EXFO FTB-8500 Series for FTB-500 - Manual (Page 236)

Stream Generation Tabs
222 FTB-8500 Series and FTB-8120NGE/8130NGE
MPLS
MPLS Configuration

Stacked Headers: Allows the activation of up to two MPLS headers.
The default setting is 1.

Label: Allows the selection of the MPLS TX labels (0 to 1048575). The
default label value is 16.

COS/EXP (Class Of Service / Experimental): Select the class of service.
The default value is 0 (0000 - Low).
0 (000 - Low)
1 (001 - Low)
2 (010 - Low)
3 (011 - Low)
4 (100 - High)
5 (101 - High)
6 (110 - High)
7 (111 - High)

TTL (Time To Live): Select the TTL value. Choices are 0 to 255. The
default setting is 128.