Re: [Detnet-dp-dt] Using MS-PW concept for the d-pw

[Jiangyuanlong <[e-mail]>]

Loa,

-----Original Message-----
From: Loa Andersson [mailto:[e-mail]] 
Sent: Saturday, February 25, 2017 3:34 PM
To: Jiangyuanlong; Jouni Korhonen
Cc: [e-mail]
Subject: Re: [Detnet-dp-dt] Using MS-PW concept for the d-pw

Yuanlong,

The L-laabel is ther to make the the intermediate not (S-PE) know what to do whit the packet, the d-pw label was not allocated by the S-PE, so it does not ahve any knowledge what it means.
[YJ] d-pw can be allocated by the S-PE in MS-PW, just as you would like to allocate the L-labels. Very similarly, I think the same T-LDP protocol can be used.
[YJ] As I said in the previous email, using PW to trigger FRER will be cleaner compared with using L-label since CW is inspected.

If you let the S-PEs allocate and swap d-pw's, the next S-PE or a T-PE can't coordinate for the same packet coming in on from tow different nodes.
[YJ] It's like the 1+1 PW protection case, though the operations of elimination and replication in the S-PE and the T-PE need to be specified.
[YJ]Take VPLS as an example, several PWs can be directed into the same VSI in a PE and PW packets are processed there (for detnet, the processing is FRER now).

But I feel like we are going in circles, can we agree on the corner stones first?

Do we want all possible/conceivable control mechanism be within scope?
[YJ] maybe we can take LDP as a first step. It seems the difficulty is how to decide the S-PEs for a detnet flow (a routing protocol may be needed for automatic selection). 
[YJ] if all T-PEs and S-PEs are determined for a detnet flow, it is quite easy to set up PW segments and LSPs respectively with the help of LDP protocol. 
Cheers,
Yuanlong

/Loa


On 2017-02-25 15:18, Jiangyuanlong wrote:
> I agreed to alternative 2. L-label is not needed, S-PE must look into the PW label (further, extract sequence number in the CW) of a packet, and all FRER semantics can be coupled with the PW label.
>
> -----Original Message-----
> From: Jouni Korhonen [mailto:[e-mail]]
> Sent: Saturday, February 25, 2017 3:07 PM
> To: Jiangyuanlong
> Cc: [e-mail]; Loa Andersson
> Subject: Re: [Detnet-dp-dt] Using MS-PW concept for the d-pw
>
> Hi,
>
>> [YJ] I regard the L-Labels and T-labels are the same LSP layer. If we look into the full MPLS label stack of a packet in a PW, normally there is an LSP label at the top (unless PHP is enabled for the last hop).
>> Not sure what is the L-Label in your picture, is it different from LSP label?
>
> L-labels have been so far in the discussion between MS-PW PEs. 
> T-labels are between any LSR. L-labels are not PHPed i.e., even if PHP 
> is enable the L-Label stays and the label above it gets popped (that 
> we have been referring as T-Labels). T- and L-labels are just a naming 
> convention. IF you don’t have “between MS-PW PEs” semantic associated 
> with the L-Label, it is the same as T-Label ;)
>
>
>
> case L-labels are present.. (alternative 1)
>
>                      PHP
>                    -------->
> +------------+                  +------------+
> |  T-labels  |                  |  L-label   |
> +------------+                  +------------+
> |  L-label   |                  | d-pw label |
> +------------+                  +------------+
> | d-pw label |                  |            |
> +------------+                  |  Payload   |
> |            |                  |            |
> |  Payload   |                  +------------+
> |            |
> +------------+
>
> case no L-labels.. (alternative 2.. and also alternative 3 if you 
> think T- and L-labels are the same)
>
>                      PHP
>                    -------->
> +------------+                  +------------+
> |  T-labels  |                  | d-pw label |
> +------------+                  +------------+
> | d-pw label |                  |            |
> +------------+                  |  Payload   |
> |            |                  |            |
> |  Payload   |                  +------------+
> |            |
> +------------+
>
>
>
>
>
> - Jouni
>

-- 


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