Internet DRAFT - draft-ietf-mboned-dorms
draft-ietf-mboned-dorms
Mboned J. Holland
Internet-Draft Akamai Technologies, Inc.
Intended status: Standards Track 7 March 2022
Expires: 8 September 2022
Discovery Of Restconf Metadata for Source-specific multicast
draft-ietf-mboned-dorms-04
Abstract
This document defines DORMS (Discovery Of Restconf Metadata for
Source-specific multicast), a method to discover and retrieve
extensible metadata about source-specific multicast channels using
RESTCONF. The reverse IP DNS zone for a multicast sender's IP
address is configured to use SRV resource records to advertise the
hostname of a RESTCONF server that publishes metadata according to a
new YANG module with support for extensions. A new service name and
the new YANG module are defined.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 8 September 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
Holland Expires 8 September 2022 [Page 1]
Internet-Draft DORMS March 2022
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Motivation and Use Cases . . . . . . . . . . . . . . . . 5
1.3.1. Provisioning and Oversubscription Protection . . . . 5
1.3.2. Authentication . . . . . . . . . . . . . . . . . . . 5
1.3.3. Content Description . . . . . . . . . . . . . . . . . 5
1.4. Channel Discovery . . . . . . . . . . . . . . . . . . . . 5
1.5. Notes for Contributors and Reviewers . . . . . . . . . . 6
1.5.1. Venues for Contribution and Discussion . . . . . . . 6
1.5.2. Non-obvious doc choices . . . . . . . . . . . . . . . 7
2. Discovery and Metdata Retrieval . . . . . . . . . . . . . . . 7
2.1. DNS Bootstrap . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Ignore List . . . . . . . . . . . . . . . . . . . . . . . 9
2.3. RESTCONF Bootstrap . . . . . . . . . . . . . . . . . . . 9
2.3.1. Root Resource Discovery . . . . . . . . . . . . . . . 9
2.3.2. Yang Library Version . . . . . . . . . . . . . . . . 10
2.3.3. Yang Library Contents . . . . . . . . . . . . . . . . 11
2.3.4. Metadata Retrieval . . . . . . . . . . . . . . . . . 12
2.3.5. Cross Origin Resource Sharing (CORS) . . . . . . . . 13
3. Scalability Considerations . . . . . . . . . . . . . . . . . 13
3.1. Provisioning . . . . . . . . . . . . . . . . . . . . . . 13
3.2. Data Scoping . . . . . . . . . . . . . . . . . . . . . . 13
4. YANG Model . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1. Yang Tree . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2. Yang Module . . . . . . . . . . . . . . . . . . . . . . . 14
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16
5.1. Linking Content to Traffic Streams . . . . . . . . . . . 17
5.2. Linking Multicast Subscribers to Unicast Connections . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
6.1. The YANG Module Names Registry . . . . . . . . . . . . . 17
6.2. The XML Registry . . . . . . . . . . . . . . . . . . . . 18
6.3. The Service Name and Transport Protocol Port Number
Registry . . . . . . . . . . . . . . . . . . . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18
7.1. YANG Model Considerations . . . . . . . . . . . . . . . . 18
7.2. Exposure of Metadata . . . . . . . . . . . . . . . . . . 20
Holland Expires 8 September 2022 [Page 2]
Internet-Draft DORMS March 2022
7.3. Secure Communications . . . . . . . . . . . . . . . . . . 20
7.4. Record-Spoofing . . . . . . . . . . . . . . . . . . . . . 21
7.5. CORS considerations . . . . . . . . . . . . . . . . . . . 21
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
9.1. Normative References . . . . . . . . . . . . . . . . . . 22
9.2. Informative References . . . . . . . . . . . . . . . . . 24
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
This document defines DORMS (Discovery Of Restconf Metadata for
Source-specific multicast).
A DORMS service is a RESTCONF [RFC8040] service that provides read
access to data in the "ietf-dorms" YANG [RFC7950] model defined in
Section 4. This model, along with optional extensions defined in
other documents, provide an extensible set of information about
multicast data streams. A review of some example use cases that can
be enabled by this kind of metadata is given in Section 1.3.
This document does not prohibit the use of the "ietf-dorms" model
with other protocols such as NETCONF [RFC6241], CORECONF
[I-D.draft-ietf-core-comi], or gNMI
[I-D.draft-openconfig-rtgwg-gnmi-spec], but the semantics of using
the model over those protocols is out of scope for this document.
This document only defines the discovery and use of the "ietf-dorms"
YANG model in RESTCONF.
This document defines the "dorms" service name for use with the SRV
DNS Resource Record (RR) type [RFC2782]. A sender using a DORMS
service to publish metadata SHOULD configure at least one SRV RR for
the "_dorms._tcp" subdomain in the reverse IP DNS zone for the source
IP used by some active multicast traffic. The domain name in one of
these SRV records provides a hostname corresponding to a DORMS server
that can provide metadata for the sender's source-specific multicast
traffic. Publishing such a RR enables DORMS clients to discover and
query a DORMS server as described in Section 2.
1.1. Background
The reader is assumed to be familiar with the basic DNS concepts
described in [RFC1034], [RFC1035], and the subsequent documents that
update them, as well as the use of the SRV Resource Record type as
described in [RFC2782].
Holland Expires 8 September 2022 [Page 3]
Internet-Draft DORMS March 2022
The reader is also assumed to be familiar with the concepts and
terminology regarding source-specific multicast as described in
[RFC4607] and the use of IGMPv3 [RFC3376] and MLDv2 [RFC3810] for
group management of source-specific multicast channels, as described
in [RFC4604].
The reader is also assumed to be familiar with the concepts and
terminology for RESTCONF [RFC8040] and YANG [RFC7950].
1.2. Terminology
+========+=================================================+
| Term | Definition |
+========+=================================================+
| (S,G) | A source-specific multicast channel, as |
| | described in [RFC4607]. A pair of IP addresses |
| | with a source host IP and destination group IP. |
+--------+-------------------------------------------------+
| DORMS | An application or system that can communicate |
| client | with DORMS servers to fetch metadata about |
| | (S,G)s. |
+--------+-------------------------------------------------+
| DORMS | A RESTCONF server that implements the ietf- |
| server | dorms YANG model defined in this document. |
+--------+-------------------------------------------------+
| RR | A DNS Resource Record, as described in |
| | [RFC1034] |
+--------+-------------------------------------------------+
| RRType | A DNS Resource Record Type, as described in |
| | [RFC1034] |
+--------+-------------------------------------------------+
| SSM | Source-specific multicast, as described in |
| | [RFC4607] |
+--------+-------------------------------------------------+
Table 1
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119] and [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Holland Expires 8 September 2022 [Page 4]
Internet-Draft DORMS March 2022
1.3. Motivation and Use Cases
DORMS provides a framework that can be extended to publish
supplemental information about multicast traffic in a globally
discoverable manner. This supplemental information is sometimes
needed by entities engaged in delivery or processing of the traffic
to handle the traffic according to their requirements.
Detailing the specifics of all known possible extensions is out of
scope for this document except to note that a range of possible use
cases are expected and they may be supported by a variety of
different future extensions. But a few example use cases are
provided below for illustration.
1.3.1. Provisioning and Oversubscription Protection
One use case for DORMS is when a network that is capable of
forwarding multicast traffic may need to take provisioning actions or
make admission control decisions based on the expected bitrate of the
traffic in order to prevent oversubscription of constrained devices
in the network. [I-D.draft-ietf-mboned-cbacc] defines some DORMS
extensions to support this use case.
1.3.2. Authentication
Another use case for DORMS is providing information for use in
authenticating the multicast traffic before accepting it for
forwarding by a network device, or for processing by a receiving
application. [I-D.draft-ietf-mboned-ambi] defines some DORMS
extensions to support this use case.
1.3.3. Content Description
Another use case for DORMS is describing the contents carried by a
multicast traffic channel. The content description could include
information about the protocols or applications that can be used to
consume the traffic, or information about the media carried (e.g.
information based on the Dublin Core Metadata Element Set [RFC5013]),
or could make assertions about the legal status of the traffic within
specific contexts.
1.4. Channel Discovery
DORMS provides a method for clients to fetch metadata about (S,G)s
that are already known to the clients. In general, a DORMS client
might learn of an (S,G) by any means, so describing all possible
methods a DORMS client might use to discover a set of (S,G)s for
which it wants metadata is out of scope for this document.
Holland Expires 8 September 2022 [Page 5]
Internet-Draft DORMS March 2022
But for example, a multicast receiver application that is a DORMS
client might learn about an (S,G) by getting signals from inside the
application logic, such as a selection made by a user, or a scheduled
API call that reacts to updates in a library provided by a service
operator.
As another example, an on-path router that's a DORMS client might
instead learn about an (S,G) by receiving a PIM message or an IGMP or
MLD membership report indicating a downstream client has tried to
subscribe to an (S,G). Such a router might use information learned
from the DORMS metadata to make an access control decision about
whether to propagate the join futher upstream in the network.
Other approaches for learning relevant (S,G)s could be driven by
monitoring a route reflector to discover channels that are being
actively forwarded, for a purpose such as monitoring network health.
1.5. Notes for Contributors and Reviewers
Note to RFC Editor: Please remove this section and its subsections
before publication.
This section is to provide references to make it easier to review the
development and discussion on the draft so far.
1.5.1. Venues for Contribution and Discussion
This document is in the Github repository at:
https://github.com/GrumpyOldTroll/ietf-dorms-cluster
Readers are welcome to open issues and send pull requests for this
document.
Please note that contributions may be merged and substantially
edited, and as a reminder, please carefully consider the Note Well
before contributing: https://datatracker.ietf.org/submit/note-well/
Substantial discussion of this document should take place on the
MBONED working group mailing list (mboned@ietf.org).
* Join: https://www.ietf.org/mailman/listinfo/mboned
* Search: https://mailarchive.ietf.org/arch/browse/mboned/
Holland Expires 8 September 2022 [Page 6]
Internet-Draft DORMS March 2022
1.5.2. Non-obvious doc choices
Log of odd things that need to be the way they are because of some
reason that the author or reviewers may want to know later.
* building the draft without this line produces a warning about no
reference to [RFC6991] or [RFC8294], but these are imported in the
yang model. RFC 8407 requires the normative reference to 8294
(there's an exception for 6991 but I'm not sure why and it doesn't
seem forbidden).
* Although it's non-normative, I chose the boundaries in the
recommendation for default setting of DNS expiry time in
Section 2.2 based on the best practices advice at
https://www.varonis.com/blog/dns-ttl/ for "Short" and "Long"
times.
* Section 7.1 is intended to be the template from
https://trac.ietf.org/trac/ops/wiki/yang-security-guidelines
(https://trac.ietf.org/trac/ops/wiki/yang-security-guidelines), as
required by https://datatracker.ietf.org/doc/html/rfc8407#section-
3.7 (https://datatracker.ietf.org/doc/html/rfc8407#section-3.7).
Individual nodes are not listed because blanket statements in that
section covere them.
* The 'must' constraint in the group list seems awkward, but seems
to work. Its intent is to require source & group to be either
both IPv4 or both IPv6, without mixing & matching. It requires
that either both the group address and its source parent's address
must contain a colon or both must NOT contain a colon, where
presence of a colon is used to distinguish IPv4 from IPv6. Maybe
there's a better way?
2. Discovery and Metdata Retrieval
A client that needs metadata about an (S,G) MAY attempt to discover
metadata for the (S,G) using the mechanisms defined here, and MAY use
the metadata received to manage the forwarding or processing of the
packets in the channel.
2.1. DNS Bootstrap
The DNS Bootstrap step is how a client discovers an appropriate
RESTCONF server, given the source address of an (S,G). Use of the
DNS Bootstrap is OPTIONAL for clients with an alternate method of
obtaining a hostname of a trusted DORMS server that has information
about a target (S,G).
Holland Expires 8 September 2022 [Page 7]
Internet-Draft DORMS March 2022
This mechanism only works for source-specific multicast (SSM)
channels. The source address of the (S,G) is reversed and used as an
index into one of the reverse mapping trees (in-addr.arpa for IPv4,
as described in Section 3.5 of [RFC1035], or ip6.arpa for IPv6, as
described in Section 2.5 of [RFC3596]).
When a DORMS client needs metadata for an (S,G), for example when
handling a new join for that (S,G) and looking up the authentication
methods that are available, the DORMS client can issue a DNS query
for a SRV RR using the "dorms" service name with the domain from the
reverse mapping tree, combining them as described in [RFC2782].
For example, a client looking for metadata about the channel with a
source IP of 2001:db8::a and the group address of ff3e::8000:d, the
client would start the DNS bootstrap step by performing a query for
the SRV RRType for the following domain (after removing the line
break inserted for editorial reasons):
_dorms._tcp.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
Or for an IPv4 (S,G) with a source address of 203.0.113.4, the DORMS
client would request the SRV record from the in-addr.arpa tree
instead:
_dorms._tcp.4.113.0.203.in-addr.arpa.
In either case, the DNS response for this domain might return a
record such as this:
SRV 0 1 443 dorms-restconf.example.com.
This response informs the client that a DORMS server should be
reachable at dorms-restconf.example.com on port 443, and should
contain metadata about multicast traffic from the given source IP.
Multiple SRV records are handled as described by [RFC2782].
A sender providing DORMS discovery SHOULD publish at least one SRV
record in the reverse DNS zone for each source address of the
multicast channels it is sending in order to advertise the hostname
of the DORMS server to DORMS clients. The DORMS servers advertised
SHOULD be configured with metadata for all the groups sent from the
same source IP address that have metadata published with DORMS.
When performing the SRV lookup, any CNAMEs or DNAMEs found MUST be
followed. This is necessary to support zone delegation. Some
examples outlining this need are described in [RFC2317].
Holland Expires 8 September 2022 [Page 8]
Internet-Draft DORMS March 2022
2.2. Ignore List
If a DORMS client reaches a DORMS server but determines through
examination of responses from that DORMS server that it may not
understand or be able to use the responses of the server (for example
due to an issue like a version mismatch or modules that are missing
but are required for the DORMS client's purposes), the client MAY add
this server to an ignore list and reject servers in its ignore list
during future discovery attempts.
A client using the DNS Bootstrap discovery method in Section 2.1
would treat servers in its ignore list as unreachable for the
purposes of processing the SRV RR as described in [RFC2782]. (For
example, a client might end up selecting a server with a less-
preferred priority than servers in its ignore list, even if an HTTPS
connection could have been formed successfully with some of those
servers.)
If an ignore list is maintained, entries SHOULD time out and allow
for re-checking after either the cache expiration time from the DNS
response that caused the server to be added to the ignore list, or
for a configurable hold-down time that has a default value no shorter
than 1 hour and no longer than 24 hours.
2.3. RESTCONF Bootstrap
Once a DORMS server has been chosen (whether via an SRV RR from a DNS
response or via some other method), RESTCONF provides all the
information necessary to determine the versions and url paths for
metadata from the server. A walkthrough is provided here for a
sequence of example requests and responses from a receiver connecting
to a new DORMS server.
2.3.1. Root Resource Discovery
As described in Section 3.1 of [RFC8040] and [RFC6415], the RESTCONF
server provides the link to the RESTCONF api entry point via the
"/.well-known/host-meta" or "/.well-known/host-meta.json" resource.
Example:
The receiver might send:
GET /.well-known/host-meta.json HTTP/1.1
Host: dorms-restconf.example.com
Accept: application/json
The server might respond as follows:
Holland Expires 8 September 2022 [Page 9]
Internet-Draft DORMS March 2022
HTTP/1.1 200 OK
Date: Tue, 09 Jul 2021 20:56:00 GMT
Server: example-server
Cache-Control: no-cache
Content-Type: application/json
{
"links":[
{
"rel":"restconf",
"href":"/top/restconf"
}
]
}
2.3.2. Yang Library Version
As described in Section 3.3.3 of [RFC8040], the yang-library-version
leaf is required by RESTCONF, and can be used to determine the schema
of the ietf-yang-library module:
Example:
The receiver might send:
GET /top/restconf/yang-library-version HTTP/1.1
Host: dorms-restconf.example.com
Accept: application/yang-data+json
The server might respond as follows:
HTTP/1.1 200 OK
Date: Tue, 09 Jul 2021 20:56:01 GMT
Server: example-server
Cache-Control: no-cache
Content-Type: application/yang-data+json
{
"ietf-restconf:yang-library-version": "2016-06-21"
}
If a DORMS client determines through examination of the yang-library-
version that it may not understand the responses of the server due to
a version mismatch, the server qualifies as a candidate for adding to
an ignore list as described in Section 2.2.
Holland Expires 8 September 2022 [Page 10]
Internet-Draft DORMS March 2022
2.3.3. Yang Library Contents
After checking that the version of the yang-library module will be
understood by the receiver, the client can check that the desired
metadata modules are available on the DORMS server by fetching the
module-state resource from the ietf-yang-library module.
Example:
The receiver might send:
GET /top/restconf/data/ietf-yang-library:modules-state/\
module=ietf-dorms,2021-07-08
Host: dorms-restconf.example.com
Accept: application/yang-data+json
The server might respond as follows:
HTTP/1.1 200 OK
Date: Tue, 09 Jul 2021 20:56:02 GMT
Server: example-server
Cache-Control: no-cache
Content-Type: application/yang-data+json
{
"ietf-yang-library:module": [
{
"conformance-type": "implement",
"name": "ietf-dorms",
"namespace": "urn:ietf:params:xml:ns:yang:ietf-dorms",
"revision": "2021-07-08",
"schema":
"https://example.com/yang/ietf-dorms@2021-07-08.yang"
}
]
}
Other modules required or desired by the client also can be checked
in a similar way, or the full set of available modules can be
retrieved by not providing a key for the "module" list. If a DORMS
client that requires the presence of certain modules to perform its
function discovers the required modules are not present on a server,
that server qualifies for inclusion in an ignore list according to
Section 2.2.
Holland Expires 8 September 2022 [Page 11]
Internet-Draft DORMS March 2022
2.3.4. Metadata Retrieval
Once the expected DORMS version is confirmed, the client can retrieve
the metadata specific to the desired (S,G).
Example:
The receiver might send:
GET /top/restconf/data/ietf-dorms:dorms/metadata/\
sender=2001:db8::a/group=ff3e::8000:1
Host: dorms-restconf.example.com
Accept: application/yang-data+json
The server might respond as follows:
HTTP/1.1 200 OK
Date: Tue, 09 Jul 2021 20:56:02 GMT
Server: example-server
Cache-Control: no-cache
Content-Type: application/yang-data+json
{
"ietf-dorms:group": [
{
"group-address":"ff3e::8000:1",
"udp-stream":[
{
"port":"5001"
}
]
}
]
}
Note that when other modules are installed on the DORMS server that
extend the ietf-dorms module, other fields MAY appear inside the
response. This is the primary mechanism for providing extensible
metadata for an (S,G), so clients SHOULD ignore fields they do not
understand.
As mentioned in Section 3.2, most clients SHOULD use data resource
identifiers in the request URI as in the above example, in order to
retrieve metadata for only the targeted (S,G)s.
Holland Expires 8 September 2022 [Page 12]
Internet-Draft DORMS March 2022
2.3.5. Cross Origin Resource Sharing (CORS)
It is RECOMMENDED that DORMS servers use the Access-Control-Allow-
Origin header field, as specified by [whatwg-fetch], and that they
respond appropriately to Preflight requests.
The use of '*' for allowed origins is NOT RECOMMENDED for publicly
reachable DORMS servers. A review of some of the potential
consequences of unrestricted CORS access is given in Section 7.5.
3. Scalability Considerations
3.1. Provisioning
In contrast to many common RESTCONF deployments that are intended to
provide configuration management for a service to a narrow set of
authenticated administrators, DORMS servers often provide read-only
metadata for public access or for a very large set of end receivers,
since it provides metadata in support of multicast data streams and
multicast can scale to very large audiences.
Operators are advised to provision the DORMS service in a way that
will scale appropriately to the size of the expected audience.
Specific advice on such scaling is out of scope for this document,
but some of the mechanisms outlined in [RFC3040] or other online
resources might be useful, depending on the expected number of
receivers.
3.2. Data Scoping
Except as outlined below, clients SHOULD issue narrowed requests for
DORMS resources by following the format from Section 3.5.3 of
[RFC8040] to encode data resource identifiers in the request URI.
This avoids downloading excessive data, since the DORMS server may
provide metadata for many (S,G)s, possibly from many different
senders.
However, clients with out of band knowledge about the scope of the
expected contents MAY issue requests for (S,G) metadata narrowed only
by the source-address, or not narrowed at all. Depending on the
request patterns and the contents of the data store, this may result
in fewer round trips or less overhead, and can therefore be helpful
behavior for scaling purposes in some scenarios. In general,
engaging in this behavior requires some administrative configuration
or some optimization heuristics that can recover from unexpected
results.
Holland Expires 8 September 2022 [Page 13]
Internet-Draft DORMS March 2022
Servers MAY restrict or throttle client access based on the client
certificate presented (if any), or based on heuristics that take note
of client request patterns.
A complete description of the heuristics for clients and servers to
meet their scalability goals is out of scope for this document.
4. YANG Model
The primary purpose of the YANG model defined here is to serve as a
scaffold for the more useful metadata that will extend it. See
Section 1.3 for some example use cases that can be enabled by the use
of DORMS extensions.
4.1. Yang Tree
The tree diagram below follows the notation defined in [RFC8340].
module: ietf-dorms
+--rw dorms
+--rw metadata
+--rw sender* [source-address]
+--rw source-address inet:ip-address
+--rw group* [group-address]
+--rw group-address
| rt-types:ip-multicast-group-address
+--rw udp-stream* [port]
+--rw port inet:port-number
Figure 1: DORMS Tree Diagram
4.2. Yang Module
<CODE BEGINS>
file ietf-dorms@2022-03-07.yang
module ietf-dorms {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-dorms";
prefix "dorms";
import ietf-inet-types {
prefix "inet";
reference "RFC 6991 Section 4";
}
import ietf-routing-types {
prefix "rt-types";
Holland Expires 8 September 2022 [Page 14]
Internet-Draft DORMS March 2022
reference "RFC 8294";
}
organization "IETF MBONED (Multicast Backbone
Deployment) Working Group";
contact
"Author: Jake Holland
<mailto:jholland@akamai.com>
";
description
"Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
This module contains the definition for the DORMS data type.
It provides out of band metadata about SSM channels.";
revision 2021-07-08 {
description "Draft version, post-early-review.";
reference
"draft-ietf-mboned-dorms";
}
container dorms {
description "Top-level DORMS container.";
container metadata {
description "Metadata scaffold for source-specific multicast
channels.";
list sender {
key source-address;
Holland Expires 8 September 2022 [Page 15]
Internet-Draft DORMS March 2022
description "Sender for DORMS";
leaf source-address {
type inet:ip-address;
mandatory true;
description
"The source IP address of a multicast sender.";
}
list group {
key group-address;
description "Metadata for a DORMS (S,G).";
leaf group-address {
type rt-types:ip-multicast-group-address;
mandatory true;
description "The group IP address for an (S,G).";
}
must '(re-match(./group-address, "[^:]*") and ' +
're-match(../source-address, "[^:]*")) or ' +
'(re-match(./group-address, ".*:.*") and ' +
're-match(../source-address, ".*:.*"))' {
error-message 'A group-address type must match '+
'its parent source-address type';
}
list udp-stream {
key "port";
description
"Metadata for UDP traffic on a specific port.";
leaf port {
type inet:port-number;
mandatory true;
description
"The UDP port of a data stream.";
}
}
}
}
}
}
}
<CODE ENDS>
5. Privacy Considerations
Holland Expires 8 September 2022 [Page 16]
Internet-Draft DORMS March 2022
5.1. Linking Content to Traffic Streams
In the typical case, the mechanisms defined in this document provide
a standardized way to discover information that is already available
in other ways.
However, depending on the metadata provided by the server, observers
may be able to more easily associate traffic from an (S,G) with the
content contained within the (S,G). At the subscriber edge of a
multicast-capable network, where the network operator has the
capability to localize an IGMP [RFC3376] or MLD [RFC3810] channel
subscription to a specific user or location, for example by MAC
address or source IP address, the structured publishing of metadata
may make it easier to automate collection of data about the content a
receiver is consuming.
5.2. Linking Multicast Subscribers to Unicast Connections
Subscription to a multicast channel generally only exposes the IGMP
or MLD membership report to others on the same LAN, and as the
membership propagates through a multicast-capable network, it
ordinarily gets aggregated with other end users.
However, a RESTCONF connection is a unicast connection, and exposes a
different set of information to the operator of the RESTCONF server,
including IP address and timing about the requests made. Where DORMS
access becomes required to succeed a multicast join (for example, as
expected in a browser deployment), this can expose new information
about end users relative to services based solely on multicast
streams. The information disclosure occurs by giving the DORMS
service operator information about the client's IP and the channels
the client queried.
In some deployments it may be possible to use a proxy that aggregates
many end users when the aggregate privacy characteristics are needed
by end users.
6. IANA Considerations
6.1. The YANG Module Names Registry
This document adds one YANG module to the "YANG Module Names"
registry maintained at <https://www.iana.org/assignments/yang-
parameters>. The following registrations are made, per the format in
Section 14 of [RFC6020]:
Holland Expires 8 September 2022 [Page 17]
Internet-Draft DORMS March 2022
name: ietf-dorms
namespace: urn:ietf:params:xml:ns:yang:ietf-dorms
prefix: dorms
reference: I-D.draft-ietf-mboned-dorms
6.2. The XML Registry
This document adds the following registration to the "ns" subregistry
of the "IETF XML Registry" defined in [RFC3688], referencing this
document.
URI: urn:ietf:params:xml:ns:yang:ietf-dorms
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
6.3. The Service Name and Transport Protocol Port Number Registry
This document adds one service name to the "Service Name and
Transport Protocol Port Number Registry" maintained at
<https://www.iana.org/assignments/service-names-port-numbers>. The
following registrations are made, per the format in Section 8.1.1 of
[RFC6335]:
Service Name: dorms
Transport Protocol(s): TCP, UDP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Description: The DORMS service (RESTCONF that
includes ietf-dorms YANG model)
Reference: I-D.draft-ietf-mboned-dorms
Port Number: N/A
Service Code: N/A
Known Unauthorized Uses: N/A
Assignment Notes: N/A
7. Security Considerations
7.1. YANG Model Considerations
The YANG module specified in this document defines a schema for data
that is designed to be accessed via RESTCONF [RFC8040]. The lowest
RESTCONF layer is HTTPS, and the mandatory-to-implement secure
transport is TLS [RFC8446].
There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., config true, which is the
default). These data nodes may be considered sensitive or vulnerable
in some network environments. Write operations (e.g., edit-config)
Holland Expires 8 September 2022 [Page 18]
Internet-Draft DORMS March 2022
to these data nodes without proper protection can have a negative
effect on network operations. These are the subtrees and data nodes
and their sensitivity/vulnerability:
Subtrees:
* /dorms/metadata
* /dorms/metadata/sender
* /dorms/metadata/sender/group
* /dorms/metadata/sender/group/udp-stream
Data nodes:
* /dorms/metadata/sender/source-address
* /dorms/metadata/sender/group/group-address
* /dorms/metadata/sender/group/udp-stream/port
These data nodes refer to the characteristics of a stream of data
packets being sent on a multicast channel. If an unauthorized or
incorrect edit is made, receivers would no longer be able to
associate the data stream to the correct metadata, resulting in a
denial of service for end users that rely on the metadata to properly
process the data packets. Therefore DORMS servers MUST constrain
write access to ensure that unauthorized users cannot edit the data
published by the server.
The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content. DORMS servers MAY use NACM
to constrain write accesses.
However, note that scalability considerations described in
Section 3.1 might make the naive use of NACM intractable in many
deployments, for a broadcast use case. So alternative methods to
constrain write access to the metadata MAY be used instead of or in
addition to NACM. For example, some deployments that use a CDN or
caching layer of discoverable DORMS servers might uniformly provide
read-only access through the caching layer, and might require the
trusted writers of configuration to use an alternate method of
accessing the underlying database such as connecting directly to the
origin, or requiring the use of a non-RESTCONF mechanism for editing
the contents of the metadata.
Holland Expires 8 September 2022 [Page 19]
Internet-Draft DORMS March 2022
The data nodes defined in this YANG module are writable because some
deployments might manage the contents in the database by using normal
RESTCONF editing operations with NACM, but in typical deployments
it's expected that DORMS clients will generally have read-only
access. For the reasons and requirements described in Section 7.2,
none of the data nodes in the DORMS module or its extensions contain
sensitive data.
DORMS servers MAY provide read-only access to clients for publicly
available metadata without authenticating the clients. That is,
under the terms in Section 2.5 of [RFC8040] read-only access to
publicly available data MAY be treated as unprotected resources.
7.2. Exposure of Metadata
Although some DORMS servers MAY restrict access based on client
identity, as described in Section 2.5 of [RFC8040], many DORMS
servers will use the ietf-dorms YANG model to publish information
without restriction, and even DORMS servers requiring client
authentication will inherently, because of the purpose of DORMS, be
providing the DORMS metadata to potentially many receivers.
Accordingly, future YANG modules that augment data paths under "ietf-
dorms:dorms" MUST NOT include any sensitive data unsuitable for
public dissemination in those data paths.
Because of the possibility that scalable read-only access might be
necessary to fulfill the scalability goals for a DORMS server, data
under these paths MAY be cached or replicated by numerous external
entities, so owners of such data SHOULD NOT assume such data can be
kept secret when provided by DORMS servers anywhere under the "ietf-
dorms:dorms" path even if access controls are used with authenticated
clients unless additional operational procedures and restrictions are
defined and implemented that can effectively control the
dissemination of the secret data. DORMS alone does not provide any
such mechanisms, and users of DORMS can be expected not to be
following any such mechanisms in the absence of additional
assurances.
7.3. Secure Communications
The provisions of Section 2 of [RFC8040] provide secure communication
requirements that are already required of DORMS servers, since they
are RESTCONF servers. All RESTCONF requirements and security
considerations remain in force for DORMS servers.
Holland Expires 8 September 2022 [Page 20]
Internet-Draft DORMS March 2022
It is intended that security related metadata about the SSM channels
such as public keys for use with cryptographic algorithms may be
delivered over the RESTCONF connection, and that information
available from this connection can be used as a trust anchor. The
secure transport provided by these minimum requirements are relied
upon to provide authenticated delivery of these trust anchors, once a
connection with a trusted DORMS server has been established.
7.4. Record-Spoofing
When using the DNS Boostrap method of discovery described in
Section 2.1, the SRV resource record contains information that SHOULD
be communicated to the DORMS client without being modified. The
method used to ensure the result was unmodified is up to the client.
There must be a trust relationship between the end consumer of this
resource record and the DNS server. This relationship may be end-to-
end DNSSEC validation or a secure connection to a trusted DNS server
that provides end-to-end safety to prevent record-spoofing of the
response from the trusted server. The connection to the trusted
server can use any secure channel, such as with a TSIG [RFC8945] or
SIG(0) [RFC2931] channel, a secure local channel on the host, DNS
over TLS [RFC7858], DNS over HTTPS [RFC8484], or some other mechanism
that provides authentication of the RR.
If a DORMS client accepts a maliciously crafted SRV record, the
client could connect to a server controlled by the attacker, and use
metadata provided by them. The consequences of trusting maliciously
crafted metadata could range from attacks against the DORMS client's
parser of the metadata (via malicious constructions of the formatting
of the data) to arbitrary disruption of the decisions the DORMS
client makes as a result of processing validly constructed metadata.
Clients MAY use other secure methods to explicitly associate an (S,G)
with a set of DORMS server hostnames, such as a configured mapping or
an alternative trusted lookup service.
7.5. CORS considerations
As described in Section 2.3.5, it's RECOMMENDED that DORMS servers
provide appropriate restrictions to ensure only authorized web pages
access metadata for their (S,G)s from the widely deployed base of
secure browsers that use the CORS protocol according to
[whatwg-fetch].
Holland Expires 8 September 2022 [Page 21]
Internet-Draft DORMS March 2022
Providing '*' for the allowed origins exposes the DORMS-based
metadata to access by scripts in all web pages, which opens the
possibility of certain kinds of attacks against networks where
browsers have support for joining multicast (S,G)s.
If the authentication for an (S,G) relies on DORMS-based metadata
(for example, as defined in [I-D.draft-ietf-mboned-ambi]), an
unauthorized web page that tries to join an (S,G) not permitted by
the CORS headers for the DORMS server will be prevented from
subscribing to the channels.
If an unauthorized site is not prevented from subscribing, code on
the site (for example a malicious advertisement) could request
subscriptions from many different (S,G)s, overflowing limits on the
joining of (S,G)s and disrupting the delivery of multicast traffic
for legitimate use.
Further, if the malicious script can be distributed to many different
users within the same receiving network, the script could coordinate
an attack against the network as a whole by joining disjoint sets of
(S,G)s from different users within the receiving network. The
distributed subscription requests across the receiving network could
overflow limits for the receiving network as a whole, essentially
causing the websites displaying the ad to participate in an
overjoining attack (see Appendix A of [I-D.draft-ietf-mboned-cbacc]).
Even if network safety mechanisms protect the network from the worst
effects of oversubscription, the population counts for the multicast
subscriptions could be disrupted by this kind of attack, and
therefore push out legitimately requested traffic that's being
consumed by real users. For a legitimately popular event, this could
cause a widespread disruption to the service if it's successfully
pushed out.
A denial of service attack of this sort would be thwarted by
restricting the access to (S,G)s to authorized websites through the
use of properly restricted CORS headers.
8. Acknowledgements
Thanks to Christian Worm Mortensen, Dino Farinacci, Lenny Guiliano,
and Reshad Rahman for their very helpful comments and reviews.
9. References
9.1. Normative References
Holland Expires 8 September 2022 [Page 22]
Internet-Draft DORMS March 2022
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2317] Eidnes, H., de Groot, G., and P. Vixie, "Classless IN-
ADDR.ARPA delegation", BCP 20, RFC 2317,
DOI 10.17487/RFC2317, March 1998,
<https://www.rfc-editor.org/info/rfc2317>.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
DOI 10.17487/RFC2782, February 2000,
<https://www.rfc-editor.org/info/rfc2782>.
[RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
"DNS Extensions to Support IP Version 6", STD 88,
RFC 3596, DOI 10.17487/RFC3596, October 2003,
<https://www.rfc-editor.org/info/rfc3596>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8294] Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger,
"Common YANG Data Types for the Routing Area", RFC 8294,
DOI 10.17487/RFC8294, December 2017,
<https://www.rfc-editor.org/info/rfc8294>.
Holland Expires 8 September 2022 [Page 23]
Internet-Draft DORMS March 2022
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[whatwg-fetch]
"WHATWG Fetch Living Standard", October 2020,
<https://fetch.spec.whatwg.org/>.
9.2. Informative References
[I-D.draft-ietf-core-comi]
Veillette, M., Stok, P. V. D., Pelov, A., Bierman, A., and
I. Petrov, "CoAP Management Interface (CORECONF)", Work in
Progress, Internet-Draft, draft-ietf-core-comi-11, 17
January 2021, <https://www.ietf.org/archive/id/draft-ietf-
core-comi-11.txt>.
[I-D.draft-ietf-mboned-ambi]
Holland, J. and K. Rose, "Asymmetric Manifest Based
Integrity", Work in Progress, Internet-Draft, draft-ietf-
mboned-ambi-01, 31 October 2020,
<https://www.ietf.org/archive/id/draft-ietf-mboned-ambi-
01.txt>.
[I-D.draft-ietf-mboned-cbacc]
Holland, J., "Circuit Breaker Assisted Congestion
Control", Work in Progress, Internet-Draft, draft-ietf-
mboned-cbacc-02, 1 February 2021,
<https://www.ietf.org/archive/id/draft-ietf-mboned-cbacc-
02.txt>.
[I-D.draft-openconfig-rtgwg-gnmi-spec]
Shakir, R., Shaikh, A., Borman, P., Hines, M., Lebsack,
C., and C. Morrow, "gRPC Network Management Interface
(gNMI)", Work in Progress, Internet-Draft, draft-
openconfig-rtgwg-gnmi-spec-01, 5 March 2018,
<https://www.ietf.org/archive/id/draft-openconfig-rtgwg-
gnmi-spec-01.txt>.
Holland Expires 8 September 2022 [Page 24]
Internet-Draft DORMS March 2022
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures
( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
2000, <https://www.rfc-editor.org/info/rfc2931>.
[RFC3040] Cooper, I., Melve, I., and G. Tomlinson, "Internet Web
Replication and Caching Taxonomy", RFC 3040,
DOI 10.17487/RFC3040, January 2001,
<https://www.rfc-editor.org/info/rfc3040>.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, DOI 10.17487/RFC3376, October 2002,
<https://www.rfc-editor.org/info/rfc3376>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
DOI 10.17487/RFC3810, June 2004,
<https://www.rfc-editor.org/info/rfc3810>.
[RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Protocol Version 2 (MLDv2) for Source-
Specific Multicast", RFC 4604, DOI 10.17487/RFC4604,
August 2006, <https://www.rfc-editor.org/info/rfc4604>.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
<https://www.rfc-editor.org/info/rfc4607>.
[RFC5013] Kunze, J. and T. Baker, "The Dublin Core Metadata Element
Set", RFC 5013, DOI 10.17487/RFC5013, August 2007,
<https://www.rfc-editor.org/info/rfc5013>.
Holland Expires 8 September 2022 [Page 25]
Internet-Draft DORMS March 2022
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[RFC6415] Hammer-Lahav, E., Ed. and B. Cook, "Web Host Metadata",
RFC 6415, DOI 10.17487/RFC6415, October 2011,
<https://www.rfc-editor.org/info/rfc6415>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
[RFC8945] Dupont, F., Morris, S., Vixie, P., Eastlake 3rd, D.,
Gudmundsson, O., and B. Wellington, "Secret Key
Transaction Authentication for DNS (TSIG)", STD 93,
RFC 8945, DOI 10.17487/RFC8945, November 2020,
<https://www.rfc-editor.org/info/rfc8945>.
Author's Address
Jake Holland
Akamai Technologies, Inc.
150 Broadway
Cambridge, MA 02144,
United States of America
Email: jakeholland.net@gmail.com
Holland Expires 8 September 2022 [Page 26]
