Application of HVPN on an IP RAN

Service Overview

As 3G and Long Term Evolution (LTE) services develop, mobile operators keep building and expanding RANs. This situation imposes high requirements on the bandwidth, scalability, and configuration flexibility of the IP RAN between base transceiver stations (BTSs)/NodeBs/eNodeBs and base station controllers (BSCs)/radio network controllers (RNCs)/mobility management entities (MMEs). IP datacom networks, as the mainstream of datacom networks, are large in scale and provide a variety of access modes. To maximize carriers' return on investment, reduce network construction costs, and evolve the existing network smoothly to an LTE network, an IP RAN solution is introduced.

In the HVPN bearer solution, the RAN provides excellent fixed-mobile convergence (FMC) capabilities and has simple and flexible networking. The hierarchical network between CSGs and radio service gateways (RSGs) can bear various types of services.

Networking Description

As shown in Figure 1, the HVPN bearer solution involves three types of devices:

CSG: On an HVPN, CSGs function as UPEs to provide access services for BTSs/NodeBs/eNodeBs.
Access service gateway (ASG): On an HVPN, ASGs function as SPEs to provide access services for UPEs.
RSG: On an HVPN, RSGs function as NPEs to connect to BSCs/RNCs/MMEs.

Figure 1 Networking diagram for the HVPN bearer solution

Feature Deployment

The HVPN bearer solution applies to large-scale networks with dynamic routing capabilities. Table 1 uses an HoVPN bearer solution as an example to describe feature deployment for E2E Ethernet service bearer and protection.

**Table 1** Feature deployment in an HoVPN bearer solution
Feature	Description
Service	LTE S1/X2 3G Eth
IGP	IGP multi-processes must be deployed between CSGs and RSGs to ensure proper data forwarding. A routing policy needs to be configured on ASGs to aggregate and filter routes. This configuration reduces bandwidth requirements for updating and maintaining routes. Recommended routing protocol: IS-IS multi-processes
MPLS tunnel	MPLS tunnels must be established between CSGs and ASGs, and between ASGs and RSGs. Recommended tunnel protocol: MPLS TE (tunnel selectors must be configured)
VPN	Hierarchical L3VPN must be configured between CSGs and ASGs, and between ASGs and RSGs to isolate services.
Protection switching	Protection switching must be configured for nodes and links to provide high availability: BGP tracking must be enabled network-wide to speed up IBGP route convergence. The ConnectRetry interval for re-establishing neighbor relationships must be prolonged between a CSG and the master ASG. VPN FRR must be configured on CSGs, ASGs, and RSGs. MPLS TE hot standby and BFD for TE CR-LSP must be configured to protect links between devices.
QoS	E2E QoS must be configured between CSGs and RSGs to ensure service quality. Recommended QoS solutions: DiffServ
Clock synchronization	E2E clock synchronization must be configured between CSGs and RSGs to ensure real-time data transmission. Recommended clock synchronization technologies: synchronous Ethernet and 1588v2