策略基礎網路管理之流量控制

Abstract

網際網路的使用者、設備、服務與日俱增，他們相互牽連的複雜度也相對增加，但是它目前的傳輸品質仍然是「儘力去做」(Best Effort) 的方式，無法保證頻寬與安全，這勢必局限網際網路的發展與服務範圍。解決方法之一就是對於網路設備與服務能有統籌性控管，藉著設計與使用運作策略 (Policy) 於網際網路，運作策略是一種規範網路設備運作的規則，主要是指導設備去如何處理不同的封包提供不同的服務等級，這也是一種網管系統就是所謂的 Policy-Based Network Management，負責傳送運作策略可藉由下列之一通信協定來完成之，有SNMP (Simple Network Management Protocol)、COPS (Common Open Policy Service)、HTTP等，我們在此要探討與實作的是專門為傳送運作策略而量身設計的COPS與其延生協定COPS-PR (RFC-3084 COPS Usage for Policy Provisioning)。在應用COPS的機制裡, 受控管網域內只需有一個運作策略伺服器，控管所有邊緣路由器 (Edge Router)，進一步路由器也可使用COPS將網路狀況資料回報給管理端知道，以利檢視Policy執行效果，如此一來就可以此作為改進運作策略內容、路由器運作、網路拓僕y規劃的依據，使網路運作更合理順暢。由於COPS的緣起是以解決QoS為起始，所以本文所談到的PBNM主要以QoS服務為背景，更精確的說是以 IETF之差別服務 (Difference Service) 為基礎所實作的管理系統，透過運作策略伺服器將運作策略傳至以Linux 為平台的路由器，實現流量控管的最終目的。

The Internet transmission are always "Best Effort" even through there are high bandwidth and high computing power have been deployed. One of solutions to control transmission quality and integrate these network services and devices is Policy-Based Network Management (PBNM) system. Policy is a rule to guide the behavior of a network or distributed system at high-level. Policy could be transferred by Simple Network Management Protocol (SNMP), Common Open Policy Service (COPS), HTTP, the target we will discuss and implement are COPS and its extending protocol COPS Usage for Policy Provisioning (COPS-PR). Based on COPS mechanism there could be a policy server on one administrative domain, and many administrated edge devices (routers), network status could be report by COPS also. According to these status system could update policies or enhance quality of service . More precisely our system will based on the Difference Service (DiffServ) policies and integrated with Linux Traffic Control.