4.2. NLRI Value Encoding

The Flow Specification NLRI value consists of a list of optional components and is encoded as follows:

Encoding: <[component]+>

A specific packet is considered to match the Flow Specification when it matches the intersection (AND) of all the components present in the Flow Specification.

Components MUST follow strict type ordering by increasing numerical order. A given component type MAY (exactly once) be present in the Flow Specification. If present, it MUST precede any component of higher numeric type value.

All combinations of components within a single Flow Specification are allowed. However, some combinations cannot match any packets (e.g., "ICMP Type AND Port" will never match any packets) and thus SHOULD NOT be propagated by BGP.

An NLRI value not encoded as specified here, including an NLRI that contains an unknown component type, is considered malformed and error handling according to Section 10 is performed.