We began to talk about network devices, switches, routers, bridges from Ethernet
Ethernet data transmission is a shared bus using CSMA / CD (Carrier Sense Multiple Access with Collision Detection): with Collision Detection Carrier Sense Multiple Access technology. In layman's terms, the Ethernet, all nodes share the transmission medium, transmission procedure of each node is: Listen Before Send, conflict is suspended, the random retransmission delay. If there are two Ethernet data in a time frame simultaneously, the two will destroy each other, leading to transmission failure.
Collision domain (collision domain) refers to a group of computers, the same time within the group, only one host send (unicast) packets. Or that only one host to send data, the other hosts in the group after it has been sent to wait to send. Broadcast domain (broadcast domain) is sent (broadcast) Times article, the computer group to receive the packet.
Conflict and broadcast domains repeater is the same, is the entire network.
Hub (multiport repeater can be seen as the) conflict and broadcast domains is the same, is the hub of all ports (computer groups under).
Each port bridge (usually two) is a collision domain, all ports belong to the same broadcast domain.
Switcher (can be seen as a multi-port bridge) is a vlan is a broadcast domain, a port is a collision domain vlan's. (Not involved in the cascade scene)
Each port of the router (or switch to start three port three functions) is a broadcast domain. If the port is connected to an Ethernet LAN, each port is a collision domain.
Level in terms of the work, repeaters and the physical layer to hubs, bridges, and the working link layer switcher, three switches and routers in the network layer. (Note: refers to the physical layer in the OSI model, the link layer and network layer refers to the TCP / IP four-layer model where we usually say that the story is actually a TCP / IP layer model in other words.! , the link layer under TCP / IP four-layer model is the equivalent of a physical layer complements the OSI model.)
From the forward to achieve in terms of bridges need a mac table, the switcher requires a two-story vlan table, three three switches function assistance is needed to modify the second floor vlan table, while the three-routing table of router processing and two-story vlan processing table are independent.
3 bridges
The backplane bridge port isolation, each port is an independent channel that is to say, no longer repeater / hub that is shared nature of the backsheet. Finally use a separate port to do the smart features.
Layer 2 bridge table to maintain mac and mac correspondence between ports, which can be (unknown unicast go broadcast process) by the beginning of the second floor of broadcast packets to learn. Thus, the bridge can know the relationship between the mac and each port which all nodes.
Thus, when a bridge port frame received packets, it can extract and observe the relationship src_mac, dst_mac, rcv_port: if src_mac and dst_mac belong rcv_port under forward the frame to another port will not, play a collision domain isolation. On the contrary, it is forwarded to another port, reach another (sub) network.
Mac this table, for the uplink from the port determines whether the same effect (i.e., the same network), to find out the port from downstream effects (due to the two ports on the bridge is simplified), and the original is a switch forwarding process.
Seen from the bridge begins, with a layer of the steps, not as a repeater / concentrator as it is because it can not only identify mac for all (other) port forwarding the simple treatment. However, it still can not separate broadcast domains (and this is not configured vlan switch is the same as the original).
Router
Router (Router) is connected to the Internet each local area network device, it will automatically selected and set route according to the situation of the channel, the best path, the transmission signal according to the predecessor sequence. General router has two parts, WAN and LAN, WAN is used to dial-up, is to make the route a section of its own access to the Internet, LAN is used to exchange data within a local area network, external network cable plugged into the WAN port, through our computer network cable LAN port, wireless router wireless LAN are generally part of, it is generally called WLAN. Router built-in DHCP server, you can use the computer automatically assigns IP routing, so they will be able to plug in directly online
