1.3.10. [CHP] Section

The Channel Protocol (CHP) component resides on the control processor and implements the telephony communication protocol that is used on each network interface. There are different versions of this component for handling different signaling types as well as different protocol types on different B channels. There is one CHP instance created for each B channel in the system.

The [CHP] section of the CONFIG file is a subset of the [TSC] section. Protocol specific parameters, primarily in the form of variants, are defined in the [CHP] section. The selection of which of these protocol variants to use on which line (span) is determined in the [TSC] section. For more information on protocol variants selection, see Section 1.3.11, [TSC] Section.

A number of protocol variants are defined in the CONFIG file. Variants are defined by the Variant Define n command, where n is the variant identifier. The Variant Define n command defines variant "n" as all of the parameter definitions in the [CHP] section preceding the command.

Note: If a parameter is defined multiple times prior to the Variant Define n command, then only the last definition of the parameter is used for that variant.

Example:

! T1 Protocol variant definitions
Variant VariantFormat         1     !T1 CAS format
Variant ProtocolType          1     !E&M=1,LS-FXS=2,GS-FXS=3
Variant Wink                  y
Variant Dial                  y
Variant DialFormat            1     !DTMF=1, MF, DP
Variant ANI                   0     !No=0, Pre, Post
Variant ANIFormat             1     !DTMF=1, MF, DP
Variant ANICount              0
Variant DNIS                  y
Variant DNISFormat            1     !DTMF=1, MF, DP
Variant DNISCount             0
Variant CallProgress          y
  .
  .
  .
! Define Protocol Variant 2 as T1 E&M Wink Start, DTMF Dial & 
! DNIS + callProgress
Variant Define 2

! Note: Previous variant parms are kept, and the following 
! commands replace the specified parameters

! Define Protocol Variant 5 as T1 Loop Start FXS, DTMF Dial 
! & DNIS, callProgress, and DialTone detection.
Variant ProtocolType          2     !E&M=1,LS-FXS=2,GS-FXS=3
Variant Wink                  n
Variant Define 5

! Define Protocol Variant 4 as T1 E&M Wink Start, no tone 
! and no callProgress
Variant ProtocolType          1     !E&M=1,LS-FXS=2,GS-FXS=3
Variant Wink                  y
Variant Dial                  n
Variant DNIS                  n
Variant CallProgress          n
Variant Define 4

! Define Protocol Variant 6 as Ground Start FXS
Variant ProtocolType          3     !E&M=1,LS-FXS=2,GS-FXS=3
Variant Wink                  n
Variant Dial                  y
Variant DNIS                  y
Variant CallProgress          y
Variant Define 6 

From the [CHP] example, selecting protocol variant 2 would include all the parameter definitions from the beginning of the [CHP] section to the Variant Define 2 line. This would define the protocol as T1 E&M Wink start, DTMF dialing, DNIS digits, with call progress (ProtocolType = 1, Wink = y, Dial = y, DialFormat = 1, DNIS = y, CallProgress = y).

If, however, you were to select protocol variant 5, this would include all of the parameter definitions from the beginning of the [CHP] section to the Variant Define 5 line. In this case, the protocol type would change to LS-FSX (Loop start) and Wink Start would be disabled, but DTMF dialing, DNIS digits, and call progress would still be used (ProtocolType = 2, Wink = n).

If protocol variant 4 were selected, all of the parameter definitions from the beginning of the [CHP] section to the Variant Define 4 line would be included. Now, the protocol type would change back to E&M Wink start with no DTMF dialing, no DNIS digits, and no call progress (ProtocolType = 1, Wink = y, Dial = n, DNIS = n, CallProgress = n).

You may also create your own variant if none of the existing defined protocol variants match your need. For example, to create a new protocol variant in which you want to use E&M Immediate start (instead of Wink start) with no ANI/DNIS digits provided, you may add another Variant Define n after the Variant Define 2 statement. In this example, we can use n = 1 because this number has not yet been defined in the CONFIG file. That part of the [CHP] section would then become:

! Define Protocol Variant 2 as T1 E&M Wink Start, DTMF Dial & DNIS + callProgress
Variant Define 2
! Define Protocol Variant 1 as T1 E&M Immediate Start, DTMF Dial + callProgress
Variant Wink	                     n
Variant DNIS	                     n
Variant Define 1 

By disabling DNIS in protocol variant 1, which follows protocol variant 2, we have also caused DNIS to be disabled in protocol variant 5. DNIS was originally enabled in protocol variant 5 because protocol variant 5 followed protocol variant 2 which defined it as enabled. We will now need to re-enable DNIS in protocol variant 5 as shown in the following example:

! Define Protocol Variant 5 as T1 Loop Start FXS, DTMF Dial 
! & DNIS, callProgress, and DialTone detection.
! Add DNIS back to this protocol variant
Variant DNIS                     y
Variant ProtocolType 2  ! E&M=1, LS-FXS=2, GS-FXS=3
Variant Wink n
Variant Define 5 

Although protocol variants are defined in the [CHP] section, protocol variants are assigned in the [TSC] section of the CONFIG file. Selecting a particular Variant Define n is accomplished by changing the values of the Inbound and Outbound parameters for a particular line. The Inbound and Outbound parameters are the sixth and seventh parameters respectively in the defineBSet command in the [TSC] section of the CONFIG file.

For information about the defineBSet command and setting TSC parameters, see Section 1.3.11, [TSC] Section.

For information about each CHP parameter, see the following sections:

• Section 4.15, [CHP] Parameters.
• Section 4.16, [CHP] T-1 Protocol Variant Definitions.
• Section 4.17, [CHP] ISDN Protocol Variant Definitions

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