Re: comments on mech-v2-01

[Erik Nordmark <Erik.Nordmark@sun.com>]

> 1) A race is triggered when an IPv6 router that has a configured tunnel
>    with another router is doing dynamic mtu detection. The outcome of the
>    race is that one or more ICMPv6 "packet too big" message might not be
>    sent out to an host.
> 
> Assume an IPv6 network like:
> 
> [H1]-------->[R1]===========>[R2]--------->[H2]

>   5. H1->R1 TCP packet of size 1400 (this is a retry)
>   6. R1->H1 ICMPv6 "packet too big" with size 1300
>   7. H1->R1 TCP packet of size 1400 (this is a retry)
>   8. ... (the above cycle might repeat if there are more IPv4 routers
>      that send ICMPv4 "fragmentation needed" with 8 bytes of payload)

I don't understand how it can repeat. Do you think it can repeat forever?

When the 8-byte payload ICMP errors are sent then R1 will effectively
compute the minimum received (per IPv4 path MTU discovery).

It is true that in the case of 8-byte payload ICMP errors you get at
least two packet drops instead of at least one in the case of a single layer
of MTU discovery (R1 needs to learn the tunnel MTU which causes at least one
packet loss, and then H1 needs to learn the MTU from R1 which causes at
least one packet loss. (And in all cases there can be more than one packet loss
if there are multiple large packets in flight at the same time.)

> 9) Link-layer address (which is an IPv4 address) is not meant to be used
>    with ND. Is there any reason that the sending (of link-layer address)
>    is a "SHOULD NOT", and the receiving is a ?MUST ignore?. The sending,
>    and the receiving parts should be made consistent with respect to
>    link-
>    layer address. i.e. sending should be a "SHOULD NOT", and receiving
>    should be a "SHOULD ignore?, or sending should be a "MUST NOT", and
>    receiving should be a "MUST ignore?.

The reason it was written like this was to not immediately invalidate any
older implementations that might have sent the link-layer address options.
I don't know if there ever were any such implementations.

> Btw, "NOT" is not a keyword.
>    Hence "s/NOT/not".

It's upper case for emphasis, since I can't use bold face. I don't think
this use of upper case voilates any rules.


> Editorial
> ---------
> 
> 1) s/For that reason/For that reason,/

Noted.

  Erik