On 1/12/10 3:34 PM, WashamFan wrote:
Hi,

   The 6rd CE and BR SHOULD support the IPv6 Subnet-Router anycast
    address [RFC4291] for its own 6rd delegated prefix.  This
allows, for
    example, IPv6 ping messages to be sent to the 6rd Virtual Interface
    itself for additional troubleshooting of the internal operation
of
    6rd at a given CE or BR, over and above an IPv4 ping to the
                                       ^^^^^^^^^^^^^^^^^^^ ( I don't
get it)
    associated CE or BR IPv4 address.  In the case of the BR, the IPv4
    address used to calculate the 6rd delegated prefix is the configured
    BR IPv4 Address.

we just tried to say that with a well known IPv6 address to ping
(subnet router anycast) then that can be used for troubleshooting. in
addition to using the IPv4 address. happy to edit if you have a
suggestion of better text.

Washam - Point is that an IPv4 ping, and an IPv6 ping encapsulated in

the same IPv4 address by 6rd both test the same reachability in terms
of
the CE to BR or CE to CE communication path, etc. Using IPv6 goes a
bit
further than that by ensuring that the 6rd mechanism itself is working

correctly.
Thanks for the explanation. I know now, it is the idiom "over and above"
that kept confusing me before I consulted a native speaker. Personally,
I think it would be easier for non-English speaker like me to read if you
use "in addition to" or something similar instead. (I used to interpret it
as IPv6 ping over IPv4 ping which makes no sense ;-)
Ah, I see. We'll work on something that avoids idioms here.
Besides, I wanna ask, are you saying IPv6 ping is only for the test between
CE and BR? I assume yes since anycast address is considered here.
The IPv6 anycast address here is to ping any CE or BR, and from any IPv6 host. It's simply a way of relying on a known IPv6 address at any 6rd node to be used for isolated troubleshooting using IPv6 messages and the 6rd encapsulation technique.

- Mark
washam


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