After reading the article about synchronization issues in BGP, I realised there's one thing I don't get.
RTC in AS300 sends updates about 188.8.131.52. RTA and RTB run iBGP, so RTB gets the update and is able to reach 184.108.40.206 via next hop 220.127.116.11. Remember that the next hop is carried via iBGP. In order to reach the next hop, RTB must send the traffic to RTE. Assume that RTA has not redistributed network 18.104.22.168 into IGP. At this point, RTE has no idea that 22.214.171.124 even exists. If RTB starts to advertise to AS400 that RTB can reach 126.96.36.199, traffic that comes from RTD to RTB with destination 188.8.131.52 flows in and drops at RTE.
Isn't it the key reason of why people use BGP - the fact that IGP protocols such as OSFP don't need to know about thousands of different networks from other ASes, because BGP routers handles it for them?
The article states that RTE, which is an IGP router, should also know about
184.108.40.206 advertised to RTA over BGP by RTC. If RTC advertised other prefixes as well, that would mean RTE (IGP router!!) would have to learn them as well so that RTB can communicate with AS300.