Subject: Re: Transport layer interface

From: Brian Rosen <[email-masked]>
Date: Thu, 26 Aug 1999 07:35:36 -0400

This is too easy:

1. E911 - 12 calls are queued in buffers, network is busy and a 911 call
comes through -- it is put at the head of the line

2. "Olympic" service.  Service provider offers a variety of plans, at
different costs.  Under congestion, Gold service customers get better
performance

3. 30 messages are queued, some of them "Adds", some subtracts.  A
message comes from the MG which is something that equates to "out of
DSP" resources.  Reorder the messages so subtracts are ahead of Adds.

The first one may turn out to be a requirement, and that may FORCE
ALF in EVERY implementation.  YMMV.

Brian

> -----Original Message-----
> From: John Segers [mailto:[email-masked]]
> Sent: Thursday, August 26, 1999 3:38 AM
> To: Brian Rosen
> Cc: [email-masked]
> Subject: Re: Transport layer interface
>
>
> All,
>
> I don't quite understand how ALF will be substantially better for
> congestion management than a layered approach.  I understand
> that if the
> the application has control over message buffers, it can
> reorder them.
> What I'm wondering is whether reordering/canceling MEGACO
> messages will
> lead to a sufficient reduction in traffic, in the presence of media
> streams on the same network.  Can someone give an example
> where it would
> help?
>
> John
> --
> John Segers                                  email: [email-masked]
> Lucent Technologies                                        Room HE 306
> Dept. Forward Looking Work                      phone: +31 35 687 4724
> P.O. Box 18, 1270 AA  Huizen                      fax: +31 35 687 5954
>

---

From: John Segers <[email-masked]>
Date: Thu, 26 Aug 1999 13:51:17 +0200

Brian,

See my comments below.

John

> comes through -- it is put at the head of the line

Will the ALF mechanism be able to guarantee that you can set up the 911
call?  There will, in all likelihood, be a lot of traffic that is not
under the control of the MGC (voice streams, data traffic).  ALF can
help give priorities to certain calls, but I don't think it can provide
guarantees.

> different costs.  Under congestion, Gold service customers get better

Again the question is whether you can guarantee that the premium service
subscribers get the service they pay for.  If you manage to the
signaling through for setting up a premium subscriber's call, how will
the voice quality be in the congested network?

It seems to me that provisioning the network and/or implementing QoS are
better ways to satisfy 1 and 2.

> DSP" resources.  Reorder the messages so subtracts are ahead of Adds.

If all 30 queued messages are destined for the same MG, then yes.  This
example suggests that you are talking about a big gateway.  Is that
likely to run out of DSP resources?

---

From: Christian Groves <[email-masked]>
Date: Thu, 26 Aug 1999 16:05:06 +1000

We don't have ALF today but we already do all of these requirements.

1. This is done at a Call Control, priorities are associated with calls
and its the call level that decides which calls proceed. In the US there
are services such as MLPP (mutli-level precedence and pre-emption) which
satisfy this. In some cases the call establishment will be queued, in
some cases the existing calls will be dropped. This is up to the
application to decide based on importance its not up to the transport to
decide.

2. The service differentiation is done at a call level. Its the
application that determines what is done. Under congestion the
application knows how important a customer is and will prioritise the
setting up of media streams. How this is done is dependent on your
particular application.

Both 1&2 are seperate from the actual transport. Whether you use
transport layering or ALF doesn't make a difference. I would say using a
layered approach gives flexibility because it allows different
applications to handle congestion etc in their own way. I believe this
was why ALF got support because it was stated 'applications know best'
but should it be one ALF for ALL applications? The transport and the
interface to it should be agnostic.

Cheers, Christian