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

[Loa Andersson <[e-mail]>]

Yuanlong,


On 2017-02-25 18:02, Jiangyuanlong wrote:
> 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.

If you do that the S-PE will swap the d-pw, packets will come in from
two different directions with differnt d-pws to the egress, and there
is no way for the egress to identify packets to eliminate.

/Loa
and the egress will have no way

> [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]