ipx互联网分组交换协议

X.25 is a packet-switched network technology used long before ago. X.25 is one of the first packet-switched network used to transmit data between multiple hosts. In this tutorial, we will define the X.25 protocol as well as the X.25 standard, history, network equipment, and components.

X.25是很久以前使用的一种分组交换网络技术。 X.25是用于在多个主机之间传输数据的第一个分组交换网络之一。 在本教程中，我们将定义X.25协议以及X.25标准，历史记录，网络设备和组件。

X.25分组交换 (X.25 Packet Switching)

As its name suggests X.25 is a packet-switching technology that is used to transmit data between different host locations. X.25 uses HDLC packets which also contains some information about the routing like source and destination address.

顾名思义，X.25是一种分组交换技术，用于在不同主机位置之间传输数据。 X.25使用HDLC数据包，其中还包含有关路由的一些信息，例如源地址和目标地址。

X.25标准 (X.25 Standard)

X.25 protocol is created by the International Telecommunication Union (ITU) in 1976. Originally X.25 is created to carry voice signals over the telephone lines. But later the capability of the X.25 is used for network and internet communication. X.25 encompasses the first 3 layers of the OSI Reference model which are Physical Layer, Data Link Layer, Network Layer. X.25 was a very popular late 1970s and 1980s among the telecommunication and IT world. The latest version of the X.25 standard is released in 1996.

X.25协议是由国际电信联盟(ITU)于1976年创建的。最初X.25的创建是为了在电话线上承载语音信号。 但是后来X.25的功能用于网络和Internet通信。 X.25包含OSI参考模型的前3层，分别是物理层，数据链路层，网络层。 X.25在1970年代和1980年代后期在电信和IT世界中非常流行。 X.25标准的最新版本于1996年发布。

X.25的特征 (Characteristics of X.25)

X.25 network protocol provides some characteristics.

X.25网络协议提供了一些特性。

• The packet size varies from 64 bytes to 4096 bytes where 128 bytes is the default packet size. If the packet size is different for multiple DTE and DCE the packets will be fragmented.
  数据包大小从64字节到4096字节不等，其中128字节是默认数据包大小。 如果多个DTE和DCE的数据包大小不同，则数据包将被分段。
• X.25 is a low-speed network for today’s internet speeds. X.25 provides speed around 100kbps and below.
  X.25是当今互联网速度的低速网络。 X.25提供大约100kbps及以下的速度。
• X.25 is used to create faster and newer network communication protocols like ATM and Frame Relay.
  X.25用于创建更快和更新的网络通信协议，例如ATM和帧中继。
• X.25 is a very robust protocol because it is debugged and inspected heavily from its creation from the 1970s. Literally there is no data error on modern X.25 networks.
  X.25是一种非常强大的协议，因为它从1970年代创建以来就经过大量调试和检查。 从字面上看，现代X.25网络上没有数据错误。
• Another problematic attribute of the X.25 protocol is its delay because of the DCE’s store and forward mechanism.
  X.25协议的另一个有问题的属性是由于DCE的存储和转发机制而导致的延迟。

X.25网络设备和组件 (X.25 Network Equipment and Components)

Some equipment and terms are used to fully implement the X.25 network. Here are some of the most important of them.

一些设备和术语用于完全实现X.25网络。 以下是其中一些最重要的内容。

• `Data Terminal Equipment (DTE)` is used on the end-user, device or host part in order to terminate the X.25 network.
  在终端用户，设备或主机部分使用“数据终端设备(DTE)”以终止X.25网络。
• `Data Circuit-Terminating Equipment (DCE)` is used to route the X.25 packets between DTE devices. Multiple DCE devices are used to connect the DTE’s and other DCE devices together.
  “数据电路终结设备(DCE)”用于在DTE设备之间路由X.25数据包。 多个DCE设备用于将DTE和其他DCE设备连接在一起。
• `Switched Virtual Circuits (SVC’s)` are like virtual connections between different DTE’s. They can be created by using different DCE’s to connect the same two DTE’s. Every time a transmission session will occur a new SVC is created.
  交换虚拟电路(SVC)就像不同DTE之间的虚拟连接。 可以通过使用不同的DCE连接相同的两个DTE来创建它们。 每次发生传输会话时，都会创建一个新的SVC。
• `Permanent Virtual Circuits (PVC’s)` are similar to the leased line where the connection is always established between two DTE’s. There is no need to set-up phase.
  “永久虚拟电路(PVC)”类似于租用线路，其中始终在两个DTE之间建立连接。 无需设置阶段。

X.25物理层 (X.25 Physical Layer)

The physical layer of the X.25 provides some communication lines which transmit electrical signals according to V.35, RS232, and X.21 standards. The physical layer is simply copper lines that are used for telephone communication.

X.25的物理层提供了一些通信线路，这些线路根据V.35，RS232和X.21标准传输电信号。 物理层只是用于电话通信的铜线。

X.25数据链路层 (X.25 Data Link Layer)

Data Link layer is one of the most important parts of the X.25 protocol. Data Link Layer provides error-free communication and transmission between two X.25 nodes. X.25 provides the error checking mechanism in each hop during transmission. This can create some delay. X.25 packets are generally shorter than other protocol packets which are generally 128 or 256 bytes.

数据链路层是X.25协议最重要的部分之一。 数据链路层提供了两个X.25节点之间的无错通信和传输。 X.25在传输过程中的每个跳中提供了错误检查机制。 这会造成一些延迟。 X.25数据包通常比其他协议数据包短，通常为128或256字节。

X.25网络层 (X.25 Network Layer)

X.25 network layer simply used to manage end-to-end communication between different DTE devices. The network layer also governs set-up and teardown and flow control between the DTE devices as well as routing function with multiplexing multiple logical or virtual connections ver single physical connection.

X.25网络层仅用于管理不同DTE设备之间的端到端通信。 网络层还通过在单个物理连接上复用多个逻辑或虚拟连接，来管理DTE设备之间的建立和拆除以及流控制以及路由功能。

翻译自: https://www.poftut.com/what-is-x-25-packet-switching-network-protocol/

ipx互联网分组交换协议