April 2015
Intermediate to advanced
372 pages
6h 56m
Chinese
Content preview from SDN: 軟體定義網路
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網路功能虛擬化（NFV） | 311
雖然這個應用範例，目前被提供 Puppet 的 L2 函式庫延伸功能所限制，但是在未來的新
功能方面，並不會存在真正的限制。
值得注意的是，類似的功能限制存在於一些可替換產品上，例如，OpenStack
Quantum。這也將會在後續版本 API 當中解決。也就是說，這個問題在於廠商是否會不
斷支援和擴充 API，以支援 L3 服務、堆疊或其他服務。
網路功能虛擬化（NFV）
在資料中心協調流程中，服務供應商提供的服務包括虛擬設備（例如，防火牆）。一般
來說，可以透過協調流程使用這些虛擬設備，允許存在一個操作流程進行簡單的遍歷動
作，這裡的邏輯介面代表租戶網路的一個入口和出口，同時建立一個簡單的資料流程模
式。事實上，這是網路功能虛擬化（NFV）技術的核心，本書使用「
服務鏈結（Service
Chaining）
」的概念，將這些功能連結起來（如圖 11-7 所示）。
圖 11-7：資料中心服務鏈結示意圖。由高可用性原則匯出的堆疊，可能會有額外的複雜性存在。
圖中描述活動中和待機的 VM 虛擬主機，這裡的活動中 / 待機的設備是以吞吐量的角度來看
NFV 的變化概念，在範例中為所有租戶提供服務的定義是，一條基本的服務鏈結：為所
有從網際網路入口流量提供的 ADC 防火牆
8
。如果採用 VPN/ 私有網路存取，那麼事實
上是兩個服務鏈結。虛擬設備所採取的動作可能是轉送、更改及轉送、丟棄，並不需要
額外的邏輯，也不需要在服務網路元件之間傳送中繼資料，同時服務鏈結也沒有明顯的 ...
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