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Spirent Test Center: How to modify DSCP values according to IEEE in QOS filed with modifier.

Objective/Summary
  • To provide settings to increment only on DSCP bits when we use modifier on QOS field.
Environment/Versions
  • Spirent Test Center
  • 4.80
  • DSCP
  • Modifier
Procedure
  • When we use diffserv in QOS and using modifier to increment DSCP values. By default, it takes increment on complete 8-bit QOS field.
  •  The first 6 bits in QOS field are DSCP and next two bits are ECN which is un used.
  • If we use default values in modifier, It increments on ECN part as well that leads to unknown Dscp code (Check Pcap file DSCPwithwrongmodifier ) as ECN part is unused according to IEEE. Please use below settings to increment only first 6 bits of DSCP.
  • Attached config file, please verify it once.
Notes
  • This is how we need to make changes to achieve this requirement.
  • Example: If we look at below screen shot of modifier, it is with default values. This increments from first bit in this one byte field. 
  • By default, Modifier settings in HEX format.  You need to convert into binary . Step value increments based on Mask that we give in MASK. Below settings increments from 1st bit (00000001) as mask defaults to FF

                           

  • As I look to increment only from 6 bits, Converting Mask to Maximum 6 bits like below and put HEX value in MASK and then it increments from 3 bit(00000100).

                           
    

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Product : Windows GUI