AS (Autonomous System)
The internet is an network of networks and each individual network in this collection of networks is called an Autonomous System
AS is a group of connected routers that are run and managed by a single network operator (Single Organization)
The AS can be anyone a University, Organization or even a Level 3 ISP
IGP (Internet Gateway Protocol)
IGP is used for routing inside an single AS (Organization)
OSPF (Open Short Path First)
RIP & RIPv2 (Routing Information Protocol)
EGP (External Gateway Protocol)
Used to route data between different AS (Organization)