在現今的網路中，網路服務供應業者使用了許多網路設備來提供服務，例如一些提供資訊安全以及分析流量的設備。因為使用硬體實作網路設備的困難度不斷持續上升，因此提出了網路功能虛擬化的技術，使得業者可以用軟體來實作網路功能設備。一般來說，網路功能之間存在著順序性，我們稱之為網路功能序列。每當客戶有所需求時，業者需要保留一條路徑給客戶，並且保證這條路徑上有夠用的頻寬以及能夠經過客戶需求的網路功能序列。因此當客戶量增多時，因為網路資源有限，所以業者必須決定要服務哪些客戶並向被服務的客戶收取相對於其要求頻寬的費用， 因此我們的問題是如何能在網路資源有限的情況下，盡量滿足較多的頻寬。
為了解決這個問題，我們分析出決定路徑的長度是其中最為重要的問題，因此我們提出一個方法，能在不同網路狀況下， 安排給客戶最適合的路徑長度。最後透過實驗分析，我們的方法確實能達到較佳的結果。

In the enterprise network, network functions (NFs) are widely used to provide some services, such as security protection and traffic analysis. To deal with the increasing complexity of hardware-based appliances, Network Function Virtualization (NFV) has been proposed to transform from hardware to software. Normally, traffics are required to go through several Virtual Network Functions (VNFs) in a particular order, called service chain. We need to find a single routing path carrying flow demand for each traffic and place VNFs on the path to satisfy the service chain. When satisfying the service chain for a set of traffic with demand, the total flow size go through a link cannot exceed the link's bandwidth. Because of the resource of network is limited, network operator need to decide whether to accept or reject traffics. To increase the network utilization, our goal is to maximize the total demand size of accepted traffic. However, the length of the single routing path is an important issue when solving the this problem. To address these challenges, we study different cases for different length of path. Based on these cases, we introduce a heuristic algorithm to solve this problem with a suitable path length. Our simulations, comparing our algorithm with three heuristics, show that the proposed algorithm achieve a better performance than other heuristics.

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