8.4 Ingress and Egress Functions

In this section, ingress and egress functions are discussed. Classification and policing are typically related to the ingress, while scheduling, queuing, queue management and shaping to the egress. These functions are dependent on the network node capabilities.

8.4.1 Ingress Classification and Policing

At the ingress of e.g. a service provider's node, traffic may be subject to classification and ingress policing. An example is policing related to MEF services.

These ingress functions are related to trust. Often at the boundary between administrative domains, ingress functions are executed. If the backhaul network is administered by an entity separate from the mobile network operator, the backhaul network operator may wish to control the amount of traffic entering his network by means of policing.

Ingress policing also helps to avoid excessive traffic overloading the network element. This is related to security as well, since it mitigates some of the risks related to flooding attacks. Again, if the network can be trusted, there is less need for ingress policing.

Control plane policing refers to limiting the amount of ICMP control messages, spanning tree BPDUs, routing protocol messages, and similar control messages, which all typically require processing from a processor unit of a network node. If a processor is overloaded with incoming packets to be processed, it may crash or stall causing unpredictable behaviour.

If the policer is QoS-aware, it ...

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