Checking SIP authentication (SIP-Invite) for outgoing calls

In this article, we assume that you have access to the SIP traces of your phone system. One way to obtain those traces, is the Wireshark tool.

Please note that this topic requires advanced knowledge of VoIP and networking. If in doubt, please contact your network engineer.

Technical background

For establishing a VoIP call, one side sends a "SIP Invite" to invite another subscriber to join the conversation. In addition to the technical conditions, this also contains information about the calling subscriber. A separate SIP Invite is also created for call forwarding.

In order for this to be clearly identified by our infrastructure and for the call to be reliably transferred, it is crucial that the SIP user name of the call-initiating number is transmitted in the "SIP from address User Part" field - "From-User part" for short. If this does not happen, our infrastructure will reject the outgoing call attempt for security reasons.

Possible causes of failure

We regularly observe that systems are configured in such a way that, instead of the SIP user name, the User Provided Number (UPN) is transmitted in the From-User part, i.e. the call number that is to be displayed to the remote station

Please always use one of the following fields for transmitting the UPN:
P-Asserted-Identity
P-Preferred-Identity
From-Display
Remote Party ID

Learn more about this matter in our article „Configuring CLIP no screening correctlyn“.

So ist es richtig

Here is an excerpt from a trace with a properly configured SIP invite. The key data of the call are as follows:

Number block: 030-80951 (000-999)
SIP user name: 00493080951
UPN: Im Feld From-Display (hier die 03080951055)
Registrar: voip.easybell.de

From: "03080951055" <sip:00493080951@voip.easybell.de>;tag=xxxyyyzzz
SIP Display info: "03080951055"
SIP from address: sip:00493080951@voip.easybell.de
SIP from address User Part: 00493080951
SIP from address Host Part: voip.easybell.de
SIP from tag: xxxyyyzzz

If the trace of your connections shows the data as in this example, you can exclude the configuration of the caller ID as the cause for failure.

If not, please check the settings of your phone system for outgoing telephony and especially for call forwarding. In our help section you will find instructions for numerous models. If in doubt, please contact the manufacturer of your phone system to assist you with the setup.

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Name	Purpose	Lifetime	Type	Provider
CookieConsent	Saves your consent to using cookies.	2 year	HTML	Website
_pk_id	Used to store a few details about the user such as the unique visitor ID.	13 months	HTML	Matomo
_pk_ses	Short lived cookie used to temporarily store data for the visit.	30 minutes	HTML	Matomo
fe_typo_user	Assigns your browser to a session on the server.	session	HTTP	Website
apcCheckData	Availability Check	24 hours	HTML	Website
order_session	Availability Check	36 hours	HTML	Website
_ga	Used to distinguish users.	2 years	HTML	Google
_ga_V3PFWQFH0B	Used to persist session state.	2 years	HTML	Google

Name	Purpose	Lifetime	Type	Provider
_clck	Persists the Clarity User ID and preferences, unique to that site is attributed to the same user ID.	1 year	HTML	Microsoft Corporation
_clsk	Connects multiple page views by a user into a single Clarity session recording.	1 day	HTML	Microsoft Corporation
CLID	Identifies the first-time Clarity saw this user on any site using Clarity.	1 year	HTML	Microsoft Corporation
ANONCHK	Indicates whether MUID is transferred to ANID, a cookie used for advertising. Clarity doesn't use ANID and so this is always set to 0.	10 minutes	HTML	Microsoft Corporation
MR	Indicates whether to refresh MUID.	7 days	HTML	Microsoft Corporation
MUID	Identifies unique web browsers visiting Microsoft sites. These cookies are used for advertising, site analytics, and other operational purposes.	1 year	HTML	Microsoft Corporation
SM	Used in synchronizing the MUID across Microsoft domains.	session	HTML	Microsoft Corporation
_fbp	Used by Facebook to deliver a series of advertisement products such as real time bidding from third party advertisers	3 months	HTML	Facebook
fr	Ads targeting cookie for Facebook	3 months	HTML	Facebook
AnalyticsSyncHistory	This cookie is set by LinkedIn. Used to store information about the time a sync with the lms_analytics cookie took place for users in the Designated Countries	30 days	HTML	LinkedIn
UserMatchHistory	LinkedIn Ads ID syncing	30 days	HTML	LinkedIn
bcookie	Browser Identifier cookie to uniquely identify devices accessing LinkedIn to detect abuse on the platform. For more information about LinkedIn cookies, please navigate to https://www.linkedin.com/legal/l/cookie-table.	1 year	HTML	LinkedIn
bscookie	Used to remember a user's language setting to ensure LinkedIn.com displays in the language selected by the user in their settings	1 year	HTML	LinkedIn
lang	Used to memorize a user's language setting.	session	HTML	LinkedIn
li_sugr	Used to make a probabilistic match of a user's identity outside the Designated Countries	90 days	HTML	LinkedIn
lidc	To facilitate data center selection.	24 hours	HTML	LinkedIn
_guid	Used to identify a LinkedIn Member for advertising through Google Ads	90 days	HTML	Google
_gcl_au	Used to measure ad and campaign performance and conversion rates for Google ads on a site visited	90 days	HTML	Google
_gcl_aw	Used through Google Ads to understand user interaction with the site and advertising	90 days	HTML	Google
_gcl_dc	Used through Google Campaign Manager and DV 360 to understand user interaction with the site and advertising	90 days	HTML	Google