We use HOMER to extend packet captures between our network and yours which also includes encrypted packets sent over TLS and port 5061.


  1. Login into your account.
  2. Select Tools.
  3. Select Trace.
  4. Search the number you wish to trace

NB – we only hold trace data for a maximum of 24 hrs due to the volume of data we collect.

Reading a SIP capture

Via:  SIP/2.0/TLS;rport;branch=z9hG4bKPjoQMLjD6b2raEOAUVy5zyw-gkqicHm5uy;alias
Max-Forwards:  69
From:  "Mike Johnstone" <>;tag=j9VrEnzQvI8GDUzXupl02A2lXfF7dRmx
Contact:  <sip:13106341780@;transport=TLS;;ob>
Call-ID: SPB4-cvKPwGtbfEu4XuopOQ6MlNgtNaS
CSeq:  28848 INVITE
Supported:  replaces, 100rel, timer, norefersub
Session-Expires:  1800
Min-SE:  90
User-Agent:  MySIPcity iOSn/sdp
Content-Length: 279


The INVITE is the contact information of the next hop in the call route. In the above example, the username of the next hop is 14242179560, who is hosted by

Via: SIP/2.0/TLS;rport;branch=z9hG Max-Forwards: 69

The Via header field indicates the path taken by the request so far and helps in routing the responses back along the same path. If the SIP INVITE passed through multiple SIP proxies, there will be multiple VIA headers. In the given example, the responses will be sent back to the WAN IP at the port 50813.

From: “Mike Johnstone” <>;tag=j9

The From header field indicates contact information of the initiator of the SIP INVITE request, Mike Johnstone in this case.


The To header field contains the information about the called party or the recipient of the request, or the number 14242179560 in this example.

Call-ID: SPB4-cvKPwGtbfEu4XuopOQ6MlNgtNaS

The Call-ID header field is a unique ID identifying the SIP call. All messages containing this call-id will be assigned to the same SIP call.

Contact: <sip:13106341780@;transport=TLS;;ob>

The Contact header field provides a SIP or SIPS URI that should be used to contact the sender of the INVITE, Mike.

Common SIP Response Codes

1xx = Informational SIP responses

  • 100 Trying – Extended search is being performed so a forking proxy must send a 100 Trying response.
  • 180 Ringing – The Destination User Agent has received the INVITE message and is alerting the user of call.
  • 183 Session Progress – This response may be used to send extra information for a call which is still being set up.

2xx = Success responses

  • 200 OK – Shows that the request was successful.

4xx = Request failures

  • 400 Bad Request: The request could not be understood due to malformed syntax.
  • 401 Unauthorized :The request requires user authentication. This response is issued by us as part of the normal password challenge and response process
  • 403 Forbidden: The server understood the request but is refusing to fulfill it. Sometimes (but not always) this means the call has been rejected by the receiver.
  • 404 Not Found: The server has definitive information that the user does not exist at the domain specified in the Request-URI. This status is also returned if the domain in the Request-URI does not match any of the domains handled by the recipient of the request.
  • 407 Proxy Authentication Required: The request requires user authentication. This response is issued by proxies.
  • 408 Request Timeout: Couldn’t find the user in time. The server could not produce a response within a suitable amount of time, for example, if it could not determine the location of the user in time. The client MAY repeat the request without modifications at any later time. 

5xx = Server errors

  • 500 Internal Server Error: The server could not fulfill the request due to some unexpected conditions.
  • 502 Bad Gateway: The server is acting as a gateway or proxy and received an invalid response from a downstream server while attempting to fulfill the request.
  • 503 Service Unavailable: The server is undergoing maintenance or is temporarily overloaded and so cannot process the request. A “Retry-After” header field may specify when the client may reattempt its request.

6xx = Global failures

  • 600 Busy Everywhere – All possible destinations are busy.
  • 603 Decline – Destination cannot or is refusing to participate in the call but on our network also signals the account has no credit.
  • 604 Does Not Exist Anywhere – The server has authoritative information that the requested user does not exist anywhere.
  • 606 Not Acceptable – The user’s agent was contacted successfully but some aspects of the session description were not acceptable.
  • 607 Unwanted – The called party did not want his call from the calling party. Future attempts from the calling party are likely to be similarly rejected.
Updated on 24 October 2021

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