Re: [Detnet-dp-dt] one question on S-DetNet-PEs

[Balázs Varga A <[e-mail]>]

Hi,

Generally agree, just two additional notes/comments:
- Mandatory tunnels:
They are needed anyway for regular P nodes. The DetNet role of intermediate 
"P" nodes is limited to ensure congestion protection.  However P nodes can 
usually recognize only LSP labels and cannot consider the whole label stack for 
flow recognition.  Therefore if DetNet flows would not use tunnels P nodes may
not distinguish them from regular (non-DetNet) flows and cannot achieve congestion
protection.

- DA-S-PE needs also PW and FRER specific configuration:
As clarification to the step when "DetNet-PW-label is allocated by the DA-S-PE for 
the DA-T-PE". You wrote:
   > the DetNet-PW-label is allocated by the DA-S-PE for the DA-T-PE, and
   >  as the LSP is set up an instruction is entered into the LFIB whether
   >  the DA-S-PE should do FRER or not.
I think we need more than a simple instruction "to do FRER or not". The egress
replication on the DA-S-PE (towards the next DA-S-PE(s) or the terminating 
DA-T-PE) may be DetNet-flow specific (how many member flows should be created,
which tunnel should be used by the egress member flows, etc.). 

I think we do not have signaling for that DetNet-flow and FRER specific configuration.
Do we intend to configure them in advance via management?

Cheers
Bala'zs

-----Original Message-----
From: Detnet-dp-dt [mailto:[e-mail]] On Behalf Of Loa Andersson
Sent: Thursday, March 09, 2017 2:31 AM
To: [e-mail]; [e-mail]
Subject: Re: [Detnet-dp-dt] one question on S-DetNet-PEs

Jouni, et.al.,

On 2017-03-09 04:18, Jouni Korhonen wrote:
> Good guestion.
>
> I guess, if you want a specific node to be a S-DetNet-PE for some 
> overlay and P for other, you could "tunnel" through it in P case.

Yes - I think that is necessary. There is a bit more too it though.
> The
> currect draft still has text for "overlay labels" (i.e., L-labels) and 
> I think those would work nicely for this case as you say below.

OK - leave that in! There is a terminology issue here, the way we are doing things now, the L-label is the PSN tunnel in the PW architecture.

The caveat is that PSN tunnel needsto be mandatory, unless you want to have a very complicated configuration for when a node is P for one overlay but DA-S-PE for another.

Let me see if I got right

- the PSN-tunnel (PHP'ed at the P node adjacent to the DA-S-PE) takes
   the DetNet PW to the DA-S-PE.

- the DetNet-PW-label is allocated by the DA-S-PE for the DA-T-PE, and
   as the LSP is set up an instruction is entered into the LFIB whether
   the DA-S-PE should do FRER or not.

- DA-T-PE establish a PSN-tunnel through which the DetNet PW is
   tunneled.

- in the case of using a signaling protocol (since this is PWs I guess
   it by default is LDP) to establish the PW, no other node than the
   DA-S-PE, and the egress (DA-T-PE) sees the request for FRER.

- for signaling the L-Label/PSN tunnel, RSVP-TE could be used, which
   means that the L-Label/PSN-tunnel also serves at BW container.

Did I get that right?

Yes I think it will work.

/Loa

>
> - Jouni
>
> 3/8/2017, 5:03 AM, Loa Andersson kirjoitti:
>>
>> Folks,
>>
>> There might be a simple answer, but I don't see it just now.
>>
>> Suppose we have a network, where we designate a certain number of 
>> nodes as S-DetNet-PEs, to build a nice overlay DetNet.
>>
>> Assume that we also designate another set of nodes as S-DetNet-PEs 
>> for another overlay DetNet.
>>
>> Also assume that some nodes that are S-DetNet-PE in one network are 
>> P's in the other.
>>
>> If we signal that we have have a detnet-ms-pw going through a P node 
>> that is capable of doing elimination/replication, how do we stop the 
>> P-node from doing that?
>>
>> This was something that the T-Lables did for us.
>>
>> /Loa

-- 


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

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