While packet switched networks have numerous advantages in flexibility, efficient utilization of bandwidth and price per bit, circuit switching remains the more reliable paradigm (Copeland, 2000). Historically, circuit switching came first when telecommunications infrastructure grew in complexity to the point that technologies and terminology were developed to provide some unified structure and a conceptual abstraction to design and describe it (Ibid.). Concepts integral to packet switching have been around since the early 1960's (Living Internet, 2010). So circuit switching is a bit more mature and its behavior is well-known practically to the point of being deterministic but packet switching is becoming ubiquitous due to its efficient support of protocols like IP and better utilization of bandwidth (Laureate, 2010).
Frequency Division Multiplexing is less susceptible to latency than Time Division Multiplexing because all multiplexed streams are transmitting at the same time. However TDM is more flexible and efficient because it can dynamically adjust the time period allocation (Joan, 2010). This capability allows it to allocate more resources to those conversations that use them. Therefore it is exceedingly well suited to encapsulating data-link layer traffic that isn't too latency sensitive. Because FDM can't dynamically allocate spectrum the way TDM can time it has yet to demonstrate many advantages beyond that of low-latency. But FDM can be leveraged within TDM timeslices, offering the best of both. (Ibid.).
Copeland, L. (2000) QuickStudy: Packet Switched vs. Circuit Switched Networks [Online], Available from: http://www.computerworld.com/s/article/41904/Packet_Switched_vs._Circuit_Switched_Networks (Accessed: 9 October, 2010)
Joan, B. (2010) Difference Between FDM and TDM [Online]. Available from: http://www.differencebetween.net/technology/difference-between-fdm-and-tdm/ (Accessed: 9 October, 2010)
Laureate (2010) Seminar 1: Computer Networks and the Internet [Online]. Available from: https://elearning.uol.ohecampus.com/bbcswebdav/xid-9254_4
Living Internet (2010) Packet Switching History [Online]. Available from: http://www.livinginternet.com/i/iw_packet_inv.htm (Accessed: 10 October, 2010)