The Type Frame field of F frames along with the subclass field determines the function of the package that has been sent or received.They are the control signaling messages.
The Type Frame field is a set of 8 bits (1 byte) and the main values that can take are shown in the following table:
Table 1. Main values of the "Type Frame" field of F frames or Full Frame
"type frame" value
Description
Details
00000001
DTMF
To send DTMF digits
00000002
Voice Data
Subclass field show the audio codec used. See table 2.
00000003
Video
Subclass field show the video codec used.
00000004
Control
Provide session control. They refer to control of the devices connected to the IAX endpoint. Subclass field show the specific control message. See table 3.
00000005
No usado
00000006
IAX Control
Provide IAX protocol specific endpoint management. They are used to manage IAX protocol interactions that are generally independent of the type of endpoints. Subclass field show the specific IAX control message. See table 4.
00000007
Text
00000008
Image
00000009
HTML
Table 2. Meaning of the subclass values for Frame Type = "0x02" (voice data)
Subclass Value (Type Frame =0x02)
Description (codec used in the convesation)
0x0001
G.723.1
0x0002
GSM
0x0004
G.711 u (u-law)
0x0008
G.711 a (a-law)
0x0080
LPC10
0x0100
G.729
0x0200
Speex
0x0400
iLBC
Table 3. Meaning of the subclass values for Frame Type = "0x04" (control)
Subclass Value (Type Frame =0x04)
Description
0x01
Hangup
0x02
Ring
0x03
Ringing (ringback)
0x04
Answer
0x05
Busy Condition
0x08
Congestion Condition
0x0e
Call Progress
Table 4. Meaning of the subclass values for Frame Type = "0x06" (IAX control)
