Internet Engineering Task Force (IETF) B. Stark

Internet Engineering Task Force (IETF) B. Stark
Request for Comments: 9046 AT&T
Category: Informational M. Jethanandani
ISSN: 2070-1721 Kloud Services
June 2021

Babel Information Model

Abstract

The Babel information model provides structured data elements for a
Babel implementation reporting its current state and may allow
limited configuration of some such data elements. This information
model can be used as a basis for creating data models under various
data modeling regimes. This information model only includes
parameters and parameter values useful for managing Babel over IPv6.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9046.

Copyright Notice

Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.

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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction
1.1. Requirements Language
1.2. Notation
2. Overview
3. The Information Model
3.1. Definition of babel-information-obj
3.2. Definition of babel-constants-obj
3.3. Definition of babel-interface-obj
3.4. Definition of babel-if-stats-obj
3.5. Definition of babel-neighbor-obj
3.6. Definition of babel-route-obj
3.7. Definition of babel-mac-key-set-obj
3.8. Definition of babel-mac-key-obj
3.9. Definition of babel-dtls-cert-set-obj
3.10. Definition of babel-dtls-cert-obj
4. Extending the Information Model
5. Security Considerations
6. IANA Considerations
7. References
7.1. Normative References
7.2. Informative References
Acknowledgements
Authors' Addresses

1. Introduction

Babel is a loop-avoiding, distance-vector routing protocol defined in
[RFC8966]. [RFC8967] defines a security mechanism that allows Babel
packets to be cryptographically authenticated, and [RFC8968] defines
a security mechanism that allows Babel packets to be both
authenticated and encrypted. This document describes an information
model for Babel (including implementations using one or both of these
security mechanisms) that can be used to create management protocol
data models (such as a NETCONF [RFC6241] YANG [RFC7950] data model).

Due to the simplicity of the Babel protocol, most of the information
model is focused on reporting the Babel protocol operational state,
and very little of that is considered mandatory to implement for an
implementation claiming compliance with this information model. Some
parameters may be configurable. However, it is up to the Babel
implementation whether to allow any of these to be configured within
its implementation. Where the implementation does not allow
configuration of these parameters, it MAY still choose to expose them
as read-only.

The information model is presented using a hierarchical structure.
This does not preclude a data model based on this information model
from using a referential or other structure.

This information model only includes parameters and parameter values
useful for managing Babel over IPv6. This model has no parameters or
values specific to operating Babel over IPv4, even though [RFC8966]
does define a multicast group for sending and listening to multicast
announcements on IPv4. There is less likelihood of breakage due to
inconsistent configuration and increased implementation simplicity if
Babel is operated always and only over IPv6. Running Babel over IPv6
requires IPv6 at the link layer and does not need advertised
prefixes, router advertisements, or DHCPv6 to be present in the
network. Link-local IPv6 is widely supported among devices where
Babel is expected to be used. Note that Babel over IPv6 can be used
for configuration of both IPv4 and IPv6 routes.

1.1. Requirements Language

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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

1.2. Notation

This document uses a programming-language-like notation to define the
properties of the objects of the information model. An optional
property is enclosed by square brackets, [ ], and a list property is
indicated by two numbers in angle brackets, <m..n>, where m indicates
the minimal number of list elements, and n indicates the maximum
number of list elements. The symbol "*" for n means there are no
defined limits on the number of list elements. Each parameter and
object includes an indication of "ro" or "rw". "ro" means the
parameter or object is read-only. "rw" means it is read-write. For
an object, read-write means instances of the object can be created or
deleted. If an implementation is allowed to choose to implement a
"rw" parameter as read-only, this is noted in the parameter
description.

The object definitions use base types that are defined as follows:

binary: A binary string (sequence of octets).

boolean: A type representing a Boolean (true or false) value.

datetime: A type representing a date and time using the Gregorian
calendar. The datetime format MUST conform to
[RFC3339], Section 5.6.

ip-address: A type representing an IP address. This type supports
both IPv4 and IPv6 addresses.

operation: A type representing a remote procedure call or other
action that can be used to manipulate data elements or
system behaviors.

reference: A type representing a reference to another information
or data model element or to some other device resource.

string: A type representing a human-readable string consisting
of a (possibly restricted) subset of Unicode and ISO/
IEC 10646 [ISO.10646] characters.

uint: A type representing an unsigned integer number. This
information model does not define a precision.

2. Overview

The information model is hierarchically structured as follows:

+-- babel-information
+-- babel-implementation-version
+-- babel-enable
+-- router-id
+-- self-seqno
+-- babel-metric-comp-algorithms
+-- babel-security-supported
+-- babel-mac-algorithms
+-- babel-dtls-cert-types
+-- babel-stats-enable
+-- babel-stats-reset
+-- babel-constants
| +-- babel-udp-port
| +-- babel-mcast-group
+-- babel-interfaces
| +-- babel-interface-reference
| +-- babel-interface-enable
| +-- babel-interface-metric-algorithm
| +-- babel-interface-split-horizon
| +-- babel-mcast-hello-seqno
| +-- babel-mcast-hello-interval
| +-- babel-update-interval
| +-- babel-mac-enable
| +-- babel-if-mac-key-sets
| +-- babel-mac-verify
| +-- babel-dtls-enable
| +-- babel-if-dtls-cert-sets
| +-- babel-dtls-cached-info
| +-- babel-dtls-cert-prefer
| +-- babel-packet-log-enable
| +-- babel-packet-log
| +-- babel-if-stats
| | +-- babel-sent-mcast-hello
| | +-- babel-sent-mcast-update
| | +-- babel-sent-ucast-hello
| | +-- babel-sent-ucast-update
| | +-- babel-sent-IHU
| | +-- babel-received-packets
| +-- babel-neighbors
| +-- babel-neighbor-address
| +-- babel-hello-mcast-history
| +-- babel-hello-ucast-history
| +-- babel-txcost
| +-- babel-exp-mcast-hello-seqno
| +-- babel-exp-ucast-hello-seqno
| +-- babel-ucast-hello-seqno
| +-- babel-ucast-hello-interval
| +-- babel-rxcost
| +-- babel-cost
+-- babel-routes
| +-- babel-route-prefix
| +-- babel-route-prefix-length
| +-- babel-route-router-id
| +-- babel-route-neighbor
| +-- babel-route-received-metric
| +-- babel-route-calculated-metric
| +-- babel-route-seqno
| +-- babel-route-next-hop
| +-- babel-route-feasible
| +-- babel-route-selected
+-- babel-mac-key-sets
| +-- babel-mac-default-apply
| +-- babel-mac-keys
| +-- babel-mac-key-name
| +-- babel-mac-key-use-send
| +-- babel-mac-key-use-verify
| +-- babel-mac-key-value
| +-- babel-mac-key-algorithm
| +-- babel-mac-key-test
+-- babel-dtls-cert-sets
+-- babel-dtls-default-apply
+-- babel-dtls-certs
+-- babel-cert-name
+-- babel-cert-value
+-- babel-cert-type
+-- babel-cert-private-key

Most parameters are read-only. The following is a descriptive list
of the parameters that are not required to be read-only:

* enable/disable Babel

* create/delete Babel Message Authentication Code (MAC) Key sets

* create/delete Babel Certificate sets

* enable/disable statistics collection

* Constant: UDP port

* Constant: IPv6 multicast group

* Interface: enable/disable Babel on this interface

* Interface: metric algorithm

* Interface: split horizon

* Interface: sets of MAC keys

* Interface: verify received MAC packets

* Interface: set of certificates for use with DTLS

* Interface: use cached info extensions

* Interface: preferred order of certificate types

* Interface: enable/disable packet log

* MAC-keys: create/delete entries

* MAC-keys: key used for sent packets

* MAC-keys: key used to verify packets

* DTLS-certs: create/delete entries

The following parameters are required to return no value when read:

* MAC key values

* DTLS private keys

Note that this overview is intended simply to be informative and is
not normative. If there is any discrepancy between this overview and
the detailed information model definitions in subsequent sections,
the error is in this overview.

3. The Information Model

3.1. Definition of babel-information-obj

object {
string ro babel-implementation-version;
boolean rw babel-enable;
binary ro babel-self-router-id;
[uint ro babel-self-seqno;]
string ro babel-metric-comp-algorithms<1..*>;
string ro babel-security-supported<0..*>;
[string ro babel-mac-algorithms<1..*>;]
[string ro babel-dtls-cert-types<1..*>;]
[boolean rw babel-stats-enable;]
[operation babel-stats-reset;]
babel-constants-obj ro babel-constants;
babel-interface-obj ro babel-interfaces<0..*>;
babel-route-obj ro babel-routes<0..*>;
[babel-mac-key-set-obj rw babel-mac-key-sets<0..*>;]
[babel-dtls-cert-set-obj rw babel-dtls-cert-sets<0..*>;]
} babel-information-obj;

babel-implementation-version: The name and version of this
implementation of the Babel protocol.

babel-enable: When written, it configures whether the protocol
should be enabled (true) or disabled (false). A read from the
running or intended datastore indicates the configured
administrative value of whether the protocol is enabled (true) or
not (false). A read from the operational datastore indicates
whether the protocol is actually running (true) or not (i.e., it
indicates the operational state of the protocol). A data model
that does not replicate parameters for running and operational
datastores can implement this as two separate parameters. An
implementation MAY choose to expose this parameter as read-only
("ro").

babel-self-router-id: The router-id used by this instance of the
Babel protocol to identify itself. [RFC8966] describes this as an
arbitrary string of 8 octets.

babel-self-seqno: The current sequence number included in route
updates for routes originated by this node. This is a 16-bit
unsigned integer.

babel-metric-comp-algorithms: List of supported cost computation
algorithms. Possible values include "2-out-of-3", as described in
[RFC8966], Appendix A.2.1, and "ETX", as described in [RFC8966],
Appendix A.2.2.

babel-security-supported: List of supported security mechanisms.
Possible values include "MAC" to indicate support of [RFC8967] and
"DTLS" to indicate support of [RFC8968].

babel-mac-algorithms: List of supported MAC computation algorithms.
Possible values include "HMAC-SHA256" and "BLAKE2s-128" to
indicate support for algorithms indicated in [RFC8967].

babel-dtls-cert-types: List of supported certificate types.
Possible values include "X.509" and "RawPublicKey" to indicate
support for types indicated in [RFC8968].

babel-stats-enable: Indicates whether statistics collection is
enabled (true) or disabled (false) on all interfaces. When
enabled, existing statistics values are not cleared and will be
incremented as new packets are counted.

babel-stats-reset: An operation that resets all babel-if-stats
parameters to zero. This operation has no input or output
parameters.

babel-constants: A babel-constants-obj object.

babel-interfaces: A set of babel-interface-obj objects.

babel-routes: A set of babel-route-obj objects. Contains the routes
known to this node.

babel-mac-key-sets: A set of babel-mac-key-set-obj objects. If this
object is implemented, it provides access to parameters related to
the MAC security mechanism. An implementation MAY choose to
expose this object as read-only ("ro").

babel-dtls-cert-sets: A set of babel-dtls-cert-set-obj objects. If
this object is implemented, it provides access to parameters
related to the DTLS security mechanism. An implementation MAY
choose to expose this object as read-only ("ro").

3.2. Definition of babel-constants-obj

object {
uint rw babel-udp-port;
[ip-address rw babel-mcast-group;]
} babel-constants-obj;

babel-udp-port: UDP port for sending and listening for Babel
packets. Default is 6696. An implementation MAY choose to expose
this parameter as read-only ("ro"). This is a 16-bit unsigned
integer.

babel-mcast-group: Multicast group for sending and listening to
multicast announcements on IPv6. Default is ff02::1:6. An
implementation MAY choose to expose this parameter as read-only
("ro").

3.3. Definition of babel-interface-obj

object {
reference ro babel-interface-reference;
[boolean rw babel-interface-enable;]
string rw babel-interface-metric-algorithm;
[boolean rw babel-interface-split-horizon;]
[uint ro babel-mcast-hello-seqno;]
[uint ro babel-mcast-hello-interval;]
[uint ro babel-update-interval;]
[boolean rw babel-mac-enable;]
[reference rw babel-if-mac-key-sets<0..*>;]
[boolean rw babel-mac-verify;]
[boolean rw babel-dtls-enable;]
[reference rw babel-if-dtls-cert-sets<0..*>;]
[boolean rw babel-dtls-cached-info;]
[string rw babel-dtls-cert-prefer<0..*>;]
[boolean rw babel-packet-log-enable;]
[reference ro babel-packet-log;]
[babel-if-stats-obj ro babel-if-stats;]
babel-neighbor-obj ro babel-neighbors<0..*>;
} babel-interface-obj;

babel-interface-reference: Reference to an interface object that can
be used to send and receive IPv6 packets, as defined by the data
model (e.g., YANG [RFC7950] and Broadband Forum (BBF) [TR-181]).
Referencing syntax will be specific to the data model. If there
is no set of interface objects available, this should be a string
that indicates the interface name used by the underlying operating
system.

babel-interface-enable: When written, it configures whether the
protocol should be enabled (true) or disabled (false) on this
interface. A read from the running or intended datastore
indicates the configured administrative value of whether the
protocol is enabled (true) or not (false). A read from the
operational datastore indicates whether the protocol is actually
running (true) or not (i.e., it indicates the operational state of
the protocol). A data model that does not replicate parameters
for running and operational datastores can implement this as two
separate parameters. An implementation MAY choose to expose this
parameter as read-only ("ro").

babel-interface-metric-algorithm: Indicates the metric computation
algorithm used on this interface. The value MUST be one of those
listed in the babel-metric-comp-algorithms parameter. An
implementation MAY choose to expose this parameter as read-only
("ro").

babel-interface-split-horizon: Indicates whether or not the split-
horizon optimization is used when calculating metrics on this
interface. A value of "true" indicates split-horizon optimization
is used. Split-horizon optimization is described in [RFC8966],
Section 3.7.4. An implementation MAY choose to expose this
parameter as read-only ("ro").

babel-mcast-hello-seqno: The current sequence number in use for
multicast Hellos sent on this interface. This is a 16-bit
unsigned integer.

babel-mcast-hello-interval: The current interval in use for
multicast Hellos sent on this interface. Units are centiseconds.
This is a 16-bit unsigned integer.

babel-update-interval: The current interval in use for all updates
(multicast and unicast) sent on this interface. Units are
centiseconds. This is a 16-bit unsigned integer.

babel-mac-enable: Indicates whether the MAC security mechanism is
enabled (true) or disabled (false). An implementation MAY choose
to expose this parameter as read-only ("ro").

babel-if-mac-key-sets: List of references to the babel-mac-key-sets
entries that apply to this interface. When an interface instance
is created, all babel-mac-key-sets instances with babel-mac-
default-apply "true" will be included in this list. An
implementation MAY choose to expose this parameter as read-only
("ro").

babel-mac-verify: A Boolean flag indicating whether MACs in incoming
Babel packets are required to be present and are verified. If
this parameter is "true", incoming packets are required to have a
valid MAC. An implementation MAY choose to expose this parameter
as read-only ("ro").

babel-dtls-enable: Indicates whether the DTLS security mechanism is
enabled (true) or disabled (false). An implementation MAY choose
to expose this parameter as read-only ("ro").

babel-if-dtls-cert-sets: List of references to the babel-dtls-cert-
sets entries that apply to this interface. When an interface
instance is created, all babel-dtls-cert-sets instances with
babel-dtls-default-apply "true" will be included in this list. An
implementation MAY choose to expose this parameter as read-only
("ro").

babel-dtls-cached-info: Indicates whether the cached_info extension
(see [RFC8968], Appendix A) is included in ClientHello and
ServerHello packets. The extension is included if the value is
"true". An implementation MAY choose to expose this parameter as
read-only ("ro").

babel-dtls-cert-prefer: List of supported certificate types, in
order of preference. The values MUST be among those listed in the
babel-dtls-cert-types parameter. This list is used to populate
the server_certificate_type extension (see [RFC8968], Appendix A)
in a ClientHello. Values that are present in at least one
instance in the babel-dtls-certs object of a referenced babel-dtls
instance and that have a non-empty babel-cert-private-key will be
used to populate the client_certificate_type extension in a
ClientHello.

babel-packet-log-enable: Indicates whether packet logging is enabled
(true) or disabled (false) on this interface.

babel-packet-log: A reference or URL link to a file that contains a
timestamped log of packets received and sent on babel-udp-port on
this interface. The [libpcap] file format with a .pcap file
extension SHOULD be supported for packet log files. Logging is
enabled/disabled by babel-packet-log-enable. Implementations will
need to carefully manage and limit memory used by packet logs.

babel-if-stats: Statistics collection object for this interface.

babel-neighbors: A set of babel-neighbor-obj objects.

3.4. Definition of babel-if-stats-obj

object {
uint ro babel-sent-mcast-hello;
uint ro babel-sent-mcast-update;
uint ro babel-sent-ucast-hello;
uint ro babel-sent-ucast-update;
uint ro babel-sent-IHU;
uint ro babel-received-packets;
} babel-if-stats-obj;

babel-sent-mcast-hello: A count of the number of multicast Hello
packets sent on this interface.

babel-sent-mcast-update: A count of the number of multicast update
packets sent on this interface.

babel-sent-ucast-hello: A count of the number of unicast Hello
packets sent on this interface.

babel-sent-ucast-update: A count of the number of unicast update
packets sent on this interface.

babel-sent-IHU: A count of the number of "I Heard You" (IHU) packets
sent on this interface.

babel-received-packets: A count of the number of Babel packets
received on this interface.

3.5. Definition of babel-neighbor-obj

object {
ip-address ro babel-neighbor-address;
[binary ro babel-hello-mcast-history;]
[binary ro babel-hello-ucast-history;]
uint ro babel-txcost;
uint ro babel-exp-mcast-hello-seqno;
uint ro babel-exp-ucast-hello-seqno;
[uint ro babel-ucast-hello-seqno;]
[uint ro babel-ucast-hello-interval;]
[uint ro babel-rxcost;]
[uint ro babel-cost;]
} babel-neighbor-obj;

babel-neighbor-address: IPv4 or IPv6 address the neighbor sends
packets from.

babel-hello-mcast-history: The multicast Hello history of whether or
not the multicast Hello packets prior to babel-exp-mcast-hello-
seqno were received. A binary sequence where the most recently
received Hello is expressed as a "1" placed in the leftmost bit,
with prior bits shifted right (and "0" bits placed between prior
Hello bits and most recent Hello for any not-received Hellos).
This value should be displayed using hex digits ([0-9a-fA-F]).
See [RFC8966], Appendix A.1.

babel-hello-ucast-history: The unicast Hello history of whether or
not the unicast Hello packets prior to babel-exp-ucast-hello-seqno
were received. A binary sequence where the most recently received
Hello is expressed as a "1" placed in the leftmost bit, with prior
bits shifted right (and "0" bits placed between prior Hello bits
and the most recent Hello for any not-received Hellos). This
value should be displayed using hex digits ([0-9a-fA-F]). See
[RFC8966], Appendix A.1.

babel-txcost: Transmission cost value from the last IHU packet
received from this neighbor, or the maximum value to indicate the
IHU hold timer for this neighbor has expired. See [RFC8966],
Section 3.4.2. This is a 16-bit unsigned integer.

babel-exp-mcast-hello-seqno: Expected multicast Hello sequence
number of next Hello to be received from this neighbor. If
multicast Hello packets are not expected or processing of
multicast packets is not enabled, this MUST be NULL. This is a
16-bit unsigned integer; if the data model uses zero (0) to
represent NULL values for unsigned integers, the data model MAY
use a different data type that allows differentiation between zero
(0) and NULL.

babel-exp-ucast-hello-seqno: Expected unicast Hello sequence number
of next Hello to be received from this neighbor. If unicast Hello
packets are not expected or processing of unicast packets is not
enabled, this MUST be NULL. This is a 16-bit unsigned integer; if
the data model uses zero (0) to represent NULL values for unsigned
integers, the data model MAY use a different data type that allows
differentiation between zero (0) and NULL.

babel-ucast-hello-seqno: The current sequence number in use for
unicast Hellos sent to this neighbor. If unicast Hellos are not
being sent, this MUST be NULL. This is a 16-bit unsigned integer;
if the data model uses zero (0) to represent NULL values for
unsigned integers, the data model MAY use a different data type
that allows differentiation between zero (0) and NULL.

babel-ucast-hello-interval: The current interval in use for unicast
Hellos sent to this neighbor. Units are centiseconds. This is a
16-bit unsigned integer.

babel-rxcost: Reception cost calculated for this neighbor. This
value is usually derived from the Hello history, which may be
combined with other data, such as statistics maintained by the
link layer. The rxcost is sent to a neighbor in each IHU. See
[RFC8966], Section 3.4.3. This is a 16-bit unsigned integer.

babel-cost: The link cost, as computed from the values maintained in
the neighbor table: the statistics kept in the neighbor table
about the reception of Hellos and the txcost computed from
received IHU packets. This is a 16-bit unsigned integer.

3.6. Definition of babel-route-obj

object {
ip-address ro babel-route-prefix;
uint ro babel-route-prefix-length;
binary ro babel-route-router-id;
reference ro babel-route-neighbor;
uint ro babel-route-received-metric;
uint ro babel-route-calculated-metric;
uint ro babel-route-seqno;
ip-address ro babel-route-next-hop;
boolean ro babel-route-feasible;
boolean ro babel-route-selected;
} babel-route-obj;

babel-route-prefix: Prefix (expressed in IP address format) for
which this route is advertised.

babel-route-prefix-length: Length of the prefix for which this route
is advertised.

babel-route-router-id: The router-id of the router that originated
this route.

babel-route-neighbor: Reference to the babel-neighbors entry for the
neighbor that advertised this route.

babel-route-received-metric: The metric with which this route was
advertised by the neighbor, or the maximum value to indicate the
route was recently retracted and is temporarily unreachable (see
Section 3.5.4 of [RFC8966]). This metric will be NULL if the
route was not received from a neighbor but was generated through
other means. At least one of the following MUST be non-NULL:
babel-route-calculated-metric or babel-route-received-metric.
Having both be non-NULL is expected for a route that is received
and subsequently advertised. This is a 16-bit unsigned integer;
if the data model uses zero (0) to represent NULL values for
unsigned integers, the data model MAY use a different data type
that allows differentiation between zero (0) and NULL.

babel-route-calculated-metric: A calculated metric for this route.
How the metric is calculated is implementation specific. The
maximum value indicates the route was recently retracted and is
temporarily unreachable (see Section 3.5.4 of [RFC8966]). At
least one of the following MUST be non-NULL: babel-route-
calculated-metric or babel-route-received-metric. Having both be
non-NULL is expected for a route that is received and subsequently
advertised. This is a 16-bit unsigned integer; if the data model
uses zero (0) to represent NULL values for unsigned integers, the
data model MAY use a different data type that allows
differentiation between zero (0) and NULL.

babel-route-seqno: The sequence number with which this route was
advertised. This is a 16-bit unsigned integer.

babel-route-next-hop: The next-hop address of this route. This will
be empty if this route has no next-hop address.

babel-route-feasible: A Boolean flag indicating whether this route
is feasible, as defined in Section 3.5.1 of [RFC8966]).

babel-route-selected: A Boolean flag indicating whether this route
is selected (i.e., whether it is currently being used for
forwarding and is being advertised).

3.7. Definition of babel-mac-key-set-obj

object {
boolean rw babel-mac-default-apply;
babel-mac-key-obj rw babel-mac-keys<0..*>;
} babel-mac-key-set-obj;

babel-mac-default-apply: A Boolean flag indicating whether this
object instance is applied to all new babel-interfaces instances
by default. If "true", this instance is applied to new babel-
interfaces instances at the time they are created by including it
in the babel-if-mac-key-sets list. If "false", this instance is
not applied to new babel-interfaces instances when they are
created. An implementation MAY choose to expose this parameter as
read-only ("ro").

babel-mac-keys: A set of babel-mac-key-obj objects.

3.8. Definition of babel-mac-key-obj

object {
string rw babel-mac-key-name;
boolean rw babel-mac-key-use-send;
boolean rw babel-mac-key-use-verify;
binary -- babel-mac-key-value;
string rw babel-mac-key-algorithm;
[operation babel-mac-key-test;]
} babel-mac-key-obj;

babel-mac-key-name: A unique name for this MAC key that can be used
to identify the key in this object instance since the key value is
not allowed to be read. This value MUST NOT be empty and can only
be provided when this instance is created (i.e., it is not
subsequently writable). The value MAY be auto-generated if not
explicitly supplied when the instance is created.

babel-mac-key-use-send: Indicates whether this key value is used to
compute a MAC and include that MAC in the sent Babel packet. A
MAC for sent packets is computed using this key if the value is
"true". If the value is "false", this key is not used to compute
a MAC to include in sent Babel packets. An implementation MAY
choose to expose this parameter as read-only ("ro").

babel-mac-key-use-verify: Indicates whether this key value is used
to verify incoming Babel packets. This key is used to verify
incoming packets if the value is "true". If the value is "false",
no MAC is computed from this key for comparison with the MAC in an
incoming packet. An implementation MAY choose to expose this
parameter as read-only ("ro").

babel-mac-key-value: The value of the MAC key. An implementation
MUST NOT allow this parameter to be read. This can be done by
always providing an empty string when read, through permissions,
or by other means. This value MUST be provided when this instance
is created and is not subsequently writable. This value is of a
length suitable for the associated babel-mac-key-algorithm. If
the algorithm is based on the Hashed Message Authentication Code
(HMAC) construction [RFC2104], the length MUST be between 0 and an
upper limit that is at least the size of the output length (where
the "HMAC-SHA256" output length is 32 octets as described in
[RFC4868]). Longer lengths MAY be supported but are not necessary
if the management system has the ability to generate a suitably
random value (e.g., by randomly generating a value or by using a
key derivation technique as recommended in the security
considerations in Section 7 of [RFC8967]). If the algorithm is
"BLAKE2s-128", the length MUST be between 0 and 32 bytes inclusive
as specified by [RFC7693].

babel-mac-key-algorithm The name of the MAC algorithm used with this
key. The value MUST be the same as one of the enumerations listed
in the babel-mac-algorithms parameter. An implementation MAY
choose to expose this parameter as read-only ("ro").

babel-mac-key-test: An operation that allows the MAC key and MAC
algorithm to be tested to see if they produce an expected outcome.
Input to this operation is a binary string and a calculated MAC
(also in the format of a binary string) for the binary string.
The implementation is expected to create a MAC over the binary
string using the babel-mac-key-value and the babel-mac-key-
algorithm. The output of this operation is a Boolean indication
that the calculated MAC matched the input MAC (true) or the MACs
did not match (false).

3.9. Definition of babel-dtls-cert-set-obj

object {
boolean rw babel-dtls-default-apply;
babel-dtls-cert-obj rw babel-dtls-certs<0..*>;
} babel-dtls-cert-set-obj;

babel-dtls-default-apply: A Boolean flag indicating whether this
object instance is applied to all new babel-interfaces instances
by default. If "true", this instance is applied to new babel-
interfaces instances at the time they are created by including it
in the babel-interface-dtls-certs list. If "false", this instance
is not applied to new babel-interfaces instances when they are
created. An implementation MAY choose to expose this parameter as
read-only ("ro").

babel-dtls-certs: A set of babel-dtls-cert-obj objects. This
contains both certificates for this implementation to present for
authentication and those to accept from others. Certificates with
a non-empty babel-cert-private-key can be presented by this
implementation for authentication.

3.10. Definition of babel-dtls-cert-obj

object {
string rw babel-cert-name;
string rw babel-cert-value;
string rw babel-cert-type;
binary -- babel-cert-private-key;
} babel-dtls-cert-obj;

babel-cert-name: A unique name for this certificate that can be used
to identify the certificate in this object instance since the
value is too long to be useful for identification. This value
MUST NOT be empty and can only be provided when this instance is
created (i.e., it is not subsequently writable). The value MAY be
auto-generated if not explicitly supplied when the instance is
created.

babel-cert-value: The certificate in Privacy-Enhanced Mail (PEM)
format [RFC7468]. This value MUST be provided when this instance
is created and is not subsequently writable.

babel-cert-type: The name of the certificate type of this object
instance. The value MUST be the same as one of the enumerations
listed in the babel-dtls-cert-types parameter. This value can
only be provided when this instance is created and is not
subsequently writable.

babel-cert-private-key: The value of the private key. If this is
non-empty, this certificate can be used by this implementation to
provide a certificate during DTLS handshaking. An implementation
MUST NOT allow this parameter to be read. This can be done by
always providing an empty string when read, through permissions,
or by other means. This value can only be provided when this
instance is created and is not subsequently writable.

4. Extending the Information Model

Implementations MAY extend this information model with other
parameters or objects. For example, an implementation MAY choose to
expose Babel route filtering rules by adding a route filtering object
with parameters appropriate to how route filtering is done in that
implementation. The precise means used to extend the information
model would be specific to the data model the implementation uses to
expose this information.

5. Security Considerations

This document defines a set of information model objects and
parameters that may be exposed and visible from other devices. Some
of these information model objects and parameters may be configured.
Securing access to and ensuring the integrity of this data is in
scope of and the responsibility of any data model derived from this
information model. Specifically, any YANG [RFC7950] data model is
expected to define security exposure of the various parameters, and a
[TR-181] data model will be secured by the mechanisms defined for the
management protocol used to transport it.

Misconfiguration (whether unintentional or malicious) can prevent
reachability or cause poor network performance (increased latency,
jitter, etc.). Misconfiguration of security credentials can cause a
denial-of-service condition for the Babel routing protocol. The
information in this model discloses network topology, which can be
used to mount subsequent attacks on traffic traversing the network.

This information model defines objects that can allow credentials
(for this device, for trusted devices, and for trusted certificate
authorities) to be added and deleted. Public keys may be exposed
through this model. This model requires that private keys and MAC
keys never be exposed. Certificates used by [RFC8968]
implementations use separate parameters to model the public parts
(including the public key) and the private key.

MAC keys are allowed to be as short as zero length. This is useful
for testing. It is RECOMMENDED that network operators follow current
best practices for key length and generation of keys related to the
MAC algorithm associated with the key. Short (and zero-length) keys
are highly susceptible to brute-force attacks and therefore SHOULD
NOT be used. See the security considerations as described in
Section 7 of [RFC8967] for additional considerations related to MAC
keys; note that there are some specific key value recommendations in
the fifth paragraph. It says that if it is necessary to derive keys
from a human-readable passphrase, "only the derived keys should be
communicated to the routers" and "the original passphrase itself
should be kept on the host used to perform the key generation" (which
would be the management system in the case of a remote management
protocol). It also recommends that keys "should have a length of 32
octets (both for HMAC-SHA256 and BLAKE2s), and be chosen randomly".

This information model uses key sets and certification sets to
provide a means of grouping keys and certificates. This makes it
easy to use a different set per interface, use the same set for one
or more interfaces, have a default set in case a new interface is
instantiated, and change keys and certificates as needed.

6. IANA Considerations

This document has no IANA actions.

7. References

7.1. Normative References

[ISO.10646]
International Organization for Standardization,
"Information technology - Universal Coded Character Set
(UCS)", ISO Standard 10646:2014, 2014.

[libpcap] GitLab, "Libpcap File Format", Wireshark Foundation,
November 2020, <https://gitlab.com/wireshark/wireshark/-
/wikis/Development/LibpcapFileFormat>.

[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<https://www.rfc-editor.org/info/rfc2104>.

[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>.

[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.

[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868,
DOI 10.17487/RFC4868, May 2007,
<https://www.rfc-editor.org/info/rfc4868>.

[RFC7468] Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
April 2015, <https://www.rfc-editor.org/info/rfc7468>.

[RFC7693] Saarinen, M-J., Ed. and J-P. Aumasson, "The BLAKE2
Cryptographic Hash and Message Authentication Code (MAC)",
RFC 7693, DOI 10.17487/RFC7693, November 2015,
<https://www.rfc-editor.org/info/rfc7693>.

[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>.

[RFC8966] Chroboczek, J. and D. Schinazi, "The Babel Routing
Protocol", RFC 8966, DOI 10.17487/RFC8966, January 2021,
<https://www.rfc-editor.org/info/rfc8966>.

[RFC8967] Dô, C., Kolodziejak, W., and J. Chroboczek, "MAC
Authentication for the Babel Routing Protocol", RFC 8967,
DOI 10.17487/RFC8967, January 2021,
<https://www.rfc-editor.org/info/rfc8967>.

[RFC8968] Décimo, A., Schinazi, D., and J. Chroboczek, "Babel
Routing Protocol over Datagram Transport Layer Security",
RFC 8968, DOI 10.17487/RFC8968, January 2021,
<https://www.rfc-editor.org/info/rfc8968>.

7.2. Informative References

[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>.

[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>.

[RFC8193] Burbridge, T., Eardley, P., Bagnulo, M., and J.
Schoenwaelder, "Information Model for Large-Scale
Measurement Platforms (LMAPs)", RFC 8193,
DOI 10.17487/RFC8193, August 2017,
<https://www.rfc-editor.org/info/rfc8193>.

[TR-181] Broadband Forum, "Device Data Model", Issue: 2 Amendment
14, November 2020,
<http://cwmp-data-models.broadband-forum.org/>.

Acknowledgements

Juliusz Chroboczek, Toke Høiland-Jørgensen, David Schinazi, Antonin
Décimo, Roman Danyliw, Benjamin Kaduk, Valery Smyslov, Alvaro Retana,
Donald Eastlake, Martin Vigoureux, Acee Lindem, and Carsten Bormann
have been very helpful in refining this information model.

The language in the "Notation" section was mostly taken from
[RFC8193].

Authors' Addresses

Barbara Stark
AT&T
TX
United States of America

Email: [email protected]

Mahesh Jethanandani
Kloud Services
CA
United States of America

Email: [email protected]