RE: accept_ mode and neighbor solicitaion (NS) pkts

Hi Steve,

I think that accept-mode is for accepting packets to the virtual
address for management purposes. It can also be used by applications
and other protocols so that rest of the world knows only about
the virtual address. As an example, OSPFv3 can use the virtual
link-local address for running the protocol. Since way, adjacent
routers will consider the VRRP group to be as if there it was only
router with one IPv6 address. For this to work, OSPFv3 control
packets to the virtual link-local address should not be dropped.

So, would it be possible that we define "accept-mode" only for virtual
addresses whose scope is global? This way, all packets to link-local
virtual addresses are always accepted.

John


> -----Original Message-----
> From: Stephen Nadas [mailto:[email protected]] 
> Sent: Thursday, November 08, 2007 9:04 AM
> To: John Cruz (johcruz); Don Provan; [email protected]
> Cc: [email protected]
> Subject: accept_ mode and neighbor solicitaion (NS) pkts
> 
> Hi John, Don, Bob,
> 
> I'd like to clarify what packets accept mode = off should apply to as
> follows: 
> 
> Suppose router A is IPv6 address owner of ipa, and router B backs up
> ipa.  Suppose also that  accept mode is in its default state of off on
> B.  Further imagine, if you will, a client with an (unsophisticated)
> neighbor unreachability detection implementation, by which I mean the
> client sends an neighbor solicitaion (NS) msg, gets a reply, sets a
> timer, when timer pops, sends another NS msg (ie, client 
> doesn't follow
> the SHOULD about using higher layer info to infer forward 
> progress).   
> 
> Finally, suppose that in between NS requests made by client, VRRP
> mastership for ipa switches to router B.  
> 
> The draft says: 
> 
>    Accept_Mode             Controls whether a virtual router in Master
>                            state will accept packets addressed to the
>                            address owner's IPvX address as 
> its own if it
>                            is not the IPvX address owner.  Default is
>                            False.
> 
> So, when NS pkt arrives at rtr B while it is master, rtr B 
> drops it bcos
> acccept mode is off.  Client will looses its address mapping 
> for ipa (at
> least for a time).  In analogous IPv4 case, ARP pkt won't 
> make it to IP
> layer, presumably ARP req/resp will flow and address mapping 
> will not be
> lost.   
> 
> I'd like to add text in next spin of draft to the above para 
> to clarify
> that accept_mode doesn't apply to NS requests, which we think resolves
> this.
> 
> Comments or objections?  There's at least a question in my mind about
> whether there are other IPv6 ICMP (control fn related) pkts that
> accept_mode should not apply to.
> 
> Thanks,
> Steve     
> 
>           
> 

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