Re: http/2 prioritization/fairness bug with proxies
William Chan (陈智昌) <willchan@chromium.org> Mon, 04 February 2013 17:51 UTC
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Date: Mon, 04 Feb 2013 09:49:54 -0800
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From: "William Chan (陈智昌)" <willchan@chromium.org>
To: Nico Williams <nico@cryptonector.com>
Cc: Amos Jeffries <squid3@treenet.co.nz>, HTTP Working Group <ietf-http-wg@w3.org>, Mark Nottingham <mnot@mnot.net>
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Subject: Re: http/2 prioritization/fairness bug with proxies
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Note that these priority labels would be suboptimal for browser usage. As I understand it, all requests within a page load would fall within a single priority level, probably priority 1 in your case. In my presentation, I demonstrated how browsers want to do resource request prioritization within the HTTP protocol level. Different resources have very different prioritization requirements within a page load, and unless the protocol supports client advisory priorities, the browser must make a link underutilization vs contention tradeoff. Specifically, the browser will withhold making HTTP requests for low priority resources under higher priority HTTP requests complete, so as to avoid contention. This achieves some amount of prioritization at the risk of underutilizing the link. As I understand it, your proposal also requires trustworthy clients to set the appropriate priority level, unless the proxy has some mechanism for determining the appropriate priority level by inspecting the stream, at which point the client requested priority is useless. I'm not sure that trusting clients to set the appropriate priority level for shared sessions is advisable. Opaque levels where only relative priority matters within a "group" is resilient to this problem. On Mon, Feb 4, 2013 at 8:46 AM, Nico Williams <nico@cryptonector.com> wrote: > > On Feb 4, 2013 8:05 AM, "Amos Jeffries" <squid3@treenet.co.nz> wrote: >> On 4/02/2013 11:01 p.m., Mark Nottingham wrote: >> > [...] > >> Which goes to show why specifying an algorithm for handling opaque >> client-selected prioritization is the wrong way to go about this. >> >> You have presented a good argument for specifying a set of standardized >> priority labels with criterion for setting each label. >> eg. >> Priority 1 - user actioned fetch - requires fast answer >> Priority 2 - background/automated fetch in user-visible window - requires >> fast answer but treat as bulk traffic. >> Priority 3 - automated software fetch - treat as low-speed traffic. >> Priority 4 - idle software probe - may drop if necessary. >> >> ... then letting the algorithm designers and implementers free to write >> their prioritization algorithms around those definitions. > > +1, plus priorities for real-time requests?
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- http/2 prioritization/fairness bug with proxies William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Yoav Nir
- Re: http/2 prioritization/fairness bug with proxi… Mark Nottingham
- Re: http/2 prioritization/fairness bug with proxi… Poul-Henning Kamp
- Re: http/2 prioritization/fairness bug with proxi… Ilya Grigorik
- Re: http/2 prioritization/fairness bug with proxi… Amos Jeffries
- Re: http/2 prioritization/fairness bug with proxi… Mark Nottingham
- Re: http/2 prioritization/fairness bug with proxi… Amos Jeffries
- Re: http/2 prioritization/fairness bug with proxi… Albert Lunde
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… James M Snell
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Poul-Henning Kamp
- Re: http/2 prioritization/fairness bug with proxi… Ben Niven-Jenkins
- Re: http/2 prioritization/fairness bug with proxi… Poul-Henning Kamp
- Re: http/2 prioritization/fairness bug with proxi… Patrick McManus
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Ashok Kumar
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Mike Belshe
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Martin Thomson
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Martin Thomson
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Martin Thomson
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Martin Thomson
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… Yoav Nir
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Amos Jeffries
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… Roberto Peon
- Re: http/2 prioritization/fairness bug with proxi… Amos Jeffries
- Re: http/2 prioritization/fairness bug with proxi… Nico Williams
- Re: http/2 prioritization/fairness bug with proxi… William Chan (陈智昌)