Advanced Computer Networks: Lecture 22. This lecture will cover the following: OSPF routing protocol; original ARPANET metric; how to make routing scale; mobile IP and challenges; flat versus hierarchical addresses;...
CS716 Advanced Computer Networks By Dr. Amir Qayyum Lecture No. 22 OSPF Routing Protocol • Authentication of routing messages – Encrypted communication between routers • Additional hierarchy – Domains are split into areas – Routers only need to know how to reach every node in a domain – Routers need to know how to get to the right area – Load balancing • Allows traffic to be distributed over multiple routes Original ARPANET Metric • Uniform 56 kbps lines – Bandwidth equal on every line (hence irrelevant) – Latency relatively unimportant • Use queue length as distance (number of packets waiting to use a link) Problems – Uniform bandwidth assumption became invalid – Latency comparable to 1kB transmission delay on 1.544 Mbps link How to Make Routing Scale • Flat versus Hierarchical Addresses • Inefficient use of hierarchical address space – Class C with 2 hosts (0.78% efficient) – Class B with 256 hosts (0.39% efficient) • Still Too Many Networks – Routing tables do not scale – Route propagation protocols do not scale Mobile IP Sending host (Network 12) Foreign agent (12.0.0.6) Home agent (10.0.0.3) (Network 10) Home network Internetwork IP tunnel (10.0.0.9) Mobile host Mobile IP Challenges • How does the MH get a local IP address ? • How does the HA intercept a packet that is destined for the MH ? • How does the HA then deliver the packet to the FA ? • How does the FA deliver the packet to the MH ? .. .Lecture? ?No.? ?22 OSPF Routing Protocol • Authentication of routing messages – Encrypted communication between routers