Routing Information Protocol(RIP)and Open Shortest Path First(OSPF)routing protocols are most widely used IGP.The purpose of this paperis to illustrate something as follows:(1)Description of RIP,Description of OSPF.(2)Comparison between RIP(DV)and OSPF(LS)routing protocols.(3)How reconvergence times can be improved.(4)Explanations of the consequences of least-cost routing in a single-service inter-network.(5)How source-routing mechanisms can be used to improve overall network efficiency.