Networking - Network Component - Bridges

A bridge is a network device that operates at the Data Link Layer (Layer 2) of the OSI (Open Systems Interconnection) model. Its primary function is to connect two or more network segments or LANs (Local Area Networks) and selectively forward data packets between them based on MAC addresses. Bridges are commonly used to divide a large network into smaller segments to improve network performance and efficiency.

Here are some key points about bridges:

  • Function: A bridge connects two or more network segments that use the same network protocol and forwards data packets between them. It examines the MAC addresses of incoming data packets and selectively forwards them only to the appropriate segment where the destination device is located.
  • MAC Address Learning: One of the important functions of a bridge is MAC address learning. When a data packet arrives at a bridge, it examines the source MAC address and associates it with the port through which the packet arrived. The bridge builds a MAC address table, which helps in making forwarding decisions in the future.
  • Filtering and Forwarding: Bridges use the MAC address table to determine the appropriate port to which a data packet should be forwarded. If the destination MAC address is in the same network segment as the source device, the bridge discards the packet. Otherwise, it forwards the packet to the corresponding segment.
  • Segmentation and Collision Domain Isolation: Bridges can help divide a large network into smaller segments. Each segment operates as an independent collision domain, reducing the chances of collisions and improving network performance. By isolating collisions to individual segments, bridges enhance network efficiency.

Types of Bridges:

  • Transparent Bridge: A transparent bridge is the most common type of bridge. It operates at the MAC sublayer of the Data Link Layer and is transparent to network devices. It forwards data packets based on MAC addresses without modifying the content of the packets.
  • Source Route Bridge: Source Route Bridges (SRB) use source routing protocols to determine the complete path for data packets. The source device includes the entire route in the packet, and the bridge simply forwards the packet along the specified path.

Advantages of Bridges:

  • Improved Network Performance: By dividing a large network into smaller segments, bridges reduce network congestion and improve overall network performance.
  • Collision Isolation: Bridges isolate collisions within individual network segments, reducing collision domain size and minimizing the impact of collisions on the entire network.
  • Scalability: Bridges provide a scalable solution for network expansion. Additional bridges can be added to connect more network segments as the network grows.

Disadvantages of Bridges:

  • Limited Broadcast Domain: Each bridge creates a separate broadcast domain, which can increase the volume of broadcast traffic and potentially impact network performance.
  • Limited Interconnectivity: Bridges can only connect network segments that use the same network protocol. They cannot connect segments that use different protocols without additional protocol conversion mechanisms.