How IPv4 Address Negotiation and Release for Dynamic PPP Subscribers Works in a Subscriber Access Network

You can use on-demand IPv4 address allocation or de-allocation for dynamic dual-stack subscribers.

IPv4 Address Negotiation for Dynamic PPP Subscribers

1. PPP Link Control Protocol (LCP) is established and IPv6 control protocol is successfully negotiated.
2. The broadband network gateway (BNG) receives an Internet protocol Control Protocol (IPCP) Configure Request with a 0.0.0.0 IPv4 address option from the CPE.
3. The BNG sends an Access-Request message with the Unisphere-Ipv4-release-control VSA (if configured) to the RADIUS server.
4. The BNG receives an Access-Accept message from the RADIUS server.
   • If a Framed-IP-Address attribute is received, then a duplicate address check (if configured) is performed on the BNG. If a duplicate address check is completed successfully, then PPP continues IPCP negotiation with the CPE. Otherwise, the entire PPP session is brought down by sending an LCP terminate request to the CPE.
   • If Framed-Pool attribute is received, then the IPv4 address is allocated from the specified local address pool configured in the BNG. If the pool is not configured in the BNG and there is no other IP pool available, then an IPCP protocol reject is sent to the CPE.
   • If neither a Framed-IP-Address attribute nor a Framed-Pool attribute is received, then the BNG allocates an IPv4 address from one of the configured local address pools. If the BNG cannot allocate an IPv4 address, then an IPCP protocol reject is sent to the CPE.
   • If an Access-Reject or Access-Challenge message is received instead of an Access-Accept, then the IPCP protocol reject is sent to the CPE.
   • If there is no response from the RADIUS server, then IPCP should be terminated.
   • If ADFv4 filters are present in the Access-Accept message, then they need to be reinstalled for that subscriber in the BNG.
   • If both IPv4 primary and secondary DNS addresses are present in the Access-Accept message, then both of them need to be updated for that subscriber in the BNG. If either an IPv4 primary DNS address or an IPv4 secondary DNS address is present in the Access-Accept message, then only the corresponding DNS address needs to be updated for that subscriber.
5. The BNG sends an IPCP Configure NACK with the new IPv4 address option to the CPE.
6. The dynamic inet family and local address are added and all IPv4 (family inet) services for the dynamic client profile are instantiated.

   The BNG sends an IPCP Configure Request with a local IPv4 address option to the CPE.

7. The BNG sends an immediate Interim-Accounting message (if configured) with the Unisphere-Ipv4-release-control VSA (if configured) and a Framed-IP-Address attribute to the RADIUS server.
8. All IPv4 services, such as ascend data filters (ADF) and firewall filters, for the dynamic service profile and the lawful intercept service (if present for inet family) are instantiated and the Service Accounting-Start messages (if service accounting is configured and IPv4 service is not part of a multi-family service profile) are sent to the RADIUS server. If service instantiation fails, then IPCP is terminated and an IPv4 address release process is initiated.
9. The BNG receives an IPCP Configure Request with a new IPv4 address option from the CPE.
10. The BNG sends an IPCP Configure ACK to the CPE.
11. The BNG receives a Service Accounting-Start response from the RADIUS server.
12. The BNG receives an Interim-Accounting response from the RADIUS server.
13. The BNG receives an IPCP Configure ACK from the CPE.

IPv4 Address Release for Dynamic PPP Subscribers

1. The BNG receives an IPCP terminate request from the CPE.
2. The BNG sends an IPCP terminate ACK to the CPE.
3. The following actions occur:
   • All IPv4 (family inet) services for the dynamic client profile are de-instantiated and the dynamic inet family and local address are removed.
   • All IPv4 services, such as ascend data filters (ADF) and firewall filters, for a dynamic service profile and the lawful intercept service (if present for inet family) are de-instantiated. The Service Accounting-Stop messages (if service accounting is configured and IPv4 service is not part of a multi-family service profile) is sent to the RADIUS server.
   • If an IPv4 address was allocated from a local address pool, then it is available.
   • The IPv4 address entry is cleared from the subscriber record
4. The BNG sends an immediate Interim-Accounting message (if configured) with the Unisphere-Ipv4-release-control VSA (if configured) to the RADIUS server and the Framed-IP-Address attribute must not be included.

   User Session Statistics and service session statistics for multi-family service are retained for the entire PPP session and is not cleared when the IPv4 address is released.

5. The BNG receives an Interim-Accounting response from the RADIUS server.

   No action taken in the BNG whether or not it receives a response from the RAIDUS server.