IP ToS/DSCP

[Patrik Lahti]

On 10-07-06 01:16 PM, sthaug at nethelp.no wrote:
>> dhcp-4.1.1 packet.c:143	ip.ip_tos = IPTOS_LOWDELAY;
>>
>> Just wondering if this should/will change? (would be easy to provide a
>> command line option I guess).
>
> Is it likely to matter at all? I don't consider DHCP a time critical
> service. As long as the server replies within a few seconds, the
> client should be happy.
>

I guess I should have made more of a point so you don't think I'm insane :-)

The first reason for changing is that IPTOS_LOWDELAY is deprecated, and 
DSCPs should really be used. Using a command line option lets the user 
decide.

I'm coming at this from a different angle - reliability, not low delay. 
DHCP can be considered to be network control type traffic. I.e. without 
it functioning, there will be no IP connectivity. Consider a situation 
where DHCP is renewing and due to excess packet loss (maybe because of a 
lot of other traffic is saturating the link at higher priority, above 
Best Effort) the renew messages are lost. Therefore DHCP enters 
discovery again and the IP address is removed from the interface...

PS. Same thing should really be done for IPv6 using IPV6_TCLASS socket 
option.

Cheers!
/P