Towards the Intelligent On-line Home Office

Transcription

1 Towards the Intelligent On-line Home Office S.Antoniazzi, M.Pampolini OCEANS Customer Equipment & Networks Lab. Italtel spa Introduction The opportunity to telework, as well as to establish small offices at home, is attracting a growing base of residential customers worldwide, due in particular to the low-cost communication infrastructure offered by the Internet. Some achievements relevant to such a scenario are reported, belonging to Italtel internal research activities as well as to OCEANS (Open Communication Environment for Agent-based Networked Services), a European research project (ACTS AC323) concerned with improving the human-machine dialogue by means of software agent technologies in the context of the residential market. While the main focus of OCEANS is on infotainment and electronic commerce applications, most of the specifications and demonstrators developed are suitable for a SOHO (Small Office / Home Office) environment as well. OCEANS enhances the pioneering work started earlier in 1995 with MUSIST (Multimedia User Interface for Interactive Services and TV), one of the first European projects (ACTS AC010) to investigate interactive set-top-box architectures and user interfaces in particular. Moreover, the approach incrementally developed in MUSIST and OCEANS is now going to be extended with new projects (EUROPA, BRIC) in the European Commission ITEA programme. When targeting telework services for the residential / SOHO domain, new technical issues arise. The most significant of them is probably the coexistence in the customer premises of multiple heterogeneous user terminals, typically at least one PC for the computational tasks (word processing, data base management, etc.) and a TV-oriented set-top-box for infotainment and electronic commerce. An even more sophisticated scenario could include additional appliances such as Internet phones and other kinds of thin clients. It should be pointed out that all devices would need network access, to the Internet and possibly other IP networks. Sharing of peripherals such as printers, scanners and mass-storage devices will be also required. While a large number of technologies are currently proposed for home networking, this report will focus on Ethernet-based solutions. Indeed, Ethernet is a low-cost and widely available communication standard for PCs and can be implemented in set-top-boxes as well, as in the case of the MUSIST and OCEANS terminals. The Ethernet data link layer is also used in phone-line home networks enabling up to 1 Mbit/s bandwidth using existing home cabling. Moreover, Internet access devices supporting xdsl broadband technology and Ethernet connections to home appliances are already available in the market. 99

2 The multi-session scenario In the context of a residential / SOHO domain, emerging technologies such as ADSL (Asymmetrical Digital Subscriber Line) and other broadband data access solutions enable subscribers to access the Internet and other networks at much higher speeds (up to 6-8 Mbit/s downstream) than those available through analog modems (56 Kbit/s) and ISDN (64 or 128 Kbit/s). The following picture illustrates the scenario of different customer premises connected to the Internet through different networks: Figure 13: Broadband access scenario. However, there is still the need for an effective and efficient way of interconnecting multiple end-user terminals (PC, STB, etc.), among themselves for local communication as well as to the so-called Network Termination (NT) or ADSL Transmission Unit Remote (ATU-R), which in turn is able to provide the desired external connectivity to the Internet and other data networks. This would allow multiple users within a home to share the same high-speed link to the service provider (ISP) value added services, while simultaneously having the possibility of sharing local terminal peripherals, thus leading to the idea of a Customer Premises Network (CPN). In a more detailed view, a possible situation for the CPN is shown in the following picture. 100

3 Figure 14: Customer premises network. The client terminals can be interconnected through many different physical media but, in most common cases, an Ethernet MAC (Medium Access Control) layer is exported to the upper network protocols, due to the fact that Ethernet is currently the most cost effective and simple LAN technology. Furthermore, the connection between the CPN and the desired ISP(s) is established by means of the wide-spread and easily manageable Point to Point Protocol (PPP), in order to allow the required authentication mechanisms and to set up the needed point to point link. The PPP session is in turn mapped by the NT into a well-defined ATM virtual channel which is terminated by either the Central Office equipment (CO) or the ISP itself. Finally, the choice of using ATM over ADSL is due to the intrinsic capability of ATM to provide Quality of Service (QoS) together with the high bandwidth available with the use of ADSL technology. These requirements are mandatory, in particular, to implement real time services such as audio/video streaming over the Internet. At the same time, it is necessary to guarantee that all clients are able to intercommunicate when no remote access connection is established or when the NT is switched off. This means that every device that is connected to the CPN must be provided with its own local IP address, either statically or dynamically assigned, valid only in the context of such a network. These considerations lead to two major required kinds of connectivity, while the basic assumption is always that multiple terminals are involved and a single PPP session is allowed for each terminal: Homogeneous sessions (only one service provider available at a time): global connectivity can be accomplished by terminating the PPP session at the NT. Only one official IP address is assigned to the CPN, so the NT must perform some kind of address translation mechanism (such as NAT) to guarantee simultaneous Internet access. The terminal-owned local IP address remains valid inside the CPN and the NT itself acts as an IP gateway. The PPP session is mapped to an individual virtual channel at the NT side. 101

4 Heterogeneous sessions (more than one service providers available at the same time): individual connectivity should be accomplished by extending the PPP session from the NT to the end system across the CPN, that is every user performs his own dial-up connection and authentication. A solution must be adopted to carry the different PPP sessions across the CPN; every session that refers to the same service provider is mapped to the corresponding virtual channel at the NT. In this case a second IP address, an official one, is assigned to each terminal that sets up a remote connection. The need for the second kind of connectivity will arise more and more with new services and with the opportunity to telework: consider an employee who needs to access his/her company s virtual private network (VPN) while another member of the same family wishes to connect to the personal ISP. Currently there are several different proposals specifying how these requirements can be satisfied: however many of these proposals involve significant user configuration of the modem and, in some cases, require users to deploy ATM network interface cards (NICs) in their personal computers both of which impose significant complexity on the end user. This complexity may hinder the rapid, widespread consumer adoption of high-speed services such as ADSL. In the contrast, the PPP over Ethernet (PPPoE) protocol, now available in the form of an Internet standard (RFC 2516), provides the ability to connect multiple hosts at a remote site through a common NT device. In addition, it provides access control and billing functionality in a manner similar to dial-up services using PPP. Each terminal equipment is provided with its own PPP stack and the user is presented with a familiar dial-up networking user interface. Access control, billing and type of service can be controlled on a per-user, rather than a per-site basis. By combining the simplicity of Ethernet technology with the proven scalability and administrative controls of PPP, ISPs and carriers are presented with a new approach to speed deployment of high-speed Internet services with proven and familiar technologies PPP and Ethernet. Moreover PPPoE makes it easier for service providers to provision services to support multiple users across a dedicated digital subscriber line (DSL), cable, or wireless connection. It also simplifies the end-user experience to dynamically select between services. By making the customer premises equipment (CPE) easier to configure, ISPs costs are reduced and their ability to rapidly deploy services to thousands of subscribers is enhanced. From a protocol point of view the homogeneous connectivity leads to the architecture depicted in the following picture: 102

5 Application Protocols IP IP Routing PPP Ethernet MAC Ethernet MAC AAL5 ATM Physical Layer (10BaseT, HomeRun, etc.) ADSL Terminal (PC, STB, Web Phone, etc.) NT Figure 15: Protocol stack for homogeneous sessions. As can be seen, the PPP session is terminated at the NT, thus allowing multiple simultaneous connections with only one Service Provider. Moreover this involves an increased complexity in the NT itself, though the CPN terminal is kept unchanged. On the other hand, the heterogeneous connectivity leads to the architecture depicted in the following different picture: Application Protocols IP PPP RCF 1483 Ethernet MAC Ethernet MAC AAL5 ATM Physical Layer (10BaseT, HomeRun, etc.) ADSL Terminal (PC, STB, Web Phone, etc.) NT Figure 16: Protocol stack for heterogeneous sessions. Here an increased complexity on the terminal side can be observed, but in fact this is exactly the same case as when a connection to the Internet through an analog modem is adopted. On the other side, the NT simply acts as an Ethernet bridge between the CPN and the outside world. RFC 1483 specifies how an Ethernet frame must be encapsulated into AAL5 PDUs: in this way the Ethernet LAN is seen as extended to the ISP, where the PPP session terminates again. 103

6 Multi-session capabilities for the Internet set-top-box Within OCEANS and the other projects mentioned above, a thin client approach has been taken for the user terminal. A thin client is a device with lower cost and higher usability than a conventional personal computer. Of course, there are contexts when a thin client cannot replace a PC. However, thin clients can be used as complementary terminals in many areas, in particular when multiple users or access points are required and when user expertise is limited. The terminal architecture specified and implemented in the OCEANS project is founded on the Java emerging standard. Furthermore, Italtel has developed a custom Java-based Internet navigation software. The system can operate in a conventional configuration (monitor, keyboard and mouse) as well as in a living room set-up (TV set and infrared remote controller, including integrated micro-keyboard). Unlike most thin client browsers, the Italtel navigation software is compliant with the latest Internet standards, including HTML 4.0, XML, DOM, and ECMAScript. It also supports Java applets and the SSL security protocol. Local networking based on phone-line and wireless technologies is currently under experimentation and a bandwidth in the range of 1 Mbit/s is expected. Concerning Internet access, a broadband solution based on an ADSL/ATM link via network termination (ATU-R) device, is supported. The terminal is currently equipped with an Ethernet (10 Mbit/s) port and work is in progress to provide ATM Forum (25 Mbit/s) and USB (12 Mbit/s) interfaces as well. Multi-session capabilities based on the PPPoE protocol will allow to use multiple set-topboxes in the home, as well as enabling telework activities from a PC while using the STB for infotainment tasks. References Antoniazzi S., A Flexible Software Architecture for Multimedia Home Platforms, IEEE Tyrrhenian International Workshop on Digital Communications Multimedia Communications, Ischia, Italy, September Antoniazzi S., Marmolin H., Schapeler G., Weickert B., The MUSIST Browser and Navigation Concept, Proc. of European Conference on Multimedia Applications, Services and Techniques (ECMAST 98), Berlin, Antoniazzi S., Schapeler G., Interoperability for multimedia home platforms, Proc. of Interworking 98 Conference, Toronto, Antoniazzi S., A Virtual Machine Approach for Delivering 2D/3D Applications to Networked Terminals for Residential Users, International Workshop on Synthetic-Natural Hybrid Coding and Three-Dimensional Imaging, Rhodes, Greece, September Antoniazzi S., Schapeler G., An Open Software Architecture For Multimedia Consumer Terminals, Lecture Notes in Computer Science, Multimedia Applications, Services and Techniques ECMAST 97, Vol.1242, pp , Springer-Verlag, Antoniazzi S., Ievola C., Marcozzi E., Penzo R., Sturlesi M., An Authoring And Run-Time Environment For Interactive Multimedia Services, Lecture Notes in Computer Science, 104

7 Multimedia Applications, Services and Techniques ECMAST 97, Vol.1242, pp , Springer- Verlag, Antoniazzi S., Buschmann J., Marcozzi E., Profumo A., Internet and New Interactive Multimedia Services: Integration Opportunities, European Conference on Multimedia Applications, Services and Techniques (ECMAST 96), ACTS Session, Louvain-la-Neuve, Belgium, Buschmann J., Pampolini M., ATM interface design issues for IP traffic over ATM/ADSL access networks, SPIE International Symposium on Voice, Video and Data communications, Boston, November Heinanen J., RFC 1483, Multiprotocol Encapsulation over ATM Adaptation Layer 5, July Mamakos L. et al., RFC 2516, A Method for Transmitting PPP Over Ethernet (PPPoE), February