When building computer networks, one of the most important early decisions is selecting the network topology. This refers to how the cables, nodes, links and other physical components connect together to enable devices to communicate.
The topology lays the foundation for how well the network will perform and scale. Making smart choices helps maximize key attributes:
- Speed and overall throughput
- Reliability and resilience to outages
- Security
- Ability to add capacity and new devices easily
- Cost efficiency
This guide will explain the 7 essential types of network topology clearly with real-world examples. Grasping these core concepts is key to designing, managing and troubleshooting any networked environment from home WiFi to global enterprise infrastructure.
Point-to-Point Topology
A point-to-point topology represents the simplest possible network connection – just two endpoints communicating directly without any other intervening devices.
Simple Point-to-Point Topology. Image source: ResearchGate
This is the equivalent of two people having a conversation versus trying to talk across a crowded room. No other parties get involved in sending or receiving messages across the link.
Point-to-point connections work over all sorts of networking technology:
- Fiber Optic Cable – Very high speed laser-based connections between cities.
- Microwave – Long range wireless links over tens of kilometers.
- Ethernet Cable – Direct network cables between devices in a building.
What Role Does Point-to-Point Play?
We use point-to-point links as building blocks to connect more complex network structures. A bunch of point-to-point wireless links can bridge between wired network zones for example.
They also provide dedicated connectivity between fixed locations:
- Businesses paying for premium dedicated internet lines to guarantee capacity and uptime.
- Long distance network backbones carrying lots of data for ISPs and carriers.
- Rural internet access via microwave links to properties lacking fiber or cable connections.
The simplest interconnection between two endpoints offers unrivaled speed thanks to no intermediary components. We utilize point-to-point for pure throughput above other priorities.
Pros and Cons of Point-to-Point Links
| Pros | Cons |
|---|---|
| Extremely fast data transfer speeds | No inherent redundancy – single link failure knocks out connection |
| Conceptually simple to understand | Only directly connects two endpoints |
| Easy to configure security protocols | Constrained flexibility for complex network requirements |
| Compact – requires little physical infrastructure | Line of sight constraints on wireless links |
Point-to-point fits simple networking needs or providing backbone capacity between parts of more intricate networks.
Its role is transporting data quickly and reliably between two fixed endpoints rather than anything more complex. All data flows strictly down that single dedicated pipe.
Star Topology
Star networks centralize connectivity through a single focal device that all other endpoints plug into. This central controller manages and directs traffic flows.
Star Topology with Central Switch. Image source: imperva.com
In home networks, the wireless router performs this hub role allowing multiple Wi-Fi devices to interconnect. In corporate networks it is a central switch that user computers plug into.
Star Networks in Action
Star networks are ubiquitous thanks to the Ethernet protocol which powers most modern wired local area networking. The alternative is token based networking which never gained as much traction.
When you see an office floor where each desk has a cable feeding back to floor mounted ports, that cables are likely terminating at a network switch to form a physical star layout.
The switch acts as traffic cop – data comes in across one port and can exit out any others depending on internal address tables. This sets up dedicated communications channels between individual endpoint pairs.
In wireless contexts such as WiFi, it is the wireless access point device that performs the hub role. It bridges between the wired network infrastructure and wireless devices connecting to it.
Expandability and Resilience Properties
A nice feature of star networks is the ability to incrementally add new connections without disturbing existing nodes. Just plugging extra devices into ports on the central switch integrates them into the network with all capabilities available immediately.
Similarly, failures of connections affect only that endpoint node – the rest of the network continues functioning. This localization of issues contrasts with bus or ring structures where an individual failure can completely bring the whole network down.
The flip side is that the central hub concentrates both connectivity and the potential for failure in one spot. If the hub device itself crashes or needs maintenance taken offline, connectivity across every attached client also fails simultaneously.
Pros and Cons of Star Topologies
| Pros | Cons |
|---|---|
| Adding/relocation endpoints easy by changing switch ports | Total network outage if central hub device fails |
| Outage of one node localizes issue | Increased cabling to route everything via center |
| Centralized control and coordination | Hub choice constrains overall performance |
| Wide adoption via Ethernet protocol | Security challenges with central route point |
Star topology does centralize control and failure risk. However, the extensive real-world adoption using Ethernet LAN switching confirms this flexibility and local failure containment trumps the downsides for many common scenarios.
Bus Topology
Bus networks rely on a common backbone cable which all networked devices connect into to communicate. Nodes take turns transmitting on the shared medium according to rules avoiding collisions.
Shared Backbone Bus Topology. Image source: Javatpoint.
This trunk cable essentially acts as a linear messaging bus that data rides up and down. All network participants can receive traffic, with devices targeting communication at intended recipients.
Contrasting Rings, Stars and Trees
Rings, stars and trees all utilize a central coordinating device or specific restricted pathways that manage flow. Bus networks route all data openly down a common pipe instead.
It moves away from centralized control towards a peer-based model. Participants utilize Carrier Sense Multiple Access (CSMA) disciplines to take turns sharing the medium.
This standardized protocol listens if any other data flowing before transmitting. It waits for clear channels avoiding anything transmitting simultaneously, resulting in collisions corrupting both streams.
Early Ethernet relied on coaxial cable based bus networks prior to moving the switched star centric distribution we predominantly use today in local area deployment. It is simpler and cheaper to connect devices into open bus style topologies in small areas.
Strengths and Weaknesses of Bus Networks
Multipoint bus topologies do come with limitations for more extensive connectivity:
- Aggregate performance caps out at bus cable limits shared across all devices
- Expanding networks by adding more nodes inevitably slows throughput
- Fault isolation tricky with all devices accessing same cable
- Failure of the bus cable itself halts everything
| Pros | Cons |
|---|---|
| Cheap and easy for small peer groups | Limited aggregate network capacity |
| Add new nodes anywhere on bus | Difficult fault isolation with single shared segment |
| Fair bandwidth access arbitration | No redundancy or failover if bus fails totally |
| No complexity around routing logic | Security exposure with traffic visible to all participants |
The open simplicity of bus connectivity makes it less suitable for mission critical systems. However it has usefulness for cheaper consumer or IoT style networking applications.
Mesh Topology
Mesh networks provide multiply redundant interlinks between peer nodes. This ensures connectivity survives individual link failures via remaining alternate paths.
Example of a Mesh Topology. Image Credit: incapsula.com
Why Use Meshing?
Real world networks implement meshing in parts requiring high resilience against interruptions, rather than heavily meshing everything. That rapidly becomes infeasible across costs, complexity and cable plant for large environments.
We utilized meshing where downtime has severe consequences – banks, hospitals, infrastructure. The redundant interconnects provide failover to sustain uptime through inevitable individual component failures.
These rich interconnect relationships between devices also improve aggregate bandwidth and throughput capacity when compared to simpler configurations.
For endpoint devices like laptop users, meshing assists mobility. Your WiFi smartphone can roam between different wireless access points which have wireless backhaul interlinks coordinating connectivity and access.
Contrasting Star and Tree Structures
Both stars and trees heavily concentrate connectivity through singular central funnel points. These clearly become vulnerabilties regarding uptime and throughput ceilings in large networks.
Losing the core router in a 5000 person company cuts out the entire organization instantly. Their work stops until connectivity resumes.
However, meshing shifts away from this by mandating multiple independent pathways for data. If any one node fails or needs maintenance, traffic reroutes sustaining availability and performance during remediations.
This clearly matters when money and reputations absolutely rely on systems running continuously without fail. Banks promise "five nines" uptime meaning 99.999 percent guaranteed availability in service level agreements. This works out to under 6 minutes of total downtime annually!
Evaluating Mesh Tradeoffs
Nothing is 100 percent perfect however, so mesh networks also come with implementation and operating challenges. Significant cabling plant costs arise requiring each device connects multiply upstream and downstream to peers for full redundancy. It is expensive.
Maintenance processes contend with complex interdependencies when locating faults. Traffic traversing devices takes less predictable pathways with constant re-routing from incidents. Security policies are very challenging to sustain consistently.
Overall however, many organizations determine this overhead merits the exceptional resilience and capacity meshed designs provide for vital environments.
| Pros | Cons |
|---|---|
| Inbuilt redundancy sustains uptime | N links demand N(N-1)/2 connectors (cost) |
| Throughput improves via multiple routes | Complex fault isolation with decentralized routing |
| Local failures stay local via rerouting | Management overhead around security and traffic optimization |
| Conceptually simple | Required culture change from hierarchical control norms |
Tree Topology
Trees model hierarchy. A root node at the top provides backbone connectivity out to many child sub-nodes layered down multiple generations terminating eventually at edge endpoints.
Conceptual Tree Network Topology. Image Credit: ørjan.io
A core root node provides connectivity out to regional distribution hubs across the first layer of child sub-nodes.
These hubs similarly link the next generation of local sub-networks onward down the tree out towards the edge endpoints eventually.
Parent to child data flows bidirectionally across the rigid pathways although bulk traffic tends to descend from top towards endpoint leaves at the lower layers.
Real World Tree Structures
The tiered nature of tree networks mirrors both human organizational structures as well as the physical architecture of network hardware connectivity:
- Corporate hierarchies cascade from central headquarters outwards to remote regional offices.
- National telco transmission data enters regional centers then reaches metro zones extending ultimately to customers.
- High capacity fiber or Ethernet backbones split into smaller child branches via switches.
ThisSegmentation helps cater to location specific needs at child sub-layers while consolidating higher performance routing over quicker backbone rings or mesh trunks towards the tree root layers.
Hierarchical trees ultimately simplify complex flat unstructured connectivity via these known pathways. Troubleshooting stays manageable following branches rather than chasing looping mesh links.
Operations can scale systems following well organized subdivision principles across clear demarcations in the hierarchy.
Tradeoffs Around Centralization
The rigid structure does risk single points of failure closer to the root however. Entire sub-trees disappear downstream if regional distribution hubs fail. Redundant mechanisms help mitigate this.
Similarly, capacity bottlenecks are more likely further up the tree as increasing aggregate child node bandwidth concentrates into fewer routes back upstream.
Overall utilizing hierarchy brings simplification that boosts manageability for large deployments which outweigh disadvantages through layered engineering.
| Pros | Cons |
|---|---|
| Structured cabling and troubleshooting | Bandwidth bottlenecks up tree toward root |
| Match to administrative org structures | Loss of regional hub downs entire sub-tree |
| Central backbone favors fast meshing | More rigidity adapting to change |
| Divide and conquer scale out branching | Arbitrary mapping of functionality onto hierarchy |
Hybrid Topology
Hybrid networks combine multiple topological structures across a multilayer design attempting to balance strengths and weaknesses of each.
Conceptual Hybrid Network Topology. Image Credit: ResearchGate
Typically, the access layer network favors flexibility and cost efficiency connecting end users so features bus or star patterns.
Distribution into the metro backbone strikes a balance between performance, cost and manageability. This middle layer utilizes tree structures frequently.
The core long haul transmission backbone then leverages high speed heavily meshed or ring patterns for maximum throughput and redundancy.
In large environments, automating adaption and failover across multilayer protocols presents challenges. Network management systems tackle this via policies that reconfigure routing dynamically based on load and known status.
Administrators define hierarchy between the layered schemes as connectivity descends from the resilient mesh backbone through structured trees reaching large numbers of low cost switches at the edge.
Real World Hybrid Infrastructure
The global internet itself stands as the largest functioning hybrid system:
Core Backbone – High speed router interconnected via vast meshed links often running in parallel for redundancy to protect against line cuts.
Regional Distribution – Large internet exchanges implementing tree structures for centers to branch traffic out into metro regions.
Local ISP Access – ISPs combine flexible bus and star centric last mile infrastructure to reach customers.
Well engineered hybrids allow this incredibly intricate global infrastructure to cost effectively sustain near 100 percent uptime across inevitable edge failures through flexibility and redundancy higher up the hierarchy.
Without hybrid structures, outages would likely become far more extensive through interconnected knock on effects.
| Pros | Cons |
|---|---|
| Optimally adapts topology traits to network functions | Design and implementation complexity |
| Leverages strengths of multiple schemes | Potential layer to layer compatibility hurdles |
| Customizable implementations | Tendency towards fragmentation |
| Automation assists managing scale/complexity | Multilayer debugging challenges |
Conclusion
This guide covered the 7 essential types of network topology seen across computing and telecommunication infrastructures.
Engineers utilize these fundamental patterns as building blocks while designing solutions optimized for speed, resilience flexibility and operational costs.
Selecting appropriate topological organization schemes and thoughtfully combining advantages across layers with hybrid designs allows networks to efficiently fulfill crucial functionality even at global scale.
Understanding these key concepts will assist you in navigating discussions around constructing resilient cost effective networking.
