[Serusers] local ACK found -> dropping it!

[Corey]

Having some troubles with a new voip gateway service we're using; hoping 
someone could provide any advice.

To sum up:

Call is initiated from pots line; gets routed to voip gateway provider; gateway 
forwards invite to our ser server; one ring then busy signal is heard on 
originating/requesting pots line; the destined softphone UA, registered via 
our ser server, never gets call.

As far as I can fathom, ser recieves an INVITE forwarded/routed from the 
gateway, then ser requests auth/cred, then gateway responds with an 
ACK and at that point everything just stops.

Assistance is much appreciated, as I'm unable to determine what may be 
causing the issue. 


208.xxx.xxx.xx  =  3rd-party/commercial voip gateway server
206.xx.xx.x     =  our ser proxy server

1234567890 = originating pots line
8889997777 = softphone UA number ( aliased to sip uri 'blah at 206.xx.xx.x' )


ngrep:

#
U 208.xxx.xxx.xx:5060 -> 206.xx.xx.x:5060
  INVITE sip:8889997777 at 206.xx.xx.x SIP/2.0..Via: SIP/2.0/UDP 208.xxx.xxx.xx:5060;branch=z9hG4bK40f0830c;rport..From: "John Doe" <sip:1234567890 at 208.xxx.xxx.xx>;tag=as5f35b551..To: <s
  ip:8889997777 at 206.xx.xx.x>..Contact: <sip:1234567890 at 208.xxx.xxx.xx>..Call-ID: 02c132b659e84c2321debbf226051e3d at 208.xxx.xxx.xx..CSeq: 102 INVITE..User-Agent: Asterisk PBX..Max-Forwards: 70
  ..Date: Fri, 24 Feb 2006 22:28:05 GMT..Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY..Content-Type: application/sdp..Content-Length: 397....v=0..o=root 32669 32669 IN IP4
   208.xxx.xxx.xx..s=session..c=IN IP4 208.xxx.xxx.xx..t=0 0..m=audio 10784 RTP/AVP 0 18 8 3 111 4 97 101..a=rtpmap:0 PCMU/8000..a=rtpmap:18 G729/8000..a=fmtp:18 annexb=no..a=rtpmap:8 PCMA/80
  00..a=rtpmap:3 GSM/8000..a=rtpmap:111 G726-32/8000..a=rtpmap:4 G723/8000..a=rtpmap:97 iLBC/8000..a=rtpmap:101 telephone-event/8000..a=fmtp:101 0-16..a=silenceSupp:off - - - -..
#
U 206.xx.xx.x:5060 -> 208.xxx.xxx.xx:5060
  SIP/2.0 407 Proxy Authentication Required..Via: SIP/2.0/UDP 208.xxx.xxx.xx:5060;branch=z9hG4bK40f0830c;rport=5060..From: "John Doe" <sip:1234567890 at 208.xxx.xxx.xx>;tag=as5f35b551..To
  : <sip:8889997777 at 206.xx.xx.x>;tag=2d38da4c38ea547b795405b32554c3bb.f3cb..Call-ID: 02c132b659e84c2321debbf226051e3d at 208.xxx.xxx.xx..CSeq: 102 INVITE..Proxy-Authenticate: Digest realm="208.1
  39.204.245", nonce="43fe339b33d7c58a0d89e4711838584d"..Server: Sip EXpress router (0.9.4 (i386/linux))..Content-Length: 0..Warning: 392 206.xx.xx.x:5060 "Noisy feedback tells:  pid=2
  974 req_src_ip=208.xxx.xxx.xx req_src_port=5060 in_uri=sip:8889997777 at 206.xx.xx.x out_uri=sip:8889997777 at 206.xx.xx.x via_cnt==1"....
#
U 208.xxx.xxx.xx:5060 -> 206.xx.xx.x:5060
  ACK sip:8889997777 at 206.xx.xx.x SIP/2.0..Via: SIP/2.0/UDP 208.xxx.xxx.xx:5060;branch=z9hG4bK40f0830c;rport..From: "John Doe" <sip:1234567890 at 208.xxx.xxx.xx>;tag=as5f35b551..To: <sip:
  8889997777 at 206.xx.xx.x>;tag=2d38da4c38ea54795405554c3bb...Contact: <sip:1234567890 at 208.xxx.xxx.xx>..Call-ID: 02c132b659e84c2321debbf226051e3d at 208.xxx.xxx.xx..CSeq: 102 ACK..User-A
  gent: Asterisk PBX..Max-Forwards: 70..Content-Length: 0....

... end of transmission;
no further exchange after gateway ACK;
originating pots line hears a single ring, then fast busy signal;
softphone UA never recieves INVITE or anything


ser debug:

IP Request:
 0(2974)  method:  <INVITE>
 0(2974)  uri:     <sip:8889997777 at 206.xx.xx.x>
 0(2974)  version: <SIP/2.0>
 0(2974) parse_headers: flags=1
 0(2974) Found param type 232, <branch> = <z9hG4bK40f0830c>; state=6
 0(2974) Found param type 235, <rport> = <n/a>; state=17
 0(2974) end of header reached, state=5
 0(2974) parse_headers: Via found, flags=1
 0(2974) parse_headers: this is the first via
 0(2974) After parse_msg...
 0(2974) preparing to run routing scripts...
 0(2974) parse_headers: flags=128
 0(2974) end of header reached, state=9
 0(2974) DEBUG: get_hdr_field: <To> [31]; uri=[sip:8889997777 at 206.xx.xx.x]
 0(2974) DEBUG: to body [<sip:8889997777 at 206.xx.xx.x>
]
 0(2974) get_hdr_field: cseq <CSeq>: <102> <INVITE>
 0(2974) DEBUG:maxfwd:is_maxfwd_present: value = 70
 0(2974) DBG:maxfwd:process_maxfwd_header: value 70 decreased to 16
 0(2974) DEBUG: add_param: tag=as5f35b551
 0(2974) end of header reached, state=29
 0(2974) parse_headers: flags=256
 0(2974) DEBUG: get_hdr_body : content_length=397
 0(2974) found end of header
 0(2974) find_first_route: No Route headers found
 0(2974) loose_route: There is no Route HF
 0(2974) is_local(): Realm '206.xx.xx.x' is local
 0(2974) parse_headers: flags=16384
 0(2974) pre_auth(): Credentials with given realm not found
 0(2974) build_auth_hf(): 'Proxy-Authenticate: Digest realm="208.xxx.xxx.xx", nonce="43fe35e639b33d7c58a0d89e47df7fe11838584d"
'
 0(2974) parse_headers: flags=-1
 0(2974) check_via_address(208.xxx.xxx.xx, 208.xxx.xxx.xx, 0)
 0(2974) DEBUG:destroy_avp_list: destroying list (nil)
 0(2974) receive_msg: cleaning up
 0(2974) SIP Request:
 0(2974)  method:  <ACK>
 0(2974)  uri:     <sip:8889997777 at 206.xx.xx.x>
 0(2974)  version: <SIP/2.0>
 0(2974) parse_headers: flags=1
 0(2974) Found param type 232, <branch> = <z9hG4bK40f0830c>; state=6
 0(2974) Found param type 235, <rport> = <n/a>; state=17
 0(2974) end of header reached, state=5
 0(2974) parse_headers: Via found, flags=1
 0(2974) parse_headers: this is the first via
 0(2974) After parse_msg...
 0(2974) preparing to run routing scripts...
 0(2974) parse_headers: flags=4
 0(2974) DEBUG: add_param: tag=2d38da4c38ea547b795405b32554c3bb.f3cb
 0(2974) end of header reached, state=29
 0(2974) DEBUG: get_hdr_field: <To> [73]; uri=[sip:8889997777 at 206.xx.xx.x]
 0(2974) DEBUG: to body [<sip:8889997777 at 206.xx.xx.x>]
 0(2974) DEBUG: sl_filter_ACK : local ACK found -> dropping it!
 0(2974) DEBUG:destroy_avp_list: destroying list (nil)
 0(2974) receive_msg: cleaning up