Bridging

Bridging, which is based on the OSI network model of the link layer address, the network data packet forwarding process. Is working in OSI second layer. General switch, bridge has the bridge effect. It switches, itself has a port and MAC mapping table, through these, separate collision domains. Simply through the bridge can take two different physical LAN connection, is a kind of link layer in LAN interconnection storage forwarding equipment. Bridge from a local area network to receive MAC frame, unpacking, check, check, according to another local format reassembled, sent to its physical layer.

Brief introduction

The bridge was used in two or more segments of the network or subnet communication path is provided between the interconnection equipment.

These network or subnet with the same address and network topological structure. A workstation on a network can use the bridge to other online station broadcast message, so the bridge is connected network segment to the two port (or port ) equipment. In addition, the bridge also can be the business busy network is divided into two sections, each section to reduce communication amount in order to improve the performance of. It can filter the network broadcast information, allowing only the necessary communication information through the bridge to other network.

Installation

Expanding the network distance and number of nodes.

Reduce connections caused by excessive communication bottleneck.

To link different networks, such as Ethernet, token ring network. And in the transmission of packets between them. The premise is that they use the same network protocol.

The bridge may be a stand-alone device, or by mounting one or more cards in the server to establish, the premise is the server operating system support bridge. The bridge connected to each LAN segment has a specific network number. For example, the network is similar to the street name, room number, similar to the workstation. The bridge connected between the data transfer in network. Novell NetWare, Banyan VINES and Microsoft company's network has a server bridging function. If the bridging function enables the server to paralyzed, requires external bridges, external bridge by Cisco, 3COM, Cabletron supplier manufacturing.

The bridge has a filter function, the function is realized by reading the Ethernet or token ring frame address to determine the packet which belongs to a LAN network. However, the bridge can not access the network layer protocol information, so it cannot provide the optimal path selection. The router can be programmed to (or study ) in a special path for routing packets to reduce or avoid communication congestion cost. And multiple protocol router can be used for process with multiple communication protocol for network communication. As the network grew, bridging the number increases, may appear circular loop or invalid path. In bridged network to avoid the loop will be discussed in a later. The bridge is lack of congestion management, unable to determine the optimum data path. When many workstations transmitting will cause congestion. In a bridged network, flow control by an end system. Bridge in to compensate for the congestion problem and send additional packets, may actually makes the problem expanded. These issues will be addressed in this section" spanning tree algorithm " in the discussion.