## Abstract

We consider a geometric model for the problem of minimizing access control lists (ACLs) in network routers, a model that also has applications to rectilinear picture compression and figure drawing in common graphics software packages. Here the goal is to create a colored rectilinear pattern within an initially white rectangular canvas, and the basic operation is to choose a subrectangle and paint it a single color, overwriting all previous colors in the rectangle. Rectangle Rule List (RRL) minimization is the problem of finding the shortest list of rules needed to create a given pattern. ACL minimization is a restricted version of this problem where the set of allowed rectangles must correspond to pairs of IP address prefixes. Motivated by the ACL application, we study the special cases of RRL and ACL minimization in which all rectangles must be strips that extend either the full width or the full height of the canvas (strip-rules). We provide several equivalent characterizations of the patterns achievable using strip-rules and present polynomial-time algorithms for optimally constructing such patterns when, as in the ACL application, the only colors are black and white (permit or deny). We also show that RRL minimization is NP-hard in general and provide O(min(n^{1/3};OPT^{1/2}))-approximation algorithms for general RRL and ACL minimization by exploiting our results about strip-rule patterns.

Original language | English |
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Title of host publication | Proceedings of the 18th Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2007 |

Publisher | Association for Computing Machinery |

Pages | 1066-1075 |

Number of pages | 10 |

ISBN (Electronic) | 9780898716245 |

State | Published - 2007 |

Externally published | Yes |

Event | 18th Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2007 - New Orleans, United States Duration: 7 Jan 2007 → 9 Jan 2007 |

### Publication series

Name | Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms |
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Volume | 07-09-January-2007 |

### Conference

Conference | 18th Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2007 |
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Country/Territory | United States |

City | New Orleans |

Period | 7/01/07 → 9/01/07 |

### Bibliographical note

Publisher Copyright:Copyright © 2007 by the Association for Computing Machinery, Inc. and the Society for Industrial and Applied Mathematics.