Subject: RE: [Speermint] [wg-business] WGLCfordraft-ietf-speermint-terminology-12

From: "Dan Warren" <[email-masked]>
Date: Tue, 2 Oct 2007 09:45:29 +0100

All

Some of the points made by John (in his comments 14, 15 and 16) I agree
with but I think it goes further than that.  So rather than making a
proper comment, can I check my understanding of the terms as someone
that has picked the spec up recently and tried to understand it?

There are four terms relating to network types - peer network, service
provider, SIP Service Provider and Internet Telephony Service Provider.
The document states that SSP and ITSP are synonymous, although I might
argue that an ITSP is a subset of an SSP, purely because the 'T' part
suggests a specific service attributable to the UA's within that network
and hence also implies something about the way that service is delivered
(or at least ought to).  SSP is more general and hence could include
applications that do not have the same requirements on QoS and hence do
not require the same DSCP marking, but if you are all happy for these to
be equivalent, I am not going to fuss about the semantics of what is
implied by 'telephony'.

Now I get slightly confused.  A Peer Network sounds like it is a special
case of an SSP - in effect a peered SSP.  Is that correct?  If so I'd
suggest for readability of the document, SSP is defined before Peer
Network, and Peer Network is defined as I describe above.

Similarly, an SSP seems to be a specialised SP, in that not only does it
provide L3 transport of SIP signalling and media packets, but also
includes SIP end points.  Similar to my last point, it would help the
document to define SP before SSP, so that the definition of SSP can be
'An SSP is an SP that also includes UASs and UACs...' and then a Peer
Network can be defined as '...an SSP that has connections to peer SSPs
via...'.  A nice hierarchical definition (start with the broadest term
and get narrower' generally saves a lot of redefinition, which in itself
can create ambiguity.

And that leads me quite neatly on to a question - how are you
classifying the transit or carrier network that would sit between the
SSPs to provide interconnectivity?  It is clearly an SP since it will
provide L3 transport of SIP and media, but if my comments above are
right, SP is intended to be an umberella term covering all the
sub-variants of SP.  It will also need to have some characteristics
dependent upon whether it is expected to provide any additional
functionality - it clearly needs to be DiffServ aware, but it could also
be required to provide a bunch of functions around transcoding and
reframing in the media plane, and maybe SIP variant interworking, which
could imply B2BUAs.  It seems though that this network, be it the
internet or something provided by a carrier operator is only alluded to
in the definition of Federations.  Is there not a need to identify it
explicitly, even if it is far simpler than I have conceived it to be?  I
note that in the Architecture document, in Figure 3 a 'Transit IP
Provider' is identified (although the text never refers to Figure 3 nor
Transit IP Provider), but then in Figure 1 of the same document a whole
bunch of terms not defined in this document are used...

I'd appreciate at least comments on whether what I have laid out as the
herarchy of these terms is right or not, but I'm not going to get fussy
about whether the proposed shuffle of the ordering takes place.

Cheers

Dan

> > > 14) "3.8. Service Provider
> > > 
> > >    A Service Provider (or SP) is defined to be an entity
> > that provides
> > >    layer 3 (IP) transport of SIP signaling and media packets.  An 
> > >    example of this may be an Internet Service Provider (ISP)."
> > > This at first glance is reasonable, but then the next
> > section goes on to
> > > define a SIP Service Provider as something that is not a
> > special case of
> > > a Service Provider, since it operates at layer 5, not at 
> layer 3. We 
> > > should perhaps find a different term for "Service Provider"
> > when we mean
> > > layer 3, e.g., "Network Service Provider".
> > That's fine with me....although terms like this are ambiguous.  I 
> > think we had specified Internet Service Provider before, but there 
> > were arguments against being that "specific".  So, we 
> generalized the 
> > term and just provided it as an example.
> [JRE] I think we have to do something. The term SP is OK if 
> it is intended to embrace all types of SP that we are dealing 
> with, including SSP. But if we need a term for an SP that 
> operates only at layer 3, we need a different term.
> 
> > > 
> > > 15) "A SIP Service Provider (or SSP) is an entity that provides 
> > >    application level transport of SIP signaling to its 
> customers." 
> > > Elsewhere the document talks about level 5 peering, but 
> now it talks 
> > > about application level. Also, isn't it more than just 
> transport. I 
> > > don't have a particular proposal, but I don't really like
> > the present
> > > definition.
> > 
> > Hmmm...I'll see if I can think of something to make this clearer.
> > Anyone else have an opinion (heh...that's a stupid 
> question.  Everyone 
> > has an opinion, right?!)? :-)
> 
> > > 
> > > 16) "3.10. Internet Telephony Service Provider
> > > 
> > >    An Internet Telephony Service Provider, or ITSP, is a
> > synonym for
> > >    SSP. While the terms ITSP and SSP are frequently used 
> > >    interchangeably, the SPEERMINT working group uses the 
> term SSP."
> > > So why define the term if we are not going to use it? We
> > could mention
> > > it in a note below the definition of SSP, if really needed.
> > > 
> > ....don't care either way...we can do that to.  Does it 
> significantly 
> > make things simpler by doing as you suggest?
> [JRE] The point is, by having an explicit definition of ITSP, 
> it tends to encourage other SPEERMINT documents to use it, 
> even though there is an explicit statement that SPEERMINT 
> will use only SSP. I thought just making it a note below the 
> definition of SSP would help to de-emphasise ITSP further.

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From: "Elwell, John" <[email-masked]>
Date: Tue, 02 Oct 2007 10:24:16 +0100

Dan,

I agree with most of what you say. One point, however, is your proposal:
'An SSP is an SP that also includes UASs and UACs...' (which I guess
comes from text in the existing definition of Peer Network, which I
failed to comment on).

Is it a necessary condition that an SSP include UAs (other than B2BUAs,
perhaps)? I guess it depends what we perceive as the scope of an SSP.
UAs such as PSTN gateways, media servers, etc. might be considered part
of the SSP. But a UA in a user's home that uses the services of an SSP?
That to me is not really part of the SSP.

John

> -----Original Message-----
> From: Dan Warren [mailto:[email-masked]] 
> Sent: 02 October 2007 09:45
> To: Elwell, John; Daryl Malas
> Cc: Malas, Daryl; "Peterson, , dmm"@1-4-5.net; 
> [email-masked]; Livingood, Jason
> Subject: RE: [Speermint] [wg-business] 
> WGLCfordraft-ietf-speermint-terminology-12
> 
> All
> 
> This email and its attachments are intended for the above 
> named only and may be confidential. If they have come to you 
> in error you must take no action based on them, nor must you 
> copy or show them to anyone; please reply to this email or 
> call +44 207 759 2300 and highlight the error
> 
> 
>