Network Knowledge Supplement 2

SDH is the most widely used optical transmission network. It features high bandwidth, strong anti-interference, and high scalability.
In a specific network connection, the general service provider places the cable at the user's place, and the user places the cable with a modulation device (common Modem

, DTU or baseband modem), and then our network edge settings (usually vrouters) are connected with the modulation device. But some lines

A vro has a built-in device that can directly connect to the cables deployed by the service provider, such as Ei/ATM.

Wan can be divided into X.25, frame relay, ATM, and ISDN networks by line type. as a result, the routers also have the same asynchronous serial port, ATM interface, isdn bri interface, bri/pri interface, and so on.

Currently, VRP supports the following Wan interfaces: asynchronous serial port, synchronous serial port, isdn bri interface, and CEI/pri interface. there are two asynchronous serial ports in VRP. One is to set the same or asynchronous serial ports to work in asynchronous mode, and the interface name is serial; the other is dedicated asynchronous serial ports, and the interface name is async.

The asynchronous serial port can be set to a leased line or a dialing method. the dialing method is more commonly used in applications. When an asynchronous serial port is connected to an external modem or ISDN Ta, it can be used as a dialing interface. It encapsulates the Link Layer Protocol slip or PPP and supports network protocols such as IP and IPX.

Synchronous Serial Port features:

It can work in the DTE and DCE modes. Generally, the synchronous serial port of the router works in the DTE mode and receives the clock provided by the DCE device.

Synchronous serial ports can be connected to multiple types of cables, such as V.24 and V.35. VRP can automatically detect the types of external cables for synchronous serial ports and select the electrical characteristics. In general, manual configuration is not required. the link layer protocols supported by synchronous serial ports include PPP and frame relay. lapb, X.25, and so on. supports IP and IPX network layer protocols.

You can run the display interface serial command to view the current external cable type of the synchronous serial port and the working mode (MHD/DCE.

Quidway series routers use V.24 interface cable appearance. v.24 cables are divided into DTE cables and DCE cables. one end of the V24 DCE cable is a 50-pin plug (connected to a router) and the other is a 25-hole plug (external network segment ). the V24 cable conforms to the EIA-RS-232 interface standard, and can work in both synchronous and asynchronous modes, so it can be connected asynchronously with the common analog modem and ISDN terminal adapter. you can also connect to the baseband modem for synchronous connection. in asynchronous mode, the link layer protocol PPP is encapsulated, and the network layer protocol IP address and IPX are supported. The maximum transmission rate is 115200bps. In synchronous mode, X.25, frame relay, PPP, HDLc, slip, lapb, and other link layer protocols support IP and IPX, while the highest transmission rate is only 64000bps.

V.24 The cable interface is divided into the DCE and DTE sides, corresponding to the data circuit device (network side) and data terminal device (user side), corresponding to the DCE side is the socket (25 holes ), the DTE side is a plug (50-pin ). vrouters belong to DTE-side devices, and various modem and ISDN terminal adapters belong to DCE devices.

In the V.35 interface procedure, the common interfaces of quidway series routers will also be used as an example, from their mechanical characteristics, electrical characteristics, common control signals, transmission rates, transmission Distance and interface cable.

V.35 cable interface characteristics in strict accordance with the EIAFFIA-V.35 standards, the router end for db50 connector, external network segment for 34-pin connector, also atmosphere DCE and DTE two, the corresponding DCE side is the socket C34 hole, and the DTE side is the plug (34-pin ).

V.35 cables are generally used only for synchronous transmission of data. They can encapsulate link layer protocols, such as X.25, frame relay, PPP, slip, and lapb, and Support Network Layer Protocol IP and IPX, the V.35 cable is usually used to connect a vrov.to a baseband modem. In this mode, the vro is always on the DTE side, the same as the V.24 cable.

The pins corresponding to these control signals comply with RS-232 level standards, whether in V.24 or V.35 interface procedures.