1. OSPF Immediate Hello draft-kou-ospf-immediately-replying-hello-00.txt Zengjie Kou Xiaoyi Guo

2. Problems of normal OSPF Hello Each router sends Hello independently without responding to its neighbors The speed of neighbor discovery is slow Recovery of down link (e.g. interface flapping) is slow

3. Mechanisms of Immediate Hello When receiving a Hello, the OSPF router immediately replies Hello to its neighbors. After reaching “ Full ” state, it resumes normal hello. When the OSPF router ’ s neighbor state changing from "2-Way" or greater state back to "Init", it immediately sends Hello On broadcast and NBMA, the OSPF router sends Hello immediately when its interface role changed.

4. Benefits of Immediate hello On P2P, P2MP, virtual link, the time an OSPF router need to reach “ ExStart ” state is reduced from about 10 seconds to sub- second On broadcast, the time to reach “ ExStart ” state is reduced from about 10 seconds to sub-second when a link goes down then up

5. Convergence Time: Hello v.s. Immediate Hello (P2P) The time for DUT to reach “ Full ” state (millisecond) :

6. Convergence Time: Hello v.s. Immediate Hello (broadcast/NBMA) The experiment data is similar to P2P scenario The time for DUT to reach “ Full ” state (millisecond) :

7. Question and comment? Working group draft?