TM561
Case Study 2
By
Jeffery Long

What makes Zero1 unique is it uses only the wireless data links to handsets, rather than cellular voice links. It relies on others GSM network for service. However uses its own network except for last mile. When comparing the PSTN and the Voip network use a different set of protocols. For example, Voip uses TCP-IP, and the Session Initiation Protocol. The PSTN uses TDM frames in multiplexing, in addition to signaling protocols. Which is why, Voip requires an interface to sit at the border of both systems. Also on the PSTN voice is analog with the exception of when it goes thru the switch it becomes digital thru TDM. Most VOIP must interface to the internet for service i.e Zer01, others like ATT Uverse or Verizon FIOS are integrated into the PSTN of their telephone network. There is a case where the call originates and terminates on devices connected to the PSTN but the call’s routing is done over the Internet. This can be done as communication over the Internet is cheaper and typically used for international calls. There can be a case where the call originates and terminates on devices connected to the Internet but a part of the call’s route is over the PSTN. This can be the case when the circuit-switched link through the PSTN reduces the communication delay whereas the end-to-end Internet path may have a higher expected delay. Calls can be routed over the data network internally or over the internet externally, mobile telephony costs can be decreased significantly. There are several ways a VoIP can be attacked, the most common is the DoS attack, VoIP provide good cover for a DoS attack because all a hacker has to do is keep multiple packet streams running. There is Toll Fraud, this is when someone gains unauthorized access to a VoIP network and makes repeated long distance calls. Phishing through email is trying