We are seeking a highly technical, hands-on Senior Voice Engineer to join our Unified Communications and Collaboration (UC&C) Solution Engineering team. Reporting to the Voice Team Lead, this individual contributor will serve as a principal-level subject matter expert for enterprise voice and SIP signaling, with solid working knowledge of the network infrastructure that carries it. This role is focused on deep technical execution rather than people management. The engineer will design, secure, and troubleshoot complex voice environments, owning the hardest Tier 3/Tier 4 escalations involving SIP dialog analysis and advanced call flows, and partnering with the dedicated LAN/WAN, Virtualization, and Cybersecurity teams when issues cross into their domains. The position is also accountable for verifying that voice and UC systems meet DISA Security Technical Implementation Guide (STIG) requirements. This position supports multiple DoD contracts and serves as a cross-program technical authority for voice engineering. As a Level T5 engineer, the incumbent will influence solutions that affect strategic goals and business results across those programs, recommend and develop technical standards that are reused from contract to contract, and guide the technical work of other engineers. The position will work closely with Transport Engineering, Network Operations, Cybersecurity, program leadership, customers, and vendor partners. Key Responsibilities SIP Signaling and Advanced Call-Flow Troubleshooting SIP Dialog Analysis: Serve as the senior escalation point for complex voice incidents, analyzing complete SIP dialogs (INVITE, provisional and final responses, ACK, re-INVITE, UPDATE, PRACK, REFER, BYE) to isolate signaling failures across multi-hop call paths. Advanced Call Flows: Troubleshoot and resolve issues in complex scenarios, including attended and blind transfers, call forking, hunt and pilot groups, conferencing, call park, shared lines, simultaneous ring, emergency calling, and cloud/hybrid routing through multiple Session Border Controllers (SBCs). Media and SDP Negotiation: Diagnose offer/answer and codec negotiation failures, early media, DTMF (RFC 2833/4733 and SIP INFO) mismatches, SRTP key exchange problems, one-way and no-way audio, and media anchoring or bypass issues. Header and Normalization Analysis: Interpret and manipulate SIP headers (Via, Contact, Record-Route, P-Asserted-Identity, Diversion, History-Info, Session-Expires) and develop SBC message manipulation and normalization rules to resolve interoperability problems between carriers, call-control platforms, and cloud services. Diagnostic Tooling: Use Wireshark/TShark, SBC debug and trace tools, call-control platform traces, call-detail records, and ladder diagrams to reconstruct call flows and document root cause. Root-Cause Analysis: Deliver written root-cause analyses with permanent corrective actions, and feed lessons learned into design standards and operating procedures shared across supported contracts. STIG Compliance and Voice Security STIG Compliance Checking: Perform and document compliance assessments of voice, UC, and SBC systems against applicable DISA STIGs and Security Requirements Guides (SRGs), including the Voice/Video Services Policy STIG and vendor-specific STIGs. Scanning and Validation: Use DISA STIG Viewer, Security Content Automation Protocol (SCAP) Compliance Checker, Evaluate-STIG, and authenticated vulnerability scans to produce and maintain STIG checklists (.ckl/.cklb) and validate findings. Remediation: Develop and implement remediation for open findings, harden configurations, and build secure configuration baselines that remain compliant through upgrades and changes. Authorization Support: Provide voice-specific technical input to the Cybersecurity team for Risk Management Framework (RMF) packages, POA&Ms, and Authority to Operate (ATO) activities, including justification for deviations and mitigations. Secure Signaling and Media: Implement and troubleshoot SIP over TLS, mutual TLS, SRTP, certificate and PKI management, and secure trunking to carriers and cloud platforms. Layer 2 and Layer 3 Networking for Voice (in partnership with LAN/WAN teams) Layer 2 Switching: Apply working knowledge of voice VLANs, 802.1Q trunking, Spanning Tree, LLDP-MED/CDP, Power over Ethernet, and 802.1X/MAB to troubleshoot endpoint registration and call-quality issues, and define voice requirements for the LAN team. Layer 3 Routing: Understand routing behavior (static, OSPF, EIGRP, BGP, HSRP/VRRP, ACLs) well enough to identify when routing or asymmetric paths are breaking signaling or media, and provide clear evidence to the WAN team for resolution. NAT, Firewall, and Traversal: Resolve SIP and RTP traversal issues at SBC demarcation points, and specify firewall, NAT, and port requirements for voice to the network and security teams. QoS: Define voice and video QoS requirements (DSCP and CoS marking, trust boundaries, call admission control) and validate end-to-end QoS behavior with the LAN/WAN teams. Network Performance Analysis: Isolate packet loss, jitter, latency, and MTU issues affecting voice using packet captures, interface statistics, and call-quality metrics. Voice Platform Engineering and Delivery Design Authority: Author and review high- and low-level designs, implementation procedures, test plans, and rollback plans for voice and UC solutions, and approve designs produced by other engineers. Platform Architecture: Architect and integrate IP telephony, SIP trunking, and SBC platforms, including Cisco Unified Communications Manager, Cisco CUBE, AudioCodes Mediant, and Ribbon SBC, and establish reference configurations reused across contracts. Dial Plans and Routing: Architect enterprise dial plans, E.164 normalization, digit manipulation, route patterns, and carrier and PSTN interconnections. Cloud Voice Integration: Design integrations with Microsoft Teams Phone (Direct Routing and Operator Connect), Webex Calling, and comparable cloud platforms. Technical Guidance: Mentor and guide the technical work of other engineers through design reviews, peer review of configurations, and knowledge transfer, and recommend new standards and solutions to the Team Lead. Vendor and Carrier Escalations: Lead technical engagements with manufacturers, carriers, and SIP service providers on complex defects and interoperability issues. Cross-Program Technical Authority Multi-Contract Support: Serve as the voice engineering subject matter expert for multiple DoD contracts, prioritizing technical work across programs with the Team Lead. Standardization: Develop common voice architectures, STIG-compliant baselines, and SIP normalization standards that can be applied consistently across contracts and customers. Strategic Input: Contribute to technical roadmaps, modernization strategies, and capture or proposal efforts, including solution designs, bills of material, and level-of-effort estimates. Customer and Leadership Engagement: Brief program managers, government customers, and executive leadership on technical risks, recommendations, and solution tradeoffs that affect program goals. Required Experience and Education Education and Experience: Bachelor's degree and 12 or more years of relevant experience, or a Master's degree and 10 or more years, in VoIP, enterprise telephony, unified communications, network engineering, or a closely related discipline. Additional relevant experience and certifications may be considered in lieu of a degree. Clearance: Active Secret clearance required to be considered. DoD 8140/8570 Compliance: Ability to obtain an IAT Level II certification (e.g., CompTIA Security+ CE) within the period required by the contract. SIP Expertise: Expert-level, hands-on experience analyzing SIP dialogs and SDP negotiation in packet captures and platform traces to resolve complex, multi-hop call-flow failures. STIG Compliance:

NEN Solution Engineering – Senior Voice Engineer