Routers implementing the Controlled-Load and Guaranteed Services must check for conformance of data flows to their appropriate reserved Tspecs. This is known as policing. Any non-conforming data flows must not be allowed to affect the QOS offered to conforming data flows or to affect unfairly the handling of best-effort traffic.
Within these constraints the router should attempt to forward as many of the packets of the non-conforming data flow as possible. This might be done by dividing the packets into conforming and non-conforming groups and forwarding the non- conforming group on a best effort basis. Alternatively, the router may choose to degrade the QOS of all packets of a non-conforming data flow equally. The usual enforcement policy is to forward non-conforming packets as best-effort datagrams. There is some debate about actually making non-conforming packets lower effort than best effort since otherwise there is an incentive for users to send deliberately at higher rantes than their Tspec would allow.
Action with regard to non-conforming datagrams can be configurable to allow for situations such as traffic-sharing where the preferred action might be to discard non-conforming datagrams. This configuration requirement also applies to reshaping. If and when a marking facil ity (e.g. a bit in the IP header to indicate that a packet has exceeded its flow parameters) becomes available these non- conforming datagrams should be marked to ensure that they are treated as best-effort datagrams at all subsequent routers.
An additional requirement for policing over that of meeting the global traffic contract, is that there are possible consequences for pricing if excess traffic is not seen to receive a lesser service guarantee.