Synchronous systems and asynchronous systems

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In a synchronous system, all service signals from service boards to cross-connect boards are synchronous (same frequencies and aligned frame headers), and both time-division and space-division cross-connections can be implemented inside cross-connect chips.
In an asynchronous system, service signals from service boards to cross-connect boards are asynchronous (different frequencies and unaligned frame headers). Services are independent of each other, and only space-division cross-connection can be implemented inside cross-connect chips.
The OSN 8800 is a synchronous system, while the OSN 6800 is an asynchronous system.

Other related questions:
Whether service provisioning is affected if a synchronous device is added to an OTN ring of an asynchronous system
A synchronous system and an asynchronous system can be interconnected with each other.

Describe the synchronous and asynchronous cables used by AR routers
AR routers support the following three types of 8AS cables: 1. Straight-through cables, which apply to financial scenarios where dumb terminals are used X1 Signal Direction X2 (Female connector) 1 DCD �? 1 2 DTR �? 2 3 DSR �? 3 4 GND - 4 5 RXD �? 5 6 TXD �? 6 7 CTS �? 7 8 RTS �? 8 2. Asynchronous serial cables, which apply to common scenarios X1 (Male connector) Signal Direction X2 (Female connector) 1 DCD �? Blue 2 DTR �? Orange 3 DSR �? White and brown 4 GND - White and blue 5 RXD �? Green 6 TXD �? White and green 7 CTS �? Brown 3. Adapter cables, which are used together with the preceding two types of cables and apply to telecommunication or common scenarios X1 (Male connector) Signal Direction X2 (Female connector) 1 DCD �? Blue 2 DTR �? Orange 3 DSR �? White and brown 4 GND - White and blue 5 RXD �? Green 6 TXD �? White and green 7 CTS �? Brown 8 RTS �? White and orange 4. Self-made cables, which are used in serial port server scenarios X1 Signal Direction X2 (Female connector) 1 DCD �? 4 2 DTR �? 7 3 DSR �? 2 4 GND - 5 5 RXD �? 3 6 TXD �? 6 7 CTS �? 1 8 RTS �? 8

Initial synchronization of OceanStor V3 storage systems
Initial synchronization of remote replication for OceanStor V3 storage systems can be performed online.

Description of synchronous/asynchronous serial interfaces of AR routers
The serial interface is one of the most commonly used WAN interfaces. A serial interface can work in synchronous mode or asynchronous mode. Therefore it is also called the synchronous/asynchronous serial interface. Devices support the following synchronous serial interfaces: - Synchronous interfaces generated from synchronous/asynchronous serial interfaces that work in synchronous mode, which are named as Serial Devices support the following asynchronous serial interface: - Asynchronous interfaces generated from synchronous/asynchronous serial interfaces that work in asynchronous mode, which are named as Serial - Dedicated asynchronous serial interfaces which are named as Async 1. Serial interfaces have the following features in synchronous mode: - Serial interfaces can work in data terminal equipment (DTE) mode or data circuit-terminating equipment (DCE) mode. Devices on which DTE cables are connected to the serial interface are named as DTE devices. Devices on which DCE cables are connected to the serial interface are named as DCE devices. In general, devices are used as DTE devices and receive the clock provided by DCE devices. - Serial interfaces support the following link-layer protocols: PPP, X.25, LAPB, FR, and HDLC. - Serial interfaces support protocols in the IP network layer. 2. In asynchronous mode, serial interfaces can work in protocol mode or stream mode. ? Protocol mode - In protocol mode, after the physical link of a serial interface is established, the serial interface uses the existing link-layer protocols to configure parameters and establish the link. - In protocol mode, the type of link-layer protocol is PPP. - In protocol mode, serial interfaces support protocols in the IP network layer. ? Stream mode - In stream mode, when the devices connected to both ends of a serial interface begin to interact with each other, a device can send configuration information to the peer device to configure the physical-layer parameters of the peer device and establish the link. - In stream mode, serial interfaces do not support protocols in the IP network layer or link layer.

What Is the Difference Between Synchronous Remote Replication and Asynchronous Remote Replication
Both synchronous remote replication and asynchronous remote replication can be used in disaster recovery solutions implemented by storage systems to back up data remotely. However, they are implemented in different ways and applicable to different service scenarios. Implementation modes are describes as follows: ? Synchronous remote replication: When a host writes data to the primary LUN, a write request is also sent to the secondary LUN. After both LUNs return a response indicating a successful I/O write, the primary storage system sends the host a response indicating a successful I/O write, implementing real-time data synchronization between the primary LUN and the secondary LUN. ? Asynchronous remote replication: When writing data to the primary LUN, the primary storage system records the changed data. After the primary LUN returns a response indicating a successful write, the primary storage system sends the host a response indicating a successful write. Then, data synchronization is triggered by a user manually or by the system based on user-defined trigger conditions to ensure data consistency between the primary LUN and the secondary LUN. Service scenarios are described as follows: ? Synchronous remote replication requires high bandwidth and low data latency. Therefore, synchronous remote replication is typically used in disaster recovery scenarios where the primary and secondary storage systems are adjacent to each other, such as the intra-city data backup and disaster recovery scenario. ? Asynchronous remote replication is not demanding on bandwidth and data latency. Therefore, asynchronous remote replication is applicable to disaster recovery scenarios where the primary and secondary storage systems are far away from each other or the network bandwidth is limited.

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