Knowledge about hubs and switches
Ethernet is the current local area network with the most common communication protocol standards. This standard defines in the local area network (LAN...
Ethernet is the most widely used LAN technology, is a kind of local area network system, using CSMA/CD network access method.
Ethernet is the current local area network with the most common communication protocol standards. This standard defines in the local area network (LAN) type of cable and signal processing method used in the. Ethernet in the interconnection between devices at the rate of 10~100Mbps transport packets, twisted pair cable, 10 Base T Ethernet because of its low cost, high reliability and the rate of 10Mbps and become the most widely used Ethernet technology. Wireless Ethernet to 11Mbps DS, many manufacturing suppliers can communicate using a common protocol software, open the best.
△ Ethernet connection
Topological structure:
Star: network equipment management convenient, easy to expand, the need for special as the core node, the network needs more cable, the reliability of the core set of requirements of high. The network of special equipment (such as RS485 hub or switch) as the core node, through twisted pair to the hosts in the LAN connected to the core node, it will form the star type structure.
Star network while the need for cable than bus type wiring and connectors, but cheaper than the bus. In addition, a star topology can be cascaded mode is very convenient to expand the network to a large scale, so it is used widely, used by most of the ethernet. Transmission media: Ethernet can use a variety of connection medium, including coaxial cable, twisted pair and optical fiber.
The twisted pair is used for the connection from the host to the hub or switch, and the optical fiber is used to switch between the cascade and switch to inter router point-to-point link.
The twisted pair is used for the connection from the host to the hub or switch, and the optical fiber is used to switch between the cascade and switch to inter router point-to-point link. Coaxial cable as the main connection medium early are gradually eliminated. What is the hub?
The hub English name is HUB, from the literal meaning can know its function, is the line set up.
HUB works in the physical layer, multiple devices can use the twisted pair to connect HUB to realize the interconnection of physical layer.
Internal HUB or the bus sharing technology, so the use of CSMA/CD technology to interact, it receives data on radio, all connected to the HUB device to receive and read Is it right? Own bag.
Hub with repeaters are the same as the physical layer network equipment.
Disadvantages are: shared Ethernet due to all of the nodes are connected in the same collision domain, whether a frame where you come from or where to go, all the node can receive the frame. As nodes are added, a lot of conflicts will lead to network performance degradation. And the hub and transmit only one data frame, this means that the RS485 HUB hub all ports are to share the same bandwidth.
What is the switch?
As mentioned above, HUB works in the physical layer, to interact with CSMA/CD technology, is broadcast, conflict.
A switch at the data link layer, there are a few points to know:
(1) Ethernet switches within a digital cross network, rather than a shared bus. The advantage is that the terminal is temporarily connected, interactive data independent of each other.
(2) each port has the transmission line and line, each with a buffer, can send to temporarily cache terminal data, such as line resources idle after sending data.
(3) can be done according to the port forwarding, the principle is to switch according to the data frame in the head of the destination MAC address to find the port, the port connecting equipment only accept the data frame, which avoids a lot of conflict.
The working process of switch are as follows:
(1) all the data frame received each port on the network.
(2) to establish the MAC address table by the source MAC address data frames received in (that is, the source address learning), use the address maintenance address ageing mechanism.
(3) in the MAC address lookup table frame in the destination MAC address. If found, it will be sent to the destination MAC address where the port equipment (not including the original port). If not, then; to all ports to send (not including the original port).
(4) for broadcast frames and multicast frames to all port forwarding.
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