draft-ietf-homenet-babel-profile-01.txt   draft-ietf-homenet-babel-profile-02.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 December 2, 2016 Intended status: Experimental July 3, 2017
Expires: June 5, 2017 Expires: January 4, 2018
Homenet profile of the Babel routing protocol Homenet profile of the Babel routing protocol
draft-ietf-homenet-babel-profile-01 draft-ietf-homenet-babel-profile-02
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 [RFC6126] and its extensions that a Homenet router must implement, as
well as the interactions between HNCP and Babel. well as the interactions between HNCP [RFC7788] and Babel.
Status of This Memo Status of This Memo
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Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Background . . . . . . . . . . . . . . . . . . . . . . . 2
2. The Homenet profile of Babel . . . . . . . . . . . . . . . . 3 2. The Homenet profile of Babel . . . . . . . . . . . . . . . . 3
2.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Non-requirements . . . . . . . . . . . . . . . . . . . . 5 2.2. Non-requirements . . . . . . . . . . . . . . . . . . . . 4
3. Interactions between HNCP and Babel . . . . . . . . . . . . . 5 3. Interactions between HNCP and Babel . . . . . . . . . . . . . 5
3.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Non-requirements . . . . . . . . . . . . . . . . . . . . 6 3.2. Non-requirements . . . . . . . . . . . . . . . . . . . . 6
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Normative References . . . . . . . . . . . . . . . . . . 7 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2. Informative References . . . . . . . . . . . . . . . . . 7 6.1. Normative 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: [RFC6126]. 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
skipping to change at page 4, line 20 skipping to change at page 4, line 20
specific routing for IPv6, as defined in draft-boutier-babel-source- specific routing for IPv6, as defined in draft-boutier-babel-source-
specific [BABEL-SS]. This implies that it MUST implement the specific [BABEL-SS]. This implies that it MUST implement the
extension mechanism defined in RFC 7557. 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. The extension mechanism is required by
source-specific routing. 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 implement HMAC-based REQ5: a Homenet implementation of Babel MUST use metrics that are of
authentication, as defined in RFC 7298, MUST implement the two
mandatory-to-implement algorithms defined in RFC 7298, and MUST
enable and require authentication when instructed to do so by HNCP.
Rationale: some home networks include "guest" links that can be
used by third parties that are not necessarily fully trusted. In
such networks, it is essential that either the routing protocol is
secured or the guest links are carefully firewalled.
Generic mechanisms such as DTLS and dynamically keyed IPsec are
not able to protect multicast traffic, and are therefore difficult
to use with Babel. Statically keyed IPsec, perhaps with keys
rotated by HNCP, is vulnerable to replay attacks and would
therefore require the addition of a nonce mechanism to Babel.
REQ6: 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
values for link costs, combining routers from different vendors values for link costs, combining routers from different vendors
will lead to sub-optimal routing. will cause sub-optimal routing.
REQ7: a Homenet implementation of Babel SHOULD distinguish between REQ6: a Homenet implementation of Babel SHOULD distinguish between
wired and wireless links; if it is unable to determine whether a link wired and wireless links; if it is unable to determine whether a link
is wired or wireless, it SHOULD make the worst-case hypothesis that is wired or wireless, it SHOULD make the worst-case hypothesis that
the link is wireless. It SHOULD dynamically probe the quality of the link is wireless. It SHOULD dynamically probe the quality of
wireless links and derive a suitable metric from its quality wireless links and derive a suitable metric from its quality
estimation. The algorithm described in Appendix A of RFC 6126 MAY be estimation. The algorithm described in Appendix A of RFC 6126 MAY be
used. used.
Rationale: support for wireless transit links is a "killer Rationale: support for wireless transit links is a "killer
feature" of Homenet, something that is requested by our users and feature" of Homenet, something that is requested by our users and
easy to explain to our bosses. In the absence of dynamically easy to explain to our bosses. In the absence of dynamically
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Rationale: hysteresis is only useful in congested and highly Rationale: hysteresis is only useful in congested and highly
dynamic networks. In a typical home network, stable and dynamic networks. In a typical home network, stable and
uncongested, the feedback loop that hysteresis compensates for uncongested, the feedback loop that hysteresis compensates for
does not occur. does not occur.
NR2: a Homenet implementation of Babel MAY include support for other NR2: a Homenet implementation of Babel MAY include support for other
extensions to the protocol, as long as they are known to interoperate extensions to the protocol, as long as they are known to interoperate
with both the core protocol and source-specific routing. with both the core protocol and source-specific routing.
Rationale: delay-based routing is useful in redundant meshes of Rationale: a number of extensions to the Babel routing protocol
tunnels, which do not occur in typical home networks (which have been defined over the years; however, they are useful in
typically use at most one VPN link). Interference-aware routing, fairly specific situations, such as routing over global-scale
on the other hand, is likely to be useful in home networks, but overlay networks [BABEL-RTT] or multi-hop wireless networks with
the extension requires further evaluation before it can be multiple radio frequencies [BABEL-Z]. Hence, with the exception
recommended for widespread deployment. of source-specific routing, no extensions are required for
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 (in particular, under
no circumstances does Babel cause HNCP to perform an action). How no circumstances does Babel cause HNCP to perform an action). How
this is realised is an implementation detail that is outside the this is realised is an implementation detail that is outside the
scope of this document: while it could conceivably be done using a scope of this document: while it could conceivably be done using a
private communication channel between HNCP and Babel, existing private communication channel between HNCP and Babel, existing
implementations have HNCP install a route in the operating system's implementations have HNCP install a route in the operating system's
kernel which is later picked up by Babel. kernel which is later picked up by Babel using the existing
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.
Rationale: source-specific routes are the main tool that Homenet Rationale: source-specific routes are the main tool that Homenet
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are explicitly excluded from this requirement, since their exact are explicitly excluded from this requirement, since their exact
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 (RFC 7788 publishes a single default route towards that gateway ([RFC7788]
Section 6.5). 7788 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
NR3: an HNCP node that receives a DHCPv6 prefix delegation MAY NR3: an HNCP node that receives a DHCPv6 prefix delegation MAY
announce a non-specific IPv6 default route over Babel in addition to announce a non-specific IPv6 default route over Babel in addition to
the source-specific default route mandated by requirement REQ7. the source-specific default route mandated by requirement REQ7.
Rationale: since the source-specific default route is more Rationale: since the source-specific default route is more
specific than the non-specific default route, the former will specific than the non-specific default route, the former will
override the latter if all nodes implement source-specific override the latter if all nodes implement source-specific
routing. Announcing an additional non-specific route is allowed, routing. Announcing an additional non-specific route is allowed,
since doing that causes no harm and might simplify operations in since doing that causes no harm and might simplify operations in
some circumstances, e.g. when interoperating with a rougint some circumstances, e.g. when interoperating with a routing
protocol that does not support source-specific routing. protocol that does not support source-specific routing.
NR4: an HNCP node that receives a DHCPv4 lease with an IPv4 address NR4: an HNCP node that receives a DHCPv4 lease with an IPv4 address
and wins the election for NAT gateway SHOULD NOT announce a source- and wins the election for NAT gateway SHOULD NOT announce a source-
specific IPv4 default route. specific IPv4 default route.
Homenet does not require support for IPv4 source-specific routing. Homenet does not require support for IPv4 source-specific routing.
Announcing source-specific routes will not cause routing Announcing IPv4 source-specific routes will not cause routing
pathologies (blackholes or routing loops), but it might cause pathologies (blackholes or routing loops), but it might cause
packets sourced in different parts of the Homenet to follow packets sourced in different parts of the Homenet to follow
different paths, with all the confusion that this entails. different paths, with all the confusion that this entails.
4. Acknowledgments 4. Security Considerations
5. References Both HNCP and Babel carry their control data in IPv6 packets with a
link-local source address, and implementations are required to drop
packets sent from a global address. Hence, they are only susceptible
to attacks from a directly connected link on which the HNCP and Babel
implementations are listening.
5.1. Normative References The security of a Homenet network relies on having a set of trusted
"internal" links that are secured at a lower layer (either physically
or at the link layer); HNCP and Babel packets are only accepted when
they originate on these trusted links (see Section 5 of [RFC7788]).
External, leaf and guest links are not trusted, and any HNCP or Babel
packets that are received on such links are ignored.
If untrusted links are used for transit, which is NOT RECOMMENDED,
and therefore need to carry HNCP and Babel traffic, then HNCP and
Babel MUST be secured using an upper-layer security protocol. While
both HNCP and Babel support cryptographic authentication, at the time
of writing no protocol for autonomous configuration of HNCP and Babel
security has been defined.
5. Acknowledgments
A number of people have helped with definining the requirements
listed in this document. I am especially indebted to Markus Stenberg
for his help.
6. 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-boutier-babel-source-specific-01 (work in
progress), January 2015. progress), January 2015.
[RFC6126] Chroboczek, J., "The Babel Routing Protocol", RFC 6126, [RFC6126] Chroboczek, J., "The Babel Routing Protocol", RFC 6126,
February 2011. February 2011.
[RFC7298] Ovsienko, D., "Babel Hashed Message Authentication Code
(HMAC) Cryptographic Authentication", RFC 7298, July 2014.
[RFC7557] Chroboczek, J., "Extension Mechanism for the Babel Routing [RFC7557] Chroboczek, J., "Extension Mechanism for the Babel Routing
Protocol", RFC 7557, May 2015. Protocol", RFC 7557, May 2015.
5.2. Informative References [RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking
Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April
2016.
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-
babel-rtt-extension-01 (work in progress), May 2015. babel-rtt-extension-01 (work in progress), May 2015.
[BABEL-Z] Chroboczek, J., "Diversity Routing for the Babel Routing [BABEL-Z] Chroboczek, J., "Diversity Routing for the Babel Routing
Protocol", draft-chroboczek-babel-diversity-routing-01 Protocol", draft-chroboczek-babel-diversity-routing-01
(work in progress), February 2016. (work in progress), February 2016.
[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
[RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking [RFC7298] Ovsienko, D., "Babel Hashed Message Authentication Code
Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April (HMAC) Cryptographic Authentication", RFC 7298, July 2014.
2016, <http://www.rfc-editor.org/info/rfc7788>.
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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