Let‘s start by clearly defining what a network bridge is. A bridge is a Layer 2 device that connects multiple local area networks (LANs) allowing them communicate as one larger LAN. Bridges forward data frames based on MAC addresses rather than IP information.
In other words, bridges act like a literal bridge between different networks – they form a pathway for devices to talk across areas that would otherwise be isolated islands. But there are some nuances so read on to learn more!
Why Do We Need LAN Bridges?
LAN bridges help solve a common networking challenge – how to link separate physical zones like floors in an office building into one communication realm.
Running long cabling runs between locations gets impractical. Plus multiple distinct LANs allow better organization and access control.
Bridging them retains those advantages while removing barriers to connectivity across subnets.
For you, this means your WiFi can still span across say both buildings on a corporate campus because of the bridging infrastructure underneath that seamlessly connects everything.
A Quick History of Bridging Networks
- Early bus-based office LANs in the 1970s faced distance limits for running shared coaxial cables
- Multi-port bridges enabled extending these networks across longer reaches
- Advancements in switching and microelectronics lead to dedicated bridge hardware in the 80s
- Standardization of Ethernet and TCP/IP opened use-cases like campus backbones
- Today it‘s common for equipment like wireless access points to have bridging capabilities
So in summary, a long evolutionary march to the ubiquitous bridged networks powering our connected world!
What Are The Main Types of Network Bridges?
There are three primary bridge architectures, each with their own pros and cons:
Transparent Bridge
- Forward data based on destination MAC address
- Learn addresses by listening to network traffic
- Simplest plug-and-play option
- Supported widely on multiport devices like switches
Translational Bridge
- Joins dissimilar network protocols by converting frame formats
- Allows interoperation e.g. Ethernet to Token Ring
- Adds complexity so niche usage
Source Routing Bridge
- Depend on source computer to define route path through bridge
- Declining relevance as transparent proved superior
| Type | Key Characteristic | Complexity | Use Cases |
|---|---|---|---|
| Transparent | MAC address forwarding | Low | General purpose LAN connectivity |
| Translational | Converts protocols | High | Legacy system integration |
| Source Routing | Pre-defined path | Medium | Early bridged networks |
Now you know the most common options available and can select the right one for your environment!
How Do Bridges Actually Work?
It‘s worth taking a quick look under the hood at the key mechanisms that allow a bridge to forward data between interfaces:
1. Learning – By listening to frames on its ports, a bridge learns which MAC addresses are reachable through each interface. This populates the MAC address table.
2. Filtering – Using the table, bridges only forward relevant frames out the destination port. Other segments are sheltered reducing congestion.
3. Forwarding – The bridge finally transmits the frame onto the target LAN if allowed by the filtering rules.
This sequence allows seamless communication across the bridged network backbone!
What Are The Benefits of Using LAN Bridges?
Deploying bridges between your subnetworks comes with several advantages:
Cost Savings – Connecting LANs via a bridge is far cheaper than buying router hardware and configuring routing protocols.
Performance – Bridges split collision domains allowing network expansion without congestion impacting speeds.
Flexibility – Bridging is transparent to end devices and operating systems. It works independently of higher level protocols.
Control – Bridges give administrators the ability to connect while retaining separation of traffic domains.
Reliability – Spanning tree protocols let bridges provide redundancy while preventing forwarding loops.
For most networking use cases, LAN bridges strike an ideal balance of simplicity, speed and modular architectural design.
Potential Drawbacks and Challenges
The main downsides to watch out for when relying on bridges in your environment are:
Latency – Every hop across a bridge introduces a tiny bit of forwarding delay which can add up.
Fragility – A single bridge failure can split your network so plan redundancy carefully.
Traffic leaks – Bridges exchange broadcasts so segments hear each other‘s chatter unless configured carefully.
Limited tools – Troubleshooting bridged connections often proves more difficult than routing paths.
Scalability limits – Extensive bridging can strain MAC address tables so know equipment memory size.
Real World Examples of Network Bridges
While bridges may sound like an abstract concept, they deliver vital utility across many different networks:
Campus Networks – Join building LANs over fiber or wireless links to enable unified school/corporate intranets.
SDN Overlays – Virtual extensible LAN standards like VxLAN use logical bridges between data centers.
Metro Backbones – Cities deploy high-capacity microwave and millimeter wave bridges linking critical sites.
Backhaul Aggregation – Wireless ISPs bridge long distances from their core using specialized directional equipment.
From the small to the mammoth scales – bridges help pull localized zones into larger networks!
Final Thoughts
I hope this lengthy yet plain explanation gives you confidence in understanding the importance of bridging in all types of computer networks!
They are simple constructs that offer tremendous reach and flexibility. Learning about bridges hopefully demystifies one building block empowering our amazing connected age.
Let me know if you have any other questions on this or other fundamental networking concepts!
