Re: H2 Implementation Debug State URI

[Cory Benfield <[e-mail]>]

> On 9 Aug 2016, at 16:59, Alex Rousskov <[e-mail]> wrote:
> 
> On 08/09/2016 03:50 AM, Cory Benfield wrote:
> 
>> For those that don’t add support, they blindly forward the request
>> on, running the risk of information leakage and invalid/incorrect
>> responses.
> 
> I do not see how Max-Forwards unsupporting proxies can have a
> significant negative effect on the problem you are trying to solve.
> Obviously, you will not get their debugging state, but that is going to
> happen no matter what -- there will always be proxies that do not
> support your new feature. Why would Max-Forwards unsupporting proxies
> produce invalid responses? They will just forward the response the next
> hop gives them, and that response would be correct or incorrect
> regardless of what they do.
> 
> AFAICT, Max-Forwards essentially lets you interrogate supporting hops.
> Unless you change the protocol to require debugging support, nothing you
> can do will let you interrogate unsupporting hops.
> 
> This overall problem feels very similar to traceroute -- it does not
> always work and not all hops support ICMP TTLs, but it works well enough
> in many cases to remain useful.
> 

I think this summary is true if HPACK information is removed from the debugging output. So using Max-Forwards is conditional on not dumping HPACK. That may be an acceptable compromise.

Cory