The Situation

In 2008 the FDA conducted an analysis of the Public Switched Telephone Network (PSTN) costs using traditional Primary Rate ISDN (PRI) Time Division Multiplex (TDM) connectivity and compared that to costs related to using Session Initiation Protocol (SIP) Voice Over IP (VoIP) based connectivity for all for inbound and outbound calling for the White Oak campus. The savings using SIP VoIP trunks was compelling by using VoIP versus TDM and the conversion to SIP based trunks (SIP trunking) was approved and implemented.

Some of the Benefits included;

  • Eliminated the dependencies of fixed installed PRI’s on campus with minimum service redundancy
  • All calls to any other agency on the HHS Networks contract is free.
  • No long Distance (LD) charges
  • 1500 minutes for each session monthly shared per user
  • DID Redundancy available to FDA (for emergency)
  • Portal access for each DN on Verizon’s network to monitor, track, forward, etc. calls
  • Advance call routing features available on SIP

The SIP trunking service was provided via existing Verizon MPLS connectivity into two of the FDA data centers. To ensure interoperability with the Verizon SIP trunking service Verizon required its customers to terminate SIP the trunks to a dedicated Session Border Controller (SBC) security appliance. At the time there were a number of potential SBC vendors to choose from, but Acme Packet at the time was a pioneer in this space and was considered best of breed and as such the FDA purchased their own SBC equipment and thus maintain License cost and engineering/support since.

The Solution

The FDA White Oak campus, as the center of the agency in the Washington area has a requirement for uninterrupted voice communications services.  The pre-SIP design of the VoIP network at White Oak included a physical infrastructure redundancy and failover for the Call Manager servers and VoIP systems. 

The transport path for access to the PSTN (Public Switched Telephone Network) PRI’s that provide the actual dial tone is a fault tolerant SONET ring that will recover in 30 seconds or less in the event of a fiber cut or failure providing the agency with a high level of survivability.

However, the Beltsville Central Office was a single access to the PSTN.  In order to eliminate this single point of failure Verizon’s SIP Trunking service has been deployed at a more cost effective and as a more operationally efficient solution. 

This was accomplished using an  IP based service (utilizing the existing Verizon Business MPLS network backbone, (known as vBNS+) along with a network based “soft switch” service being installed.

Deployment Architecture

When considering a SIP trunk deployment there are two viable deployment models to choose from which are distributed and centralized. The distributed model distributes connectivity and equipment as each location where the service is utilized. A centralized model pools connectivity and equipment into one or more data centers and allows for efficient usage of resources by more than one location.

The FDA SIP trunking environment is based on the more efficient centralized model with SIP trunk termination into two of the FDA data centers. The centralized deployment allowed the FDA to eliminate many individual Primary Rate ISDN (PRI) circuits and maximize trunk utilization over two MPLS data circuits.

Two Oracle Acme Packet Net-Net 3820 SBC hardware based VoIP security appliances deployed in two datacenters (ADC and WODC) in an Active/Standby Highly Available (HA) pair with capability of up to 8000 sessions per HA pair. Calls are loaded across each of the SBC HA pairs in an active/active fashion ensuring calls are distributed across the each of the data centers. The SBCs monitor all trusted devices and if a device fails to respond as expected, it will be bypassed.

What are the SBCs responsible for in the FDA environment

Every call in and out of the FDA White Oak campus and 2 FDA field locations (Chicago Lisle, Dauphin Island) traverse the SBCs. The SBCs route all calls between the Cisco Unified Call Manager (including the existing WebEx Meeting place bridges), the hosted Interactive Intelligence ACD environment and now an active eFax pilot.

The SBC logically separates traffic by call Domains referred to as Realms. Each realm can be configured
to treat traffic differently depending on the application using that realm. At this time the SBCs are configured the following realms:

  • Verizon – securely terminate the Verizon SIP trunk service
  • Cisco Call Manager – All UC services for HQ (~15,000 end-points including voicemail and 28 buildings) and All audio conference services including cloud WebEx (CCA)
  • Hosted ACD Production – All cloud ERIC call center 40 plus products (HR, IT, Travel, IT calls, FDA info, etc.)
  • Hosted ACD Development/test – Dedicated test environment for new IVR configuration and SW updates.
  • eFax Pilot – Fax transmission over IP delivered to users email inbox.

As a result of this architecture the SBC is the most appropriate location to perform call blocking to reduce inbound/outbound call fraud/hacking attempts and nuisance calls in or out of the FDA. Incoming nuisance calls have been on the rise and requests to block specific numbers has been a frequent request. The SBC rejects the call in such a way that instructs Verizon to terminate the call and not attempt to send the call into the other data center therefor reducing resource utilization.

Outbound calls from the FDA to Verizon must be sent to the appropriate Verizon SIP target or else the call will be rejected. The SBC’s control the routing to Verizon and have been configured to handle normal and redirected calls. This area of the configuration is complex but is easily performed by the SBC software.

By leveraging a feature in the Oracle Acme Packet SBCs the FDA was able to reduce or completely eliminate expensive Cisco hardware based Media Termination Point DSP resources in the router infrastructure. The SBCs monitor the content of the outbound calls destined to the Verizon SIP trunks and the ACD platform and when necessary it will modify the message to change it from a delayed offer of resources to an more standard method of an “early offer”.

Security – A session border controller (SBC) plays a critical role in providing SIP trunking security at the FDA. The SBC acts as an SIP back-to-back user agent (B2BUA) by terminating incoming traffic, performing signaling transformation/manipulation and originating the traffic on the egress when routed to the destination. The SBC provides a secure demarcation point between Verizon and the FDA unified communications applications with the following security features Topology Hiding & Privacy, Access Control, Denial of Service (DoS) Protection, Virus & Worm Protection, Encryption, and Logging, Monitoring & Reporting.