Carrier case study: Arelion begins converging its IP and optical network layers

Arelion has taken another step in converging its IP and optical layers by adding Cisco 400G Quad Small Form Factor Pluggable Double Density (QSFP-DD) Bright Optical Modules in its production IP backbone. The first regional reach deployment spans 675 kilometers between Stockholm and Copenhagen over a third-party Optical Open Line System (O-OLS).

After conducting rigorous testing and what it said were “successful” trials, this deployment accelerated Arelion’s plans to provide customers with cost-optimized performance and capacity. The provider said it streamlines the overall network architecture, improves energy efficiency, and ensures a more efficient expansion process.

Cisco 400G QSFP-DD Bright Optical Modules, with greater than +1 dBm transmit power, simplify integration with brownfield and greenfield deployments. The streamlined architecture eliminates the need for excessive hardware, thereby reducing potential points of failure. As a result, Cisco claims it can achieve 64% capital and 76% operational savings. This contributes to a more cost-efficient network with fewer interfaces to control and maintain.

The Cisco 400GBASE Quad Small Form-Factor Pluggable Double Density (QSFP-DD) portfolio offers various high-density transceiver modules and the flexibility of 400GigE connectivity options for data center, high-performance computing networks, enterprise core and distribution layers, and service provider applications. The QSFP-DD modules are Cisco’s latest generation of 400G transceiver modules based on a QSFP-DD form factor.

Arelion is finding several use cases with the Cisco technology. The first is to expand business inside a city to pick up traffic in more locations.

“Instead of telling a customer you have to be in this data center to use our services, we can tell them you can be any of these five data centers because we can easily transport data with this technology,” said Mattias Fridström, chief evangelist for Arelion. “Before this, you needed metro DWDM equipment.”  

The provider can also replace expensive optical transponders in the optical network by using the plugs in the routers directly. “There are two different business cases, but both will be applied and dramatically reduce our costs,” Fridström said.

IPoDWDM connection

The motivation to adopt Cisco’s platform was driven by Arelion’s desire to integrate its IP and optical network infrastructure.

Before the service provider enhanced its network, Arelion’s IP backbone was separated from the optical network. This meant that 50% of the production network went into the optical network and the other went into serving wholesale service customers.

Traditionally, a provider would send the internet traffic from the router to the optical gear to the other side.

Fridström said that the advent of 400G Ethernet changed the equation. “When 400G Ethernet almost became identical to normal transport capacity, it became possible to install the laser in the plug of the router,” he said. “You can then shoot the directly from the router to the optical layer to another router somewhere.”

Being a global provider, Arelion aims to connect all its routers throughout its locations. The provider can now remove the optical layer between the routers.

Specifically, the provider’s adoption of 400ZR, an ethernet-based fiber networking standard designed for transmitting 400G speeds at least 80 km distances, is critical in this network transition.

“The 400G ZR was built for short distances of 20-30 kilometers,” Fridström said. “When you have a router in a data center in the inner city of London and another router in the city of London, you want to shoot traffic between each router.”

This technology has been in Arelion’s network for two years in most European cities and some in the United States.

Being able to carry traffic at longer distances with less power is critical. “Having the laser pluggables is much better than it was before because it enables longer distances and higher output power,” Fridström said. “Instead of having 10 db of power, it has 0 or plus-1 db.”

Reducing costs

Another benefit of the IPoDWDM technology is reducing network operation costs and greater efficiency in transporting traffic within its network.

For example, with the traffic in London and Paris, Arelion would send it to the DWDM equipment in London. Then, the traffic would be dropped into a router in Paris. “What we can do now with the latest technology from Cisco/Arista, and others are doing this, we can shoot traffic from a router directly from London and Paris,” Fridström said.

Today, the service provider uses the Cisco platform to transmit traffic between Stockholm and Copenhagen because of the demand in these markets. Because it can eliminate the middle layer and not purchase another optical transponder, Arelion can save 64% on capex.

“There’s no point of sending that traffic over the existing DWDM system if you can just use the traffic between the routers,” Fridström said. “You still need the DWDM amplifiers, but removing the transponders can save much money.”  

Since half of Arelion’s optical footprint is used for IP transport, Fridström added, “there’s an opportunity to lower the cost of backbone services by removing a part of the optical layer and shooting traffic between the routers.”

Initially, it tested the platform on a route between Hamburg and Copenhagen. Following the trial's success, the provider plans to implement the technology platform in other parts of its network.

“A perfect way for us to either replace existing traffic with cheaper ways of carrying traffic or expand the networks to new locations without having to buy optical transponders, we just have to buy the amplifiers,” Fridström said. “This is a way for us to be more efficient and meet future customer price points.”

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