wdiff draft-ietf-roll-aodv-rpl-07.txt draft-ietf-roll-aodv-rpl-08.txt

ROLL S. Anamalamudi
Internet-Draft SRM University-AP
Intended status: Standards Track M. Zhang
Expires: October 14, 2019 November 8, 2020 Huawei Technologies
C. Perkins
Futurewei
Deep Blue Sky Networks
S.V.R.Anand
Indian Institute of Science
B. Liu
Huawei Technologies
April 12, 2019
May 7, 2020

AODV based RPL Extensions for Supporting Asymmetric AODV-P2P-RPL P2P Links in Low-Power Low-
Power and Lossy Networks (LLNs)
draft-ietf-roll-aodv-rpl-07
draft-ietf-roll-aodv-rpl-08

Abstract

Route discovery for symmetric and asymmetric Point-to-Point (P2P)
traffic flows is a desirable feature in Low power and Lossy Networks
(LLNs). For that purpose, this document specifies a reactive P2P
route discovery mechanism for both hop-by-hop routing and source
routing: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL
protocol.
protocol (AODV-RPL). Paired Instances are used to construct
directional paths, in case some of the links between source and
target node are asymmetric.

Status of This Memo

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3
3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 6 5
4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 7 6
4.1. AODV-RPL DIO RREQ Option . . . . . . . . . . . . . . . . 7 . . 6
4.2. AODV-RPL DIO RREP Option . . . . . . . . . . . . . . . . 9 . . 8
4.3. AODV-RPL DIO Target Option . . . . . . . . . . . . . . . . . 10
5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 11
6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 13
6.1. Route Request Generation . . . . . . . . . . . . . . . . 13
6.2. Receiving and Forwarding RREQ messages . . . . . . . . . 14
6.2.1. General Processing . . . . . . . . . . . . . . . . . 14
6.2.2. Additional Processing for Multiple Targets . . . . . 15
6.3. Generating Route Reply (RREP) at TargNode . . . . . . . . 16
6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 16
6.3.2. RREP-DIO for Asymmetric Route . . . . . . . . . . . . 16
6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 16 17
6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 17
7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 18 19
8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 19
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 20
9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 19 20
9.2. AODV-RPL Options: RREQ, RREP, and Target . . . . . . . . 19 20
10. Security Considerations . . . . . . . . . . . . . . . . . . . 20
11. Future Work . . . . . . . Link State Determination . . . . . . . . . . . . . . . . . . 21
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
13.1.
12.1. Normative References . . . . . . . . . . . . . . . . . . 21
13.2.
12.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Example: ETX/RSSI Values to select S bit . . . . . . 23
Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 24
B.1. Changes from version 07 to version 08 . . . . . . . . . . 24
B.2. Changes from version 06 to version 07 . . . . . . . . . . 24
B.2.
B.3. Changes from version 05 to version 06 . . . . . . . . . . 24
B.3. 25
B.4. Changes from version 04 to version 05 . . . . . . . . . . 24
B.4. 25
B.5. Changes from version 03 to version 04 . . . . . . . . . . 24
B.5. 25
B.6. Changes from version 02 to version 03 . . . . . . . . . . 25
Appendix C. Contributors . . . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 26

1. Introduction

RPL[RFC6550]

RPL [RFC6550] (Routing Protocol for LLNs (Low-Power Low-Power and Lossy
Networks)) Networks) is a
an IPv6 distance vector routing protocol designed to support multiple
traffic flows through a root-based Destination-
Oriented Destination-Oriented Directed
Acyclic Graph (DODAG). Typically, a router does not have routing
information for most other routers. Consequently, for traffic
between routers within the DODAG (i.e., Point-to-Point (P2P) traffic)
data packets either have to traverse the root in non-
storing non-storing mode, or
traverse a common ancestor in storing mode. Such P2P traffic is
thereby likely to traverse longer routes and may suffer severe
congestion near the DAG root (for more information see [RFC6997],
[RFC6998]).

To discover better paths for P2P traffic flows

The route discovery process in RPL, P2P-RPL
[RFC6997] specifies a temporary DODAG where AODV-RPL is modeled on the source acts as a
temporary root. analogous
procedure specified in AODV [RFC3561]. The source initiates DIOs encapsulating on-demand nature of AODV
route discovery is natural for the P2P
Route Discovery option (P2P-RDO) needs of peer-to-peer routing in
RPL-based LLNs. AODV terminology has been adapted for use with an address vector AODV-
RPL messages, namely RREQ for both hop-
by-hop mode (H=1) and source routing mode (H=0). Subsequently, each
intermediate router adds its IP address Route Request, and multicasts the P2P mode
DIOs, until the message reaches the Target Node, which then sends the
"Discovery Reply" object. P2P-RPL is efficient for source routing,
but much less efficient RREP for hop-by-hop routing due to the extra
address vector overhead. However, for symmetric links, when the P2P
mode DIO message is being multicast from the source hop-by-hop,
receiving nodes can infer a next hop towards the source. When the
Target Node subsequently replies to the source along the established
forward route, receiving nodes determine the next hop towards the
Target Node. For hop-by-hop routes (H=1) over symmetric links, this
would allow efficient use of routing tables for P2P-RDO messages
instead of the "Address Vector".

RPL and P2P-RPL both specify the use of a single DODAG in networks of
symmetric links, where the two directions of a link MUST both satisfy
the constraints of the objective function. This disallows the use of
asymmetric links which are qualified in one direction. But,
application-specific routing requirements as defined in IETF ROLL
Working Group [RFC5548], [RFC5673], [RFC5826] and [RFC5867] may be
satisfied by routing paths using bidirectional asymmetric links. For
this purpose, [I-D.thubert-roll-asymlink] described bidirectional
asymmetric links for RPL [RFC6550] with Paired DODAGs, for which the
DAG root (DODAGID) is common for two Instances. This can satisfy
application-specific routing requirements for bidirectional
asymmetric links in core RPL [RFC6550]. Using P2P-RPL twice with
Paired DODAGs, on the other hand, requires two roots: one for the
source and another for the target node due to temporary DODAG
formation. For networks composed of bidirectional asymmetric links
(see Section 5), AODV-RPL specifies P2P route discovery, utilizing
RPL with a new MoP. AODV-RPL makes use of two multicast messages to
discover possibly asymmetric routes. This provides higher route
diversity and can find suitable routes that might otherwise go
undetected by RPL. AODV-RPL eliminates the need for address vector
overhead in hop-by-hop mode. This significantly reduces the control
packet size, which is important for Constrained LLN networks. Both
discovered routes (upward and downward) meet the application specific
metrics and constraints that are defined in the Objective Function
for each Instance [RFC6552]. On the other hand, the point-to-point
nature of routes discovered by AODV-RPL can reduce interference near
the root nodes and also provide routes with fewer hops, likely
improving performance in the network.

The route discovery process in AODV-RPL is modeled on the analogous
procedure specified in AODV [RFC3561]. The on-demand nature of AODV
route discovery is natural for the needs of peer-to-peer routing in
RPL-based LLNs. AODV terminology has been adapted for use with AODV-
RPL messages, namely RREQ for Route Request, and RREP for Route
Reply. AODV-RPL currently omits some features compared Route
Reply. AODV-RPL currently omits some features compared to AODV -- in
particular, flagging Route Errors, blacklisting unidirectional links,
multihoming, and handling unnumbered interfaces.

AODV-RPL reuses and provides a natural extension to the core RPL
functionality to support routes with birectional asymmetric links.
It retains RPL's DODAG formation, RPL Instance and the associated
Objective Function, trickle timers, and support for storing and non-
storing modes. AODV adds basic messages RREQ and RREP as part of RPL
DIO (DODAG Information Object) control messages, and does not utilize
the DAO message of RPL. AODV-RPL specifies a new MOP running in a
seperate instance dedicating to discover P2P routes, which may differ
from the P2MP routes discoverable by native RPL. AODV-RPL can be
operated whether or not native RPL is running otherwise.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119], [RFC8174]. This document uses the following terms: BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

AODV
Ad Hoc On-demand Distance Vector Routing[RFC3561].

AODV-RPL Instance
Either the RREQ-Instance or RREP-Instance

Asymmetric Route
The route from the OrigNode to the TargNode can traverse different
nodes than the route from the TargNode to the OrigNode. An
asymmetric route may result from the asymmetry of links, such that
only one direction of the series of links fulfills satisfies the constraints
in Objective
Function during route discovery.

Bi-directional Asymmetric Link
A link that can be used in both directions but with different link
characteristics.

DIO
DODAG Information Object

DODAG RREQ-Instance (or simply RREQ-Instance)
RPL Instance built using the DIO with RREQ option; used for
control message transmission from OrigNode to TargNode, thus
enabling data transmission from TargNode to OrigNode.

DODAG RREP-Instance (or simply RREP-Instance)
RPL Instance built using the DIO with RREP option; used for
control message transmission from TargNode to OrigNode thus
enabling data transmission from OrigNode to TargNode.

Downward Direction
The direction from the OrigNode to the TargNode.

Downward Route
A route in the downward direction.

hop-by-hop routing
Routing when each node stores routing information about the next
hop.

on-demand routing
Routing in which a route is established only when needed.

OrigNode
The IPv6 router (Originating Node) initiating the AODV-RPL route
discovery to obtain a route to TargNode.

Paired DODAGs
Two DODAGs for a single route discovery process between OrigNode
and TargNode.

P2P
Point-to-Point -- in other words, not constrained a priori to
traverse a common ancestor.

reactive routing
Same as "on-demand" routing.

RREQ-DIO message
An AODV-RPL MoP MOP DIO message containing the RREQ option. The
RPLInstanceID in RREQ-DIO is assigned locally by the OrigNode.

RREP-DIO message
An AODV-RPL MoP MOP DIO message containing the RREP option. The
RPLInstanceID in RREP-DIO is typically paired to the one in the
associated RREQ-DIO message.

Source routing
A mechanism by which the source supplies the complete route
towards the target node along with each data packet [RFC6550].

Symmetric route
The upstream and downstream routes traverse the same routers.

TargNode
The IPv6 router (Target Node) for which OrigNode requires a route
and initiates Route Discovery within the LLN network.

Upward Direction
The direction from the TargNode to the OrigNode.

Upward Route
A route in the upward direction.

ART option
AODV-RPL Target option: a target option defined in this document.

3. Overview of AODV-RPL

With AODV-RPL, routes from OrigNode to TargNode within the LLN
network are established "on-demand". In other words, the route
discovery mechanism in AODV-RPL is invoked reactively when OrigNode
has data for delivery to the TargNode but existing routes do not
satisfy the application's requirements. AODV-RPL is thus functional
without requiring the use of RPL or any other routing protocol.

The routes discovered by AODV-RPL are not constrained to traverse a
common ancestor. Unlike
RPL [RFC6550] and P2P-RPL [RFC6997], AODV-RPL can enable asymmetric communication paths
in networks with bidirectional asymmetric links. For this purpose,
AODV-RPL enables discovery of two routes: namely, one from OrigNode
to TargNode, and another from TargNode to OrigNode. When possible,
AODV-RPL also enables symmetric route discovery along Paired DODAGs
(see Section 5).

In AODV-RPL, routes are discovered by first forming a temporary DAG
rooted at the OrigNode. Paired DODAGs (Instances) are constructed
according to the AODV-RPL Mode of Operation (MoP) (MOP) during route
formation between the OrigNode and TargNode. The RREQ-Instance is
formed by route control messages from OrigNode to TargNode whereas
the RREP-Instance is formed by route control messages from TargNode
to OrigNode. Intermediate routers join the Paired DODAGs based on
the rank Rank as calculated from the DIO message. Henceforth in this
document, the RREQ-DIO message means the AODV-RPL mode DIO message
from OrigNode to TargNode, containing the RREQ option (see
Section 4.1). Similarly, the RREP-DIO message means the AODV-RPL
mode DIO message from TargNode to OrigNode, containing the RREP
option (see Section 4.2). The route discovered in the RREQ-Instance
is used for transmitting data from TargNode to OrigNode, and the
route discovered in RREP-Instance is used for transmitting data from
OrigNode to TargNode.

4. AODV-RPL DIO Options

4.1. AODV-RPL DIO RREQ Option

OrigNode sets its IPv6 address in the DODAGID field of the RREQ-DIO
message. A RREQ-DIO message MUST carry exactly one RREQ option. option,
otherwise it SHOULD be dropped.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |S|H|X| Compr | L | MaxRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Orig SeqNo | |
+-+-+-+-+-+-+-+-+ |
| |
| |
| Address Vector (Optional, Variable Length) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: DIO RREQ option format Format for AODV-RPL MoP RREQ Option

OrigNode supplies the following information in the RREQ option:

Option Type
The type assigned to the RREQ option (see Section 9.2).
TBD2

Option Length
The length of the option in octets, excluding the Type and Length
fields. Variable due to the presence of the address vector and
the number of octets elided according to the Compr value.

S
Symmetric bit indicating a symmetric route from the OrigNode to
the router transmitting this RREQ-DIO.

H
Set to one for a hop-by-hop route. Set to zero for a source
route. This flag controls both the downstream route and upstream
route.

X
Reserved.

Compr
4-bit unsigned integer. Number of prefix octets that are elided
from the Address Vector. The octets elided are shared with the
IPv6 address in the DODAGID. This field is only used in source
routing mode (H=0). In hop-by-hop mode (H=1), this field MUST be
set to zero and ignored upon reception.

L
2-bit unsigned integer determining the duration that a node is
able to belong to the temporary DAG in RREQ-Instance, including
the OrigNode and the TargNode. Once the time is reached, a node
MUST leave the DAG and stop sending or receiving any more DIOs for
the temporary DODAG. The definition for the "L" bit is similar to
that found in [RFC6997], except that the values are adjusted to
enable arbitrarily long route lifetime.

* 0x00: No time limit imposed.
* 0x01: 16 seconds
* 0x02: 64 seconds
* 0x03: 256 seconds

L is independent from the route lifetime, which is defined in the
DODAG configuration option. The route entries in hop-by-hop
routing and states of source routing can still be maintained even
after the node no longer maintains DAG expires. connectivity or messaging.

MaxRank
This field indicates the upper limit on the integer portion of the
rank
Rank (calculated using the DAGRank() macro defined in [RFC6550]).
A value of 0 in this field indicates the limit is infinity.

Orig SeqNo
Sequence Number of OrigNode, defined similarly as in AODV
[RFC3561]. OrigNode. See Section 6.1.

Address Vector
A vector of IPv6 addresses representing the route that the RREQ-
DIO has passed. It is only present when the 'H' H bit is set to 0.
The prefix of each address is elided according to the Compr field.

A node

TargNode can join the RREQ instance at a Rank whose integer portion
is equal to the MaxRank. Other nodes MUST NOT join a RREQ instance
if its own rank Rank would be equal to or higher than MaxRank. Targnode can join the RREQ instance at a
rank whose integer portion is equal to the MaxRank. A router
MUST discard a received RREQ if the integer part of the advertised rank
Rank equals or exceeds the MaxRank limit. This definition of MaxRank is
the same as that found in [RFC6997].

4.2. AODV-RPL DIO RREP Option

TargNode sets its IPv6 address in the DODAGID field of the RREP-DIO
message. A RREP-DIO message MUST carry exactly one RREP option. option,
otherwise the message SHOULD be dropped. TargNode supplies the
following information in the RREP option:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |G|H|X| Compr | L | MaxRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shift |Rsv| |
+-+-+-+-+-+-+-+-+ |
| |
| |
| Address Vector (Optional, Variable Length) |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: DIO RREP option format Format for AODV-RPL MoP

Type
The type assigned to the RREP option (see Section 9.2)

Option Type
TBD3

G
Gratuitous route (see Section 7).

H
Requests either source routing (H=0) or hop-by-hop (H=1) for the
downstream route. It MUST be set to be the same as the 'H' H bit in
RREQ option.

X
Reserved.

Compr
4-bit unsigned integer. Same definition as in RREQ option.

L
2-bit unsigned integer defined as in RREQ option.

MaxRank
Similarly to MaxRank in the RREQ message, this field indicates the
upper limit on the integer portion of the rank. Rank. A value of 0 in
this field indicates the limit is infinity.

Shift
6-bit unsigned integer. This field is used to recover the
original InstanceID RPLInstanceID (see Section 6.3.3); 0 indicates that the
original InstanceID RPLInstanceID is used.

Rsv
MUST be initialized to zero and ignored upon reception.

Address Vector
Only present when the 'H' H bit is set to 0. For an asymmetric route,
the Address Vector represents the IPv6 addresses of the route that
the RREP-DIO has passed. For a symmetric route, it is the Address
Vector when the RREQ-DIO arrives at the TargNode, unchanged during
the transmission to the OrigNode.

4.3. AODV-RPL DIO Target Option

The AODV-RPL Target (ART) Option is based on the Target Option in
core RPL [RFC6550]. The Flags field is replaced by the Destination
Sequence Number of the TargNode and the Prefix Length field is
reduced to 7 bits so that the value is limited to be no greater than
127.

A RREQ-DIO message MUST carry at least one ART Option. A RREP-DIO
message MUST carry exactly one ART Option. Otherwise, the message
SHOULD be dropped.

OrigNode can include multiple TargNode addresses via multiple AODV-
RPL Target Options in the RREQ-DIO, for routes that share the same
constraints.
requirement on metrics. This reduces the cost to building only one
DODAG.
Furthermore, a single Target Option can be used for different
TargNode addresses if they share the same prefix; in that case the
use of the destination sequence number is not defined in this
document.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Dest SeqNo |r|Prefix Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ |
| Target Prefix / Address (Variable Length) |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: Target option format for AODV-RPL MoP

Type
The type assigned to the ART MOP

Option Type
TBD4

Option Length
Length of the option in octets excluding the Type and Length
fields

Dest SeqNo

In RREQ-DIO, if nonzero, it is the last known Sequence Number for
TargNode for which a route is desired. In RREP-DIO, it is the
destination sequence number associated to the route.

r
A one-bit reserved field. This field MUST be initialized to zero
by the sender and MUST be ignored by the receiver.

Prefix Length
7-bit unsigned integer. Number of valid leading bits in the IPv6
Prefix. If Prefix Length is 0, then the value in the Target
Prefix / Address field represents an IPv6 address, not a prefix.

Target Prefix / Address
(variable-length field) An IPv6 destination address or prefix.
The Prefix Length field contains the number of valid leading bits
in the prefix. The length of the field is the least number of
octets that can contain all of the bits of the Prefix, in other
words Floor((7+(Prefix Length))/8) octets. The remaining bits in
the Target Prefix / Address field after the prefix length (if any)
MUST be set to zero on transmission and MUST be ignored on
receipt.

5. Symmetric and Asymmetric Routes

In Figure 4 and Figure 5, BR is the Border Router, O is the OrigNode,
R is an intermediate router, and T is the TargNode. If the RREQ-DIO
arrives over an interface that is known to be symmetric, and the 'S' S
bit is set to 1, then it remains as 1, as illustrated in Figure 4.
If an intermediate router sends out RREQ-DIO with the 'S' S bit set to 1,
then all the one-hop links on the route from the OrigNode O to this
router meet the requirements of route discovery, and the route can be
used symmetrically.

BR
/----+----\
/ | \
/ | \
R R R
_/ \ | / \
/ \ | / \
/ \ | / \
R -------- R --- R ----- R -------- R
/ \ <--S=1--> / \ <--S=1--> / \
<--S=1--> \ / \ / <--S=1-->
/ \ / \ / \
O ---------- R ------ R------ R ----- R ----------- T
/ \ / \ / \ / \
/ \ / \ / \ / \
/ \ / \ / \ / \
R ----- R ----------- R ----- R ----- R ----- R ---- R----- R

>---- RREQ-Instance (Control: O-->T; Data: T-->O) ------->
<---- RREP-Instance (Control: T-->O; Data: O-->T) -------<

Figure 4: AODV-RPL with Symmetric Paired Instances

Upon receiving a RREQ-DIO with the 'S' S bit set to 1, a node determines
whether this one-hop link can be used symmetrically, i.e., both the
two directions meet the requirements of data transmission. If the
RREQ-DIO arrives over an interface that is not known to be symmetric,
or is known to be asymmetric, the 'S' S bit is set to 0. If the 'S' S bit
arrives already set to be '0', it is set to be '0' on retransmission
(Figure 5). Therefore, for For an asymmetric route, there is at least one hop which
doesn't fulfill the constraints in satisfy the two
directions. Objective Function. Based on the 'S' S bit received
in RREQ-DIO, the TargNode T determines whether or not the route is
symmetric before transmitting the RREP-DIO message upstream towards
the OrigNode O.

The criteria used to determine whether or not each link is symmetric
is beyond the scope of the document, and may be implementation-
specific. For instance, intermediate routers MAY can use local
information (e.g., bit rate, bandwidth, number of cells used in
6tisch), a priori knowledge (e.g. link quality according to previous
communication) or use averaging techniques as appropriate to the
application.

Appendix A describes an example method using the ETX and RSSI to
estimate whether the link is symmetric in terms of link quality is
given in using an averaging technique.

BR
/----+----\
/ | \
/ | \
R R R
/ \ | / \
/ \ | / \
/ \ | / \
R --------- R --- R ---- R --------- R
/ \ --S=1--> / \ --S=0--> / \
--S=1--> \ / \ / --S=0-->
/ \ / \ / \
O ---------- R ------ R------ R ----- R ----------- T
/ \ / \ / \ / \
/ <--S=0-- / \ / \ / <--S=0--
/ \ / \ / \ / \
R ----- R ----------- R ----- R ----- R ----- R ---- R----- R
<--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0--

>---- RREQ-Instance (Control: O-->T; Data: T-->O) ------->
<---- RREP-Instance (Control: T-->O; Data: O-->T) -------<

Figure 5: AODV-RPL with Asymmetric Paired Instances

6. AODV-RPL Operation

6.1. Route Request Generation

The route discovery process is initiated when an application at the
OrigNode has data to be transmitted to the TargNode, but does not
have a route that satisfies the Objective Function for the target that fulfills the requirements of
the data transmission. In this case, the OrigNode builds a local
RPLInstance and a DODAG rooted at itself. Then it transmits a DIO
message containing exactly one RREQ option (see Section 4.1) via
link-local multicast. The DIO MUST contain at least one ART Option
(see Section 4.3). The 'S' S bit in RREQ-DIO sent out by the OrigNode is
set to 1.

Each node maintains a sequence number, which rolls over like a
lollipop counter [Perlman83]; refer to number; the operation is specified in
section 7.2 of [RFC6550] for
detailed operation. [RFC6550]. When the OrigNode initiates a route
discovery process, it MUST increase its own sequence number to avoid
conflicts with previously established routes. The sequence number is
carried in the OrigSeqNo Orig SeqNo field of the RREQ option.

The address in the ART Option can be a unicast IPv6 address or a
prefix. The OrigNode can initiate the route discovery process for
multiple targets simultaneously by including multiple ART Options,
and within a RREQ-DIO the requirements for the routes to different
TargNodes MUST be the same.

OrigNode can maintain different RPLInstances to discover routes with
different requirements to the same targets. Using the InstanceID
pairing mechanism (see Section 6.3.3), route replies (RREP-DIOs) for
different RPLInstances can be distinguished.

The transmission of RREQ-DIO obeys the Trickle timer. timer [RFC6206]. If
the duration specified by the "L" L bit has elapsed, the OrigNode MUST
leave the DODAG and stop sending RREQ-DIOs in the related
RPLInstance.

6.2. Receiving and Forwarding RREQ messages

6.2.1. General Processing

Upon receiving a RREQ-DIO, a router which goes through the steps below. If
the router does not belong to the
RREQ-instance goes through RREQ-Instance, then the following steps: maximum
useful rank (MaxUseRank) is MaxRank. Otherwise, MaxUseRank is set to
be the Rank value that was stored when the router processed the best
previous RREQ for the DODAG with the given RREQ-Instance.

Step 1:

If the 'S' S bit in the received RREQ-DIO is set to 1, the router MUST check the two directions
determine whether each direction of the link by (by which the RREQ-DIO RREQ-
DIO is
received. received) satisfies the Objective Function. In case that
the downward (i.e. towards the TargNode) direction of the link can't fulfill
does not satisfy the requirements, Objective Function, the link can't be used
symmetrically, thus the 'S' S bit of the RREQ-DIO to be sent out MUST
be set as 0. If the 'S' S bit in the received RREQ-DIO is set to 0,
the router MUST only checks check into the upward direction (towards the
OrigNode) of the link.

If the upward direction of the link can fulfill satisfy the requirements
indicated Objective
Function (defined in the constraint option, [RFC6551]), and the router's rank Rank would not
exceed the MaxRank MaxUseRank limit, the router joins the DODAG of the
RREQ-Instance. The router that transmitted the received RREQ-DIO
is selected as the preferred parent. Later, other RREQ-DIO
messages might be received. How to maintain the parent set,
select the preferred parent, and update the router's rank obeys
the core RPL and of the OFs defined in ROLL WG. In case
RREQ-Instance. The router that transmitted the received RREQ-DIO
is selected as the preferred parent. Otherwise, if the
constraint Objective
Function is not satisfied or the MaxRank MaxUseRank limit is not fulfilled, exceeded, the
router MUST discard the received RREQ-DIO and MUST NOT join the
DODAG.

Step 2:

Then the router checks if one of its addresses is included in one
of the ART Options. If so, this router is one of the TargNodes.
Otherwise, it is an intermediate router.

Step 3:

If the 'H' H bit is set to 1, then the router (TargNode or
intermediate) MUST build the an upward route entry accordingly. The
route entry towards OrigNode
which MUST include at least the following items: Source Address,
InstanceID, Destination Address, Next Hop, Lifetime, and Sequence
Number. The Destination Address and the InstanceID respectively
can be respectively learned from the DODAGID and the RPLInstanceID of the RREQ-DIO, RREQ-
DIO, and the Source Address is copied from the ART
Option. address used by the local
router to send data to the OrigNode. The next hop Next Hop is the
preferred parent. The lifetime is set according to DODAG
configuration (i.e., not the L bit) and can be extended when the
route is actually used. The sequence number represents the
freshness of the route entry, and it is copied from the Orig SeqNo
field of the RREQ option. A route entry with the same source and
destination address, same InstanceID, but stale sequence number,
SHOULD
MUST be deleted.

Step 4:

If the 'H' router is an intermediate router, then it transmits a RREQ-
DIO via link-local multicast; if the H bit is set to 0, an the
intermediate router MUST include the address of the interface
receiving the RREQ-DIO into the address vector.

Step 4:

An intermediate vector.. Otherwise, if
the router transmits a RREQ-DIO via link-local
multicast. TargNode (i.e., TargNode) was not already associated with the
RREQ-Instance, it prepares a RREP-DIO Section 6.3. If, on the
other hand TargNode was already associated with the RREQ-Instance,
it takes no further action and does not send an RREP-DIO.

6.2.2. Additional Processing for Multiple Targets

If the OrigNode tries to reach multiple TargNodes in a single RREQ-
instance,
Instance, one of the TargNodes can be an intermediate router to the
others, therefore it SHOULD MUST continue sending RREQ-DIO to reach other
targets. In this case, before rebroadcasting the RREQ-DIO, a
TargNode MUST delete the Target Option encapsulating its own address,
so that downstream routers with higher ranks Rank values do not try to
create a route to this TargetNode.

An intermediate router could receive several RREQ-DIOs from routers
with lower ranks Rank values in the same RREQ-instance RREQ-Instance but have different
lists of Target Options. When rebroadcasting the RREQ-DIO, the
intersection of these lists SHOULD MUST be included. For example, suppose
two RREQ-DIOs are received with the same RPLInstance and OrigNode.

Suppose further that the first RREQ has (T1, T2) as the targets, and
the second one has (T2, T4) as targets. Then only T2 needs to be
included in the generated RREQ-DIO. If the intersection is empty, it
means that all the targets have been reached, and the router SHOULD MUST NOT
send out any RREQ-DIO. For the purposes of determining the
intersection with previous incoming RREQ-DIOs, the intermediate
router maintains a record of the targets that have been requested
associated with the RREQ-Instance. Any RREQ-DIO message with
different ART Options coming from a router with higher rank Rank is
ignored.

6.3. Generating Route Reply (RREP) at TargNode

6.3.1. RREP-DIO for Symmetric route

If a RREQ-DIO arrives at TargNode with the 'S' S bit set to 1, there is a
symmetric route along which both directions can fulfill satisfy the
requirements. Objective
Function. Other RREQ-DIOs might later provide asymmetric upward
routes (i.e. S=0). Selection between a qualified symmetric route
and an asymmetric route that might have better performance is
implementation-specific and out of scope. If the implementation uses
selects the symmetric route, and the L bit is not 0, the TargNode MAY
delay transmitting the RREP-DIO for duration RREP_WAIT_TIME to await
a better symmetric route. route with a lower Rank. The value of RREP_WAIT_TIME is
set by default to 1/4 of the time duration determined by the L bit.

For a symmetric route, the RREP-DIO message is unicast to the next
hop according to the accumulated address vector (H=0) or the route
entry (H=1). Thus the DODAG in RREP-Instance does not need to be
built. The RPLInstanceID in the RREP-Instance is paired as defined
in Section 6.3.3. In case the 'H' H bit is set to 0, the address vector
received in the RREQ-DIO MUST be included in the RREP-DIO. TargNode
increments its current sequence number and uses the incremented
result in the Dest SeqNo in the ART option of the RREQ-
DIO. RREQ-DIO. The
address of the OrigNode MUST be encapsulated in the ART Option and
included in this RREP-DIO message.

6.3.2. RREP-DIO for Asymmetric Route

When a RREQ-DIO arrives at a TargNode with the 'S' S bit set to 0, the
TargNode MUST build a DODAG in the RREP-Instance rooted at itself in
order to discover the downstream route from the OrigNode to the
TargNode. The RREP-DIO message MUST be re-transmitted via link-local
multicast until the OrigNode is reached or MaxRank is exceeded. The
TargNode MAY delay transmitting the RREP-DIO for duration
RREP_WAIT_TIME to await a route with a lower Rank. The value of
RREP_WAIT_TIME is set by default to 1/4 of the time duration
determined by the L bit.

The settings of the fields in RREP option and ART option are the same
as for the symmetric route, except for the 'S' S bit.

6.3.3. RPLInstanceID Pairing

Since the RPLInstanceID is assigned locally (i.e., there is no
coordination between routers in the assignment of RPLInstanceID), the
tuple (OrigNode, TargNode, RPLInstanceID) is needed to uniquely
identify a discovered route. The upper layer applications may have
different requirements and they can initiate the It is possible that multiple route
discoveries with dissimilar Objective Functions are initiated
simultaneously. Thus between the same pair of OrigNode and TargNode,
there can be multiple AODV-RPL route discovery instances. To avoid
any mismatch, the RREQ-Instance and the RREP-Instance in the same
route discovery MUST be paired somehow, e.g. using the RPLInstanceID.

When preparing the RREP-DIO, a TargNode could find the RPLInstanceID
to be used for the RREP-Instance is already occupied by another RPL
Instance from an earlier route discovery operation which is still
active. In other words, it might happen that two distinct OrigNodes
need routes to the same TargNode, and they happen to use the same
RPLInstanceID for RREQ-Instance. In this case, the occupied
RPLInstanceID MUST NOT be used again. Then the second RPLInstanceID
MUST be shifted into another integer so that the two RREP-instances
can be distinguished. In RREP option, the Shift field indicates the
shift to be applied to original RPLInstanceID. When the new
InstanceID after shifting exceeds 63, it rolls over starting at 0.
For example, the original InstanceID is 60, and shifted by 6, the new
InstanceID will be 2. Related operations can be found in
Section 6.4.

6.4. Receiving and Forwarding Route Reply

Upon receiving a RREP-DIO, a router which does not belong to the
RREQ-instance
RREQ-Instance goes through the following steps:

Step 1:

If the 'S' S bit is set to 1, the router proceeds MUST proceed to step 2.

If the 'S' S bit of the RREP-DIO is set to 0, the router MUST check
the downward direction of the link (towards the TargNode) over
which the RREP-DIO is received. If the downward direction of the
link can fulfill the requirements indicated in satisfy the constraint
option, Objective Function, and the router's rank Rank
would not exceed the MaxRank limit, the router joins the DODAG of
the RREP-Instance. The router that transmitted the received RREP-DIO RREP-
DIO is selected as the preferred parent. Afterwards, other RREP-DIO RREP-
DIO messages can be received. How
to maintain the parent set, select the preferred parent, and
update the router's rank obeys the core RPL and the OFs defined in
ROLL WG.

If the constraints are Objective Function is not fulfilled, satisfied, the router MUST NOT
join the DODAG; the router MUST discard the RREQ-DIO, and does not
execute the remaining steps in this section.

Step 2:

The router next checks if one of its addresses is included in the
ART Option. If so, this router is the OrigNode of the route
discovery. Otherwise, it is an intermediate router.

Step 3:

If the 'H' H bit is set to 1, then the router (OrigNode or
intermediate) MUST build a downward route entry. The route entry
SHOULD
MUST include at least the following items: OrigNode Address,
InstanceID, TargNode Address as destination, Next Hop, Lifetime
and Sequence Number. For a symmetric route, the next hop Next Hop in the
route entry is the router from which the RREP-DIO is received.
For an asymmetric route, the next hop Next Hop is the preferred parent in
the DODAG of RREQ-Instance. The InstanceID in the route entry
MUST be the original RPLInstanceID (after subtracting the Shift
field value). The source address is learned from the ART Option,
and the destination address is learned from the DODAGID. The
lifetime is set according to DODAG configuration and can be
extended when the route is actually used. The sequence number
represents the freshness of the route entry, and is copied from
the Dest SeqNo field of the ART option of the RREP-DIO. A route
entry with same source and destination address, same InstanceID,
but stale sequence number, SHOULD be deleted.

If the 'H' H bit is set to 0, for an asymmetric route, an intermediate
router MUST include the address of the interface receiving the
RREP-DIO into the address vector; for a symmetric route, there is
nothing to do in this step.

Step 4:

If the receiver is the OrigNode, it can start transmitting the
application data to TargNode along the path as provided in RREP-
Instance, and processing for the RREP-DIO is complete. Otherwise,
in case of an asymmetric route, the intermediate router transmits
the RREP-DIO via link-local multicast. In case of a symmetric
route, the RREP-DIO message is unicast to the next hop Next Hop according
to the address vector in the RREP-DIO (H=0) or the local route
entry (H=1). The RPLInstanceID in the transmitted RREP-DIO is the
same as the value in the received RREP-DIO. The local knowledge
for the TargNode's sequence number SHOULD be updated.

Upon receiving a RREP-DIO, a router which already belongs to the
RREQ-Instance SHOULD drop the RREP-DIO.

7. Gratuitous RREP

In some cases, an Intermediate router that receives a RREQ-DIO
message MAY transmit a "Gratuitous" RREP-DIO message back to OrigNode
instead of continuing to multicast the RREQ-DIO towards TargNode.
The intermediate router effectively builds the RREP-Instance on
behalf of the actual TargNode. The 'G' G bit of the RREP option is
provided to distinguish the Gratuitous RREP-DIO (G=1) sent by the
Intermediate node from the RREP-DIO sent by TargNode (G=0).

The gratuitous RREP-DIO can be sent out when an intermediate router R
receives a RREQ-DIO for a TargNode T, TargNode, and R happens to have the router has a more recent
(larger destination sequence number) pair of downward and upward
routes to T the TargNode which also fulfill satisfy the requirements. Objective Function.

In case of source routing, the intermediate router R MUST unicast the
received RREQ-DIO to TargNode T including the address vector between
the OrigNode O and the router R. router. Thus T the TargNode can have a complete
upward route address vector from itself to O. the OrigNode. Then R the
router MUST send out the gratuitous RREP-DIO including the address
vector from R the router itself to T. the TargNode.

In case of hop-by-hop routing, R the intermediate router MUST unicast
the received RREQ-DIO
hop-by-hop to T. the Next Hop on the route. The routers Next Hop
router along the route SHOULD MUST build new route entries with the related
RPLInstanceID and DODAGID in the downward direction. The above
process will happen recursively until the RREQ-DIO arrives at the
TargNode. Then T the TargNode MUST unicast recursively the RREP-DIO
hop-by-hop to R, the intermediate router, and the routers along the
route SHOULD build new route entries in the upward direction. Upon
receiving the unicast RREP-DIO, R the intermediate router sends the
gratuitous RREP-DIO to the OrigNode as defined in Section 6.3.

8. Operation of Trickle Timer

The trickle timer operation to control RREQ-Instance/RREP-Instance
multicast is similar uses [RFC6206] to that control RREQ-DIO and RREP-DIO
transmissions. The Trickle control of these DIO transmissions follow
the procedures described in P2P-RPL [RFC6997]. the Section 8.3 of [RFC6550] entitled
"DIO Transmission".

9. IANA Considerations

9.1. New Mode of Operation: AODV-RPL

IANA is required asked to assign a new Mode of Operation, named "AODV-RPL" for
Point-to-Point(P2P) hop-by-hop routing under the RPL registry.
The value of TBD1 is assigned from the "Mode of Operation" space
Registry [RFC6550].

+-------------+---------------+---------------+
| Value | Description | Reference |
+-------------+---------------+---------------+
| TBD1 (5) | AODV-RPL | This document |
+-------------+---------------+---------------+

Figure 6: Mode of Operation

9.2. AODV-RPL Options: RREQ, RREP, and Target

Three entries are required for

IANA is asked to assign three new AODV-RPL options "RREQ", "RREP" and "ART" with values of TBD2 (0x0A), TBD3 (0x0B) and TBD4 (0x0C)
"ART", as described in Figure 7 from the "RPL Control Message
Options" space Registry [RFC6550].

Figure 7: AODV-RPL Options

10. Security Considerations

The

In general, the security mechanisms defined in section 10 of [RFC6550] and
section 11 considerations for the operation of [RFC6997] can also be applied AODV-RPL
are similar to those for the control messages
defined operation of RPL (as described in this specification. The RREQ-DIO
Section 19 of the RPL specification [RFC6550]). Sections 6.1 and RREP-DIO both have a
secure variant, 10
of [RFC6550] describe RPL's security framework, which provide integrity and provides data
confidentiality, authentication, replay protection as well
as optional confidentiality protection, and delay protection.
protection services.

A router can join a temporary DAG created for a secure AODV-RPL route
discovery only if it can operate in support the three security modes defined Security Configuration in
[RFC6550]. AODV-RPL messages SHOULD use a security mode at least as
strong as use,
which also specifies the security mode used in RPL.

o Unsecured. In this mode, RREQ-DIO and RREP-DIO are used without
any security fields as defined key in section 6.1 of [RFC6550]. The
control messages can be protected by other security mechanisms,
e.g. link-layer security. This mode SHOULD NOT be used when RPL use. It does not matter whether the
key is using Preinstalled mode preinstalled or Authenticated mode (see below).

o Preinstalled. In this mode, AODV-RPL uses secure RREQ-DIO and
RREP-DIO messages, and a node wishing to join a secured network
will dynamically acquired. The router must have been pre-configured with a shared key. A node can use
that
the key to in use before it can join the AODV-RPL DODAG as DAG being created for a host or secure
P2P-RPL route discovery.

If a router.
Unsecured messages MUST be dropped. This mode SHOULD NOT be used
when RPL is using Authenticated mode.

o Authenticated. In this mode, besides rogue router knows the preinstalled shared key,
a node MUST obtain a second key from a key authority. The
interaction between a node and for the key authority is out Security Configuration in
use, it can join the secure AODV-RPL route discovery and cause
various types of scope
for this specification. Authenticated mode may be useful, for
instance, to protect against damage. Such a malicious rogue router advertising could advertise false
information in RREQ-DIO or RREP-DIO its DIOs in order to include itself in the discovered route. This
route(s). It could generate bogus RREQ-DIO, and RREP-DIO messages
carrying bad routes or maliciously modify genuine RREP-DIO messages
it receives. A rogue router acting as the OrigNode could launch
denial-of-service attacks against the LLN deployment by initiating
fake AODV-RPL route discoveries. In this type of scenario, RPL's
authenticated mode would also prevent of operation, where a malicious router
from initiating node can obtain the key to
use for a P2P-RPL route discovery operations or launching denial-of-
service attacks only after proper authentication,
SHOULD be used.

When RREQ-DIO message uses source routing option with 'H' set to impair the performance 0,
some of the LLN. AODV-RPL
can use security concerns that led to the keys established with deprecation of Type 0
routing headers [RFC5095] may apply. To avoid the Authenticated mode RPL
instance. Once a router or possibility of a host has been authenticated
RREP-DIO message traveling in a routing loop, if one of its addresses
are present as part of the
RPL instance, it can join the AODV-RPL instance without any
further authentication. The authentication in AODV-RPL can also
be independent to RPL if, before joining Source Route listed inside the AODV-RPL instance, message,
the node obtains another key from Intermediate Router MUST NOT forward the key authority. message.

11. Future Work

There has been some discussion about how to determine the initial
state of a link after an AODV-RPL-based network has begun operation.
The current draft operates as if the Link State Determination

This document specifies that links are considered symmetric until
additional metric information is collected. The means for making Other link metric information is considered out of scope for AODV-RPL. In
the future, RREQ and RREP messages could
can be equipped with new fields acquired before AODV-RPL operation, by executing evaluation
procedures; for use in verifying link metrics. In particular, it is possible to
identify unidirectional links; an RREQ received across a
unidirectional link has to instance test traffic can be dropped, since the destination node
cannot make use generated between nodes
of the received DODAG to route packets back to the
source node that originated the route discovery operation. This is
roughly the same as considering a unidirectional link to present an
infinite cost metric that automatically disqualifies it deployed network. During AODV-RPL operation, OAM techniques
for use in
the reverse direction.

12. Contributors

Abdur Rashid Sangi
Huaiyin Institute of Technology
No.89 North Beijing Road, Qinghe District
Huaian 223001
P.R. China
Email: sangi_bahrian@yahoo.com

13. evaluating link state (see([RFC7548], [RFC7276], [co-ioam]) MAY
be used (at regular intervals appropriate for the LLN). The
evaluation procedures are out of scope for AODV-RPL.

12. References

13.1.

12.1. 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>.

[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
Demand Distance Vector (AODV) Routing", RFC 3561,
DOI 10.17487/RFC3561, July 2003,
<https://www.rfc-editor.org/info/rfc3561>.

[RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
of Type 0 Routing Headers in IPv6", RFC 5095,
DOI 10.17487/RFC5095, December 2007,
<https://www.rfc-editor.org/info/rfc5095>.

[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
March 2011, <https://www.rfc-editor.org/info/rfc6206>.

[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>.

[RFC6552] Thubert, P.,

[RFC6551] Vasseur, JP., Ed., "Objective Function Zero for the Routing
Protocol Kim, M., Ed., Pister, K., Dejean, N.,
and D. Barthel, "Routing Metrics Used for Path Calculation
in Low-Power and Lossy Networks (RPL)", Networks", RFC 6552, 6551,
DOI 10.17487/RFC6552, 10.17487/RFC6551, March 2012,
<https://www.rfc-editor.org/info/rfc6552>.
<https://www.rfc-editor.org/info/rfc6551>.

[RFC6998] Goyal, M., Ed., Baccelli, E., Brandt, A., and J. Martocci,
"A Mechanism to Measure the Routing Metrics along a Point-
to-Point Route in a Low-Power and Lossy Network",
RFC 6998, DOI 10.17487/RFC6998, August 2013,
<https://www.rfc-editor.org/info/rfc6998>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

13.2.

12.2. Informative References

[I-D.thubert-roll-asymlink]
Thubert, P., "RPL adaptation for asymmetrical links",
draft-thubert-roll-asymlink-02 (work in progress),
December 2011.

[Perlman83]
Perlman, R., "Fault-Tolerant Broadcast of Routing
Information", December 1983.

[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
Demand Distance Vector (AODV) Routing", RFC 3561,
DOI 10.17487/RFC3561, July 2003,
<https://www.rfc-editor.org/info/rfc3561>.

[RFC5548] Dohler, M., Ed., Watteyne, T., Ed., Winter, T., Ed., and
D. Barthel, Ed., "Routing Requirements

[co-ioam] Ballamajalu, Rashmi., S.V.R., Anand., and Malati. Hegde,
"Co-iOAM: In-situ Telemetry Metadata Transport for Urban Low-Power
and Lossy Networks", RFC 5548, DOI 10.17487/RFC5548, May
2009, <https://www.rfc-editor.org/info/rfc5548>.

[RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T.
Phinney, "Industrial Routing Requirements in Low-Power and
Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October
2009, <https://www.rfc-editor.org/info/rfc5673>.

[RFC5826] Brandt, A., Buron, J., and G. Porcu, "Home Automation
Routing Requirements in Low-Power and Lossy Networks",
RFC 5826, DOI 10.17487/RFC5826, April 2010,
<https://www.rfc-editor.org/info/rfc5826>.

[RFC5867] Martocci, J., Ed., De Mil, P., Riou, N., and W. Vermeylen,
"Building Automation Routing Requirements in Low-Power and
Lossy Networks", RFC 5867, DOI 10.17487/RFC5867, June
2010, <https://www.rfc-editor.org/info/rfc5867>.
Resource Constrained Networks within IETF Standards
Framework", 2018 10th International Conference on
Communication Systems & Networks (COMSNETS) pp.573-576,
Jan 2018.

[RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and
J. Martocci, "Reactive Discovery of Point-to-Point Routes
in Low-Power and Lossy Networks", RFC 6997,
DOI 10.17487/RFC6997, August 2013,
<https://www.rfc-editor.org/info/rfc6997>.

[RFC6998] Goyal, M., Ed., Baccelli, E., Brandt, A., and J. Martocci,
"A Mechanism to Measure the Routing Metrics along a Point-
to-Point Route in a Low-Power and Lossy Network",
RFC 6998, 6997,
DOI 10.17487/RFC6998, 10.17487/RFC6997, August 2013,
<https://www.rfc-editor.org/info/rfc6998>.
<https://www.rfc-editor.org/info/rfc6997>.

[RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
Weingarten, "An Overview of Operations, Administration,
and Maintenance (OAM) Tools", RFC 7276,
DOI 10.17487/RFC7276, June 2014,
<https://www.rfc-editor.org/info/rfc7276>.

[RFC7548] Ersue, M., Ed., Romascanu, D., Schoenwaelder, J., and A.
Sehgal, "Management of Networks with Constrained Devices:
Use Cases", RFC 7548, DOI 10.17487/RFC7548, May 2015,
<https://www.rfc-editor.org/info/rfc7548>.

Appendix A. Example: ETX/RSSI Values to select S bit

We have tested the

The combination of "RSSI(downstream)" Received Signal Strength Indication(downstream)
(RSSI) and "ETX
(upstream)" Expected Number of Transmissions(upstream)" (ETX) has been
tested to determine whether the a link is symmetric or asymmetric at the
intermediate nodes. The example of how the ETX and RSSI values are may be used in conjuction is conjunction
as explained below:

Source---------->NodeA---------->NodeB------->Destination

Figure 8: Communication link from Source to Destination

+-------------------------+----------------------------------------+
| RSSI at NodeA for NodeB | Expected ETX at NodeA for NodeB->NodeA |
+-------------------------+----------------------------------------+
| > -60 | 150 |
| -70 to -60 | 192 |
| -80 to -70 | 226 |
| -90 to -80 | 662 |
| -100 to -90 | 993 |
+-------------------------+----------------------------------------+

Table 1: Selection of 'S' S bit based on Expected ETX value

We tested the operations in this specification by making the
following experiment, using the above parameters. In our experiment,
a communication link is considered as symmetric if the ETX value of
NodeA->NodeB and NodeB->NodeA (See Figure.8) are, (see Figure 8) are within, say, within a 1:3
ratio. This ratio should be taken understood as a notional metric for deciding
link symmetric/asymmetric nature, and precise definition of the ratio
is beyond the scope of determining the draft. In general, link's
symmetric/asymmetric nature. NodeA can only typically know the ETX value
in the direction of NodeA -> NodeB but it has no direct way of
knowing the value of ETX from NodeB->NodeA. Using physical testbed
experiments and realistic wireless channel propagation models, one
can determine a relationship between RSSI and ETX representable as an
expression or a mapping table. Such a relationship in turn can be
used to estimate ETX value at nodeA for link NodeB--->NodeA from the
received RSSI from NodeB. Whenever nodeA determines that the link
towards the nodeB is bi-directional asymmetric then the "S" S bit is set
to "S=0". 0. Later on, the link from NodeA to Destination is asymmetric
with "S" S bit remains set to "0". 0.

Appendix B. Changelog

Note to the RFC Editor: please remove this section before
publication.

B.1. Changes from version 07 to version 08

o Instead of describing the need for routes to "fulfill the
requirements", specify that routes need to "satisfy the Objective
Function".

o Removed all normative dependencies on [RFC6997]

o Rewrote Section 10 to avoid duplication of language in cited
specifications.

o Added Section 11 with text and citations to more fully describe
how implementations determine whether links are symmetric.

o Modified text comparing AODV-RPL to other protocols to emphasize
the need for AODV-RPL instead of the problems with the other
protocols.

o Clarified that AODV-RPL uses some of the base RPL specification
but does not require an instance of RPL to run.

o Improved capitalization, quotation, and spelling variations.

o Specified behavior upon reception of a RREQ-DIO or RREP-DIO
message for an already existing DODAGID (e.g, Section 6.4).

o Fixed numerous language issues in IANA Considerations Section 9.

o For consistency, adjusted several mandates from SHOULD to MUST and
from SHOULD NOT to MUST NOT.

o Numerous editorial improvements and clarificaions.

B.2. Changes from version 06 to version 07

o Added definitions for all fields of the ART option (see
Section 4.3). Modified definition of Prefix Length to prohibit
Prefix Length values greater than 127.

o Modified the language from [RFC6550] Target Option definition so
that the trailing zero bits of the Prefix Length are no longer
described as "reserved".

o Reclassified RFC 3561 [RFC3561] and RFC 6998 [RFC6998] as Informative.

o Added citation to RFC 8174 for [RFC8174] to Terminology section.

B.2.

B.3. Changes from version 05 to version 06

o Added Security Considerations based on the security mechanisms
defined in RFC 6550. [RFC6550].

o Clarified the nature of improvements due to P2P route discovery
versus bidirectional asymmetric route discovery.

o Editorial improvements and corrections.

B.3.

B.4. Changes from version 04 to version 05

o Add description for sequence number operations.

o Extend the residence duration L in section 4.1.

o Change AODV-RPL Target option to ART option.

B.4.

B.5. Changes from version 03 to version 04

o Updated RREP option format. Remove the 'T' T bit in RREP option.

o Using the same RPLInstanceID for RREQ and RREP, no need to update
[RFC6550].

o Explanation of Shift field in RREP.

o Multiple target options handling during transmission.

B.5.

B.6. Changes from version 02 to version 03

o Include the support for source routing.

o Import some features from [RFC6997], e.g., choice between hop-by-
hop and source routing, the "L" L bit which determines the duration of
residence in the DAG, MaxRank, etc.

o Define new target option for AODV-RPL, including the Destination
Sequence Number in it. Move the TargNode address in RREQ option
and the OrigNode address in RREP option into ADOV-RPL Target
Option.

o Support route discovery for multiple targets in one RREQ-DIO.

o New InstanceID pairing mechanism.

Appendix C. Contributors

Abdur Rashid Sangi
Huaiyin Institute of Technology
No.89 North Beijing Road, Qinghe District
Huaian 223001
P.R. China
Email: sangi_bahrian@yahoo.com

Authors' Addresses

Satish Anamalamudi
SRM University-AP
Amaravati Campus
Amaravati, Andhra Pradesh 522 502
India

Email: satishnaidu80@gmail.com

Mingui Zhang
Huawei Technologies
No. 156 Beiqing Rd. Haidian District
Beijing 100095
China

Email: zhangmingui@huawei.com

Charles E. Perkins
Futurewei
2330 Central Expressway
Santa Clara 95050
Deep Blue Sky Networks
Saratoga 95070
United States

Email: charliep@computer.org
S.V.R Anand
Indian Institute of Science
Bangalore 560012
India

Email: anand@ece.iisc.ernet.in

Bing Liu
Huawei Technologies
No. 156 Beiqing Rd. Haidian District
Beijing 100095
China

Email: remy.liubing@huawei.com