hi
CM Request = request for a dedicated channel
3GPP TS04.08
The CM SERVICE REQUEST message contains the
– mobile identity according to sub-clause 10.5.1.4;
– mobile station classmark 2;
– ciphering key sequence number; and
– CM service type identifying the requested type of transaction (e.g. mobile originating call establishment, emergency call establishment, short message service, supplementary service activation), location services)
CM = CONNECTION MANAGEMENT
It is a GSM protocol
/www.tutorialspoint.com/gsm/gsm_protocol_stack.htm
Regards
pix