SIP Provider British Telecom (UK) (kb4788)

The information in this article applies to:

  • SwyxWare 2015

[ Summary | Information | Links ]


Information und configuration hints for SIP provider British Telecom (Great Britain/UK).

This knowledgebase article provides information when configuring the SwyxWare with the following BT SIP Services:
-          BT Wholesale SIP Trunking (WSIPT)
-          BT Global Services One Voice SIP trunk UK


General information

British Telecom (BT) is offering registerless SIP trunks. This means that the authentication is based on the public IP address of the SwyxWare server. Therefore, you need a static, public IP address from your ISP assigned to the SwyxWare server.

BT is operating with a number of different servers. Therefore it is not possible to preconfigure the Proxy Server in the "SIP" tab of the Trunkgroup Properties dialog. In this field, please enter the IP address that BT has named you.


For your convenience the generated CustomProviderProfiles.config is available for download at the end of this article. Extended information about how to use this file can be found at Configuration and Adaptation of SIP Providers via Provider Profiles (kb3436).

Important: From SwyxWare2015R4 on, the provider profile for British Telecom (UK) is available in the list of provider profiles and the CustomProviderProfiles.config is no longer necessary.

During creation of the SIP Trunkgroup, the profile 'British Telecom (UK)' must be selected.

In case that the SwyxWare server is running with a private IP address and the static, public IP address is provided by NAT gateway, it is necessary to configure a STUN server in the properties of the SIP trunk group, under the tab 'SIP'. A list of public STUN servers can e.g. be found at In this case, it is necessary to configure the correct portwarding in the NAT gateway, such that inbound SIP requests are being forwarded to port 65002 of the SwyxWare server.

If no NAT gateway is necessary, the BT SIP trunk has to be configured such that inbound SIP requests are being directly sent to port 65002 of the SwyxWare server.

For additional information, it is possible to download a configuration guide at the end of this article.

BT expects a Session interval of 600 (seconds) on outbound calls. The prevent reINVITES which would slow down the call establishment, underneath the registry key  HKLM\Software\Wow6432Node\Swyx\LinkMgr\CurrentVersion\Options two new DWORD values SipMinSessionTimerIntervalSeconds and SipSessionTimerIntervalSeconds  can be created with an assigned value of 600 (decimal). After creating this value, the LinkMgr service must be restarted.
Important: This setting will affect all SIP Trunks.

Tested Features

  • Incoming/outgoing national calls
  • Correct Calling Line Identification (CLI) on national
  • CLIP No Screening
  • Holding and retrieving calls
  • Toggeling between two calls
  • Call transfer
  • Conferencing
  • Mutually supported codecs:
    • G.711a
    • G.711µ
    • G.729
    • T.38 for FAX negotiation
  • Incoming/outgoing DTMF signaling in accordance with via RFC2833
  • T.38 Negotiation and FAX transmission

Test date:
21/01/2016 with SwyxWareV2015R3

Further tested SIP providers


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