RETN opens resilient Tallinn-Cēsis Baltic backbone link

RETN has launched a new terrestrial internet backbone route between Tallinn, Estonia, and Cēsis, Latvia, adding an additional path on a corridor that carries traffic between Northern and Central Europe.

The route was put through an early live test during pre-service work when a fibre break disrupted the primary path in late 2025. Engineers shifted traffic onto the new Tallinn-Cēsis line and restored multiple backbone channels within an hour.

The incident affected more than 40 DWDM backbone channels across several European segments, according to RETN. Key performance indicators, including latency and jitter, stayed within expected levels during the reroute.

Physical fibre faults can take a long time to resolve, particularly when restoration depends on field repairs. RETN contrasted the hour-long reroute with longer restoration times that can occur in Layer 1 environments when organisations wait for physical repairs, sometimes taking days, and potentially longer in subsea situations.

Route Expansion

The Tallinn-Cēsis link is part of RETN's wider network expansion programme, focused on increasing route and supplier diversity between Northern and Central Europe. The aim is to improve backbone resilience by adding alternative terrestrial routes that can carry traffic when a primary path fails.

From a network design perspective, additional terrestrial paths reduce reliance on a single fibre provider or physical corridor. This is particularly important on busy north-south and east-west routes, where a fault can affect multiple services at once.

The new route adds another terrestrial path between Northern Europe, including Finland and the Nordics, and Central Europe, while reducing dependence on a single fibre supplier.

Tallinn Presence

The expansion also includes a new core point of presence in Tallinn at Greenergy Data Centre, enabling RETN to deliver its full portfolio of network services locally.

Points of presence are physical sites for network equipment and interconnection, often located in data centres where operators can connect to other carriers, cloud platforms, and enterprise networks. A core site typically supports backbone routing and transport rather than only local access connections.

Capacity Headroom

The Tallinn-Cēsis line adds up to 40TBps of capacity and includes new DWDM spectrum. RETN positioned the additional headroom to support future growth and expedite rerouting during disruptions.

DWDM increases the capacity of fibre by transmitting multiple optical channels at different wavelengths. It allows operators to scale backbone capacity without building entirely new physical routes, although new fibre builds remain important for physical diversity.

Operational Lessons

RETN said the live incident during pre-service work validated the new build's operation and reinforced the need for alternative routes that engineers can use quickly in the event of a physical failure.

Backbone operators often plan for failures as routine events, particularly in regions where construction activity, weather, and third-party damage can affect terrestrial fibre. A new route can also expand traffic engineering options as teams balance latency targets, available capacity, and commercial constraints on leased infrastructure.

Tony O'Sullivan, CEO of RETN, said: "Modern backbone networks have to be engineered on the assumption that outages are inevitable; therefore, the network design should be resilient from the start."

"The Tallinn-Cēsis route was built as part of a deliberate resilience strategy-adding diversity at both the route and supplier level-so that when a failure occurs, traffic can be shifted quickly without compromising performance."

RETN operates a Eurasian network spanning Western and Eastern Europe and Central Asia, with onward connectivity towards Southeast Asia. The company runs optical transport and IP/MPLS infrastructure across its footprint and sells telecommunications services over that network.

Further backbone builds across Northern and Central Europe remain part of the expansion programme. The Tallinn-Cēsis route is now in service as an additional terrestrial option on the Baltic corridor.