A bridge in computer networking is a device that connects multiple subnetworks, forming a single, larger network. It allows devices on different network segments to communicate as if they were on the same network.
Understanding Network Bridges
A bridge operates at the data link layer of the OSI model. Unlike routers which operate at the network layer, bridges analyze MAC addresses to make forwarding decisions, which is how they differentiate from routers. Here's a deeper look:
Functionality
- Connecting Subnetworks: A bridge joins two or more LAN (Local Area Network) segments to expand the effective size of the network.
- Data Filtering: Bridges analyze the destination MAC addresses of data packets. They only forward packets to the specific network segment where the destination device resides. This process helps to reduce network traffic on unnecessary segments.
- Protocol Compatibility: Bridges work with the same network protocol. For example, an Ethernet bridge is used to connect Ethernet networks. As noted in our reference, "It provides interconnection with other computer networks that use the same protocol."
- MAC Address Learning: Bridges learn which MAC addresses are associated with each port. They use this information to determine where to send packets, instead of broadcasting them to every connected network segment. This is an essential operation, increasing network efficiency.
How Bridges Work
- Receiving Data: When a data packet arrives at a bridge, it first examines the destination MAC address.
- Looking Up Address: The bridge consults its internal table, which maps MAC addresses to specific ports or network segments.
- Forwarding: If the destination MAC address is known, the packet is forwarded only to the segment associated with that address. Otherwise, the data may be broadcast to every segment.
- Learning: Bridges continuously learn by adding new MAC address-to-port mappings to their tables when a new device sends traffic.
Practical Applications of Bridges
- Extending LANs: Bridges are commonly used to connect multiple LANs within the same organization. For instance, several separate offices can be interconnected, or a single organization can be expanded into different floors.
- Reducing Network Collisions: By segmenting a network, a bridge can limit the number of devices sharing the same physical media, thereby minimizing collisions and improving network performance.
- Connecting Different Network Topologies: Bridges can connect different network topologies, such as those using hubs or switches, and provide an enhanced and efficient network.
Advantages of Using Bridges
- Improved Performance: By reducing unnecessary traffic, bridges enhance overall network performance.
- Reduced Collisions: Segmenting the network reduces the frequency of data collisions.
- Increased Network Size: Enables you to expand LANs beyond their original physical limitations.
Example
Imagine an office with two separate Ethernet networks. You want to have all devices be able to access each other without routing the traffic through different networks. By adding a bridge between these two Ethernet networks, all devices can now communicate as one large LAN, and traffic between them will be handled by the bridge, which limits traffic to where it should go. As specified in our reference "Through a bridge, multiple LANs can be connected to form a larger and extended LAN."
Summary Table
| Feature | Description |
|---|---|
| Function | Connects subnetworks to create one extended LAN |
| OSI Layer | Data Link Layer (Layer 2) |
| Address Type | MAC Addresses |
| Purpose | Reduce network traffic, extend network size, minimize collisions |
| Protocol | Operates using same protocol, for example, Ethernet Bridge for Ethernet network |
