o  Flow Labeling Capability

         A new capability is added to enable the labeling of packets
         belonging to particular traffic "flows" for which the sender
         requests special handling, such as non-default quality of
         service or "real-time" service.







 
RFC 2460                   IPv6 Specification              December 1998


      o  Authentication and Privacy Capabilities

         Extensions to support authentication, data integrity, and
         (optional) data confidentiality are specified for IPv6.

   This document specifies the basic IPv6 header and the initially-
   defined IPv6 extension headers and options.  It also discusses packet
   size issues, the semantics of flow labels and traffic classes, and
   the effects of IPv6 on upper-layer protocols.  The format and
   semantics of IPv6 addresses are specified separately in [ADDRARCH].
   The IPv6 version of ICMP, which all IPv6 implementations are required
   to include, is specified in [ICMPv6].

2.  Terminology

   node        - a device that implements IPv6.

   router      - a node that forwards IPv6 packets not explicitly
                 addressed to itself.  [See Note below].

   host        - any node that is not a router.  [See Note below].

   upper layer - a protocol layer immediately above IPv6.  Examples are
                 transport protocols such as TCP and UDP, control
                 protocols such as ICMP, routing protocols such as OSPF,
                 and internet or lower-layer protocols being "tunneled"
                 over (i.e., encapsulated in) IPv6 such as IPX,
                 AppleTalk, or IPv6 itself.

   link        - a communication facility or medium over which nodes can
                 communicate at the link layer, i.e., the layer
                 immediately below IPv6.  Examples are Ethernets (simple
                 or bridged); PPP links; X.25, Frame Relay, or ATM
                 networks; and internet (or higher) layer "tunnels",
                 such as tunnels over IPv4 or IPv6 itself.

   neighbors   - nodes attached to the same link.

   interface   - a node's attachment to a link.

   address     - an IPv6-layer identifier for an interface or a set of
                 interfaces.

   packet      - an IPv6 header plus payload.

   link MTU    - the maximum transmission unit, i.e., maximum packet
                 size in octets, that can be conveyed over a link.





 
RFC 2460                   IPv6 Specification              December 1998


   path MTU    - the minimum link MTU of all the links in a path between
                 a source node and a destination node.

   Note: it is possible, though unusual, for a device with multiple
   interfaces to be configured to forward non-self-destined packets
   arriving from some set (fewer than all) of its interfaces, and to
   discard non-self-destined packets arriving from its other interfaces.
   Such a device must obey the protocol requirements for routers when
   receiving packets from, and interacting with neighbors over, the
   former (forwarding) interfaces.  It must obey the protocol
   requirements for hosts when receiving packets from, and interacting
   with neighbors over, the latter (non-forwarding) interfaces.

3.  IPv6 Header Format

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version| Traffic Class |           Flow Label                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Payload Length        |  Next Header  |   Hop Limit   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                         Source Address                        +
   |                                                               |
   +                                                               +