From 2014–2015, annual traffic growth reached 50%. During the pandemic, demand spiked so sharply that all channels were fully loaded. This experience drove the search for new solutions to scale and increase network efficiency.
Challenges
The key challenge for Sarkor was IPv4 address scarcity. The company was forced to purchase IPv4 pools at high prices or lease addresses from other operators. For example, purchasing 10,752 and leasing 10,240 IPv4 addresses made it clear that alternatives were needed. Management set the following goals:
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Optimize IPv4 address usage through NAT;
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Prepare infrastructure for IPv6 (Dual-Stack);
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Retain the flexibility of the existing architecture built on in-house developments;
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Reduce CAPEX and OPEX compared to traditional solutions from large vendors.
Solution
Sarkor’s first introduction to VAS Experts products was in 2020, when a DPI solution was deployed to optimize external uplink channels. The project provided positive experience with traffic prioritization, though it was temporarily put on hold. Later, in line with the company’s philosophy of favoring software over hardware from Cisco and Juniper, the Stingray Service Gateway (SSG) with CG-NAT functionality on x86 servers appeared to be a highly promising option — especially for IPv4 address savings and IPv6 readiness. The company also already had significant positive experience with software-based deployments.
As a result, Sarkor gained:
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Full Cone NAT: seamless operation of P2P protocols and online games;
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Paired IP address pooling: subscriber sessions tied to a single external IP address;
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Hairpinning: local subscriber traffic exchange without translation;
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Limits: configurable TCP/UDP session limits per NAT pool;
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NAT record export: to text files or NetFlow v10;
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Seamless integration with existing processes;
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No more IPv4 rentals — eventually leasing out its own address pools.
Address density (ratio of public to private IPv4 addresses) also proved comfortable. Following VAS Experts’ recommendation, Sarkor set a 1:8 ratio, which preserved headroom for subscriber growth.
The next stage was migration to BNG and the VAS Experts router.
Previously, Sarkor used a custom-built BNG solution as well as a legacy PPPoE scheme. During migration, the company’s engineers developed their own RADIUS server, compatible with both the new BNG and the existing billing system. Dual-stack (IPv4 and IPv6) support was also enabled. Subscriber channel policing became especially valuable for designing tariff plans. Prior experience helped efficiently implement traffic prioritization by protocol signatures and AS.
The use of the BIRD software router directly within the SSG preserved routing flexibility, allowing dynamic advertisement of subscriber subnets via both BGP and OSPF. Importantly, it also preserved internal resources and customer-facing services. Configuration and integration caused no issues, since a similar software router had already been deployed and successfully used in the network.
Additionally, an IPoE segment outside billing was preserved for corporate clients and banks (around 200 customers) that require internet access independent of billing status.
Results
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IPv4 savings. CG-NAT eliminated the need for costly purchases or leases of additional address pools.
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Redundancy. The network architecture now runs on two physical domains, each with four BNGs. Within each domain, two logical segments are implemented. Failover works in active-active mode with manual intervention: in case of failure, engineers redistribute the load to backup BNGs. Despite requiring manual switching, downtime is minimal and not critical.
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Reliability. After migrating to its own data center, a hardware issue was detected on one BNG. VAS Experts engineers promptly restored operation by replacing the network card and rebuilding DPDK.
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Regulatory compliance. A pre-filter for preliminary traffic filtering in accordance with local law was deployed. The solution successfully passed regulator checks and “saved the 2021 budget.”
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Flexibility. All key services were launched “in a single box” with no extra points of failure, fully aligning with the company’s internal philosophy.
Development Plans
The next stage of growth is regional expansion. The company plans to build mini–data centers in key locations across the country and deploy BNGs there, minimizing backbone traffic and improving service quality for customers outside Tashkent.
Customer Feedback
We have always focused on software solutions, used to flexibility and in-house development. The VAS Experts solution turned out to be perfectly aligned with our philosophy: everything in one box, with no extra points of failure. CG-NAT and BNG fully met our expectations and even exceeded them. Today, we confidently look to the future and prepare for regional expansion.
— Shukhrat Ishmatov, Head of IT Department, Sarkor
