TCP/IP Tutorial and Technical Overview - IBM Redbooks

source routing, which operates in a similar way to source routing in IPv4 (see “IP
datagram routing options” on page 105).
Figure 9-7 IPv6 routing header
Where:
next hdr
Next hdr The type of header after this one.
Hdr length Length of this routing header, not including the first 8
bytes.
Type Type of routing header. Currently, this can only have the
value 0, meaning strict/loose source routing.
Segments left Number of route segments remaining, that is, number of
explicitly listed intermediate nodes still to be visited before
reaching the final destination.
Address 1..n A series of 16-byte IPv6 addresses that make up the
source route.
The first hop on the required path of the packet is indicated by the destination
address in the basic header of the packet. When the packet arrives at this
address, the router swaps the next address from the router extension header
with the destination address in the basic header. The router also decrements the
segments left field by one, and then forwards the packet.
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hdr length
reserved
address[0]
address[1]
type addrs left
/ / . . .
/ /
address[n-1]