Re: [L3sm] New Version Notification for draft-wu-l3sm-rfc8049bis-02.txt

[David Ball <[e-mail]>]

Thanks Qin, I think most of the comments are being addressed.  Some 
responses below, I've snipped out the ones where we have agreement.


On 21/08/2017 07:47, Qin Wu wrote:
>
> > 2. In section 6.3, I think we can add a statement like: "Multiple locations can be 
> associated
>
> >     with a single site, but a particular location cannot be associated with more 
> than one site."
>
> >    (Personally I don't see the need for this restriction, but this sentence is based 
> on the
>
> >      previous discussion).
>
> We will not be making this change (which seems consistent with your 
> view). A location is a description of a physical location, while a 
> site is part of a service (i.e., a CE). There is no reason to prohibit 
> a service having two co-located CEs. And, of course, two different 
> services could have sites at a single location.
>

[DB]
Ok - in that case, for clarity, can we make the opposite statement: 
"Multiple locations can be associated with a single site; similarly, a 
particular location can be associated with more than one site."

[Note: I came to the conclusion above based on the previous discussion 
about SubVPN, where you said site-network-accesses in different sites 
couldn't share physical components because different sites would be 
associated with different locations.  If multiple sites are allowed to 
be associated with the same location, then they could also share some 
physical components, right?]

> > 3. Section 6.3.2.2.1: I don't think we concluded on whether or not there is a 
> valid use
>
> >    case whereby only IPv6 link-local addresses are used for the site-network-access IP
>
> >    addressing, and no other addresses.  Currently this can't be represented in the
>
> >    model - should it be?  If so, then a sixth option for address-allocation-type 
> needs to
>
> >    be added, for "link-local-only".  Otherwise, we can ignore it.
>
> We think this is covered under "static-address".
>
> If a need for a further classification it can be added in the future.
>

[DB]
Ok

> > 9. In section 6.12.2.2, the second paragraph needs to be updated (or
>
> >     deleted?) now that you have added the "direction" leaf.
>
> We don't believe there is anything actually incorrect about the 
> current text.
>

[DB]
Ok, in that case I don't understand it. :)  Suppose there is a 
provider-managed connection with a qos-profile, and the direction in the 
qos profile is set to Site-to-WAN.  The second paragraph says: "the 
provider should ensure scheduling according to the requested policy in 
both traffic directions", but the description of the direction says: 
"used to specify the direction which qos profile is applied to".  Since 
the direction is Site-to-WAN in this example, this means the profile 
would only be applied in that direction, not in both directions.  That 
seems to contradict the previous text that says it should be applied in 
both directions?

> > 12. The value carried in the svc-mtu leaf is now described more clearly, but its 
> intended
>
> >     use is still unclear, at least to me.  Would something like the following be 
> correct?  If
>
> >     not, what is the correct expression of how to interpret this leaf?
>
> >    "For a given VPN service, the service provider may discard (or for IPv4, may fragment)
>
> >     packets that are longer than the smallest svc-mtu across all 
> site-network-accesses for
>
> >     all sites in the VPN."
>
> We think that SPs are used to the concept of link MTU. svc-mtu 
> modifies the link MTU for the site-access links within the scope of a 
> particular service. We think that an SP will know exactly how to 
> handle packets that exceed MTU values
>

[DB]
Ok, so the intent is that this is just local to the 
site-network-access.  I.e. we could say: "Packets transmitted over the 
site-network-access that are longer than the svc-mtu may be discarded 
(or for IPv4, fragmented)."

> > 13. In the new filters container, there is a list of filters indexed by type (ipv4, 
> ipv6,
>
> >     lan-tag, or vpn-policy-filter-type).  Each filter contains a leaf-list of IPv4 
> prefixes,
>
> >     a leaf-list of ipv6 prefixes and a leaf-list of lan-tags.  Is the intent that the 
> contents
>
> >     of the filter matches the type?  There is nothing to enforce that currently 
> - should
>
> >     there be a "when" statement for each leaf-list, to restrict it to only the case
>
> >     where the type is appropriate (e.g. the ipv4-lan-prefix leaf-list would have
>
> >     "when ../type = ipv4")?
>
> >     I don't really understand what this new filter list achieves over having a single
>
> >     filter that could contain a mix of ipv4 prefixes, ipv6 prefixes and lan-tags.  What's
>
> >     the advantage of 3 filters each containing a single type over one filter 
> containing
>
> >     all three types?
>
> RFC 8049 allowed multiple filters of any one type, but not a mix of 
> filters of different types. That's now fixed.
>

[DB]
Right, I was comparing to the previous version of 8049bis rather than to 
RFC8049 (which I agree did not allow a mix of prefixes and LAN tags).

With the new version, you could have data like this:

<filters>
   <filter>
     <type>lan</type>
<ipv4-lan-prefix>10.0.0.0/24</ipv4-lan-prefix>  // IPv4 prefix specified 
even though type is lan
   </filter>
   <filter>
     <type>ipv4</type>
     <ipv6-lan-prefix>10::0/64</ipv6-lan-prefix>  // IPv6 prefix and lan 
tag specified even though type is ipv4
     <lan-tag>foo</lan-tag>
   </filter>
</filters>

I think the aim could be achieved with a single filter that contains 
leaf-lists for IPv4, Ipv6 and lan tags, i.e.:

container filter {
   leaf-list ipv4-lan-prefix { type inet:ipv4-prefix; }
   leaf-list ipv6-lan-prefix { type inet:ipv6-prefix; }
   leaf-list lan-tag { type string; }
}

This allows full flexibility, i.e. a filter can have zero or more IPv4 
prefixes, zero or more IPv6 prefixes and zero or more LAN tags.

> > 14. As no-one can remember why BFD can only be specified on site-network-accesses
>
> >    and not on sites, I suggest allowing both options - i.e. move the "oam" 
> container from
>
> >    "grouping site-attachment-ip-connection" to "grouping site-routing"; or better 
> still,
>
> >     move it to its own grouping, and use that grouping in both site-top-level-cfg and
>
> >    site-network-access-top-level-cfg.
>
> While this seems to offer a reduction in configuration in some cases 
> while still allowing the detailed configuration, we don't believe 
> there is much of a saving and don't think this change needs to be made.
>

[DB]
Ok.

>
> > 15. For the site-network-access connection addressing, ip-connection/ipv4/address-
>
> >   allocation-type is optional with no default, but 
> ip-connection/ipv6/address-allocation-
>
> >    type has a default defined (static-addressing).  This means it's impossible to 
> have a
>
> >   site-network-access that only uses IPv4 addressing.  I think the 
> default should be
>
> >    deleted in the IPv6 case, so that an IPv4-only site-network-access could be
>
> >    represented by simply not setting the IPv6 address-allocation-type.
>
> Good catch, to get consistent with original RFC8049, I would propose 
> to add the default for ipv4-only site-network-access as well.
>
> Note that we use "feature" for both ipv4 case and ipv6 case.
>

[DB]
Using "feature" doesn't solve the problem, since that turns IPv4 or IPv6 
on or off for every service.  However, the SP might have some IPv4-only 
services and some IPv6-only services.  So, they need to advertise both 
features, but they also need a way to not specify an IPv6 connection 
address for the IPv4-only services, and to not specify an IPv4 
connection address for the IPv6-only services.
So, I believe the best solution is to delete the default for the 
address-allocation-type in both cases.


     David


> Thanks for your time and effort.
>
> Qin
>
> On 09/08/2017 11:40, Qin Wu wrote:
>
>     Here is the update to draft-wu-l3sm-rfc8049bis-02 based on
>     additional discussion on the list.
>
>     https://www.ietf.org/internet-drafts/draft-wu-l3sm-rfc8049bis-02.txt
>
>     Thank David for additional comments. Thank Design team to help
>     address these comments.
>
>     The main changes include:
>
>     1.Clarify the rational of the model in the section 5 based on
>     David's comment.
>
>     2.Add multi-filter and multi-VPN per entry support for VPN policy.
>
>     3.Modify description for svc-input-bandwidth leaf and svc-output-
>
>     Bandwidth leaf to address inconsistency issue with the text in
>     section 6.12.1.
>
>     4. Add text to clarify the way to achieve Per-VPN QoS policy.
>
>     5. Remove address-scope-type since there is no common
>     understanding on this.
>
>     6. Modify the description of autonomous-system under container
>     “BGP” to address David's comment on AS.
>
>     Regarding provider address and mask to the model for the DHCP and
>     DHCP relay cases, talking with design team members,
>
>     We believe these parameters are the one requested by Customer to
>     Provider and therefore we keep it in the model.
>
>     Regarding Number of BGP sessions, eBGP multihop between loopbacks
>     and other similar issue, The design team agreed that it is not
>
>     reasonable to enumerate all the cases this models doesn't support.
>     The current text has been clear about this.
>
>     We believe that we have address all the comments. Thanks!
>
>     -Qin
>
>     -----邮件原件-----
>
>     发件人: [e-mail] <mailto:[e-mail]>
>     [mailto:[e-mail]]
>
>     发送时间: 2017年8月9日18:20
>
>     收件人: Qin Wu; Luis Tomotaki; Kenichi Ogaki; Stephane Litkowski
>
>     主题: New Version Notification for draft-wu-l3sm-rfc8049bis-02.txt
>
>     A new version of I-D, draft-wu-l3sm-rfc8049bis-02.txt has been
>     successfully submitted by Qin Wu and posted to the IETF repository.
>
>     Name:            draft-wu-l3sm-rfc8049bis
>
>     Revision: 02
>
>     Title:           YANG Data Model for L3VPN Service Delivery
>
>     Document date:   2017-08-09
>
>     Group:           Individual Submission
>
>     Pages:           181
>
>     URL:
>     https://www.ietf.org/internet-drafts/draft-wu-l3sm-rfc8049bis-02.txt
>
>     Status: https://datatracker.ietf.org/doc/draft-wu-l3sm-rfc8049bis/
>
>     Htmlized: https://tools.ietf.org/html/draft-wu-l3sm-rfc8049bis-02
>
>     Htmlized:
>     https://datatracker.ietf.org/doc/html/draft-wu-l3sm-rfc8049bis-02
>
>     Diff: https://www.ietf.org/rfcdiff?url2=draft-wu-l3sm-rfc8049bis-02
>
>     Abstract:
>
>        This document defines a YANG data model that can be used for
>
>        communication between customers and network operators and to
>     deliver
>
>        a Layer 3 provider-provisioned VPN service.  This document is
>     limited
>
>        to BGP PE-based VPNs as described in RFCs 4026, 4110, and
>     4364.  This
>
>        model is intended to be instantiated at the management system to
>
>        deliver the overall service.  It is not a configuration model to be
>
>        used directly on network elements.  This model provides an
>     abstracted
>
>        view of the Layer 3 IP VPN service configuration components. 
>     It will
>
>        be up to the management system to take this model as input and use
>
>        specific configuration models to configure the different network
>
>        elements to deliver the service.  How the configuration of network
>
>        elements is done is out of scope for this document.
>
>        If approved, this document obsoletes RFC 8049.  The changes are a
>
>        series of small fixes to the YANG module, and some
>     clarifications to
>
>        the text.
>
>     Please note that it may take a couple of minutes from the time of
>     submission until the htmlized version and diff are available at
>     tools.ietf.org.
>
>     The IETF Secretariat
>
>     _______________________________________________
>
>     L3sm mailing list
>
>     [e-mail] <mailto:[e-mail]>
>
>     https://www.ietf.org/mailman/listinfo/l3sm
>
>
>
> -- 
> David Ball
> <[e-mail]> <mailto:[e-mail]>

-- 
David Ball
<[e-mail]>