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3.1 ISPs & Connectivity

Internet Service Providers (ISPs) are the on-ramp to the Internet. Tier-1, Tier-2, and last-mile providers form a hierarchy of peering and transit relationships.

3.1 ISPs and Connectivity

ISP hierarchy

Tier 1 backbone Tier 2 regional / national Tier 3 last-mile (you) Figure 3.1 - Each higher tier supplies transit to the layer below; peering is between Tier 1s.

Connection types

TypeTypical speedUse
DSLup to ~100 MbpsLegacy SMEs
Cable100-500 MbpsResidential common
Fibre (FTTH)GigabitModern home + small office
Wireless5G FWA, P2PRural, bridge link
Leased lineSymmetricHigh SLA; expensive
MPLSSymmetricPrivate WAN over multiple providers
SD-WANMixedOrchestrated mix of the above

Philippine context

ISPNotes
PLDTLargest fixed-line / fibre operator
GlobeMobile + fibre
ConvergeFibre-led; aggressive expansion
DITOThird mobile carrier
SkyCable-led incumbent

Internet Exchange Points (PHIX, PHOpenIX) reduce inter-ISP latency. RA 7925 regulates the sector.

Worked example - small bank dual-homed branch

ItemConfiguration
Branch2x fibre to two different last-mile ISPs
HQMPLS + Internet over SD-WAN, BGP-steered
FailoverSub-30s on primary path loss
SLA target99.9 % branch reachability
Mentor’s tip: Tier 1, 2, 3 - the hierarchy decides your real SLA. Dual-homing matters more than the brochure number. Document the route from app to user; the longest hop is usually where outages bite.

Discussion

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