> In RFC 2460 it states "IPv6 nodes must accept and attempt to process
> extension headers in any order and occuring any number of times in the same
> packet, except for the Hop-by-Hop Options header which is restricted to
> appear immediately after an IPv6 IP Header." Below are some discussions
> my colleagues and I have had on the Routing Type 0 extension header. Any
> insight you can shed would be appreciated.
[...]
>
>
> The second case that could cause multiple Type 0 Routing headers to appear
> in one packet is if an intermediate node inserted one.
The only way an intermediate node can insert additional extension headers
(actually insert anything that changes the length of the IP datagram) is
by encapsulating the packet with another IP header.
Anything else, e.g. taking a packet with IP+TCP and making it
IP+rthdr+TCP, breaks Path MTU discovery and would cause problems if AH was
used.
Thus the allowable "insertion" of a routing header is to conver
e.g. IP1+TCP to IP2+rthdr+IP1+TCP.
Erik
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