The Root Cause:

NS-3 uses the SSID string as part of its internal hashing mechanism to seed random number generators for various network operations. When you change the SSID from "ns3-80211n" to "abc", you're inadvertently changing the seed values for:

Solutions:

Explicit Random Seed Control:

RngSeedManager::SetSeed(12345);

RngSeedManager::SetRun(1);