With more and more high requirements for video image quality, more and more large video transmission flow, more and more complex monitoring and application environment, the security monitoring of large traffic video signal transmission requirements for real-time, integrity and fluency is increasing. In the face of massive high-definition video transmission and network problems, engineers and integrators call: Ordinary network PoE switches have completely failed!
Traditional switches are developed from bridges and belong to the second layer of OSI, the data link layer device. It addresses according to the MAC address, selects routes through the station table, and the establishment and maintenance of the station table is automatically performed by the switch. The router belongs to the third layer of OSI, the network layer device, which is addressed according to the IP address and is generated by the table routing protocol.
1. Loop: An algorithm is established based on the exchange address learning and the station table. No loops are allowed between switches. Once a loop exists, the spanning tree algorithm must be started to block the port where the loop is generated. The router's routing protocol does not have this problem. There are multiple paths between routers to balance the load and improve reliability.
2. Load concentration: There can only be one path between switches, so that information is concentrated on one communication link and can not be dynamically distributed to balance the load. The router's routing protocol algorithm can avoid this. The OSPF routing protocol algorithm can not only generate multiple routes, but also select different best routes for different network applications.
3. Broadcast control: Switches can only narrow the conflict domain, not the broadcast domain. The entire exchange network is a large broadcast domain, and the broadcast message is scattered to the entire exchange network. The router can isolate the broadcast domain, and the broadcast message can not continue broadcasting through the router.
4. Subnetwork division: Switches can only recognize MAC addresses. The MAC address is a physical address and uses a flat address structure, so the molecular network can not be drawn according to the MAC address. The router recognizes the IP address. The IP address is assigned by the network administrator. It is a logical address and the IP address has a hierarchical structure. It is divided into a network number and a host number. It can be easily used to divide the molecular network. The main function of the router is to connect. Different networks.
5. Confidentiality issues: Although the switch can also filter frames based on the source MAC address, destination MAC address, and other frames, However, the router filters the message according to the source IP address, destination IP address, TCP port address, etc., which is more intuitive and convenient.
6. Medium correlation: As a bridge device, the switch can also complete the conversion between different link layers and physical layers. However, this conversion process is relatively complex and is not suitable for ASIC implementation, which will inevitably reduce the forwarding speed of the switch. Therefore, at present, switches mainly complete network interconnection of the same or similar physical media and link protocols, and are not used to interconnect networks with very different links between physical media and link layer protocols. The router is different. It is mainly used for interconnection between different networks, so it can connect networks with different physical media, link layer protocols, and network layer protocols. Although the router has an advantage in functionality, it is expensive and the message forwarding speed is low.
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