Telecom Network Engineer (SS7 / SMSC)

About the role

Most "SMS API" companies are a thin REST surface in front of a single upstream intermediary. We are not. DogeSMS is moving up the stack — first as a CLEC-style direct operator in North America (ISP Telecom on the +1 footprint), then through additional licensed footholds in Europe and APAC. That means owning the actual signalling and message-transit layers, not just the customer-facing API. This role sits at that boundary. The day-to-day is unglamorous in the way that real telecom work is unglamorous: SS7 / SIGTRAN over M3UA for legacy interconnects, SMPP 3.4 / 5.0 toward operator SMSCs, Diameter for LTE / 5G-NSA charging and routing, GSM MAP for MO / MT-SMS at the application layer, and the boring but mandatory parts — HLR / HSS subscriber lookups, SCCP global title translation, MAP-PhaseN compatibility quirks, MNP (number portability) dips. You will design and operate the integration between our Go message-pipeline and the carrier-grade signalling stack (commercial or open-source — Mavenir, RestComm jSS7, Kannel, OpenBSC heritage code), make sure the signalling interconnects stay up across maintenance windows, and explain to backend engineers why "just retry the SMPP submit" is a category error. This is a hire for someone who has actually worked at a carrier, MVNO, or signalling-as-a-service operator — not someone who has only read the specs. We do not need ten of these. We need one who is unmistakably the person to call.

What you'll do

• Own DogeSMS's signalling-layer architecture across SS7 / SIGTRAN (M3UA, SCCP, TCAP, MAP) and Diameter (S6a/d, Gy/Ro for LTE/5G-NSA), including capacity planning for SMSC throughput and HLR query rates.
• Run the SMPP termination fleet: bind-receiver / bind-transceiver lifecycle, throughput pacing, DLR (delivery receipt) correlation, and integration with the Go pipeline's order state machine.
• Operate our MAP-layer interface for MO-SMS (Mobile Originated) reception on the ISP Telecom +1 footprint — windowing, MAP-PhaseN negotiation, abort-handling for malformed TCAP dialogues.
• Design the GSM / LTE / 5G NSA roaming and number-portability (MNP) dip strategy: when to consult an HLR / HSS, when to use a third-party dip service, how to cache without burning operator goodwill.
• Partner with the Go backend team on the wire-protocol boundary: define internal contracts between the signalling stack and the order pipeline, instrument every PDU class with OpenTelemetry, drive postmortems when packet-level pathology shows up as user-visible failure.
• Lead the technical conversation with new carrier and signalling-stack counterparties — what does their SMSC support, which MAP phase, what Diameter AVPs are mandatory, how do they handle SMS over IMS (SIP MESSAGE / SMSoIP).

What we expect

• 7+ years inside the actual telecom industry — at a Tier-1 MNO, an MVNO with a real signalling stack, an SMSC platform builder (Mavenir / Sinch / Comviva / Mobixell), or a signalling-as-a-service operator (NetNumber, iconectiv, Tata Communications).
• Hands-on operational experience with at least three of: SS7 over SIGTRAN (M3UA), GSM MAP, SMPP 3.4 / 5.0, Diameter, SIP / SMS over IMS. Spec-only knowledge does not count — we will ask about quirks that only appear in production.
• Working comfort with HLR / HSS, SCCP global title translation, GSM short-message routing, and number-portability dips against operator-specific NP databases.
• Linux fundamentals (tshark / Wireshark with SS7 dissectors, perf / bpftrace for kernel-side debugging, systemd for production daemons). You are not afraid of legacy stacks written in C or Java that pre-date your tenure.
• Calm demeanor on signalling incidents — when a Diameter peer flaps at 3AM you do not panic, you read the connection trace and you know what AVP went wrong.
• Bonus: regulatory familiarity with EE / LT / EU CLEC licensing, GSMA IR.74 / IR.71 messaging interop, or Canadian CLEC obligations (we have an ISP Telecom partnership in flight that hits all three).

Stack we use

SS7 / SIGTRAN signalling: commercial implementations (Mavenir, NetNumber) and/or open-source heritage (RestComm jSS7, OpenSS7, Kannel for SMPP / WAP termination). SMPP termination toward carrier SMSCs over TLS where supported. Diameter for LTE/5G-NSA via commercial stacks (sm9s, freeDiameter). The Go backend speaks to this layer over well-defined internal RPC — you own the contract on the signalling side, the Go team owns it on the pipeline side. OpenTelemetry per PDU class, SigNoz dashboards, Lark on-call for signalling incidents. No "let's rewrite SS7 in Rust." No greenfield-or-bust attitude. The whole point of this lane is that telecom is a 40-year-old discipline and our job is to interoperate with it correctly, not to declare it obsolete.

Compensation

$70,000–$150,000 USD annually. Real signalling engineers in Tallinn and Vilnius are a small, specialized labor market — the upper band reflects that scarcity and is reserved for someone with named SS7 / Diameter production experience at a Tier-1 carrier or signalling-platform builder. Pay is in USD, structured as either Estonian / Lithuanian employment with full local benefits or USD contractor invoice depending on your situation. Equity available for full-time hires. We cover certification fees for relevant industry training (GSMA, Mobileum, Mavenir certifications).

Hiring process

1. Submit via the talent pool form linked on /careers/openings/telecom-network-engineer. One paragraph on the most operationally painful signalling incident you have personally resolved — what protocol, what symptom, what root cause, what the fix was.
2. 60-minute technical conversation with a co-founder + an external advisor we work with from the carrier side. We will trade pcaps and ask you to walk us through what is wrong with one.
3. Paid scoped exercise ($400 USD): given a representative SMPP / MAP scenario, sketch the integration architecture with our Go pipeline and identify three failure modes you would instrument first. Scoped to one calendar week, ~6 hours of effort.
4. 2-week paid trial project ($1,200 USD): a real piece of the ISP Telecom integration work — we deliberately do not gate this behind theatre; you get a real ticket and we observe how you think through it.

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