FWIW, Concerning MLPP's application to packet networks, the following two I-Ds are currently proposed in IETF SIP WG:
Title: SIP Precedence mapping to MLPP Interworking http://search.ietf.org/internet-drafts/draft-polk-sip-mlpp-mapping-01.txt abstract: This document describes an extension to the Session Initiation Protocol [1] to allow SIP (and IP) into existing Voice Backbone Infrastructures that require Multi-Level Precedence and Preemption [2] Service throughout those networks. This document will also allow MLPP networks that are ISDN-based now to evolve/ migrate or be replaced by a SIP-based Voice Signaling network with no loss in capability of that original network. More likely is the case that additional functionality and capabilities can be realized such as mobility and reduced user headaches (explained later) with SIP being MLPP enabled within a network infrastructure.
Title: Multi-Level Precedence and Preemption over IP draft-polk-mlpp-over-ip-00.txt Summary abstract: This document describes how the ANSI specification T1.619- 1992[1] and its extension T1.619a-1994 [2] should be mapped or correlated or migrated over to either a mixed TDM and IP network (with Gateways in between) or a pure IP network that requires the functionality of these two specs as Standard Operating Procedure.
At 03:35 AM 4/19/2001, Horvath Ernst wrote:
Roy,
as you say, call priority and QoS are different issues, but over a packet network both come down to the same problem, expedited transport of packets with minimal packet loss. So the mechanisms used in both cases may well be the same.
The ISDN MLPP service is very complex and would be over-kill in a packet network which should not run into the same blocking situations as a circuit switched network. The complexity of MLPP was also the reason why ISO did not adopt it for QSIG (QSIG has a simpler call priority service called CPI, call priority interruption).
Regards, Ernst Horvath Siemens AG
-----Ursprüngliche Nachricht----- Von: Roy, Radhika R, ALCOO [mailto:rrroy@ATT.COM] Gesendet am: Mittwoch, 18. April 2001 21:30 An: ITU-SG16@mailbag.cps.INTEL.COM Betreff: Re: Emergency Services and Service classes
Hi, Tom:
Good that MLPP was discussed in the last Rap. meeting.
One suggestion comes to my mind that we can define "Priority" field in such a way keeping options for all kinds of priority (civilian, interworking with ISDN, etc.) levels and let people choose as it is needed.
Best regards, Radhika R. Roy AT&T
-----Original Message----- From: Tom-PT Taylor [mailto:taylor@nortelnetworks.com] Sent: Wednesday, April 18, 2001 3:16 PM To: Roy, Radhika R, ALCOO; ITU-SG16@MAILBAG.INTEL.COM Subject: RE: Emergency Services and Service classes
I just wanted to note that MLPP came up in the Launceston discussion. The point was made at that time that MLPP (the M stands for "Military") is a separate issue, since what Gary and company are talking about is civilian emergency services.
Beyond that, we are committed to working with other Study Groups on this issue.
-----Original Message----- From: Roy, Radhika R, ALCOO [ mailto:rrroy@ATT.COM
Sent: Wednesday, April 18, 2001 1:34 PM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: Emergency Services and Service classes
Hi, Tom and All:
I have few comments on: 1. Priority Class, 2. Quality/QOS Class, and 3. Dependency between Priority and Quality
- Priority Class of a Call
Let us define priority classes for a call across all ITU SGs (not ONLY in SG16). If the SG16 is allowed to do define the priority class that will be followed by other SGs, we may then define this in this SG
and will be
sending liaison to other SGs (because the emergency services standard works span multiple SGs.
In addition, there are other areas that we need to look into. For example, the present ISDN standard also defines MLPP where several kinds of priority are offered. (Recently, contributions have also been presented to define priority is SIP in accordance to the MLPP.)
- Quality/QOS Class of a Call
To define quality of a call is being undertaken in Q.F/16. It will take time to define QOS classes or anything like this in Q.F because the definitions of QOS provided in various cases (e.g., SG 13 [Q.4], BICC, TIPHON, IETF, etc) are problematic at the application layer because they are often tied to the network layer. Suggestions are also there whether best, high, medium, or best-effort will mean anything unless we call guaranteed, controlled, or best-effort.
The point is that let us continue the discussion of quality in Q.F/16 so that we agree on this.
By the way, in Q.F/16, we are considering the quality at the medium level as opposed the per call level. (At one point, we found that classes are becoming problematic. So, we have started to use a matrix where a user will define how each medium will be treated - a kind of
preferences [e.g.,
guaranteed, controlled, or best-effort] without defining explicit classes.)
- Dependency between Priority and Quality
I do not clearly whether there will be any dependency between the priority and quality of a call.
Hope this helps.
Best regards, Radhika R. Roy AT&T
-----Original Message----- From: Gary Thom [ mailto:gthom@delta-info.com
Sent: Wednesday, April 18, 2001 12:41 PM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Emergency Services and Service classes
I would like to re-open the discussion started at the Nov
2000 Geneva
meeting and continued at the March 2001 Launceston meeting
relating to
Emergency Services.
In order to support Emergency Services, there are three services that are desired: 1)Priority Dial Tone - this is a line or endpoint dedicated to emergency calls. 2)Priority Call Setup - this allows an emegency call to be made from any endpoint. 3)Priority Call transit through packet network - this requires interworking existing ISUP high probability of completion call marking with H.323, H.323 Annex M.2, h.246 Annex C, and H.248.
An emergency call may be pre-emptive or may just improve the probability of call completion without pre-emption depending on national policy. Authentication issues also need to be worked out. Currently, in the US, this is handled like a calling card authentication.
At the Geneva meeting, it was decided that this work was closely related to contribution D.4 from Cicso on reserving resources and also Annex N/H.323 on QOS. Also included were liaison statements from SG11 on QOS for BICC, and an ETSI TIPHON document on signaling end-to-end-qos.
All of these items require a method of signaling the desired quality of service. One way of doing this that seems to be common to all requirements is to specify a Service Class parameter and to send this parameter in the various RAS and Call Signaling exchanges.
I would like to propose the following Service Class parameter.
ServiceClass ::= SEQUENCE { priority CHOICE { emergency, high, normal, low } quality CHOICE ;per TIPHON definition { best, high, medium, bestEffort } }
The priority field is used to indicate the importance of the call. This is used not only for assuring that resources can be allocated, but also to improve the probability of completion of the call.
The quality field is taken from the ETSI TIPHON QOS Class definitions, and relate to bitrate, codec type, and voice or video quality.
High or emergency priority calls may not require best audio quality, medium may be sufficient (even prefered because of the lower bandwidth requirement), while normal priority calls may desire high or best audio quality.
The Service Class parameter would then be added to the necessary RAS and Call Signalling messages. At a minimum this would include the ARQ and Setup messages, but might also be applied to others.
It is necessary in the ARQ and Setup messages so that High Probability of Completion calls comming into the network from the PSTN can be given priority treatment.
For priority dial tone, perhaps the Service Class should be included in the RRQ to indicate the desired priority, once authenticated by the Gatekeeper and confirmed in the RCF, this endpoint could then include that Service Class in subsequent ARQ and Setup messages. Is a token required from the Gatekeeper to indicate that the endpoint has been granted priority status????
For priority call completion, an authentication authority and procedure needs to be defined. One approach is for the call to be made to an access number, the user is then queried for a PIN and the called endpoint number. After authentication, the call would be transfered to the called endpoint. The transfered call would be placed using the Service Class provided by the athentication authority. This would be the same procedure for any calling card call made on the packet network. The Service Class would be based on teh service level agreement between the card user and the provider. In the case of an emergency caller, the SLA would indicate Emergency Priority. How are calling card calls handled on packet networks now???? Is this consistent???
I would appreciate any input that you could provide.
Gary
Name : Gary A. Thom Company: Delta Information Systems, Inc. Address: 300 Welsh Rd., Bldg 3 Horsham, PA 19044 USA Phone : +1-215-657-5270 x123 Fax : +1-215-657-5273 E-mail : gthom@delta-info.com Website: www.delta-info.com
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