If I understand Interior gateway protocols (RIP,OSPF,EIGRP) are used within companies network to route packets between different subnets.
BGP is commonly used by ISP : I may say it is used to route (IGPs) between different Autonomous systems on the internet...I could be wrong...please correct me
BGP is also used by companies, in case they have 2 primary connections to 2 different ISPs.
but in this case, I am not sure what the company will route through BGP...considering if the company has just one connection to a single ISP, then all that the company is doing is connecting to internet....Please correct me
Frame Relay allows company sites to be connected just like they are one site... if each site is using IGPs then ...I may say IGPs (Layer3) are tunnelled through FR(Layer2)..please correct me on this
MPLS is similar to FR ...but I wonder if it does tunnel each company site IGPs(Layer3) through MPLS.
MPLS works at layer 2.5.
Any clarification will be appreciated.