4 Subscriber Sessions in L2-Connected BRAS

Session start

The start of the session is considered to by the DHCPACK response towards the Subscriber, in response to its DHCPREQUEST/DHCPINFORM request. BRAS extracts and stores in its internal UDR database the following information:

Subscriber MAC address

Subscriber IP address

VLAN/QinQ Subscriber identifiers

The information above is used for further "authentication" of any frame received from the Subscriber, as well as during traffic termination/origination.

Session terminating

The Subscriber session is considered to be terminated once the DHCPRELEASE or DHCPDECLINE DHCP requests are received. If the Subscriber session is terminated, the traffic of this Subscriber is no longer handled and goes down to the trash.

Session state

Subscriber session can reside in one of the following three states:

Active: DHCPACK positive response received for the IP address request in the DHCPREQUEST

Closed: DHCPRELEASE/DHCPDECLINE request to release an IP address is received

Unknown: the request to lease an IP address hasn't gone through the FastDPI. Sessions reside in this state when restarting the FastDPI.

BRAS behavior after rebooting

Once the fastDPI starts, the user session state is in an unknown one, as long as there are no DHCP requests from the Subscriber. However, the Subscriber may already have a previously assigned IP address.

Once the fastDPI starts, the user session state is in an unknown one, as long as there are no DHCP requests from the Subscriber. However, the Subscriber may already have a previously assigned IP address.
This can cause the problems in case the network topology will be changed simultaneously with the VAS Experts DPI rebooting, if the Subscriber VLAN/QinQ identifiers has been changed as a result of some Operator's activity.These problems can be fixed by manual editing the UDR using the fdpi_ctrl utility.