The Nokia router’s class-based forwarding feature applies to a set of LSPs that are part of the same SDP. Each LSP must be configured as part of an SDP specifying the forwarding classes it supports. A forwarding class can only be assigned to one LSP in a specific SDP, meaning that only one LSP within an SDP supports a specific class of service. However, multiple classes of services can be assigned to an LSP. Both RSVP and static LSPs are allowed. All subclasses are assigned to the same LSP as the parent forwarding class.
When a service packet is received at an ingress SAP, it is classified into one of the eight forwarding classes. If the packet leaves the SR on an SDP that is configured for class-based forwarding, the outgoing LSP is selected based on the packet's forwarding class. Each SDP has a default LSP. The default LSP is used to forward a received packet that was classified at the ingress SAP into a forwarding class for which the SDP does not have an explicitly-configured LSP association. It is also used to forward a received packet if the LSP supporting its forwarding class is down.
Class-based forwarding can be applied to all services supported by the Nokia routers. For VPLS services, explicit FC-to-LSP mappings are used for known unicast packets. Multicast and broadcast packets use the default LSP. There is a per-SDP user configuration that optionally overrides this behavior to specify an LSP to be used for multicast/broadcast packets.
VLL service packets are forwarded based on their forwarding class only if shared queuing is enabled on the ingress SAP. Shared queuing must be enabled on the VLL ingress SAP if class-forwarding is enabled on the SDP the service is bound to. Otherwise, the VLL packets are forwarded to the LSP which is the result of hashing the VLL service ID. Because there are eight entries in the ECMP table for an SDP, one LSP ID for each forwarding class, the resulting load balancing of VLL service ID is weighted by the number of times an LSP appears on that table. For instance, if there are eight LSPs, the result of the hashing is similar to when class based forwarding is disabled on the SDP. If there are fewer LSPs, then the LSPs which were mapped to more than one forwarding class, including the default LSP, have proportionally more VLL services forwarding to them.
Only user packets are forwarded based on their forwarding class. OAM packets are forwarded in the same way as an SDP with class-based forwarding disabled. In other words, LSP ping and LSP trace messages are queued in the queue corresponding to the forwarding class specified by the user and are forwarded over the LSP being tested. Service and SDP OAM packets, such as service ping, VCCV ping, and SDP ping are queued in the queue corresponding to the forwarding class specified by the user and forwarded over the first available LSP.
Class-based forwarding is not supported for protocol packets tunneled through an SDP. All packets are forwarded over the default LSP.
Class-based forwarding is not supported on a spoke SDP used for termination on an IES or VPRN service. All packets are forwarded over the default LSP.