Subject: Re: [Idr] Re: Last Call: 'Connecting IPv6 Islands over IPv4 MPLS using IPv6 Provider Edge Routers (6PE)' to Proposed Standard

From: Eric Rosen <[email-masked]>
Date: Tue, 05 Sep 2006 12:55:29 -0400

Yakov> the current/original  encoding already provides a  way to distinguish
Yakov> between IPv4 and  IPv6 addresses ...  the NH Length  field is used to
Yakov> distinguish between IPv4 and IPv6 as the NH. 

Gee,  I thought  that the  use of  TLV encoding  was a  fairly well-accepted
technique in protocol  design.  Is there some added value  to be gained from
not  including  a type  field?   I guess  someone  might  consider "lack  of
extensibility" to be an added value ;-) 

On the other hand,  one could one say that omitting the  type field does not
restrict extensibility, because if one has a new type to send one can always
make sure  it has  a hitherto  unused length, even  if this  requires adding
padding.  The  only problem  would be  that whoever has  to write  that spec
would probably die from embarrassment.

Yakov> the current/original encoding provides  yet another way to distingush
Yakov> between IPv4 and IPv6 as the NH addresses - use two different SAFIs

Oh good,  more SAFIs.  Well,  what's simpler, adding  more SAFIs or  using a
type field?   ;-) Even  using the  length would be  better than  adding more
SAFIs. 

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