Top of Rack
 demonstrates that most of the topology in Amazon Cloud is ToR mode.
- All servers in a track are first connected to a separate Top of Rack (ToR) switch, and then the ToR switch is connected to aggregate swtiches.
- Such a topology has currently become a mainstream network topology in a data center.
 A Measurement Study on Co-residence Threat inside the Cloud, by Zhang Xu, Haining Wang and Zhenyu Wu, in UsenixSecurity2016