6MAN J. Hui
Internet-Draft Arch Rock Corporation
Intended status: Standards Track JP. Vasseur
Expires: November 27, 2010 Cisco Systems, Inc
D. Culler
UC Berkeley
May 26, 2010
A Source Routing Header for RPL
draft-hui-6man-rpl-routing-header-00
Abstract
In Low power and Lossy Networks (LLNs), memory constraints on routers
may limit them to maintaining at most a few routes. In some
configurations, it is necessary to use these memory constrained
routers to deliver datagrams to nodes within the LLN. The Routing
for Low Power and Lossy Networks (RPL) protocol can be used in some
deployments to store most, if not all, routes on one (e.g. the
Directed Acyclic Graph (DAG) root) or few routers and forward the
IPv6 datagram using a source routing technique to avoid large routing
tables on memory constrained routers. This document specifies a new
IPv6 Routing header type for delivering datagrams within a RPL
domain.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 27, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Format of the RPL Routing Header . . . . . . . . . . . . . . . 4
3. RPL Router Behavior . . . . . . . . . . . . . . . . . . . . . 6
4. RPL Border Router Behavior . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5.1. Source Routing Attacks . . . . . . . . . . . . . . . . . . 9
5.2. ICMPv6 Attacks . . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
Routing for Low Power and Lossy Networks (RPL) is a distance vector
IPv6 routing protocol designed for Low Power and Lossy networks (LLN)
[I-D.ietf-roll-rpl]. Such networks are typically constrained in
resources (limited communication data rate, processing power, energy
capacity, memory). In particular, some LLN configurations may
utilize LLN routers where memory constraints limit nodes to
maintaining only a small number of default routes and no other
destinations. However, it may be necessary to utilize such memory-
constrained routers to forward datagrams and maintain reachability to
destinations within the LLN.
To utilize paths that include memory-constrained routers, RPL relies
on source routing from more capable RPL routers. RPL provides the
necessary mechanisms to collect routing information at more capable
RPL routers and form paths from those routers to arbitrary
destinations within the RPL domain. However, a a source routing
mechanism supported by IPv6 is needed to deliver datagrams.
This document specifies the Type 4 Routing header (RH4) (to be
confirmed by IANA) for use strictly within a RPL domain. The basic
format of RH4 draws from that of the Type 0 Routing header (RH0)
[RFC2460]. However, RH4 introduces mechanisms to compact the source
route entries when all entries share the same prefix with the IPv6
Destination Address of the encapsulating header, a typical scenario
in LLNs using source routing. The compaction mechanism reduces
consumption of scarce resources such as bandwidth.
RH4 also differs from RH0 in the processing rules to alleviate
security concerns that lead to the deprecation of RH0 [RFC5095].
Unlike RH0, routers processing RH4 must implement a strict source
route policy where each and every IPv6 hop is specified within the
datagram itself. Furthermore, a RH4 header must only be used within
a RPL domain. RPL Border Routers, responsible for connecting RPL
domains and IP domains that use other routing protocols, may insert a
RH4 header into datagrams entering the RPL domain but must not allow
datagrams already carrying a RH4 header to enter or exit the RPL
domain.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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2. Format of the RPL Routing Header
The Type 4 Routing header has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type=4| Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Compr | Pad | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Addresses[1..n] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Next Header 8-bit selector. Identifies the type of header
immediately following the Routing header. Uses
the same values as the IPv4 Protocol field
[RFC3232].
Hdr Ext Len 8-bit unsigned integer. Length of the Routing
header in 8-octet units, not including the first
8 octets. Note that when Addresses[1..n] are
compressed (i.e. value of Compr is not 0), Hdr
Ext Len does not equal twice the number of
Addresses.
Routing Type 8-bit selector. Set to 4 (to be confirmed by
IANA).
Segments Left 8-bit unsigned integer. Number of route segments
remaining, i.e., number of explicitly listed
intermediate nodes still to be visited before
reaching the final destination. Value MUST be
between 0 and Segments, inclusive.
Compr 4-bit unsigned integer. Number of prefix octets
from each segment that is elided. For example, a
Type 4 Routing header carrying full IPv6
addresses sets Compr to 0.
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Pad 4-bit unsigned integer. Number of octets that
are used to for padding after Address[n] and the
end of the Type 4 Routing header.
Address[1..n] Vector of addresses, numbered 1 to n. Each
vector element has size (16 - Compr).
The Type 4 Routing header shares the same basic format as the Type 0
Routing header [RFC2460]. When carrying full IPv6 addresses, the
Compr and Pad fields are set to 0 and the only difference between the
Type 4 and Type 0 encodings is the value of the Routing Type field.
A common network configuration for a RPL domain is that all nodes
within a LLN share a common prefix. Type 4 Routing header introduces
the Compr and Pad fields to allow compaction of the Address[1..n]
vector when all entries share the same prefix as the IPv6 Destination
Address field of the encapsulating packet. The Compr field indicates
the number of prefix octets that are shared with the IPv6 Destination
Address of the encapsulating header. The shared prefix octets are
not carried within the Routing header and each entry in Address[1..n]
has size (16 - Compr) octets. When Compr is non-zero, there may
exists unused octets between the last entry, Address[n], and the end
of the Routing header. The Pad field indicates the number of unused
octets that are used for padding. Note that when Compr is 0, Pad
MUST be null and carry a value of 0.
IPv6 Addresses MUST NOT appear more than once in a Type 4 Routing
header. The IPv6 Destination Address of the encapsulating packet
MUST NOT appear in a Type 4 Routing header.
Multicast addresses MUST NOT appear in a Type 4 Routing header, or in
the IPv6 Destination Address field of a packet carrying a Type 4
Routing header.
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3. RPL Router Behavior
A RPL Router MAY insert a Type 4 Routing header if one does not
already exist. The conditions for inserting a Type 4 Routing header
are out of scope of this document.
As specified in [RFC2460], a routing header is not examined or
processed until it reaches the node identified in the Destination
Address field of the IPv6 header. In that node, dispatching on the
Next Header field of the immediately preceding header causes the
Routing header module to be invoked.
The function of Type 4 Routing header is intended to be very similar
to IPv4's Strict Source and Record Route option [RFC0791]. When
processing the Type 4 Routing header, a router MUST drop the packet
if the next entry is not a neighboring node and SHOULD send an ICMP
Destination Unreachable (ICMPv6 Type 1) message with ICMPv6 Code set
to 7 (to be confirmed by IANA) to the packet's Source Address. An
ICMPv6 Code of 7 indicates that the router does not have the next
Address entry as a neighbor and cannot satisfy the strict source
route. When generating ICMPv6 error messages, the rules in Section
2.4 of [RFC4443] must be observed.
The following describes the algorithm performed when processing a
Type 4 Routing header:
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if Segments Left = 0 {
proceed to process the next header in the packet, whose type is
identified by the Next Header field in the Routing header
}
else {
compute n, the number of addresses in the Routing header, by
n = ((Hdr Ext Len * 8) - Pad) / (16 - Comp)
if Segments Left is greater than n {
send an ICMP Parameter Problem, Code 0, message to the Source
Address, pointing to the Segments Left field, and discard the
packet
}
else {
decrement Segments Left by 1;
compute i, the index of the next address to be visited in
the address vector, by subtracting Segments Left from n
if Address[i] or the IPv6 Destination Address is multicast {
discard the packet
}
else if Address[i] is not an neighboring node {
send an ICMP Destination Unreachable, Code 3, message to
the Source Address and discard the packet
}
else {
swap the IPv6 Destination Address and Address[i]
if the IPv6 Hop Limit is less than or equal to 1 {
send an ICMP Time Exceeded -- Hop Limit Exceeded in
Transit message to the Source Address and discard the
packet
}
else {
decrement the Hop Limit by 1
resubmit the packet to the IPv6 module for transmission
to the new destination
}
}
}
}
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4. RPL Border Router Behavior
RPL Border Routers (referred to as LBRs in
[I-D.ietf-roll-terminology] are responsible for ensuring that a Type
4 Routing header is only used within the RPL domain it was created.
RPL Border Routers MUST drop datagrams entering or exiting the RPL
domain that contain a Type 4 Routing header in the IPv6 Extension
headers.
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5. Security Considerations
5.1. Source Routing Attacks
[RFC5095] deprecates the Type 0 Routing header due to a number of
significant attacks that are referenced in that document. Such
attacks include network discovery, bypassing filtering devices,
denial-of-service, and defeating anycast.
Because this document specifies that Type 4 Routing headers are only
for use within a RPL domain, such attacks cannot be mounted from
outside the RPL domain. As described in Section 4, RPL Border
Routers MUST drop datagrams entering or exiting the RPL domain that
contain a Type 4 Routing header in the IPv6 Extension headers.
5.2. ICMPv6 Attacks
The generation of ICMPv6 error messages may be used to attempt
denial-of-service attacks by sending error-causing Type 4 Routing
headers in back-to-back datagrams. An implementation that correctly
follows Section 2.4 of [RFC4443] would be protected by the ICMPv6
rate limiting mechanism.
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6. IANA Considerations
This document defines a new IPv6 Routing Type of 4 (to be confirmed).
This document defines a new ICMPv6 Destination Unreachable Code of 7
to indicate that the router does not have the next Address element as
a neighbor and could not satisfy the strict source route.
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7. Acknowledgements
TODO.
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8. References
8.1. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
of Type 0 Routing Headers in IPv6", RFC 5095,
December 2007.
8.2. Informative References
[I-D.ietf-roll-rpl]
Winter, T., Thubert, P., and R. Team, "RPL: IPv6 Routing
Protocol for Low power and Lossy Networks",
draft-ietf-roll-rpl-07 (work in progress), March 2010.
[I-D.ietf-roll-terminology]
Vasseur, J., "Terminology in Low power And Lossy
Networks", draft-ietf-roll-terminology-03 (work in
progress), March 2010.
[RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by
an On-line Database", RFC 3232, January 2002.
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Authors' Addresses
Jonathan W. Hui
Arch Rock Corporation
501 2nd St. Ste. 410
San Francisco, California 94107
USA
Phone: +415 692 0828
Email: jhui@archrock.com
JP Vasseur
Cisco Systems, Inc
11, Rue Camille Desmoulins
Issy Les Moulineaux, 92782
France
Email: jpv@cisco.com
David E. Culler
UC Berkeley
465 Soda Hall
Berkeley, California 94720
USA
Phone: +510 643 7572
Email: culler@cs.berkeley.edu
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