About the Senior Core Network Engineer role
A career in senior core network engineering centers on the architectural design, deployment, and optimization of the central nervous system of modern telecommunications: the packet-switched core network. Professionals in these senior roles are the bridge between high-level network strategy and the granular, low-level protocol analysis required to ensure flawless connectivity. They are responsible for the evolution and daily operation of the infrastructure that powers 3G, 4G LTE, and emerging 5G networks, ensuring that millions of subscribers experience high-speed data, voice, and IoT services without interruption.
The primary responsibilities of a Senior Core Network Engineer are deeply technical and strategic. They lead the design and dimensioning of the Evolved Packet Core (EPC) and 5G Core (5GC), focusing on scalability to accommodate relentless data growth. A significant portion of their work involves managing roaming architecture, negotiating with IPX/GRX providers, and establishing direct bi-lateral roaming agreements to ensure global connectivity. They architect the DNS hierarchy for the mobile core, particularly designing S-NAPTR records that allow MME and SGSN nodes to discover critical gateways like PGW, SGW, and UPF. Additionally, they define subscriber profiles within the HSS/UDM, meticulously configuring QoS parameters, APN settings, and AMBR limits for specialized services such as IMS, IoT, and standard internet access.
A core part of the role is deep-dive troubleshooting. These engineers are expected to decode complex signaling procedures across multiple generations of technology, including Iu-PS for 3G, S1-MME and S11 for 4G, and EN-DC for 5G NSA. They must have an expert-level understanding of 3GPP standards to analyze critical data call-flows, including attach/registration procedures (authentication vectors, ULR/ULA) and bearer management (dedicated bearer creation for VoLTE). Proficiency with protocol analyzers like Wireshark is essential for dissecting ASN.1 messages and Diameter signaling protocols (Gx, Gy, S6a, GTP-C, GTP-U). Furthermore, they act as the primary technical interface with network equipment vendors, leading technical evaluations, design reviews, and acceptance testing to validate that new solutions meet stringent operational standards.
Typical skills and requirements for these positions are rigorous. Candidates usually possess a background from a Tier 1 carrier, mobile network operator, or major network equipment provider, with a minimum of three years in a hands-on engineering or architectural capacity. Deep expertise is required in core network nodes like SGSN, GGSN, PGW, HSS, MME, and SGW. A strong command of IP networking—including BGP/OSPF routing, VRFs, and ASN management—is mandatory, alongside expert-level DNS knowledge. As the industry evolves, experience with cloud-native functions, Control and User Plane Separation (CUPS), and 5G Standalone (SA) architecture is increasingly valued. For those seeking senior core network engineer jobs, the role demands a unique blend of strategic planning, hands-on protocol analysis, and vendor management, making it a critical and highly specialized profession within the telecommunications sector.