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1、热点技术基于IP网络的SLA参数探讨柯敏 雷维礼（电子科技大学通信与信息工程学院，成都 610054）摘要： 随着技术的不断成熟，通信运营商之间新一轮的竞争逐渐由技术转向服务，SLA（Service Level Agreement，服务等级协议）受到越来越多人的关注，并且已经开始运用到各种场景。但是SLA要发挥更大的作用，还需要进一步的研究和提高，尤其是关于SLA参数的问题。本文针对目前最主流的IP网络进行SLA参数的分析和讨论。关 键 词： 管理服务 IP网络 SLA 参数 KQI KPI1. 引言 在当前日益激烈的电信市场，提高服务品质和客户满意度已成为通信运营商在竞争中取胜的一个重要筹码
2、，SLA（Service Level Agreement，服务等级协议）服务模式应运而生。SLA是服务提供商和客户通过协商，在服务品质、优先权和责任义务等方面达成的协定，用来保证可度量的网络性能达到所定义的品质，具有法律效力。SLA至少需要包含3方面内容：服务等级目标（SLO）、违例处理和不可抗因素声明。其中服务等级目标是通过定义SLA参数来描述的，目前各种SLA参数的分类和定义已成为SLA管理中的重点，正确、有效的参数定义也是服务提供商与客户就服务质量达成一致理解的基础。尤其是以IP为核心的网路与传统的电信网相比，其服务质量的性能指标更加复杂多变，SLA参数的管理将更加困难。2. 基于IP网
3、络的SLA参数随着信息网络的飞速发展，技术的不断成熟，IP网络凸显出很多其他技术不可替代的优点，使得它的应用范围不断扩大，承载的业务也不断增加，甚至有人预测未来的网络将进入全IP化时代。不管未来是否会全IP化，至少在将来很长一段时间里，运营商仍将提供基于IP的各种业务，故本文讨论的SLA参数将主要针对IP网络的业务。2.1 SLA参数框架 TMF 701最早提出SLA六类参数模型，后来又在GB917中进行了扩展和完善，该模型中SLA参数分为：技术/服务独立参数、技术特定参数、服务特定参数，每种参数又分为单个服务实例和总体服务要求两种类型。如表1所示。表1 六类参数模型的框架技术特定参数服务特定
4、参数技术服务/独立参数单个服务实例如物理接口细节如业务类型如最大故障时间总体服务要求月报参数如计费方式如对所有用户的可用性技术特定参数指那些与支持服务和应用的相关技术有关的参数；服务特定参数指与业务服务相关的参数；技术/业务独立参数是不直接属于服务性能的参数，如可用性、平均故障时间（MTBF）、电话平均响应时间等。随后在GB923中又提出了KPI（key performance indicator，关键性能指标）/KQI（key quality Indicator，关键质量指标）的概念，在GB917v4中延续了这个模型。KQI是服务的某个方面的服务质量的直接量度，而它是由多个称为KPI的度量因
5、子决定的。这些KPI度量因子是支撑该服务的服务资源（网络的或非网络的）和下层服务的性能的量度。同时KQI还可以进一步划分为产品KQI和服务KQI，图1反映了服务KQI和产品KQI，以及KPI的关系。图1 KQI/KPI关系2.2 SLA的层次结构在GB 917 v1.5当中就开始有初步的分层概念，区分了两大类的服务：网络承载服务（Network Bearer Service）和应用服务（Application Services）。GB917 v4.0对企业的服务应用进行了确切的层次结构划分，如图2所示。分为：业务应用（Business Application，BA）、业务服务（Business
6、 Service，BS）、网络服务（Network Service，NS）。业务应用是面向客户的最终产品，由多种业务服务共同组成，业务服务由网络服务提供，同时网络服务又是内部或外部的网络资源支撑，所以各层之间是相互依赖的。图2 SLA的层次结构在GB917 v4.0中列举了普遍的业务应用和基本的业务服务，并且详细分析了各种业务服务需要的网络服务及资源。而基于IP网络的业务服务常见的主要是：话音业务、办公自动化、用户帮助、远程工作、企业内部网（Intranet）、全局网（Extranet）以及公共互联网（Internet）服务。2.3 基于IP网络的SLA参数结合SLA的两种参数模型，按照层次结
7、构的思想分析SLA的参数，从层次结构的顶端开始逐层映射，最后得到统一的、可测量的参数集合，这是分析SLA参数的有效方法。KQI和KPI都可能写入SLA中，但是KQI是由KPI决定的，要最终得到KQI的值必须通过测量KPI，所以为了得到有效的SLA报告必须找到可测量的KPI。GB917 v4.0中给出具有一般性的服务KQI，这些KQI可以被用到某个特定的应用中。下面列出基于IP网络的业务服务相关的一般性服务KQI：l 话音业务：服务可用性、通话/视频质量、响应时间、往返延迟、延迟、机密性、不批判性、协同性、连接时间、降级l 办公自动化：服务可用性、响应时间、机密性、完整性、磁盘空间、帮助桌面、培
8、训、协同性l 用户帮助：服务可用性、通话/视频质量、响应时间、事物处理率、有效信息量、吞吐量、故障时间、关闭时间、呼叫持续时间、连接时间、降级l 远程工作：服务可用性、响应时间、机密性、不批判性、帮助桌面、培训、有效信息量、驳回l 企业内部网（Intranet）：服务可用性、响应时间、机密性、协同性、帮助桌面、有效信息量、驳回、l 全局网（Extranet）：服务可用性、响应时间、机密性、协同性、帮助桌面、有效信息量、驳回、磁盘空间、不批判性l 公共互联网（Internet）：服务可用性、响应时间、帮助桌面、有效信息量对不同的应用，或业务服务，因为侧重点和关注角度不一样，更重要的是，网络服务的
9、方式等下层资源的不同，同样的服务KQI映射为KPI的策略可能会有很大的差别。比如话音服务和办公自动化的服务KQI中都有响应时间（Response time），但对话音服务来说，响应时间可以直接从网络服务（IP）的响应时间（KPI）获得，而办公自动化的响应时间映射为KPI包括：客户端服务时间、服务器服务时间、窗口大小等多个指标。所以对具体的应用或业务服务的KQI到KPI的参数映射需要具体分析。事实上，KQI到KPI的映射过程并不是一步到位的，结合层次结构的思想，我们把映射过程也按照层次划分，如业务服务层，有服务KQI和服务KPI，如图3所示。图3 KQI、KPI及服务资源的关系图3表示了业务服务
10、的KQI、KPI与支撑该服务的服务资源之间的关系。企业的业务应用的实现需要得到业务服务的支持，而业务服务是由网络服务支撑的。每个业务服务的KQI提供了该服务某个特定方面的性能测度，其数据通过一定的数据来源获得，主要是服务的KPI。业务服务的KPI数据可以是从服务资源那里直接获得的，也可以是从支撑该服务的下层服务的KQI那里间接获得的。如果是从支撑服务那里取得的，就需要将该KQI映射为支撑服务的相应KPI，依此类推，整个映射过程可能是简单的，也可能是复杂的。以呼叫中心的话音服务为例，层次映射过程如图4所示。图4 KQI/KPI参数级别映射关系3. 小结现今，SLA已成为电信业发展的一个大热点，而
11、SLA管理中一个重要环节就是对SLA参数集和其具体取值进行合适地选取和确定，并不断地优化，但就目前的研究来说，理论还不足以正确指导这个过程，也没有一个统一的标准，这势必使SLA在执行过程中带来一些障碍，所以找到一个统一的、有效的SLA参数集仍是我们需要进一步研究的课题。参考文献 1 TMF.GB917 v1.5-2001，SLA management handbookS.2 TMF.GB917 v4.0-2004,SLA Management Handbook Volume 4:Enterprise Perspective.3 TMF.GB923 v3.0-2004，Wireless Serv
12、ice Measurements Handbook.4 张挺.IP网络的SLA服务等级协议探讨.江苏通信技术,2006(6).Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what
13、 it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my ti
14、me.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but rig
15、ht now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man ta
16、ke a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, kn
17、owing that if they would just line up in a vertical straight line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy
18、 who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon a
19、s the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications),
20、 Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less
21、 than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifti
22、ng even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 ki
23、lometers). Here, Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be travel
24、ing fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top
25、of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he
26、plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach s
27、peeds.Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
