WAN Aggregator QoS Design

This section discusses WAN QoS considerations and designs, including the following: • Slow-speed (≤ 768 kbps) WAN link design • Medium-speed (768 kbps to T1/E1 speed) WAN link design • High-speed (> T1/E1 speed) WAN link design

QoS Design

QoS Design Principles: One design principle is to always enable QoS policies in hardware rather than software whenever a choice exists as QoS in software places incremental loads on CPU. Classification and Marking Principles: In order to provide end-to-end Differentiated Services and PHBs, Cisco recommends to classify and mark applications as close to their sources …

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QoS Requirement for Applications

QoS Requirements for Voice Voice Bearer Traffic: Voice quality is directly affected by all three QoS quality factors: loss, latency and jitter. Cisco DSP can use predictor algorithms to compensate for up to 30ms loss of voice samples.  So, two or more voice packets loss will cause noticeable voice quality degradation. A summary of the …

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Quality of Service

Cisco IOS QoS features are a solution for delay, jitter, packet loss and bandwidth utilization in the IP network. Cisco IOS features including below toolsets; Classification and Marking tools: allow traffic to be partitioned into multiple priority levels, or classes of service based on the input interface, ACLs, policy defined or NBAR for layer 7 …

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无源光网络技术PON

什么是PON 光纤接入从技术上可分为两大类:有源光网络(AON,ActiveOptical Network)和无源光网络(PON,Passive Optical Network)。PON是一种点到多点的光纤接入技术,它由局侧的OLT(光线路终端)、用户侧的ONU(光网络单元)以及ODN(光分发复用网络)组成。一般其下行采用TDM广播方式、上行采用TDMA(时分多址接入)方式,而且可以灵活地组成树型、星型、总线型等拓扑结构(典型结构为树形结构)。所谓“无源”,是指ODN中不含有任何有源电子器件及电子电源,全部由光分路器(Splitter)等无源器件组成,消除了局端与客户端之间的有源设备,它能避免外部设备的电磁干扰和雷电影响,减少线路和外部设备的故障率,提高系统可靠性,同时可节省维护成本,是电信维护部门长期期待的技术。

视频知识-图像显示格式

颜色编码方式YUV与RGB YUV(亦称YCrCb)是被欧洲电视系统所采用的一种颜色编码方法(属于PAL),是PAL和SECAM模拟彩色电视制式采用的颜色空间。其中的Y,U,V几个字母不是英文单词的组合词,Y代表亮度,uv代表色差,u和v是构成彩色的两个分量。在现代彩色电视系统中,通常采用三管彩色摄影机或彩色CCD摄影机进行取像,

视频知识-视频压缩编码格式

ITU标准 H.261 H.261又称为P*64,其中P为64kb/s的取值范围,是1到30的可变参数,它最初是针对在ISDN上实现电信会议应用特别是面对面的可视电话和视频会议而设计的。实际的编码算法类似于MPEG算法,但不能与后者兼容。H.261在实时编码时比MPEG所占用的CPU运算量少得多,此算法为了优化带宽占用量,引进了在图像质量与运动幅度之间的平衡折中机制,也就是说,剧烈运动的图像比相对静止的图像质量要差。因此这种方法是属于恒定码流可变质量编码。H.261标准是为ISDN设计,主要针对实时编码和解码设计,压缩和解压缩的信号延时不超过150ms,码率px64kbps(p=1~30)。只支持两种图像扫描格式:QCIF和CIF。

视频知识-视频信号制式

常见的电视信号制式是PAL和NTSC,另外还有SECAM等。NTSC即正交平衡调幅制,PAL为逐行倒像正交平衡调幅制,均采用隔行扫描。PAL和NTSC制式区别在于节目的彩色编、解码方式和场扫描频率不同。中国(不含香港地区)、印度、巴基斯坦等国家采用PAL制式,美国、日本、韩国以及我国台湾地区等采用NTSC制式。