Re: [Sipping] New draft on end system communication services

[Xiaotao Wu <[e-mail]>]

On Fri, 18 Feb 2005, Arjun Roychowdhury wrote:

> Xiaotao/Henning,
>
> Thanks for the *excellent* draft. It effectively addresses a lot of
> CPL limitations. Even though your draft has the noble intent of
> end-devices, I can see B2BUA providers rubbing their hands in glee ;-)
>
> One quick comment: Is it at all possible to provide an interface using
> which a person creating a service  in LESS can do a database-dip to
> resolve a URI ?

Arjun,

Thanks for the comments!
Yes, we are thinking to extend CPL 'lookup' modifier.
Currently, the 'lookup' modifier has only one non-uri source --
'registration', or a uri-list. For proxy servers, that's usually enough,
but not enough for end systems. The 'lookup' modifier should be able to do
a database-dip to resolve a URI.

> Hardcoding URIs into scripts is often very limiting. To make it more
> general, it would be very useful if there was a way in which
> applications could 'intercept' the call flow of LESS for the only
> purpose of providing 'input' to the next stage.

In LESS, we defined a variable as 'action.last-action-result' to get the
return value of the last performed action. But usually, actions do not
return unpredictable values (so far, we only have UI:getinput to return
arbitrary values). For predictable action results, we use action
output (e.g., for 'call' action, it has 'accepted', 'busy' ... output) to
handle (branch) call decisions. This way, it's easier for static script
analysis, e.g., feature interaction handling when merging multiple scripts
into one for execution.

Thanks!

-Xiaotao

>
> More comments later as I digest the rest.
>
> regds
> arjun
>
>
>
> On Thu, 17 Feb 2005 19:33:16 -0500 (EST), Xiaotao Wu
> <[e-mail]> wrote:
> > We have written a new draft on the Language for End System Services (LESS)
> >
> > http://www.ietf.org/internet-drafts/draft-wu-iptel-less-00.txt
> >
> > This work can be closely related to the SIP P2P work because in a P2P
> > network, there is no infra-structure to provide communication services,
> > for example, phone spam filtering. Usually, users will not put their
> > services on peers' node due to privacy and security reasons. That makes
> > end system services very important, and it is necessary to define a
> > mechanism for end system service creation.
> >
> > >From the abstract:
> >
> >    In Internet telephony, end systems can take a large role in providing
> >    services, especially in networks without pre-configured
> >    infra-structure, such as peer-to-peer networks.  Since we believe
> >    that end system services differ in their requirements from network
> >    services, we define a new service creation scripting language called
> >    the Language for End System Services (LESS).  LESS inherits many
> >    characteristics from the Call Processing Language (CPL).  It contains
> >    commands and events for direct user interaction and the control of
> >    media applications.  This document defines the basic elements of LESS
> >    and several commonly used LESS extensions.
> >
> > Suggestions and comments would be appreciated.
> >
> > -Xiaotao
> >
> > ===========================================================
> > Name      : Xiaotao Wu
> > Email     : [e-mail]
> > Homepage  : http://www.cs.columbia.edu/~xiaotaow
> > Phone     : [phone],  Fax: [phone]
> > Phone-PC  : [phone]
> > SIP       : sip:[e-mail]
> > Office    : Room 506, Computer Science building, West 120th
> > ===========================================================
> >
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> >
>
>
> --
> Arjun Roychowdhury
>

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