The difference between a traditional vswitch and a modern vswitch

The difference between a traditional vswitch and a modern vswitch

Some vswitches on the market claim to have QoS Assurance. In fact, they only support single-level priority settings and do not form a loop logically. In the event of a fault, the backup link is enabled, I would like to share it with you here and hope it will be useful to you.

We often mention that the traditional Ethernet switch is actually a multi-port L2 network device based on the bridge technology, it provides low-latency and Low-overhead channels for data frame forwarding from one port to another. A router is a group exchange device (or network layer Relay Device) in the network layer of the OSI protocol model. The basic function of a router is to transmit data (IP packets) to the correct network, including:

1. IP datagram forwarding, including path finding and transmission of the datagram;

2. subnet isolation to prevent broadcast storms;

3. Maintain the route table and exchange route information with other routers. This is the basis for IP packet forwarding.

4. IP datagram error handling and simple congestion control;

5. Filtering and accounting of IP datagram.

Differences between vswitches and vrouters

Traditional switches are developed from bridges and belong to the OSI Layer 2 (data link layer device. It selects routes from the station table based on MAC address addressing. The establishment and maintenance of the station table is automatically implemented by the switch. A router is a layer-3 network-layer device of OSI. It is addressing based on IP addresses and is generated through the route table routing protocol.

The biggest advantage of a vswitch is that it is fast. Because the vswitch only needs to identify the MAC address in the frame, the selection of forwarding Port Based on the MAC address is simple, Which is easy for ASIC implementation. Therefore, the forwarding speed is extremely high. However, the working mechanism of vswitches also brings about some problems.

1. Loop:Based on the vswitch address learning algorithm and the station table algorithm, no loops are allowed between vswitches. Once a loop exists, the Spanning Tree Algorithm must be enabled to block the ports that generate the loop. The router routing protocol does not solve this problem. There are multiple channels between routers to balance the load and improve reliability.

2. Load concentration:There can only be one channel between switches, so that information is concentrated on one communication link and cannot be dynamically allocated to balance the load. The router routing protocol algorithm can avoid this. The OSPF routing protocol algorithm can not only generate multiple routes, but also select different optimal routes for different network applications.

3. Broadcast control:A vswitch can only narrow down the conflicted domain, but not the broadcast domain. The entire exchange network is a large broadcast domain, where broadcast packets are scattered across the entire exchange network. Vrouters can isolate broadcast domains, and broadcast packets cannot be broadcast through vrouters.

4. subnet division: The vswitch can only recognize MAC addresses. The MAC address is a physical address and uses a flat address structure. Therefore, you cannot divide subnets Based on the MAC address. Vro identifies IP addresses. IP addresses are allocated by network administrators. They are logical addresses and IP addresses have hierarchies. They are divided into network numbers and host numbers, which can be easily used to divide subnets, the main function of a vro is to connect to different networks.

5. Confidentiality issues: Although traditional switches can filter Frames Based on the source MAC address, target MAC address, and other frames, however, the vro filters packets based on the source IP address, destination IP address, and TCP port address of the packets, making them more intuitive and convenient.

6. media-related: A switch can also be used as a bridge device to convert between different link layers and physical layers. However, this conversion process is complicated and is not suitable for ASIC implementation and will inevitably reduce the forwarding speed of the switch. Therefore, currently, vswitches primarily Interconnect Networks with the same or similar physical media and link protocols.

Instead of connecting networks with very different physical media and link layer protocols, routers are different. They are mainly used for interconnection between different networks, therefore, it can connect networks with different physical media, link layer protocols, and network layer protocols. Although a vro has a functional advantage, it is expensive and has a low packet forwarding speed.