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    2.3 Next generation: IPv6

        2.3.1 Aim of IPv6 from multimedia point of view

Evolution in both datacom and telecom seem to lead to convergence. In the future, there will no longer be this idea of separate systems to convey text data and real-time data. Networks will convey information. That is the reason why Internet Protocol evolved to this sixth version. It is supposed to conciliate the wills of both datacommunication and telecommunication networks. That is, using a packet routing protocol that is able to discriminate different data streams to forward first those that cannot undergo any delay.

        2.3.2 Why is IPv6 more efficient than IPv4?

• Performance point of view:
  Both Local Area Networks (LANs) and wide area networks (WANs) have progressed to ever-greater data rates, pushing into hundreds of megabits per second, with plans for gigabit LANs and WANs. In addition, as more services, especially graphics-based services, become available over the Internet, we can expect that the ratio of external traffic (traffic that leaves the local network) to internal traffic will rise. With these immense speeds and the increased load, it is critical that routers perform their functions as rapidly as possible. The router should be able to process and forward IP datagrams fast enough to fully utilize its high-speed links and to keep up with the traffic flow. A major factor is the hardware platform itself, but the design of the IP also plays a critical role. 
  
  Three aspects of IPv6 design contribute to meeting performance requirements: 
  - The number of fields in the IPv6 packet header is reduced from IPv4. A number of IPv6 options are placed in separate optional headers located between the IPv6 header and the transport-layer header. Most of these optional headers are not examined or processed by any router on the packet's path. This simplifies and speeds up router processing of IPv6 packets compared to IPv4 datagrams.3 It also makes it easier to add additional options. 
  - The IPv6 packet header is fixed-length whereas the IPv4 header is variable-length. Again, the IPv6 design simplifies processing. 
  - IPv6 routers do not permit packet fragmentation, although it is in IPv4. In IPv6, fragmentation may only be performed by the source. 
  
  
• Network Service:
  With the new version of IP, it becomes possible to associate packets with particular service classes, perform the routing function on the basis of those classes, and allow the networks along the route to make use of this class information. In particular, this allows the real-time services support and to specify priority levels to determine discard strategy in the event of congestion. IPv4 has proven its deficiency in this area. IPv6 enables the labelling of packets belonging to a particular traffic flow for which the sender requests special handling. This aids in the support of specialised traffic such as real-time video.
  
  
• Addressing flexibility:
  IPv4 was originally designed for host-to-host communication, thus it is best employed for unicast addressing: a single address bit pattern corresponds to a single host. Other forms of addressing are supported but poorly, partly because the address size is limited to 32 bits and partly because no provision is made for certain addressing modes. IPv6 includes the concept of anycast addressing, for which a packet is delivered to a single machine instead of a whole set of nodes. The scalability of multicast routing is improved by adding a scope field to multicast addresses.