There are several options to connect subscribers to the network: with or without session establishment. Many telecom operators already use the PPPoE as a protocol for establishing sessions. Another protocol that is gaining popularity in broadband access networks is the DHCP / IPoE protocol. Each of the protocols has its own advantages and disadvantages, therefore, when choosing a single service model, these points should be taken into account. PPPoE has more advanced authentication mechanisms comparing to DHCP, and DHCP is less sensitive to connection failures. PPPoE has on-board keepalive mechanisms for detecting problems in the session. DHCP allows subscribers to access the operator services without additional client equipment settings. In order to identify users, in the case of PPPoE, explicit names are used that are sent by users, and in the case of DHCP, option 82 is used. In both cases, the RADIUS mechanism is used for authentication.

Service Delivery Model
One of the fundamental points is the principle of distributing virtual LAN networks at the access level. The most common in today’s networks is the Shared VLAN approach. Each service has its own separate VLAN, and each user subscribed to the service has an access to it. The main advantage of using this approach is the simplicity of its implementation. The disadvantages include problems with controlling the interaction of subscribers with each other, the inability to provide a personalized SLA service for each subscriber. These requirements are enough to refuse this approach when building an access network.

The next approach is a model with the allocation of VLANs per subscriber (Customer VLAN) and provisioning of all services to the subscriber in one VLAN. In this approach, you can clearly identify the subscriber by the VLAN number. All subscriber services are authenticated in one place – on BRAS / BNG. This approach imposes additional requirements on aggregation equipment and BRAS / BNG devices regarding the use of Q’n’Q technology.

The final approach is to allocate a separate VLAN for each individual service (S-VLAN). The advantage of this approach is the access control and SLA provisioning. However, it requires manual configuration of a large number of subinterfaces on BRAS / BNG. The CPE device must support 802.1q technology. Access devices must support DHCP option 82.

Among the models of access provisioning, the C-VLAN model is optimal. Moreover, each service within a single VLAN is provided with a guaranteed level of service due to the hierarchy of the quality of service mechanism.

Despite the differences in PPPoE and DHCP / IPoE protocols, the existing network should provide the ability to connect subscribers in both cases. This will allow an operator to expand the portfolio of services provided and ensure customer loyalty.

BRAS/BNG Fault Tolerance
To ensure fault tolerance, it is recommended to use a circuit with redundant devices and power supplies.

Supported Functionality
RADIUS server for managing subscriber sessions;
Automatic creation of VLAN subinterfaces for the first incoming packet;
IPoE subscriber sessions (IPv4 / IPv6 *);
DHCP subscriber sessions (IPv4 / IPv6 *);
PPPoE subscriber sessions;
DHCP Relay (IPv4 only);
DHCP Relay Proxy (IPv4 only);
DHCP Local Server (IPv4 / IPv6 *) (in a virtual container);
Processing DHCP Option 82;
Time quotas allocation;
IP Demux interface;
Protection of Control Plane against attacks by ARP and DHCP packets (IPv4 only);
Tracing IPoE subscribers by MAC and IP addresses;
Tracing individual DHCP subscriber sessions;
Tracing RADIUS messages for a given subscriber;
Support for local HTTP Redirect server;
GRE support for implementing HTTP Redirect on an external server;
Creation of service profiles locally and their assignment to subscriber sessions statically or via the RADIUS protocol;
RADIUS CoA support;
QoS at VLAN level, H-QoS *.
* Available soon