Present day routers typically employ monolithic operating systems which are not easily upgradahle and extensible. With the rapid rate of protocol development it is becoming increasingly important to dynamically upgrade router software in an incre-mental fashion. We have designed and implemented a high performance, modular, extended integrated services router software architecture in the NetBSD operating system kernel. This architecture allows code modules, called plugins, to be dynamically added and configured at run time. One of the novel features of our design is the ability to bind different plugins to individual flows; this allows for distinct plugin implementations to seamlessly coexist in the same runtime environment. High performance is achieved through a carefully designed modular architecture; an innovative packet classification algorithm that is both powerful and highly efficient; and by caching that exploits the flow-like character-istics of Internet traffic. Compared to a monolithic best-effort kernel, our implementation requires an average increase in packet processing overhead of only 8 % , or 500 cycles/2.lms per packet when run-ning on a P61233. 1.1 Keywords High performance integrated services routing, modular router architecture, router plugins 2.

To support the Internet's explosive growth and expansion into a true integrated services network, there is a need for cost-effective switching technologies that can simultaneously provide high capacity switching and advanced QoS. Unfortunately, these two goals are largely believed to be contradictory in nature. To support QoS, sophisticated packet scheduling algorithms, such as Fair Queueing, are needed to manage queueing points. However, the bulk of current research in packet scheduling algorithms assumes an output buffered switch architecture, whereas most high performance switches (both commercial and research) are input buffered. While output buffered systems may have the desired quality of service, they lack the necessary scalability. Input buffered systems, while scalable, lack the necessary quality of service features. In this paper, we propose the construction of switching systems that are both input and output buffered, with the scalability of input buffered switches and the r...

The fluid Generalized Processor Sharing (GPS) algorithm has desirable properties for integrated services networks and many Packet Fair Queueing (PFQ) algorithms have been proposed to approximate GPS. However, there have been few high speed implementations of PFQ algorithms that can support a large number of sessions with diverse rate requirements and at the same time maintain all the important properties of GPS. The implementation cost of a PFQ algorithm is determined by (1) computation of the system virtual time function and (2) maintaining the relative ordering of the packets via their timestamps (scheduling); and (3) in some algorithms, regulation of packets based on eligibility times. While most of the recently proposed PFQ algorithms reduce the complexity of computing the system virtual time function, the complexity of scheduling and traffic regulation (and therefore the overall complexity of implementing PFQ), is still a function of the number of active sessions. In addition, whi...

Present day routers typically employ monolithic operating systems which are not easily upgradable and extensible. With the rapid rate of protocol development it is becoming increasingly important to dynamically upgrade router software in an incremental fashion. We have designed and implemented a high performance, modular, extended integrated services router software architecture in the NetBSD operating system kernel. This architecture allows code modules, called plugins, to be dynamically added and configured at run time. One of the novel features of our design is the ability to bind different plugins to individual flows; this allows for distinct plugin implementations to seamlessly coexist in the same runtime environment. High performance is achieved through a carefully designed modular architecture; an innovative packet classification algorithm that is both powerful and highly efficient; and by caching that exploits the flow-like characteristics of Internet traffic. Compared to a mon...

The fluid Generalized Processor Sharing (GPS) algorithm has desirable properties for integrated services networks and many Packet Fair Queueing (PFQ) algorithms have been proposed to approximate GPS. However, there have been few high speed implementations of PFQ algorithms that can support large number of sessions with diverse rate requirements and at the same time maintain all the important properties of GPS. The implementation cost of a PFQ algorithm is determined by two components: (1) computation of the system virtual time function and (2) maintaining the relative ordering of the packets via their timestamps in a priority queue mechanism. While most of the recently proposed PFQ algorithms reduce the complexity of computing the system virtual time function, the complexity of maintaining the priority queue, and therefore the overall complexity of implementing PFQ, is still a function of the number of active sessions. In addition, while reducing the algorithmic or asymptotic complexit...

While PFQ algorithms can provide per-flow end-to-end delay guarantees for real-time traffic or protection among competing best-effort traffic, they have two important limitations. The first one is that, since only one parameter (a weight) is used to allocate resource for each flow, there is a coupling between delay and bandwidth allocation. When used for real-time traffic, this can result in network under-utilization. The second and less well known limitation is that, when used for best-effort traffic, PFQ algorithms favor throughputoriented applications such as FTP over delay-sensitive bursty applications such as WWW, and telnet. This is due to the memory-less instantaneous fairness property of PFQ algorithms. In a previous study [1], we proposed the Fair Service Curve (FSC) algorithm which enables more flexible delay and bandwidth allocation for real-time traffic through the use of non-linear service curves. In this paper, we show that, when used for best-effort traffic, FSC can impr...

this paper, we propose a new implementation approach called dual-rate grouping, which can significantly alleviate the above problems. Compared with the grouping architecture, the proposed approach possesses better performance in terms of approximating per session-based PFQ algorithms without increasing the implementation complexity