Re: [Idr] 6PE-Alt draft

[Francois Le Faucheur IMAP <[e-mail]>]

Hi,

FYI, here is a note posted on the v6ops list where that topic was  
brought up first by Vishwas.


Begin forwarded message:
> From: Francois Le Faucheur IMAP <[e-mail]>
> Date: 31 January 2008 17:53:54 GMT+01:00
> To: Vishwas Manral <[e-mail]>
> Cc: Francois Le Faucheur IMAP <[e-mail]>,  
> [e-mail], "Jeremy De Clercq" <jeremy.de_clercq@alcatel- 
> lucent.be>, "Ooms Dirk" <[e-mail]>, [e-mail]
> Subject: Re: 6PE-Alt
>
>
> On 31 Jan 2008, at 15:25, Vishwas Manral wrote:
>
>> Hi Francois,
>>
>> The document I have written does not use signaling
>
> It is a bit of a stretch to claim that 6PE-Alt does not use signaling.
> 6PE-Alt and 6PE both use MP-BGP to signal IPv6 reachability.  6PE- 
> Alt would simply save you one field (the label value) inside the  
> same advertisement.
>
> On the other hand, 6PE-Alt would restrict operations to only one of  
> the options allowed in 6PE. The reasons 6PE allowed multiple label  
> allocation is precisely because different PEs may want to use  
> different label allocation policies.  For example, one 6PE router  
> may prefer to allocate per-prefix label in order to be able to  
> forward packets via label switching as opposed to performing IPv6  
> lookup. 6PE allows each PR router to use whatever label allocation  
> scheme it sees best.
>
>
>> and does not define
>> a new AFI/SAFI functionality to achieve the 6PE.
>
> It is a bit of a stretch to imply that 6PE defines a new AFI/SAFI.
> 6PE uses the IPv6 AFI and the SAFI defined in RFC3107 (which for  
> memory dates back from 2001) precisely for the purpose of binding  
> an MPLS label when advertising IPv6 reachability.
>
>>
>> The difference is obvious, we get the same functionality
>
> my impression is that you get a restricted subset of the  
> functionality (ie forcing every router to use that single label  
> allocation scheme). This had been discussed before and decided that  
> such a restriction was undesirable and unnecessary.
>
>> without
>> adding any new signaling mechanism.
>
> my impression is that both use the same MP-BGP signaling mechanism  
> except one would save a few bytes in the same MP-BGP advertisements.
>
> There are multiple interoperable implementations of 6PE today and  
> am not aware of significant issues with the current 6PE control plane.
>
> Cheers
>
> Francois
>



On 31 Jan 2008, at 16:00, Vishwas Manral wrote:

> Hi Jan,
>
> I am CC'ing the authors of the 6PE draft to get their views. Let me
> explain the draft in greater detail however.
>
> In 6PE, MP-BGP SAFI family label is used to exchange routes between 2
> 6PE routers (a new AFI/ SAFI combination is defined). Each route is
> attached with a label (which may be the IPv6 Explicit NULL label). In
> the data-plane this label is used as the inner label and the other
> label is the tunnel label, which gets the packet from source PE to
> destination PE. Once the packet gets to the destination PE, the inner
> label is looked up and a POP operation is done on it and the IPv6
> header is looked up in the routing table.
>
> With 6PE-Alt, no additional signaling mechanism is required. All we
> need to do is instead of using the signaled label as the inner label,
> we use the IPv6 Explicit NULL label. The same operations happen as 6PE
> without any explicit signaling of the labels with each route. It helps
> prevent all the excess signaling and still providing the exact same
> functionality. We are using the meaning implied in the "Explicit NULL
> Label". We do not need to signal anything here.
>
> As an alternate, if you notice in IPv6, the end sites/ devices will
> become IPv6 and the network may still have IPv4. If the assumption
> that each device in the IPv6 networks has a Global IPv6 address (not
> that IPv6 site local has been deprecated), we can do without the
> entire BGP MPLS IPv6 VPN functionality.
>
> Thanks,
> Vishwas
>
> On Jan 31, 2008 6:31 AM, Vishwas Manral <[e-mail]>  
> wrote:
>> Hi Jan,
>>
>> You may be missing the scope of the document. There is a  
>> discussion in
>> the v6ops group too which .
>>
>> The idea is simple. We do not need to define a new AFI/ SAFI
>> combination to achieve the 6PE functionality. We can just use the
>> meaning implied in the IPv6 Explicit NULL label. The 6PE RFC does  
>> talk
>> about allowing signaling for the Explicit NULL label in which case  
>> the
>> dataplane functionality becomes just the same, but in 6PE even  
>> that is
>> signaled using BGP extensions defined in RFC3107.
>>
>> Thanks,
>> Vishwas
>>
>>
>> On Jan 31, 2008 2:14 AM, Jan Novak <[e-mail]> wrote:
>>>
>>>
>>> Hi,
>>>
>>> Just out of curiosity - lets say you have two IPv4 VPNs with
>>> overlapping set of Pes and both of them want to provide 6PE
>>> service.
>>> When the explicit-null encapsulated packets from two different
>>> VPNs (but same PE) arrive to the other side PE - how do you
>>> decide which is which - e.g. which packet should be shipped to
>>> which VPN ??
>>>
>>> Jan
>>>
>>>
>>> _________________________________________________________________
>>> Telly addicts unite!
>>> http://www.searchgamesbox.com/tvtown.shtml
>>

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