Re: [PWE3] WG Poll on draft-jin-pwe3-cbit-negotiation-03.txt ( comment )

[[e-mail]]

Luca,
After discussing with the authors, we decide to add the wait for label 
release before sending label request, this wouldn't harm and bring some 
secure.

Then are you OK with the following text?

When Local PE changes its control word from NOT PREFERRED to PREFERRED and 
only if it already received the remote label mapping message with C-bit=0, 
additional procedure will be added as follow:
-i Local PE MUST send a label withdraw message to remote PE if it has 
previously sent a label mapping, and wait until receiving a label release 
from the remote PE.
-ii Local PE MUST send a label request message to remote PE, and wait 
until receiving a label mapping message containing the remote PE 
configured control word setting.
-iii After receiving remote PE label mapping with control word setting, 
Local PE MUST follow procedures defined in [RFC4447] section 6 when 
sending it's label mapping message.

Correspondingly, the modified procedure of PE in figure 1 will be as 
follows:

1. PE2 changes locally configured control word to PREFERRED. 
2. PE2 will then send label withdraw message to PE1. 
3. PE1 MUST send label release in reply to label withdraw message from 
PE2. 
4. Upon receipt of Label release message from PE1, PE2 MUST send label 
request messages to PE1 although it already received the label mapping 
with C-bit=0. 
5. PE1 MUST send label mapping message with C-bit=1 again to PE2 (Note: 
PE1 MUST send label mapping with locally configured CW parameter). 
6. PE2 receives the label mapping from PE1 and updates the remote label 
binding information. PE2 MUST wait for PE1 label binding before sending 
its label binding with C-bit set, only if it previously had a label 
binding with C-bit = 0 from PE1. 
7. PE2 will send label mapping to PE1 with C-bit=1. 

It is to be noted that the above assume that PE1 is configured to support 
CW, however in step 5 if PE1 doesn't support CW, PE1 would send the label 
mapping message with C-bit =0, this would result in PE2 in step 7 sending 
a label mapping with C-bit=0 as per [RFC4447] CW negotiation procedure.

Thanks
Lizhong


------------send by Luca 
Martini-------------------------------------------
Matthew & Andy,


Although I support clarifying this procedure , I believe this document
needs some work.
In section 3 for example :

   When Local PE changes its control word from NOT PREFERRED to
   PREFERRED and only if it already received the remote label mapping
   message with C-bit=0, additional procedure will be added as follow:

         -i. Local PE sends label withdraw message to the remote if it
             already sends label mapping message, for it has changed its
             control word parameter.

        -ii. Local PE MUST send a label request messages to peer PE to
             get peer's configured control word parameter before sending
             new label mapping message to peer PE.

       -iii. After receiving the new label mapping message from peer PE
             and updating the remote label binding information, the
             Local PE should send label mapping to peer PE according to
             procedures defined in [RFC4447].

What does the item i) mean ? the English is not clear.
Why does the PE have to do ii) ?

All we really need is a statement on how the c-bit negotiation state
machine can be reset if one end has changed "his mind" .

Can we fix this document before  issuing the -00 WG draft version ?

Thanks.
Luca
 

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