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Multifield Classifiers

A multifield (MF) classifier is a second method for classifying traffic flows. Unlike the behavior aggregate classifier, a multifield classifier can examine multiple fields in the packet—for example, the source and destination address of the packet or the source and destination port numbers of the packet. With multifield classifiers, you set the forwarding class and loss priority of a packet based on firewall filter rules.

Note: For a specified interface, you can configure both an MF classifier and a BA classifier without conflicts. Because the classifiers are always applied in sequential order, the BA classifier followed by the MF classifier, any BA classification result is overridden by an MF classifier, if they conflict.

JUNOS software performs MF traffic classification by directly scrutinizing multiple fields of a packet to classify a packet without having to rely upon the output of the previous BA traffic classification. JUNOS software can simultaneously check a packet's data ranging from layer 2 to layer 7 as shown in Table 177

Table 177: MF Classification

Layer	CoS Parameter
Layer 2	IEEE 802.1Q: VLAN ID IEEE 802.1p: User Priority
Layer 3	IPv4: Precedence IPv4: DSCP IPv4: Source IP address IPv4: Destination IP address IPv4: Protocol ICMP: Code and type
Layer 4	TCP/UDP: Source port TCP/UDP: Destination port TCP: Flags AH/ESP: SPI
Layer 7	Not supported for this release.

Using JUNOS software, you configure an MF classifier with a firewall filter and its associated match conditions. This enables you to use any filter match criteria to locate packets that require classification. For more information on firewall filters and policies, see the JUNOS Software Security Configuration Guide.

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