Stroll in the Cloud Network (i)

Before reading this article, it is best to understand the following:

Understanding OpenStack will help to understand this article. This article explains the general principle method of Linux virtual network, although it is not limited to application in OpenStack, but the experiment of this paper is based on OpenStack. OpenStack is an open source IaaS cloud that you can begin to familiarize yourself with from the Devstack script (http://devstack.org/).

Understanding QEMU will also help to understand this article. QEMU is a machine emulator that supports multiple CPUs, and this article uses QEMU to create virtual machines to validate the tests in this article.

What is a cloud?

What is a cloud? My understanding is that a dynamically scalable server cluster that provides multiple tenants with services at all levels, such as the operating system layer, the middleware layer, the application layer, and so on, is called the cloud. So the cloud has large-scale, highly scalable, on-demand services, automation, energy saving and environmental protection, high reliability and so on. The following Figure 1 outlines the architecture of the cloud from the software stack perspective:

Figure 1. The architecture of the cloud

IaaS, infrastructure as a service, infrastructure services: You can simply understand that a scalable operating system (virtual machine or real machine) instance is sold to multiple tenants as an infrastructure service and costs are calculated on demand. Of course, the operating system as an infrastructure service is only one of the IaaS, and is the most important one, I am afraid that the concept of confusion so we only focus on this. In fact, as long as the infrastructure provides services, the concept should be called IaaS, for example, relational databases, if it is a cluster deployment, it is also the infrastructure services, it should be called IaaS. Such products such as IBM's Smart Cloud Entry, such as open source OpenStack.

PaaS, Platform as a service, platform as services: You can simply understand to sell scalable middleware resources as platform services to multiple tenants and then calculate costs on demand. For example, a PaaS can automatically launch an operating system instance provided by IaaS in real time, and then automatically deploy the middleware application server (such as IBM's WebSphere) on top of the SaaS application, and then deploy a set of SaaS application instances, if the concurrency is increased instantaneously and automatically integrate them into the load balancing system, so as to realize the automatic scaling of platform services, which is PaaS. Such products such as IBM's IWD, such as Google's App Engine.

SaaS, Software as a service, software as services: You can simply understand that scalable distributed software as a software service to provide users with some kind of online services, such as video services, map services.

XaaS, X as a Server, everything is service: as long as it is to provide multiple tenants on-demand services can be called XaaS, like in OpenStack, the network part of the code to separate the composition of the Quantum project, you can call the network as a service (NaaS, Netwo RK as a service); Like using XCat automatic deployment of bare metal can be called bare metal as a service (MaaS, bare-metal as a services).

What is a network in the cloud?

In traditional data centers, each network port corresponds to only one physical machine; with the cloud, a physical network card may host multiple virtual network adapters. The relationship between the physical network card and the virtual NIC is the following three situations:

One-to-one, a physical network card corresponding to a virtual network card, is the next one of the many cases of a special case

A one-to-many, a physical network card corresponding to multiple virtual network card, this article is to introduce the situation

Multi-pair, multiple physical network corresponding to a virtual network card, that is, we often say bonding, used as load balancing

Figure 2. The main content of virtual network

Figure 2 above shows the main contents of the virtual network: