1.4 ROUTING HEADER

The IPv6 source uses the Routing header to list at least one intermediate node to be seen along the way to the packet's destination. In essence, this functionality is somewhat similar to IPv4's Source Route options. The Routing header is designated by a Next Header value of 43 in the header just prior to it.

If, when a received packet is being processed the node comes across a Routing header with an unknown Routing Type value, the specified behavior of the node is dependent upon the value of the Segments Left field.

Should the Segments Left be zero, then the node should ignore the Routing header and go directly to processing the next header in the packet. The Next Header field in the Routing header designates that packet's type.

Should the Segments Left not be zero, then the node needs to throw the packet away and transmit an ICMP Parameter Problem, Code 0. This refers to sending a message to the packet's Source Address in an effort to aim towards the unrecognized Routing Type.

Multicast addresses (each of the set of nodes) can not appear in a Routing header of Type 0, or in the IPv6 Destination Address field of a packet holding a Routing header of Type 0 as shown in Figure 1.2.

Should the bit number 0 of the Strict/Loose Bit Map have a value 1, the Destination Address field of the IPv6 header in the original packet needs to designate a neighbor of the...