We consider the problem of providing service guarantees in a high-speed packet switch. As basic requirements, the switch should be scalable to high speeds per port, a large number of ports and a large number of traffic flows with independent guarantees. Existing scalable solutions are based on Virtual Output Queuing, which is computationally complex when required to provide service guarantees for a large number of flows. We present a novel architecture for packet switching that provides support for such service guarantees. A cost-effective fabric with small external speedup is combined with a feedback mechanism that enables the fabric to be virtually lossless, thus avoiding packet drops indiscriminate of flows. Through analysis and simulation, we show that this architecture provides accurate support for service guarantees, has low computational complexity and is scalable to very high port speeds.
In recent years, these potential scalability concerns have been addressed by implementing a very small number of independent service guarantees. Under the Differentiated Services framework @cite_12 , flows are aggregated in @math classes, and service guarantees are offered for classes. The downside is that the realized QoS per flow has a lower level of assurance (higher probability of violating the desired service level) than the QoS per aggregate @cite_9 , @cite_1 . Moreover, recently proposed VPN and VLAN services @cite_11 , @cite_17 require per-VPN or VLAN QoS guarantees. All the above are arguments in favor of implemeting a number of independent service guarantees per port much larger than six.
@cite_11 @cite_9 @cite_1 @cite_12 @cite_17
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The Differentiated Service (Diff-Serv) architecture [1] advocates a model based on different “granularity” at network edges and within the network. In particular, core routers are only required to act on a few aggregates that are meant to offer a pre-defined set of service levels. The use of aggregation raises a number of questions for end-to-end services, in particular when crossing domain boundaries where policing actions may be applied. This paper focuses on the impact of such policing actions in the context of individual and the bulk services built on top of the Expedited Forwarding (EF) [7] per-hop-behavior (PHB). The findings of this investigation confirm and quantify the expected need for reshaping at network boundaries, and identify a number of somewhat unexpected behaviors. Recommendations are also made for when reshaping is not available. This paper explores, primarily by means of analysis, the differences that can exist between individual and aggregate loss guarantees in an environment where guarantees are only provided at an aggregate level. The focus is on understanding which traffic parameters are responsible for inducing possible deviations and to what extent. In addition, we seek to evaluate the level of additional resources, e.g., bandwidth or buffer, required to ensure that all individual loss measures remain below their desired target. The paper's contributions are in developing analytical models that enable the evaluation of individual loss probabilities in settings where only aggregate losses are controlled, and in identifying traffic parameters that play a dominant role in causing differences between individual and aggregate losses. The latter allows the construction of guidelines identifying what kind of traffic can be safely multiplexed into a common service class. This document defines an architecture for implementing scalable service differentiation in the Internet. This architecture achieves scalability by aggregating traffic classification state which is conveyed by means of IP-layer packet marking using the DS field [DSFIELD]. Packets are classified and marked to receive a particular per-hop forwarding behavior on nodes along their path. Sophisticated classification, marking, policing, and shaping operations need only be implemented at network boundaries or hosts. Network resources are allocated to traffic streams by service provisioning policies which govern how traffic is marked and conditioned upon entry to a differentiated services-capable network, and how that traffic is forwarded within that network. A wide variety of services can be implemented on top of these building blocks. This document provides requirements for Layer 3 Virtual Private Networks (L3VPNs). It identifies requirements applicable to a number of individual approaches that a Service Provider may use to provision a Virtual Private Network (VPN) service. This document expresses a service provider perspective, based upon past experience with IP-based service offerings and the ever-evolving needs of the customers of such services. Toward this end, it first defines terminology and states general requirements. Detailed requirements are expressed from a customer perspective as well as that of a service provider. This memo provides information for the Internet community.