draft-ietf-homenet-babel-profile-00.txt   draft-ietf-homenet-babel-profile-01.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 8, 2016 Intended status: Experimental December 2, 2016
Expires: January 9, 2017 Expires: June 5, 2017
Homenet profile of the Babel routing protocol Homenet profile of the Babel routing protocol
draft-ietf-homenet-babel-profile-00 draft-ietf-homenet-babel-profile-01
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. [RFC6126] and its extensions that a Homenet router must implement, as
well as the interactions between HNCP 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
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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 9, 2017. This Internet-Draft will expire on June 5, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 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
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publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 12 skipping to change at page 2, line 12
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
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 . . . . . . . . . . . . . . . . . . . . 5
3. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 3. Interactions between HNCP and Babel . . . . . . . . . . . . . 5
4. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Normative References . . . . . . . . . . . . . . . . . . 6 3.2. Non-requirements . . . . . . . . . . . . . . . . . . . . 6
4.2. Informative References . . . . . . . . . . . . . . . . . 6 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Normative References . . . . . . . . . . . . . . . . . . 7
5.2. Informative References . . . . . . . . . . . . . . . . . 7
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
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 defines the exact subset of the Babel protocol and its This document consists of two parts. The first specifies the exact
extensions that is required by a conformant implementation of the subset of the Babel protocol and its extensions that is required by
Homenet protocol suite. an implementation of the Homenet protocol suite. The second
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 The body of RFC 6126 [RFC6126] defines the core, unextended
protocol. It allows Babel's control data to be carried over protocol. It allows Babel's control data to be carried over
either link-local IPv6 or IPv4, and in either case allows either link-local IPv6 or IPv4, and in either case allows
announcing both IPv4 and IPv6 routes. It leaves link cost announcing both IPv4 and IPv6 routes. It leaves link cost
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o Four RFCs and Internet-Drafts define optional extensions to Babel: 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], radio interference aware routing [BABEL-Z], and delay-
based routing [BABEL-RTT]. All of these extensions interoperate based routing [BABEL-RTT]. All of these extensions interoperate
with the core protocol as well as with each other. with 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
[Sentences within square brackets are editorial notes and are not
intended for publication.]
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.
Rationale: since Babel is able to carry both IPv4 and IPv6 routes Rationale: since Babel is able to carry both IPv4 and IPv6 routes
over either IPv4 or IPv6, choosing the protocol used for carrying over either IPv4 or IPv6, choosing the protocol used for carrying
control traffic is a matter of preference. Since IPv6 has some control traffic is a matter of preference. Since IPv6 has some
features that make implementations somewhat simpler and more features that make implementations somewhat simpler and more
reliable (notably link-local addresses), we require carrying reliable (notably link-local addresses), we require carrying
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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 remain necessary for years to
come, and even in pure IPv6 deployments, including code for 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.
[BS suggest that this should be a MUST.]
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-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]).
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used by third parties that are not necessarily fully trusted. In used by third parties that are not necessarily fully trusted. In
such networks, it is essential that either the routing protocol is such networks, it is essential that either the routing protocol is
secured or the guest links are carefully firewalled. secured or the guest links are carefully firewalled.
Generic mechanisms such as DTLS and dynamically keyed IPsec are Generic mechanisms such as DTLS and dynamically keyed IPsec are
not able to protect multicast traffic, and are therefore difficult not able to protect multicast traffic, and are therefore difficult
to use with Babel. Statically keyed IPsec, perhaps with keys to use with Babel. Statically keyed IPsec, perhaps with keys
rotated by HNCP, is vulnerable to replay attacks and would rotated by HNCP, is vulnerable to replay attacks and would
therefore require the addition of a nonce mechanism to Babel. therefore require the addition of a nonce mechanism to Babel.
[There is no consensus about this requirement. A simpler solution
is to disable Babel on guest interfaces. MS suggests this might
be a SHOULD.]
[This needs expanding with an explanation of how HNCP is supposed
to signal the use of authentication.]
REQ6: a Homenet implementation of Babel MUST use metrics that are of 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 lead to sub-optimal routing.
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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
computed metrics, the routing protocol attempts to minimise the computed metrics, the routing protocol attempts to minimise the
number of links crossed by a route, and therefore prefers long, number of links crossed by a route, and therefore prefers long,
lossy links to shorter, lossless ones. In wireless networks, lossy links to shorter, lossless ones. In wireless networks,
"hop-count routing is worst-path routing". "hop-count routing is worst-path routing".
[This should probably be MUST, but it might be difficult or even
impossible to implement in some environments, especially in the
presence of wired-to-wireless bridges.]
2.2. Non-requirements 2.2. Non-requirements
NR1: a Homenet implementation of Babel MAY perform route selection by NR1: a Homenet implementation of Babel MAY perform route selection by
applying hysteresis to route metrics, as suggested in Section 3.6 of applying hysteresis to route metrics, as suggested in Section 3.6 of
RFC 6126 and described in detail in Section III.E of [BABEL-RTT]. RFC 6126 and described in detail in Section III.E of [BABEL-RTT].
However, it MAY simply pick the route with the smallest metric. However, it MAY simply pick the route with the smallest metric.
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
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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: delay-based routing is useful in redundant meshes of
tunnels, which do not occur in typical home networks (which tunnels, which do not occur in typical home networks (which
typically use at most one VPN link). Interference-aware routing, typically use at most one VPN link). Interference-aware routing,
on the other hand, is likely to be useful in home networks, but on the other hand, is likely to be useful in home networks, but
the extension requires further evaluation before it can be the extension requires further evaluation before it can be
recommended for widespread deployment. recommended for widespread deployment.
3. Acknowledgments 3. Interactions between HNCP and Babel
4. References The Homenet architecture cleanly separates between configuration,
which is done by HNCP, and routing, which is done by Babel. While
the coupling between the two protocols is deliberately kept to a
minimum, some interactions are unavoidable.
4.1. Normative References All the interactions between HNCP and Babel consist of HNCP causing
Babel to perform an announcement on its behalf (in particular, under
no circumstances does Babel cause HNCP to perform an action). How
this is realised is an implementation detail that is outside the
scope of this document: while it could conceivably be done using a
private communication channel between HNCP and Babel, existing
implementations have HNCP install a route in the operating system's
kernel which is later picked up by Babel.
3.1. Requirements
REQ7: if an HNCP node receives a DHCPv6 prefix delegation for prefix
P and publishes an External-Connection TLV containing a Delegated-
Prefix TLV with prefix P and no Prefix-Policy TLV, then it MUST
announce a source-specific default route with source prefix P over
Babel.
Rationale: source-specific routes are the main tool that Homenet
uses to enable optimal routing in the presence of multiple IPv6
prefixes. External connections with non-trivial prefix policies
are explicitly excluded from this requirement, since their exact
behaviour is application-specific.
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
gateway and MUST announce a (non-specific) IPv4 default route over
Babel.
Rationale: the Homenet architecture does not use source-specific
routing for IPv4; instead, HNCP elects a single NAT gateway and
publishes a single default route towards that gateway (RFC 7788
Section 6.5).
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
towards P over Babel.
Rationale: prefixes assigned to links must be routable within the
Homenet.
3.2. Non-requirements
NR3: an HNCP node that receives a DHCPv6 prefix delegation MAY
announce a non-specific IPv6 default route over Babel in addition to
the source-specific default route mandated by requirement REQ7.
Rationale: since the source-specific default route is more
specific than the non-specific default route, the former will
override the latter if all nodes implement source-specific
routing. Announcing an additional non-specific route is allowed,
since doing that causes no harm and might simplify operations in
some circumstances, e.g. when interoperating with a rougint
protocol that does not support source-specific routing.
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-
specific IPv4 default route.
Homenet does not require support for IPv4 source-specific routing.
Announcing source-specific routes will not cause routing
pathologies (blackholes or routing loops), but it might cause
packets sourced in different parts of the Homenet to follow
different paths, with all the confusion that this entails.
4. Acknowledgments
5. References
5.1. 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 [RFC7298] Ovsienko, D., "Babel Hashed Message Authentication Code
(HMAC) Cryptographic Authentication", RFC 7298, July 2014. (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.
4.2. Informative References 5.2. 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.
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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 [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, <http://www.rfc-editor.org/info/rfc7788>. 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@pps.univ-paris-diderot.fr Email: jch@irif.fr
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