Dynamic Bandwidth Adjustment for Class-based Differentiated Services Networks

以動態頻寬調整之方法降低差異式服務網路之用戶阻絕率

郭芳璋(Fang-Jang Kuo)

《宜蘭技術學報》 9期電機資訊專輯 (2002/12) Pp. 207-215

https://doi.org/10.6179/nit.eec.2002.09.31

摘要

為了簡化網路的複雜度，差異式服務網路將網路上的訊務分成少數的幾個類別，並指定適量的頻寬供其使用。每一個類別必須有足夠的剩餘頻寬才能允許新的呼叫請求使用網路，否則就會將其回絕。然而，當某一種類別缺少頻寬而回絕用戶之請求時，別的類別可能有相當多的剩餘頻寬。為了將頻寬有效的利用以降低阻絕率，本文提出一種動態頻寬調整的方法。而且，為了使同一種優先權的訊務能有近似的延遲，該方法並搭配「最糟狀況公平權重」排程法來處理路徑器中的訊務﹒在本文中，動態頻寬調整時機有二種：「即時調整」與「週期調整」其中，週期調整又分10秒與100週期來討論。摸摸結果顯示即時調整可以很有效地降低阻絕率，但必須花費相當的時間處理頻寬調整的事情。相反地，週期性調整的方法雖然不須系統隨時調整頻寬，但其反應能力也會較差，阻絕率也就較高。

關鍵字

差異式服務網路 ； 動態頻寬調整 ； 阻絕率 ； 最糟狀況公平權重

並列摘要

Differentiated Services (Diffserv) networks classify packets into one of a small number of aggregated classes. Each class is usually allocated with fixed bandwidth. Whether a new call request is admitted or rejected depends on whether the corresponding class has enough redundant bandwidth. This article presents a dynamic bandwidth allocation scheme which tries to adjust bandwidth between different classes so as to prevent call blocking. In order to balance the latency of packets of different classes, this scheme is cooperated with the 'worst case weighted fair queuing' method. Two time points, 'real-time' and 'periodic,' for adjusting bandwidth are discussed. The periodic adjusting scheme is evaluated with two periods, 10 and 100 seconds. The simulation results reveal that the real-time adjusting can effectively elevate the blocking ratio at the cost of processing load of adjusting work. On the contrary, the periodic adjusting scheme can relieve the processing time at the cost of higher blocking ratio.

並列關鍵字

Diffserv networks ； dynamic bandwidth allocation ； blocking ratio ； worst case weighted fair queuing