IBCP

Most BNG session types have one or more control plane messages that are sent in-band and therefore arrive directly on the UPF. Because the BNG UPF cannot handle these messages, they are forwarded to the BNG CPF. To accomplish this, the BNG CPF installs specific Ethernet or IP filter rules that match these packets; for example, by matching UDP destination port 67 to extract DHCP. These packets are encapsulated in GTP-U and sent to the CPF. Similarly, the BNG CPF sends downstream In-Band Control Plane (IBCP) packets over GTP-U toward the BNG UPF.

For upstream traffic, the BNG UPF sends any control plane messages that do not match a session over a default tunnel. See Default IBCP session for information about how this tunnel is signaled. If the control plane messages do not match the default tunnel rules, the messages are dropped.

When a session is created, either out-of-band or via a trigger over the default tunnel, the BNG CPF installs per-session control plane rules for both upstream and downstream. Packets that match the upstream rules are forwarded to the BNG CPF using the signaled GTP-U parameters. For downstream rules, the BNG UPF allocates a TEID that the BNG CPF can use to send packets. The BNG UPF does not support a default downstream IBCP tunnel.

The upstream IBCP (including default) follows the sgt-qos dscp application configuration, using the ibcp keyword on the router or VPRN. A specific DSCP value (default NC2) can be provisioned and mapped to a specific FC, as usual.

See the 7450 ESS, 7750 SR, 7950 XRS, and VSR Quality of Service Guide, section "QoS for Self-Generated (CPU) Traffic on Network Interfaces" for more information.

Downstream IBCP packets are handled directly in the data path. Ingress QoS is applied based on the provisioning. Egress QoS depends on the session type. The session types are as follows:

Parent topic: Session management