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On 8/21/07 7:31 PM, Chris Cappuccio wrote:
quoted text
> On a related note, I work with some equipment that uses TOS values and
> some that uses DSCP.
> 
> When you see a TOS value in tcpdump (0x68 for instance) just divide by 4
> to get the DSCP (and throw away any remainder.)  The DSCP value uses the same
> field in the IP packet as TOS, but ignores the last bits.  So, DSCP to TOS
> is simply multiply by 4 (and convert to hex)

Yes and no. TOS field definitions have changed over the years; there's a
history of this moving target in RFC 3168, section 22.

The 6-bit DSCP field is defined in RFC 2474. It does not ignore anything
in TOS; if anything it's a superset.

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