Edge and Core Data Center Architecture in Telecom: Understanding vEPC, EBGP-EVPN, and VXLAN Overlay

Introduction: The Shift Toward Virtualized Telecom Networks

Telecom networks are going through some major changes to accommodate 5G, IoT, and cloud-native services. The old-school hardware-based EPC (Evolved Packet Core) systems are giving way to vEPC (Virtualized EPC), which is being rolled out in Edge Data Centers (DCs) and Core Data Centers (DCs) that are spread out.

The diagram we shared shows how control plane and user plane separation (CUPS), overlay/underlay networking, and inter-DC connectivity using EBGP-EVPN are all part of what makes up a modern telecom setup.

In this blog, we’ll dive into each piece to help both telecom pros and enthusiasts get a clear picture of how these next-gen networks work efficiently and at scale.

Edge DC vs. Core DC: Roles in Telecom Architecture

Edge Data Center (Edge DC)

Located closer to users, optimizing for low latency and quick response times.

Houses virtualized network functions (VNFs) like:

vSBC (Session Border Controller)

vPCSCF (Proxy Call Session Control Function)

vSPGW (Serving/Packet Gateway)

vEPDG (Evolved Packet Data Gateway)

These VNFs play a vital role in providing voice, multimedia, and packet data services right where the users are.

Core Data Center (Core DC)

Central hub for control plane components dealing with subscriber management, policy control, and mobility management.

Includes VNFs such as:

vI/S-CSCF (Serving/Interrogating Call Session Control Functions)

vTAS (Telephony Application Server)

vPCRF (Policy and Charging Rules Function)

vHSS (Home Subscriber Server)

vMME (Mobility Management Entity)

Core DC is essential for managing policy enforcement, authentication, and session continuity.

Key Difference:

Edge DC = low-latency tasks (close to users)

Core DC = centralized control & subscriber management

The Role of vEPC (Virtualized Evolved Packet Core)

The vEPC sits at the center of this architecture. It turns traditional EPC functions into virtual ones, letting them run on standard hardware or in the cloud.

Control Plane Functions (vMME, vPCRF, vHSS, vPCSCF): Manage signaling, policy enforcement, and session handling.

User Plane Functions (vSPGW, vEPDG): Deal with actual user traffic to ensure efficient packet forwarding.

CUPS (Control and User Plane Separation): Enhances scalability and flexibility, allowing the user traffic and signaling functions to scale independently.

This division is critical for being ready for 5G, where you’ll need to connect a ton of devices with super-low latency, which calls for a more distributed setup.

Overlay and Underlay Networking in Telecom

Today's telecom data centers are using overlay and underlay networks to tackle the challenges of scalability, multiple tenants, and smooth connectivity across various locations.

Underlay Network

Based on physical connections: VLAN, MPLS-TP, MPLS, and BGP L3VPN.

Forms the foundation for transporting data.

Guarantees reliable connections between Edge DC and Core DC.

Overlay Network

Utilizes VXLAN (Virtual Extensible LAN) to create logical tunnels over the underlay.

Makes it easier to manage multi-tenant settings and allows for flexible segmentation of network services.

Separates service provisioning from the limitations of physical hardware.

Why Overlay/Underlay?

Underlay = reliable transport

Overlay = agility and scalability in services

EBGP-EVPN: The Glue Between Edge and Core

EVPN (Ethernet VPN) with EBGP (External Border Gateway Protocol) enables multi-site interconnectivity connecting Edge DC and Core DC.

EBGP-EVPN extends Layer 2 and Layer 3 services across the WAN.

Efficiently distributes MAC addresses and IP routing.

Ensures seamless subscriber and service mobility among multiple data centers.

Key Benefits of EBGP-EVPN in Telecom:

Streamlined inter-DC traffic management

Simplified routing, easily scalable MAC/IP learning

Cuts down on flooding and speeds up convergence

Facilitates active-active DC connectivity for better resilience

Control Plane vs. User Plane Separation

In this setup, the control plane (signaling) is distinct from the user plane (data forwarding):

Control Plane: Operates across both Edge and Core DC, handling session setups, subscriber authentication, and policy enforcement.

User Plane: Situated primarily at the Edge DC, close to users for speedy data forwarding.

This CUPS model aligns well with 5G network slicing and MEC (Multi-access Edge Computing) scenarios.

Step-by-Step Data Flow in the Architecture

A mobile device connects through RAN to the Edge DC gateway (GW).

User data moves into Edge DC VNFs (vSPGW, vEPDG) for packet forwarding.

Control signals are sent from Edge DC to Core DC VNFs (vMME, vPCRF, vHSS).

Overlay connectivity (VXLAN) guarantees logical service separation.

Underlay transport (VLAN/MPLS) assures stable packet forwarding across the WAN.

EBGP-EVPN takes care of routing and service mobility across Edge-Core links.

This setup ensures optimized latency, smooth mobility, and policy-driven data forwarding.

Key Benefits of Edge-Core vEPC Architecture

Low Latency Services: Edge DC minimizes round-trip delays.

Scalability: Separating overlay and underlay allows for massive scaling.

Resilience: EBGP-EVPN provides fault tolerance and active-active links.

Cloud-Native Readiness: vEPC functions run on standard operating systems or cloud platforms.

5G Preparedness: CUPS and the distributed model meet the needs of 5G core infrastructure.

Quick Comparison Table: Edge DC vs. Core DC Functions

Category Edge DC (Closer to Users)Core DC (Centralized Control)Latency Ultra-low latency, user plane traffic Higher latency tolerated (signaling)Functions vSPGW, vEPDG, vSBC, vPCSCF vMME, vPCRF, vHSS, vI/S-CSCF, vTAS Role Data forwarding, media processing Policy, authentication, session management Scaling User plane scaling Control plane scaling5G Alignment MEC, slicing, user traffic handling Subscriber management, core intelligence

Conclusion: Why This Architecture Matters for 5G and Beyond

The illustrated Edge-Core DC architecture with vEPC, VXLAN overlays, and EBGP-EVPN is fundamental for modern 4G and 5G networks.

By keeping control and user planes separate, deploying VNFs across various sites, and using overlay/underlay networking, operators can provide:

Ultra-low latency services

Resilient and scalable connectivity

Multi-tenancy capabilities

Smooth transition to 5G Core and network slicing

For those in telecom, getting a grip on this architecture is vital as the industry moves toward a fully cloud-native, virtualized, and automated future.