fabric是什么意思，Fabric核心概念介绍之Fabric网络？

下面我们来学习Fabric的网络。在这里我贴出了英语原文，英语不好的小伙伴可直接看中文（翻译的不贴切的地方，请多多指教）。本系列教程上中下三部分。在本节我们先来学习下“什么是Fabric网络”，“fabric网络在公司应用中的例子”，“网络的组件”和“如何创建一个Fabric网络”。

什么是Fabric网络？

Fabric网络是具有权限管理的区块链网络，技术架构上为消费者和管理员提供分布式的账本服务。在大部分情况下，在一个联盟中，最初配置时是需要有网络管理权限的。并且，联盟中的成员达成一致后，策略是可以改变的。

A Fabric permissioned blockchain network is a technical infrastructure that provides ledger services to application consumers and administrators. In most cases, multiple organizationscome together as a consortium to form the network and their permissions are determined by a set of policies that are agreed to by the consortium when the network is originally configured. Moreover, network policies can change over time subject to the agreement of the organizations in the consortium.

公司应用区块链网络的一个例子

有RA,RB,RC和RD四个组织决定利用Fabric网络进行共同投资。组织RA将会部署3个Peer节点和2个客户端应用。组织RB将会部署4个Peer节点和一个客户端应用。组织RC将会部署3个Peer节点和两个客户端应用。组织RD将会部署4个排序节点。RA和RB之间可以形成一个联盟，并且建立一个通道在他们之间。同理，RC和RD也可以这么做。每个应用通道又可以配置自己的策略。

The organizations RA, RB, RC and RD have decided to jointly invest in a Fabric blockchain network. Organization RA will contribute 3 peers, and 2 client applications of RA will consume the services of the blockchain network. Organization RB will contribute 4 peers and has 1 client application. Organization RC contributes 3 peers and has 2 client applications. Organization RD contributes 4 orderers. Organization RA and RB have decided to form a consortium and exploit a separate application channel between the two of them. Organization RB and RC have decided to form another consortium and also exploit a separate application channel between the two of them. Each application channel has its own policy.

网络的组件

一个Fabric网络由以下部分组成：

• 账本（每个通道都有一个，由区块链和状态数据库组成）
• 智能合约（在Fabric网络中也称为链码）
• Peer节点
• 排序服务
• 通道
• Fabric证书颁发机构

网络服务的消费者

• 属于组织的客户端应用；
• 区块链网络管理员的客户端；

网络的策略和身份

Fabric证书颁发机构（CA）颁发证书，让组织验证身份。组织中有一个或者多个CA，可以选择一个去使用。除此之外，客户端应用使用证书去认证交易提案，peer节点使用证书去为提案背书并且把合法的交易提交到账本。

The Fabric Certificate Authority (CA) issues the certificates for organizations to authenticate to the network. There can beone or more CAs on the network and organizations can choose to use their own CA. Additionally, client applications owned by organizations in the consortium use certificates to authenticate transaction proposals, and peers use them to endorse proposals and commit transactions to the ledger if they are valid.

Fabric网络实例（来源Fabric官方文档）

上面图表的解释如下：Fabric网络N中有策略网络NP1，排序服务O。通道策略CP1管理通道C1。联盟RARB建立了通道C1，排序服务O管理通道C1，peer节点P1和P2和客户端节点A1和A2在通道C1上可以进行交易。客户端应用A1属于组织RA。证书颁发机构CA1为组织RA服务。P2维护账本L1和L2。P2利用链码S4和S5。排序服务节点O属于组织RD.。

The explanation of the diagram is as follows: There is a Fabric network N with network policy NP1 and ordering service O. Channel C1 is governed by channel policy CP1. Channel C1 has been established by consortium RARB. Channel C1 is managed by ordering service O and peers P1 and P2 and client applications A1 and A2 have been granted permission to transact on C1. Client application A1 is owned by organization RA. Certificate authority CA1 serves organization RA. Peer P2 maintains ledger L1 associated with channel C1 and L2 associated with C2. Peer P2 makes use of chain code S4 and S5. The orderer nodes of ordering service O are owned by organization RD.

创建网络

网络的创建是由客户端，peer节点，channel通道和ordering服务节点的联盟创建的。排序服务是网络中的地位十分重要，因为它包含着网络中的通道的配置。每个通道的配置包含通道的策略和membership信息（比如X509根证书）。

创建Fabric网络（图片来自Fabric官方文档）

The network is created from the definition of the consortium including its clients, peers, channels, and ordering service(s). The ordering service is the administration point for the network because it contains the configuration for the channel(s) within the network. The configurations for each channel includes the policies for the channel and the membershipinformation (in this example X509 root certificates) for each member of the channel.

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