36. Logical Channels in GPRS Above physical channels, a series of logical channels are defined to perform a series of functions which are signaling, broadcast of general system information, synchronization, channel assignment, paging, or payload transport
40. GTP header LFN : Flag indicating whether the LLC frame number is included or not. Message Type : Type of GTP message. Sequence number : Transaction identity for signaling messages and an increasing sequence number for tunneled T-PDUs. Flow label : Identifies unambiguously a GTP flow. LLC frame number : Used at the Inter SGSN Routing Update procedure to coordinate the data transmissions on the link layer between the MS and the SGSN. x : Spare bits x indicate the unused bits which are set to 0 by the sending side and are ignored by the receiving side. FN : Continuation of LLC frame number. TID : Tunnel identifier that points out MM and PDP contexts