Network Devices Explained: Bridges, Switches, and Routers

Bridges and Switches: Essential Network Elements

Bridges (Puentes) and Switches are network elements that possess control capabilities, storing and forwarding the frames they receive through their ports based on their content.

They are primarily used to interconnect similar or different Local Area Networks (LANs). A bridge isolates traffic between network segments.

For instance, if an Ethernet network needs to exceed 2.5 km in length, a bridge can be installed to segment the network. By assigning each segment a length not exceeding 2.5 km, a total network length of up to 5 km can be achieved.

OSI Layer 2 Operation

Bridges operate at OSI Layer 2 (Data Link Layer). Their basic unit of operation is the frame.

Phases in Frame Pathing Between Segments:

1. The received frame is first stored in memory.
2. A CRC (Cyclic Redundancy Check) is performed to prevent the forwarding of erroneous frames.
3. Some bridges are capable of directing the frame toward the target segment.
4. Finally, the bridge forwards the frame if the destination is reachable through the target segment.

The Network Switch

A switch is a device that also functions at OSI Layer 2. While it resembles a bridge in operation, several characteristics distinguish it:

• The switch is always local.
• It connects network segments instead of entire networks.
• It is generally faster than a bridge.
• It can share the network bandwidth appropriately across each segment.
• Switches are often stackable.
• The total bandwidth of the switch exceeds the bandwidth available at each individual port.
• Some switches can connect network segments of different types.
• Typical protocols are managed through network management systems.

The Router: Layer 3 Interconnection

A Router is a hardware device or software component that can be configured to route packets between its different ports using logical addresses. Routers interconnect LANs and operate at OSI Layer 3 (Network Layer).

Router operation is fundamentally determined by the specific network protocol being used. This Layer 3 focus means its performance involves less analysis of individual data packages compared to Layer 2 devices. A router isolates logical networks, dividing traffic between segments and managing broadcast traffic effectively.

It is crucial to consider the network protocol that the router must handle. A router configured for TCP/IP routing is highly versatile, though its ability to route other protocols depends on its configuration.

Routing Algorithms

Static Routing Algorithms

In static routing, the routing table is manually programmed by the network administrator. These algorithms lack the capacity to automatically learn the network topology itself.

Dynamic or Adaptive Routing Algorithms

These algorithms are capable of learning the network topology autonomously, making them much more flexible than static methods, although they may sometimes result in lower throughput (yields). Common protocols used include RIP, RIPv2, and SPF (Shortest Path First).