Basic knowledge about vro technology and L2 Switch

With the development of China's routing industry, it also promotes the update and upgrade of router technology. Here we mainly explain the basic knowledge of router technology and L2 Switch. In order to adapt to the challenges brought by the deepening of network applications, the scale and speed of the network are rapidly developing. The speed of the LAN has increased from 10 Mbit/s to 100 Mbit/s, currently, Gigabit Ethernet technology is widely used.

In terms of network structure, it has also evolved from the LAN of shared media to the current LAN. The exchange LAN technology enables dedicated bandwidth to be exclusive to users, greatly improving the efficiency of LAN transmission. It can be said that in the network system integration technology, the first-layer interface and the second-layer exchange technology that are directly oriented to users have obtained satisfactory answers. However, as the core of the network, the router technology that acts as the interconnection between networks has no qualitative breakthrough. In this case, a new router technology came into being. This is the layer-3 Exchange Technology: it is a router because it can operate on the layer-3 of the network protocol, it is a type of routing that understands a device and can act as a route decision. It is a switch because it is extremely fast and almost achieves the second-layer switching speed. Who are the advantages and disadvantages of layer-2 switches, layer-3 switches, and routers? To answer this question, let's start with the working principles of these three technologies:

1. layer-2 Exchange Technology

A layer-2 switch is a device at the data link layer. It can read the MAC address information in the data packet and exchange it based on the MAC address. There is an address table inside the vswitch, which indicates the relationship between the MAC address and the vswitch port. When a vswitch receives a packet from a port, it first reads the source MAC address from the packet header so that it knows the port on which the machine with the source MAC address is connected, it then reads the destination MAC address in the packet header and finds the corresponding port in the address table. If there is a port corresponding to the destination MAC address in the table, the packet is copied directly to the port, if no corresponding port is found in the table, the packet is broadcast to all ports. When the target machine responds to the source machine, the switch can learn which port the target MAC address corresponds, the next time you transmit data, you no longer need to broadcast all ports.

The second-layer switch creates and maintains its own address table. Because L2 switches generally have a wide switching bus bandwidth, they can exchange data for many ports at the same time. If a L2 Switch has N ports, and the bandwidth of each port is M, and the bus bandwidth of the switch exceeds N × M, the switch can achieve line rate switching. The L2 Switch does not limit the broadcast packets. It copies the broadcast packets to all ports. Layer-2 switches generally contain ASIC Application specific Integrated Circuit Chip used to process data packet forwarding, so the forwarding speed can be very fast.

2. router technology

A Router operates at the network layer, the third layer in the OSI Layer-7 network model. There is a route table inside the router, which indicates where to go if you want to go somewhere. When a router receives a packet from a port, it first removes the packet header at the link layer), reads the destination IP address, searches for the route table, and determines where to send the next packet, then, the packet header of the link layer is packaged.) The packet is forwarded. If the next address cannot be determined, a message is returned to the source address and the packet is discarded.

Vro technology and layer-2 switching seem a bit similar. In fact, the main difference between routing and switching is that switching occurs at the layer-2 data link layer of the OSI reference model. This difference determines that different control information needs to be used for routing and exchange during data transmission. Therefore, the two methods to implement their respective functions are different.

The routing technology is actually composed of two basic activities, that is, determining the optimal path and transmitting data packets. Among them, data packet transmission is relatively simple and direct, while the route determination is more complex. The routing algorithm writes different information into the routing table. The router selects the optimal path based on the destination to which the data packet arrives and sends the data packet to the next vro that can reach the destination. When a router receives the packet, it will also view its target address and use the appropriate path to continue transmission to the subsequent router. And so on until the data packet reaches the final destination.

Vrouters can communicate with each other and maintain their route tables by transmitting different types of information. The route update information is generally composed of some or all route tables. By analyzing the route update information sent by other routers, the router can master the topology of the entire network. Link Status broadcast is another type of information transmitted between router technologies. It can send the link status and incoming notifications of information senders to other routers.