The High Availability feature ensures the following functionalities for AMF-service:

• No session loss when AMF-service pods get killed or restarted.

• During restart, the AMF-service pods don't:

  • Fail any procedures

  • Increase in call processing time

  • Result in call failure of the retried calls

  • Restart or crash other pods

  • Downgrade the performance

The AMF protocol pod maintains the security context cache, NAS UL, and DL counter information for subscribers. Whenever this information is modified in the cache, the same information gets replicated to the peer protocol pod to ensure high availability.

Note	It is recommended to support a maximum of two protocol pod replicas for high availability. If both protocol pod replicas go down back to back or together, the security context data gets lost.

Typically, the two replicas of protocol endpoint pods are spawned on active-standby mode on different servers to achieve redundancy and resiliency.

The AMF protocol pods determine among themselves who is the leader by using the Etcd for electing a leader. The leader information gets registered in the topology management module in the Etcd. The leader selection upgradation helps with replicating the security context cache to the other AMF protocol pod. If the leader pod goes down, the other (follower) pod becomes active and handles the traffic. The follower pod works with the replicated security context cache, UL, and DL counters from the leader.

The AMF-SCTP and the AMF-service pods query the leader information for the AMF protocol pod before making any IPC call. When the leader pod goes down, the other pod gets selected as a leader and the subsequent IPC request goes to the selected protocol pod.

If a pod comes up, the security context cache gets synced with the peer before the pod becomes ready.

To configure this feature, use the following configuration:

config 
    instance instance-id instance_id 
        endpoint ngap replicas replica_count 
        end 

NOTES:

• endpoint ngap replicas replica_count —Specify the number of NGAP replicas per node.

SCTP uses virtual IP (VIP) to support HA. This feature supports two SCTP endpoints.

The SCTP pod starts and listens on VIP. If one SCTP pod goes down, traffic moves to the other SCTP pod using VIP.

To configure this feature, use the following configuration procedure:

1. Configure the k8 node labels, on which the SCTP pod should run.

   k8 label sctp-layer key smi.cisco.com/node-type value sctp

   Note	The label must have a minimum number of two K8 nodes for active or standby pods to work.

2. Configure the two replicas as active and standby pod for SCTP. The active pod receives the traffic.

   config 
       instance instance-id instance_id 
           endpoint sctp 
               replicas replica_count 
               end 

   NOTES:

   • replicas replica_count —Specify the number of SCTP replicas per node.

3. Configure the VIP for IPv4 and IPv6 using the following commands:

   config 
       instance instance-id instance_id 
           endpoint sctp 
               vip-ip ipv4_addressoffline { vip-interface interface_name | vip-port port_number } 
               vip-ipv6 ipv6_address { offline  | vip-ipv6-port ipv6_port_number } 
               end 

   NOTES:

   • vip-ip ipv4_address [ offline | vip-interface interface_name | vip-port port_number ] —Specify the IPv4 address of the pod on which VIP is enabled, interface, and the port number. This configuration marks VIP-IP as offline (standby).

   • vip-ipv6 ipv6_address [ offline | vip-ipv6-port ipv6_port_number ] —Specify the IPv6 address of the pod on which VIP is enabled. This configuration marks VIP-IP as offline (standby) if you specify as offline.