## 计算机代写|计算机网络代写computer networking代考|CS6250

2022年10月8日

couryes-lab™ 为您的留学生涯保驾护航 在代写计算机网络computer networking方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写计算机网络computer networking代写方面经验极为丰富，各种代写计算机网络computer networking相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础
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## 计算机代写|计算机网络代写computer networking代考|Protocol Layering

But enough about airlines. Let’s now turn our attention to network protocols. To provide structure to the design of network protocols, network designers organize protocols – and the network hardware and software that implement the protocolsin layers. Each protocol belongs to one of the layers, just as each function in the airline architecture in Figure $1.22$ belonged to a layer. We are again interested in the services that a layer offers to the layer above-the so-called service model of a layer. Just as in the case of our airline example, each layer provides its service by (1) performing certain actions within that layer and by (2) using the services of the layer directly below it. For example, the services provided by layer $n$ may include reliable delivery of messages from one edge of the network to the other. This might be implemented by using an unreliable edge-to-edge message delivery service of layer $n-1$, and adding layer $n$ functionality to detect and retransmit lost messages.
A protocol layer can be implemented in software, in hardware, or in a combination of the two. Application-layer protocols-such as HTTP and SMTP-are almost always implemented in software in the end systems; so are transport-layer protocols. Because the physical layer and data link layers are responsible for handling communication over a specific link, they are typically implemented in a network interface card (for example, Ethernet or WiFi interface cards) associated with a given link. The that just as the functions in the layered airline architecture were distributed among the various airports and flight control centers that make up the system, so too is a layer $n$ protocol distributed among the end systems, packet switches, and other components that make up the network. That is, there’s often a piece of a layer $n$ protocol in each of these network components.

Protocol layering has conceptual and structural advantages [RFC 3439]. As we have seen, layering provides a structured way to discuss system components. Modularity makes it easier to update system components. We mention, however, that some researchers and networking engineers are vehemently opposed to layering [Wakeman 1992]. One potential drawback of layering is that one layer may duplicate lower-layer functionality. For example, many protocol stacks provide error recovery on both a per-link basis and an end-to-end basis. A second potential drawback is that functionality at one layer may need information (for example, a timestamp value) that is present only in another layer, this violates the goal of separation of layers.

## 计算机代写|计算机网络代写computer networking代考|Networks Under Attack

The Internet has become mission critical for many institutions today, including large and small companies, universities, and government agencies. Many individuals also rely on the Internet for many of their professional, social, and personal activities. Billions of “things,” including wearables and home devices, are currently being connected to the Internet. But behind all this utility and excitement, there is a dark side, a side where “bad guys” attempt to wreak havoc in our daily lives by damaging our Internet-connected computers, violating our privacy, and rendering inoperable the Internet services on which we depend.

The field of network security is about how the bad guys can attack computer networks and about how we, soon-to-be experts in computer networking, can defend networks against those attacks, or better yet, design new architectures that are immune to such attacks in the first place. Given the frequency and variety of existing attacks as well as the threat of new and more destructive future attacks, network security has become a central topic in the field of computer networking. One of the features of this textbook is that it brings network security issues to the forefront.

Since we don’t yet have expertise in computer networking and Internet protocols, we’ll begin here by surveying some of today’s more prevalent securityrelated problems. This will whet our appetite for more substantial discussions in the upcoming chapters. So we begin here by simply asking, what can go wrong? How are computer networks vulnerable? What are some of the more prevalent types of attacks today?

# 计算机网络代考

.协议分层

## 计算机代写|计算机网络代写computer networking代考|Networks Under Attack

. com 今天，互联网已经成为许多机构的关键任务，包括大大小小的公司、大学和政府机构。许多人也依赖互联网进行许多专业、社交和个人活动。数十亿的“东西”，包括可穿戴设备和家用设备，目前正在连接到互联网上。但是，在所有这些实用和兴奋的背后，有一个黑暗的一面，“坏人”试图破坏我们的日常生活，破坏我们连接互联网的电脑，侵犯我们的隐私，并使我们赖以生存的互联网服务无法运行 网络安全领域是关于坏人如何攻击计算机网络，以及关于我们这些即将成为计算机网络专家的人如何保护网络不受这些攻击，或者更好的是，首先设计对此类攻击免疫的新架构。鉴于现有攻击的频率和种类，以及新的和更具破坏性的未来攻击的威胁，网络安全已经成为计算机网络领域的中心课题。这本教材的特点之一是把网络安全问题提了出来 由于我们还没有计算机网络和互联网协议方面的专业知识，我们将从今天一些比较普遍的安全相关问题开始。这将激发我们在接下来的章节中进行更多实质性讨论的欲望。所以我们从简单的问题开始，会出什么问题?计算机网络有多脆弱?现在比较普遍的攻击类型有哪些?

## 有限元方法代写

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。