The called side terminal equipment shall check that the content of the Low layer compatibility information element is compatible with the functions it supports.
The Low layer compatibility information element (if available) shall be used to check compatibility of low layers(e.g. from layer 1 to layer 3, if layered according to the OSI model).
Note - The Bearer capability information element is also checked (see B.3.2). Therefore, if any conflict from duplication of information in the Bearer capability and the Low layer compatibility information elements is detected, this conflict shall be resolved according to Annex I, e.g. the conflicting information in the Low layer compatibility information element shall be ignored.
If the Low layer compatibility information element is not included in an incoming SETUP message, the Bearer capability information element shall be used to check the compatibility of low layers.
The called terminal equipment may check the High layer compatibility information element (if present) as part of user-to-user compatibility checking procedures, even if the network only supports bearer services.
If a mismatch is detected in checking any of the information elements above, then the terminal equipment shall either ignore or reject the offered call using cause No. 88, incompatible destination (see 5.2.2).