However, since these protocols themselves utilize a protocol that may experience packet loss, it cannot be guaranteed that the network management applications can be utilized. A simple mechanism in the network layer is required so that systems can be probed to determine if the lowest levels of the networking software are operating correctly. The complexity of the echo facility must be kept low. If it is not, then there is a good chance that the facility will not be universally provided. An echo path must succeed and fail in unison with the normal data path or else it will not provide a useful diagnostic tool.
Backward compatibility is an important consideration whenever a change is made to a protocol.
The short term approach will produce echo packets that are indistinguishable from normal data ISO 8473 PDUs. These echo packets may be switched through ISO 8473 routers that do not implement the echo function. The short term approach will be adopted as an Elective Internet Standard because it is backward compatible with ISO 8473. However, due to its nature, the short term approach will never be incorporated into future versions of ISO 8473. The long term approach will produce echo packets that are not compatible with the existing standard.