Per-domain Packet Scale Rate Guarantee for Expedited Forwarding

The Expedited Forwarding Per-hop Behavior (EF PHB) was recently replaced by a new definition, called Packet Scale Rate Guarantee (PSRG), under the Differentiated Services (DiffServ) framework. This replacement raises two challenges. One is the implementation of PSRG server. Another is the provision of per-domain PSRG. To address the first challenge, we introduce a new concept called Latency-Rate Worst-case Service Guarantee (LR-WSG). We prove that if a server provides LR-WSG, it also provides PSRG. We show that many well-known schedulers support LR-WSG, which include not only one-level schedulers but also their hierarchical versions. To address the second challenge, we first prove that PSRG can be extended from per-node to per-domain if no flow aggregation is performed. The proof is notable in that it depends solely on the concept of PSRG itself. We then investigate the provision of per-domain PSRG in presence of flow aggregation. We propose to use Packet Scale Fair Aggregator (PSFA) to aggregate flows. We show that with PSFA, per-domain PSRG can be provided in spite of flow aggregation. We finally provide a brief discuss on the viability of using PSFA in DiffServ networks and define an Expedited Forwarding Per-domain Behavior (EF PDB).