WAP limitations for GET and POST

[Irving Reid <Irving.Reid@baltimore.com>]

I did a bit of Googling around, and also asked some of the WAP folks within
Baltimore what limitations we can expect on URLs and POST data.

According to http://www.allnetdevices.com/faq/?pair=07.014, existing
browsers can send in the range of 500-1000 bytes as a URL parameter (i.e.,
GET) and about 1300 bytes as POST data.

The short answer for the future is, "it depends..." Unfortunately, it looks
like each client is allowed to pick its own limits and report them as part
of the User Agent Profile. There's no way to nail down a limit that's
guaranteed to work for every client without testing them all.

The "Binary XML" bytecode representation (WAP-192) might be useful to
produce a compact form of SAML assertions, but I can't see us sorting out
the issues with it in time for SAML 1.0.

The WAP specifications are available at
http://www.wapforum.com/what/technical.htm.


Here's the reply I got to my query within Baltimore:

> As you already know the size of the information that you can be "post" or
"get"
> is somewhat small. The sizes you mention are consistent with some of the
early
> browsers (1300 bytes for a post). As a rule the amount of data that can be
> transferred from  a mobile device will remain limited when compared to a
desktop.
> So it will always be handy to have a "constrained" profile of something
like SAML. 

> I found that using hidden fields and then POSTing them is a better way to
transfer
> information to the server (GETs tend to get truncate along the way :-) ).
All of
> this is WAP specific though. 

> Looking at the WAP standards:
> WAP-227 defines a persistent storage API accessible through WMLScript. No
mention
> is made of a size limit.
> WAP-223 defines cookies - A minimum of 4 cookies of 125 bytes each are
specified
> (there were some earlier mails on this)
> WAP-236 implies that the size of a WML document that can be handled can be
derived
> from the UAProf (user agent profile) information - so the device should be
able
> to tell you what size of wml docs it will support
> WAP-192 defines something called binary XML (bytecode representation of
XML to
> keep size down... This may be of interest to you in the SAML context...
> WAP-230 specifies limits on message sizes (at last) - By the look of
things
> message sizes are negotiated between the server and client. It defaults to
1400
> but may be more or less depending on the negotiation. I read somewhere
that the
> size limit is related to the IP packet size limit in the Ethernet world
(which
> is just over 1500 bytes or so). Anyway a lot of phones can handle more
these
> days...

 - irving - 


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