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Re: Why, technically, MIP and IPv6 can't be deployed

2004-11-09 12:59:20


----- Original Message -----
From: Masataka Ohta 
<mohta(_at_)necom830(_dot_)hpcl(_dot_)titech(_dot_)ac(_dot_)jp>
Date: Wednesday, November 10, 2004 2:50 am
Subject: Re: Why, technically, MIP and IPv6 can't be deployed

Francis Dupont wrote:

   > Could you describe why exactly IPv6 can't run on the (layer 
2?) WLAN
   > infrastructure?
   
   That ND extensively, without any valid reason to do so, use
   multicast, which is not acknowledged at WLAN L2, means IPv6
   or its ND is unreliable over congested WLAN. If multicast
   ND packet is lost by congestion, it is not retransmitted by L2.
   
=> Masataka san, your argument is right (I saw 40% lost rate
on multicast over IEEE 802.11b) but it applies to IPv4 (ARP
uses broadcast) too...

Yes, it does, but not so badly.

ARP actually use broadcast for request but not for reply.

ND uses unicast for replies (Router Discovery may not though).

Moreover, ARP request from terminals to base stations, which
are often routers, are unicast at lower L2.

Same with ND.

Same with _any_ MAC unicast with toDS=1...

So, over WLAN, ARP works a lot better than ND. It should
also be noted that, with IPv4, it is natural to have link
specific adaptation mechanism for each different link type
that it is perfectly fine to have IP over WLAN which is
different from IP over Ether.

Your premises are incorrect,  the comparisons you are using are invalid.

On the other hand, ND, an attempt to have a universal
adaptation mechanism ignoring link specific properties,
which contradicts with the very basic reason to have
"adaptation", is a total failure.

Really, so does ARP, except where it's not supported, and requires
servers.
 
It should be noted that MIPv6 is hopelessly tainted by ND.

I'l take hopeless ND taints any day.

The ND architecture as part of IPv6 (rather than the link-layer)
allows L3 neighbour security mechanisms to be implemented once in
IP.

I think that retransmission timers, and ordering of messages
in ND can be altered.  The insecurity of ARP cannot.

Which do we need for the future 10-15 years of the Internet?

Greg 

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