Re: [netmod] [802.1 - 12909] IETF Sub-interface VLAN YANG Data Models - draft-ietf-netmod-sub-intf-vlan-model-04

[Robert Wilton <[e-mail]>]

Hi John, Lou,

Thank you both for your comments and helping to get the necessary 
visibility and review from 802.1 WG.

On 13/11/2018 07:03, Lou Berger wrote:
> Hi John,
>
>     Thank you (and Janos, the group) for the agenda time and the 
> message.  There was also a request for a single c-type vlan example.  
> I see that there is already one on page 22 as part of the match 
> container.

I will add an explicit example for a single tag L3 sub-interface c-vlan 
match as well.

>
> See below for inline responses.
>
> Rob/WG,
>     The plan is to address the comments raised in this mail, update 
> the draft and then go to LC.  Please note that the document status 
> should be changed Informational to Standards Track.

OK.


>
> On 11/13/2018 11:55 AM, John Messenger wrote:
>> Hi,
>>
>> At the 802.1 TSN meeting this morning, Lou Berger made a presentation 
>> on behalf of Rob Wilton summarising the recent changes in this 
>> draft.  I like the changes to the structure which are intended to 
>> align the VLAN tag structure to that specified in 802.1Q.  I notice 
>> that the draft retains clause 2.2 (Extensibility) but I think that's 
>> a bug, because it's not reflected in the model (which is a fixed 
>> structure of one or two tags).
> I agree.

I agree, I think that this section can be deleted.


>> Right now, it says that the Ethertypes are taken from 
>> dot1q-tag-type.  Would this allow tags other than 802.1QTagType 
>> (81-00) and 802.1QSTagType (88-A8)?  That shouldn't be allowed.
> I read this as just trying to use the IEEE defined types.  We 
> certainly can restrict this to just c-vlan and s-vlan values, but 
> perhaps you want to consider defining an enumeration for this case 
> (valid-qtag-types).
>
> Rob (wg)
>
>     Do you see any issue with restricting tag-types to 
> dot1q-types:c-vlan and dot1q-types:s-vlan?
I quite like the model being tied to the IEEE defined type and 
associated identities, that only currently defines "c-vlan" and 
"s-vlan".  However, since they are identities it is possible for anyone 
to augment new identities in new YANG modules.

We could block other types by using must statements.  In fact, in the 
case that they are double tagged then the model already enforces that 
outer-tag is s-vlan and inner-tag is c-vlan.  So covering the single tag 
case also makes sense.


>
>> My preference would be to remove the forward-looking statement quoted 
>> here because it implies a willingness to extend to 3 tags:
>>     The structure of the model is currently limited to matching or
>>     rewriting a maximum of two 802.1Q tags in the frame header but has
>>     been designed to be easily extensible to matching/rewriting three or
>>     more VLAN tags in future, if required.
>
> sure. (at least from my perspective.)

Agreed.  This statement is now wrong and should be removed.


>
>> It looks like you could parse an untagged frame as either :(untagged) 
>> or :(dot1q-vlan-tagged) (without either of the optional tags).  Is 
>> that a bug?

Yes, that is a bug.  I will fix this.  dot1q-vlan-tagged should only be 
allowed to match on outer-tag or outer-tag & second-tag.  So, I probably 
need to mark outer-tag as mandatory.

Thanks again for your help.

I'll post an updated draft shortly.

Thanks,
Rob


>
> I may be missing something, but I think you're right - i,e., why would 
> dot1q-vlan-tagged be present without an outer-tag, but I may be 
> missing something...
>
> Thanks again.
>
> Lou
>
>> Thanks,
>>     -- John
>>
>> -----Original Message-----
>> From: List HELP only <[e-mail]> On Behalf Of Robert 
>> Wilton
>> Sent: 05 November 2018 16:16
>> To: [e-mail]
>> Subject: [802.1 - 12909] IETF Sub-interface VLAN YANG Data Models - 
>> draft-ietf-netmod-sub-intf-vlan-model-04
>>
>> Ballot due Nov. 6: P802.1Qcx/D0.4
>> For particulars see
>>    https://1.ieee802.org/active-ballots/
>> 802.1 list help: https://1.ieee802.org/email-lists/
>> List archives (access-controlled) by date:
>>                 www.ieee802.org/1/private/email2/mail1.html
>> -----
>>
>> Dear esteemed 802.1 WG members,
>>
>> A few years back, at the start of my IETF and IEEE standards journey 
>> I wrote a draft defining a sub-interface based VLAN termination YANG 
>> model.  After discussion and presentations in both IETF NETMOD WG and 
>> IEEE 802.1 WG, there was a general agreement that it would be 
>> acceptable for IETF to publish this YANG model as an informational 
>> RFC, with the acknowledgement that 802.1Q VLAN technology is owned by 
>> IEEE, and in future the IEEE 802.1 WG may choose to publish a VLAN 
>> termination model.
>>
>> As part of that IETF NETMOD WG process, and after IEEE 802.1 WG had 
>> reviewed the model, I made a small change in structure of the YANG 
>> model with the sole aim of making the model simpler to use. In 
>> particular, the older model required a slightly clunky indexed list 
>> of VLAN tags, and that is replaced with a simpler structure 
>> supporting two explicit named VLAN tags ('outer-tag' and 
>> 'second-tag').  A while back, Glenn requested that I pass these 
>> changes by the IEEE 802.1 WG to ensure that the changes are 
>> acceptable to the IEEE 802.1 WG, hence this email.
>>
>> The change is perhaps best illustrated via the following change in 
>> the YANG tree output.
>>
>> The*older format* of the YANG model (that members of the 802.1Q WG 
>> previously saw) was like this:
>>
>> *if-cmn:encaps-type: +--:(vlan) +--rw vlan +--rw tags +--rw tag* [index]
>> +--rw index uint8 +--rw dot1q-tag +--rw tag-type dot1q-tag-type +--rw
>> vlan-id dot1q-vlan-id*
>>
>> The *updated format *of YANG model in the current draft is like this:
>>
>>          +--:(dot1q-vlan)
>>             +--rw dot1q-vlan
>>                +--rw outer-tag!
>>                |  +--rw tag-type    dot1q-tag-type
>>                |  +--rw vlan-id     ieee:vlanid
>>                +--rw second-tag!
>>                   +--rw tag-type    dot1q-tag-type
>>                   +--rw vlan-id     ieee:vlanid
>>
>> The same equivalent change has been made for L2 sub-interfaces as well.
>>
>> The latest internet draft is
>> https://tools.ietf.org/html/draft-ietf-netmod-sub-intf-vlan-model-04
>>
>> In particular, it may also be useful to look at the instance data
>> examples in chapter 7, that give a couple of examples of how the YANG
>> model is expected to be used both for L3 termination, and also when used
>> in conjunction with the IETF L2VPN YANG model to provision a
>> point-to-point L2 service.
>>
>> I hope to submit this draft to the NETMOD WG chairs for WG last call
>> after the current IETF 103 meeting.  So if anyone has any concerns then
>> please may I ask that you raise them.  ideally I would like to get them
>> informally addressed before this document progresses. Alternatively if
>> you need more time to review this change, or need this as a formal
>> liaison then please let me know, and I'll do my best.
>>
>> Thank you for your time,
>> Rob Wilton
>>
>>
>> ===
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> .
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