Hi Manav,
Maybe I'm missing a key point but I think if you are using the new OSPFv3 
authentication on a link then all routers on the network corresponding to that 
link need to support it in order to form adjacencies. 
Thanks,
Acee
On Jan 19, 2011, at 7:05 AM, Bhatia, Manav (Manav) wrote:

> Hi Acee,
>  
> I think the idea behind this logic was for the purposes of backward 
> compatibility. I agree that this is not right if *all* routers support the AT 
> capability. However, if you have even one router that does not support this, 
> then you would probably need this mechanism.How would an implementation, that 
> is AT incapable, send an OSPFv3 + LLS block to a router, if the receiving end 
> always implicitly assumes the presence of an authentication trailer? One 
> could argue that if the AT router has turned ON authentication then it MUST 
> only accept packets with the AT block, but then we are taking a giant leap of 
> faith where we're assuming that ALL routers will simultaneously turn on the 
> AT mechanism.
>  
>  If folks think that this opens a security hole, then vendors could add a 
> knob that could toggle this behavior. By default, the knob could assume the 
> presence of an authentication trailer if auth has been turned on. The second 
> state would be where authentication trailer is assumed to be present only if 
> the AT bit is set.
>  
> If folks agree to this, then we could add a note about this in the next 
> revision.
>  
> Cheers, Manav
> From: Acee Lindem [mailto:[email protected]] 
> Sent: Wednesday, January 19, 2011 4.34 PM
> To: Rajesh Shetty
> Cc: Bhatia, Manav (Manav); [email protected]
> Subject: Re: [OSPF] AT Bit
> 
> Hi Rajesh,
> 
> You are correct. I thought that this was in the draft but see that it is not. 
> Right, we should drop packets with the AT Bit clear when authentication is 
> configured on the receiving side. OSPFv3 will drop packets not containing the 
> options field (LS-Request, LS-Update, and Ack) if the adjacency is not in 
> Exchange state or higher. 
> 
> Thanks,
> Acee
> On Jan 19, 2011, at 5:19 AM, Rajesh Shetty wrote:
> 
>> Dear All,
>> AT Bit Definition:
>> AT bit must be set in all ospfv3 protocol packets that contain an 
>> authentication trailer. On the receiving side authentication trailer is only 
>> examined if AT bit is set.
>> Consider a scenario where authentication trailer draft is supported by all 
>> the routers and authentication is configured on receiving side but not on 
>> sending side. Even in this scenario receiving side will successfully accept 
>> the packet (Since AT bit is not set), this is a security threat.
>> Please correct me if I am missing something.
>> Thanks
>> Rajesh
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>> -----Original Message-----
>> From: [email protected] [mailto:[email protected]] On Behalf Of Acee 
>> Lindem
>> Sent: Friday, January 07, 2011 8:39 PM
>> To: Bhatia, Manav (Manav)
>> Cc: [email protected]; Vishwas Manral
>> Subject: Re: [OSPF] Supporting Authentication Trailer for OSPFv3
>> Actually I was just making sure everyone was paying attention :^) Since I'm 
>> an author, I'll validate with Abhay and Stewart but I think we can move 
>> forward and make this a WG document.
>> Thanks,
>> Acee
>> On Jan 6, 2011, at 8:46 PM, Bhatia, Manav (Manav) wrote:
>> > I am sure Acee meant that the he and the authors would like to see this 
>> > draft adopted up as a WG draft.
>> >
>> > I agree with that sentiment and would request this to be accepted as a WG 
>> > document. We've had several mails in the past where this work was 
>> > supported and none that was against.
>> >
>> > Cheers, Manav
>> >
>> >> -----Original Message-----
>> >> From: Acee Lindem [mailto:[email protected]]
>> >> Sent: Friday, January 07, 2011 2.11 AM
>> >> To: [email protected]
>> >> Cc: Bhatia, Manav (Manav); Vishwas Manral
>> >> Subject: Supporting Authentication Trailer for OSPFv3
>> >>
>> >> Speaking as WG Co-Chair:
>> >>
>> >> At the last OSPF WG meeting, there was some interest in this
>> >> draft. I'm now asking for opinions for and against.
>> >>
>> >> Speaking as a WG member:
>> >>
>> >> The authors (myself included) would not like to make this a
>> >> WG draft. On the OSPF list and at the OSPF WG meeting, the
>> >> only dissent was on along the lines of making IPsec
>> >> (including IKEv2) work better with OSPFv3 rather than doing
>> >> this. I don't disagree that this should be a goal but I don't
>> >> think it should preclude this work.
>> >>
>> >> Thanks,
>> >> Acee
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