-----Original Message-----
From: Tom Herbert <[email protected]> 

> Correct, that's the fundamental problem. When public network providers apply 
> ad hoc protocol filtering, that limits the capabilities and opportunities to 
> provide value to the users. For instance, if someone came up with a new 
> transport protocol that improves user security by 10x, we couldn't deploy it 
> because some network providers would block it. So the very security policies 
> that are ostensibly in place to protect the users can actually harm them.

Potentially, I agree. Problem is, each of the players has to determine what is 
an acceptable risk. If an ISP wants to keep his infrastructure secure, he's got 
the responsibility to make it so, as best he can. He can’t trust mechanisms 
that either don’t exist yet or that might introduce their own new 
vulnerabilities. Someone says, trust me, these extensions will be for your own 
good, and yet he is fully cognizant that those extensions could also be used in 
ddos attacks, he'll say thanks but no thanks. Maybe I'll let those through 
after we're satisfied with testing and experience.

> As for what constitutes the "the greater good", like pretty much everything 
> else in IETF shouldn't that be something determined by "rough consensus"?

Yes, but unfortunately, that does not absolve the players of their own 
responsibilities. In matters of security, no one will blindly follow "rough 
consensus." We are 180 degrees from the Postel principle:

"Be conservative in what you do, be liberal in what you accept from others," is 
turned on its head, as we know. For system security, you cannot be liberal in 
what you accept from others.

> Even if the consensus were that extension headers need to be deprecated, to 
> me that would be better than the current situation where we, specifically 
> application and host developers, need to deal with a patchwork of anonymous 
> and seemingly arbitrary network provider policies that degenerate the end to 
> end services we can provide to users to rely only on least common denominator 
> of protocols which we can only deduce by guess work.

I get your point completely. We don’t have an IETF dictatorship though, so what 
happens is that over time, smart people have to decide how best to do their 
jobs, given the realities of today. There is a lot of infrastructure 
flexibility, and apps, thought really cool when they were developed, that go 
unused for just this reason. Such as, you might be better off, in your network, 
to use proxy-MLD and to block PIM-SM. Same goes for some or even much of ICMP. 
It's the tussle Brian C talks about.

Bert

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