Vswitch basic knowledge Summary

Exchange Technology Summary

1. Port Exchange Technology

Port switching technology first appeared in a slot hub. The backplane of a hub is usually divided into multiple Ethernet segments, each of which is a broadcast domain, networks do not communicate with each other. After the master module is inserted, it is usually allocated to the network segment of a backplane. Port switching is used to allocate and balance the Ethernet module ports among multiple network segments of the backplane. Based on the degree of support, port switching can also be subdivided:

Module switching: migrate the entire module to the network segment.

Port group switch: ports on the module are usually divided into several groups, and each group of ports allows network segment migration.

Port-level switch: each port can be migrated between different network segments. This switching technology is based on the first layer of OSI and has the advantages of flexibility and load balancing capabilities. If properly configured, fault tolerance can still be implemented to a certain extent, but the characteristics of the shared transmission media are not changed, and thus cannot be called a real exchange.

2. Frame Exchange Technology

Frame switching is currently the most widely used LAN switching technology. It provides a parallel transmission mechanism to reduce conflicting domains and obtain high bandwidth by performing differential segments on Traditional transmission media. Generally, the implementation technologies of each company's products are different, but there are generally the following processing methods for network frames:

Pass-through switching: Provides line rate processing capabilities. The switch only reads the first 14 bytes of the network frame and then transfers the network frame to the corresponding port.

Storage forwarding: Checks errors and controls the reading of network frames.

The exchange speed of the previous method is very fast, but it lacks more advanced control over network frames, lacks Intelligence and Security, and cannot support port exchange with different rates. Therefore, each vendor focuses on the latter technology. Some manufacturers even break down network frames and break down frames into fixed cells. This cell processing is easy to implement by hardware, and the processing speed is fast, at the same time, advanced control functions such as LET hub of MADGE can be completed, such as priority control.

3. Cell Exchange Technology

ATM technology uses a fixed length of 53 bytes of Cell Exchange. Because the length is fixed, it is easy to implement with hardware. ATM uses dedicated non-differential connections and runs in parallel. multiple nodes can be established through a switch at the same time, but the communication capability between each node is not affected. ATM also allows multiple virtual links at the source node, target node, and node to ensure sufficient bandwidth and fault tolerance. The statistical time-division circuit is used in ATM, which can greatly improve the channel utilization. The bandwidth of an ATM can reach 25 M, 155 M, M, or even several Gb. However, with the emergence of 10-ge Ethernet, the ATM technology, which once represents the future direction of the development of network and communication technologies, began to lose its meaning.

Q & A about vswitches

What does a vswitch do?

A: The switch performs three tasks: forwarding data packets, flooding data packets, and discovering new MAC addresses.

What is a MAC table? How is it generated and used?

Answer: 1) the MAC table is like the phone book (yellow page), the phone book record (name, phone number), and the MAC Table Record (MAC, interface ).

2) When the switch receives a packet, it searches for the MAC table with its MAC destination address. If the data packet is found, the data packet will be forwarded. If the data packet is not found, the data packet will be flooding.

3) When a packet is received, the switch uses its MAC source address to query the MAC table. If the packet is not found, a new address is found, and the address and input interface are added to the MAC table. In this way, the MAC table increases with the new data stream, and the generated entries (MAC, Interface) can be used to forward data packets.

Why do vswitches need to be flooded?

A: The network is often used for flood searches. The bureau network features broadcast and flood, while the switch is a bureau network device, which is convenient and efficient. A vswitch uses a MAC table to forward data packets. If the table does not have a destination MAC, data cannot be forwarded, but data is generally transmitted. Without knowing the switch path, flood can quickly send data packets to the destination. At the same time, flood side effects also have different measures to control.

Will the same MAC be input from different interfaces? What should I do with a vswitch?

A: Yes. However, the MAC table only keeps one MAC. For example, if MAC1 is input from F0/1 for the first time, a new entry (MAC1, F0/1) is added to the MAC table ). Later, MAC1 is input from F0/5 of another interface. This MAC table does not add new entries, but updates (MAC1, F0/1) to (MAC1, F0/5 ).

Under what circumstances will the same MAC input from different interfaces?

A: loop. For example, S1, S2, and S3 are connected to a triangle. H1 is connected to S1 and H2 is connected to S2, which causes flooding on the three switches. For example, if H1 is pingh2, the MAC table is empty. S2 will find that ping comes in from two different input interfaces.

Does the entry in the mac table of the vswitch have a validity period?

A: Yes. It takes about 5 minutes. The MAC table only stores active MAC. If the switch does not receive the packet sent from a node within a few minutes, the switch clears the MAC of the node from the MAC table ..

How many MAC can be placed in the mac table of a vswitch? Answer: It depends on the model and price, from 4 K to 1 M (1024 K ).

Do you understand the three descriptions of exchange technology? This article is the basic knowledge, readers should not be too troubled in understanding, if still not clear, this site also has a lot of related resources for you to read: http://network.51cto.com/switch/