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Fwd: B2B proposal

  • From: "Strickland, Tom" < >
  • To:
  • Subject: Fwd: B2B proposal
  • Date: Thu, 13 Jun 2013 16:46:39 +0100

Forwarded on behalf of Keith, as his emails seem to be bouncing off the list. I will add my own thoughts in a subsequent email.

---------- Forwarded message ----------
From: Lewis, Keith < " target="_blank"> >
Date: Thu, Jun 13, 2013 at 4:34 PM
Subject: Re: B2B proposal
To: " target="_blank">


Some comments inline below.


--------- Forwarded message ----------
From: Jonas Borjesson < " target="_blank"> >
Date: Wed, Jun 12, 2013 at 7:28 PM
Subject: Re: B2B proposal
To: " target="_blank">

Hi all,

I agree with George – i.e., 1A is my preferred solution since as I'm
sure you know by now that I like interfaces, things become more
explicit. Apart from that, I do have a few other questions/comments:

=== Consistency ===
The suggestion calls for a lot of new very specific methods, such as
SipFactory.createContinuationRequest and

The first two ones are very specific but the third one has two
meanings, incoming and outgoing which is defined by the UAMode. Going
with the rest of the methods and the overall intent of the proposal
should they just be renamed to
SipSession.getActiveIncoming/OutgoingInvites? I can go both ways but
just wanted to ask. I think consistency is super important in an API.
However, from a simplicity point of view I have some other concerns
about these every specific methods...

I like the idea of having SipSession.getActiveIncoming/OutgoingInvites

Also, we often returns Collection but sometimes pass in Set. If the
intent is indeed to e.g. not allow duplicates then sure, use a Set but
then I would ask if that really matters for the proposed changes? So
is the useage of Set deliberate?

Yes createContinuationRequest could take a Collection.

And finally, in 289 Iterators are what is typically returned so if
nothing else the return values from these new proposals should
probably do the same (even though there are some inconsistencies in
289 as well – SipApplicationSession.getTimers() e.g.) .

But Collections are more useful - I would prefer utility over consistency. We can find out what others think.

=== Simplicity ===

In general, we should certainly make the life of the developers easy
but I don't always think creating a bunch of different very special
purpose methods will actually help. If we end up creating methods such
as SipFactory.createContinuationRequest then I believe that the API is
broken as it is and patching it is only going to make developers more

--- CreateContinuationRequest ---

So, createContinuationRequest, apart from making that particular use
case just slightly easier, is it a good idea? Perhaps the routing
directive should be added to the SipFactory.createRequest methods
instead? If we decide to keep the createContinuationRequest, why not a
createReverseRequest too?

I guess I personally do not like the createContinuationRequest because
for consistency sake we should then also add all the other
possibilities but the API becomes really cluttered, which is even
worse. So, I'm voting for not including this method and if really
needed enhance the SipFactory.createRequest ones instead, which I
believe is also what Binod suggested.

I included createContinuationRequest as a lightweight version of the B2BuaHelper.createRequest() methods which may be deprecated. You are right we could just remove it.

If a B2B application is sequenced in by a remote container that used ROUTE-BACK it should copy route headers. If the same app is to work well with a local app router it should use the CONTINUE directive. I was thinking that there may be some merit in doing both in the same method but not much would be lost by removing the method and having these two actions performed separately.

(I note that it is quite cumbersome to copy route headers in the correct order so a pushRoutes() method might be helpful for creating B2B apps).

Also, on a separate note, the javadoc isn't super clear what the
directive is for the newly created request. I assume is is NEW, which
makes sense but the only reference I have found regarding this is the
javadoc on SipServletRequest.setRoutingDirective, which is referring
to the deprecated SipFactory.createRequest. Perhaps we should improve
the javadoc here...

(side note2: for a beautiful API that gets stuff done, check out the
Python Requests API (though http is way simpler protocol but this API
is what I try and strive for)

--- SipInviteRequest.getUnacknowledgedProvisionalResponse ---

Why do we need to pass in the SipSession? If we do, it seems like this
method should be on the SipSession as opposed to the request. Since it
is on the request, I would assume this method would only return
responses for this particular transaction, correct? And if so, the
SipSession is not needed since the request you are operating on
explicitly is associated with a SipSession, or perhaps I'm missing

Version 2 of my proposal did have this method on the SipSession. I realised a problem with that as explained in the email that accompanied version 3.

The rseq value in a reliable provisional is only unique for that dialog. Due to forking there can be several dialogs which return provisional responses. In order to locate a specific response at a UAC which is downstream of a forking proxy we need to pass the session (or derived session) along with the rseq to the method on SipInviteRequest.

If we put the method on the SipSession there is still a problem with the uniqueness of the rseq value. PRACK can arrive after the corresponding ACK by which time a new INVITE transaction can be in progress which also has provisional responses. To retrieve the correct response we would need to pass it the requestId of the INVITE transaction as well as the rseq.

It seems best to avoid cluttering the SipSession interface with methods such as this one.

--- SipSession.getActiveInvites ---

What about getActiveXXX? i.e., what about all the other methods?

Only INVITE transactions require an ACK, other transactions are complete once the final response is sent/received. Similarly only INVITES can have reliable provisional responses.

On Fri, May 31, 2013 at 6:48 AM, Lewis, Keith < " target="_blank"> > wrote:
> I attach a new version of the transaction proposal.
> It addresses some issues I noticed with the previous version.
> There are some changes to the method names and a reduction in the number of
> methods which may address some of the comments from the last meeting.
> Here are the main changes
> For reliable provisional responses I now use the term "unacknowledged"
> rather than pending in the method names and description.
> I realised that there can be more than one invite transaction within a
> dialog which has unacknowledged provisional responses. This means that
> when retrieving a provisional response we need to use a combination of the
> invite request, the session and the rseq. This could have been achieved by
> adding the invite as a parameter to a method on the session. It seemed more
> natural to put the method on the request and pass the session and rseq as
> parameters. Since the method only applies to invite requests I am proposing
> that we create a new interface - SipInviteRequest -  which extends
> SipServletRequest.
> The section on linking has been updated to reflect the fact the we need to
> store a reference to the invite as well as the rseq when linking provisional
> responses.
> I moved the method for accessing final responses to the new interface and
> renamed it from getPendingInviteResponse to getFinalResponse.
> I combined the two getPendingRequest methods on SipSession into one method
> which returns a map and simplified the definition of pending. I added a
> UAMode parameter to select just incoming or outgoing requests - this seemed
> more useful than mixing both in the same map and reflects which is done in
> the B2buaHelper.getPendingMessages method.
> I added a new method SipSession.getActiveInvites which returns a map of
> SipInviteRequests.
> I split the createInviteResponseForDerivedSession method into 2 separate
> methods - createDerivedSession and SipInviteRequest.createResponse - this
> addresses the concern with the complex name. It also allows additional
> responses to be sent on a derived session thus allowing some useful B2B
> behaviour missing from the existing B2BuaHelper.
> Keith
> On Tue, May 14, 2013 at 5:11 PM, Lewis, Keith < " target="_blank"> > wrote:
>> Binod,
>> Thanks for the feedback.
>> Some comments inline below.
>> Keith
>> On Fri, May 10, 2013 at 8:58 AM, Binod < " target="_blank"> > wrote:
>>> Hi Keith,
>>> Here are some comments on this document.
>>> - In general, we should try to keep the methods as generic as possible.
>>>   We do not need to save developer writing one extra line of code for
>>>   "a particular case" at the cost of introducing a "special purpose"
>>> method.
>>> - SipFactory.createContinuationRequest :
>>>   I would instead have a createRequest(originalrequest, from, to,
>>> Set<String> excludeList)
>>> - For the pendingxxx methods, there is conflict between pending state and
>>>   Implicit transaction state defined in JSR 289. While it may be
>>> difficult to
>>>   now change the behavior of implicit transaction state, we should not
>>> try to
>>>   ignore that completely.
>> The aim in providing these methods is to reduce the need for applications
>> to store messages. In defining the meaning of "pending" we are saying when
>> the container can stop holding a reference to the message. We are not
>> defining when the transaction is complete. I think the fact that we have now
>> removed references to transactions from the names of the methods will help
>> avoid confusion.
>>> - There is no alternative to current b2buahelper.getPendingMessages
>>> method.
>> This is deliberate. Developers who are happy with this method can continue
>> to use the B2BuaHelper. The fact that this method is cumbersome to use was
>> the main motivating factor for us suggesting a new API.
>>> - How about defining the pending messages as a readonly collection? And
>>> retrieve
>>>   that collection from session? For example, we can define a interface
>>>   called Session.PendingMessageCollection that extend the java
>>> collection.
>>>   By default, this interface can act as the collection of uncommitted
>>> messages.
>>>   The additional usecases like getting pending invites and getting
>>> reliable provisional
>>>   responses etc can be added as extra methods to this interface.
>>> - If an invite gets a reliable provisional response and involves prack,
>>> does the
>>>   invite remain pending until ack for invite 2xx, right?
>> Yes
>>> - Why do we need createInviteResponseForDerivedSession? The name sounds
>>> quite odd to
>>>   me. Application can always do getPendingInvite() and then create a
>>> response, right?
>> Previously I named it the same as the equivalent method on the B2BuaHelper
>> - createResponseToOriginalRequest -  but it was suggested that it should
>> have a new name. This is my attempt. The method is special in that it
>> creates a new (derived) session for a forked response so the name is meant
>> to indicate this.
>>> - SipServletRequest.getRequestId -> SipServletRequest.getId()
>>> - I would try not to use sip method names directly in the api. So,
>>> instead of getPendingInvite,
>>>   may be PendingMessageCollection.getRequest(String methodName) might be
>>> better?
>> Chapter 17 of RFC3261 distinguishes INVITE transactions and explains the
>> special processing they receive. Since the method returns the initial
>> request of an INVITE transaction it seems OK to name the method
>> getPendingInvite(). We have the method getPendingRequest(String requestId)
>> which can be used more generally for both INVITE and non-INVITE requests.
>>> thanks,
>>> Binod.
>>> On Wednesday 08 May 2013 09:03 PM, Lewis, Keith wrote:
>>> Here is an updated version of the B2B and transaction API.
>>> Most of the changes are those suggested by the group.
>>> Keith Lewis
>>> On Fri, Mar 22, 2013 at 6:03 PM, Lewis, Keith < " target="_blank"> >
>>> wrote:
>>>> Hi all,
>>>> Here is the thrupoint proposal for B2B changes.
>>>> Keith

Tom Strickland, Software Developer, Thrupoint Software. Tel: +44 (0) 2920 005110
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Re: B2B proposal

Jonas Borjesson 06/12/2013

Re: B2B proposal

Binod 06/13/2013

Message not available

Message not available

Fwd: B2B proposal

Strickland, Tom 06/13/2013

Re: B2B proposal

Jonas Borjesson 06/13/2013

Re: B2B proposal

Strickland, Tom 06/14/2013

Re: B2B proposal

Binod 06/14/2013

Re: B2B proposal

Strickland, Tom 06/14/2013

Re: B2B proposal

Binod 06/17/2013

Re: B2B proposal

Nitzan Nissim 06/17/2013

Re: B2B proposal

Strickland, Tom 06/17/2013

Re: B2B proposal

Jonas Borjesson 06/14/2013

Re: B2B proposal

Lewis, Keith 06/15/2013
Please Confirm