Department of Teleinformatics Network Services Royal Institute of Technology
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- 4.2.2Mobile Devices
- 4.3Multimedia
- 4.3.2Quality of Service
- 4.3.3Broadcasting Media
- 4.3.4Hierarchical Transmission
4.2Plug and Play4.2.1Installing DevicesWhen home networking is to be introduced to the masses, a variety of network devices and appliances will probably already be available. The problem is that far from everyone has the network administrator’s knowledge that may be required to configure them and get them all working together. Without an easy-to-use, plug-and-play fashion solution, home networking would have a hard time entering the market. This is the reason why the IPv6 working groups put a lot of effort into making IPv6 a protocol that anyone could use without extra knowledge. It seemed reasonable that it should not be any difference in plugging in an intelligent IPv6 enabled television set from plugging in a conventional one. With the autoconfiguration mechanisms defined in IPv6, installing and connecting new devices or appliances to a home network will be a very simple task for anyone to do. In fact, just plugging the device into a network socket should be enough to give it global Internet access presuming the security policies admits it. If the network medium also is capable of acting power supply (e.g. IEEE 1394/Firewire, mains) plug-and-play is really the true word! 4.2.2Mobile DevicesFuture homes will most certainly contain numerous mobile devices connected to the Internet. Simple devices such as door keys, remotes, portable radios and watches may all have a small IPv6 stack implemented, enabling them to communicate with other devices and appliances. The autoconfiguration mechanisms featured in IPv6 provides for powerful, yet easy to use, mobility support and makes mobile computing a simple task. By using the home server as a mobile IPv6 home agent, it will also be possible to maintain a single IPv6 address wherever the device may be located. This brings up an interesting topic about the addressing in IPv6. Since the IPv6 address space easily can provide every person with a personal IPv6 address, why not give everyone a static address? The address should be based on a unique number such as birth date together with codes for place of birth etc, or maybe the SSN. With the mobility support, this address would then serve as a direct line to that person wherever he or she is, much like the number to the persons cellular telephone or pager. Incoming messages may then be rerouted to any device by assigning it with the appropriate address. Of course, this requires tight security as described in Section 4.4. 4.3Multimedia4.3.1ConvergenceT  he world of communication is about to change. Today, multiple separate services for transporting real-time information such as speech or video are used in parallel (e.g. TV, radio, and telephone). Each service typically requires its own specific medium, billing and end-user devices. This “redundancy”, with multiple services serving the same purpose of delivering information, will probably end with the introduction of home networking. By using a single information network such as the Internet, all kinds of information could be delivered in a uniform and easy accessible way (Figure 4 .9). Figure 4.9 The world of media is converging 4.3.2Quality of ServiceToday there are already many examples of real-time applications for internetworking available. These includes tools for listening to streaming music, watching streaming video on demand and Internet telephony (Voice over IP, VoIP). However, today’s Internet makes it hard for real-time applications to deliver the quality needed, especially all the way to the homes. The most limiting factor for home users today is probably the lack of bandwidth. Watching a movie in broadcast quality requires several megabits per second. Even with advanced compression algorithms, a single modem is simply not enough. The bandwidth problem will probably be solved in a very near future since many competing operators all racing to be the dominant provider with the majority of the homes as customers. The most common way to provide broadband today is through the cable TV network, which has proven to be a very attractive bearer. However, Quality of Service (QoS) is more than just bandwidth. It has to provide means for limiting or control the latency and jitter. In addition, resource reservation is desired when many different services are to be sharing the same medium. IPv6 is well prepared for real-time services. The latency will still depend heavily on the routers in the core networks, but with a fixed header size and no need for the routers to recalculate the header checksum every hop, the delay will probably be lower than today. The latency variation, the jitter, caused by changing routing decisions during a transmission, could also be limited by using the flow label. This would cause intermediate routers to serve all packets belonging to the same flow in the same way. Additionally, using the flow label in conjunction with a resource reservation protocol such as RSVP as described in Section 3.5.1 and the draft written by S. Berson [6], would also take care of the resource reservation issue. 4.3.3Broadcasting MediaIf broadcasting media such as TV and radio are to be carried over the Internet, it must support multicasting. Multicasting is used to send packets from one source to multiple destinations without unneeded replication. It is a hot topic, and much research is being performed to make multicasting available in IPv4. Currently, a “virtual” Internet called the MBONE makes multicasting possible by using tunnels between multicast capable routers, but still IPv4 multicast is far from fully deployed. IPv6, on the other hand, has native support for multicasting, making it ideal for broadcasting media. Every IPv6 capable router is required to handle multicast routing according to the specifications. An IPv6 node also has full multicast management support through the group management messages included in ICMPv6. When sending a TV broadcast, it would also be important to specify where the broadcast should be available. The multicast scope features in IPv6 multicasting make this selection an easy task. A regional news agency could choose to broadcast only to customers within the local neighborhood or the city. In the same way, national broadcasting companies could choose to limit their broadcasts to the country border as listed in Table 4 .4. This requires however that the conceptual borders are known by the routers and that all assigned scope values are commonly known. Table 4.4: Example of home networking multicast scopes
In home networking, the more common usage of broadcasting would be in-house distribution of audio and video. As a source, any IPv6 enabled TV receiver, DVD player or hi-fi equipment would do. The receivers would typically be video monitors and speakers used to present the streaming data. These kinds of transmissions would often use more local scopes than those used by the TV companies, maybe limited to “Apartment scope” or “Building scope”. The scope control would also be welcomed by all kinds of local authorities and persons such as hotels, tenants’ associations and employees for internal communication. 4.3.4Hierarchical TransmissionWhen broadcasting real-time multimedia to a vast number of customers, not all of those will use the Internet under equal conditions. While some may have the luck to access the Internet through the cable TV network featuring several megabits per second of bandwidth, others may have to be content with a simpler connection. The broadcast has to be accessible to all those customers, but the users using a high-speed connection will surely not settle with only getting the poor quality limited by the low-speed connections. One solution is of course to split the stream into multiple ones with well-defined bit rates. However, this method wastes bandwidth since the same content will have to be made available in parallel. A better solution is to use hierarchical transmission. By separating the source stream into incremental parts that together make up the original stream, a receiver may choose how much quality that should be received. For example, a videoconference with audio sampled at 22 kHz and video with a resolution of 640 by 480 pixels may be split up into four streams, or layers as illustrated in Figure 4 .10. The low-capacity customer may now choose to receive only the first layer with low-quality audio, while the high-speed user may be able to combine them all and thereby getting a higher quality stream.
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