QoS markings in packet capture

[Scott Hanson]

I have a WireShark packet capture and need some assistance looking for DSCP and other QoS marking.  I can find in the capture under the IP header where there is a section that looks like this>Differentiated Services Field: 0x80 (DSCP: CS4, ECN: Not-ECT)

>Differentiated Services Field: 0x80 (DSCP: CS4, ECN: Not-ECT)

1000 00..=Differentiated Services Codepoint: Class Selector 4 (32)

.... ..00 =Explicit  Congestion Notification:: Not ECN=Capable Transport (0)

I am trying to see how I can tell exactly what QoS marking are there as in DSCP 46, EF

all replies rated.

Thanks

[Carlos Villagran]

Hi!

That packet is marked with Precedence 4.

You see the binary number at the left side of the Differentiated Services Codepoint? 1000 00 that is decimal 32 so this is DSCP 32.

There you should see 101 110 which is 46 in decimal meaning DSCP 46 or EF.

1000 00..=Differentiated Services Codepoint: Class Selector 4 (32)    

100000 = 32

Hope it helps, best regards!

JC

[Joseph W. Doherty]

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Posting

You're looking at the right place.

What can be confusing, DSCP is the first 6 bits of the ToS byte, so you numeric values for DSCP CS4 is 32 but the ToS byte value is 0x80.

Also the first 3 bits of the ToS byte also provides the old IPPrec values, in this case, IPPrec is 4.

For DSCP EF, the decimal value of the first six bits would be 46, but the the ToS byte value would be 0xb8.

If you work with something like extended ping, on a Cisco device, you can set the desired DSCP value, by setting the ToS byte to 4 times the decimal DSCP value.

NB: I didn't see Carlos' posting until after I posted mine.