Babel Information Model
draft-ietf-babel-information-model-01

Abstract

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.

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This Internet-Draft will expire on July 6, 2018.

Copyright Notice

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

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Table of Contents

• 1. Introduction
• 1.1. Requirements Language
• 1.2. Notation
• 2. The Information Model
• 2.1. Definition of babel-information
• 2.2. Definition of babel-constants
• 2.3. Definition of babel-interfaces
• 2.4. Definition of babel-neighbors
• 2.5. Definition of babel-security
• 2.6. Definition of babel-trust
• 2.7. Definition of babel-sources
• 2.8. Definition of babel-routes
• 3. Acknowledgements
• 4. References
• 4.1. Normative References
• 4.2. Informative References
• Appendix A. Open Issues
• Author's Address

1. Introduction

Babel is a loop-avoiding distance-vector routing protocol defined in RFC 6126bis. Babel Hashed Message Authentication Code (HMAC) Cryptographic Authentication, defined in RFC 7298, describes a cryptographic authentication mechanism for the Babel routing protocol. This document describes an information model for Babel (including HMAC) that can be used to created management protocol data models (such as a netconf [RFC6241] YANG data model). Other Babel extensions may be included in this document when they become working group drafts.

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 configuration of these parameters, it may still choose to expose them as read-only.

1.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

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 [RFC3339].

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 enumerations.

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. The Information Model

2.1. Definition of babel-information

     object {
          string                babel-implementation-version;
          base64                babel-self-router-id;
         [int                   babel-self-seqno;]
          string                babel-cost-comp-algorithms<1..*>;
          babel-constants-obj   babel-constants;
          babel-interfaces-obj  babel-interfaces<0..*>;
          babel-sources-obj     babel-sources<0..*>;
          babel-routes-obj      babel-routes<0..*>;
      }babel-information-obj;
            

• babel-version: the version of this implementation of the Babel protocol
• babel-self-router-id: the router-id used by this instance of the Babel protocol to identify itself; RFC 6126bis 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
• babel-cost-comp-algorithm: a set of names of supported cost computation algorithms; possible values include "k-out-of-j", "ETX"
• babel-constants: a babel-constants object
• babel-interfaces: a set of babel-interface objects
• babel-sources: a set of babel-source objects
• babel-routes: a set of babel-route objects

2.2. Definition of babel-constants

     object {
          int          babel-udp-port;
         [ip-address   babel-multicast-group-ipv6;]
         [ip-address   babel-multicast-group-ipv4;]
      }babel-constants-obj;
            

• babel-udp-port: UDP port for sending and listening for Babel messages; default is 6696; MAY be configurable
• babel-multicast-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-multicast-group-ipv4: multicast group for sending and listening to multicast announcements on IPv4; default is 224.0.0.111; MAY be configurable

2.3. Definition of babel-interfaces

     object {
          uri                  babel-interface-reference;
         [int                  babel-interface-seqno;]
         [int                  babel-interface-hello-interval;]
         [int                  babel-interface-update-interval;]
          boolean              babel-request-trigger-ack;
          boolean              babel-lossy-link;
         [int                  babel-external-cost;]
          babel-neighbors-obj  babel-neighbors<1..*>;
         [babel-security-obj   babel-security<1..*>;]
      }babel-interfaces-obj;
            

• babel-interface-reference: reference to an interface object as defined by the data model
• babel-interface-seqno: the current sequence number in use for this interface
• babel-interface-hello-interval: the current hello interval in use for this interface
• babel-interface-update-interval: the current update interval in use for this interface
• babel-request-trigger-ack: requests acknowledgement of triggered updates (if number of neighbors less than babel-ack-limit); MAY be configurable
• babel-lossy-link: indicates (if true) that the link of this interface is considered lossy; MAY be configurable
• babel-external-cost: external input to cost of link of this interface (need to determine how to express this);MUST be configurable if implemented

2.4. Definition of babel-neighbors

     object {
          ip-address           babel-neighbor-address;
          string               babel-hello-history;
          int                  babel-txcost;
          int                  babel-hello-seqno;
          int                  babel-neighbor-ihu-interval;
         [int                  babel-rxcost]
      }babel-neighbors-obj;
            

• babel-neighbor-address: (IPv4 or v6) address the neighbor sends messages from
• babel-hello-history: the Hello history (do we want a human readable format?)
• babel-txcost: transmission cost value from the last IHU packet received from this neighbor, or meximum 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 neighbor
• babel-router-id: router-id of the neighbor
• babel-rxcost: reception cost calculated for this neighbor

2.5. Definition of babel-security

     object {
          string                babel-security-supported;
          string                babel-security-enabled-protocol;
          credentials           babel-security-self-cred;
          babel-trust-obj       babel-trust<1..*>;
    }babel-security-obj;
            

• 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: the credentials this router presents to participate in the enabled security protocol
• babel-trust-obj: a set of babel-trust objects that identify the credentials of a router whose babel messages are trusted

2.6. Definition of babel-trust

     object {
          credentials           babel-trust-cred;
    }babel-trust-obj;
            

• babel-trust-cred: the credentials of a router whose babel messages can be trusted

2.7. Definition of babel-sources

     object {
          ip-address           babel-source-prefix;
          int                  babel-source-prefix-length;
          base64               babel-source-router-id;
          int                  babel-source-seqno;
          int                  babel-source-metric;
         [int                  babel-source-garbage-collection-time;]
      }babel-sources-obj;
            

• babel-source-prefix: Prefix this entry applies to
• babel-source-prefix-length: Length of the source prefix
• babel-source-router-id: router-id of the router originating this prefix
• babel-source-seqno: last sequence number used by this source
• babel-source-metric: this source's feasibility distance
• babel-source-garbage-collection-time: garbage-collection timer for this source

2.8. Definition of babel-routes

     object {
          ip-address           babel-route-prefix;
          int                  babel-route-prefix-length;
          base64               babel-route-router-id;
          base64               babel-route-neighbor;
          int                  babel-route-metric;
          int                  babel-route-seqno;
          ip-address           babel-route-next-hop;
          boolean              babel-route-selected;
      }babel-routes-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: router-id of the source router for which this route is advertised
• babel-route-neighbor: neighbor that advertised this route (a router-id)
• babel-route-metric: the metric with which this route was advertised by the neighbor, or maximum value (infinity) to indicate a recently retracted route
• babel-route-seqno: the sequence number with which this route was advertised
• babel-route-next-hop: the next-hop address of this route
• 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. Acknowledgements

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

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

4. References

4.1. Normative References

4.2. Informative References

Appendix A. Open Issues

This draft must be reviewed against draft-ietf-babel-rfc6126bis.

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

• 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?"
• babel-interfaces-obj: "This needs further discussion, I fear some of these are implementation details."
• Would it be useful to define some parameters for reporting statistics or logs? [Yes, but these need to be proposed.]
• Would it be useful to define some parameters specifically for security anomalies? [Yes, but these need to be proposed.]
• I created a basic security model. It's useful for single (or no) active security mechanism; but not multiple active. OK?
• Do we need a registry for the supported security mechanisms?

Author's Address