RE: Web Intents for local network services (DAP Action-510)

Hi again,

It seems as the requirement in the UPnP Device Architecture 1.1 specification that each discovery message MUST fit entirely in a single UDP packet, that might be down to 512 bytes, prohibits us to define long headers that perform full Web Intents Service registrations. So currently I see no other option than relying on the Device Description document, as proposed in Shenzhen, for Service registration. 

In addition to this we could just add one extra header "action.webintents.org:...." that helps UA's Web Intents implementation to filter SSDP responses. It would be good to have a " type.webintents.org:.." header as well but then we risk to exceed the limit of 512 bytes if several types are supported.

What do you say. Any views?

Claes

-----Original Message-----
From: Nilsson, Claes1 
Sent: den 22 maj 2012 12:55
To: 'Dave Raggett'
Cc: Cathy.Chan@nokia.com; public-web-intents@w3.org
Subject: RE: Web Intents for local network services (DAP Action-510)

Hi again Dave,

Regarding line breaking rules for SSDP I assume that the HTTP rules apply. RFC2616, section 4.2 states: 
"Header fields can be extended over multiple lines by preceding each extra line with at least one SP or HT."

However, the length of SSDP packets is an issue. Section 1.2.2 in UPnP(tm) Device Architecture 1.1 states:

"Note that UDP packets are also bounded in length (perhaps as small as 512 Bytes in some implementations); each discovery message MUST fit entirely in a single UDP packet. There is no guarantee that the above 3+2d+k messages will arrive in a particular order."

So if UDP packets can be as small as 512 bytes and each discovery message MUST fit entirely in a single UDP packet we have a problem. One option would be to just add the action.webintents.org and type.webintents.org headers, which makes it possible for UAs to filter responses based on these headers and only retrieve the Device Description, that contains the full Service registration markup, for matching Services. 

We are further investigating the issue.

Best regards
  Claes



-----Original Message-----
From: Dave Raggett [mailto:dsr@w3.org] 
Sent: den 21 maj 2012 18:04
To: Nilsson, Claes1
Cc: Cathy.Chan@nokia.com; public-web-intents@w3.org
Subject: Re: Web Intents for local network services (DAP Action-510)

On 21/05/12 16:35, Nilsson, Claes1 wrote:
> Hi Dave,
> 
> Yes, this is a good idea but want to be sure that we don't propose something that is against the UPnP standard. Taking the example at slide 10 would the following be ok?
> 
> registration.webintents.org:
> [{"action":"http://webintents.org/view",
>   "type":["video/mp4", "video/ogg", "video/webm"],
>   "href":"/control.html",
>   "title":"Living room TV",
>   "disposition":"window"},
>  { ...2nd service...},
>  { ...3rd service...}]
> 
> Regards
>   Claes

Yes, that seems fine to me so long as we conform to the line breaking
rules for SSDP, which at a guess may be similar to those for HTTP. The
SSDP spec may also have some wording about maximum line or field
lengths, so that would be worth checking too.

Best regards,
-- 
Dave Raggett <dsr@w3.org> http://www.w3.org/People/Raggett

Received on Friday, 25 May 2012 11:05:45 UTC