Network Technology Tutorials Notes (13)

<title>LAN Technology</title> LAN technology LAN networking equipment and methods--network transmission media

LAN networking equipment and methods--network equipment

In many cases, we want to extend the reach of Ethernet. The following is a discussion of extending Ethernet at the physical layer. This extension still seems to be a network at the network level.

Extend a local area network with a hub

If you use multiple hubs, you can override the network to a larger extent. For example, in a school there are three departments, each with a10Base T Ethernet, through a backbone of the hub to connect the various systems of Ethernet to become a larger ethernet. There are two advantages to doing so, one is to make the Ethernet of different faculties in this school communicate, and the second is to enlarge the coverage of Ethernet. However, the use of such a multi-level structure of the hub also brings some problems, before the three-connected Ethernet interconnection, each system Ethernet is a separate conflict domain, at any one time, in each conflict domain only one site can send data, each system throughput rate is 10Mbps, Therefore, the throughput rate of the three systems is 30Mbps. After three lines are connected through hubs, three collision domains become a collision domain, at which time the maximum throughput rate is still a system throughput of 10Mbps. When the two stations of a system are communicating, the data transmitted will be forwarded through all hubs, making it impossible for the other departments to communicate internally because a communication generates a conflict domain. The second is that if different systems use different Ethernet technologies, it is not possible to connect them through a hub.

Extending Ethernet over the data link layer

Network Bridge is used to extend Ethernet over the data link layer. The bridge is working at the data link layer, which forwards or filters the received frames based on the MAC address. When the bridge receives a frame, it does not forward the frame to all the interfaces, but insists on the destination MAC address of the frame before deciding which interface to forward the frame to, or the switch router. The simplest bridge has two interfaces, and a bridge with complex points can have multiple interfaces, and when two Ethernet is interconnected over a bridge, it becomes a larger Ethernet network.

A bridge is a forwarding frame, and using a network bridge can have several advantages. A filter traffic, increase throughput, network bridge work in the data link layer of the Mac sub-layer, you can make the Ethernet network segments become split open conflict domain, if the network bridge into a hub there is no division conflict domain function. If the throughput rate for each network segment is 10Mbps, the throughput rate for the entire network segment is 30Mbps. The second extends the Ethernet range and also increases the speed of workstations on Ethernet. Three improves reliability, but a network segment failure does not affect other network segments. Four interconnected different physical layers of different Mac sub-layers at different rates of Ethernet.
Bridge also has some shortcomings, such as the Network Bridge to store first, then check the publication, and then forward a process. The CSMA/CD algorithm is executed before forwarding, and the avoidance occurs when there is a conflict. The second in the Mac sub-layer does not have the traffic control function, when the network traffic is heavy when the storage space may not be enough to cause frame loss condition. The third bridge is only suitable for users not too much, traffic is not too large Ethernet, or sometimes because the message sent too much broadcast storm.

The bridge does not change the frame's original MAC address when forwarding the frame, the most commonly used bridge is the transparent bridge

The so-called transparent means that the sending site does not know the sending of the frame to pass through which bridge, the Ethernet site can not see the Network Bridge on Ethernet, while the bridge is also a Plug and Play device, that is, as long as the network bridge access to the local area network, not through manual configuration to publish, the bridge can work.
The forward table of the newly-connected bridge is empty, and it processes the received frames through the self-learning algorithm and forwards the frames according to the forwarding post.

Using the switch

An Ethernet switch is, in essence, a multi-interface bridge.

Network Technology Tutorials Notes (13)