Subject: [Softwires] New version of draft-ietf-softwire-yang posted

From: Ian Farrer <[email-masked]>
Date: Mon, 30 Oct 2017 16:12:22 +0100

Hi,

I’ve just posted an updated version of draft-ietf-softwire-yang. This has taken quite some time to produce and is quite a significant update from -01.

The most notable changes in this version:

1, There are now 3 models as this follows intended function much more cleanly than the previous approach:
* CE Model (MAP-E/T, lw4o6)
* BR Model (MAP-E/T, lw4o6)
* Common Model (groupings of functions used by CE and BR)

2, The CE model is now structured to work with the ietf-interfaces YANG model - the softwire is defined as config for building a tunnel interface. This allows us to use it for getting necessary configuration described in other models such as ietf-routing. It is also in line with the way that the tunnel interface is configured in CE devices.

3, Where there is duplication, configuration nodes have been removed in favour of referencing other YANG models - e.g. referencing ietf-nat for NAT and PSID configuration in the CE.

4, Better descriptions, improved counters and a lot of other little fix ups.

One question that the authors have been discussing is the approach to defining ‘binding’ type softwires (lw4o6, MAP EA=0). This is the current, relevant text in Sec 2:

Within the BR and CE modules, the YANG "feature" statement is used to
distinguish which of the different softwire mechanism(s) is relevant	
for a specific element's configuraiton.  For each module, a choice
statement is included for either 'binding' or 'algorithmic'.  Binding
is used for configuring Lightweight 4over6, whereas Algorithmic is
used for configuring MAP-T or MAP-E.

+---------------------+-----------+---------------+
|    S46 Mechanism    |  ce-type? |  data-plane?  |
+---------------------+-----------+---------------+
|  Lightweight 4over6 |  binding  |      n/a      |
|        MAP-E        | algorithm | encapsulation |
|        MAP-T        | algorithm |  translation  |
+---------------------+-----------+---------------+

A proposed change is to cover the ‘binding’ cases of MAP configuration here as well - a suggestion for how this section could read is:

Within the BR and CE modules, the YANG "feature" statement is used to	 	   
distinguish which of the different softwire mechanism(s) is relevant	 	   	
for a specific element's configuraiton.  For each module, a choice	 	  	
statement is included for either 'binding' or 'algorithmic'.  Binding	 	   	
is used for configuring Lightweight 4over6 or MAP with EA=0 (with or	 	   	
without PSID) softwires (described in [RFC7597] Appendix A Examples 4	 	   	
and 5).  Algorithmic is used for MAP-T or MAP-E 'mesh' (EA>0, no	 		
PSID) configuration.

+-------------------------------+-----------+---------------+ 	                    
|         S46 Mechanism         |  ce-type? |  data-plane?  |	 	            	
+-------------------------------+-----------+---------------+	 	           	
| Lightweight 4over6 / MAP EA=0 |  binding  |      n/a      |	 	            	
|           MAP-E Mesh          | algorithm | encapsulation |	 	            	
|           MAP-T Mesh          | algorithm |  translation  |	 	           	
+-------------------------------+-----------+---------------+	 	            

Obviously, if we were to go this way, then other parts of the draft would need to be updated in line.

As ever, any comments, suggestions etc. appreciated.

Thanks,
Ian