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

[Lou Berger <[e-mail]>]

Balázs,
A couple of comments below.

On 3/9/2017 4:02 AM, Balázs Varga A wrote:
> 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. 
The also can provide TE style resource control (allocation, enforcement,
even shaping and policing).  It may even provide LSP level
protection/restorations functions.

>  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.
This is up to the "client" layer, i.e., DetNet aware S&T PEs.  Note that
a P router is an LSR and  only operates on labels (either classic MPLS
or SR).  S-PEs and T-PEs are always on PEs, by definition, even when the
function doesn't reside connected to CEs.

Lou


>
> - 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