The IPv6 header includes a new field that is not found in the IPv4 header, called the flow label. The flow label in IPv6 is used to identify packets that require special handling by routers for quality of service (QoS) or other reasons, allowing these packets to be handled efficiently as they move through the network.
References
Juniper Networks Technical Documentation on IPv6
IPv6 Header Fields - Juniper Networks

To configure filter-based forwarding, perform the following tasks: Create a match filter on the ingress device. To specify a match filter, include the filter filter-name statement at the [edit firewall] hierarchy level. A packet that passes through the filter is compared against a set of rules to classify it and to determine its membership in a set. Once classified, the packet is forwarded to a routing table specified in the accept action in the filter description language. The routing table then forwards the packet to the next hop that corresponds to the destination address entry in the table. Create routing instances that specify the routing table(s) to which a packet is forwarded, and the destination to which the packet is forwarded at the [edit routing-instances] hierarchy level.