- SPF Enhancements
- Flooding Enhancements
- Fragmentation
- Overloading
- Review Questions
Review Questions
Describe the modification to the simplistic SPF algorithm of Chapter 2 that allows ECMP.
Why is per-destination load balancing better than per-packet load balancing?
Why is per-flow load balancing better than per-destination load balancing?
What modification to the basic SPF algorithm is required, when there are equal costs involving both point-to-point links and broadcast links, to avoid disruption of ECMP?
What is Incremental SPF, and in what two general cases can it improve the efficiency of SPF in an area?
What is partial route calculation, and how does it improve the efficiency of SPF calculations?
How does SPF delay improve the efficiency of SPF calculations?
How can an excessive SPF delay reduce the performance of a network?
What is adaptive SPF delay, and what is its advantage over a set delay period?
Why are individual refresh timers for each self-originated LSA or LSP in a database better than a single monolithic timer?
How does adding a delay period to the refresh timers of self-originated LSAs or LSPs reduce problems associated with heavy flooding?
Under what circumstances can increasing the time a router waits for an acknowledgement of a transmitted LSA or LSP before retransmitting improve flooding efficiency?
What is a mesh group?
What are the advantages and disadvantages of using blocked mode in a mesh group?
What are the advantages and disadvantages of using set mode in a mesh group?
Can the three mesh group modes (inactive, blocked, and set) be used in the same network?
What is a demand circuit?
What is the OSPF DoNotAge bit?
What two changes are made to OSPF procedures in the extensions for support of demand circuits?
What is the purpose of the DC bit in the Options field of LSAs?
What is the purpose of the DC bit in the Options field of OSPF Hello and Database Description packets?
What does the presumption of reachability mean in regard to OSPF over demand circuits?
In what way can OSPF over demand circuits effect the consistency of LSA sequence numbers, and in what way can this be a problem?
What is OSPF flood reduction?
Why is fragmentation less of an issue with OSPF than with IS-IS?
What is the IS-IS ReceiveLSPBufferSize, and why are Hellos padded to this size during when attempting to form an adjacency?
What is the purpose of the LSP Number in the LSP header?
What happens if LSP Number 0 of a fragmented LSP is missing in a link state database?
What is the purpose of the IS-Alias-ID (type 24) TLV?
What does it mean when an IS-IS router is overloaded?
How is the OL bit useful in BGP transit networks?
What is the advantage of enabling an overload timeout option in BGP transit networks?
How can "overloading" behavior be created in an OSPF area?