在差異式服務的網路架構中，不同的使用者可以得到不同等級的服務。而在保證遞送這個服務等級，路由器提供三種不同的封包丟棄機率來提供軟性的服務保證。但是許多研究已經發現這樣的網路架構並不能達到預期的效果，這是因為傳輸協定會因為封包丟失而有不同的反應。
一個網路服務提供者並不能知道什麼型態的資料流會被送進網路，所以一個網路必須能夠適應不同的使用者，並提供一定的服務品質。
我們提出了一個新的流量控制的方法，改進了差異式服務網路架構中的邊緣路由器，藉由偵測流量的情形並動態地調整封包丟棄機率使網路有適應不同類型資料流的能力。實驗結果證明這個方法可以改善因為資料流不同而引起的頻寬分配不公平的現象。

Differentiated Services architecture permits the allocation of different levels of service to different users. And the Assured Forwarding Per-Hop-Behavior Group defined different drop precedence in the DS routers to provide soft guarantees. However, it has been observed that the drop precedence cannot achieve the desired target rates because of the strong interaction of the transport protocol with packet drops in the Internet.
An Internet Service Provider (ISP) does not know what kind of traffic will be sent into the network, so the Internet Service Provider should be able to adapt different types of clients and provides certain quality of services (QOS).
We propose a new flow control scheme to enhance the edge routers in a Differentiated Services network with the adaptive drop precedence according to actual flow rates to improve the fairness among the different types of traffics through the Differentiated Services network.

Introduction…………………………….…………..……….……………1

1.1Problems with Internet today.………………….……………………………..2
1.2 Integrated Services and Differentiated Services………….…….……………2

The Differentiated Services Architecture……………………………...…5

2.1 Differentiated Services Region……………………………………………....5
2.2 Traffic Classification and Conditioning……………………………………...8
2.3 Per-Hop Behaviors………………………………………………………….13
2.4 Bandwidth Broker…………………………………………………………..17

Problems with Differentiated Services……………………………...…..22

3.1 The Causes for the Problems……………………………………….……….23
3.2 Related Works……………………………………………………………....25

Adaptive Flow Control Scheme……………………………..….……....31

4.1 AFCS Architecture………………………………………………………….31
4.2 Dropper and Queue Management…………………………………….….....32
4.3 Bandwidth Broker………………………….……………………………….35
4.4 AFCS Ingress Node………………………………………………………....37
4.5 AFCS Egress Node……………………………………………………….…40

Simulation Result and Analysis……………….………….………..……42

Conclusion and Future Work………….………………….……..………47





Reference…………………………………………………..……………49

Appendix : Terminology…………………………..……………………51

[1] J. Wroclawski, "The Use of RSVP with IETF Integrated Services," RFC 2210, September 1997.
[2] K. Nichols, S. Blake, F. Baker, D. Black, “Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers,” RFC 2474, December 1998.
[3] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, and W. Weiss, "An Architecture for Differentiated Services," RFC 2475, December 1998.
[4] Hungkei Chow, Alberto Leon-Garcia, “A Feedback Control Extension to Differentiated Services,” Internet Draft, draft-chow-diffserv-fbctrl-00.txt, March 1999.
[5] J. Heinanen, Telia Finland, F. Baker, W. Weiss, Lucent Technologies, J. Wroclawski, “Assured Forwarding PHB Group,” RFC 2597, June 1999.
[6] V. Jacobson, K.Nichols, K. Poduri," An Expedited Forwarding PHB," RFC 2598, June 1999.
[7] David D. Clark and Wenjia Fang, “Explicit Allocation of Best-Effort Packet Delivery Service,” IEEE/ACM Transactions on Networking, AUGUST 1998.
[8] D. Durham, Ed., J. Boyle, R. Cohen, S. Herzog, R. Rajan, A.Sastry, “The COPS (Common Open Policy Service) Protocol,” RFC 2748, January 2000.
[9] Ikjun Yeom and A. L. Narasimha Reddy, “Realizing Throughput Guarantees in a Differentiated Services Network,” IEEE CONFERENCE 1999.
[10] Wu-Chang Feng, Dilip D. Kandlur, Member, IEEE, Debanjan Saha, and Kang G. Shin, Fellow, IEEE, “Adaptive Packet Marking for Maintaining End-to-End Throughput in a Differentiated-Services Internet,” IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 7, NO. 5, OCTOBER 1999.
[11] Wu-Chang Feng, Dilip D. Kandlur, Member, IEEE, Debanjan Saha, and Kang G. Shin, Fellow, IEEE, “Understanding and Improving TCP Performance Over Networks with Minimum Rate Guarantees,” IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 7, NO. 2, APRIL 1999.
[12] Sally Floyd, and Van Jacobson, “Random Early Detection Gateways for Congestion Avoidance,” IEEE/ACM TRANSACTIONS ON NETWORKING, VOL 1, NO 4, AUGUST 1993.
[13] S. McCanne and S. Floyd. ns-LBNL Network Simulator. Http://www-nrg.ee.lbl.gov/ns/.
[14] V. Jacobson, "Congestion Avoidance and Control," in Proc. ACM SIGCOMM'88, Stanford, CA, 1988, pp. 314-329.
[15] Sally Floyd, and Van Jacobson, "Link-sharing and Resource Management Models for Packet Networks," IEEE/ACM TRANSACTIONS ON NETWORKING, VOL 3, NO 4, AUGUST 1995.
[16] K. Nichols, V. Jacobson, and L. Zhang, "A Two-bit Differentiated Services Architecture for the Internet," Work in Progress, ftp://ftp.ee.lbl.gov/papers/dsarch.pdf