Here is some junk from tcpdump
23:04:00.668914 IP (tos 0x10, ttl 35, id 61624, offset 0, flags [DF], proto UDP (17), length 1465)
54.172.60.0.5060 > 10.251.14.186.5060: [udp sum ok] SIP, length: 1437
INVITE sip:[email protected] SIP/2.0
Record-Route: sip:54.172.60.0:5060;lr;ftag=03636896_6772d868_0b7fbbd3-eb17-4a75-9ec2-2cb4f7df9975
From: sip:[email protected];tag=03636896_6772d868_0b7fbbd3-eb17-4a75-9ec2-2cb4f7df9975
To: sip:[email protected];user=phone
CSeq: 31073 INVITE
Max-Forwards: 61
Accept: application/sdp,application/isup,application/dtmf,application/dtmf-relay,multipart/mixed
P-Asserted-Identity: sip:[email protected]:5060
Content-Disposition: session;handling=required
Diversion: sip:[email protected];reason=unconditional
Call-ID: [email protected]
Via: SIP/2.0/UDP 54.172.60.0:5060;branch=z9hG4bK8d2e.6d812a91.0
Via: SIP/2.0/UDP 172.18.5.96:5060;branch=z9hG4bK0b7fbbd3-eb17-4a75-9ec2-2cb4f7df9975_6772d868_1763044002874572
Contact: sip:[email protected]:5060;transport=udp
Allow: INVITE,ACK,CANCEL,BYE,UPDATE,OPTIONS
User-Agent: Twilio Gateway
X-Twilio-AccountSid: ACe8281c857a15388463f36c20ad518e2c
X-Twilio-ApiVersion: 2010-04-01
Content-Type: application/sdp
X-Twilio-CallSid: CAf1b93afe473254c52a40415c31081055
Content-Length: 250
v=0
o=- 1091482841 1091482841 IN IP4 54.172.60.115
s=Twilio Media Gateway
c=IN IP4 54.172.60.115
t=0 0
m=audio 10170 RTP/AVP 0 101
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=sendrecv
a=maxptime:20
a=ptime:20
23:04:00.669313 IP (tos 0x60, ttl 64, id 35445, offset 0, flags [none], proto UDP (17), length 760)
10.251.14.186.5060 > 54.172.60.0.5060: [bad udp cksum 65ce!] SIP, length: 732
SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 54.172.60.0:5060;branch=z9hG4bK8d2e.6d812a91.0;received=54.172.60.0;rport=5060
Via: SIP/2.0/UDP 172.18.5.96:5060;branch=z9hG4bK0b7fbbd3-eb17-4a75-9ec2-2cb4f7df9975_6772d868_1763044002874572
From: sip:[email protected];tag=03636896_6772d868_0b7fbbd3-eb17-4a75-9ec2-2cb4f7df9975
To: sip:[email protected];user=phone;tag=as2f82089f
Call-ID: [email protected]
CSeq: 31073 INVITE
Server: FPBX-13.0.61.1(13.7.2)
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH, MESSAGE
Supported: replaces, timer
WWW-Authenticate: Digest algorithm=MD5, realm=“asterisk”, nonce="6d0dbf4f"
Content-Length: 0
23:04:00.748656 IP (tos 0x10, ttl 35, id 61635, offset 0, flags [DF], proto UDP (17), length 449)
54.172.60.0.5060 > 10.251.14.186.5060: [udp sum ok] SIP, length: 421
ACK sip:[email protected] SIP/2.0
Via: SIP/2.0/UDP 54.172.60.0:5060;branch=z9hG4bK8d2e.6d812a91.0
From: sip:[email protected];tag=03636896_6772d868_0b7fbbd3-eb17-4a75-9ec2-2cb4f7df9975
Call-ID: [email protected]
To: sip:[email protected];user=phone;tag=as2f82089f
CSeq: 31073 ACK
Max-Forwards: 70
User-Agent: Twilio Gateway
Content-Length: 0
23:04:00.755148 IP (tos 0x10, ttl 37, id 18706, offset 0, flags [DF], proto UDP (17), length 1469)
54.172.60.1.5060 > 10.251.14.186.5060: [udp sum ok] SIP, length: 1441
INVITE sip:[email protected] SIP/2.0
Record-Route: sip:54.172.60.1:5060;lr;ftag=45382281_6772d868_e26a8b64-f80d-4353-a614-2be7183c60a9
From: sip:[email protected];tag=45382281_6772d868_e26a8b64-f80d-4353-a614-2be7183c60a9
To: sip:[email protected];user=phone
CSeq: 31073 INVITE
Max-Forwards: 61
Accept: application/sdp,application/isup,application/dtmf,application/dtmf-relay,multipart/mixed
P-Asserted-Identity: sip:[email protected]:5060
Content-Disposition: session;handling=required
Diversion: sip:[email protected];reason=unconditional
Call-ID: [email protected]
Via: SIP/2.0/UDP 54.172.60.1:5060;branch=z9hG4bK82e1.48771c66.0
Via: SIP/2.0/UDP 172.18.14.147:5060;branch=z9hG4bKe26a8b64-f80d-4353-a614-2be7183c60a9_6772d868_1763057144876588
Contact: sip:[email protected]:5060;transport=udp
Allow: INVITE,ACK,CANCEL,BYE,UPDATE,OPTIONS
User-Agent: Twilio Gateway
X-Twilio-AccountSid: ACe8281c857a15388463f36c20ad518e2c
X-Twilio-ApiVersion: 2010-04-01
Content-Type: application/sdp
X-Twilio-CallSid: CAf1b93afe473254c52a40415c31081055
Content-Length: 250
v=0
o=- 1633755016 1633755016 IN IP4 54.172.60.116
s=Twilio Media Gateway
c=IN IP4 54.172.60.116
t=0 0
m=audio 14560 RTP/AVP 0 101
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=sendrecv
a=maxptime:20
a=ptime:20
23:04:00.755427 IP (tos 0x60, ttl 64, id 37247, offset 0, flags [none], proto UDP (17), length 762)
10.251.14.186.5060 > 54.172.60.1.5060: [bad udp cksum ba2c!] SIP, length: 734
SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 54.172.60.1:5060;branch=z9hG4bK82e1.48771c66.0;received=54.172.60.1;rport=5060
Via: SIP/2.0/UDP 172.18.14.147:5060;branch=z9hG4bKe26a8b64-f80d-4353-a614-2be7183c60a9_6772d868_1763057144876588
From: sip:[email protected];tag=45382281_6772d868_e26a8b64-f80d-4353-a614-2be7183c60a9
To: sip:[email protected];user=phone;tag=as71a2822d
Call-ID: [email protected]
CSeq: 31073 INVITE
Server: FPBX-13.0.61.1(13.7.2)
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH, MESSAGE
Supported: replaces, timer
WWW-Authenticate: Digest algorithm=MD5, realm=“asterisk”, nonce="3d68b01b"
Content-Length: 0
23:04:00.827630 IP (tos 0x10, ttl 37, id 18709, offset 0, flags [DF], proto UDP (17), length 449)
54.172.60.1.5060 > 10.251.14.186.5060: [udp sum ok] SIP, length: 421
ACK sip:[email protected] SIP/2.0
Via: SIP/2.0/UDP 54.172.60.1:5060;branch=z9hG4bK82e1.48771c66.0
From: sip:[email protected];tag=45382281_6772d868_e26a8b64-f80d-4353-a614-2be7183c60a9
Call-ID: [email protected]
To: sip:[email protected];user=phone;tag=as71a2822d
CSeq: 31073 ACK
Max-Forwards: 70
User-Agent: Twilio Gateway
Content-Length: 0