Babel routing protocol                                          B. Stark
Internet-Draft                                                      AT&T
Intended status: Informational                             April 5, 2018
Expires: October 7, 2018

                        Babel Information Model


   This Babel Information Model can be used to create data models under
   various data modeling regimes (e.g., YANG).  It allows a Babel
   implementation (via a management protocol such as netconf) to report
   on its current state and may allow some limited configuration of
   protocol constants.

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
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   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 October 7, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Notation  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  The Information Model . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Definition of babel-information-obj . . . . . . . . . . .   5
     3.2.  Definition of babel-constants-obj . . . . . . . . . . . .   6
     3.3.  Definition of babel-interfaces-obj  . . . . . . . . . . .   7
     3.4.  Definition of babel-neighbors-obj . . . . . . . . . . . .   8
     3.5.  Definition of babel-security-obj  . . . . . . . . . . . .   9
     3.6.  Definition of babel-routes-obj  . . . . . . . . . . . . .  10
   4.  Common Objects  . . . . . . . . . . . . . . . . . . . . . . .  11
     4.1.  Definition of babel-credential-obj  . . . . . . . . . . .  11
     4.2.  Definition of babel-log-obj . . . . . . . . . . . . . . .  11
   5.  Extending the Information Model . . . . . . . . . . . . . . .  11
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Appendix A.  Open Issues  . . . . . . . . . . . . . . . . . . . .  13
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   Babel is a loop-avoiding distance-vector routing protocol defined in
   draft-ietf-babel-rfc6126bis [rfc6126bis]. draft-babel-7298bis
   [BABEL-HMAC] defines a security mechanism that allows Babel messages
   to be cryptographically authenticated, and draft-babel-dtls
   [BABEL-DTLS] defines a security mechanism that allows Babel messages
   to encrypted.  This document describes an information model for Babel
   (including implementations using one of these security mechanisms)
   that can be used to created management protocol data models (such as
   a netconf [RFC6241] YANG data model).

   Due to the simplicity of the Babel protocol and the fact that it is
   designed to be used in non-professionally administered environments
   (such as home networks), most of the information model is focused on
   reporting status of the Babel protocol, and very little of that is
   considered mandatory to implement (conditional on a management
   protocol with Babel support being implemented).  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

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   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.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 values, and n is the maximum.  The symbol * for
   n means no upper bound.

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

   base64      An opaque array of bytes.

   boolean     A type representing a boolean value.

   counter     A non-negative integer that monotonically increases.
               Counters may have discontinuities and they are not
               expected to persist across restarts.

   credentials An opaque type representing credentials needed by a
               cryptographic mechanism to secure communication.  Data
               models must expand this opaque type as needed and
               required by the security protocols utilized.

   datetime    A type representing a date and time using the Gregorian
               calendar.  The datetime format MUST conform to RFC 3339

   int         A type representing signed or unsigned integer numbers.
               This information model does not define a precision nor
               does it make a distinction between signed and unsigned
               number ranges.  This type is also used to represent

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

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

   uri         A type representing a Uniform Resource Identifier as
               defined in STD 66 [RFC3986].

2.  Overview

   The Information Model is hierarchically structured as follows:

   information object
      includes implementation version, router id, this node seqno,
        enable flag parameters
      constants object (exactly one per information object)
         includes UDP port and optional multicast and unicast groups
      interfaces object
         includes interface reference, Hello seqno and intervals,
           update interval, link type, external cost parameters
         neighbors object
            includes neighbor IP address, Hello history, cost
         security object (per interface)
            includes supported and enabled security mechanisms, self
              credentials (credential object), trusted credentials
              (credential object)
      security object (common to all interfaces)
         includes supported and enabled security mechanisms, self
           credentials (credential object), trusted credentials
           (credential object)
      routes object
         includes route prefix, source router, reference to
           advertising neighbor, metric, sequence number, whether
           route is feasible, whether route is selected

   Following is a list of the data elements that an implementation can
   choose to allow to be configurable:

   o  enable/disable babel

   o  Constant: UDP port

   o  Constant: IPv6 multicast group

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   o  Constant: IPv4 multicast group

   o  Interface: Link type

   o  Interface: External cost (must be configurable if implemented, but
      implementation is optional)

   o  Interface: enable/disable babel on this interface

   o  Interface: enable/disable message log

   o  Security: self credentials

   o  Security: trusted credentials

   o  Security: enable/disable security log

   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                babel-implementation-version;
             boolean               babel-enable;
             base64                babel-self-router-id;
             string                babel-supported-link-types<1..*>;
            [int                   babel-self-seqno;]
             string                babel-metric-comp-algorithms<1..*>;
             babel-constants-obj   babel-constants;
             babel-interfaces-obj  babel-interfaces<0..*>;
             babel-routes-obj      babel-routes<0..*>;
            [babel-security-obj    babel-security;]

      babel-implementation-version: the version of this implementation
      of the Babel protocol

      babel-enable: if true, the babel implementation is running; if
      false, the babel implementation is not currently running; MAY be
      configurable to allow babel to be started or stopped

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      babel-self-router-id: the router-id used by this instance of the
      Babel protocol to identify itself; draft-ietf-babel-rfc6126bis
      [rfc6126bis] describes this as an arbitrary string of 8 octets

      babel-supported-link-types: set of values of supported link types
      where the following enumeration values MUST be supported: 1 =
      wireless, 2 = physical-layer ethernet, 99 = other

      babel-self-seqno: the current sequence number included in route
      updates for routes originated by this node

      babel-metric-comp-algorithms: a set of names of supported cost
      computation algorithms; possible values include "k-out-of-j",

      babel-constants: a babel-constants object

      babel-interfaces: a set of babel-interface objects

      babel-security: a babel-security object that applies to all
      interfaces; if this object is implemented, it allows a security
      mechanism to be enabled or disabled in a manner that applies to
      all Babel messages on all interfaces

      babel-sources: a set of babel-source objects

      babel-routes: a set of babel-route objects; includes received and
      routes routes

3.2.  Definition of babel-constants-obj

        object {
             int          babel-udp-port;
            [ip-address   babel-mcast-group-ipv6;]
            [ip-address   babel-mcast-group-ipv4;]

      babel-udp-port: UDP port for sending and listening for Babel
      messages; default is 6696; MAY be configurable

      babel-mcast-group-ipv6: multicast group for sending and listening
      to multicast announcements on IPv6; default is ff02:0:0:0:0:0:1:6;
      MAY be configurable

      babel-mcast-group-ipv4: multicast group for sending and listening
      to multicast announcements on IPv4; default is; MAY be

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3.3.  Definition of babel-interfaces-obj

        object {
             string               babel-interface-reference;
            [boolean              babel-interface-enable;]
             int                  babel-link-type;
            [int                  babel-mcast-hello-seqno;]
            [int                  babel-ucast-hello-seqno;]
            [int                  babel-mcast-hello-interval;]
            [int                  babel-ucast-hello-interval;]
            [int                  babel-update-interval;]
            [int                  babel-external-cost;]
            [boolean              babel-message-log-enable;]
            [babel-log-obj        babel-message-log<0..*>;]
             babel-neighbors-obj  babel-neighbors<1..*>;
            [babel-security-obj   babel-interface-security;]

      babel-interface-reference: reference to an interface object as
      defined by the data model (e.g., YANG, BBF TR-181); data model is
      assumed to allow for referencing of interface objects which may be
      at any layer (physical, Ethernet MAC, IP, tunneled IP, etc.);
      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

      babel-interface-enable: if true, babel sends and receives messages
      on this interface; if false, babel messages received on this
      interface are ignored and none are sent; MAY be configurable

      babel-link-type: indicates the type of link; integer values
      specify an enumeration of a supported link type where the
      following enumerations MUST be supported: 1 = wireless, 2 =
      physical-layer ethernet, 99 = other; additional values MAY be
      supported; MAY be configurable

      babel-mcast-hello-seqno: the current sequence number in use for
      multicast hellos on this interface

      babel-ucast-hello-seqno: the current sequence number in use for
      unicast hellos on this interface

      babel-mcast-hello-interval: the current multicast hello interval
      in use for this interface

      babel-ucast-hello-interval: the current unicast hello interval in
      use for this interface

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      babel-update-interval: the current update interval in use for this

      babel-external-cost: external input to cost of link of this
      interface (need to determine how to express this);MUST be
      configurable if implemented

      babel-message-log-enable: if true, logging of babel messages
      received on this interface is enabled; if false, babel messages
      are not logged; MUST be configurable, if implemented

      babel-message-log: log entries that have timestamp of a received
      Babel message and the entire received Babel message, including
      Ethernet frame and IP headers; an implementation must restrict the
      size of this log, but how and what size is implementation-specific

      babel-neighbors: a set of babel-neighbors objects

      babel-interface-security: a babel-security object that applies to
      this interface; if implemented, this allows security to be enabled
      only on specific interfaces or allows different security
      mechanisms to be enabled on different interfaces

3.4.  Definition of babel-neighbors-obj

        object {
             ip-address           babel-neighbor-address;
            [string               babel-hello-mcast-history;]
            [string               babel-hello-ucast-history;]
             int                  babel-txcost;
             int                  babel-hello-seqno;
             int                  babel-neighbor-ihu-interval;
            [int                  babel-rxcost]
            [int                  babel-cost]

      babel-neighbor-address: (IPv4 or v6) address the neighbor sends
      messages from

      babel-hello-mcast-history: the multicast Hello history of whether
      or not each of the 16 multicast Hello messages prior to babel-
      hello-seqno was received; represented as a 16 bit (4 hex digits)
      value where 1 = Hello received and 0 = Hello not received; see
      draft-ietf-babel-rfc6126bis [rfc6126bis] section A.1

      babel-hello-ucast-history: the unicast Hello history of whether or
      not each of the 16 unicast Hello messages prior to babel-hello-
      seqno was received; represented as a 16 bit (4 hex digits) value

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      where 1 = Hello received and 0 = Hello not received; see draft-
      ietf-babel-rfc6126bis [rfc6126bis] section A.1

      babel-txcost: transmission cost value from the last IHU packet
      received from this neighbor, or maximum value (infinity) to
      indicates the IHU hold timer for this neighbor has expired

      babel-hello-seqno: expected Hello sequence number

      babel-neighbor-ihu-interval: current IHU interval for this

      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 neighbour in each IHU

      babel-cost: link cost is computed from the values maintained in
      the neighbour table: the statistics kept in the neighbour table
      about the reception of Hellos, and the txcost computed from
      received IHU packets

3.5.  Definition of babel-security-obj

        object {
             string                babel-security-supported;
             string                babel-security-enabled-protocol;
             babel-credential-obj  babel-security-self-cred<1..*>;
             babel-credential-obj  babel-security-trust<1..*>;
            [boolean               babel-credvalid-log-enable;]
            [babel-log-obj         babel-credvalid-log<0..*>;]

      babel-security-supported: list of supported security mechanisms

      babel-security-enabled-protocol: the currently enabled security
      protocol; empty if none is enabled

      babel-security-self-cred: credentials this router presents to
      participate in the enabled security protocol; ; adding and
      deleting credentials MAY be allowed

      babel-security-trust: a set of babel-credential-obj objects that
      identify the credentials of routers whose babel messages may be
      trusted or of a certificate authority (CA) whose signing of a
      router's credentials implies the router credentials can be
      trusted; how a security mechanism interacts with this list is
      determined by the mechanism; a security algorithm may do

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      additional validation of credentials, such as checking validity
      dates or revocation lists, so presence may not be sufficient to
      determine trust; adding and deleting credentials MAY be allowed

      babel-credvalid-log-enable: if true, logging of messages that
      include credentials used for authentication is enabled; if false,
      these messages are not logged; MUST be configurable, if

      babel-credvalid-log: log entries that have the timestamp a message
      containing credentials used for peer authentication (e.g., DTLS
      Server Hello) was received on a Babel port, and the entire
      received message (including Ethernet frame and IP headers); an
      implementation must restrict the size of this log, but how and
      what size is implementation-specific

3.6.  Definition of babel-routes-obj

        object {
             ip-address           babel-route-prefix;
             int                  babel-route-prefix-length;
             base64               babel-route-router-id;
            [int                  babel-route-metric;]
            [int                  babel-route-announced-metric;]
             int                  babel-route-seqno;
             ip-address           babel-route-next-hop;
             boolean              babel-route-feasible;
             boolean              babel-route-selected;

      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: router-id of the source router for which
      this route is advertised

      babel-route-metric: the metric with which this route was
      advertised by the neighbor, or maximum value (infinity) to
      indicate a recently retracted route; this metric will be 0 (zero)
      if the route was not received from a neighbor but was generated
      through other means; either babel-route-announced-metric or babel-
      route-metric MUST be provided

      babel-route-announced-metric: a calculated metric for this route;
      how the metric is calculated is implementation-specific; either

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      babel-route-announced-metric or babel-route-metric MUST be

      babel-route-seqno: the sequence number with which this route was

      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 known to work; a route that is not feasible will never be

      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

4.  Common Objects

4.1.  Definition of babel-credential-obj

        object {
             credentials           babel-cred;

      babel-cred: a credential, such as an X.509 certificate, a public
      key, etc. used for signing and/or encrypting babel messages

4.2.  Definition of babel-log-obj

        object {
             datetime           babel-log-time;
             string             babel-log-entry;

      babel-log-time: the date and time (according to the device
      internal clock setting, which may be a time relative to boot time,
      acquired from NTP, configured by the user, etc.) when this log
      entry was created

      babel-log-entry: the logged message, as a string of utf-8 encoded
      hex characters

5.  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

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   with parameters appropriate to how route filtering is done in that
   implementation.  The precises means used to extend the information
   model would be specific to the data model the implementation uses to
   expose this information.

6.  Security Considerations

   This document defines a set of information model objects and
   parameters that may be exposed to be visible from other devices, and
   some of which may be configured.  Any mechanism or protocol that is
   used to transmit this information or allow for its configuration is
   also responsible for ensuring this is done so in a secure manner.

7.  IANA Considerations

   This document makes no IANA requests.

8.  Acknowledgements

   Juliusz Chroboczek's review has been very helpful in refining this
   information model.

   The language in the Notation section was mostly taken from RFC 8193

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

              Chroboczek, J., "The Babel Routing Protocol", Work in
              Progress, draft-ietf-babel-rfc6126bis, October 2017.

9.2.  Informative References

              Schinazi, D., "TBD", Work in Progress, rfc6347, March

              Ovsienko, D., "Babel HMAC Cryptographic Authentication",
              Work in Progress, draft-ovsienko-babel-rfc7298bis, March

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              International Organization for Standardization,
              "Information Technology - Universal Multiple-Octet Coded
              Character Set (UCS)", ISO Standard 10646:2014, 2014.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,

   [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,

   [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,

Appendix A.  Open Issues

   This draft must be reviewed against draft-ietf-babel-rfc6126bis.  [I
   feel like this has been adequately done, but I could be wrong.]

   Following are some issues where a conscious decision may be useful:

   1.   babel-interfaces-obj: Juliusz:"This needs further discussion, I
        fear some of these are implementation details."  [In the absence
        of discussion, the current model stands.  Note that all but
        link-type and the neighbors sub-object are optional; if an
        implementation does not have any of the optional elements then
        it simply doesn't have them and that's fine.]

   2.   Would it be useful to define some parameters for reporting
        statistics or logs? [2 logs are now included.  If others are
        needed they need to be proposed.]

   3.   Would it be useful to define some parameters specifically for
        security anomalies?  [The 2 logs should be useful in identifying
        security anomalies.  If more is needed, someone needs to

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   4.   I created a basic security model.  It's useful for single (or
        no) active security mechanism (e.g., just HMAC, just DTLS, or
        neither); but not multiple active (both HMAC and DTLS -- which
        is not the same as HMAC of DTLS and would just mean that HMAC
        would be used on all unencrypted messages -- but right now the
        model doesn't allow for configuring HMAC of unencrypted messages
        for routers without DTLS, while DTLS is used if possible).  OK?

   5.   Do we need a registry for the supported security mechanisms?
        [Given the current limited set, and unlikelihood of massive
        expansion, I don't think so.  But we can if someone wants it.]

   6.   babel-external-cost may need more work. [if no comment, it will
        be left as is]

   7.   babel-hello-[mu]cast-history: the Hello history is formated as
        16 bits, per A.1 of 6126bis.  Is that a too implementation
        specific?  [We also now have an optional-to-implement log of
        received messages, and I made these optional.  So maybe this is

   8.   rxcost, txcost, cost: is it ok to model as integers, since
        6126bis 2.1 says costs and metrics need not be integers.  [I
        have them as integers unless someone insists on something else.]

   9.   Should babel link types have an IANA registry?  [Right now, none
        is defined.]

   10.  For the security log, should it also log whether the credentials
        were considered ok?  [Right now it doesn't and I think that's ok
        because if you log Hellos it was ok and if you don't it wasn't.]

   Closed Issues:

      Closed by defining base64 type and using it for all router IDs:
      "babel-self-router-id: Should this be an opaque 64-bit value
      instead of int?"

Appendix B.  Change Log

   Individual Drafts:

      v00 2016-07-07 EBD Initial individual draft version

      v01 2017-03-13 Addressed comments received in 2016-07-15 email
      from J.  Chroboczek

   Working group drafts:

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      v00 2017-07-03 Addressed points noted with "oops" in

      v01 2018-01-02 Removed item from issue list that was agreed (in
      Prague) not to be an issue.  Added description of data types under
      Notation section, and used these in all data types.  Added babel-
      security and babel-trust.

      v02 2018-mm-dd

         - changed babel-version description to babel-implementation-

         - replace optional babel-interface-seqno with optional babel-
         mcast-hello-seqno and babel-ucast-hello-seqno

         - replace optional babel-interface-hello-interval with optional
         babel-mcast-hello-interval and babel-ucast-hello-interval

         - remove babel-request-trigger-ack

         - remove "babel-router-id: router-id of the neighbor"; note
         that parameter had previously been removed but description had
         accidentally not been removed

         - added an optional "babel-cost" field to babel-neighbors
         object, since the spec does not define how exactly the cost is
         computed from rxcost/txcost

         - deleted babel-source-garbage-collection-time

         - change babel-lossy-link to babel-link-type and make this an
         enumeration; added at top level babel-supported-link-types so
         which are supported by this implementation can be reported

         - changes to babel-security-obj to allow self credentials to be
         one or more instances of a credential object; allowed trusted
         credentials to include CA credentials; made some parameter name

         - updated references and Introduction

         - added Overview section

         - deleted babel-sources-obj

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Internet-Draft           Babel Information Model              April 2018

         - added feasible Boolean to routes

         - added section to briefly describe extending the information

         - deleted babel-route-neighbor

         - tried to make definition of babel-interface-reference clearer

         - added security and message logs

Author's Address

   Barbara Stark
   Atlanta, GA


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