| 367 | === More Sophisticated Packing: Multiple Passes === |

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| 369 | The previous examples have all treated packing containers onto physical machines as a single step process with a single parameter - the packing factor. In fact, we can divide containers into sets and pack each set independently using different parameters. For example in an experiment with many containers dedicated only to forwarding packets and a few modeling servers, we could create two sets and pack the forwarders tightly (a high packing factor) and the servers loosely. |

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| 371 | In return for the greater control on packing, there is a price. When a set of containers is packed, the containers system takes into account both the nodes to be packed and their interconnections. When subsets of containers are packed, the system cannot consider the interconnections between subsets. In some cases, the packing of subsets can lead to a DETER experiment that cannot be created successfully. This danger is mitigated by the fact that containers that are packed together are often related in ways that limit the number of connections between that set and another. |

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