Implementing SIP Telephony for High Call Volumes

Call centers and large enterprises face unique challenges when implementing SIP Telephony. Network protection, SIP normalization, system survivability, and load balancing—among other issues—take on greater significance as the number of concurrent calls scales above several hundred and approaches one thousand.


Network Performance

With high-volume calling, the enterprise network requires close monitoring and adjustment to ensure the level of network performance is able to support high voice quality. Whether the enterprise opts for a SIP trunking solution or a hosted SIP service, Quality of Service (QoS),  traffic shaping, and WAN optimization will need special attention. These protocol parameters should be closely watched and tweaked. A high-quality enterprise session border controller (eSBC), combined with a cloud-based edge orchestration service is very useful—even essential—in taking care of these issues.

SIP Trunk Application Drawing

Live, real-time network monitoring and alerting can help engineers identify and correct performance issues before they cause business-critical impairments to enterprise communications. The right eSBC will come with cloud-based edge orchestration capability and will offer the required software features and capabilities that support such performance controls.

Hosted SIP Application Drawing

Network Protection

As the number of simultaneous calls increases, so does the exposure to security threats. Toll fraud, especially, is a major concern. Security features to look for when selecting the eSBC include the following:

  • Network separation—including a clear demarc between the service-provider WAN and the enterprise LAN. Split configuration domain within the eSBC makes it natural to enforce this security mechanism
  • Encryption—both media (SRTP) and signaling (TLS) should be encrypted to prevent intercept, snooping, and hacking of the enterprise traffic.
  • Other basics—Intrusion protection, denial of service (DoS) prevention, trusted peer, and stateful firewall, are essential security services to check off when selecting the eSBC.


With enterprise communications traversing various service-provider networks, and involving users in remote and home offices, all with diverse vendor equipment (handsets, softphones, and so on), interoperability is key. The SIP protocol is flexible by design. It has been implemented in many different, vendor-specific “dialects.” A good eSBC provides SIP normalization or “translation” between differing dialects.

High-Volume eSBC with Cloud Edge Orchestration

For a high-capacity eSBC that supports up to 1,000 concurrent SIP calls, and that can be managed via cloud edge orchestration, consider the new SmartNode SN5600 Session Border Controller.

What do you think?

  • Which issues do you consider most critical for a large enterprise SIP implementation:  network performance or network protection?
  • What sort of interoperability challenges have you faced when setting up a high-capacity enterprise SIP solution?


W. Glendon Flowers
Product Marketing Manager | Patton LLC
Glendon is responsible for creating corporate marketing and technical content including press releases, web copy, white papers, case studies, educational and tutorial pieces as well as other publications. He serves as editor-in-chief for Patton's email newsletter and other outbound communications. He holds a Bachelor of Science in Computer Science from UMUC and a Bachelor of Music in percussion performance from UMCP. Mr. Flowers is a single father with three adult daughters: Lauren, Hannah & Sarah (twins). He plays guitar, bass, keyboards, drums, and percussion and enjoys composing and arranging music and songs.

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