Re: [netmod] A few comments on draft-dbb-netmod-acl

[[e-mail]]

Hi Qin,

Thanks for the comments.

Please see inline.

Cheers,
Med

De : netmod <[e-mail]> De la part de Qin Wu
Envoyé : jeudi 27 octobre 2022 08:08
À : [e-mail]
Objet : [netmod] A few comments on draft-dbb-netmod-acl

Hi, Oscar:
I have read the latest version of draft-dbb-netmod-acl, the problem statement and gap analysis are interesting, here are a few comments on this draft:
1.For problem statement in section 4.3 and section 4.5, I am wondering how  do you feel encrypted traffic at the transport layer, e.g., TLS layer or QUIC layer,
I feel it is hard, you might read one of presentation slides for IAB MTEN workshop, one gap we identify is ACL fall short to deal with encrypted traffic.

[Med] I guess this falls under a match-based on the payload:

==

3.7.  Payload-based Filtering



   Some transport protocols use existing protocols (e.g., TCP or UDP) as

   substrate.  The match criteria for such protocols may rely upon the

   'protocol' under 'l3', TCP/UDP match criteria, part of the TCP/UDP

   payload, or a combination thereof.  [RFC8519] does not support

   matching based on the payload.



   Likewise, the current version of the ACL model does not support

   filtering of encapsulated traffic.
===

The full augmentation is


     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace

               /ietf-acl:matches:

       +--rw (payload)?

          +--:(prefix-pattern)

             +--rw prefix-pattern {match-on-payload}?

                +--rw offset?       identityref

                +--rw offset-end?   uint64

                +--rw operator?     operator

                +--rw prefix?       binary


Please let us know if you think this does not address the case you have in mind. Thanks.

But for unencrypted traffic, yes, the ACL extension provide fine granularity access control.

2.For section 3.2, I feel the solution seems not complete, how defined set is used, in the match, it lack a example to explain how it is used.

[Med] We will consider adding more examples, but the defined sets can be called under the l3/l4 match conditions. Here is, for example, how a set can be referenced under l3/ipv4:


     augment /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace

               /ietf-acl:matches/ietf-acl:l3/ietf-acl:ipv4:

       +--rw next-header-set?                leafref


3.For section 3.1, it is a good extension, but I understand the idea is to apply the same action to a set of prefixes, let's say two prefixes, since the destination-ipv6-network is defined as an array, I am wondering whether the action should be changes into 2 actions in an array:

[Med] Not sure to get this comment. The proposal is to have the same action for all the addresses in a set/list.

   {
     "ietf-access-control-list:acls": {
       "acl": [
         {
           "name": "prefix-list-support",
           "type": "ipv6-acl-type",
           "aces": {
             "ace": [
               {
                 "name": "my-test-ace",
                 "matches": {
                   "ipv6": {
                     "destination-ipv6-network": [
                       "2001:db8:6401:1::/64",
                       "2001:db8:6401:c::/64"
                     ],
                     "source-ipv6-network":
                       "2001:db8:1234::/96",
                     "protocol": 17,
                     "flow-label": 10000
                   },
                 },
                 "actions": {
                   "forwarding": [ "accept","accept"]
                 }
               }
             ]
           }
         }
       ]
     }
   }
Maybe one alternative solution is to use template, if we want to Manipulate Lists of Prefixes

4.I feel flags defined in RFC9519 is confusing, how does the controller know which packet is the last fragment, which packet is not, which packet needs to be fragmented, which one not,the fragment action is controlled by the ingress node, configuring flags seems wrong to me.
[Med] Agree that the handling of flags in 8519 is problematic. The draft includes examples how to fix this and align with other tools such as flow spec.

5. For section 3.3 "Bind ACLs to Devices, Not Only Interfaces", do we have solution to this problem? If not, I think draft-ma-opsawg-ucl-acl-00 provide excatly the solution you are looking for if my understanding is correct, to address the limitation of IP address based access control, no need to tie to the specific interface of the device, or a single device.

[Med] No solution is included for 3.3 because we think that it will be better addressed in a network model, not a device model. Also, agree that draft-ma-opsawg-ucl-acl is a good candidate. Thanks.

-Qin

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