1、. . 中文 5790 字 毕业设计 外文翻译 专 业 网 络 工 程 班 级 学 生 姓名 xx 学 号 xx 指 导 教师 . . Performance of Hashing-Based Schemes for Internet Load Balancing Zhiruo Cao ,Zheng Wang ,Ellen Zegura College of Computing Georgia Institute of Technology Atlanta, GA 30332-0280 Bell Labs Lucent Technologies Holmdel , NJ 07733 Abstr
2、actLoad balancing is a key technique for improving Internet performance. Effective use of load balancing requires good traffic distribution schemes. We study the performance of several hashing schemes for distributing traffic over multiple links while preserving the order of packets within a ow. Alt
3、hough hashing-based load balancing schemes have been proposed in the past, this is the first comprehensive study of their performance using real traffic traces. We evaluate five direct hashing methods and one table-based hashing method. We find that hashing using a 16-bit CRC over the Five tuple giv
4、es excellent load balancing performance. Further, load-adaptive table-based hashing using the exclusive OR of the source and destination IP addresses achieves comparable performance to the 16-bit CRC. Table-based hashing can also distribute traffic load according to unequal weights. We also report o
5、n four other schemes with poor to moderate performance. KeywordsLoad sharing, hashing. I. INTRODUCTION Load balancing (also known as load sharing) is a key technique for improving the performance and scalability of the Internet. For example, many large enterprise networks are connected to multiple I
6、nternet Service Providers (ISPs) to achieve redundant connectivity and to distribute traffic loading. Inside the Internet, the backbones are often engineered to have multiple parallel trunks between major Points of Presence to ensure high availability. Typically, these parallel trunks are congured a
7、s equal-cost paths and allow load balancing over them. . . The parallel trunks may become even more ubiquitous when the promising Dense Wavelength Division Multiplexing (DWDM) technology is deployed in the future Internet back-bone. DWDM expands the capacity of communication trunks by allowing a gre
8、ater number of channels to be carried on a single optical fiber. With potentially tens or even hundreds of DWDM channels between major points, load balancing is essential in best utilizing the multiple parallel channels. Parallel architectures have been used for packet processing for coping with exp
9、onential growth in Internet traffic, Instead of one processing engine, packets are dispatched to multiple parallel engines inside a router to increase the overall processing throughput. The same technique is also used in scaling web servers. Popular web servers often operate a farm of machines and t
10、he routers connected to them split the HTTP requests to different machines. For all of these examples, effective use of load balancing requires good schemes for splitting traffic over multiple links. In addition, since the majority of the traffic on the Internet is TCP-based 1, traffic splitting sch
11、emes need to avoid packet misordering within a TCP ow, which can falsely trigger congestion control mechanisms and cause unnecessary throughput degradation 2, 3. In this paper, we propose and evaluate a class of hashing based traffic splitting algorithms which preserve per-ow packet ordering. We con
12、sider five hash functions that are “direct,”meaning that the hash function produces a value in the range of 0.N-1, where N is the number of outgoing links. We also consider a table-based generalization that involves hashing to M bins, then assigning the M bins to the N outgoing links. Table based ha
13、shing requires more state than direct hashing, but has the flexibility to support unequal load distribution and dynamic adaptation. Our results are obtained by simulating the performance of a trafc splitter, using packet traces taken from two trunks of a major Internet backbone provider. We nd that
14、direct hashing with the destination IP address causes signicant imbalance across two links. Using the Internet checksum or the exclusive OR of both the source IP address and destination IP address improves the performance considerably, though moderate imbalance persists. The more computationally complex 16-bit CRC of the ve-tuple (source address, destination address, source port,destination port and
