Subject: New Internet Draft on Flooding Simulation

From: "Choudhury, Gagan L, ALASO" <[email-masked]>
Date: Fri, 1 Nov 2002 15:45:39 -0500

We have just submitted the attached Internet draft "draft-choudhury-manral-flooding-simulation-00.txt".  Please give us comments electronically and during the OSPF WG meeting at Atlanta.  The Title and abstract are given below.

        Gagan Choudhury 
        Vishwas Manral

 <<draft-choudhury-manral-flooding-simulation-00.txt>> 

Title: LSA Flooding Optimization Algorithms and Their Simulation Study

Abstract: The full flooding of LSAs in OSPF may cause large CPU and memory
consumption at node processors of a network with large number of nodes,
links, adjacencies per node and LSDB size.  An LSA storm, defined as  
the near-simultaneous update of a large number of LSAs, in such  
networks may cause network instability and outage.

We do a simulation study of four alternative algorithms to full 
flooding to determine their ability to handle large LSA storms.
Algorithm 2 does full flooding but in case two neighbors are connected
by multiple interfaces, flooding is done over only one such interface.
The other algorithms are based on Algorithm 2 and employ
further flooding restrictions. In Algorithm 3 each node asks only
a subset of its one-hop neighbors, known as multipoint relays, to
flood further. In Algorithm 4 flooding is done only over a
minimum spanning tree. Algorithm 5 uses full flooding (as in Algorithm
2) for LSAs carrying intra-area topology information and restricted
flooding over a minimum spanning tree (as in Algorithm 4) for other
LSAs.

In terms of handling large LSA storms and in terms of robustness under
link failures, it appears that Algorithms 2 and 5 are the most 
desirable ones and it is proposed that they be pursued further.