Fleksibilni Internet servisi na bazi kontrole kašnjenja i

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fixed delay and loss differentiation parameters and let senders decide which class satisfies their service requirements. Major problem with EDS is that it does not consider the behaviour of transport protocols employed by various applications. For instance, TCP flows are responsive and they decrease their sending rate if a packet loss has been detected. Furthermore, sending rate of a TCP flow depends on the round-trip time of its packets. Therefore, in order to achieve predictable performance of TCP flows, loss and delay differentiation parameters in EDS cannot be set arbitrarily. In [5] authors suggest that complexity of TCP may lead them to design a new transport protocol, rather than to adapt TCP to EDS. However, since TCP is already widely deployed, the only feasible solution is to adapt service differentiation mechanisms to TCP, not the opposite. In the Section 4, we introduce a new service differentiation mechanism for non- elevated services that alleviates this problem. We define the objectives of the proposed mechanism and describe its architecture. 25
4. Proposed service differentiation architecture for non-elevated services In this Section, we propose a new solution to service differentiation in Internet. Proposed architecture relies entirely on router mechanisms to provide weak service guaranties. In addition to existing scheduling and buffer management algorithms, proposed architecture employs a new algorithm named Packet Loss Controller (PLC) to ensure that traffic classes receive “different but equal” quality of service. Internet applications can be classified as delay-sensitive (DS) and throughput- sensitive (TS). Delay-sensitive applications, such as IP Telephony and Video on Demand, employ UDP or similar unresponsive protocols. Throughput-sensitive applications, such as File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), and Simple Mail Transfer Protocol (SMTP), employ TCP as a transport protocol. Therefore, service differentiation problem can be considered as a problem of providing different treatment to TCP and UDP flows. An application may use last two bits of DS field in the IP header, which are not yet assigned, to mark its packets as delay-sensitive or throughput-sensitive [37]. Two objectives of a new service differentiation architecture that we propose in this thesis are to provide: 1) proportionally lower delay to delay-sensitive class (UDP), compared to the delay experienced by throughput-sensitive class (TCP); 2) at least the same throughput to throughput-sensitive flows (TCP) as they would receive in a best-effort network. The first objective is accomplished by using a Backlog-Proportional Rate (BPR) scheduler, introduced in [12]. The BPR classifies the throughput-sensitive and delay- 26
Page 1 and 2: UNIVERZITET U BEOGRADU ELEKTROTEHNI
Page 3 and 4: Abstract Vladimir V. Vukadinović D
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: normalized loss rates among classes
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
Page 55 and 56: schedulers for proportional delay d
Page 57 and 58: 6. Packet Loss Controller Packet Lo
Page 59 and 60: described by Floyd and Jacobson [29
Page 61 and 62: where R’ and p’ are round-trip
Page 63 and 64: Since σ=σ0 ensures that T=T’, i
Page 65 and 66: ⎛ ⎜ ⎝ Based on (51) - (54),
Page 67 and 68: 7. Simulation results We evaluated
Page 69 and 70: BPR scheduling without PLC, TCP flo
Page 71 and 72: time of TCP packets continually inc
Page 73 and 74: Fig. 27. Influence of UDP load on T
Page 75 and 76: even in the case of multiple bottle
Page 77 and 78: management, PLC controller and TCP
Page 79 and 80: Appendix A The pseudocode for the h
Page 81 and 82: Appendix B We describe here a proce
Page 83 and 84: Fig. 30. TCP throughput as a functi
Page 85 and 86: 2 ⎛ 2 ⎞ 5 ⎛ 2 ⎞ 1 ⎛ ⎞
Page 87 and 88:
+Queue/PROBE set wait_ true +Queue/
Page 89 and 90:
}; #endif int idle_; /* queue is id
Page 91 and 92:
} if (!dsQueue.head() && tsQueue.he
Page 93 and 94:
* count and count_bytes keeps a tal
Page 95 and 96:
int PROBEQueue::length(int qos_clas
Page 97 and 98:
[13] S. Bodamer, “A new schedulin
Page 99 and 100:
[37] K. Nichols, S. Blake, F. Baker
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