Every Exalt radio system is able to transport both TDM and Ethernet in their native modes.
Why is it important to transport TDM traffic natively? The answer is straightforward: because the alternative — encapsulating TDM traffic over Ethernet — can have such negative system and performance implications.
In order to carry TDM traffic over Ethernet, that traffic must undergo TDM to IP protocol conversion. The conversion process creates two problems:
- It can introduce a delay, or latency, of as much as 50 milliseconds; and
- It adds overhead, necessitating the use of 50% to 200% more throughput per TDM circuit than was required for the native TDM stream.
TDM traffic is highly latency sensitive, thus the introduction of delay above and beyond propagation delay threatens the integrity and availability of that TDM traffic. The risk associated with the additional conversion delay is especially acute in multi-hop connections in which the propagation delay is already significant, as well as best-effort throughput systems. With Exalt’s native TDM, extra delay is never a concern.
The problem with overhead is a practical one: system designers need more channel bandwidth in order to accommodate the overhead. That extra bandwidth may or may not be available and may or may not have an additional price tag associated with it. And using more bandwidth to carry the same user data traffic is anything but efficient. With Exalt’s native TDM, the available channel bandwidth carries only user traffic, not overhead.
Finally, by combining TDM traffic and IP traffic in a single IP stream, the TDM traffic is now subject to the variable latency and burstiness associated with normal Ethernet traffic. Just as TDM traffic depends on low latency for successful transmission, it also depends on constant latency. With Exalt’s native TDM, the radio system delivers the low and consistent latency performance of circuit-switched connections regardless of IP traffic behavior.
Why is it important to transport Ethernet traffic natively? To ensure the highest performance IP transport over the radio link.
Unlike TDM traffic, Ethernet traffic is packet switched and can be affected by traffic in any part of the network. including, the Internet itself. Ethernet latency varies widely because it is a shared, connectionless technology and, thus, demands techniques such as QoS to emulate circuit-switched performance for latency sensitive traffic such as VoIP and video over IP.
With Exalt’s native Ethernet, packets are processed at wireline speed, ensuring that no additional latency is introduced into the microwave link.