CM service Parameter IP ToS bitmask 0x68

[shaftstri]

Hi,

There is a CallManager servcie called Tos Bitmask For Comm Between CCM and Device.

It says it is used for communication between CM and devices i.e signaling/stimulas

The default value is 0x68 in binary thats 1101000 or 104 in decimal.

How is the ToS/DSCP setting in the IP header calculated from the default value 0x68 ? I thought the default for DSCP was 26

Thanks

[Chris Deren]

ToS of 0x68 (104 decimal) is equal to DSCP 26.

The formula is DSCP * 4, so 26*4=104,

ToS Byte of IP Header is 8 bits, 6 of which are the DSCP bits and the last two are Flow control bits, so

011010 00 -> ToS 104, DSCP (first 6 bits) = 26.

The first 3 bits represent also IP precedance, so in this case 011 - IP precedance = 3

Consider DSCP 46 (RTP) as another example

ToS = 46*4=184

10111000, ip precedence = 5

Hope this helps,

Chris

[shaftstri]

Thanks Chris !