdp5Kxb6eYrxDqViOkl2GaJUCd7#015#012CSeq: 27636006 BYE#015#012Allow: INVITE, ACK, CANCEL, BYE, INFO#015#012Max-Forwards: 70#015#012User-Agent: Algo 8028 1.7.8#015#012Content-Length: 0#015#012#015
2013-01-01T00:42:05+01:00 xs4all phone: sip recv 81.23.228.129:5060, size = 495
2013-01-01T00:42:05+01:00 xs4all phone: SIP/2.0 200 OK#015#012Via: SIP/2.0/UDP 192.168.1.9:5060;rport=61031;received=82.161.39.123;branch=z9hG4bK688014405#015#012Record-Route: <sip:81.23.228.129;transport=tcp;lr;r2=on;ftag=530668702>#015#012Record-Route: <sip:81.23.228.129;lr;r2=on;ftag=530668702>#015#012Call-ID: YsTJTTdp5Kxb6eYrxDqViOkl2GaJUCd7#015#012From: <sip:1972@ag-projects.com>;tag=530668702#015#012To: "Adrian Georgescu" <sip:ag@ag-projects.com>;tag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks#015#012CSeq: 27636006 BYE#015#012Server: Blink Pro 2.0.3 (MacOSX)#015#012Content-Length: 0#015#012#015

Broken BYE¶

Algo sends this BYE message, which never arrives at the original destination as the intermediate SIP proxy has no information where to route it (it has no Route headers):

BYE sip:52138976@82.161.39.123:57428;transport=tcp SIP/2.0
Via: SIP/2.0/UDP 192.168.1.9:5060;rport;branch=z9hG4bK688014405
From: <sip:1972@ag-projects.com>;tag=530668702
To: "Adrian Georgescu" <sip:ag@ag-projects.com>;tag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks
Call-ID: YsTJTTdp5Kxb6eYrxDqViOkl2GaJUCd7
CSeq: 27636006 BYE
Allow: INVITE, ACK, CANCEL, BYE, INFO
Max-Forwards: 69
User-Agent: Algo 8028 1.7.8
Content-Length: 0

Correct BYE¶

The correct BYE message must be (observe the missing Route headers that the unit must add, they must be copied in reverse order from the original INVITE Record-Route headers same when Algo was building the 200 OK message, which incidentally is done correctly):

BYE sip:52138976@82.161.39.123:57428;transport=tcp SIP/2.0
Via: SIP/2.0/UDP 192.168.1.9:5060;rport;branch=z9hG4bK688014405
From: <sip:1972@ag-projects.com>;tag=530668702
Route: <sip:81.23.228.129;transport=tcp;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>
Route: <sip:81.23.228.129;r2=on;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.b5809b45>
Route: <sip:85.17.186.7;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.908d838>
Route: <sip:81.23.228.129;lr;ftag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks;did=1a8.c5809b45>
To: "Adrian Georgescu" <sip:ag@ag-projects.com>;tag=x0VdFW8sEn3bymiNLIQFWpc7Bqe0Hmks
Call-ID: YsTJTTdp5Kxb6eYrxDqViOkl2GaJUCd7
CSeq: 27636006 BYE
Allow: INVITE, ACK, CANCEL, BYE, INFO
Max-Forwards: 69
User-Agent: Algo 8028 1.7.8
Content-Length: 0

Incorrect Next Hop¶

The BYE message must be sent to the IP:port where the unit has received the INVITE from and not by performing a new DNS lookup. By doing a DNS lookup one may find another SIP Proxy from the same domain that has no knowledge about this dialog, there should never be a DNS lookup performed in the middle of an established SIP dialog, the standard is explicit about this behavior.