Architecture of multi-connection shaper and enforcer based on time-differential generic cell rate algorithm (GCRA)

The Generic Cell Rate Algorithm (GCRA) was used by the ITU-T Recommendation I.371 to define Peak Cell Rate and Cell Delay Variation Tolerance of an ATM connection. The ATM Forum '93 even applied it to define Sustainable Cell Rate and Burst Tolerance so as to facilitate Usage Parameter Control at User Network Interface. To determine the validity of a cell according to GCRA, the enforcer must read the clock time when the cell arrives. However, the clock of the enforcer would frequently roll over and the judgment would be incorrect accordingly. On the other hand, for a shaper in a customer premise node to dispatch cells conforming to the declared parameters, the operation would be incorrect due to the similar problem. To overcome these problems, based on 'time difference' concept, we proposed two modified GCRA's for the enforcer and shaper, respectively. Then, we design the architecture for the corresponding multi-connection shaper and enforcer and prove that they can clearly realize the proposed algorithms. Besides, the feasibility and features of the architecture are also discussed.