draft-ietf-homenet-babel-profile-03.txt   draft-ietf-homenet-babel-profile-04.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 October 25, 2017 Intended status: Standards Track January 3, 2018
Expires: April 28, 2018 Expires: July 7, 2018
Homenet profile of the Babel routing protocol Homenet profile of the Babel routing protocol
draft-ietf-homenet-babel-profile-03 draft-ietf-homenet-babel-profile-04
Abstract Abstract
This document defines the subset of the Babel routing protocol This document defines the subset of the Babel routing protocol
[RFC6126bis] and its extensions that a Homenet router must implement, [RFC6126bis] and its extensions that a Homenet router must implement,
as 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
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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 April 28, 2018. This Internet-Draft will expire on July 7, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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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
[RFC6126bis]. 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 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 RFC 6126bis [RFC6126bis] defines the Babel routing protocol. It o RFC 6126bis [RFC6126bis] defines the Babel routing protocol. It
allows Babel's control data to be carried over either link-local allows Babel's control data to be carried over either link-local
IPv6 or IPv4, and in either case allows announcing both IPv4 and IPv6 or IPv4, and in either case allows announcing both IPv4 and
IPv6 routes. It leaves link cost estimation, metric computation IPv6 routes. It leaves link cost estimation, metric computation
and route selection to the implementation. Distinct and route selection to the implementation. Distinct
implementations of RFC 6126 Babel will interoperate, in the sense implementations of RFC 6126bis Babel will interoperate, in the
that they will maintain a set of loop-free forwarding paths. sense that they will maintain a set of loop-free forwarding paths.
However, if they implement conflicting options, they might not be However, if they implement conflicting options, they might not be
able to exchange a full set of routes; in the worst case, an able to exchange a full set of routes; in the worst case, an
implementation that only implements the IPv6 subset of the implementation that only implements the IPv6 subset of the
protocol and an implementation that only implements the IPv4 protocol and an implementation that only implements the IPv4
subset of the protocol will not exchange any routes. In addition, subset of the protocol will not exchange any routes. In addition,
if implementations use conflicting route selection policies, if implementations use conflicting route selection policies,
persistent oscillations might occur. persistent oscillations might occur.
o The informative Appendix A of RFC 6126 suggests a simple and easy o The informative Appendix A of RFC 6126bis suggests a simple and
to implement algorithm for cost and metric computation that has easy to implement algorithm for cost and metric computation that
been found to work satisfactorily in a wide range of topologies. has 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 6126bis does not provide an algorithm for route
its Section 3.6 suggests selecting the route with smallest metric selection, its Section 3.6 suggests selecting the route with
with some hysteresis applied. An algorithm that has been found to smallest metric with some hysteresis applied. An algorithm that
work well in practice is described in Section III.E of has been found to work well in practice is described in
[DELAY-BASED]. Section III.E of [DELAY-BASED].
o Five RFCs and Internet-Drafts define optional extensions to Babel: o Five 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], delay-based routing [BABEL-RTT] and ToS-specific [BABEL-SS], delay-based routing [BABEL-RTT] and ToS-specific
routing [ToS-SPECIFIC]. All of these extensions interoperate with routing [ToS-SPECIFIC]. All of these extensions interoperate 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
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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
control data over IPv6. control data over IPv6.
REQ2: a Homenet implementation of Babel MUST implement the IPv6 REQ2: a Homenet implementation of Babel MUST implement the IPv6
subset of the protocol defined in the body of RFC 6126. subset of the protocol defined in the body of RFC 6126bis.
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 6126bis. Use of
techniques for acquiring IPv4 connectivity (such as multiple layers other techniques for acquiring IPv4 connectivity (such as multiple
of NAT) is strongly discouraged. layers of NAT) is strongly discouraged.
Rationale: support for IPv4 will likely remain necessary for years Rationale: support for IPv4 will likely remain necessary for years
to 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-ietf-babel-source- specific routing for IPv6, as defined in draft-ietf-babel-source-
specific [BABEL-SS]. specific [BABEL-SS].
Rationale: source-specific routing is an essential component of Rationale: source-specific routing is an essential component of
the Homenet architecture. Source-specific routing for IPv4 is not the Homenet architecture. 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 6126bis. 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 cause sub-optimal routing. will cause sub-optimal routing.
REQ6: 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 6126bis MAY
used. be 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".
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 6126bis 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
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.
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If untrusted links are used for transit, which is NOT RECOMMENDED, If untrusted links are used for transit, which is NOT RECOMMENDED,
then any HNCP and Babel traffic that is carried over such links MUST then any HNCP and Babel traffic that is carried over such links MUST
be secured using an upper-layer security protocol. While both HNCP be secured using an upper-layer security protocol. While both HNCP
and Babel support cryptographic authentication, at the time of and Babel support cryptographic authentication, at the time 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 defining the requirements listed
listed in this document. I am especially indebted to Markus Stenberg in this document. I am especially indebted to Barbara Stark, Markus
for his input. Stenberg, and Stephen Farrell.
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-ietf-babel-source-specific-01 (work in Babel", draft-ietf-babel-source-specific-01 (work in
progress), August 2017. progress), August 2017.
[RFC6126bis] [RFC6126bis]
Chroboczek, J., "The Babel Routing Protocol", Internet Chroboczek, J. and D. Schinazi, "The Babel Routing
Draft draft-ietf-babel-rfc6126bis-02, May 2017. Protocol", Internet Draft draft-ietf-babel-rfc6126bis-04,
October 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-
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