Cascaded policing systems and methods

1. An apparatus for policing transfer of packets, each said packet belonging to one of a plurality of traffic classes, said apparatus comprising:

a first policer for marking individual arriving first-class packets belonging to a first traffic class from among said plurality of traffic classes, which packets conform to a first committed information rate as conforming first-class packets; and

a second policer receiving a combination of said conforming first-class packets and arriving second-class packets belonging to a second traffic class from among said plurality of traffic classes, said second policer marking individual second-class packets, which second-class packets together with said conforming first-class packets conform to a sum of said first committed information rate and a second committed information rate, as conforming second-class packets.

2. An apparatus for policing transfer of packets, each packet belonging to one of a plurality of traffic classes where each traffic class is allocated a respective committed information rate, said apparatus comprising:

a cascade of policers having a one-to-one correspondence to said traffic classes, wherein

a first policer of said cascade of policers identifies packets of a first traffic class from among said plurality of traffic classes, which packets conform to a first committed information rate, as con forming packets; and

wherein each successive policer of said cascade of policers:

receives a combination of arriving packets of a corresponding traffic class and conforming packets identified by all preceding policers; and

identifies conforming packets of said corresponding traffic class which packets of said corresponding traffic class together with said conforming packets identified by all preceding policers, conform to a sum of committed information rates of all preceding traffic classes and a committed information rate of said corresponding traffic class.

3. An apparatus for policing a plurality of traffic classes of a service, said apparatus comprising:

a first policer for marking packets of a first traffic class from among said plurality of traffic classes, which packets collectively conform to a first pre-assigned guaranteed service rate, as conforming packets; and

a plurality of successive policers each successive policer provided for a specific traffic class from among said plurality of traffic classes, said each successive policer marking packets of said specific traffic class, which packets of said specific traffic class taken in combination with packets of preceding traffic classes marked as conforming packets conform to an aggregate service rate, as conforming packets of said specific traffic class.

4. The apparatus of claim 3 wherein said aggregate service rate equals a sum of guaranteed service rates of said specific traffic class and said preceding traffic classes, including said first pre-assigned guaranteed service rate.

5. The apparatus of claim 4 further comprising a leaky-bucket mechanism associated with said first policer and a leaky-bucket mechanism associated with each of said successive policers.

6. The apparatus of claim 5 wherein said marking of said packets of said first traffic class is performed by means of said leaky-bucket mechanism associated with said first policer and said marking of said packets of said specific traffic class is performed by means of said leaky-bucket mechanism associated with said each of said successive policers.

7. An apparatus for policing packets of a plurality of traffic classes of a service, said traffic classes arranged in a predetermined order, said apparatus comprising:

a first policer assigned a policer service rate equal to a pre-assigned service rate of a first traffic class of said plurality of traffic classes; and

a plurality of succeeding policers each succeeding policer allocated to a corresponding traffic class and assigned a respective policer service rat determined as a sum of a pre-assigned service rate of said corresponding traffic class and a policer service rate of an immediately preceding policer, wherein:

said first policer marks packets of said first traffic class, which packets conform to said pre-assigned service rate of said first traffic class, to produce an output of said first policer comprising packets marked as conforming packets; and

wherein said each policer:

combines packets of said corresponding traffic class with packets marked as conforming packets at outputs of all preceding policers including said first policer to produce a cumulative packet flow; and

determines conformance of said cumulative packet flow to said respective policer service rate; and

marks packets of said corresponding traffic class as conforming packets, to produce an output comprising packets marked as conforming packets, according to said conformance of said cumulative packet flow.

8. The apparatus of claim 7 wherein said output of said first policer and said output of said each succeeding policer include packets marked as nonconforming packets.