Advantages and Disadvantages of Using Presence Service - TKK - TML

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Advantages and Disadvantages of Using Presence Service Arturo Salinas Helsinki University of Technology [email protected]

Abstract In this article we are going to study some advantages and disadvantages of using Presence Service. There are several applications that are using Presence Service nowadays and in the future new ones, not even envisaged, could use Presence Service. A good example of these applications is Push-totalk over Cellular (PoC) that is implemented in some phones for 2G and 3G networks. I describe the Presence architecture for PoC and others Presence architectures in different environments such as the Internet. In this way we can see how the idea of converging networks can empower the advantages of Presence service. Some user scenarios are analysed which present some advantages of Presence Service but that present several challeges that new technologies have to address. Finally, I will present some conclusions and ideas of how the disadvantages of Presence Service can be overcome. KEYWORDS:Presence Service, architecture, user scenarios, requirements, Push-to-talk over Cellular (PoC), Jabber

1 Introduction Presence service provides access to dynamic information about an entity that can be a user or an abstract one such as a computer service. This information is called Presence Information. A simple presence information is the “available/unavailable” state that we observe in the popular Instant Messaging Internet applications like: MSN Messenger or Yahoo Messenger. There are some variations in the definition of presence information over different environments. However, most of the definitions are based in the models of Presence and Instant Messaging defined for the Internet by the IETF. Actually, presence information has been available in its basic form for quite a long time. When somebody calls using any phone a different tone will be heard depending on whether the destination number is busy or unreachable and this information is a form of presence information. Nowadays the ability to send data through telephone networks enables richer and more instantaneous presence information. We are able to see if the person to whom we are calling is available even before we try to call her. Besides this, location and willingness can be provided by presence information. We can see some examples of applications that use Presence Service (PS) in the table 1. There can be a myriad of applications of Presence Service. Because the advantages and disadvantages of PS vary amongst these applications; some kind of classification could

Application that uses PS Telephone directory

Fixed and mobile telephone networks Internet instant messaging

News or weather alerts Printer status Voice mail consuming user presence information for redictering voice messages to email or mobile phone [1]

Presence Information

Characteristics

Phone number, address, offering a service (yellow pages)

Centralized-external control, offline availability, difficult to update, possibly outdated and inexact Almost immediately available for user demand (user has to call first) Immediately available, user control

Tone of “Busy” and “Disconnected” Available/Unavailable (willingness), busy, away, on the phone, location information, what song the user is listening now (MSN Messenger) Breaking news, changes in the local weather Offline/Online, run of paper User availability, available media of communication

Immediately available, user control Immediately available, user control Immediately available, user control

Table 1: Some applications that use Presence Service (PS)

be necesssary. In [2] there is a classification of Presence applications: • Presence-enabled applications: They require Presence Information for working properly. For example: PoC or Instant Messaging Service. • Presence-enhanced applications: They add value to existing applications. For example: A presence-enhanced phone book, which is showed in the Fig. 1 . Presence could be embedded into all the contact list in a mobile phone (missed calls, received calls, etc.) • Presence-based information channels: They use Presence technology to deliver information to the users. For example: news alerts. Also in [2] a classification according to the type of service is presented: • Person-to-person applications: For example: IM or online games.

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Figure 1: Presence-enhanced phone book[2]

2006-05-4/5 The rest of the paper is organized as follows: the next section deals with Presence architectures in different environments: The first one is the Presence architecture for PoC, which is for cellular networks. The second architecture that we are going to describe is the Jabber architecture. Jabber is an open-source project for Presence and Instant Messaging on the Internet. And the third architecture presented is the Presence architecture in Mobile Adhoc networks. Studying these architectures will allow us to see different Presence protocols and how they are been integrated to enable network convergence. After that section we are going to explore some user scenarios of Presence Service that show advantages of using Presence service as well as disadvantages from the user’s viewpoint. Finally, the conclusions are presented.

2 Presence Architectures • Content-to-person applications: For example: Stockmarket information, a parking company can publish information about available parking places. • Corporate applications: For example: corporate directories, a calendar server (employee’s whereabouts). Notice that presence information can be shared by several applications: Internet Instant Messaging, fixed telephone networks, as well as variations of IM for the mobile environment such as PoC or a presence-enhanced phone book. Moreover, as we can see in the last two examples of the table 1 a service can be a provider of Presence information (news alert) or a consumer (voice mail) as well. PoC is one-way communication that instead of using text messages as IM and Internet chat uses short voice messages for the communication from one to one user or from one to several users. Indeed, this is not a new idea; walkie-talkies radio services have been available for a long time. However, PoC enhances the service with richer presence capabilities (presence-enhanced phone book, for instance). Instant Messaging and chatting are ones of the most successfully applications on the Internet; so it could be successful too if these applications are taken into the mobile environment. In this case PoC adapts nicely to mobile devices which does not have the comfortable keyboard of a PC. In the future through the phenomena of convergence of different networks; we can see the natural evolution of Presence service and PoC application toward their integration with other Internet applications like the Instant Messaging and chat. The motivation for writing this paper is to study the advantages and disadvantages of Presence Service so that knowing them we can explore future research fields and try to address the disadvantages. As Presence Service is already implemented in several applications and users are enjoying some of its advantages, it is more interesting to study the advantages in the environment of converging networks that would allow them to expand these advantages even further. Moreover, convergence with other networks such as ad-hoc networks may enable to access and enhance other services like the ones envisaged by the promoters of ubiquitous computing [3].

In fixed networks and in 3G and 2G Mobile Networks Presence service applications use the client-server paradigm. In other words they use a Presence server which is in charge to distribute presence information. However, in Ad-hoc Mobile Networks the client-server can not be applied because the decentralized nature of these networks [3]. In this case a P2P approach seems to be needed. Notice that although there are these two models of architectures, the set of protocols which dominate the market of Presence and Instant Messaging according to [4]; SIP/SIMPLE protocols and XMPP, are not depended on them [3].

2.1

Presence Architecture for PoC

The PoC architecture has been specified by several major telecommunication vendors and it is describe in [7]. Presence service is a fundamental part of PoC service and we will see how the Presence service is provided within this architecture. Moreover, all these specifications are based in the work of several standardization bodies of IP Multimedia Subsystem (IMS). The IMS is the result of the effort of the mobile communitity to integrate mobile networks with fixed networks such as the Internet [1]. The framework of IMS considers Presence service such a important service that will be used by several other services and that may become omnipresent [1]. Therefore, the Fig. 2 has been drawed according to these specifications. The boxes showed in the figure are functions as defined by the 3GPP. The implementer is free to implement a function in one or two nodes (servers) as well as combine functions into one node. The IMS server has the mission of providing a single entry for authentication and registration of all multimedia sessions (SIP connections) throughout mobile networks and fixed networks and to route and compress SIP messages. Furthermore, it enables the quality of service required for multimedia sessions. Because all kinds of media communications and services go through the IMS, this can apply different charging policies. This is important for operators and users because nowadays the only charging policy available is the charging for downloaded or uploaded bytes on the data connection. On the other hand IMS will allow to difference traffic (for example presence information bytes from PoC bytes

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2006-05-4/5 • Presentity: It is the entity that publishes its presence information. This can be a device or service. It can have only one Principal (see bellow) associated with. • Principal: It is the actual user, organisation or program that is interested in using a Presence Service either as a subscriber or a publisher of Presence Information. It can have several Presentities or Watchers associated with. • Watcher: It is interested in the presence information of a Presentity or several Presentities. Therefore, it can be subscribed to multiple presentities at once. This can be useful to save the bandwidth on mobile connections. • Presentity User Agent (PUA): It may be a user terminal or an element that is located on the network, which collects and sends presence information on behalf of some Presentity. Examples of terminals are mobile phones and personal computers. There are many examples of network elements to say few: GPRS Gateway Support Node (GGSN), which is the interface between GPRS networks and other IP networks; and Packet Data Serving Node (PDSN), which has the same function as the GGSN but for CDMA2000.

Figure 2: Presence Architecture for PoC[7]

and so on). The function of registration of IMS is also important because it opens new possibilities for the users who have several devices such as mobile devices, laptops or PDAs. Each user device may register to the IMS and this will associate it to a single user. Therefore, SIP messages may be distributed to all the devices of the user in similar way as we can see when somebody calls a phone number which has several extensions; all the phones ring at the same time and the user can pick up any of them [1]. From the Fig. 2 notice that all these services are running on the intranet of the operator. This and, the fact that the protocol used for Presence information is SIMPLE/SIP, facilitate the integration of Presence service with other fixed networks such as the Internet. The arrows on the figure represent interfaces as described in [7]; some of them are not being specified in that document such as the Ipl: Interface Presence Server/Resource List Server; and the Ik: Interface PoC Server/Resource Server. Also on the arrows are showed the protocols used by the interface; which include SIP, XCAP (explained below) and RCP/RTCP. The last two protocols are used to transport the voice (media plane) of a PoC communication. The following is the terminology used in figure (for more information, refer to [1, 7, 5, 6]. • Presence Information: It is a set of current attributes or characteristics of some presentity.

• Presence Server: It distributes and composites Presence information of some Presentity. In other words it associates several sources of Presence information (PUAs) with one Presentity. Moreover, it applies a set of policies in such a way that PUAs may update only part of the Presence Information and Watchers may only access part of it. For example, some elements of the network can provide the geographic location of the mobile phone; therefore, they must update only partiality the Presence Information stored in the Presence Server; whereas others such the mobile phone themselves may provide the user willingness to establish a communication and thus update another part of the Presence Information. • PoC Server: It enables the PoC service. • Resource List Server: It is in charge to manage contact and access lists. Contact list are like address book for PoC users, which allow them to initialise a PoC communication. Access Lists enable to control a PoC communication specifing who are allowed to receive Presence Information. It is fulfilled the Group and List Management Function (GLMF). This function may be distributed over several servers such as Presence Server and PoC server. The protocol used for communication amongst the Resource List Server and the user agents (PoC terminals) is the XML Configuration Access Protocol (XCAP), which has been created by the IEFT and is a protocol to read and modify XML configuration data stored on a server. XCAP maps XML sub-trees and its elements to HTTP URI so that they can be accessed using HTTP [8]. XCAP is used because it allows the users manage their contact and access lists in a convenient and standarised way separating the actual user interface. For example, users can add a new contact,

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delete or modify an old one; and they also can upload autorization policies into the servers [1]. As we can see in the Fig. 2 the communication from the PUA to Presence Service is carried using SIP and is through the IMS server. Therefore, PUA must be registered and authenticated in the IMS. For this communication SIP specific event notification mechanism is used [9] (SUBSCRIBE and NOTIFY requests; and PUBLISH request for publication of presence information). The PUA downloads the URI of the contact list from Resource List Server, which accomplished the GLMS function. Watchers have to be authorised by the Presentity to receive its presence information. The Presentity will receive a notification of any watcher who wants to access its presence information and then it can accept or reject the access. The steps required on the subscription of a watcher for presence information from multiple/single presentities are presented below. Notice that all the SIP messages are forwarded through the IMS. Roughly the watcher first sends a SUBSCRIBE message to the Presence Server. If the watcher is authorised to access the requested presence information then the server replies with a SIP 200 OK message. After that the Presence Server shall send the presence information document enveloped in a NOTIFY message. The watcher will respond to this message with a SIP 200 OK message. Two models exist for access presence information: Push and Pull models, they are described and analysed in [10]. In the Push Model the watcher is notified every time the presence information is updated by the presentity. On the other hand in the Pull Model the watcher requests the presence information every time it is needed. The flow of messages for publishing Presence Information is the following: the Presentity sends a PUBLISH message to the Presence Server and this shall answer with a SIP 200 OK message, which contains a Expires header. [9]

2.2

Presence for Internet Instant Messaging: Jabber

We study the Jabber architecture in this paper because Jabber is an open-source technology; therefore, all the information about the architecture can be found on the Internet. In contrast other popular Internet Instant Messaging services such as MSN Messenger or Yahoo Messenger use similar architectures but they are propietary tecnologies. MSN Messenger and other players of the Internet Instant Messaging are moving their technologies toward the use of SIP/SIMPLE protocol [11], the same set of propocols used by the 3GPP. However, Jabber uses the Extensible Messaging and Presence Protocol XMPP. Jabber/XMPP technology is not being left alone, Google Talk and others are using it [12] in their Instant Messaging, Chatting and voice-over-IP products. XMPP protocol has been standarized by the IETF as well as SIP. However, the work of the XMPP has been concluded whereas SIP and SIP/SIMPLE are still active working groups inside the IETF [13]. As it is showed at the Fig. 3, the Jabber architecture is a client-server architecture, although the XMPP protocol is not bind to any specific architecture, which is a feature shared by SIP. Nevertheless, XMPP is a very different technology from

Figure 3: Jabber Architecture[11]

SIP. For instance XMPP is used actually to transport the data in the communication between two entities on the network [11]; in contrast to SIP that is a signaling protocol used to control and establish the transport of the data (the session). We can locate XMPP in the same level as RTP in the communication between two PoC devices. Another difference with SIP is that XMPP uses a persistent connection in order to exchange Presence and Instant Messaging information. This connection is based in XML streams, which are containers of XML elements called XML stanzas. XML streams can be seen conveniently as XML documents although this is not completely correct because they are not documents but a stream of data [14]. XML stanzas are children of XML streams (using XML terminology). There are several kinds of XML stanzas; for instance CONVERSATION stanzas for conveying instant messanges; and PRESENCE for conveying presence information. It is also important to notice that this flow of information, the XML stream, is unidirectional. If a network entity engages an initial XML stream with another entity then the receiving entity must respond with another XML stream. As we can see in the Fig. 3 a Jabber server may be connected with other Jabber servers which make this architecture scalable. Also notice that Jabber server has a gateway for SIP communications. Because of the characteristic of XMPP of being a protocol of data transport, we do not see a Presence function in the Jabber architecture. In contrast with the Fig. 2 where a Presence server is defined. Also IMS does not appear here but a similar entity can be the Router oval. This router is in charge to distribute all the XML streams to the correct component inside the Jabber server.

2.3

Presence Service in Ad-hoc mobile networks

Ad-hoc networks consist of nodes which establish spontaneously a communication usually during a short period of

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2006-05-4/5 Doc2U API also extents the concept of presence awareness to shared resources being a resource any device or document. Document presence is used in collaborative writing exposing states such as: locked by some user, or being review by another user. The concept also expands the concept of presence from the current state to a recently previous or next states of the presentities, which opens several possibilities to the users [15].

2.4 Figure 4: Protocol stack for Presence Service in Ad-hoc mobile networks[3]

time. An advantage of these networks is that they do not require any infrastructure, which means a cheaper alternative to fixed and other centralisaded networks. Furthermore, they allow the instantaneous collaboration amongst several mobiles devices such as PDAs, laptops and increasingly a series of other devices and sensors that enables the so-called ubiquious computing. This set of devices that surrounds the user creates a context that can be exploited by intellegent agents that can act, adapt or expose intellegently presence information on behalf of the user. [15]. There are two proposals to implement Presence Service and Instant Messaging in Ad-hoc mobile network [3]: DoMo pervasive computing environment which is based in Jabber uses an fixed access point that is connected to a server; and another alternative is a fully decentralised architecture. In the paper refered in [3] the authors have implemented a fully decentralized Instant Messaging system in the enviroment of the Dublin Adhoc Wireless Network (DAWN), the system is depicted in the Fig. 4 In the Fig. 4 [3] each node has a topology of the network so that it knows the location of its neighborhood nodes. In the same way the management of Presence information is also carried out by each node. Therefore, presence awareness is bound up with the routing protocol. The routing protocol is an important part in the design of Ad-hoc networks, and the solution for the location of peers in DAWN is done by Nom. For presence and instant messaging, the protocol used is XMPP. As seen in the figure, DAWN has different kinds of terminals: PDAs, PC, Smart Mobiles and laptops. Each of these nodes has a wireless card (WLAN) that supports the wireless protocol 802.11b. The popularity of devices that are being shipped with wireless access is growing fast because the price of wireless technology is falling. Notice also that 802.11b has two modes of operation; with an access point and another one called Peep-to-peer Adhoc mode without a centralised point of access. We can see some important variations or extensions of the classic presence information as defined in other fixed and cellular environments. For instance, the states used for Presence information in Instant Messaging such as online, offline, available, away or busy; is extended in the model used by DoMo [15] with a new state: Around. This means that the node is in transist from one location to another and it is connected to the network for a short time. DoMo using the

Network convergence

An intense work for the standardisation of telecommunication technologies and services is carried out by different bodies [16, 1] with the objective of achieving the vision of network convergence. A fundamental part of the convergence is the IMS, which is being standardised by 3GPP for mobile networks. The ETSI [17] is working to take the SIP/IMS paradigm of 3GPP to the fixed broadband networks such as Asymmetric Digital Subscriber Lines (ADSL) or coaxial cable networks[1]. The name of these new networks being developed by the ETSI is Next Generation Networks (NGN). The vision of convergence means for the user viewpoint a seamless integration of different networks which provides a service anytime and anywhere. Indeed the users in the future will be unaware of which network they are using and the mechanisms for roaming amongst these networks will choose the most appropiate access network to deliver that service [17]. Therefore, presence service shipped with th IMS will be available seamless on mobile and fixed networks. 3GPP is adapting IMS to the requirements of fixed networks submited by the ETSI and according with [16] the release 7 will interwork with a larger range of networks such as WLAN; thus this process of standardisation will end up including all the networks studied in this section.

3 Some User scenarios of Presence Service Several user scenarios had been envisioned through the work of the Open Mobile Alliance (OMA), which is the body in charge to standarise the services and applications built on the top of the architecture and technology defined by the 3GPP. Most of the requirements showed in [18] involve the use of Presence Service as an improvement of Instant Messanging and the user contact list (the phone address book) which allows seeing the willingness and availability of the contact to establish a communication. Moreover, the presence information indicates the media which the contact wants to use for the communication (Instant Messaning, SMS, email, fixed phone, mobile, etc.) However, some user scenarios require that the users configure their terminals manually to expose an adequate presence information. This is done by using a set of profiles. For example, if the user arrives at her office, she would have to change her profile on her mobile device to “Office” profile, which means that people who want to contact her will see her presence information as “I want to be contacted by my office phone and only emergency calls can go through my mobile”. These changes of preferences or profiles can be difficult to manage for some users and for

TKK T-110.5190 Seminar on Internetworking most of users will mean too much inconvencience. Ways to improve user interfaces must be investigated to help users to manage those changes. But automatic management of these procedures can be done. In the business world this can be achieved by using a calendar application that provides presence information (Microsoft Exchange Server, Lotus Notes, etc.) Moreover, this application can provide along the classic presence information; information about the whereabouts of the user [18] (for example: “Sue is in a meeting with Bob about Presence service at hall T2”). In contrast, in the case of the large number of normal users who do not have access to a calendar application, this solution does not work. Products such as BT Fusion [19] which knows when the user is at home or out using the home Bluetooth wireless network, can give some insight of how to change automatically profiles without user intervention. As we saw in Presence Service for Ad-hoc mobile networks, the context provided by the devices that surround the user may update her presence information. Furthermore, convergence as we saw above will make Presence information available throughout different devices and networks. For instance in the user scenario described in [18], if a user is using an Instant Messanging application on her mobile device but later she log on her home computer using her fixed Internet connection; the presence information has to be updated accordingly. Other user scenarios such as advertisements and the subscription of alerts (events, news, weather, traffic, etc.) require the update of presence information through different networks as well as require that the user set complex rules and preferences for blocking users and filtering presence information. Thus ways to avoid this must also be investigated. We can see this in the following scenario: a user has her mobile device and is entering to a large mall which is providing access to its wireless network. As soon the user is entering the mall, her presence information need to be updated. This presence information can include additional information like the mall card number of a frequent buyer. Because the mall is able to track the customer habits of shopping using this number, the user can receive alerts of interesting offers for her into her mobile device. This user could need help to locate a shop or particular product; or she may be lost in the mall; therefore she would require to contact the customer help desk. Logically this kind of communication or access to a service provided by the mall must be free of charge for the users; therefore the user will see in her phone book a new temporal contact with a presence information such as “public mall help” with “busy/available” then the user can use her PoC mobile application and start to communicate with the mall staff. Moreover, this communication can include other multimedia content such as a map or video. This is an example of the future evolution of PoC, which is called Push to X [20]. Presence information can improve existing corporate directories, which can also be used to advertise services. A powerful search engine can exploit these directories to make it easy to find people and services. This will be more obvious in the future when users may broadly use presence-aware applications. In the world of collaborative work such as collaborative writing or brainstorm meetings (face-to-face, using video-

2006-05-4/5 conference or Instant Messaging). Several user scenarios can be enhanced with document presence information. For instance, in a meeting face-to-face all the participants may carry a PDA and form an ah-hoc network which allow them to share documents along with document presence information. These document can be the slides of a presentation, collaborative writing documents (wiki) or web pages being watched by the participants, which may be called collaborative browsering. Documents or web pages can have tags with additional information or they may even be bookmarked as we do using a web browser.

4 Conclusions We can summarise the advantages of Presence Service: • Presence service may facilate the use of other communication services. For example if a user sees that one of her buddies is online, this can animate her to start a communication with her bubby. In other words knowing the presence information of one contact can prompt the user to take further action. Moreover, because of using presence service users can feel that they keep a strong contact with her colleages, employees, friends and family. • Presence service may provide valuable information for users. For instance the user can know the location of the person who she wants to contact quite accurately. • Different applications, services and devices can share presence information, which will enhance these services as well as it provides consistencity from the user viewpoint. • Presence service can contribute to save costs in the utilization of networks because users can expose preferences for a specific media of communication: fixed phone, mobile phone, etc. Moreover, it can avoid the waste of resources; for example the time that users would spend if they call or try to establish communication with contacts that don’t want to be contacted or are unavailable. • The context surrounding the user created by several devices may provide presence information that later can be exploided by intelligent agents. By applying a set of heuristics or artificial intelligent techniques to the history of user presence information, agents can know the habits of the user (for instance, when and who she usually meet) and suggest services according to this information. Simple services such as suggestions for preferences make the establishing of a communication easier. Because the user is the centre of this context, she may feel that the services are intelligently customised for her, which is something novel and can allow the operators to differentiate themselves from their traditional role of communication enablers; role that has had a fierce competition nowadays. There are some disadvantages of using Presence service:

TKK T-110.5190 Seminar on Internetworking • As we saw in the section of user scenarios, to provide personalised services and to configure the privacy policies, users may have to interact with complex interfaces, which can be difficult for some of them. For instance, the user may want to make available her presence information for certain users. Two approaches are needed to address this problem; one is the research on usability and the other is the creation of smart services that, for example, with the help with ubiquious computing can free the user of going through these sometimes cumbersome procedures. • The availability of Presence information presents some concerns regarding the privacy of the users. Probably, users may not like to be checked out all the time, everywhere and by everyone. This can result users refuse to use the service at all. To avoid this presence service has to be fully customised and clear rules made be defined. Moreover operators or providers of the service must develop a solid position of trust to the users. This matter could be so important that it can influence the decision of the user of using one provider or another. For example, if a provider uses or leaks Presence information to third parties (governments, marketing campaings, etc.), it would damage its image and reputation. Also, technologies such as IPSec have to be deployed to protect presence information from being intercepted by no autorised people. • Presence information can include any kind of information; therefore, the format of messages used to deliver it, has to be extensible. Both SIP and XMPP propotols can be extended to support new kind of Presence information. It is also required that the providers and consumers of Presence information can interoperate smoothly in a way that users can enjoy all the advantages of Presence Service that we listed above. In fact, there are several devices that the user can use to access presence information. Therefore, a universal system for interoperation of these devices is needed. This requirement has been tackled through the effort of standarisation carried out by several telecommunication and Internet bodies. However, because of the wide range of providers and consumers of Presence information, now and in the future; on the top of the hardware interoperability (devices), a universal system of semantics has to be adopted. For instance semantic web technologies could be used as a system to establish semantics of Presence information.

Acknowledgments I would like to thank Leo Bhebhe, my tutor, for giving several ideas printed in this paper. He has also shared with me his valuable experience and guided me through the process of writing this paper.

References [1] Gonzalo Camarillo, Miguel A. Garcia-Martin The 3G IP Multimedia Subsystem (IMS), merging the Internet

2006-05-4/5 and the Cellular Worlds, Second Edition, Willey, 2006 [2] Nokia Oyj. Presence Application Development Guide, Version 1.0, Forum Nokia, April 30, 2003 [3] Derek Greene, Donal O’Mahony; Network and Telecommunications Research Group; Department of Computer Science, Trinity College, Ireland. Instant Messaging and Presence Management in Mobile AdHoc Networks, Proceedings of the Second IEEE Annual Conference on Pervasive Computing and Communications Workshops (PERCOMW’04), 2004 [4] Mourad Debbabi and Mahfuzur Rahman, Panasonic Information and Networking Technologies Laboratory The War of Presence and Instant Messaging: Right Protocols and APIs, IEEE, 2004 [5] 3GPP Universal Mobile Telecommunications System (UTMS); Presence service; Architecture and functional description; Stage 2, (3GPP TS 23.141 version 7.1.0 Release 7), ETSI, 2005 [6] 3GPP Universal Mobile Telecommunications System (UTMS); Presence service; Stage 1, (3GPP TS 22.141 version 5.2.0 Release 5), ETSI, 2002 [7] Comneon, Ericsson, Motorola, Nokia, Siemens Pushto-talk over Cellular (PoC); Architecture; PoC Release 2.0, Architecture V2.0.8 (2004-06), Technical Specification, 2004 [8] SIMPLE Internet-Draft The Extensible Markup Language (XML) Configuration Access Protocol (XCAP), draft-ietf-simple-xcap-07, Expires: December 13, 2005 [9] Comneon, Ericsson, Motorola, Nokia, Siemens Pushto-talk over Cellular (PoC); Presence Service; PoC Release 2.0, Presence Service V2.0.9 (2004-06), Technical Specification, 2004 [10] David Henrikson, Luleå University of Technology Analysis and Optimizations of Presence Generated Traffic for Cellular Networks; Master Thesis (January 28, 2005), http://epubl.ltu.se/14021617/2005/021/LTU-EX-05021-SE.pdf (referred 12.4.2006) [11] Samir Chatterjee, Tarun Abhichandani, Haiqing Li, and Bengisu Tulu (Claremont Graduate University) Jongbok Byun (Point Loma Nazarene University) Instant Messaging and Presence Technologies for College Campuses; IEEE Network, May/June 2005 [12] Google Talk Google Talk and Open Communications; http://www.google.com/talk/developer.html, (referred 27.2.2006). [13] The Internet Engineering Task Force (IETF) Active IETF Working Groups, http://www.ietf.org/ html.charters/wg-dir.html, (referred 1.3.2006) [14] IETF, Network Working Group Extensible Messaging and Presence Protocol (XMPP): Core, Request for Comments: 3920

TKK T-110.5190 Seminar on Internetworking [15] Jesus Favela, Christian Navarro and Marcela Rodriguez Extending Instant Messaging to Support Spontaneous Interactions in Ad-hoc Networks, Departamento de Ciencias de la Computacion, CICESE, Ensenada, Mexico; Facultad de Ingenieria, Universidad Autonama de Baja California, Mexico, http://wwww.cs.uoregon.edu/research/wearables/ cscw2002ws/papers/Favela.pdf (referred 12.4.2006) [16] R M Stretch and P M Adams Standards for intelligent networks, BT Technology Journal, Vol 23 No 1, Springer Netherlands, January 2005 [17] The European Telecommunications Standards Institute (ETSI), http://www.etsi.org (referred 12.4.2006) [18] Open Mobile Alliance (OMA). Presence Simple Requirements, Version 1.0, March 2005, http://www.openmobilealliance.org (referred 1.2.2006) [19] British Telecommunication. BT Fusion - the smarter mobile service. http://www.btfusionorder.bt.com, (referred 10.2.2006). [20] Nokia Oyj, White paper, Push to talk over Cellular stay connected, 2005, http://www.nokia.com/A482061 (referred 12.4.2006)

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