ISPs and Internet Infrastructure
Learn about Internet Service Providers, network hierarchies, and how internet infrastructure works.
What are ISPs?
Internet Service Providers (ISPs) connect homes, businesses, and data centers to the wider internet. They run the physical networks, assign IP addresses, and arrange the relationships that keep traffic flowing. If you’re new to addressing basics, start with our IP primer.
ISP core functions
- • Internet access for end users and organizations
- • IP address allocation and DHCP management
- • Network build‑out and maintenance
- • Traffic routing within and between networks
- • Support, monitoring, and incident response
Types of ISPs
Different providers focus on different segments:
Consumer providers
- • Residential broadband
- • Mobile/cellular data
- • Satellite access
- • Community/municipal networks
Business & wholesale
- • Enterprise access and MPLS
- • Data center connectivity
- • Cloud and managed services
- • IP transit to other networks
ISP Hierarchy and Tiers
The internet’s routing system has a loose hierarchy:
Tier 1 — Global backbone
Own global backbone capacity; no upstreams; peer with other Tier 1s
Tier 2 — Regional networks
Mix of settlement‑free peering and paid transit
Tier 3 — Access providers
Buy transit; connect last‑mile customers
IP Address Management
Where addresses come from and how they’re assigned. For address formats and versions, see IPv4 vs IPv6.
Allocation flow
RIRs (ARIN, RIPE, APNIC)
Allocate large blocks to ISPs when justified by need
ISP planning
Split blocks into regional pools and service‑specific subnets
Customer assignment
DHCP for residential; static /29 or larger for business
Operations
Reclaim, resize, and migrate pools as demand shifts
Common challenges
- IPv4 scarcity: conservation, CGNAT, pushing IPv6
- Geographic demand: balancing pools across cities and POPs
- Scale: automation for millions of leases and devices
Network Infrastructure
The layers that move your packets from A to B:
Core
High‑capacity backbone between major cities and POPs
Distribution
Regional aggregation that feeds access networks
Access
Last‑mile connectivity to homes and offices
Facilities
Data centers and central offices that host network gear
Peering and Transit
How networks exchange traffic:
Peering
Settlement‑free exchange between networks of similar size
- Lower latency, fewer middlemen
- Cost control for both sides
- Usually happens at IXPs
Transit
Paid upstream connectivity to reach the full internet
- Smaller ISPs buy from larger ones
- Used for reach and redundancy
- Priced by capacity and commits
Global Internet Connectivity
Traffic crosses oceans and continents via a mix of systems:
Infrastructure
CDNs and caching
- Edge placement: content cached inside or near ISP networks
- Direct peering: fewer hops to popular services
- Performance: lower latency and less backbone congestion
ISP Business Models
ISPs mix and match revenue streams:
Residential broadband
Pricing, SLAs, and service bundles vary by segment and geography.
Enterprise services
Pricing, SLAs, and service bundles vary by segment and geography.
Wholesale/transit
Pricing, SLAs, and service bundles vary by segment and geography.
Mobile & wireless
Pricing, SLAs, and service bundles vary by segment and geography.
Future Challenges
Demand keeps climbing
- 4K/8K video
- Remote work
- IoT growth
IPv6 transition
- Dual‑stack ops
- Training & tooling
- Legacy gear
Security pressure
- DDoS scale
- Botnets
- Critical infrastructure risk
Regulation & policy
- Privacy laws
- Net neutrality
- Data localization
Key Takeaways
- ISPs connect users to the internet and route traffic across networks.
- Peering and transit relationships shape performance and cost.
- IPv6 adoption and security resilience are long‑running priorities.