ability Emergency Call Routing Dial Plan and Call Routing Considerations IP Addressing 95 Understanding the Centralized Model with Direct Media Model Summary 97 Chapter 7 Design and Implementation Considerations Geographic and Regulatory Considerations IP Connectivity Options Physical Delivery and Connectivity IP Addressing Dial Plans and Call Routing 104 Porting Phone Numbers to SIP Trunks Emergency Calls Supplementary Services Voice Calls Voice Mail Transcoding Mobility Network Demarcation Service Provider UNI Compliance Codec Choice Fault Isolation Statistics Billing 111 QoS Marking Security Considerations SIP Trunk Levels of Security Exposure Access Lists (ACL) Hostname Validation NAT and Topology Hiding xii SIP Trunking Firewalls Security Protection at the SIP Protocol Level SIP Listening Port Transport Layer Security (TLS) Back-to-Back User Agent (B2BUA) SIP Normalization Digit Manipulation SIP Privacy Methods Registration and Authentication Toll Fraud Signaling and Media Encryption Session Management, Call Traffic Capacity, Bandwidth Control, and QoS Trunk Provisioning Bandwidth Adjustments and Consumption Call Admission Control (CAC) Limiting Calls per Dial-Peer Global Call Admission Control Quality of Service (QoS) Traffic Marking Delay and Jitter Echo 128 Congestion Management Voice-Quality Monitoring Scalability and High Availability Local and Geographical SIP Trunk Redundancy Border Element Redundancy In-Box Hardware Redundancy Box-to-Box Hardware Redundancy (1+1) Clustering (N+1) Load Balancing Service Provider Load Balancing Domain Name System (DNS) CUCM Route Groups and Route Lists Cisco Unified SIP Proxy PSTN TDM Gateway Failover SIP Trunk Capacity Engineering SIP Trunk Monitoring Summary 139 Further Reading Chapter 8 Interworking Protocols Applications Endpoints Service Provider SIP Trunk Interworking-SP UNI SIP Normalization Media DTMF 148 DTMF Relay DTMF Relay Methods DTMF Relay Conversion Codecs 150 Payload Types Codec Filtering or Stripping Transcoding Transrating Fax and Modem Traffic T.38 a