EXFO FTB-8500 Series for FTB-500 - Manual (Page 246)

Stream Generation Tabs
232 FTB-8500 Series and FTB-8120NGE/8130NGE
Frame Configuration (Fibre Channel)

CS_CTL: The Class Specific Control field contains management
information for the class of service identified by the SOF. The default
setting is hexadecimal 00 corresponding to no preference and no
specific DSCP. Possible values for Class 3 service are:

S_ID: The source identifier specifies the source port address. Choices
are listed in the D_ID table. Refer to D_ID for more information. The
default setting is hexadecimal 000000.
Note: The source identifier address may be affected by the login process.

TYPE: The Data Structure Type indicates the type of data contained in
the data field. The default value is FF corresponding to Vendor specific.
Bit Description
31 PREF (Preference)
0 = Frame is delivered with no Preference
1 = Frame may be delivered with Preference
30 Reserved for additional Preference function
29-24 DSCP (Differentiated Services Code Point)