[Cerowrt-devel] [aqm] ping loss "considered harmful"

Andrew Mcgregor andrewmcgr at google.com
Mon Mar 2 19:07:25 EST 2015

Maybe I should mention https://github.com/apenwarr/blip

HTTP ping, using deliberate 204 responses.  Will run over whatever version
of HTTP/SPDY/QUIC your browser happens to be using at the time.

On 3 March 2015 at 10:34, David Lang <david at lang.hm> wrote:

> On Mon, 2 Mar 2015, Joe Touch wrote:
>  On 3/2/2015 3:14 PM, David Lang wrote:
>>> On Mon, 2 Mar 2015, Joe Touch wrote:
>>>  On 3/2/2015 1:40 AM, Brian Trammell wrote:
>>>> ...
>>>>> The real solution is to create a utility called "ping" that uses
>>>>> traffic that gets prioritized the same way as the traffic you care
>>>>> about instead of ICMP echo request/reply. Users don't care about
>>>>> the packets on the wire so much as they do that you're supposed to
>>>>> ping things.
>>>> There are three separate problems:
>>>> 1. a ping that doesn't use ICMP
>>>>     there are dozens of these
>>>> 2. needing a reflector
>>>>     ping gets around this only because the reflector is widely
>>>>     deployed (and integrated into most OSes)
>>>> 3. using the same port as the traffic you care about
>>>>     transport protocol is only one problem (ICMP being a "transport
>>>>     protocol" by virtue of using the IP protocol number field)
>>>>     the other is differential prioritization based on port number
>>>>     there's no easy solution to that;
>>>>     every service would need an integrated
>>>>     ping reflector
>>>> I suspect #3 is the ultimate killer of this idea.
>>> The service you are trying to contact acts as a reflector for TCP
>>> traffic. If you send a syn you will get back a syn-ack from the TCP
>>> stack of the receiving system.
>> Sure, but SYNs and SYN-ACKs don't get prioritized the same as
>> non-control TCP segments. And they could have been spoofed by a middlebox.
> well, this is exactly the sort of thing that http heartbeat (the core of
> heartbleed) was designed to provide.
> It's not perfect, you can see where you really get the response from (vi
> the traceroute), and if you are going through a MITM (i.e. transparent
> proxy), all you are ever going to be able to test is the network between
> yourself and the proxy. It's up to the people who own the proxy to test
> beyond that.
> David Lang
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Andrew McGregor | SRE | andrewmcgr at google.com | +61 4 1071 2221
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