Re: [Detnet-dp-dt] FW: New update of the draft available

[Loa Andersson <[e-mail]>]

Balázs,

I'd not seen this before. I thought that we'd reached consensus on the
need to tunneling across the P routers after the comments from Jouni and
Yuanlong. Please see inline.

On 2017-03-13 18:09, Balázs Varga A wrote:
> Hi, mail below seems to be lost in hyperspace. I send it again, sorry for possible duplicates ... Cheers Bala'zs
>
> -----Original Message-----
> From: Balázs Varga A
> Sent: Saturday, March 11, 2017 7:54 PM
> To: 'Loa Andersson' <[e-mail]>nu>; [e-mail]
> Subject: RE: [Detnet-dp-dt] New update of the draft available
>
> Hi Loa,
>
<snip>

>> d-pw label with signaling that exposes the "request for DetNet
>> NSP/FRER" to P nodes
> Could You explain it more, I do not see your point. Do You propose that the L-label value would control whether a PW is a DetNet PW with PRER or not?
>

We discuss the "overlay network" in terms of P and PE nodes. The P node
does not not do PRER, while the PE may do so if we tell them.

However one node by serve as P in one overlay network, and as PE in
another.

Consider:

                 +------+
                 | PE-B1|
                 +------+
                    |
                    v
                 +------+
                 | P-B1 |
                 +------+
                    |
                    v
                 +------+
  +------+       | P-A1 |       +------+       +------+       +------+
  | PE-A1|------>| PE-B2|------>| P-A2 |------>| P-A3 |------>| PE-A2|
  +------+       +------+       +------+       +------+       +------+
                    |
                    v
                 +------+
                 | P-B2 |
                 +------+
                    |
                    v
                 +------+
                 | PE-B3|
                 +------+


Ledgend: PE-A = DA-*-PE, PE node in network A
          P-A  = P node network A
          PE-B = DA-*-PE, PE node in network B
          P-B  = P node network B

Problem is signalling!

If have the PW-Label un-tunneled PE-B will establish the unprotected PW
to PE-B3, requesting PERF of the PERF capable nodes.

Node PE-B2 will do PREF, which is fine, that is what it is supposed to
do. PE-B3 will eliminate duplicates as it is supposed to do.

PE-A1 will also try to set up an un-tunneled PW to PE-A2, PA-2, PA-3 and
PE-A2 will do what they are supposed to do. The problem is that the node
"P-A1" is also "PE-B2" and will understand the request for PERF, which
it is not supposed to do.

Our solution is to use the L-label to tunnel between DA-*-PE.

/Loa



> Thx & Cheers
> Bala'zs
>
> -----Original Message-----
> From: Detnet-dp-dt [mailto:[e-mail]] On Behalf Of Loa Andersson
> Sent: Saturday, March 11, 2017 3:38 AM
> To: [e-mail]
> Subject: Re: [Detnet-dp-dt] New update of the draft available
>
> Jouni,
>
> Mostly looks very good, the thing I don't understand is why you still say that the L-label is optional, it really isn't.
>
> - we need it to deliver the d-pw label unchanged
> - since we can't guarantee that the "P" nodes are not able to do
>    DetNet NSP, we can't set up the d-pw label with signaling that
>    exposes the "request for DetNet NSP/FRER" to P nodes.
> - needed for protection
> - the end-to-end tunnel must be the innermost tunnel, carrying
>    pw label
>
> There is one case, if two DA-*-PEs are immediately adjacent, there the L-lable will be an implicit NULL label and not appear in the stack, but for the control plane it is there.
>
> /Loa
>
> On 2017-03-11 07:25, Jouni Korhonen wrote:
>> * Added Loa’s comments on the L-label.
>> * Added Janos’ comments.
>> * Added extended forwarder text.
>> * Added (speculative text.. can be removed) D bit to flow-id word so
>> that we can check in a ring case the direction of the flow (note this
>> does not double history buffer space as claimed.. did not bother to
>> fix that)
>> * reworked the PW encapsulation pictures.
>> * Added more content to DA-*-PE descriptions.
>>
>> - Jouni
>>
>>
>

-- 


Loa Andersson                        email: [e-mail]
Senior MPLS Expert                          [e-mail]
Huawei Technologies (consultant)     phone: [phone]