draft-ietf-homenet-babel-profile-02.txt   draft-ietf-homenet-babel-profile-03.txt 
Network Working Group J. Chroboczek Network Working Group J. Chroboczek
Internet-Draft IRIF, University of Paris-Diderot Internet-Draft IRIF, University of Paris-Diderot
Intended status: Experimental July 3, 2017 Intended status: Experimental October 25, 2017
Expires: January 4, 2018 Expires: April 28, 2018
Homenet profile of the Babel routing protocol Homenet profile of the Babel routing protocol
draft-ietf-homenet-babel-profile-02 draft-ietf-homenet-babel-profile-03
Abstract Abstract
This document defines the subset of the Babel routing protocol This document defines the subset of the Babel routing protocol
[RFC6126] and its extensions that a Homenet router must implement, as [RFC6126bis] and its extensions that a Homenet router must implement,
well as the interactions between HNCP [RFC7788] and Babel. as well as the interactions between HNCP [RFC7788] and Babel.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 4, 2018. This Internet-Draft will expire on April 28, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . 7 6.1. Normative References . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . 7 6.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
The core of the Homenet protocol suite consists of HNCP [RFC7788], a The core of the Homenet protocol suite consists of HNCP [RFC7788], a
protocol used for flooding configuration information and assigning protocol used for flooding configuration information and assigning
prefixes to links, combined with the Babel routing protocol prefixes to links, combined with the Babel routing protocol
[RFC6126]. Babel is an extensible, flexible and modular protocol: [RFC6126bis]. Babel is an extensible, flexible and modular protocol:
minimal implementations of Babel have been demonstrated that consist minimal implementations of Babel have been demonstrated that consist
of a few hundred of lines of code, while the "large" implementation of a few hundred of lines of code, while the "large" implementation
includes support for a number of extensions and consists of over ten includes support for a number of extensions and consists of over ten
thousand lines of C code. thousand lines of C code.
This document consists of two parts. The first specifies the exact This document consists of two parts. The first specifies the exact
subset of the Babel protocol and its extensions that is required by subset of the Babel protocol and its extensions that is required by
an implementation of the Homenet protocol suite. The second an implementation of the Homenet protocol suite. The second
specifies how HNCP interacts with Babel. specifies how HNCP interacts with Babel.
1.1. Background 1.1. Background
The Babel routing protocol and its extensions are defined in a number The Babel routing protocol and its extensions are defined in a number
of documents: of documents:
o The body of RFC 6126 [RFC6126] defines the core, unextended o RFC 6126bis [RFC6126bis] defines the Babel routing protocol. It
protocol. It allows Babel's control data to be carried over allows Babel's control data to be carried over either link-local
either link-local IPv6 or IPv4, and in either case allows IPv6 or IPv4, and in either case allows announcing both IPv4 and
announcing both IPv4 and IPv6 routes. It leaves link cost IPv6 routes. It leaves link cost estimation, metric computation
estimation, metric computation and route selection to the and route selection to the implementation. Distinct
implementation. Distinct implementations of core RFC 6126 Babel implementations of RFC 6126 Babel will interoperate, in the sense
will interoperate and maintain a set of loop-free forwarding that they will maintain a set of loop-free forwarding paths.
paths, but given conflicting metrics or route selection policies However, if they implement conflicting options, they might not be
may give rise to persistent oscillations. able to exchange a full set of routes; in the worst case, an
implementation that only implements the IPv6 subset of the
protocol and an implementation that only implements the IPv4
subset of the protocol will not exchange any routes. In addition,
if implementations use conflicting route selection policies,
persistent oscillations might occur.
o The informative Appendix A of RFC 6126 suggests a simple and easy o The informative Appendix A of RFC 6126 suggests a simple and easy
to implement algorithm for cost and metric computation that has to implement algorithm for cost and metric computation that has
been found to work satisfactorily in a wide range of topologies. been found to work satisfactorily in a wide range of topologies.
o While RFC 6126 does not provide an algorithm for route selection, o While RFC 6126 does not provide an algorithm for route selection,
its Section 3.6 suggests selecting the route with smallest metric its Section 3.6 suggests selecting the route with smallest metric
with some hysteresis applied. An algorithm that has been found to with some hysteresis applied. An algorithm that has been found to
work well in practice is described in Section III.E of work well in practice is described in Section III.E of
[DELAY-BASED]. [DELAY-BASED].
o The extension mechanism for Babel is defined in RFC 7557 o Five RFCs and Internet-Drafts define optional extensions to Babel:
[RFC7557].
o Four RFCs and Internet-Drafts define optional extensions to Babel:
HMAC-based authentication [RFC7298], source-specific routing HMAC-based authentication [RFC7298], source-specific routing
[BABEL-SS], radio interference aware routing [BABEL-Z], and delay- [BABEL-SS], delay-based routing [BABEL-RTT] and ToS-specific
based routing [BABEL-RTT]. All of these extensions interoperate routing [ToS-SPECIFIC]. All of these extensions interoperate with
with the core protocol as well as with each other. the core protocol as well as with each other.
2. The Homenet profile of Babel 2. The Homenet profile of Babel
2.1. Requirements 2.1. Requirements
REQ1: a Homenet implementation of Babel MUST encapsulate Babel REQ1: a Homenet implementation of Babel MUST encapsulate Babel
control traffic in IPv6 packets sent to the IANA-assigned port 6696 control traffic in IPv6 packets sent to the IANA-assigned port 6696
and either the IANA-assigned multicast group ff02::1:6 or to a link- and either the IANA-assigned multicast group ff02::1:6 or to a link-
local unicast address. local unicast address.
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subset of the protocol defined in the body of RFC 6126. subset of the protocol defined in the body of RFC 6126.
Rationale: support for IPv6 routing is an essential component of Rationale: support for IPv6 routing is an essential component of
the Homenet architecture. the Homenet architecture.
REQ3: a Homenet implementation of Babel SHOULD implement the IPv4 REQ3: a Homenet implementation of Babel SHOULD implement the IPv4
subset of the protocol defined in the body of RFC 6126. Use of other subset of the protocol defined in the body of RFC 6126. Use of other
techniques for acquiring IPv4 connectivity (such as multiple layers techniques for acquiring IPv4 connectivity (such as multiple layers
of NAT) is strongly discouraged. of NAT) is strongly discouraged.
Rationale: support for IPv4 will remain necessary for years to Rationale: support for IPv4 will likely remain necessary for years
come, and even in pure IPv6 deployments, including code for to come, and even in pure IPv6 deployments, including code for
supporting IPv4 has very little cost. Since HNCP makes it easy to supporting IPv4 has very little cost. Since HNCP makes it easy to
assign distinct IPv4 prefixes to the links in a network, it is not assign distinct IPv4 prefixes to the links in a network, it is not
necessary to resort to multiple layers of NAT, with all of its necessary to resort to multiple layers of NAT, with all of its
problems. problems.
REQ4: a Homenet implementation of Babel MUST implement source- REQ4: a Homenet implementation of Babel MUST implement source-
specific routing for IPv6, as defined in draft-boutier-babel-source- specific routing for IPv6, as defined in draft-ietf-babel-source-
specific [BABEL-SS]. This implies that it MUST implement the specific [BABEL-SS].
extension mechanism defined in RFC 7557.
Rationale: source-specific routing is an essential component of Rationale: source-specific routing is an essential component of
the Homenet architecture. The extension mechanism is required by the Homenet architecture. Source-specific routing for IPv4 is not
source-specific routing. Source-specific routing for IPv4 is not
required, since HNCP arranges things so that a single non-specific required, since HNCP arranges things so that a single non-specific
IPv4 default route is announced (Section 6.5 of [RFC7788]). IPv4 default route is announced (Section 6.5 of [RFC7788]).
REQ5: a Homenet implementation of Babel MUST use metrics that are of REQ5: a Homenet implementation of Babel MUST use metrics that are of
a similar magnitude to the values suggested in Appendix A of a similar magnitude to the values suggested in Appendix A of
RFC 6126. In particular, it SHOULD assign costs that are no less RFC 6126. In particular, it SHOULD assign costs that are no less
than 256 to wireless links, and SHOULD assign costs between 32 and than 256 to wireless links, and SHOULD assign costs between 32 and
196 to lossless wired links. 196 to lossless wired links.
Rationale: if two implementations of Babel choose very different Rationale: if two implementations of Babel choose very different
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Homenet. Homenet.
3. Interactions between HNCP and Babel 3. Interactions between HNCP and Babel
The Homenet architecture cleanly separates between configuration, The Homenet architecture cleanly separates between configuration,
which is done by HNCP, and routing, which is done by Babel. While which is done by HNCP, and routing, which is done by Babel. While
the coupling between the two protocols is deliberately kept to a the coupling between the two protocols is deliberately kept to a
minimum, some interactions are unavoidable. minimum, some interactions are unavoidable.
All the interactions between HNCP and Babel consist of HNCP causing All the interactions between HNCP and Babel consist of HNCP causing
Babel to perform an announcement on its behalf (in particular, under Babel to perform an announcement on its behalf (under no
no circumstances does Babel cause HNCP to perform an action). How circumstances does Babel cause HNCP to perform an action). How this
this is realised is an implementation detail that is outside the is realised is an implementation detail that is outside the scope of
scope of this document: while it could conceivably be done using a this document; while it could conceivably be done using a private
private communication channel between HNCP and Babel, existing communication channel between HNCP and Babel, in existing
implementations have HNCP install a route in the operating system's implementations HNCP installs a route in the operating system's
kernel which is later picked up by Babel using the existing kernel which is later picked up by Babel using the existing
redistribution mechanisms. redistribution mechanisms.
3.1. Requirements 3.1. Requirements
REQ7: if an HNCP node receives a DHCPv6 prefix delegation for prefix REQ7: if an HNCP node receives a DHCPv6 prefix delegation for prefix
P and publishes an External-Connection TLV containing a Delegated- P and publishes an External-Connection TLV containing a Delegated-
Prefix TLV with prefix P and no Prefix-Policy TLV, then it MUST Prefix TLV with prefix P and no Prefix-Policy TLV, then it MUST
announce a source-specific default route with source prefix P over announce a source-specific default route with source prefix P over
Babel. Babel.
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behaviour is application-specific. behaviour is application-specific.
REQ8: if an HNCP node receives a DHCPv4 lease with an IPv4 address REQ8: if an HNCP node receives a DHCPv4 lease with an IPv4 address
and wins the election for NAT gateway, then it MUST act as a NAT and wins the election for NAT gateway, then it MUST act as a NAT
gateway and MUST announce a (non-specific) IPv4 default route over gateway and MUST announce a (non-specific) IPv4 default route over
Babel. Babel.
Rationale: the Homenet architecture does not use source-specific Rationale: the Homenet architecture does not use source-specific
routing for IPv4; instead, HNCP elects a single NAT gateway and routing for IPv4; instead, HNCP elects a single NAT gateway and
publishes a single default route towards that gateway ([RFC7788] publishes a single default route towards that gateway ([RFC7788]
7788 Section 6.5). Section 6.5).
REQ9: if an HNCP node assigns a prefix P to an attached link and REQ9: if an HNCP node assigns a prefix P to an attached link and
announces P in an Assigned-Prefix TLV, then it MUST announce a route announces P in an Assigned-Prefix TLV, then it MUST announce a route
towards P over Babel. towards P over Babel.
Rationale: prefixes assigned to links must be routable within the Rationale: prefixes assigned to links must be routable within the
Homenet. Homenet.
3.2. Non-requirements 3.2. Non-requirements
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different paths, with all the confusion that this entails. different paths, with all the confusion that this entails.
4. Security Considerations 4. Security Considerations
Both HNCP and Babel carry their control data in IPv6 packets with a Both HNCP and Babel carry their control data in IPv6 packets with a
link-local source address, and implementations are required to drop link-local source address, and implementations are required to drop
packets sent from a global address. Hence, they are only susceptible packets sent from a global address. Hence, they are only susceptible
to attacks from a directly connected link on which the HNCP and Babel to attacks from a directly connected link on which the HNCP and Babel
implementations are listening. implementations are listening.
The security of a Homenet network relies on having a set of trusted The security of a Homenet network relies on having a set of
"internal" links that are secured at a lower layer (either physically "Internal" and "Ad Hoc" interfaces (Section 5.1 of [RFC7788]) that
or at the link layer); HNCP and Babel packets are only accepted when are assumed to be connected to links that are secured at a lower
they originate on these trusted links (see Section 5 of [RFC7788]). layer. HNCP and Babel packets are only accepted when they originate
External, leaf and guest links are not trusted, and any HNCP or Babel on these trusted links. "External" and "Guest" interfaces are
packets that are received on such links are ignored. connected to links that are not trusted, and any HNCP or Babel
packets that are received on such interfaces are ignored. ("Leaf"
interfaces are a special case, since they are connected to trusted
links but HNCP and Babel traffic received on such interfaces is
ignored.)
If untrusted links are used for transit, which is NOT RECOMMENDED, If untrusted links are used for transit, which is NOT RECOMMENDED,
and therefore need to carry HNCP and Babel traffic, then HNCP and then any HNCP and Babel traffic that is carried over such links MUST
Babel MUST be secured using an upper-layer security protocol. While be secured using an upper-layer security protocol. While both HNCP
both HNCP and Babel support cryptographic authentication, at the time and Babel support cryptographic authentication, at the time of
of writing no protocol for autonomous configuration of HNCP and Babel writing no protocol for autonomous configuration of HNCP and Babel
security has been defined. security has been defined.
5. Acknowledgments 5. Acknowledgments
A number of people have helped with definining the requirements A number of people have helped with definining the requirements
listed in this document. I am especially indebted to Markus Stenberg listed in this document. I am especially indebted to Markus Stenberg
for his help. for his input.
6. References 6. References
6.1. Normative References 6.1. Normative References
[BABEL-SS] [BABEL-SS]
Boutier, M. and J. Chroboczek, "Source-Specific Routing in Boutier, M. and J. Chroboczek, "Source-Specific Routing in
Babel", draft-boutier-babel-source-specific-01 (work in Babel", draft-ietf-babel-source-specific-01 (work in
progress), January 2015. progress), August 2017.
[RFC6126] Chroboczek, J., "The Babel Routing Protocol", RFC 6126,
February 2011.
[RFC7557] Chroboczek, J., "Extension Mechanism for the Babel Routing [RFC6126bis]
Protocol", RFC 7557, May 2015. Chroboczek, J., "The Babel Routing Protocol", Internet
Draft draft-ietf-babel-rfc6126bis-02, May 2017.
[RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking [RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking
Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April
2016. 2016.
6.2. Informative References 6.2. Informative References
[BABEL-RTT] [BABEL-RTT]
Jonglez, B. and J. Chroboczek, "Delay-based Metric Jonglez, B. and J. Chroboczek, "Delay-based Metric
Extension for the Babel Routing Protocol", draft-jonglez- Extension for the Babel Routing Protocol", draft-jonglez-
skipping to change at page 8, line 18 skipping to change at page 8, line 18
[DELAY-BASED] [DELAY-BASED]
Jonglez, B. and J. Chroboczek, "A delay-based routing Jonglez, B. and J. Chroboczek, "A delay-based routing
metric", March 2014. metric", March 2014.
Available online from http://arxiv.org/abs/1403.3488 Available online from http://arxiv.org/abs/1403.3488
[RFC7298] Ovsienko, D., "Babel Hashed Message Authentication Code [RFC7298] Ovsienko, D., "Babel Hashed Message Authentication Code
(HMAC) Cryptographic Authentication", RFC 7298, July 2014. (HMAC) Cryptographic Authentication", RFC 7298, July 2014.
[ToS-SPECIFIC]
Chouasne, G., "https://tools.ietf.org/id/draft-chouasne-
babel-tos-specific-00.xml", draft-chouasne-babel-tos-
specific-00 (work in progress), July 2017.
Author's Address Author's Address
Juliusz Chroboczek Juliusz Chroboczek
IRIF, University of Paris-Diderot IRIF, University of Paris-Diderot
Case 7014 Case 7014
75205 Paris Cedex 13 75205 Paris Cedex 13
France France
Email: jch@irif.fr Email: jch@irif.fr
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