Re: [OPSAWG] Benjamin Kaduk's No Objection on draft-ietf-opsawg-vpn-common-10: (with COMMENT)

[[e-mail]]

Hi Ben, 

Thank you for the review. The changes to address your review can be tracked at: https://github.com/IETF-OPSAWG-WG/lxnm/commit/108707e8b2aea6590b0a9695756c7546887c9614 

Please see inline. 

Cheers,
Med

> -----Message d'origine-----
> De : Benjamin Kaduk via Datatracker [mailto:[e-mail]]
> Envoyé : mercredi 22 septembre 2021 06:19
> À : The IESG <[e-mail]>
> Cc : [e-mail]; [e-mail];
> [e-mail]; [e-mail]; [e-mail]
> Objet : Benjamin Kaduk's No Objection on draft-ietf-opsawg-vpn-common-
> 10: (with COMMENT)
> 
> Benjamin Kaduk has entered the following ballot position for
> draft-ietf-opsawg-vpn-common-10: No Objection
> 
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> 
> Please refer to https://www.ietf.org/blog/handling-iesg-ballot-
> positions/
> for more information about how to handle DISCUSS and COMMENT positions.
> 
> 
> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-opsawg-vpn-common/
> 
> 
> 
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
> 
> I have a bold proposal for consideration: since we are defining a new
> common set of groupings for VPN and, in some cases, proposing to rename
> existing terminology already, can we consider moving away from the term
> "VPN" itself?  The word "private" is ambiguous as to what level of
> privacy is being provided (e.g., network routing vs cryptographic) and
> who the conveyed content is to be private from.  A term like "virtual
> network" removes that ambiguity, and lets us use the explicit attributes
> to convey whether encryption is in use when appropriate.
> 
> There is no particular triggering point (at least, not yet) at which it
> becomes clearly correct to make a breaking change like this, so we may
> end up just having to pick a time somewhat arbitrarily, if we are to
> make such a change at all.  Perhaps now is that time; perhaps not.

[[Med]] I hear some of your observations but VPN is a well-established name for a widely deployed technology. I don't think it is a good idea to touch this. Please note that there is already generic model for VNs (https://datatracker.ietf.org/doc/draft-ietf-teas-actn-vn-yang/) that is distinct from what we are doing here.

> 
> Section 3
> 
>           grouping vpn-profile-cfg
>             +-- valid-provider-identifiers
>                +-- external-connectivity-identifier* [id]
>                |       {external-connectivity}?
>                |  +-- id?   string
> 
> Presumably I am just misreading RFC 8340, but I thought that the list
> key was implicitly mandatory, so it would appear as just "id" (as
> opposed to "id?").  (Many instances.)

[[Med]] Good question. Actually we trusted what is in Section 3.2 of 8340. That's the output we get from pyang. Note that ? is not displayed when the grouping is used in another model (L2NM/L3NM). Will double check this with Martin.  

> 
>    'vpn-route-targets':
>       *  A YANG grouping that defines Route Target (RT) import/export
>          rules used in a BGP-enabled VPN (e.g., [RFC4364][RFC4664]).
> 
> On very quick skim, it's not clear what motivates the RFC 4664 reference
> -- "route target" does not appear, for example, nor does "import" or
> "export".

[[Med]] This is just to insist that it can be used for both L3 and L2VPNs. Unlike L3NM, there are plenty L2VPN technologies; hence the choice to point to a generic L2 framework.

> 
> Section 4
> 
>      identity pim-proto {
>        if-feature "pim";
>        base routing-protocol-type;
> 
> This is in the section with the group-management-protocols; is "routing-
> protocol-type" really the intended base?

[[Med]] Yes. Both PIM and other group management protocols fall under:

  /*
   * Identities related to multicast
   */ 

> 
>      identity embb {
>      [...]
>      identity urllc {
>      [...]
>      identity mmtc {
> 
> Similar to Roman's comment, a reference seems useful for these.
> If we intend to implicitly rely on RFCs 8299 and/or 8466 for
> terminology, we should say so in the terminology section.

[[Med]] Added this note under the terminology section:

   The document inherits many terms from [RFC8299] and [RFC8466]
   (e.g., Enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low
   Latency Communications (URLLC), Massive Machine Type Communications
   (mMTC)).

> 
>        leaf vpn-id {
>          type vpn-common:vpn-id;
>          description
>            "A VPN identifier that uniquely identifies a VPN.
>             This identifier has a local meaning, e.g., within
>             a service provider network.";
> 
> Thank you for indicating the scope of validity of the identifier!
> (Elsewhere as well.)
> 
>      grouping service-status {
>        [...]
>            leaf last-change {
>              type yang:date-and-time;
>              description
>                "Indicates the actual date and time of the service status
>                 change.";
> 
> What's the motiviation behind leaving this as "config true"?  When would
> it be useful to set it manually?

[[Med]] This can be set, for example, when a new administrative status is set. 

> 
>        list vpn-target {
>          [...]
>          leaf id {
>            type int8;
>            description
>              "Identifies each VPN Target.";
> 
> I wasn't able to find the motivation for limiting to int8 in RFC 4364,
> though I mostly assume I'm just looking in the wrong place.

[[Med]] I confirm that there is no such concept in 4364. The intuitive design would be to use leaf-list, but the reason for having this is a list with an id is recorded in this note:

         Note that this is modelled as a list to ease the reuse of this
         grouping in modules where a pointer is needed (e.g., associate
         an operator with RTs).

We don't see the need to go beyond uint8. As illustrated, for example, in L3NM a typical usage of this would be simply:

==
                         "vpn-targets": {
                           "vpn-target": [
                             {
                               "id": "1",
                               "route-targets": [
                                 "0:65550:1"
                               ],
                               "route-target-type": "both"
                             }
                           ]
                         }
==

> (But why *signed* int8?)

[[Med]] This should be unsigned. Fixed. 

> 
> Section 5
> 
> While there may be no direct security considerations from what is
> effectively just defining some new compound types for reuse, I think we
> may want to consider some privacy considerations.  For example, we have
> the "customer-name" field in the vpn-description, and it is sometimes
> the case that customers want to remain confidential.  Thus, any
> instantiations of the grouping would incur a potential need for
> confidentiality and minimizing the scope of distribution.
> 

[[Med]] We do already discuss this for example in the L3NM. No problem to add a note here as well. I added this NEW text:

   Modules that use the groupings that are defined in this document
   should identify the corresponding security considerations.  For
   example, reusing some of these groupings will expose privacy-related
   information (e.g., customer-name).  Disclosing such information may
   be considered as a violation of the customer-provider trust
   relationship. 


> NITS
> 
> Section 4
> 
>      feature bearer-reference {
>        description
>          "Indicates support for the bearer reference access constraint.
>           That is, the reuse of a network connection that was already
>           ordered to the service provider apart from the IP VPN site.";
> 
> I echo Roman's comment that this feature would benefit from a reference
> or further discussion; the current description leaves me unclear on what
> is meant and with no recourse for learning more.  (RFCs 4026 and 4176
> are presented as generic references for VPN-related terms, but do not
> cover the concept of "bearer reference".)

[[Med]] The description is basically echoing RFC8299: 

==
   o  The "bearer-reference" parameter is used in cases where the
      customer has already ordered a network connection to the SP apart
      from the IP VPN site and wants to reuse this connection.
== 

We can update the description to first introduce the concept of bearer:

      "A bearer refers to properties of the CE-PE attachment that
       are below Layer 3.

> 
>        reference
>          "I-D.ietf-teas-ietf-network-slice-framework:
>             Framework for IETF Network Slices";
> 
> draft-ietf-teas-ietf-network-slice-framework is replaced by draft-ietf-
> teas-ietf-network-slices.

[[Med]] Shame on me as I'm contributing to that work :-( Fixed. Thanks.

> 
>      identity rsvp-te {
>        base protocol-type;
>        description
>          "Transport is based on RSVP-TE.";
>        reference
>          "RFC 3209: RSVP-TE: Extensions to RSVP for LSP Tunnels";
> 
> Is the transport itself RSVP-TE, or is it that RSVP-TE is used to
> provision the tunnels used as transport?  (Similar question for bgp-lu?)

[[Med]] This means "relies upon" to setup the underlay transport. 

OLD:
  Transport is based on
NEW:
 Transport setup relies upon

> 
>      identity dot1q {
>        if-feature "dot1q";
>        base encapsulation-type;
>        description
>          "Dot1q encapsulation.";
> 
> I suppose the feature declaration does so, but maybe some "802" is in
> order here as well?

[[Med]] We didn't as we though this is redundant with the reference under the dot1q feature:

    reference
      "IEEE Std 802.1Q: Bridges and Bridged Networks"; 

> 
>      identity ethernet-type {
>        base encapsulation-type;
>        description
>          "Ethernet encapsulation type.";
>      }
> 
>      identity vlan-type {
>        base encapsulation-type;
>        description
>          "VLAN encapsulation.";
>      }
> 
>      identity untagged-int {
>        base encapsulation-type;
>        description
>          "Untagged interface type.";
>      [...]
> 
> Should we be more consistent about whether the description ends in
> "type"?

[[Med]] Indeed. Fixed. 

> 
>      identity lag-int {
>        if-feature "lag-interface";
>        base encapsulation-type;
>        description
>          "LAG interface type.";
>        reference
>          "IEEE Std. 802.1AX: Link Aggregation";
> 
> lag-int is the only encapsulation-type identify element that has a
> reference stanza.  We did mention LAG in the context of 802.1AX earlier,
> so maybe it's not needed?

[[Med]] Right. We should be consistent. 

> 
>      identity web {
>        base customer-application;
>        description
>          "Web applications (e.g., HTTP, HTTPS).";
>      [...]
>      identity file-transfer {
>        base customer-application;
>        description
>          "File transfer application (e.g., FTP, SFTP).";
> 
> Maybe we could just list HTTPS and SFTP as the (respective) examples, in
> 2021?

[[Med]] These are only examples. I tend to keep the same description as in RFC8299 as this is related to the customer traffic. 

> 
>        leaf vpn-name {
>          type string;
>          description
>            "A name used to refer to the VPN.";
> 
> Should we say a little more about how the name differs from the id,
> given that both are "type string"?

[[Med]] The main difference is provided as part of the "id" description: the id is what is used to uniquely identify the VPN. 

That's said, I updated the description for better clarity as follows: 

NEW:
        "A name used to associate a name with the service
         in order to facilitate the identification of 
         the service";

> 
>          leaf import-policy {
>            type string;
>            description
>              "Defines the 'import' policy.";
>          }
>          leaf export-policy {
>            type string;
>            description
>              "Defines the 'export' policy.";
> 
> Does it "define" or merely "identify" the policy?  Naively, a
> "definition" would be a rather long string...

[[Med]] "identifies" is more appropriate. Fixed. 

> 
>      grouping vpn-components-group {
>        [...]
>        container groups {
>          description
>            "Lists the groups to which a VPN node,a site, or a network
> 
> space after comma.
> 
> 

[[Med]] Fixed. Thank you. 

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