Hello guys,
So, the day has come to define and describe our first service !
This post may well be considered as the Stage-1 service description of our first service. This is in line with the project objectives outlined here:
http://whitelassiblog.wordpress.com/2008/09/29/service-design-processes-and-lifecycle-at-whitelassi/
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This blog post will be divided into the following sections:
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1) Motivation behind this service and Stage-1 service description.
2) Service terminology and definitions.
3) Standards reference (domain knowledge)
4) Forward Path.
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1) Motivation behind this service and Stage-1 service description.
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The IP Multimedia Subsystem (IMS) mandates device independence. Moreover, IMS allows a single public identity of a device to be shared amongst multiple physical devices. Each physical device in IMS is identified uniquely by an IMS Private User Identity (IMPI). Each IMPI may have multiple IMS public user identities (IMPUs).
With the advent of IMS, there will be a need for a device management framework.
A single human user may own several devices. He may use different devices for different purposes. He may give an IMS device to his children to carry with them etc.
This would call for a management framework for managing the devices (personal network) for this user.
The user may want to impose certain parentel control mechanisms on the device that is given to the kids. A protective parent may want to screen all calls that are made to their kids, and define an access control list to control who may call and who may not call.
The user may want to specify which services should be rendered to which device, based on the device capabilities. The user may want to add/remove devices from his personal network. The user may even want to control other devices from a single device.
Because IMS is access independent, the nature of these devices can vary:
As for example, device 1 is a mobile handheld, device 2 is a set top box, device 3 is a desktop computer and so on. I may specify the mobile handheld as my personal network controller. This means, that all configurable changes to my personal network (add/delete/modify etc) will be performed using this ‘master’ device which is the controller for all other devices present in my personal network.
Using my mobile handheld as a controller, i can direct all multicast session requests to my set top box and all file transfer requests to my desktop.
The prospect of such an application server will is not limited to the telecom domain alone. Even non IMS devices will be able to define their personal network by means of a service management point (GUI) exposed by the PNM (Personal Network Management) application server.
From this discussion, it is now clear, that PNM as defined by 3GPP is a generic device management framework, where the devices may be of diverse forms and types. This project will implement the personal network management server in the context of the IP Multimedia Subsystem. Thus the PNM AS will be a SIP application server.
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2) Service terminology and definitions.
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For getting well versed with the definitions and other terminology pertaining to IMS and PNM, there is a reference list given below:
a) User Equipment (UE):
The user equipment is a physical device that is at the customer premisis. This physical device may be a mobile handheld, a laptop, a desktop or even a set top box.
b) IMS Private User Identity (IMPI):
The IMS Private User Identity is a unique device identifier which has a one-to-one relationship with a physical device. It is defined by the operator and is used for Authorization, Authentication and Accounting purposes in IMS. From the perspective of the PNM AS, an IMPI is a unique device identifier, belonging to a particular personal network of devices.
c) IMS Public User Identity (IMPU):
The IMPI defined above, can have multiple Public user identities associated with it. An IMS user, places calls using a public user identity. There is a one-to-many relationship between an IMPI and an IMPU. An IMPU can take two forms…either a SIP URI or a TEL URL number. There is a requirement for every IMPI to have atleast one IMPU associated with it.
An example of IMPUs—> sip: aayush@rancore.com
sip: aayush@192.168.128.30:5060
tel: +919987081573
d) Personal Network:
A personal network in the context of personal network management service is a user defined network of physical devices (indexed by an IMPI) that a human user has configured in the PNM application server. The human user can add/delete any number of physical devices as part of his personal network. A user may also temporarily define a ‘guest device’ to be part of his personal network for a specified period of time.
e) Personal Network Element (PNE):
This is the smallest unique element of a personal network. A Personal network is made up of multiple personal network elements. From the perspective of IMS, an IMS UE is a personal network element. In 3GPP, it is suggested that a PNE may consist of multiple devices, but this claim is not backed up by substance. In the context of this project, a PNE maps to a single User Equipment (UE). A UE is in turn indexed by an IMPI.
f) Personal Area Network(PAN):
The personal area network is defined as the home network of the user who has defined his personal network in the PNM AS. In the context of 3GPP IMS, the local network/home network of a user is the one where the user is registered. IMS users register with a node called S-CSCF (Serving Call Session Control Function). The S-CSCF is always located in the home network of the user. Thus, the PNM AS shall always be in the home network of the user, as it receives triggers from the S-CSCF, as will be discussed in the stage-3 discussion of call flows.
g) Personal Network User (PN User):
From the perspective of this service, the PN User is the human user who owns the network of his personal network, especially the personal network controller (PNC).
h) Personal Network Controller (PNC):
A PNC refers to the physical device that the human user uses to control other PNE’s of his personal network. The human user configures a single personal network controller through a service management point (GUI based SMP) at the PNM AS. The human user uses his PNC to exercise access control for other devices, by virtue of changing configurations using the SMP.
i) Personal Network Controlee (PNCE):
A PNCE refers to a device or a set of devices, that are being managed and controlled by the PNC. These can be a set of devices that the human user has configured through the SMP at the PNM AS.
j) Service Management Point (SMP):
This is a graphical User interface (GUI) exposed by the PNM AS, through a web based interface towards the devices. Only the personal network controller (PNC) can change access rules, device configurations and other management actions through the PNM SMP. The PNC can add or remove PNCE’s from the SMP.
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3) Standards reference (domain knowledge):
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The IMS standards are vast with a lot of details. Therefore, it is important to identify and outline only those parts of the standards that are relevant to this application server (PNM).
There are certain things that are clear to us now:
a) The PNM Application Server (PNM AS) is a SIP AS as defined by 3GPP TS 24.228 Section 4.2.4 till 4.2.4a. This section defines the ISC (IMS Service Control) reference point between an IMS SIP AS and the S-CSCF. It is a fact that all incoming SIP requests to the PNM AS (IMS AS) will come either from the ISC reference point (S-CSCF) or from the I-CSCF. The interface with the I-CSCF can be left as of now..and will be explained later.
b) Please download 3GPP TS 22.259 v9.0.0 from: http://www.3gpp.org/ftp/Specs/html-info/22259.htm
click on 9.0.0 version hyperlink..and the download will start.
c) Please download 3GPP TS 23.259 v8.1.0 from: http://www.3gpp.org/ftp/Specs/html-info/23259.htm
d) Please download 3GPP TS 24.259 v1.2.0 from: http://www.3gpp.org/ftp/Specs/html-info/24259.htm
Ponts b,c and d will be the core basis of our development.
Point ‘a’ defines and explains the concept of call routing on the ISC reference point. All SIP application servers..may it be PNM or any other server will interact with the IMS core network over the ISC reference point. The node with which we will interact will be the S-CSCF. Different routing scenarios are defined here.
e) RFC 3261: www.faqs.org/rfcs/rfc3261.html to get an idea of SIP. Sections 1-12 and 17 are most important.
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4) Forward Path
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A logical way forward will be to study the PNM standard links given above along with the 24.228 link. Then we can move to the Stage-2 service description. Also RFC 3261will give deep insight on SIP.
Dont forget to check out the Imp-links tab and SLEE tutorial tabs at the header of this blog ! These tabs specify the programming model that we will follow to implement all this domain knowledge !
If there are any doubts…..please leave me a comment here on the blog or on the mailing list: users@whitelassi.dev.java.net
or email me directly at abhatnagar192006@gmail.com
Best Regards
Aayush
