Roy,
Let me summaries my position, then we can talk next week.
1. I agree that H.323 is (mostly) transport independent. I also want the transport to be application independent. Another words, I do not want to tell the service provider that I am sending voice or any other media. I only want to tell the service provider that I need a given QoS for the data stream.
2. I agree that the QoS needs depend on the needs of a given data stream. It would be good if this can be specified. However, the means to specify this should be independent of the transported data (voice).
3. We definitely need a means to specify the end-to-end QoS on a demand basis. I would think that the originating service provider should be able to receive this and forward it to subsequent service providers based on the available and selected route.
4. I agree that the means used to specify the desired QoS should be independent of the transport layer. It should also be independent of the application.
5. Yes, our work is limited to H.323. This limits our ability to create a general solution. On the other hand, if we consider H.323 QoS transport to be a value added service, then the service providers can change a special value added service charge for H.323 transport. A general solution is an advantage to the H.323 solutions in that the QoS service charge is a general change and not specific to H.323. (Sorry, for some people this is heresy.)
Maybe there is a balance between your method of specifying in detail the desired QoS and the fact that it is H.323 specific.
Bob
------------------------------------------------------------------ Robert Callaghan Siemens Enterprise Networks Tel: +1.561.923.1756 Fax: +1.561.923.1403 Email: Robert.Callaghan@ICN.Siemens.com ------------------------------------------------------------------
-----Original Message----- From: Roy, Radhika R, ALCOO [mailto:rrroy@ATT.COM] Sent: Monday, August 14, 2000 11:29 AM To: ITU-SG16@mailbag.cps.intel.com Subject: Re: H.323 QOS
Hi, Bob:
I have provide my reply embedded in your email [RRR].
In addition, I am providing some general explanation.
The fundamental problem is that the network layer QOS signaling schemes are different because these are transport dependent. In olden days, we have also made application specific to the particular transport mechanism. For example, H.320, H.321, etc.
However, the application like H.323 has changed the landscape. It is transport independent although it can be sent over any transport network specific to meets its specific needs. For example, we change the abstraction of network address into IP, ATM, etc. as needed. So, this simple example shows how H.323 is transported in a specific network while the "network address" is the universal abstraction for both IP and ATM.
If people want to solve having the service level agreement in a specific way without using any standards, it is their choice. In fact, many service providers are doing this in a proprietary manner toady. There is no common standard to express the QOS in a universal way that remains the same on end-to-end basis and there are so many translations in the network layer without having a common reference. As I explained above, if we want to make H.323 IP specific, we could do this as well. In this case, we do NOT need to make it transport independent. But the question is: Why did we make H.323 transport independent?
We have discussed this a lot in the past while we have been developing Annex H.323 N, and have come to the same conclusion that we do need to make H.323 QOS transport independent so that it can be implemented for any network or a combination of networks or a combination of network layer QOS.
It also bridges the fundamental gap that the application (audio codecs, video codecs, data) has its own intrinsic needs to express its QOS because it is the application whose needs to be satisfied no matter what the underlying transport network or networks may be. The beauty of H.245 is that it provides a negotiation capability on end-to-end basis and the same can also used for QOS (in fact, it is also used to day for RSVP, and ATM QOS in a monolithic network).
The beauty of H.323 QOS Annex N is that it helps to implement all heterogeneous network layer QOS (RSVP, DiffServ, MPLS, ATM QOS, etc) in any combination that people may like to implement.
Hope this will clarify your points further.
Best regards, Radhika R. Roy AT&T
-----Original Message----- From: Callaghan, Robert [mailto:Robert.Callaghan@ICN.SIEMENS.COM] Sent: Monday, August 14, 2000 10:17 AM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: H.323 QOS
Roy,
I have two points:
1) For me, it is the responsibility of my service provider to provide the service agreed to in my service level agreement. This may require the existence of service level agreements between service providers; so be it. This should not be my problem. [RRR] Yes, that is why a service provider needs to have a common set of H.323 QOS that remains the same on end-to-end basis so that H.323 services can be provided transparently. My primary reference point is H.323 service providers, not transport network service providers. A transport network service provider may or may not need H.323 QOS. If a transport service provider may also use H.323 QOS a common basis for mapping among RSVP, DiffServ, MPLS, and ATM QOS at the network layer if they think that H.323 QOS is a good reference based on "standard." Please note that a service provider may have IP, ATM, and/or other networks to provide H.323 services. So, H.323 QOS will provide to have a common basis for translation in this heterogeneous networking environment.
2) The interface needed to obtain a given service level should be independent of the application, even when multi-service providers are involved on an end-to-end basis. That is, the interface should work for any application. Therefore there should not be any H.323 specific signaling required to obtain the requested QOS. [RRR] We are wearing the "Hat" of H.323. That is, we are NOT talking about only IP, ATM, etc. We are dealing with the H.323 application and the services related to H.323. So, H.323 QOS needs to be translated as needed in the transport layer.
3) The interface required to signal RSVP, DiffServ, MPLS, ATM QOS, etc. are all different. This is recognized today in H.245 in that RSVP and ATM QOS are handled differently. H.245 should be extended to handle all variant of QOS based on the needs of the individual specifications. [RRR] Yes, it is all different QOS in the network layer, but the H.323 application is "only one" and remains the same on end-to-end basis, and its QOS needs (what we call H.323 QOS end-to-end) is also the same and does not change not matter whether the network supports RSVP, DiffServ, MPLS, and/or ATM QOS. This is the problem that we have solved in H.323 QOS (you can see appendix of H.323 Annex N). If you go through appendix of H.323 Annex N, you can easily see how this problem has been solved. Please go through this annex N, ask me or others who worked for this annex specific questions if you have any.
Bob
------------------------------------------------------------------ Robert Callaghan Siemens Enterprise Networks Tel: +1.561.923.1756 Fax: +1.561.923.1403 Email: Robert.Callaghan@ICN.Siemens.com ------------------------------------------------------------------
-----Original Message----- From: Roy, Radhika R, ALCOO [mailto:rrroy@ATT.COM] Sent: Monday, August 14, 2000 9:37 AM To: ITU-SG16@mailbag.cps.intel.com Subject: Re: H.323 QOS
Hi, Bob:
I agree completely agree with you.
In fact, we are all trying to achieve the same goal. For example, H.323 does supports QOS today via H.245. You can easily see that RSVP and ATM QOS are supported using H.245. The beauty of this approach is that H.245 is still transport independent. All we have done here is: the abstraction of H.245 has been used to support the RSVP and ATM QOS to implement the network layer QOS. However, this is only good for the single network. For example, end-to-end RSVP or end-to-end ATM QOS.
If there are multiple networks or if a single IP network implements RSVP in one domain, DiffServ in another domain, and MPLS in another domain, there is no transparent H.323 QOS signaling mechanism that is universal on end-to-end basis so that it can be mapped over the RSVP, DiffServ, MPLS, ATM QOS, etc transparently.
In Appendix of H.323 Annex N, we have done the same. We have the abstraction of H.323 QOS in the application layer. We have shown how the H.323 QOS can be mapped over the RSVP, DiffServ, ATM QOS, etc. if needed. It also provides the backward compatibility with the existing H.323 standard. However, we have done only for the pre-call setup signaling part. We have not done the call setup part yet. In the call setup part, we will include H.245 in a similar way what H.323 is supporting RSVP and ATM QOS today in a monolithic network.
I appreciate your email.
Best regards, Radhika R. Roy AT&T
-----Original Message----- From: Callaghan, Robert [SMTP:Robert.Callaghan@icn.siemens.com] Sent: Monday, August 14, 2000 9:08 AM To: Roy, Radhika R, ALCOO Cc: 'Mailing list for parties associated with ITU-T Study Group 16' Subject: RE: H.323 QOS
Roy,
In my view, the network, as a minimum, needs only provide transport. H.323 is an application using this transport and is not different from any other application being transported. Any application may request a desired quality of service that the network may grant based on policies, service level agreements, and availability. Each data connection used by an application may request a different QOS. Most likely H.323 is such an application as needing an enhanced QOS. This simple case should work. This is all that is required.
In addition to transport, the network may optionally provide other additional services. These services may include application layer routing. These optional services should be configured and indicated independently from the basic transport QOS.
It is correct that H.323, as an application, is (mostly) transport independent. However, the interface between the application and the transport layer is not transport independent. The interface specification used to request a given QOS is totally dependant on the standards body that specified the transport layer; and for this there has been little or no coordination.
Because transport QOS over IP is based on IETF specifications, it is necessary that the interface used to request a given QOS conform to the appropriate IETF specification. If such an interface specification is not available, that input might be provided to the appropriate IETF body as to the requirements.
I can see the endpoints negotiating the desired QOS base on need, price, and other considerations. For me, this is the limit to the application layer involvement in QOS negotiation. At this point, the application negotiations with the transport provider as to the desired and available QOS. It is up to the transport provider to arrange for the end-to-end QOS. (Again, it is not necessary for the transport network to know that H.323 is involved in the transported data. In fact it may be encrypted in order to mask the presence of voice transport.)
For me, this is simple.
Bob
Robert Callaghan Siemens Enterprise Networks Tel: +1.561.923.1756 Fax: +1.561.923.1403 Email: Robert.Callaghan@ICN.Siemens.com
-----Original Message----- From: Roy, Radhika R, ALCOO [mailto:rrroy@ATT.COM] Sent: Friday, August 11, 2000 7:59 AM To: ITU-SG16@mailbag.cps.intel.com Subject: Re: H.323 QOS
Hi, Mike:
Let me try again.
What is the reference point of H.323 QOS? Is it not H.323? If it is so, what do we mean by H.323?
The answer is: Audio (different codecs), Video (different codecs), and Data (T.120 applications) that are used by H.323.
What are the QOS/performance characteristics of audio, video, and data from the application point of view that is generated by audio codecs, video codecs, and data (T.120) applications?
These QOS/performance characteristics come from the SOURCE codecs and data applications. Per transport independent H.323 specifications, an enduser express their QOS/performance requirements on end-to-end basis purely from application point of view irrespective of the transport network (e.g., IP, ATM, etc.).
Moreover, H.323 is meant for the packet network, not for any circuit-switched network like PSTN or ISDN.
Let us NOT go beyond this before we start debating transport layer QOS or service provider requirements. These are NOT the concern of H.323. H.323 is the transport independent application.
H.323v2/v3/v4 has also provided mechanisms how RSVP and ATM QOS can be used for H.323 audio, video, and data. So, H.323 QOS that will be defined in H.323 Annex N MUST provide mapping for the backward compatibility. It is a requirement that MUST be met per the norm of ITU-T.
So, what is left for mapping? Mapping is simply a by-product of the above requirement. Mapping is simply a table, nothing else.
Did I miss anything?
Best regards, Radhika R. Roy AT&T
-----Original Message----- From: Mike Buckley [mailto:mikebuckley@44COMMS.COM] Sent: Thursday, August 10, 2000 10:19 PM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: H.323 QOS
Radhika,
Thanks for the input which I welcome as I will unfortunately not be present at Portland.
Let me ask a few questions and make a few comments hopefully with the intent of opening up the debate.
- I am not sure I understand your concept of a mapping table between the
H.323 QOS and the transport layer QoS. My understanding is that QoS is on three levels:
a) that specified from a service point of view between the user and service provider (e.g PSTN quality, conference quality etc) This is the domain of the speech experts and can be characterised by Listener Speech Quaklity (MOS), end to end delay, and absolute category rating, R.
b) application specific parameters, (e.g. equipment delays, codec choice and performance, codec frame size, packetisation arrangements, jitter buffer design, overall packet loss etc.) Optimisation of all these will determine what can be delivered in a).
c) transport parameters for a given choice of application parameters. This boils down only to three parameters as far as I cna see: tranport network delay, packet delay variation in the transport network and packet loss in the transport network. Again these parameters will determine the results in a) for a given choice of the parameters in b). These parameters are generic from the perspective of the transport network. i.e the transport network does not need to know the details of the application.
So the sequence of cause and effect and control is:
a) User requests QoS class from service provider, b) Service provider determines application specific parameters in conjunction with users equipment and other service providers, c) Service provider requests required delay, delay variation and packet loss from network provider.
I see no need for mapping here. The only QoS info flows within the application are specific to the application and those between the application (service provider) and the transport network are generic. i.e. delay, jitter and packet loss. Have I missed something?
- The issue of bit rate and media stream statistics I think need to be
decoupled from QoS. These are specified to enable optimisation of resources within the transport network. They have no QoS significance from an application point of view. i.e the apllication does not care about the media stream bit rate and statistics but the transport network provider does as it eats up his resource. They may be used for policy enforcement however in the transport network so they do need to be agreed between service provider and network operator. i.e the network operator agrees to provide a given QoS level (delay, jitter, packet loss) provided the media properties are within an agreed profile (bit rate, flow statistics).
- The next point is how can the service provider know the statistics of
a particular VBR stream? These can only be specified over a large number of similar calls and will depend, for instance, on who is speaking, the nature of the speech interaction etc etc. They can only be measured not calculated. The service provider is in no better position to measure these than the transport network operator and, in fact, where no gateways are involved, may not be able to. On the other hand the class of signal would have to be signalled to the network operator for him to be able to distinguish which class a particular measurement belonged to. e.g voice/speech/data, codec type, conference, multicast etc. So I see no purpose in trying to exchange statistics between the service provider (application) and transport operator. I think peak bit rate is all that can be meaningfully excanged. The specification of media class is however perhaps worth exploring.
- The controlled category has always puzzled me. I only see two
possibilities. Either the requested QoS level is guaranteed (on a statistical basis e.g 95% of all connections over a specified period) or not guaranteed. Is your controlled category a way of saying guaranteed, not to 95% but to some lower figure? If you can't put a percentage on it then it seems it is plain and simple not guaranteed. Anything that is not guaranteed to some specified statistical level is best effort and you can't say anything more about it. So I only see two categories here.
In summary, I think we need to do three things in Annex N.
a) Figure out the QoS information to be exchanged within the Application between service providers and end users. This will go in H.225.0 and H.245.
b) Figure out how we are going to signal QoS and media information between the application (service providers) and transport domains (IP or ATM networks etc). The info is basically delay, jitter, packet loss requirements and peak bit rate. We need a protocol for this.
c) we need to work out the interactions between the application QoS signal flows and the application/transport signal flows. I don't think we need worry about how the transport network mechanisms assure the requested QoS paramerters. RSVP/Intserv, Diffserv, MPLS, ATM, over provisioning are all possibilities.
Would welcome comments and views on the above.
Mike
Mike Buckley +44-1457-877718 (T) +44-1457-877721 (F) mikebuckley@44comms.com
----- Original Message ----- From: "Roy, Radhika R, ALCOO" rrroy@ATT.COM To: ITU-SG16@MAILBAG.INTEL.COM Sent: Thursday, August 10, 2000 10:15 PM Subject: H.323 QOS
Hi, Mike and All:
It is time to discuss about H.323 QOS.
I believe that we have an agreement as follows:
· H.323 QOS MUST be backward compatible to support RSVP and ATM QOS as it exists for H.323v2/v3/v4 · Like H.323 spec, the application level H.323 QOS MUST be independent of the transport layer QOS and should support all transport networks (e.g., IP, ATM) · A mapping table between the H.323 QOS and the transport layer QOS (e.g., IP QOS [DiffServ, RSVP, etc.], ATM QOS [CBR, rt-VBR, nrt-VBR, ABR, etc.]) should be provided.
From the H.323 multimedia application point of view, there are following performance parameters can be used to characterize the traffic characteristics:
· Bitrate characteristics: Peak bit rate (PBR) or peak rate (PR), Sustained bit rate (SBR) or average rate (AR), minimum bit rate (MBR) or minimum rate (MR), and mean bust size (MBS) · Delay and loss characteristics: end-to-end delay (EED) or delay, end-to-end delay variation (EEDV) or delay variation (DV), and bit-error-rate (BER) or (packet) loss rate (LR)
We can now form a table with all parameters as follows:
Table 1: H.323 Multimedia Application Performance Matrix Audio (codecs)--- Video (codecs)--- Data (T.120) PBR/PR Yes/No/Value Yes/No/Value Yes/No/value SBR/AR Yes/No/Value Yes/No/Value Yes/No/value MBR/MR Yes/No/Value Yes/No/Value Yes/No/value MBS Yes/No/Value Yes/No/Value Yes/No/value EED/Delay Yes/No/Value Yes/No/Value Yes/No/value EEDV/DV Yes/No/Value Yes/No/Value Yes/No/value BER/LR Yes/No/Value Yes/No/Value Yes/No/value
From the above table we will have the opportunity to choose each parameter for each medium (audio, video, data) that makes sense from the application's and enduser's point of view. Again, these parameters can be specified as follows:
· Guaranteed: The value specified for each parameter MUST be guaranteed. · Controlled: The value specified for each parameter MAY be satisfied as far as practicable (possibly with certain range), but definitely NOT guaranteed. · Best effort: No commitment will be made.
Now each medium (e.g., audio, video, or data) will have different categories of performance matrix depending on its selection criteria and this can also be mapped to RSVP, ATM QOS, and others, if needed.
Once we agree on this format, the next step is to create H.323 QOS signaling messages.
This is my input for discussion in the upcoming Portland Q.13 meeting for H.323 QOS.
I like to see the comments from other members as well.
Best regards, Radhika R. Roy AT&T +1 732 420 1580 rrroy@att.com
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