3143012
TCAM-based distributed parallel packet classification algorithm with range-matching solution
Packet classification (PC) has been a critical data path function for many emerging networking applications. An interesting approach is the use of TCAM to achieve deterministic, high speed PC However, apart from high cost and power consumption, due to slow growing clock rate for memory technology in general, PC based on the traditional single TCAM solution has difficulty to keep up with fast growing line rates. Moreover, the TCAM storage efficiency is largely affected by the need to support rules with ranges, or range matching. In this paper, a distributed TCAM scheme that exploits chip-level-parallelism is proposed to greatly improve the PC throughput. This scheme seamlessly integrates with a range encoding scheme, which not only solves the range matching problem but also ensures a balanced high throughput performance. Using commercially available TCAM chips, the proposed scheme achieves PC performance of more than 100 million packets per second (Mpps), matching OC768 (40 Gbps) line rate.
1001399
DS-PPS: A Practical Framework to Guarantee Differentiated QoS in Terabit Routers with Parallel Packet Switch
Parallel Packet Switch (PPS) is used intensively in today's terabit router to construct the switching fabric. Basic PPS equally deals with all of the traffic in order to achieve uniform load-balancing and high throughput, but it fails to support differentiated QoS. With the recent blooming of delay- sensitive Internet traffic, such as the peer-to-peer live streaming and IPTV, differentiated QoS is becoming an urgent demand. In this paper, we propose a novel and practical framework, the Differentiated Service Parallel Packet Switch (DS-PPS), which supports three fundamental QoS features: guaranteed-delay (GD), guaranteed-bandwidth (GB) and best-effort (BE). By adaptively adjusting the number of switching planes offered to each QoS class, DS-PPS precisely controls the delay bounds of GD traffic and the drop precedence of GB traffic. We evaluate DS-PPS by extensive theoretical analyses and comprehensive simulations. Experimental results on a prototype implementation of the framework show that DS-PPS outperforms the basic PPS in three main aspects. First, the average delay of TCP short packet under full load is reduced by more than 94%. Second, the average delay of real-time traffic under full load is reduced by more than 82%. And third, the GB traffic of low drop precedence is guaranteed of nearly three times the throughput of high drop precedence at the hotspots. Significantly, our proposed DS-PPS framework is universal and scalable to support various kinds of emerging QoS-sensitive applications in multi-service terabit routers without any extra overhead.
13323849
On the Extreme Parallelism Inside Next-Generation Network Processors
Next-generation high-end network processors (NP) must address demands from both diversified applications and ever-increasing traffic pressure. One major challenge is to design an extraordinary scalable architecture. In this paper, it is argued that such an objective can only be sufficed by introducing highly paralleled structure, namely the paralleled processing-engine cluster (PPC). We demonstrate this point from the trade-off among aspects such as performance, programmability and flexibility. However, PPC natively suffers from several critical issues on load-balancing, intra-flow packet ordering and memory contention. After investigating several existing approaches, we present novel solutions for each issue according to the balance between performance and coast. Through intensive analysis and comprehensive simulations, it is shown that the shortest queue first scheduling with class-based prediction (SQF-C) performs nearly optimally, while the hardware based per-flow ordering mechanism resolves packet out-of-order independently with the load-balancing issue, inducting little throughput degradation. Implementing the unified solution, it is capable to design a PPC supporting up to OC-768c line rate. Real implementation is also carried out in our THNPU-1 prototype to verify the conclusions.
5712150
Preemptive Packet-Mode Scheduling to Improve TCP Performance
Recent Internet traffic measurements show that 60% of the total packets are short packets, which include TCP acknowledgment and control segments. These short packets make a great impact on the performance of TCP. Unfortunately, short packets suffer from large delay due to serving long data packets in switches running in the packet mode, i.e. a packet is switched in its entirety. To optimize TCP performance, we apply a cross-layer approach to the design of switching architectures and scheduling algorithms. Specifically, we propose a preemptive packet-mode scheduling architecture and an algorithm called preemptive short packets first (P-SPF). Analysis and simulation results demonstrate that compared to existing packet-mode schedulers, P-SPF significantly reduces the waiting time for short packets while achieving a high overall throughput when the traffic load is heavy. Moreover, with a relatively low speedup, P-SPF performs better than existing packet-mode schedulers under any traffic load.
3063801
Iteration-Shared Scheduling Algorithms Abolishing the Departure-Time-Compatible Graph in Switch-Memory-Switch Switches
Switch-Memory-Switch (SMS) architecture exhibits an excellent performance due to its emulating the Output Queueing structure. However, in order to achieve the maximal matching, the first stage scheduling operates at a huge computational complexity, which blocks the SMS from practical implementation. In order to put SMS into more effective industrial applications, especially in super-large size switches/routers with multi-services environment, two parallel iterative scheduling algorithms, named IS-RRM and AIS-RRM respectively, are proposed in this paper. The algorithms abolish totally the traditional departure-time-compatible (DTC) graph, and by using iteration-sharing technology, greatly reduce the required iteration number in each time slot. Using a discrete-time Markov chain to model the AIS-RRM algorithm, we obtain its upper bound of cell loss rate. Meanwhile, experimental and theoretical results show that so long as the number of shared memories is twice the switch size, AIS-RRM algorithm can achieve a cell loss rate of 10 when the input buffer size is 15 and the iteration number of each time slot is 6, despite the arrival traffic pattern and the switch size. Furthermore, the iteration number required in each time slot can be further decreased by increasing the input buffer size.
17725194
SPF: to improve the performance of packet-mode scheduling
Recent researches present that packet-mode scheduling may provide overall performance advantages over cell-mode scheduling in input queueing switches. But one significant drawback of existing packet-mode schedulers is that they tend to result in longer waiting time of short packets, whose delay is critical to the performance of IP networks. To mitigate the problem, this paper proposes a simple but effective packet-mode scheduling algorithm called Short Packets First (SPF), studies the corresponding buffering architecture, and evaluates the performance on throughput and packet delay. SPF achieves 100% throughput under an accurate Internet traffic model. Theoretical analysis proves that SPF can reduce the average packet waiting time of short packets as well as overall packets, under the condition of uniform Poisson arrival process and low to medium offered load. Furthermore, extended simulation studies show that SPF is superior to general packet-mode and cell-mode scheduling, especially under heavy offered load.
8364982
Supporting Complex Multi-Dimensional Queries in P2P Systems
More and more applications require peer-to-peer (P2P) systems to support complex queries over multi-dimensional data. For example, a P2P auction network for real estate frequently needs to answer queries such as "select five available buildings closest to the airport". Such queries are not efficiently supported in current P2P systems. Towards an efficient and scalable P2P system capable of processing complex multi-dimensional queries, the authors first proposed a comprehensive framework for sharing, indexing, and querying multi-dimensional data, where (i) peers with more computational power coordinate indexing and query processing, and (ii) other peers participate in part of the computation in order to achieve scalability and load-balance. Based on this framework, Network-R-tree (NR-tree), a P2P adaptation of the dominant spatial index - R*-tree was proposed. NR-tree, indexing spatial data at clustered peers, is capable of processing complex queries such as range queries and k-nearest neighbor queries. The authors proposed query processing algorithms for range and k-nearest neighbor queries and experimentally prove the effectiveness of proposed techniques with real data
7867063
D-CAPE: distributed and self-tuned continuous query processing
Efficient continuous query processing is critical for many applications, including monitoring remote sensors network traffic management, and online transaction processing. To overcome resource limitations and achieve real-time responsiveness, continuous query systems research focuses on issues such as punctuation-driven operator-state purging [4], load shedding, operator scheduling [7] and plan optimization and on-line migration [9]. However, when real-time yet accurate results are critical such as in stock market analysis, then there is a limitation to what any of the above optimization techniques can accomplish. Hence, distributed processing must be applied to support required scalability. It has been already proven in traditional database systems [3] that distributed processing results in high scale-up and speed-up capabilities due to aggregated resources. The design of a distributed continuous query system is characterized by an extra complexity, considered in the design of our D-Cape engine. In such a system, data streams may be infinite and initial cost statistics about the data streams are typically unknown. Moreover, cost statistics continue to change over time. Our research on distributed stream processing addresses two critical questions: (1) How to initially distribute query plans given little or possibly no cost information, and (2) How to efficiently adapt the query distribution corresponding to runtime environmental changes. Even though research is now under way in designing distributed continuous query systems [2], [1], results to date, as far as we know, are based on simulations. Our work offers empirical results of distributed continuous query processing using an actual software system [5], [6]. D-Cape, a distributed continuous query processing architecture, employs stream query engines over a cluster of shared-nothing processors. We employ a dedicated distribution manager to manage
1437746
On the skew-bounded minimum-buffer routing tree problem
Bounding the load capacitance at gate outputs is a standard element in today's electrical correctness methodologies for high-speed digital very large scale integration design. Bounds on load caps improve coupling-noise immunity, reduce degradation of signal transition edges, and reduce delay uncertainty due to coupling noise (Kahng et al. 1998). For clock and test distribution, an additional design requirement is bounding the buffer skew, i.e., the difference between the maximum and the minimum number of buffers over all of the source-to-sink paths in the routing tree, since buffer skew is one of the main factors affecting delay skew (Tellez and Sarrafzadeh 1997). In this paper, we consider algorithms for buffering a given tree with the minimum number of buffers under given load cap and buffer skew constraints. We show that the greedy algorithm proposed by Tellez and Sarrafzadeh is suboptimal for nonzero buffer-skew bounds and give examples showing that no bottom-up greedy algorithm can achieve optimality. The main contribution of the paper is an optimal dynamic programming algorithm for the problem. Experiments on test cases extracted from recent industrial designs show that the dynamic programming algorithm has practical running time and saves up to 37.5% of the buffers inserted by Tellez and Sarrafzadeh's algorithm.
800712
On the autocorrelation structure of TCP traffic
The statistical characteristics of network traffic--in particular the observation that it can exhibit long range dependence--have received considerable attention from the research community over the past few years. In addition, the recent claims that the TCP protocol can generate traffic with long range dependent behavior has also received much attention. Contrary to the latter claims, in this paper we show that the TCP protocol can generate traffic with correlation structures that spans only an analytically predictable finite range of time-scales. We identify and analyze separately the two mechanisms within TCP that are responsible for this scaling behavior: timeouts and congestion avoidance. We provide analytical models for both mechanisms that, under the proper loss probabilities, accurately predict the range in time-scales and the strength of the sustained correlation structure of the traffic sending rate of a single TCP source. We also analyze an existing comprehensive model of TCP that accounts for both mechanisms and show that TCP itself exhibits a predictable finite range of time-scales under which traffic presents sustained correlations. Our claims and results are derived from Markovian models that are supported by simulations. We note that traffic generated by TCP can be misinterpreted to have long range dependence, but that long range dependence is not possible due to inherent finite time-scales of the mechanisms of TCP.
20672183
An Algorithm to Construct k-Regular k-Connected Graphs with the Maximum k-Diameter
Abstract. Let f(2m,k) be the Maximum k-diameter of k-regular k-connected graphs on 2m vertices. In this paper we give an algorithm and prove that we can construct k-regular k-connected graphs on 2m vertices with the maximum k-diameter using it. We also prove some known results about f(2m,k) and verify that we can get some unknown values of f(2m,k) by our algorithm.