able SBC. Also consider the price of the SBC. High-available and high-redundant systems are usually expansive. Moreover, you can achieve redundancy in many different ways, which were previously discussed in this book. Following are some basic considerations when you are looking for a high- available SBC: Does the product support Geographical Diverse High availability? Does the product support Local Redundancy Active/Standby with stateful failover? Does the product support Local Redundancy Active/Active with stateful failover? Does the product support Clustering for Scalability? Does the product support zero downtime and zero call interruption during system upgrade when deployed in high availability model? Does the product support Redundant Hot Swappable Power Supplies? Does the product support Redundant Cooling Fans? Load Balancing Even though you might deploy a high-available redundant SBC, you might need to load balance your calls among multiple locations for many reasons. And you can check with your SBC vendor how it implements the load-balancing features among those sites. Following are load-balancing options (SIP and H.323): Round robin Least busy Proportional Automatic recursion within session agent group or among the dial-peers. In a SIP trunking configuration with multiple service providers, the ability to distrib- ute the incoming traffic from the other carrier to the various call agents. In a SIP trunking configuration with multiple service providers, the ability to distrib- ute the out-going traffic from the internal call-agents/endpoints to the various carriers. Can the number of routes attempted in a lookup be configured to set a max threshold? In a SIP configuration, describe in detail what mechanism the SBC platform has for determining that a call-agent is reachable and active. Also, describe the SBC platform behavior when it determines that a particular call-agent is either not reachable or not active. 180 SIP Trunking Describe methods for terminating a recursion of multiple routes in local routin