Bridge
Bridge is like a clever repeater. Repeaters receive signals from a network cable, amplify them, and send them to the next cable. In comparison, bridges are more sensitive to the information uploaded from the level. A bridge is a technology that forwards frames. According to MAC partition blocks, collisions can be isolated. Bridges connect multiple segments of the network at the data link layer.
Bridges, also known as bridges, are a type of storage/forwarding device that connects two LANs. They can split a large LAN into multiple network segments, or interconnect two or more LANs into a single logical LAN, enabling LANs. All users have access to the server.
principle
Bridges connect two similar networks and manage the flow of network data. It works at the data link layer, not only can expand the distance or range of the network, but also can improve the performance, reliability and security of the network. After network 1 and network 2 are connected via a bridge, the bridge receives the data packet sent by network 1 and checks the address in the data packet. If the address belongs to network 1, it discards it. In contrast, if it is the address of network 2, it will Continue to send to the network 2. This can use the bridge to isolate information, divide the same network number into multiple network segments (belonging to the same network number), isolate the security network segment, and prevent users in other network segments from illegally accessing. Because of the segmentation of the network, each network segment is relatively independent (belongs to the same network number), and the failure of one network segment will not affect the operation of another network segment.
A bridge can be a dedicated hardware device or it can be implemented by computer-installed bridge software. In this case, multiple network adapters (network cards) are installed on the computer.
The function of the bridge is similar to the repeater in extending the span of the network, but it can provide the intelligent connection service, that is, according to which network segment the end address of the frame is for forwarding and filtering. The network bridge's understanding of the network segment where the site is located is achieved through “self-learningâ€, with transparent bridges, transition bridges, encapsulation bridges, and source routing bridges.
When using a bridge to connect two LANs, the bridge first checks its destination address for the MAC frame from segment 1. If the frame is sent to a station on segment 1, the bridge will not forward the frame to segment 2 and filter it out; if the frame is sent to a station on segment 2, the bridge Then it is forwarded to network segment 2, which shows that if there is a pair of users on LAN1 and LAN2 communicating on this segment at the same time, it is obviously achievable. Because the bridge played a role in isolation. It can be seen that the bridge has the effect of increasing the network bandwidth under certain conditions.
The bridge's storage and forwarding functions have advantages and disadvantages compared to repeaters. The advantages are:
Using bridges for interconnection overcomes physical limitations, which means that the total number of data stations and network segments that make up a LAN can be easily expanded.
The bridge's inclusion of storage and forwarding capabilities makes it adaptable to connect two LANs using different MAC protocols, thus forming a mixed network environment where different LANs are mixed together.
The bridge's relay function only relies on the MAC frame's address and is therefore completely transparent to the higher layer protocol.
A bridge divides a large LAN into segments, which helps to improve reliability, availability, and security.
The main drawback of a bridge is that since the bridge receives and buffers the frame before it performs forwarding, it introduces more delay than the repeater. Because the bridge does not provide the flow control function, it may overload the traffic when it is relatively large, resulting in the loss of frames.
The advantages of bridges over shortcomings are the reasons for their widespread use.
A bridge works at the data link layer. Connecting two LANs and forwarding frames based on MAC addresses can be considered as a "lower router" (routers work at the network layer and forward based on network addresses such as IP addresses).
Remote bridges connect two remote LANs via a typically slower link (such as a telephone line), where performance is more important for a local bridge, and long-distance operation is better for remote bridges. important.
the difference
The comparative bridge of the bridge and the router does not understand the information of the high-level protocol in the forwarding frame, which makes it possible to handle the IP, IPX, and other protocols in the same manner at the same time. It also provides a network that will have no routing protocol (such as Net BEUI. ) Segmented features.
Because routers process data at the network layer, they are more likely to interconnect different data link layers, such as token ring segments and Ethernet segments. Bridges are usually harder to control than routers. Protocols such as IP have complex routing protocols that make it easy for network managers to manage routes; IP and other protocols also provide more information about how the network is segmented (even if its address provides such information). Bridges only work with MAC addresses and physical topologies. Therefore, bridges are generally suitable for small and simple networks.
Many organizations have multiple LANs and want to be able to connect them. The reason why a unit has multiple LANs is due to the following reasons:
First, many university departments or company departments have their own local area networks, primarily for connecting their own personal computers, workstations, and servers. Due to the different nature of the work of each department (or department), different LANs have been selected. These departments (or departments) need to communicate with each other sooner or later, and thus require bridges.
Second, a unit is more geographically dispersed and farther apart. Instead of installing a coaxial cable network at all locations, it may be better to establish a local area network at each location and connect it with a bridge and an infrared link. This may cause costs to be Lower.
Third, it may be necessary to divide a logically unitary LAN into multiple LANs to regulate the load. For example, multiple LANs connected by bridges are used. Each LAN has a set of workstations and has its own file server. Therefore, most of the communication is limited to a single LAN, which reduces the burden on the backbone network.
Fourth, in some cases, the individual LANs are no problem from the point of view of the load, but the physical distance between the machines that are furthest apart is too far apart (eg, more than 2.5 km as specified by 802.3). Even if the cable laying is not a problem, the network will still not work properly due to the long time delay. The only way is to segment the LAN and place bridges between the segments. By using bridges, you can increase the total physical distance of your work.
Fifth, reliability issues. In a single LAN, a flawed node constantly outputs useless traffic that can severely disrupt the operation of the LAN. Bridges can be located at key locations in a LAN, just like fire doors in buildings, to prevent the entire system from being damaged by a single node malfunction.
Sixth, bridges help ensure security. Most LAN interfaces have a promiscuous mode in which the computer receives all the frames, including those that are not addressed to it. If multiple bridges are set up in the network and carefully intercept important information without forwarding, then the network can be separated to prevent information from being stolen.
Bridge is like a clever repeater. Repeaters receive signals from a network cable, amplify them, and send them to the next cable. In comparison, bridges are more sensitive to the information uploaded from the level. A bridge is a technology that forwards frames. According to MAC partition blocks, collisions can be isolated. Bridges connect multiple segments of the network at the data link layer.
Bridges, also known as bridges, are a type of storage/forwarding device that connects two LANs. They can split a large LAN into multiple network segments, or interconnect two or more LANs into a single logical LAN, enabling LANs. All users have access to the server.
principle
Bridges connect two similar networks and manage the flow of network data. It works at the data link layer, not only can expand the distance or range of the network, but also can improve the performance, reliability and security of the network. After network 1 and network 2 are connected via a bridge, the bridge receives the data packet sent by network 1 and checks the address in the data packet. If the address belongs to network 1, it discards it. In contrast, if it is the address of network 2, it will Continue to send to the network 2. This can use the bridge to isolate information, divide the same network number into multiple network segments (belonging to the same network number), isolate the security network segment, and prevent users in other network segments from illegally accessing. Because of the segmentation of the network, each network segment is relatively independent (belongs to the same network number), and the failure of one network segment will not affect the operation of another network segment.
A bridge can be a dedicated hardware device or it can be implemented by computer-installed bridge software. In this case, multiple network adapters (network cards) are installed on the computer.
The function of the bridge is similar to the repeater in extending the span of the network, but it can provide the intelligent connection service, that is, according to which network segment the end address of the frame is for forwarding and filtering. The network bridge's understanding of the network segment where the site is located is achieved through “self-learningâ€, with transparent bridges, transition bridges, encapsulation bridges, and source routing bridges.
When using a bridge to connect two LANs, the bridge first checks its destination address for the MAC frame from segment 1. If the frame is sent to a station on segment 1, the bridge will not forward the frame to segment 2 and filter it out; if the frame is sent to a station on segment 2, the bridge Then it is forwarded to network segment 2, which shows that if there is a pair of users on LAN1 and LAN2 communicating on this segment at the same time, it is obviously achievable. Because the bridge played a role in isolation. It can be seen that the bridge has the effect of increasing the network bandwidth under certain conditions.
The bridge's storage and forwarding functions have advantages and disadvantages compared to repeaters. The advantages are:
Using bridges for interconnection overcomes physical limitations, which means that the total number of data stations and network segments that make up a LAN can be easily expanded.
The bridge's inclusion of storage and forwarding capabilities makes it adaptable to connect two LANs using different MAC protocols, thus forming a mixed network environment where different LANs are mixed together.
The bridge's relay function only relies on the MAC frame's address and is therefore completely transparent to the higher layer protocol.
A bridge divides a large LAN into segments, which helps to improve reliability, availability, and security.
The main drawback of a bridge is that since the bridge receives and buffers the frame before it performs forwarding, it introduces more delay than the repeater. Because the bridge does not provide the flow control function, it may overload the traffic when it is relatively large, resulting in the loss of frames.
The advantages of bridges over shortcomings are the reasons for their widespread use.
A bridge works at the data link layer. Connecting two LANs and forwarding frames based on MAC addresses can be considered as a "lower router" (routers work at the network layer and forward based on network addresses such as IP addresses).
Remote bridges connect two remote LANs via a typically slower link (such as a telephone line), where performance is more important for a local bridge, and long-distance operation is better for remote bridges. important.
the difference
The comparative bridge of the bridge and the router does not understand the information of the high-level protocol in the forwarding frame, which makes it possible to handle the IP, IPX, and other protocols in the same manner at the same time. It also provides a network that will have no routing protocol (such as Net BEUI. ) Segmented features.
Because routers process data at the network layer, they are more likely to interconnect different data link layers, such as token ring segments and Ethernet segments. Bridges are usually harder to control than routers. Protocols such as IP have complex routing protocols that make it easy for network managers to manage routes; IP and other protocols also provide more information about how the network is segmented (even if its address provides such information). Bridges only work with MAC addresses and physical topologies. Therefore, bridges are generally suitable for small and simple networks.
Many organizations have multiple LANs and want to be able to connect them. The reason why a unit has multiple LANs is due to the following reasons:
First, many university departments or company departments have their own local area networks, primarily for connecting their own personal computers, workstations, and servers. Due to the different nature of the work of each department (or department), different LANs have been selected. These departments (or departments) need to communicate with each other sooner or later, and thus require bridges.
Second, a unit is more geographically dispersed and farther apart. Instead of installing a coaxial cable network at all locations, it may be better to establish a local area network at each location and connect it with a bridge and an infrared link. This may cause costs to be Lower.
Third, it may be necessary to divide a logically unitary LAN into multiple LANs to regulate the load. For example, multiple LANs connected by bridges are used. Each LAN has a set of workstations and has its own file server. Therefore, most of the communication is limited to a single LAN, which reduces the burden on the backbone network.
Fourth, in some cases, the individual LANs are no problem from the point of view of the load, but the physical distance between the machines that are furthest apart is too far apart (eg, more than 2.5 km as specified by 802.3). Even if the cable laying is not a problem, the network will still not work properly due to the long time delay. The only way is to segment the LAN and place bridges between the segments. By using bridges, you can increase the total physical distance of your work.
Fifth, reliability issues. In a single LAN, a flawed node constantly outputs useless traffic that can severely disrupt the operation of the LAN. Bridges can be located at key locations in a LAN, just like fire doors in buildings, to prevent the entire system from being damaged by a single node malfunction.
Sixth, bridges help ensure security. Most LAN interfaces have a promiscuous mode in which the computer receives all the frames, including those that are not addressed to it. If multiple bridges are set up in the network and carefully intercept important information without forwarding, then the network can be separated to prevent information from being stolen.
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