BCP regarding TOS transparancy for internet traffic

[Mikael Abrahamsson <swmike () swm pp se>]

I've been debating whether the TOS header information must be left 
untouched by an ISP, or if it's ok to zero/(or modify) it for internet 
traffic. Does anyone know of a BCP that touches on this?

My thoughts was otherwise to zero TOS information incoming on IXes, 
transits and incoming from customers, question is if customers expect this 
to be transparent or not.

Reading <http://www.sanog.org/resources/sanog4-kaulgud-qos-tutorial.pdf> 
it looks like in the Diffserv terminology, it's ok to do whatever one 
would want.

Any feedback appreciated.

--
Mikael Abrahamsson    email: swmike () swm pp se