[j-nsp] explicit-null

[Danny Vernals]

On Thu, Oct 9, 2008 at 5:10 PM,  <david.roy at orange-ftgroup.com> wrote:
>
> In fact It's not so clear !!! For a Juniper router :
>
> When I configure explicit-null in "protocol LDP" of my Egress Router (PE).
> The Egress LSR advertise for its "LDP address or PE addr" the value of 0. The penultimate router receives this value. For VPN trafic to the CE connected to the PE (in a VRF), The penultimate router replaces the TOP label by 0. So, the PE router receives "Layer 2 frame + Label 0 + VPN LABEL + IPV4 hearder ": It removes label 0 and then performes a lookup on the VPN LABEL.
>
> It's true ?

Exactly

>
>
> The use of the explicit-null on egress instead of implicit-null, is-it just to keep the CoS information ?

afaik yes.  This is certainly the main reason, there may be others but
I'm not aware of them.

>
> Thank you
> Regards
>
>
>
> -----Message d'origine-----
> De : juniper-nsp-bounces at puck.nether.net [mailto:juniper-nsp-bounces at puck.nether.net] De la part de david.roy at orange-ftgroup.com
> Envoyé : jeudi 9 octobre 2008 17:45
> À : Stacy W. Smith
> Cc : juniper-nsp at puck.nether.net
> Objet : Re: [j-nsp] explicit-null
>
>
> Ok. Thank you. It's clear now.
>
> Regards,
> David
>
>
> -----Message d'origine-----
> De : Stacy W. Smith [mailto:stacy at acm.org] Envoyé : jeudi 9 octobre 2008 17:29 À : ROY David DTF/DERX Cc : Danny Vernals; juniper-nsp at puck.nether.net Objet : Re: [j-nsp] explicit-null
>
> See RFC 4182.
>
> --Stacy
>
> On Oct 9, 2008, at 9:24 AM, <david.roy at orange-ftgroup.com> <david.roy at orange-ftgroup.com  > wrote:
>
>>
>> For the Q2 : extracted from the RFC 3032 :
>>
>> "MPLS Label Stack Encoding :
>>
>> A value of 0 represents the "IPv4 Explicit NULL Label". This label
>> value is only legal at the bottom of the label stack. It indicates
>> that the label stack must be popped, and the forwarding of the packet
>> must then be based on the IPv4 header."
>>
>>
>> So, Junos is not compliant of the RFC ???
>>
>> David
>>
>>
>>
>> -----Message d'origine-----
>> De : Danny Vernals [mailto:danny.vernals at gmail.com] Envoyé : jeudi 9
>> octobre 2008 17:15 À : ROY David DTF/DERX Cc :
>> juniper-nsp at puck.nether.net Objet : Re: [j-nsp] explicit-null
>>
>> On Wed, Oct 1, 2008 at 11:03 AM,  <david.roy at orange-ftgroup.com>
>> wrote:
>>>
>>> Hi all,
>>>
>>> When I use Explicit null on my Egress router (in LDP), The Egress
>>> advertises label 0 for its FEC : good.
>>>
>>> Q1:  I use MPLS VPN, therefore I have 2 Labels in the stack. The
>>> penultimate LSR replaces the value of  the top label per 0. The
>>> router keeps the EXP info and the second Label.  Is-it true ?
>>>
>>
>> yes
>>
>>> Q2: When the Juniper egress router receives the Label 0, It removes
>>> it and performes a lookup on the second labal ? Is-it true ?
>>>
>>
>> yes
>>
>> Are you seeing behaviour that seems to conflict with this?
>>
>>> Thanks
>>> David
>>>
>>>
>>>
>>>
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