always-on connections
  • Users spending more time online purchasing communication services (such as music) and participating in high-value searchable offerings
  • Home networks with expanded network applications such as wireless Voice over IP (VoIP), home surveillance, and advanced services such as real-time video on demand (VoD)
  • Massively scalable games with global participants
  • Media-rich e-learning, providing learners with on-demand remote labs and lab simulations

    • Web Links IPv6 - WikiPedia
    http://en.wikipedia.org/wiki/IPv6#Larger_address_space
    Content 8.2 IPv6 Addressing 8.2.1 IPv6 Addressing Architecture The IPv4 header contains 12 basic header fields, followed by an options field and a data portion (usually the transport layer segment). The basic IPv4 header has a fixed size of 20 octets. The variable-length options field increases the size of the total IP header. IPv6 contains five of the 12 IPv4 basic header fields. The IPv6 header does not require the other seven fields. Routers handle fragmentation in IPv4, which causes a variety of processing issues. IPv6 routers do not perform fragmentation. Instead, a discovery process determines the optimum maximum transmission unit (MTU) to use during a given session. In the discovery process, the source IPv6 device attempts to send a packet at the size that is specified by the upper layers, such as the transport or application layer. If the device receives an “ICMP packet too big” message, it retransmits the MTU discover packet with a smaller MTU and repeats the process until it gets a response that the discover packet arrived intact. Then it sets the MTU for the session. The “ICMP packet too big” message contains the proper MTU size for the pathway. Each source device needs to track the MTU size for each session. Generally, tracking is done by creating a cache that is based on the destination address. However, it can also be done by using the flow label. If source-based routing is performed, tracking the MTU size can use the source address. The discovery process is beneficial because, as routing pathways change, a new MTU might be more appropriate. When a device receives an “ICMP packet too big” message, it decreases its MTU size if the Internet Control Message Protocol (ICMP) message contains a recommended MTU that is less than the current MTU of the device. A device performs an MTU discovery every 5 minutes to see whether the MTU has increased along the pathway. Application and transport layers for IPv6 accept MTU reduction notifications from the IPv6 layer. If they do not accept the notifications, IPv6 has a mechanism to fragment packets that are too large. However, upper layers are encouraged to avoid sending messages that require fragmentation. Link-layer technologies already perform checksum and error control. Because link-layer technologies are relatively reliable, an IP header checksum is considered to be redundant. Without the IP header checksum, the upper-layer optional checksums, such as User Datagram Protocol (UDP), are now mandatory. Web Links Implementing IPv6 Addressing and Basic Connectivity
    http://cisco.com/en/US/products/sw/iosswrel/
    ps5187/products_configuration_guide_chapter
    09186a00806f3a6a.html
    Content 8.2 IPv6 Addressing 8.2.2 Comparing IPv4 and IPv6 Headers The IPv6 header has 40 octets, in contrast to the 20 octets in IPv4. IPv6 has a smaller number of fields, and the header is 64-bit aligned to enable fast processing by current processors. Address fields are four times larger than in IPv4. The IPv6 header contains these fields:
    Content 8.2 IPv6 Addressing 8.2.3 IPv6 Extension Headers There are many types of extension headers. When multiple extension headers are used in the same packet, the order of the headers should be as follows:
    1. IPv6 header: Basic header described in the previous figure.
    2. Hop-by-hop options header: When used for the router alert (Resource Reservation Protocol [RSVP] and Multicast Listener Discovery version 1 [MLDv1]) and the jumbogram, this header (value = 0) is processed by all hops in the path of a packet. When present, the hop-by-hop options header always follows immediately after the basic IPv6 packet header.
    3. Destination options header (when the routing header is used): This header (value = 60) can follow any hop-by-hop options header, in which case the destination options header is processed at the final destination and also at each visited address specified by a routing header. Alternatively, the destination options header can follow any Encapsulating Security Payload (ESP) header, in which case the destination options header is processed only at the final destination. For example, mobile IP uses this header.
    4. Routing header: Used for source routing and mobile IPv6 (value = 43).
    5. Fragment header: Used when a source must fragment a packet that is larger than the MTU for the path between itself and a destination device. The fragment header is used in each fragmented packet.
    6. Authentication header and Encapsulating Security Payload header: Used within IPsec to provide authentication, integrity, and confidentiality of a packet. The authentication header (value = 51) and the ESP header (value = 50) are identical for IPv4 and IPv6.
    7. Upper-layer header: Typical headers used inside a packet to transport the data. The two main transport protocols are TCP (value = 6) and UDP (value = 17).
    Content 8.2 IPv6 Addressing 8.2.4 Defining Address Representation The 128-bit IPv6 addresses are represented by breaking them up into eight 16-bit