ITU-T H.248.53 PDF

This Recommendation provides three H.248 packages in the area of traffic control. The Traffic Management package defines the properties to control the traffic policing enforcement of the incoming flow and performing admission control in the media gateway (MG). Traffic shaping is out of scope of Traffic Management package version 1. The Traffic Policing Statistics package defines a statistic for traffic policers (as a complementary protocol element for the Traffic Management package). The Packet Size package allows a media gateway controller (MGC) to signal additional packet-size based conditions for the traffic policer.

Policy rules and policy enforcement behaviour

The tman and/or pacs packages in this Recommendation may be applied for traffic policing. If applied, the MG provides a "traffic policer" function. Any policy rule is comprised by a set of conditions and a set of actions (see e.g., usage filter/policy rules in H.248 packages for gate management/control). In the case of traffic policing, the set of functions could include:

1) transparent packet forwarding;

2) packet tagging (Note 1); or

3) packet dropping.

NOTE 1 – As at the date of approval of this Recommendation, this function is not supported by H.248.53.

A modified 2) or discarded 3) packet may be recorded in an H.248 statistic. Which statistic is used for action 3) could be dependent on different conditions:

– discarded packets due to traffic parameter violations (see clause 7.4 tmanr/dp); and

– discarded packets due to packet size range violation (see clause 8.4 pacs/dp).

NOTE 2 – Such statistics may complement other statistics used for policing, e.g., gm/dp, in the case that a complete overview is required about the various reasons behind dropped packet events.

Deriving policy enforcement point parameters

The packages define generic traffic parameters, which may be used for specific traffic policers. The mapping between these H.248 signalling elements and specific, bearer-dependent policy enforcement point (PEP) policing algorithms is the subject of clause 9. Such an algorithm may consider tman properties only (i.e., traffic policer conditions just on bitrate and/or delay variation parameters), or the pacs properties only (i.e., traffic policer conditions just on PDU size parameters), or the properties of both packages.