Internet DRAFT - draft-chroboczek-homenet-babel-profile
draft-chroboczek-homenet-babel-profile
Network Working Group J. Chroboczek
Internet-Draft PPS, University of Paris-Diderot
Intended status: Experimental March 21, 2016
Expires: September 22, 2016
Homenet profile of the Babel routing protocol
draft-chroboczek-homenet-babel-profile-00
Abstract
This document defines the subset of the Babel routing protocol
[RFC6126] and its extensions that a Homenet router must implement.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 22, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Chroboczek Expires September 22, 2016 [Page 1]
Internet-Draft Babel Extension Mechanism March 2016
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . 2
2. The Homenet profile of Babel . . . . . . . . . . . . . . . . 3
2.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Non-requirements . . . . . . . . . . . . . . . . . . . . 5
3. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
4. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Normative References . . . . . . . . . . . . . . . . . . 6
4.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The core of the Homenet protocol suite consists of HNCP [HNCP], a
protocol used for flooding configuration information and assigning
prefixes to links, combined with the Babel routing protocol
[RFC6126]. Babel is an extensible, flexible and modular protocol:
minimal implementations of Babel have been demonstrated that consist
of a few hundred of lines of code, while the "large" implementation
includes support for a number of extensions and consists of over ten
thousand lines of C code.
This document defines the exact subset of the Babel protocol and its
extensions that is required by a conformant implementation of the
Homenet protocol suite.
1.1. Background
The Babel routing protocol and its extensions are defined in a number
of documents:
o The body of RFC 6126 [RFC6126] defines the core, unextended
protocol. It 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 routes. It leaves link cost
estimation, metric computation and route selection to the
implementation. Distinct implementations of core RFC 6126 Babel
will interoperate and maintain a set of loop-free forwarding
paths, but given conflicting metrics or route selection policies
may give rise to persistent oscillations.
o The informative Appendix A of RFC 6126 suggests a simple and easy
to implement algorithm for cost and metric computation that has
been found to work satisfactorily in a wide range of topologies.
Chroboczek Expires September 22, 2016 [Page 2]
Internet-Draft Babel Extension Mechanism March 2016
o While RFC 6126 does not provide an algorithm for route selection,
its Section 3.6 suggests selecting the route with smallest metric
with some hysteresis applied. An algorithm that has been found to
work well in practice is described in Section III.E of
[DELAY-BASED].
o The extension mechanism for Babel is defined in RFC 7557
[RFC7557].
o Four RFCs and Internet-Drafts define optional extensions to Babel:
HMAC-based authentication [RFC7298], source-specific routing
[BABEL-SS], radio interference aware routing [BABEL-Z], and delay-
based routing [BABEL-RTT]. All of these extensions interoperate
with the core protocol as well as with each other.
2. The Homenet profile of Babel
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
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-
local unicast address.
Rationale: since Babel is able to carry both IPv4 and IPv6 routes
over either IPv4 or IPv6, choosing the protocol used for carrying
control traffic is a matter of preference. Since IPv6 has some
features that make implementations somewhat simpler and more
reliable (notably link-local addresses), we require carrying
control data over IPv6.
REQ2: a Homenet implementation of Babel MUST implement the IPv6
subset of the protocol defined in the body of RFC 6126.
Rationale: support for IPv6 routing is an essential component of
the Homenet architecture.
REQ3: a Homenet implementation of Babel SHOULD implement the IPv4
subset of the protocol defined in the body of RFC 6126. Use of other
techniques for acquiring IPv4 connectivity (such as multiple layers
of NAT) is strongly discouraged.
Rationale: support for IPv4 will remain necessary for years to
come, and even in pure IPv6 deployments, including code for
supporting IPv4 has very little cost. Since HNCP makes it easy to
Chroboczek Expires September 22, 2016 [Page 3]
Internet-Draft Babel Extension Mechanism March 2016
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
problems.
[BS suggest that this should be a MUST.]
REQ4: a Homenet implementation of Babel MUST implement source-
specific routing for IPv6, as defined in draft-boutier-babel-source-
specific [BABEL-SS]. This implies that it MUST implement the
extension mechanism defined in RFC 7557.
Rationale: source-specific routing is an essential component of
the Homenet architecture. The extension mechanism is required by
source-specific routing. Source-specific routing for IPv4 is not
required, since HNCP arranges things so that a single non-specific
IPv4 default route is announced (Section 6.5 of [HNCP]).
REQ5: a Homenet implementation of Babel MUST implement HMAC-based
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.
[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
a similar magnitude to the values suggested in Appendix A of
RFC 6126. In particular, it SHOULD assign costs that are no less
than 256 to wireless links, and SHOULD assign costs between 32 and
196 to lossless wired links.
Chroboczek Expires September 22, 2016 [Page 4]
Internet-Draft Babel Extension Mechanism March 2016
Rationale: if two implementations of Babel choose very different
values for link costs, combining routers from different vendors
will lead to sub-optimal routing.
REQ7: a Homenet implementation of Babel SHOULD distinguish between
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
the link is wireless. It SHOULD dynamically probe the quality of
wireless links and derive a suitable metric from its quality
estimation. The algorithm described in Appendix A of RFC 6126 MAY be
used.
Rationale: support for wireless transit links is a "killer
feature" of Homenet, something that is requested by our users and
easy to explain to our bosses. In the absence of dynamically
computed metrics, the routing protocol attempts to minimise the
number of links crossed by a route, and therefore prefers long,
lossy links to shorter, lossless ones. In wireless networks,
"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
NR1: a Homenet implementation of Babel MAY perform route selection by
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].
However, it MAY simply pick the route with the smallest metric.
Rationale: hysteresis is only useful in congested and highly
dynamic networks. In a typical home network, stable and
uncongested, the feedback loop that hysteresis compensates for
does not occur.
NR2: a Homenet implementation of Babel MAY include support for other
extensions to the protocol, as long as they are known to interoperate
with both the core protocol and source-specific routing.
Rationale: delay-based routing is useful in redundant meshes of
tunnels, which do not occur in typical home networks (which
typically use at most one VPN link). Interference-aware routing,
on the other hand, is likely to be useful in home networks, but
the extension requires further evaluation before it can be
recommended for widespread deployment.
Chroboczek Expires September 22, 2016 [Page 5]
Internet-Draft Babel Extension Mechanism March 2016
3. Acknowledgments
4. References
4.1. Normative References
[BABEL-SS]
Boutier, M. and J. Chroboczek, "Source-Specific Routing in
Babel", draft-boutier-babel-source-specific-01 (work in
progress), January 2015.
[RFC6126] Chroboczek, J., "The Babel Routing Protocol", RFC 6126,
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
Protocol", RFC 7557, May 2015.
4.2. Informative References
[BABEL-RTT]
Jonglez, B. and J. Chroboczek, "Delay-based Metric
Extension for the Babel Routing Protocol", draft-jonglez-
babel-rtt-extension-01 (work in progress), May 2015.
[BABEL-Z] Chroboczek, J., "Diversity Routing for the Babel Routing
Protocol", draft-chroboczek-babel-diversity-routing-00
(work in progress), July 2014.
[DELAY-BASED]
Jonglez, B. and J. Chroboczek, "A delay-based routing
metric", March 2014.
Available online from http://arxiv.org/abs/1403.3488
[HNCP] Stenberg, M., Barth, S., and P. Pfister, "Home Networking
Control Protocol", draft-ietf-homenet-hncp-09 (work in
progress), August 2015.
Author's Address
Chroboczek Expires September 22, 2016 [Page 6]
Internet-Draft Babel Extension Mechanism March 2016
Juliusz Chroboczek
PPS, University of Paris-Diderot
Case 7014
75205 Paris Cedex 13
France
Email: jch@pps.univ-paris-diderot.fr
Chroboczek Expires September 22, 2016 [Page 7]