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Re: ACTION-961: usefulness of multipart-mixed

From: John Hardi <john.hardi@motricity.com>
Date: Thu, 28 May 2009 16:35:56 -0700
To: Luca Passani <passani@eunet.no>
CC: Mobile Web Best Practices Working Group WG <public-bpwg@w3.org>
Message-ID: <C6446DEC.259A%john.hardi@motricity.com>

Thanks for the test sample ;).  As previously discussed, device-specific
overrides are needed for this (and a number of other features which device
manufacturers are overly optimistic about).  The ³dogfood² site lacks the
full set of overrides that one of our production sites would have, but its
the only site I can  point to which doesnıt require authentication. The
intent was to satisfy Tomıs request for an example of how the response was
constructed.  Hopefully it accomplishes that.


Note to self: Next time donıt pick the first device that shows up on the
DeviceAtlas homepage as the UA string to use in lieu of curl ;>

On 5/28/09 2:56 PM, "Luca Passani" <passani@eunet.no> wrote:

> John, I just happened to have a N95 8Gb in my drawer, so I hit your site with
> it. The XHTML was there, but none of the pictures were loaded.
> This checks out with what I was experiencing with multipart/mixed on Nokia
> devices back in 2003-2004 with Nokia 3650 and 6600, which, in turn, made me
> conclude that accept header and UAProf were a totally unreliable source of
> information to decide which devices can manage multipart.
> I am sure that Ericsson does it well because they do actual testing with
> devices.
> Luca
> John Hardi wrote:
>>  Re: ACTION-961: usefulness of multipart-mixed Tom,
>> We developed it in-house and I donıt have an open source code example I can
>> point you to.  If you want to see it in operation, the ³dogfood² site for our
>> platform m.mcore.com has multipart enabled.  If you go there with a
>> multipart-capable device, you should get a multipart payload.
>> If you have curl, this should get you todayıs home page in multipart:
>> curl -H "Accept:
>> text/html,application/xhtml+xml,application/xml,multipart/mixed" -A
>> "Mozilla/5.0 (SymbianOS/9.2; U; Series60/3.1 NokiaN95_8GB-3/20.2.005
>> Profile/MIDP-2.0 Configuration/CLDC-1.1 ) AppleWebKit/413 (KHTML, like Gecko)
>> Safari/413" http://m.mcore.com/motricity/ptl/px/home/i.aspx
>> An unscientific snapshot from one set of web servers showed a bit over half
>> the mobile pages being delivered in multipart.
>> As I mentioned in my original post, the degree of difficulty for multipart
>> may  make it unsuitable as a ³best practice² recommendation.  Itıs use is
>> probably most suitable for sites where performance is critical and worth the
>> investment.  But I did want to address the misconceptions that multipart
>> being archaic or only being used in network components.  It is a viable
>> technique which addresses some of the considerations of sections 3.4.5 and
>> 3.5.2 of the best practices.
>> John
>> On 5/28/09 12:38 AM, "Tom Hume" <tom.hume@futureplatforms.com> wrote:
>>> John
>>> Do you have some example code for this sort of thing, or can you point me at
>>> some?
>>> Tom
>>> 2009/5/27 John Hardi <john.hardi@motricity.com>
>>>> Tom,
>>>>> >From a CP POV, one would use it  to improve performance of pages which
>>>>> have a number of frequently changing  dynamic content parts (i.e. images).
>>>> By using the absolute URI/URL of a resource for the Content-Location header
>>>> URI of its part , you shouldnıt need to change the references in the base
>>>> (X)HTML part.  This allows a packaging filter on the front of your web
>>>> serverıs page processing to handle it in a fairly generic fashion.  In
>>>> general, I think this is consistent with RFC 2557.  As for support, itıs
>>>> fairly broad ‹ certainly more broad than CSS2, though that hopefully wonıt
>>>> remain the case.
>>>> John
>>>> On 5/27/09 12:46 PM, "Tom Hume" <tom.hume@futureplatforms.com
>>>> <http://tom.hume@futureplatforms.com> > wrote:
>>>>> John
>>>>> How, from a content provider POV, does one make use of this? How would I
>>>>> refer to a specific resource within a multi-part/mixed response - using
>>>>> some sort of URL scheme? And how well supported is this, in your opinion?
>>>>> Tom
>>>>> 2009/5/27 John Hardi <john.hardi@motricity.com
>>>>> <http://john.hardi@motricity.com> >
>>>>>> Magnus & Tom,
>>>>>> While not a regular contributor, I did want to add a bit of perspective
>>>>>> on this topic.
>>>>>> First I must concur with Magnus that MIME multipart is still in use and
>>>>>> can improve the userıs experience in page load times as a round-trip
>>>>>> latency reduction tool.  While it can be a network optimization as Magnus
>>>>>> describes, the benefit is actually greater if done at the page source,
>>>>>> thus eliminating the multiple round trip latencies between the mobile
>>>>>> network gateway / proxy and the CP as well as from the handset across the
>>>>>> mobile network.
>>>>>> Sprites / Composite images are not comparable; they only offer
>>>>>> improvement for static, decorative images.  If the multiple images/parts
>>>>>> of a page are dynamic content (news photos, album art, etc.) multipart
>>>>>> still provides benefit where sprites would not.  It also provides the
>>>>>> delivery performance benefits of embedded CSS with the flexibility of a
>>>>>> linked style sheet.
>>>>>> Being a content type, use of multipart is independent of
>>>>>> Content-Encoding.  So itıs not required that multipart payloads be
>>>>>> gzipped, though doing so may be worthwhile where it is also supported by
>>>>>> the device.
>>>>>> There are cases, as Luca describes, where devices advertise support in
>>>>>> HTTP headers but donıt necessarily handle it well.  So device awareness
>>>>>> and the ability to override the devicesı claim of support is necessary.
>>>>>> However, I donıt believe this is significantly different from other
>>>>>> advertised device / browser capabilities (CSS2 positioning, for example).
>>>>>> The degree of difficulty may make multipart debatable as a best practice,
>>>>>> but I donıt consider it irrelevant ³from the content providerıs point of
>>>>>> view².
>>>>>> Hope this helps...
>>>>>> John Hardi
>>>>>> Dir, Technology Strategy
>>>>>> Motricity, Inc.
>>>>>> On 5/27/09 12:22 AM, "Magnus Lönnroth" <magnus.lonnroth@ericsson.com
>>>>>> <http://magnus.lonnroth@ericsson.com>
>>>>>> <http://magnus.lonnroth@ericsson.com> > wrote:
>>>>>>> Yes, I'm referring to HTTP responses. A proxy is needed. URL-rewriting
>>>>>>> is needed. I'm not sure if the context for my response was appropriate -
>>>>>>> I was just reacting to the previous statements saying that packaging
>>>>>>> content in multi-part MIME digests was kind of obsolete. From the
>>>>>>> content provider's point of view MIME multi-part digests are irrelevant
>>>>>>> and have probably always been so. From the service provider's point of
>>>>>>> view it's still an important network level optimization. But it should
>>>>>>> be completely transparent and hence most likely not part of a best
>>>>>>> practices discussion. Sorry if I'm confusing matters.
>>>>>>>  /Magnus 

 From: Tom Hume  [mailto:tom.hume@futureplatforms.com]
 Sent: Wednesday, May 27, 2009  8:51 AM
 To: Magnus Lönnroth
 Cc: Luca Passani; Mobile Web  Best Practices Working Group WG
 Subject: Re: ACTION-961: usefulness  of multipart-mixed
Are you referring to using multi-part/mixed for HTTP responses from a web
If so, can you explain how resources within a multi-part/mixed HTTP
response are referred to from each other, or from outside the response?
2009/5/27 Magnus Lönnroth <magnus.lonnroth@ericsson.com
<http://magnus.lonnroth@ericsson.com>  <http://magnus.lonnroth@ericsson.com>
Hi,  delivering multi-part MIME digests has been and still is an important
part  of optimizing performance in our installations. The main reason for
developing this is the latency in 3g networks compared to wired broadband or
wi-fi. It must of course be fully transparent and not affect content or
content design in any way. One important aspect is to have detailed
knowledge of the device's own caching capabilities and support for digests
so that subsequent deliveries not include content that is already available
(cached) on the handset. If full digests are delivered with each request I
agree that the benefit is questionable. But if you have a good
implementation with device knowledge the improvement is  significant.
Magnus  Lönnroth
Head of Development
Service Delivery & Provisioning,  Ericsson ///
> -----Original Message-----
> From: public-bpwg-request@w3.org <http://public-bpwg-request@w3.org>
>  [mailto:public-bpwg-request@w3.org] On  Behalf Of Luca Passani
> Sent: Tuesday, May 26, 2009 11:49 PM
>  To: Mobile Web Best Practices Working Group WG
> Subject: Re:  ACTION-961: usefulness of multipart-mixed
> Multipart  was a useful mechanism to deliver a full page in one shot.
> Vodafone  leveraged multipart for its vodafone live service on
> devices which  supported it. Multipart allowed for snappy (or at least
>  "2002-snappy") display of the top page, which looked great as
>  compared to everything WAP had represented until that day.
> There was  no way to know whether multipart was properly
> supported by a device,  except testing on that device.
> Notably, many devices declared  multipart support in headers
> and UAProfs, but the information was  not reliable at all. I
> recall that I never managed to get multipart  to work on a
> Nokia device (still vaguely curious about whether there  was a way).
> Vodafone maintained its own db with this info for  devices in
> its portfolio. Not sure if they still do. Probably not.  Too
> much effort for too little value.
> 3G networks  and faster browsers make the use of multipart
> much less relevant,  particularly because pages become much
> harder to build and maintain  if multipart is in the middle. I
> made space for multipart in WURFL  back in 2003, but the
> community did not really follow: nobody was  using it obviously.
> Luca
> Tom Hume  wrote:
> > I took an action a couple of weeks ago to look into  multipart/mixed
> > MIME types, to see if they might be usefully  related to
> sections 3.4.6
> > and 3.4.7 of MWABP[1]  (ACTION-961). In particular it would seem
> > helpful to be able to  bundle many images up into a single HTTP
> > request, avoiding  unnecessary round trips to download a set
> of them.
> > The  current advice is to combine related images into a single file,
> >  download this, and use CSS positioning and clipping to
> render parts  of
> > this file. multipart/mixed would provide another route  for
> downloading
> > many resources at once.
>  >
> > The only reference I can find to mobile usage of  multipart-mixed is
> > this tutorial from OpenWave:
>  >
> >
> http://developer.openwave.com/dvl/support/documentation/technical_note
>  > s/multipart.htm
> >
> > From running this experiment  with desktop browsers, multipart-mixed
> > doesn't seem to be well  supported. I've set up an HTTP response
> > matching the above and  found that:
> >
> > - Firefox and Opera render the second  page in the message
> > - Safari doesn't recognise it as HTML and  downloads it
> > - IE renders content from both pages
>  >
> > I've also got a question of how, from within CSS or  similar, an
> > individual part of a multipart-mixed message might  be uniquely
> > referred. The only reference I can find for a  URL-scheme for such
> > things is a scheme for references to body  parts of messages, which
> > date back to 1997 or earlier, and seem  to be designed with
> HTML email
> > in mind:
> > http://www.ietf.org/rfc/rfc2392.txt
> >
>  > Beyond the Openwave tutorial, and the following tool which
>  exists to
> > create these messages:
> >
> > http://www.umts-tools.org/docs/multipart/
>  >
> > ...I can't find any other reference to them; and it's not  a
> technique
> > I've come across myself. Am I missing  something obvious here? From
> > where I'm sitting this looks like  a barely-used, poorly- supported
> > technique which I'd hesitate  to consider a best practice -
> though it
> > might be handy  if it worked.
> >
> > Tom
> >
> > [1] http://www.w3.org/TR/2009/WD-mwabp-20090507/#d1e8981
>  >
> > --
> > Future Platforms: hungry and foolish since  2000
> > work: Tom.Hume@futureplatforms.com <http://Tom.Hume@futureplatforms.com>
>  > <mailto:Tom.Hume@futureplatforms.com>  play: tomhume.org
<http://tomhume.org>  <http://tomhume.org>  <http://tomhume.org>
>  > <http://tomhume.org>
> >
>  >

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Received on Thursday, 28 May 2009 23:36:47 UTC

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