Inbound Calling Integration Guide


Derrick Tanzini


Bandwidth has multiple geographically redundant signaling proxy facilities in the United States. The specifications below provide detail as to what should be expected.


SBC (Session Border Controller) IP Information

Bandwidth employs mated pairs of SBC's for signaling redundancy.  For Inbound Calling services, please ensure that both IP addresses provided are configured for inbound traffic in the event that one SBC is offline. Your implementation specialist assisting with onboarding will be providing these IP addresses during the onboarding kick-­‐off call, or via the welcome email.


SIP (Session Initiation Protocol)

Bandwidth SIP signaling protocol is designed for RFC3261.  If any other method is used, calls will fail to set up.


Allowed Ports for Media/Audio

If a customer PBX is protected by a firewall, manufacturer compliance will need to be verified that the firewall has the ability to act as either a SIP ALG or a Back-­‐to-­‐Back User Agent (B2BUA).  The following ports are required to allow for full 2-­‐way audio:

  • UDP port 5060 – must be opened to support SIP signaling
  • UDP ports 1024-­‐64,000 – must be opened either statically or dynamically (ALG) to allow for audio path.
  • Bandwidth uses multiple IP addresses to allow media from its gateways



The following attributes are allowed within Bandwidth SIP trunks:

  • DTMF
  • Dial Plans
  • Codecs
  • Signaling Protocol
  • IP Protocol
  • Media Anchoring


Supported DTMF

Bandwidth supports both in-­‐band and out-­‐of-­‐band DTMF outlined in RFC2833.


Dial Plans

Bandwidth supports E.164 for inbound calling only. This is an international recognized standard characterized by a "+" followed by the country code, then phone number.  For example:

Local & Long Distance: +19192971000 International: +4402074942020


IP Protocols

Bandwidth requires that all SIP and audio be delivered via UDP, in packets no larger than 1350 bytes. TCP is not supported.


Supported Codecs

Codec list choices:

  • G711ulaw, G729a, ILBC (will default to ptime 30)
  • G711ulaw, G729a  (will default to ptime 20)


Call Concurrency Limits

Please contact the CSA to determine what the appropriate call concurrency limits are.  If a customer's call concurrency limit is reached, a 503-­‐Service Unavailable or 486-­‐Busy Here Signal message will be provided to the customer.


Supported Caller ID / Privacy Types

  • FROM field – default option for caller ID name, number and rating.
  • RPID (Remote Party ID) – secondary option
  • P-­‐Asserted ID – supported option
  • Privacy Headers – supported option



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