Fleksibilni Internet servisi na bazi kontrole kašnjenja i

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Abstrakt Vladimir V. Vukadinović Fleksibilni Internet servisi na bazi kontrole kašnjenja i propusnosti Internet je transportna infrastruktura za aplikacije sa različitim zahtevima u pogledu kvaliteta servisa. Današnji Internet je međutim samo “best-effort” mreža bez implementiranih mehanizama za diferencijaciju servisa. Skorašnji napori da se obezbede takvi mehanizmi usmereni su ka takozvanim fleksibilnim servisima. Većina predloženih arhitektura za pružanje fleksibilnih servisa se bazira na principu pružanju servisa malog kašnjenja po cenu povećanja verovatnoće gubitka paketa. Ove arhitekture međutim ne uzimaju u obzir uticaj diferencijacije kašnjenja na performanse TCP-a, najčešće korišćenog transportnog protokola na Internetu. Prilikom projektovanja mehanizama za diferencijaciju servisa, neophodno je uzeti u obzir kompleksnost TCP algoritma za kontrolu zagušenja. U ovoj tezi pretstavljen je nova arhitektura za diferencijaciju kašnjenja i propusnosti zasnovana na konceptu fleksibilnih servisa. Neophodni uslovi za ostvarivanje željene diferencijacije servisa između razlicitih klasa mrežnog saobraćaja izvedeni su na osnovu analize kontrolnog sistema sa povratnom spregom koga čine TCP algoritam za kontrolu zagušenja i mehanizmi za diferencijaciju kašnjenja i kontrolu verovatnoće gubitaka. Ključne reči—diferencijacija servisa, fleksibilni servisi, QoS, aktivna kontrola bafera, TCP, mrežni saobraćaj. ii
Abstract Vladimir V. Vukadinović Delay and throughput differentiation mechanisms for non-elevated services Internet is a transport infrastructure intended for applications with various service requirements. However, Internet remains to be a best-effort network without widely deployed mechanisms for service differentiation and quality of service (QoS) provisioning. Research efforts to provide service differentiation in the Internet have been recently directed toward non-elevated services. Majority of proposed non-elevated mechanisms aim to provide low delay service at the expense of increased packet loss probability. However, these proposals do not consider the influence of delay and loss differentiation on the behaviour of TCP, the most widely used transport protocol in today’s Internet. Service differentiation mechanisms cannot be properly designed without taking into account the complexity of TCP’s congestion control algorithm. In this thesis, we propose a new non-elevated service differentiation architecture and derive necessary conditions to provide desired service differentiation among traffic classes by considering TCP’s congestion control algorithm, delay differentiation mechanisms, and proposed packet loss controller as a feedback control system. Keywords—non-elevated services, service differentiation, TCP, QoS, queue management. iii
Page 1: UNIVERZITET U BEOGRADU ELEKTROTEHNI
Page 5 and 6: Table of Contents Abstrakt.........
Page 7 and 8: List of Figures Fig. 1. Traffic con
Page 9 and 10: List of Tables Table 1. Comparison
Page 11 and 12: IntServ Integrated Services IP Inte
Page 13 and 14: The DiffServ model [8]-[10] offers
Page 15 and 16: [29]. Detailed description of these
Page 17 and 18: 2. Quality of Service in Internet:
Page 19 and 20: whose sole purpose is to detect and
Page 21 and 22: architectures (implemented or propo
Page 23 and 24: 2.2.2. Differentiated Services (Dif
Page 25 and 26: 2.2.3. Non-Elevated Services Non-El
Page 27 and 28: 3. Survey of existing proposals for
Page 29 and 30: RED [29] is an active queue managem
Page 31 and 32: The intersections of the RED contro
Page 33 and 34: flows. Quality of services received
Page 35 and 36: normalized loss rates among classes
Page 37 and 38: 4. Proposed service differentiation
Page 39 and 40: controller can be considered as an
Page 41 and 42: to a close-to-optimal rate assignme
Page 43 and 44: Fig. 8. Example of an input and out
Page 45 and 46: where I DS ( τ ) Z ( τ ) = . If (
Page 47 and 48: packet departure as: V V TS DS d
Page 49 and 50: 5.3.1. Influence of traffic load In
Page 51 and 52: differentiation. Similar result has
Page 53 and 54:
In order to investigate the perform
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schedulers for proportional delay d
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6. Packet Loss Controller Packet Lo
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described by Floyd and Jacobson [29
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where R’ and p’ are round-trip
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Since σ=σ0 ensures that T=T’, i
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⎛ ⎜ ⎝ Based on (51) - (54),
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7. Simulation results We evaluated
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BPR scheduling without PLC, TCP flo
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time of TCP packets continually inc
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Fig. 27. Influence of UDP load on T
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even in the case of multiple bottle
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management, PLC controller and TCP
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Appendix A The pseudocode for the h
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Appendix B We describe here a proce
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Fig. 30. TCP throughput as a functi
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2 ⎛ 2 ⎞ 5 ⎛ 2 ⎞ 1 ⎛ ⎞
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+Queue/PROBE set wait_ true +Queue/
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}; #endif int idle_; /* queue is id
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} if (!dsQueue.head() && tsQueue.he
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* count and count_bytes keeps a tal
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int PROBEQueue::length(int qos_clas
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[13] S. Bodamer, “A new schedulin
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[37] K. Nichols, S. Blake, F. Baker
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Fleksibilni Internet servisi na bazi kontrole kašnjenja i

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