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The SBC Session Border Controller provisions basic geo-redundancy and DNS load balancing.

Background Information

  • The Integrated Access Device (IAD) is registered with an Application Server (AS).
  • The AS is protected by an SBC. The IAD discovers the SBC via DNS resolution and the SBC discovers the AS by pre-configured routing or external DB dip (e.g. ENUM).
  • Once registered, the IAD communicates with a specific SBC, and the SBC forwards requests to the specific AS (address was stored during registration).
  • For calls terminating to the IAD, the IADs register their AORs.
  • IAD has been registered by two paths and can afford for one path to fail and still receive service on the other, when it supports outbound. In a normal scenario where the IAD registers through one path and is unable to refresh the register, it moves on to an alternate SBC from DNS.


Figure : Basic Service Availability- DNS

  1. The IAD is configured with a FQDN identifying a set of SBCs.
  2. The DNS supplies multiple SBC IP addresses (local, remote or a combination of both).
  3. Basic geo-redundancy and load balancing between the SBCs are enabled. With geo-redundancy, if an SBC fails, the IAD re-registers through a different path.

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