Almost three years ago, cisco and microsoft annouced the directory enabled network(DEN)initiative, which sought to develop a standard for storing information about network devices, applications and users in a single directory.

　　This directory would bind a user's name and network resource access profile to policies for granting or restricting that access, and delegating bandwidth priorities and privileges.work on standardizing specifications for the directory were handed off to the distributed manage-ment task force (DMTF).

　　In march, the DMTF announced it had completed work on a new version of the common infor-mation model that facilitates the mapping of the CIM schema into a lightweight directory access protocol(LDAP)-compliant directory. CIM defines how to represent network device, system and application data in a directory so it can be easily shared for DEN and enter-prise management purposes.

　　By mapping the CIM schema into an LDAP directory, users will be able to further integrate directory information into an overall enterprise management system, the DMTF says.

　　Customers will make DEN-compliant products a priority once the DMTF makes a little more progress on DEN specifications-such as defining a pollicy schema that would specify data structures for binding directory profiles to network security and quality-of-service (QOS)policies and products soon follow.

　　Perhaps, vendors still have to determine how to use directories to prompt network and applications to configure themselves based on business policies. For example, when a user logs on to a network, the directroy would recognize the user's name, department, location and rank within the company, and bind this information with the user's network access or restriction policies. then the IT infrastructure would configure itself accordingly to enable or disable that a access.

　　One of the killer applications for DEN when it was announced was the ability to link QoS policies to users via dircetories. But bandwidth has become cheaper and more plentiful in the LAN over the past two years, and that's made QOS much less of an issue.

　　Instead of prioritizing bandwidth allocation, users can inexpensively overprovision band-width when they need to support delay-sensitive traffic such as voice and video. Also, simple mechanisms such as setting 802.1p bits on ethernet frame or type-of -service bits in IP headers are enough for LAN QOS.

　　Nonetheless, there 's still a huge demand among enterprise users for directories to enable self-configuring networks based on business policy.

　　DEN for QOS may still apply for WAN applications, edholm says. Indeed cisco has made more strides with DEN in the service provider market than in the enterprise arena.

　　Service providers are looking to DEN to integrate multivendor products into an interoperable operational support system.

　　So despite the silnece, progress on DEN is being the silnece, progress on DEN is being made and activty is expected to pick up once standards become a little more solidiffed.

　　差不多三年前，思科公司和微软公司宣布了目录允许网络(DEN)倡议，该公司要求开发一个在单一目录中存储有关网络设备、应用程序和用户等信息的标准。

　　此目录把用户的名字和网络资源访问简表与允许或限制访问的政策和安排带宽优先级别及特权挂起钩来。此目标标准规范的研究工作交给了分布管理任务组(DMTF)。

　　今年三月，DETF 宣布完成了新版公共信息模型(CIM)的研究工作，此模型实现了CIM模式映射到简便目录访问协议(LDAP)的相应目录中，CIM 定义如何在目录中表示网络设备，系统和应用数据，因而它很容易为DEN 和企业管理目的而被共享。

　　DMTF 称， 通过把CIM 模式映射到LDAP 目录，用户就能进一步把目录信息与整个企业管理系统结合起来。

　　一旦DMTF在DEN 规范上取得更多一些进展，如定义一个为把目录简表与网络安全和服务质量(QOS)政策捆绑在一起而规定数据结构的政策模式，以及随之而来的产品，客户将优先使用符合DEN的产品。

　　厂商们也许还不得不确定怎样利用目录来提示网络和应用程序以便依据商业政策来配置他们自己。例如：当一用户登录上网时，目录将会识别出用户的名字、所在的部门、地点及在公司中的级别，把这些信息与用户的网络访问或限制政策捆绑在一起。然后，IT 基础设施就能相应地配置自己，以便实现或不让实现访问。

　　当年宣布DEN 的最具冲击力的应用之一是通过目录把QOS 政策与用户联系起来的能力，但在过去两年局域网中带宽变的更为便宜和充足，是QOS不再是个问题。

　　当用户需要支持对延迟敏感的流量，如声音和视频图象时，他们可以廉价地获得很大的带宽，而不用对带宽进行优先等级分配。同时，在以太网桢上设置802.1P 位或者在IP 报头中设服务类型位等简单机制对局域网的QOS 来说已经足够了。

　　然而，在企业用户中对目录还存在着巨大需求，以便能够依据商业政策自行配置网络。

　　EDHOLM说：“实现QOS 的DEN 还可以应用于广域网上的应用程序。实际上。思科公司利用DEN 在服务供应商市场上取得了比企业市场更大的进步。服务供应商正期待着把DEN 做进更多厂商产品中去，成为一个可互用的运行支持系统。

　　尽管(DEN)比较沉默，但DEN 正在取得进步，一旦此标准变的更为稳定，DEN 可望会有所作为。

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