Neighbor Management Policy for 6LoWPAN
draft-ietf-lwig-nbr-mgmt-policy-01
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| Authors | Rahul Jadhav , Rabi Narayan Sahoo , Simon Duquennoy , Joakim Eriksson | ||
| Last updated | 2018-02-22 (Latest revision 2017-08-28) | ||
| Replaces | draft-jadhav-lwig-nbr-mgmt-policy | ||
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draft-ietf-lwig-nbr-mgmt-policy-01
LWIG R. Jadhav, Ed.
Internet-Draft R. Sahoo
Intended status: Informational Huawei
Expires: August 26, 2018 S. Duquennoy
Inria
J. Eriksson
Yanzi Networks
February 22, 2018
Neighbor Management Policy for 6LoWPAN
draft-ietf-lwig-nbr-mgmt-policy-01
Abstract
This document describes the problems associated with neighbor cache
management in constrained multihop networks and a sample neighbor
management policy to deal with it.
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 August 26, 2018.
Copyright Notice
Copyright (c) 2018 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
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language and Terminology . . . . . . . . . . 4
2. Neighbor Management . . . . . . . . . . . . . . . . . . . . . 5
2.1. Significance of Neighbor management policy . . . . . . . 5
2.2. Trivial neighbor management policies . . . . . . . . . . 6
2.3. Lifecycle of a NCE . . . . . . . . . . . . . . . . . . . 7
2.3.1. NCE Insertion . . . . . . . . . . . . . . . . . . . . 7
2.3.2. NCE Deletion . . . . . . . . . . . . . . . . . . . . 10
2.3.3. NCE Eviction . . . . . . . . . . . . . . . . . . . . 11
2.3.3.1. Eviction for directly connected routing entries . 11
2.3.4. NCE Reinforcement . . . . . . . . . . . . . . . . . . 12
2.4. Requirements of a good neighbor management policy . . . . 12
2.5. Approaches to neighbor management policy . . . . . . . . 13
2.5.1. Reactive Approach . . . . . . . . . . . . . . . . . . 13
2.5.2. Proactive Approach . . . . . . . . . . . . . . . . . 13
3. Reservation based Neighbor Management Policy . . . . . . . . 14
3.1. Limitations of such a policy . . . . . . . . . . . . . . 15
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. Normative References . . . . . . . . . . . . . . . . . . 16
7.2. Informative References . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
In a wireless multihop network, the node densities (maximum number of
devices connected on a single hop) may vary significantly depending
upon deployments/scenarios. While there is some policy control
possible with regards to the network size in terms of maximum number
of devices connected, it is especially difficult to set a figure on
what will be the maximum node density given a deployment. For e.g.
A network can put an upper limit on max 1000 devices but it is
impossible to state what the node density will be in this 1000 node
network.
A neighbor cache is used for populating neighboring one-hop connected
nodes information such as MAC address, link local IP address and
other reachability state information. Node density has direct
implications on the neighbor cache and in constrained network
scenario the size of the neighbor cache will be limited. Thus there
are chances that a node may not be able to fit all the neighboring
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nodes in its cache in which case it has to prioritize entries and
thus needs a neighbor management policy.
This draft presents problems related to neighbor management policies
by considering a security-enabled multi-hop 6lo network. This
document considers RPL [RFC6550] as a routing protocol and PANA (EAP-
PANA) [RFC5191] as a network access protocol. For RPL, both the
storing and non-storing mode of operations are considered. We also
provide a sample neighbor management policy which can be used in such
networks and its limitations. The aim of such a policy is to retain
set of neighbor cache entries with high quality links such that
routing adjacencies are stablized.
The problem statement and the proposed solution described is also
relevant to other multihop constrained scenarios such as 6TiSCH
[I-D.ietf-6tisch-architecture]. [I-D.ietf-6tisch-minimal-security]
talks about a pledge (new joinee) node authenticating via a Join
Proxy. The considerations mentioned in this document are applicable
for such networks as well.
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+--------+
| PAA/ |
+------| Auth |
| | Server |
| +--------+
+------------|-------------+
| | |
| (BR) |
| / \ |
| / \ |
| / \ |
| (N1) (N2) |
| / : / \ |
| / : / \ |
| / : / \ |
| (N8) (N3) (N4) |
| : / \ : |
| : / \ : |
| : / \ : |
| (N5) (New) |
| / \ |
| / \ |
| / \ |
| (N6) (N7) |
| |
| 6Lo Network |
+--------------------------+
Figure 1: Sample Topology
1.1. Requirements Language and Terminology
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 RFC 2119 [RFC2119].
PaC (PANA Client): New joining node which is yet to be authenticated.
PRE (PANA Relay Element): An already authenticated and network joined
node which is willing to act as a relay element for PaCs to complete
their authentication procedure on multi-hop networks. [RFC6345]
describes the details of PRE.
PAA (PANA Auth Agent): Auth server which hosts the credentials
database. PaC will handshake with PAA to complete authentication
procedure.
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Routing Child: A downstream node who is part of the routing table of
the parent. For e.g. in the sample topology above N5 is the directly
connected routing child for N3. N6 and N7 are also part of N3
routing table, they are routing child nodes but not directly
connected. For N6 and N7 the document might alternatively use a term
grand-child.
Routing Parent: In Figure 1, N1 and N2 are possible routing parents
for N3.
Neighbor Cache Entry (NCE): A neighbor entry managed on behalf of
directly connected peer.
This document also uses terminology described in [RFC6550] and
[RFC6775].
2. Neighbor Management
2.1. Significance of Neighbor management policy
Multihop mesh networks present unique challenges to neighbor
management especially with resource constrained nodes. In cases
where the node density is higher that the neighbor cache size, the
entries have to be prioritized. [Woo_et_al] and [Dawans_et_al] talk
about prioritization of neighbor entries by using link quality
estimation techniques. But prioritization alone may not necessarily
be optimal in all cases. The reason or function why neighbor entry
was added also needs to be taken in consideration. For example,
evicting a routing direct child might have a ripple effect in turn
impacting all the sub-childs as well.
In case of key management protocols deployed above MAC layer in
multihop network, the neighbor management kicks in early even before
the routing adjacencies are established. Since a new joining node
needs to discover/attach to a relay element for completing its
authentication procedure, the neighbor cache entries have to be
appropriately populated both on a PaC and on the PRE. If a neighbor
entry whose authentication is in progress is evicted, it will
negatively impact the authentication procedure.
Another important consideration is that with increased node density,
the prioritization based on link estimation parameters might not help
since there might be more well connected peers. In dense deployments
the number of directly attached neighbors with good quality links
might still be higher than the max entries in neighbor cache size.
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2.2. Trivial neighbor management policies
This section investigates policies which are used by most of the
current operating systems for constrained nodes. While such policies
are trivial to implement they may not be able to deal with the
constrained network scenario. Note that such policies can still be
used if it is known apriori that the neighbor cache can hold entries
for maximum node density.
a. First Come First Serve (FCFS) policy
b. Least Recently Used (LRU) policy
The primary distinction between these policies is how it treats a new
entry when the neighbor cache is full. In case of FCFS policy, the
new entry is simply rejected while with LRU, the new entry replaces
the least recently used entry.
RPL works by initiating a downstream multicast DIO to establish
upstream network path. Subsequently DAO messages might be sent by
the nodes to establish downstream paths to the nodes. Thus the
network is flooded with multicast DIO messages initially and
similarly there are chances that the same node is ended up been
selected as a preferred parent by most of the child nodes and thus
receives a DAO message from all these child nodes. Note that once a
node establishes a parent entry or a routing entry on behalf of a
directly connected node then it has to also provision a neighbor
cache entry for it for subsequent unicast traffic.
In case of FCFS policy, a node might end up hosting all the neighbor
entries based on DIO or DAO messages. Once the cache is full all the
subsequent attempts to add an NCE will fail.
In case of LRU policy, a node might end up churning lot of neighbor
entries because once the cache gets full and there is a request for
new entry, it would result in evicting the least recently used (but
active) entry. If at later point of time, there is a traffic for the
evicted entry then the old entry has to be reinstated using IPv6 NDP
procedure. This would mean reinstating the entry by evicting another
least recently used entry. If the node density is very high, then
this churn would be substantially high to extent that it would
disrupt any routing adjacencies to be established in the network in a
stable way.
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2.3. Lifecycle of a NCE
2.3.1. NCE Insertion
IPv6 NDP [RFC6775] defines signaling involved in resolving the IPv6
addresses to its corresponding MAC addresses which gets populated in
the neighbor cache. In case of constrained network, it is desired
that such control traffic is minimized and thus the neighbor cache
entries are populated as part of existing messaging. One example
would be when the node receives a DAO message from its immediate
child node, it not only makes an addition to the routing table but
also creates a neighbor cache entry for the node. Thus it eliminates
need for additional IPv6 NDP NS/NA messaging involved to resolve MAC
address. Similar hueristic is used to add neighbor entries in other
cases as well. Section 10.3.2 of [RFC6775] describes update and
addition of such NCEs based on roting information packets.
Following are the possible signaling scenarios in which case a
neighbor entry may get added.
Node Joining procedure: A new joinee node discovers a relay element
to initiate its auth procedure. At the end of the discovery phase
the new joinee node would have known the link local IP address of the
relay element. The joinee node will send an unsecured-NS to the
relay element to solicit its NA. The PRE may send a NA with the
suitable status code as defined in section 6.5.3 of [RFC6775].
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RPL
New PRE Parent PAA
| | | |
| PRE Disc | | |
|<----------->| | |
| | | |
| UNSEC-NS | | |
|------------>| | |
| | | |
| addNCE(new,reason=PANA)| |
| | | |
| UNSEC-NA(status) | |
|<------------| | |
| | | |
addNCE(PRE,reason=PANA) | |
| | | |
| PCI | | |
|------------>| | |
| | | |
| | AUTHPROC | |
|<----------->|<----------------------->|
| | | |
Figure 2: NCE creation between PaC and PRE during relay discovery
process
Relay element does not hold any state information on behalf of the
new joinee node except for its neighbor cache entry. Thus in the
Figure 1 the new joinee node may select node N3 as its PRE, in which
case N3 has to add a neighbor entry on behalf of the new joinee node.
Post authentication the node enters into network discovery phase.
The node selects one or more of its neighboring peer as its preferred
parent based on the DIO received from these peers. Note that the
node's selected relay element and its preferred parent may not be
same. The preferred parent serves as a default router node to which
all its upstream traffic is directed. Thus an NCE on behalf of
preferred parent needs to be added. In Figure 1 node N5 selects N3
as its preferred parent. N5 needs to add neighbor entry on behalf of
N3 which is its directly connected RPL preferred parent.
In case of RPL storing MOP (mode of operation), the node may send a
DAO message containing its reachability information to its preferred
parent. The parent node in turn may pass this information upstream
to its parent by generating a DAO retaining the child node's
reachability information, establishing a downstream routing path
towards the node who originated the DAO. The preferred parent has to
maintain a neighbor entry on behalf of the directly connected child
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node. For example, in the Figure 1, node N3 needs to maintain a
neighbor entry on behalf of N5 which is its directly connected child
node. Nodes N6 and N7 are grand-child nodes for node N3 for whom no
neighbor entry is required.
As mentioned in Section 10.3.2 of [RFC6775], the NCEs on parent and
child can be added directly as a result of RPL DIO/DAO signalling
without any explicit NS/NA messaging.
RPL
New PRE Parent PAA
| | | |
| | AuthProc | |
|<----------->|<----------------------->|
| | | |
| | RPL-DIO | |
|<-------------------------| |
| | | |
addNCE(parent,reason=PARENT) | |
| | | |
| | RPL-DAO | |
|------------------------->| |
| | | |
| | addNCE(new,reason=CHILD)
| | | |
Figure 3: NCE creation call Flow for RPL storing MOP
In case of non-storing MOP, the parent node needs to know the global
IPv6 address of the immediate child nodes. This is needed since the
source routing header carries the global addresses and thus the NCE
of the child node should contain the global address. Secondly, the
RPL DAO is addressed directly to the root node in case of non-storing
mode. Thus RPL messaging cannot be used for creating NCE entries on
parent and child, unlike storing MOP. The child node may send a
secure unicast NS with ARO option containing its global address to be
registered on the parent node. The child node can still use RPL DIO
to create an NCE on behalf of the parent node.
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RPL
New PRE Parent Root
| | | |
| | AuthProc | |
|<----------->|<----------------------->|
| | | |
| | RPL-DIO | |
|<-------------------------| |
| | | |
addNCE(parent,reason=PARENT) | |
| | | |
| sec-NS(ARO=GlobalIPv6) | |
|------------------------->| |
| | | |
| | addNCE(new,reason=CHILD)
| sec-NA(status) | |
|<-------------------------| |
| | | |
| | RPL-DAO | |
|-------------------------------------->|
| | | |
Figure 4: NCE creation call Flow for non-storing MOP
This document expects the neighbor management policy to remember the
reason why the neighbor entry is inserted. Secondly, the router may
remember whether the NS received was secured or unsecured and
accordingly use it to prioritize eviction entries. As described in
the next sections, this reason will help the policy to prioritize the
entries in case an eviction is required.
2.3.2. NCE Deletion
It is imperative that an unwanted neighbor entry be removed as soon
as possible. This section talks about different cases in which
neighbor entry can be deleted.
Route Invalidation: In case of storing MOP, when the child node
decides to switch its preferred parent, the RPL specifications allows
the node to send a no-path DAO message to invalidate the route along
the previous path(s). A directly connected parent node can use this
message to clear the NCE. While the entry can be immediately
cleared, usually the implementations choose to wait a small amount of
time before clearing the entry. This is to avoid any impact on the
in-transit traffic. Thus this also establishes the importance of
route invalidation to achieve optimized neighbor cache utilization.
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In case of non-storing mode, the no-path DAO cannot be not employed
since the previous parent does not having any routing information to
be invalidated. But the previous parent may still contain the NCE on
behalf of the child node. This document recommends use of [RFC6775]
section 6.5.3. which allows sending a zero lifetime ARO option in NS
for deregistering the corresponding neighbor entry.
[RFC6775], ND optimizations for 6LoWPANs, section 5.5.3. talks about
deleting the entries in case the NUD (neighbor unreachability
detection) fails either due to no response to NS messages or due to
failure response. NCEs in such cases should be deleted. An example
where NUD NS would fail because of no response is the case where the
child node switches its parent due to link unavailability. The
parent in such a case would not receive the no-path DAO message or
any other traffic from the child node. Thus on NCE lifetime expiry,
the parent node would send NS which would fail with no response, thus
triggering entry deletion.
2.3.3. NCE Eviction
The eviction rules have a major impact on the neighbor management
policy. Eviction rules are used when the policy has to forcibly
remove an active neighbor entry from the cache to make space for the
new (hopefully higher priority) entry. The eviction policy may take
into account several considerations such as the reason why the entry
was made, is the entry in active use currently, how good (for e.g.,
based on link estimation) the entry currently is.
2.3.3.1. Eviction for directly connected routing entries
This section talks about implications of an eviction in which a
parent node decides of evicting a directly connected routing child
NCE. In the sample topology Figure 1, lets assume N3 needs to evict
N5 from its neighbor cache. In case of RPL's storing MOP, eviction
of directly connected routing child NCE also has impact on all the
sub-children. Thus not only will it result in impacting N5 but also
nodes N6 and N7. It is important to note that such an eviction has
less impact on RPL's non-storing MOP i.e. in case of non-storing mode
N5 might end up selecting alternate parent N8 and does not result in
any additional control overhead for node N6 and N7.
Thus RPL's non-storing MOP provides additional eviction flexibility
for a neighbor management policy in terms evicting directly connected
child entries.
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2.3.4. NCE Reinforcement
It is expected that the latest reachability state and metric
information be maintained in context to the NCE. With wireless
networks, the neighbor cache entries prioritization may change over a
period of time especially the link quality estimation parameters or
the routing metrics. Reinforcement refers to updating the parameters
in context to the NCEs which helps in prioritizing the entries when
it comes to handling eviction. In wireless networks, on reception of
incoming packet, the receiver node's physical and MAC layer may
derive certain signal reception parameters (such as RSSI, LQI) which
can be considered for reinforcement purpose if the corresponding
transmitter/source entry in neighbor cache is found. It should be
noted that the signal quality parameters may have high variance in
6lo networks and thus statistical techniques (such as weighted
averaging) are usually employed for deciding about a link quality
over a period of time. Reinforcement can be achieved using one or
more of the following techniques:
Passive Monitoring: Reinforcing the quality parameters using packets
received from the source. Trickled DIO, periodic beacons,
application traffic etc can be used for such monitoring.
Active Probing: A node may select subset of entries for active
probing wherein it sends a message to the neighbor entry's target
and can expect a response message back. An example of such
probing is [CONTIKI] where unicast DIS is sent to solicit a
unicast DIO without impacting the trickle timers. Though it adds
a control overhead on the link, periodic probing can help to
ascertain connectivity in the absence of any other traffic from
the neighboring node.
2.4. Requirements of a good neighbor management policy
Route Stability: Stable NCEs will result in stable routing
adjacencies. Thus it is important to avoid unnecessary NCE churn
for routing path stability.
Control overhead: A neighbor management policy may have to use
signalling messages for policy handling (such as rejection of
NCE). It is required that such overhead be kept as low as
possible.
Scalability: Scalability with respect to large and uneven node
densities in the network.
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2.5. Approaches to neighbor management policy
Neighbor management policy depends upon the neighbor cache space
availability and the same can be advertised proactively or can be
handled reactively.
2.5.1. Reactive Approach
In this approach, the nodes select their RPL parent or the relay
element purely based on link metrics and subsequently when they try
to allocate their NCE in the target node, it may fail due to
unavailability of the cache space. The failure can be communicated
depending upon the signaling involved:
NS failure: Section 6.5.3 of [RFC6775] defines a procedure for NS
failure handling in case the router's neighbor cache is full. It
results in a unicast NA with ARO status field set to two.
DAO NACK: Section 9.3 of RPL [RFC6550] specifies on how can the
parent node react to DAOs from child. In case the parent could
not make a NCE on behalf of the child node, a negative ACK with
status (between 127-255) should be sent to the child node. The
natural reaction of the child node would be to switch to an
alternate parent.
PANA Failure: PaC's auth session starts with a PaC discovering a
PRE. The discovery procedure is not standardized and can be based
upon various factors including signal strength of discovery
messages from PRE. Post discovery, the PaC needs to send an
unsecured unicast NS message with an ARO containings its link-
local IPv6 address. NS helps to determine whether the PRE can
allocate an NCE for the PaC. PRE accordingly sends a NA response
with appropriate status field.
2.5.2. Proactive Approach
Neighbor cache availability could be proactively advertised by the
parent nodes in the DIO messages and in the PRE discovery messages.
A child RPL node may additionally use this information from DIO as
part of parent selection process. In case of new joinee node, the
node may use PRE discovery messages with space availability
information to select an appropriate PRE. Proactive signaling of
neighbor cache space availability will help the nodes to select the
parent node or relay node such that the failure signaling due to
cache full event can be reduced.
Currently there is no standard way of signaling such neighbor cache
space availability information. RPL's DIO messages carry metric
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information and can be augmented with neighbor cache space as an
additional metric. In case of PRE discovery however there is no
standard way of defining this information since the PRE discovery
procedure itself is not standardized.
In a wireless or shared bus network, a multicast DIO metric
advertisement may reach several child nodes eventually everyone
responding by selecting the same parent node causing neighbor cache
to be exhausted. Thus the failure handling approaches defined in the
Reactive Approach section applies here as well. But importantly the
failure signaling will be significantly reduced because of proactive
advertisement.
3. Reservation based Neighbor Management Policy
This section defines a sample neighbor management policy, with the
primary objective to reduce NCE churn and to ensure stability of
routing adjacencies. The scheme uses a reservation based policy to
reserve NCEs for:
+-----------------------------+----------------------------+--------+
| NCE Entry for | MAX count | Reason |
+-----------------------------+----------------------------+--------+
| Routing Parent | MAX_ROUTING_PARENT_NCE_NUM | PARENT |
| | | |
| Routing child | MAX_ROUTING_CHILD_NCE_NUM | CHILD |
| | | |
| Others such as pre-auth | MAX_OTHER_NCE_NUM | OTHER |
| sessions | | |
+-----------------------------+----------------------------+--------+
Table 1: Neighbor Cache Entry reservation
Note that reservation policy depends upon identification of the
reason behind making an NCE . In case of pre-auth sessions, the
corresponding NCE is created based on the unsecured NS/NA. In case
of storing MOP, CHILD_ENT NCEs are created either based on DAO (as
shown in Figure 3) or based on secured NS/NA messaging (as shown in
Figure 4). In case of non-storing MOP, a secured NS/NA messaging as
shown in Figure 4 needs to be used.
<- - - - - - - - - - - Routing Parents - - - - - - - - - - - - ->
+---------------------------------------------------------------+
| | | |
+-----------------------------------------------------+---------+
Routing Child Routing Parents Other
Figure 5: Reservation of NCEs in neighbor table
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As shown in the figure, the neighbor cache is partitioned into
different entry types. The routing parents can possibly occupy any
entry type if found vacant since in case an eviction is sought the
non-preferred routing parent could be evicted without much impact on
the functioning or on the control traffic. The eviction could be
done based on reasons specified in Section 2.3.3.
Routing Child entries are made in context to directly connected peers
and these entries are not deleted unless they are unreacable or there
is any reason for the parent node to believe that it is no longer the
preferred parent for the child node. Deletion may happen based on
reasons mentioned in Section 2.3.2.
Other entries (OTHER) may be made in response to temporary
requirement of making an NCE. One such case is the pre
authentication phase where in the relay node makes an entry of the
PaC temporarily till the time the authentication phase is completed.
The NCE made thus is garbage collected at the end of the lifetime.
Also an implementation may choose to keep a lower lifetime for such
NCEs depending upon the time taken to complete the authentication
process.
3.1. Limitations of such a policy
The reservation based policy mentioned in this section may result in
sub-optimal path selection due to lack of NCE resource on the parent
nodes. Also the restriction of maximum pre-auth sessions in the form
of MAX_OTHER_NCE_NUM limits the maximum relay sessions that can be
supported on the relay node.
The reservation policy allows the parent node to reject the child
node's DAO or NS. But the child node cannot remember this rejection
and may reattempt the same parent after some time depending upon
triggers such as reception of DIO from the same parent who rejected
it previously. One of the only way to stop the child node from
reattempting such parent selection would be to also include a
proactive approach wherein the parent node signals its resource
availability in the DIO message as mentioned in Section 2.5.2. Such
a scheme of signalling parent node's resource availability is
currently not standardized.
RPL's storing MOP imposes additional restrictions. One such case is
where a child node may have a given parent node as its only parent
and that parent node's NCE are all used up. In such a case, the
child node would keep on retrying and failing to send a DAO through
the parent node. Ideally the parent node could have evicted a least
used child node or a child node who has an alternate parent
available. Evicting such a child node is a complex process and may
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increase the control overhead as described in Section 2.3.3.1. Thus
the reservation based policy requires that the minimum node density
is sufficiently high so that every child finds a parent node in its
vicinity with enough resources.
4. Acknowledgements
Thanks to Malisa Vucinic for pointing towards security aspects of un-
authenticated nodes neighbor cache management.
5. IANA Considerations
This memo includes no request to IANA.
6. Security Considerations
The Join Relay or the PANA Relay Element allows the un-authenticated
nodes to join the network. Since the NS/NA signaling is unencrypted,
it is possible that a malicious node may try spoof and occupy all the
entries. This draft explains the use of reservation based policy for
managing such entries. Following points try to reduce the impact of
such attacks: Only a subset of entries are reserved for un-
authenticated nodes.
a. Only a subset of entries are reserved for un-authenticated nodes
doing plain-text NS/NA
b. It is recommended that NCE timeout be configured a lower value to
evict such entries as soon as possible. New joining nodes are
supposed to use these entries and thus are only needed during the
time the authentication is in progress. Thus a short-duration
NCE timeout will help reduce the impact of DoS attacks.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
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Internet-Draft Neighbor Management Policy for 6LoWPAN February 2018
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>.
7.2. Informative References
[CONTIKI] Thingsquare, "Contiki: The Open Source OS for IoT", 2012,
<http://www.contiki-os.org>.
[Dawans_et_al]
Dawans, S., Duquennoy, S., and O. Bonaventure, "On Link
Estimation in Dense RPL Deployments", 2012.
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-13 (work
in progress), November 2017.
[I-D.ietf-6tisch-minimal-security]
Vucinic, M., Simon, J., Pister, K., and M. Richardson,
"Minimal Security Framework for 6TiSCH", draft-ietf-
6tisch-minimal-security-04 (work in progress), October
2017.
[RFC5191] Forsberg, D., Ohba, Y., Ed., Patil, B., Tschofenig, H.,
and A. Yegin, "Protocol for Carrying Authentication for
Network Access (PANA)", RFC 5191, DOI 10.17487/RFC5191,
May 2008, <https://www.rfc-editor.org/info/rfc5191>.
[RFC6345] Duffy, P., Chakrabarti, S., Cragie, R., Ohba, Y., Ed., and
A. Yegin, "Protocol for Carrying Authentication for
Network Access (PANA) Relay Element", RFC 6345,
DOI 10.17487/RFC6345, August 2011,
<https://www.rfc-editor.org/info/rfc6345>.
[Woo_et_al]
Woo, A., Tong, T., and D. Culler, "Taming the Underlying
Challenges of Reliable Multihop Routing in Sensor
Networks", 2003.
Authors' Addresses
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Rahul Arvind Jadhav (editor)
Huawei
Kundalahalli Village, Whitefield,
Bangalore, Karnataka 560037
India
Phone: +91-080-49160700
Email: rahul.ietf@gmail.com
Rabi Narayan Sahoo
Huawei
Kundalahalli Village, Whitefield,
Bangalore, Karnataka 560037
India
Phone: +91-080-49160700
Email: rabinarayans@huawei.com
Simon Duquennoy
Inria
40 Avenue Halley
Building A
Villeneuve d'Ascq
France
Phone: +33 768227731
Email: simon.duquennoy@inria.fr
Joakim Eriksson
Yanzi Networks
Email: joakime@sics.se
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