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Assigning Forwarding Classes and Loss Priority

You can configure firewall filters to assign packet loss priority (PLP) and forwarding classes so that if congestion occurs, the marked packets can be dropped according to the priority you set. The valid match conditions are one or more of the six packet header fields: destination address, source address, IP protocol, source port, destination port, and DSCP. In other words, you can set the forwarding class and the PLP for each packet entering or an interface with a specific destination address, source address, IP protocol, source port, destination port, or DSCP.

Note:

Junos OS assigns forwarding classes and PLP on ingress only. Do not use a filter that assigns forwarding classes or PLP as an egress filter.

When tricolor marking is enabled, a switch supports four PLP designations: low, medium-low, medium-high, and high. You can also specify any of the forwarding classes listed in Table 1

Table 1: Unicast Forwarding Classes

Unicast Forwarding Class

For CoS Traffic Type

be

Best-effort traffic

no-loss

Guaranteed delivery for TCP traffic

fcoe

Guaranteed delivery for Fibre Channel over Ethernet (FCoE) traffic

nc

Network-control traffic

To assign forwarding classes in firewall filters:

  1. Configure the family address type and filter name:
  2. Configure the terms of the filter as appropriate, including the forwarding-class and loss-priority action modifiers. For example, each of the following terms in the filter examines various packet header fields and assigns the appropriate forwarding class and packet loss priority:

    • The term corp-traffic matches all IPv4 packets with a 10.1.1.0/24 source address and assigns the packets to forwarding class no-loss with a loss priority of low:

    • The term data-traffic matches all IPv4 packets with a 10.1.2.0/24 source address and assigns the packets to forwarding class be (best effort) with a loss priority of medium-high:

    • The last term accept-traffic matches any packets that did not match on any of the preceding terms and assigns the packets to forwarding class be with a loss priority of high:

  3. Apply the filter ingress-filter to a Layer 3 interface. For information about applying the filter, see Configuring Firewall Filters. (Assigning forwarding classes and PLP is supported only on ingress filters.)

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