ROLL
Internet Engineering Task Force (IETF) C.E. Perkins
Internet-Draft
Request for Comments: 9854 Blue Meadow Networks
Intended status:
Category: Standards Track S.V.R.Anand
Expires: 3 September 2025 S.V.R. Anand
ISSN: 2070-1721 Indian Institute of Science
S. Anamalamudi
SRM University-AP
B. Liu
Huawei Technologies
2 March
August 2025
Supporting Asymmetric Links in Low Power Low-Power Networks: AODV-RPL
draft-ietf-roll-aodv-rpl-20
Abstract
Route discovery for symmetric and asymmetric Peer-to-Peer (P2P)
traffic flows is a desirable feature in Low power Low-Power and Lossy Networks
(LLNs). For that purpose, this document specifies a reactive P2P
route discovery mechanism for both hop-by-hop routes and source
routing: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL
protocol (AODV-RPL). Paired Instances instances are used to construct
directional paths, paths for cases where there are asymmetric links between
source and target nodes.
Status of This Memo
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Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
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Internet Standards is available in Section 2 of RFC 7841.
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This Internet-Draft will expire on 3 September 2025.
https://www.rfc-editor.org/info/rfc9854.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 7
4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 9
4.1. AODV-RPL RREQ Option . . . . . . . . . . . . . . . . . . 9
4.2. AODV-RPL RREP Option . . . . . . . . . . . . . . . . . . 11
4.3. AODV-RPL Target Option . . . . . . . . . . . . . . . . . 13
5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 14
6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 17
6.1. Route Request Generation . . . . . . . . . . . . . . . . 17
6.2. Receiving and Forwarding RREQ messages . . . . . . . . . 18 Messages
6.2.1. Step 1: RREQ reception Reception and evaluation . . . . . . . . 18 Evaluation
6.2.2. Step 2: TargNode and Intermediate Router
determination . . . . . . . . . . . . . . . . . . . . 18 Determination
6.2.3. Step 3: Intermediate Router RREQ processing . . . . . 19 Processing
6.2.4. Step 4: Symmetric Route Processing at an Intermediate
Router . . . . . . . . . . . . . . . . . . . . . . . 20
6.2.5. Step 5: RREQ propagation Propagation at an Intermediate Router . 20
6.2.6. Step 6: RREQ reception Reception at TargNode . . . . . . . . . 21
6.3. Generating Route Reply (RREP) at TargNode . . . . . . . . 21
6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 21 Route
6.3.2. RREP-DIO for Asymmetric Route . . . . . . . . . . . . 22
6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 22
6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 23
6.4.1. Step 1: Receiving and Evaluation . . . . . . . . . . 23
6.4.2. Step 2: OrigNode or Intermediate Router . . . . . . . 23
6.4.3. Step 3: Build Route to TargNode . . . . . . . . . . . 23
6.4.4. Step 4: RREP Propagation . . . . . . . . . . . . . . 24
7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 24
8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 25
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
10. Security Considerations . . . . . . . . . . . . . . . . . . . 26
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 27
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
12.1.
11.1. Normative References . . . . . . . . . . . . . . . . . . 27
12.2.
11.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. Example: Using ETX/RSSI Values to determine value Determine Value of S
bit . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Bit
Appendix B. Some Example AODV-RPL Message Flows . . . . . . . . 32
B.1. Example control message flows Control Message Flows in symmetric Symmetric and asymmetric
networks . . . . . . . . . . . . . . . . . . . . . . . . 32 Asymmetric
Networks
B.2. Example RREP_WAIT handling . . . . . . . . . . . . . . . 34 Handling
B.3. Example G-RREP handling . . . . . . . . . . . . . . . . . 35
Appendix C. Changelog . . . . . . . . . . . . . . . . . . . . . 36
C.1. Changes from version 19 to version 20 . . . . . . . . . . 36
C.2. Changes from version 18 to version 19 . . . . . . . . . . 37
C.3. Changes from version 17 to version 18 . . . . . . . . . . 37
C.4. Changes from version 16 to version 17 . . . . . . . . . . 37
C.5. Changes from version 15 to version 16 . . . . . . . . . . 38
C.6. Changes from version 14 to version 15 . . . . . . . . . . 38
C.7. Changes from version 13 to version 14 . . . . . . . . . . 39
C.8. Changes from version 12 to version 13 . . . . . . . . . . 40
C.9. Changes from version 11 to version 12 . . . . . . . . . . 40
C.10. Changes from version 10 to version 11 . . . . . . . . . . 41
C.11. Changes from version 09 to version 10 . . . . . . . . . . 42
C.12. Changes from version 08 to version 09 . . . . . . . . . . 42
C.13. Changes from version 07 to version 08 . . . . . . . . . . 43
C.14. Changes from version 06 to version 07 . . . . . . . . . . 44
C.15. Changes from version 05 to version 06 . . . . . . . . . . 44
C.16. Changes from version 04 to version 05 . . . . . . . . . . 44
C.17. Changes from version 03 to version 04 . . . . . . . . . . 44
C.18. Changes from version 02 to version 03 . . . . . . . . . . 44
Appendix D. Handling
Acknowledgements
Contributors . . . . . . . . . . . . . . . . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46
1. Introduction
The Routing Protocol for Low-Power and Lossy Networks (RPL) [RFC6550]
is an IPv6 distance vector routing protocol designed to support
multiple traffic flows through a root-based Destination-Oriented
Directed Acyclic Graph (DODAG). Typically, a router does not have
routing information for destinations attached to most other routers.
Consequently, for traffic between routers within the DODAG (i.e.,
Peer-to-Peer (P2P) traffic) P2P
traffic), data packets either have to traverse the root in non-storing mode, 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 root (for more information information, see [RFC6687],
[RFC6997], [RFC6998], and [RFC9010]). The network environment that
is considered in this document is assumed to be the same as that
described in Section 1 of [RFC6550]. Each radio interface/
link interface/link and
the associated address should be treated as an independent
intermediate router. Such routers have different links links, and the
rules for the link symmetry apply independently for each of these.
The route discovery process in AODV-RPL is modeled on the analogous
peer-to-peer
P2P procedure specified in AODV [RFC3561]. The on-demand property of
AODV route discovery is useful for the needs of routing in RPL-based
LLNs when routes are needed but aren't yet established.
Peer-to-peer P2P routing
is desirable to discover shorter routes, and especially when it is
desired to avoid directing additional traffic through a root or
gateway node of the network. It may happen that some routes need to
be established proactively when known beforehand and when AODV-RPL's
route discovery process introduces unwanted delay
at the time when the
application is launched.
AODV terminology has been adapted for use with AODV-RPL messages,
namely RREQ "RREQ" for Route Request, "Route Request", and RREP "RREP" for Route Reply. "Route Reply".
AODV-RPL currently omits some features compared to AODV -- in
particular, flagging Route Errors, route errors, "blacklisting" unidirectional
links
([RFC3561]), [RFC3561], multihoming, and handling unnumbered interfaces.
AODV-RPL reuses and extends the core RPL functionality to support
routes with bidirectional asymmetric links. It retains RPL's DODAG
formation, RPL Instance and the associated Objective Function
(defined in [RFC6551]), trickle Trickle timers, and support for storing and
non-storing modes. AODV-RPL adds the basic messages RREQ and RREP as
part of the RPL DODAG Information Object (DIO) control message, which
go in separate (paired) RPL instances. AODV-RPL does not utilize the
Destination Advertisement Object (DAO) control message of RPL. AODV-
RPL uses the "P2P Route Discovery Mode of Operation" (MOP == 4) with
three new Options options for the DIO message, dedicated to discover discovering P2P
routes. These P2P routes may differ from routes discoverable by
native RPL. Since AODV-RPL uses newly defined Options options and a newly
allocated multicast group (see Section 9), there is no conflict with
P2P-RPL [RFC6997], a previous document using the same MOP. AODV-RPL
can be operated whether or not P2P-RPL or native RPL is running
otherwise. AODV-RPL could be used for networks in which routes are
needed with Objective Functions that cannot be satisfied by routes
that are constrained to traverse the root of the network or other
common ancestors. P2P routes often require fewer hops and therefore
consume less resources than routes that traverse the root or other
common ancestors. Similar in cost to base RPL [RFC6550], the cost
will depend on many factors such as the proximity of the OrigNode and
TargNodes and distribution of symmetric/asymmetric P2P links.
Experience with AODV [aodv-tot] suggests that AODV-RPL will often
find routes with improved rank compared to routes constrained to
traverse a common ancestor of the source and destination nodes.
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
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
AODV-RPL reuses names for messages and data structures, including
Rank, DODAG DODAG, and DODAGID, as defined in RPL [RFC6550].
This document also uses the following terms:
AODV
Ad Hoc On-demand hoc On-Demand Distance Vector Routing [RFC3561].
ART option
The AODV-RPL Target option: a target option defined in this document.
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 satisfies the Objective
Function during route discovery.
Bi-directional
Bidirectional Asymmetric Link
A link that can be used in both directions but with different link
characteristics.
DIO
DODAG Information Object (as defined in [RFC6550]) [RFC6550]).
DODAG RREQ-Instance (or simply RREQ-Instance)
An RPL Instance built using the DIO with RREQ option; used for
transmission of control messages from OrigNode to TargNode, thus
enabling data transmission from TargNode to OrigNode.
DODAG RREP-Instance (or simply RREP-Instance)
An RPL Instance built using the DIO with RREP option; used for
transmission of control messages from TargNode to OrigNode 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
Hop-by-hop route
A route for which each router along the routing path stores
routing information about the next hop. A hop-by-hop route is
created using RPL's "storing mode".
OF
An
Objective Function as (as defined in [RFC6550]. [RFC6550]).
OrigNode
The IPv6 router (Originating Node) (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
Peer-to-Peer -- in (in other words, not constrained a priori to traverse
a common ancestor. ancestor).
REJOIN_REENABLE
The duration during which a node is prohibited from joining a
DODAG with a particular RREQ-InstanceID, after it has left a DODAG
with the same RREQ-InstanceID. The default value of
REJOIN_REENABLE is 15 minutes.
RREQ
A RREQ-DIO message.
RREQ-DIO message
A DIO message containing the RREQ option. The RPLInstanceID in
RREQ-DIO is assigned locally by the OrigNode. The RREQ-DIO
message has a secure variant as noted in [RFC6550].
RREQ-InstanceID
The RPLInstanceID for the RREQ-Instance. The RREQ-InstanceID is
formed as the ordered pair (Orig_RPLInstanceID, OrigNode-IPaddr),
where Orig_RPLInstanceID is the local RPLInstanceID allocated by
OrigNode,
OrigNode and OrigNode-IPaddr is an IP address of OrigNode. The
RREQ-InstanceID uniquely identifies the RREQ-Instance.
RREP
A RREP-DIO message.
RREP-DIO message
A DIO message containing the RREP option. OrigNode pairs the
RPLInstanceID in RREP-DIO to the one in the associated RREQ-DIO
message (i.e., the RREQ-InstanceID) as described in Section 6.3.2.
The RREP-DIO message has a secure variant as noted in [RFC6550].
RREP-InstanceID
The RPLInstanceID for the RREP-Instance. The RREP-InstanceID is
formed as the ordered pair (Targ_RPLInstanceID, TargNode-IPaddr),
where Targ_RPLInstanceID is the local RPLInstanceID allocated by
TargNode,
TargNode and TargNode-IPaddr is an IP address of TargNode. The
RREP-InstanceID uniquely identifies the RREP-Instance. The
RPLInstanceID in the RREP message along with the Delta value
indicates the associated RREQ-InstanceID. The InstanceIDs are
matched by the mechanism explained in Section 6.3.3 6.3.3.
Source routing
A mechanism by which the source supplies a vector of addresses
towards the destination node along with each data packet
[RFC6550].
Symmetric route
The upstream and downstream routes traverse the same routers and
over the same links.
TargNode
The IPv6 router (Target Node) (target node) for which OrigNode requires a route
and initiates Route Discovery route discovery within the LLN.
Upward Direction
The direction from the TargNode to the OrigNode.
Upward Route
A route in the upward direction.
3. Overview of AODV-RPL
With AODV-RPL, routes from OrigNode to TargNode within the LLN do not
become established until they are needed. The route discovery
mechanism in AODV-RPL is invoked when OrigNode has data for delivery
to a TargNode, but existing routes do not satisfy the application's
requirements. For this reason reason, AODV-RPL is considered to be an
example of an "on-demand" routing protocols. protocol. Such protocols are also
known as "reactive" routing protocols since their operations are
triggered in reaction to a determination that a new route is needed.
AODV-RPL works 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. 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, TargNode and another from TargNode to OrigNode. AODV-RPL also
enables discovery of symmetric routes along Paired paired DODAGs, when
symmetric routes are possible (see Section 5).
In AODV-RPL, routes are discovered by first forming a temporary DAG
Directed Acyclic Graph (DAG) rooted at the OrigNode. Paired DODAGs
(Instances) are constructed during route formation between the
OrigNode and TargNode. The RREQ-
Instance RREQ-Instance is formed by route control
messages from OrigNode to
TargNode TargNode, whereas the RREP-Instance is
formed by route control messages from TargNode to OrigNode. 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.
Intermediate routers join the DODAGs based on the Rank [RFC6550] as
calculated from the DIO messages. AODV-RPL uses the same notion of
rank as defined in RFC6550: "The [RFC6550]:
| The Rank is the expression of a relative position within a DODAG
| Version with regard to neighbors, and it is not necessarily a good
| indication or a proper expression of a distance or a path cost to
| the root." root.
The Rank measurements provided in AODV messages do not indicate a
distance or a path cost to the root.
Henceforth in this document, "RREQ-DIO message" means the DIO message
from OrigNode toward TargNode, containing the RREQ option as
specified in Section 4.1. The RREQ-InstanceID is formed as the
ordered pair (Orig_RPLInstanceID, OrigNode-IPaddr), where
Orig_RPLInstanceID is the local RPLInstanceID allocated by OrigNode, OrigNode
and OrigNode-IPaddr is the IP address of OrigNode. A node receiving
the RREQ-DIO can use the RREQ-InstanceID to identify the proper OF
whenever that node receives a data packet with Source Address ==
OrigNode-IPaddr and IPv6 RPL Option having the RPLInstanceID ==
Orig_RPLInstanceID. The 'D' D bit of the RPLInstanceID field is set to 0
to indicate that the source address of the IPv6 packet is the
DODAGID.
Similarly, "RREP-DIO message" means the DIO message from TargNode
toward OrigNode, containing the RREP option as specified in
Section 4.2. The RREP-InstanceID is formed as the ordered pair
(Targ_RPLInstanceID, TargNode-IPaddr), where Targ_RPLInstanceID is
the local RPLInstanceID allocated by TargNode, TargNode and TargNode-IPaddr is
the IP address of TargNode. A node receiving the RREP-DIO can use
the RREP-InstanceID to identify the proper OF whenever that node
receives a data packet with Source Address == TargNode-IPaddr and
IPv6 RPL Option having the RPLInstanceID == Targ_RPLInstanceID along
with 'D' D == 0 as above.
4. AODV-RPL DIO Options
4.1. AODV-RPL RREQ Option
OrigNode selects one of its IPv6 addresses and sets it in the DODAGID
field of the RREQ-DIO message. The address scope of the selected
address MUST encompass the domain where the route is built (e.g, not
link-local); otherwise otherwise, the route discovery will fail. Exactly one
RREQ option MUST be present in a RREQ-DIO message, otherwise message; otherwise, the
message MUST 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 | RankLimit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Orig SeqNo | |
+-+-+-+-+-+-+-+-+ |
| |
| Address Vector (Optional, Variable Length) |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . .
Figure 1: Format for AODV-RPL RREQ Option
OrigNode supplies the following information in the RREQ option:
Option Type
8-bit unsigned integer specifying the type of the option (TBD2) (0x0B).
Option Length
8-bit unsigned integer specifying the length of the option in
octets, excluding the Type and Length fields. Variable It is 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. See Section 5.
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;
Reserved. This field MUST be initialized to zero and ignored upon
reception.
Compr
4-bit unsigned integer. When Compr is nonzero, exactly that
number of prefix octets MUST be elided from each address before
storing it in 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 time duration that a node
is able to belong to the RREQ-Instance (a temporary DAG including
the OrigNode and the TargNode). Once the time is reached, a node
SHOULD leave the RREQ-Instance and stop sending or receiving any
more DIOs for the RREQ-Instance; otherwise otherwise, memory and network
resources are likely to be consumed unnecessarily. This naturally
depends on the node's ability to keep track of time. Once a node
leaves an RREQ-Instance, it MUST NOT rejoin the same RREQ-Instance
for at least the time interval specified by the configuration
variable REJOIN_REENABLE. L is independent from the route
lifetime, which is defined in the DODAG configuration option.
* 0x00: No time limit imposed. imposed
* 0x01: 16 seconds
* 0x02: 64 seconds
* 0x03: 256 seconds
RankLimit
8-bit unsigned integer specifying the upper limit on the integer
portion of the Rank (calculated using the DAGRank() macro defined
in [RFC6550]). A value of 0 in this field indicates the limit is
infinity.
Orig SeqNo
8-bit unsigned integer specifying the sequence Number of 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 bit is set to 0.
The prefix of each address is elided according to the Compr field.
TargNode can join the RREQ instance RREQ-Instance at a Rank whose integer portion
is less than or equal to the RankLimit. Any other node MUST NOT join
a RREQ instance RREQ-Instance if its own Rank would be equal to or higher than the
RankLimit. A router MUST discard a received RREQ if the integer part
of the advertised Rank equals or exceeds the RankLimit.
4.2. AODV-RPL RREP Option
TargNode sets one of its IPv6 addresses in the DODAGID field of the
RREP-DIO message. The address scope of the selected address must
encompass the domain where the route is built (e.g, not link-local).
Exactly one RREP option MUST be present in a RREP-DIO message,
otherwise
otherwise, the message MUST 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 | RankLimit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Delta |X X| |
+-+-+-+-+-+-+-+-+ |
| |
| |
| Address Vector (Optional, Variable Length) |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . .
Figure 2: Format for AODV-RPL RREP option Option
Option Type
8-bit unsigned integer specifying the type of the option (TBD3) (0x0C).
Option Length
8-bit unsigned integer specifying the length of the option in
octets, excluding the Type and Length fields. Variable It is variable due
to the presence of the address vector and the number of octets
elided according to the Compr value.
G
Gratuitous RREP (see Section 7).
H
The H bit in the RREP option MUST be set to be the same as the H
bit in the RREQ option. It requests either source routing (H=0)
or hop-by-hop (H=1) for the downstream route.
X
1-bit Reserved field; field. This field MUST be initialized to zero and
ignored upon reception.
Compr
4-bit unsigned integer. Same This field has the same definition as in
the RREQ option.
L
2-bit unsigned integer defined as in the RREQ option. The
lifetime of the RREP-Instance SHOULD be no greater than the
lifetime of the RREQ-Instance to which it is paired, so that the
memory required to store the RREP-Instance can be reclaimed when
no longer needed.
RankLimit
8-bit unsigned integer specifying the upper limit on the integer
portion of the Rank, similarly to RankLimit in the RREQ message.
A value of 0 in this field indicates the limit is infinity.
Delta
6-bit unsigned integer. TargNode uses the Delta field so that
nodes receiving its RREP message can identify the RREQ-InstanceID
of the RREQ message that triggered the transmission of the RREP
(see Section 6.3.3).
X X
2-bit Reserved field; field. This field MUST be initialized to zero and
ignored upon reception.
Address Vector
Only present when the H bit is set to 0. The prefix of each
address is elided according to the Compr field. For an asymmetric
route, the Address Vector represents the IPv6 addresses of the
path through the network the RREP-DIO has passed. In contrast,
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 Target Option
The AODV-RPL Target (ART) Option option is based on the Target Option option in the
core RPL specification [RFC6550]. The Flags field is replaced by the
Destination Sequence Number of the TargNode 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. option. A RREP-DIO
message MUST carry exactly one ART Option. option. Otherwise, the message
MUST be dropped.
OrigNode can include multiple TargNode addresses via multiple AODV-
RPL Target Options ART
options in the RREQ-DIO, for routes that share the same requirement
on metrics. This reduces the cost to building only one DODAG for
multiple targets.
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 |X|Prefix Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ |
| Target Prefix / Address (Variable Length) |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . .
Figure 3: ART Option format Format for AODV-RPL
Option Type
8-bit unsigned integer specifying the type of the option (TBD4) (0x0D).
Option Length
8-bit unsigned integer specifying the length of the option in
octets
octets, excluding the Type and Length fields.
Dest SeqNo
8-bit unsigned integer. In RREQ-DIO, if nonzero, it is the
Sequence Number for the last route that OrigNode stored to the
TargNode for which a route is desired. In RREP-DIO, it is the
destination sequence number associated to the route. Zero is used
if there is no known information about the sequence number of
TargNode,
TargNode and not used otherwise.
X
A one-bit reserved
1-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. The Prefix Length field contains the
number of valid leading bits in the 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
A variable-length field with an IPv6 destination address or
prefix. The length of the Target Prefix / Address field is the
least number of octets that can represent all of the bits of the
Prefix, in other words words, Ceil(Prefix Length/8) octets. When Prefix
Length is not equal to 8*Ceil(Prefix Length/8) and nonzero, the
Target Prefix / Address field will contain some initial bits that
are not part of the Target Prefix. Those initial bits (if any)
MUST be set to zero on transmission and MUST be ignored on
receipt. If Prefix Length is zero, the Address field is 128 bits.
5. Symmetric and Asymmetric Routes
Links are considered symmetric until indication to the contrary is
received. In Figure Figures 4 and Figure 5, BR is the Border Router, O is the
OrigNode, each R is an intermediate router, and T is the TargNode.
In this example, these examples, the use of BR is only for illustrative purposes;
AODV does not depend on the use of border routers for its operation.
If the RREQ-DIO arrives over an interface that is known to be symmetric,
symmetric and the 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 bit set to 1, then each link en route from the
OrigNode O to this router has met 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 Instances
Upon receiving a RREQ-DIO with the S bit set to 1, a node determines
whether the link over which it was received can be used
symmetrically, i.e., both directions meet the requirements of data
transmission. If the RREQ-DIO arrives over an interface that is not
known to be symmetric, symmetric or is known to be asymmetric, the S bit is set
to 0. If the S bit arrives already set to be '0', 0, then it is set to be
'0'
0 when the RREQ-DIO is propagated (Figure 5). For an asymmetric
route, there is at least one hop which that doesn't satisfy the Objective
Function. Based on the S bit received in RREQ-DIO, TargNode T
determines whether or not the route is symmetric before transmitting
the RREP-DIO message upstream towards the OrigNode O.
It is beyond the scope of this document to specify the criteria used
when determining whether or not each link is symmetric. As an
example, intermediate routers can use local information (e.g., bit
rate, bandwidth, number of cells used in 6tisch [RFC9030]), a priori
knowledge (e.g., link quality according to previous communication) communication),
or
use averaging techniques as appropriate to the application. Other
link metric information can be acquired before AODV-RPL operation, by
executing evaluation procedures; for instance instance, test traffic can be
generated between nodes of the deployed network. During AODV-RPL
operation, OAM Operations, Administration, and Maintenance (OAM)
techniques for evaluating link state (see [RFC7548], [RFC7276], and
[co-ioam]) MAY be used (at regular intervals appropriate for the
LLN). The evaluation procedures are out of scope for AODV-
RPL. AODV-RPL. For
further information on this topic, see [Link_Asymmetry],
[low-power-wireless], and [empirical-study].
Appendix A describes an example method using the upstream Expected
Number of Transmissions
Transmission Count (ETX) and downstream Received Signal Strength
Indicator (RSSI) to estimate whether the link is symmetric in terms
of link quality 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
As illustrated in Figure 5, an intermediate router determines the S
bit value that the RREQ-DIO should carry using link asymmetry
detection methods as discussed earlier in this section. In many
cases
cases, the intermediate router has already made the link asymmetry
decision by the time RREQ-DIO arrives.
See Appendix B for examples illustrating RREQ and RREP transmissions
in some networks with symmetric and asymmetric links.
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, TargNode but does not have
a route that satisfies the Objective Function for the target of the
application's data. In this case, the OrigNode builds a local
RPLInstance and a DODAG rooted at itself. Then Then, it transmits a DIO
message containing exactly one RREQ option (see Section 4.1) to
multicast group all-AODV-RPL-nodes. The RREQ-DIO MUST contain at
least one ART Option option (see Section 4.3), which indicates the TargNode.
The S bit in RREQ-DIO sent out by the OrigNode is set to 1.
Each node maintains a sequence number; the operation is specified in
section
Section 7.2 of [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 Orig SeqNo field of the RREQ option.
The Target Prefix / Address in the ART Option 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.
options. Within a RREQ-DIO RREQ-DIO, the Objective Function 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 RPLInstanceID
pairing mechanism (see Section 6.3.3), route replies (RREP-DIOs) for
different RPLInstances can be generated.
The transmission of RREQ-DIO obeys the Trickle timer [RFC6206]. If
the duration specified by the L field has elapsed, the OrigNode MUST
leave the DODAG and stop sending RREQ-DIOs in the related
RPLInstance. OrigNode needs to set the L field such that the DODAG
will not prematurely timeout during data transfer with the TargNode.
For setting this value, it has to consider factors such as the
Trickle timer, TargNode hop distance, network size, link behavior,
expected data usage time, and so on.
6.2. Receiving and Forwarding RREQ messages Messages
6.2.1. Step 1: RREQ reception Reception and evaluation Evaluation
When a router X receives a RREQ message over a link from a neighbor
Y, X first determines whether or not the RREQ is valid. If so, X
then determines whether or not it has sufficient resources available
to maintain the RREQ-Instance and the value of the 'S' S bit needed to
process an eventual RREP, if the RREP were to be received. If not,
then X MUST either free up sufficient resources (the means for this
are beyond the scope of this document), document) or drop the packet and
discontinue processing of the RREQ. Otherwise, X next determines
whether the RREQ advertises a usable route to OrigNode, by checking
whether the link to Y can be used to transmit packets to OrigNode.
When H=0 in the incoming RREQ, the router MUST drop the RREQ-DIO if
one of its addresses is present in the Address Vector. When H=1 in
the incoming RREQ, the router MUST drop the RREQ message if the Orig
SeqNo field of the RREQ is older than the SeqNo value that X has
stored for a route to OrigNode. Otherwise, the router determines
whether to propagate the RREQ-DIO. It does this by determining
whether or not a route to OrigNode using the upstream direction of
the incoming link satisfies the Objective Function (OF). In order to
evaluate the OF, the router first determines the maximum useful rank
(MaxUsefulRank). If the router has previously joined the RREQ-
Instance associated with the RREQ-DIO, then MaxUsefulRank 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. Otherwise,
MaxUsefulRank is set to be RankLimit. If OF cannot be satisfied
(i.e., the Rank evaluates to a value greater than MaxUsefulRank) MaxUsefulRank), the
RREQ-DIO MUST be dropped, and the following steps are not processed.
Otherwise, the router MUST join the RREQ-Instance and prepare to
propagate the RREQ-DIO, as follows. The upstream neighbor router
that transmitted the received RREQ-DIO is selected as the preferred
parent in the RREQ-Instance.
6.2.2. Step 2: TargNode and Intermediate Router determination Determination
After determining that a received RREQ provides a usable route to
OrigNode, a router determines whether it is a TargNode, or a possible
intermediate router between OrigNode and a TargNode, or both. The
router is a TargNode if it finds one of its own addresses in a Target
Option
option in the RREQ. After possibly propagating the RREQ according to
the procedures in Steps 3, 4, and 5, the TargNode generates a RREP as
specified in Section 6.3. If S=0, the determination of TargNode
status and determination of a usable route to OrigNode is the same.
If the OrigNode tries to reach multiple TargNodes in a single RREQ-
Instance, one of the TargNodes can be an intermediate router to other
TargNodes. In this case, before transmitting the RREQ-DIO to
multicast group all-AODV-RPL-nodes, a TargNode MUST delete the Target
Option
option encapsulating its own address, so that downstream routers with
higher Rank values do not try to create a route to this TargNode.
An intermediate router could receive several RREQ-DIOs from routers
with lower Rank values in the same RREQ-Instance with different lists
of Target Options. options. 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 for a given RREQ-
Instance. An incoming RREQ-DIO message having multiple ART Options options
coming from a router with higher Rank than the Rank of the stored
targets is ignored. When transmitting the RREQ-DIO, the intersection
of all received lists MUST be included if it is nonempty after
TargNode has deleted the Target Option option encapsulating its own address.
If the intersection is empty, it means that all the targets have been
reached, and the router MUST NOT transmit any RREQ-DIO. Otherwise Otherwise,
it proceeds to Section 6.2.3.
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
Then, only T2 needs to be included in the generated RREQ-DIO.
The reasoning for using the intersection of the lists in the RREQs is
as follows. When two or more RREQs are received with the same Orig
SeqNo, they were transmitted by OrigNode with the same destinations
and OF. When an intermediate node receives two RREQs with the same
Orig SeqNo but different lists of destinations, that means that some
intermediate nodes retransmitting the RREQs have already deleted
themselves from the list of destinations before they retransmitted
the RREQ. Those deleted nodes are not to be re-inserted reinserted back into the
list of destinations.
6.2.3. Step 3: Intermediate Router RREQ processing Processing
The intermediate router establishes itself as a viable node for a
route to OrigNode as follows. If the H bit is set to 1, for a hop-
by-hop route, then the router MUST build or update its upward route
entry towards OrigNode, which includes at least the following items:
Source Address, RPLInstanceID, Destination Address, Next Hop,
Lifetime, and Sequence Number. The Destination Address and the
RPLInstanceID respectively can be learned from the DODAGID and the RPLInstanceID
of the RREQ-DIO. RREQ-DIO, respectively. The Source Address is the address
used by the router to send data to the Next Hop, i.e., the preferred
parent. The lifetime is set according to DODAG configuration (not
the L field) and can be extended when the route is actually used.
The Sequence Number represents the freshness of the route entry; it
is copied from the Orig SeqNo field of the RREQ option. A route
entry with the same source and destination address, address and the same
RPLInstanceID, but a stale Sequence Number (i.e., incoming sequence
number is less than the currently stored Sequence Number of the route
entry), MUST be deleted.
6.2.4. Step 4: Symmetric Route Processing at an Intermediate Router
If the S bit of the incoming RREQ-DIO is 0, then the route cannot be
symmetric, and the S bit of the RREQ-DIO to be transmitted is set to
0. Otherwise, the router MUST determine whether the downward
direction (i.e., towards the TargNode) direction of the incoming link satisfies
the OF. If so, the S bit of the RREQ-DIO to be transmitted is set to
1.
Otherwise Otherwise, the S bit of the RREQ-DIO to be transmitted is set to
0.
When a router joins the RREQ-Instance, it also associates within its
data structure for the RREQ-Instance the information about whether or
not the RREQ-DIO to be transmitted has the S-bit S bit set to 1. This
information associated to RREQ-Instance is known as the S-bit S bit of the
RREQ-Instance. It will be used later during the RREP-DIO message
processing (see Section 6.3.2. 6.3.2).
Suppose a router has joined the RREQ-Instance, and H=0, and the S-bit S bit
of the RREQ-Instance is set to 1. In this case, the router MAY
optionally include the Address Vector of the symmetric route back to
OrigNode as part of the RREQ-Instance data. This is useful if the
router later receives an RREP-DIO that is paired with the RREQ-
Instance. If the router does NOT include the Address Vector, then it
has to rely on multicast for the RREP. The multicast can impose a
substantial performance penalty.
6.2.5. Step 5: RREQ propagation Propagation at an Intermediate Router
If the router is an intermediate router, then it transmits the RREQ-
DIO to the multicast group all-AODV-RPL-nodes; if the H bit is set to
0, the intermediate router MUST append the address of its interface
receiving the RREQ-DIO into the address vector. If, in In addition, if the
address of the router's interface transmitting the RREQ-DIO is not
the same as the address of the interface receiving the RREQ-DIO, the
router MUST also append the transmitting interface address into the
address vector.
6.2.6. Step 6: RREQ reception Reception at TargNode
If the router is a TargNode and was already associated with the RREQ-
Instance, it takes no further action and does not send an RREP-DIO.
If TargNode is not already associated with the RREQ-Instance, it
prepares and transmits a RREP-DIO, possibly after waiting for
RREP_WAIT_TIME, as detailed in (Section 6.3).
6.3. Generating Route Reply (RREP) at TargNode
When a TargNode receives a RREQ message over a link from a neighbor
Y, TargNode first follows the procedures in Section 6.2. If the link
to Y can be used to transmit packets to OrigNode, TargNode generates
a RREP according to the steps below. Otherwise Otherwise, TargNode drops the
RREQ and does not generate a RREP.
If the L field is not 0, the TargNode MAY delay transmitting the
RREP-DIO for the 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 duration determined by the L field. For L == 0, RREP_WAIT_TIME
is set by default to 0. Depending upon the application,
RREP_WAIT_TIME may be set to other values. Smaller values enable
quicker formation for the P2P route. Larger values enable formation
of P2P routes with better Rank values.
The address of the OrigNode MUST be encapsulated in the ART Option option
and included in this RREP-DIO message along with the SeqNo of
TargNode.
6.3.1. RREP-DIO for Symmetric route Route
If the RREQ-Instance corresponding to the RREQ-DIO that arrived at
TargNode has the S bit set to 1, there is a symmetric route route, both of
whose directions satisfy the Objective Function. Other RREQ-DIOs
might later provide better upward routes. The method of selection
between a qualified symmetric route and an asymmetric route that
might have better performance is implementation-specific implementation specific and out of
scope.
For a symmetric route, the RREP-DIO message is unicast to the next
hop according to the Address Vector (H=0) or the route entry (H=1);
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 If the H bit is set to 0, the address vector from the
RREQ-DIO MUST be included in the RREP-DIO.
6.3.2. RREP-DIO for Asymmetric Route
When a RREQ-DIO arrives at a TargNode with the S bit set to 0, the
TargNode MUST build a DODAG in the RREP-Instance corresponding to the
RREQ-DIO rooted at itself, in order to provide OrigNode with a
downstream route to the TargNode. The RREP-DIO message is
transmitted to multicast group all-AODV-RPL-nodes.
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. It is possible that multiple route
discoveries with dissimilar Objective Functions are initiated
simultaneously. Thus Thus, between the same pair of OrigNode and
TargNode, there can be multiple AODV-RPL route discovery instances.
So that OrigNode and Targnode TargNode can avoid any mismatch, they MUST pair
the RREQ-Instance and the RREP-Instance in the same route discovery
by using the RPLInstanceID.
When preparing the RREP-DIO, a TargNode could find the RPLInstanceID
candidate for the RREP-Instance is already occupied by another RPL
Instance from an earlier route discovery operation which that is still
active. This unlikely case might happen if two distinct OrigNodes
need routes to the same TargNode, and they happen to use the same
RPLInstanceID for RREQ-Instance. In such cases, the RPLInstanceID of
an already active RREP-Instance MUST NOT be used again for assigning
RPLInstanceID for the later RREP-Instance. If the same RPLInstanceID
were re-used reused for two distinct DODAGs originated with the same DODAGID
(TargNode address), intermediate routers could not distinguish
between these DODAGs (and their associated Objective Functions).
Instead, the RPLInstanceID MUST be replaced by another value so that
the two RREP-instances RREP-Instances can be distinguished. In the RREP-DIO option,
the Delta field of the RREP-DIO message (Figure 2) indicates the
value that TargNode adds to the RPLInstanceID in the RREQ-DIO that it
received, to obtain the value of the RPLInstanceID it uses in the
RREP-DIO message. 0 indicates that the RREQ-InstanceID has the same
value as the RPLInstanceID of the RREP message. When the new
RPLInstanceID after incrementation exceeds 255, it rolls over
starting at 0. For example, if the RREQ-InstanceID is 252, 252 and
incremented by 6, the new RPLInstanceID will be 2. Related
operations can be found in Section 6.4. RPLInstanceID collisions do
not occur across RREQ-DIOs; the DODAGID equals the OrigNode address
and is sufficient to disambiguate between DODAGs.
6.4. Receiving and Forwarding Route Reply
Upon receiving a RREP-DIO, a router which that already belongs to the
RREP-Instance RREP-
Instance SHOULD drop the RREP-DIO. Otherwise Otherwise, the router performs
the steps in the following subsections.
6.4.1. Step 1: Receiving and Evaluation
If the Objective Function is not satisfied, the router MUST NOT join
the DODAG; the router MUST discard the RREP-DIO, RREP-DIO and does not execute
the remaining steps in this section. An Intermediate Router MUST
discard a RREP if one of its addresses is present in the Address
Vector,
Vector and does not execute the remaining steps in this section.
If the S bit of the associated RREQ-Instance is set to 1, the router
MUST proceed to Section 6.4.2.
If the S-bit S bit of the RREQ-Instance is set to 0, the router MUST
determine whether the downward direction of the link (towards the
TargNode) over which the RREP-DIO is received satisfies the Objective
Function,
Function and whether the router's Rank would not exceed the
RankLimit. If so, the router joins the DODAG of the RREP-Instance.
The router that transmitted the received RREP-DIO is selected as the
preferred parent. Afterwards, other RREP-DIO messages can be
received; AODV-
RPL AODV-RPL does not specify any action to be taken in such
cases.
6.4.2. Step 2: OrigNode or Intermediate Router
The router updates its stored value of the TargNode's sequence number
according to the value provided in the ART option. The router next
checks if one of its addresses is included in the ART Option. option. If so,
this router is the OrigNode of the route discovery. Otherwise, it is
an intermediate router.
6.4.3. Step 3: Build Route to TargNode
If the H bit is set to 1, then the router (OrigNode or intermediate)
MUST build a downward route entry towards TargNode which that includes at
least the following items: OrigNode Address, RPLInstanceID, TargNode
Address as destination, Next Hop, Lifetime Lifetime, and Sequence Number. For
a symmetric route, the Next Hop in the route entry is the router from
which the RREP-DIO is received. For an asymmetric route, the Next
Hop is the preferred parent in the DODAG of RREP-Instance. The
RPLInstanceID in the route entry MUST be the RREQ-InstanceID (i.e.,
after subtracting the Delta field value from the value of the
RPLInstanceID). The source address is learned from the ART Option, option,
and the destination address is learned from the DODAGID. The
lifetime is set according to DODAG configuration (i.e., not the L
field) and can be extended when the route is actually used. The
sequence number represents the freshness of the route entry, entry and is
copied from the Dest SeqNo field of the ART option of the RREP-DIO.
A route entry with the same source and destination address, address and the
same RPLInstanceID, but a stale sequence number number, MUST be deleted.
6.4.4. Step 4: RREP Propagation
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,
the RREP will be propagated towards OrigNode. If H=0, the
intermediate router MUST include the address of the interface
receiving the RREP-DIO into the address vector. If H=1, according to
the previous step step, the intermediate router has set up a route entry
for TargNode. If the intermediate router has a route to OrigNode, it
uses that route to unicast the RREP-DIO to OrigNode. Otherwise, in
the case of a symmetric route, the RREP-DIO message is unicast to the
Next Hop according to the address vector in the RREP-DIO (H=0) or the
local route entry (H=1). Otherwise, in the case of an asymmetric
route, the intermediate router transmits the RREP-DIO to multicast
group all-AODV-RPL-nodes. The RPLInstanceID in the transmitted RREP-DIO RREP-
DIO is the same as the value in the received RREP-DIO.
7. Gratuitous RREP
In some cases, an Intermediate router that receives a RREQ-DIO
message MAY unicast a "Gratuitous" Gratuitous RREP-DIO (G-RREP-DIO) message back
to OrigNode before continuing the transmission of the RREQ-DIO
towards TargNode. The Gratuitous RREP (G-RREP) allows the OrigNode
to start transmitting data to TargNode sooner. The G bit of the RREP
option is provided to distinguish the Gratuitous RREP-DIO G-RREP-DIO (G=1) sent by the
Intermediate router from the RREP-DIO sent by TargNode (G=0).
The gratuitous RREP-DIO G-RREP-DIO MAY be sent out when the Intermediate router receives
a RREQ-DIO for a TargNode, TargNode and the router has a pair of downward and
upward routes to the TargNode which that also satisfy the Objective
Function and for which the destination sequence number is at least as
large as the sequence number in the RREQ-DIO message. After
unicasting the Gratuitous RREP G-RREP to the OrigNode, the Intermediate router then
unicasts the RREQ towards TargNode, so that TargNode will have the
advertised route towards OrigNode along with the RREQ-InstanceID for
the RREQ-Instance. An upstream intermediate router that receives
such a G-RREP MUST also generate a G-RREP and send it further
upstream towards OrigNode.
In case of source routing, the intermediate router MUST include the
address vector between the OrigNode and itself in the Gratuitous
RREP. G-RREP. It
also includes the address vector in the unicast RREQ-DIO towards
TargNode. Upon reception of the unicast RREQ-DIO, the TargNode will
have a route address vector from itself to the OrigNode. Then Then, the
router MUST include the address vector from the TargNode to the
router itself in the gratuitous RREP-DIO G-RREP-DIO to be transmitted.
For establishing hop-by-hop routes, the intermediate router MUST
unicast the received RREQ-DIO to the Next Hop on the route. The Next
Hop router along the route MUST build new route entries with the
related RPLInstanceID and DODAGID in the downward direction. This
process repeats at each node until the RREQ-DIO arrives at the
TargNode. Then Then, the TargNode and each router along the path towards
OrigNode MUST unicast the RREP-DIO hop-by-hop towards OrigNode as
specified in Section 6.3.
8. Operation of Trickle Timer
RREQ-Instance/RREP-Instance multicast uses trickle Trickle timer operations
[RFC6206] to control RREQ-DIO and RREP-DIO transmissions. The
Trickle control of these DIO transmissions follows the procedures
described in the Section 8.3 of [RFC6550] entitled "DIO Transmission".
If the route is symmetric, the RREP DIO RREP-DIO does not need the Trickle
timer mechanism.
9. IANA Considerations
Note to RFC editor:
The sentence "The parenthesized numbers are only suggestions." is to
be removed prior publication.
A Subregistry in this section refers to a named sub-registry of the
"Routing Protocol for Low Power and Lossy Networks (RPL)" registry.
AODV-RPL uses the "P2P Route Discovery Mode of Operation" (MOP == 4) 4),
with new Options options as specified in this document. Please cite AODV-RPL
and this This document has
been added as one an additional reference for "P2P Route Discovery Mode
of Operation" in the protocols using MOP 4. "Mode of Operation" registry within the "Routing
Protocol for Low Power and Lossy Networks (RPL)" registry group.
IANA is asked to assign has assigned the three new AODV-RPL options "RREQ", "RREP" and
"ART", as described in Figure 6 from Table 1
in the "RPL Control Message Options" Subregistry. The parenthesized numbers are only
suggestions.
+-------------+------------------------+---------------+ registry within the "Routing
Protocol for Low Power and Lossy Networks (RPL)" registry group.
+=======+=============+===========+
| Value | Meaning | Reference |
+-------------+------------------------+---------------+
+=======+=============+===========+
| TBD2 (0x0B) 0x0B | RREQ Option | This document RFC 9854 |
+-------------+------------------------+---------------+
+-------+-------------+-----------+
| TBD3 (0x0C) 0x0C | RREP Option | This document RFC 9854 |
+-------------+------------------------+---------------+
+-------+-------------+-----------+
| TBD4 (0x0D) 0x0D | ART Option | This document RFC 9854 |
+-------------+------------------------+---------------+
Figure 6:
+-------+-------------+-----------+
Table 1: AODV-RPL Options
IANA is requested to allocate a new has allocated the permanent multicast address with link-local
scope called all-AODV-RPL-nodes in Table 2 for nodes implementing this specification from specification. This
allocation has been made in the "Local Network Control Block
(224.0.0.0 - 224.0.0.255 (224.0.0/24))" registry in within the "IPv4
Multicast Address Space Registry" registry group.
+=============+====================+============+
| Address(es) | Description | References |
+=============+====================+============+
| 224.0.0.69 | all-AODV-RPL-nodes | RFC 9854 |
+-------------+--------------------+------------+
Table 2: Permanent Multicast Address with
Link-Local Scope
10. Security Considerations
The security considerations for the operation of AODV-RPL are similar
to those for the operation of RPL (as described in Section 19 of the
RPL specification [RFC6550]). Sections 6.1 and 10 of [RFC6550]
describe RPL's optional security framework, which AODV-RPL relies on
to provide data confidentiality, authentication, replay protection,
and delay protection services. Additional analysis for the security
threats to RPL can be found in [RFC7416].
A router can join a temporary DAG created for a secure AODV-RPL route
discovery only if it can support the security configuration in use
(see Section 6.1 of [RFC6550]), which also specifies the key in use.
It does not matter whether the key is preinstalled or dynamically
acquired. The router must have the key in use before it can join the
DAG being created for secure route discovery.
If a rogue router knows the key for the security configuration in
use, it can join the secure AODV-RPL route discovery and cause
various types of damage. Such a rogue router could advertise false
information in its DIOs in order to include itself in the discovered
route(s). It could generate bogus RREQ-DIO, 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. When rogue routers might be
present, RPL's preinstalled mode of operation, where the key to use
for route discovery is preinstalled, SHOULD be used.
When a RREQ-DIO message uses the source routing option by setting the
H bit to 0, a rogue router may populate the Address Vector field with
a set of addresses that may result in the RREP-DIO traveling in a
routing loop.
If a rogue router is able to forge a gratuitous RREP, G-RREP, it could mount
denial-of-service denial-
of-service attacks.
12.
11. References
12.1.
11.1. 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>.
[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>.
[RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
and D. Barthel, "Routing Metrics Used for Path Calculation
in Low-Power and Lossy Networks", RFC 6551,
DOI 10.17487/RFC6551, March 2012,
<https://www.rfc-editor.org/info/rfc6551>.
[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>.
12.2.
11.2. Informative References
[aodv-tot] Perkins, C.E. and E.M. Royer, "Ad-hoc On-demand Distance
Vector Routing", Proceedings WMCSA'99. Second IEEE
Workshop on Mobile Computing Systems and Applications , Applications, pp.
90-100, February 1999.
[co-ioam] Rashmi Ballamajalu, R., Anand, S.V.R., and Malati M. Hegde, "Co-
iOAM: "Co-iOAM:
In-situ Telemetry Metadata Transport for Resource
Constrained Networks within IETF Standards Framework",
2018 10th International Conference on Communication
Systems & Networks (COMSNETS) pp.573-576, (COMSNETS), pp. 573-576, January 2018.
[contiki] Contiki contributors, "The Contiki Open Source OS for the Internet of Things
(Contiki Version 2.7)", commit 7635906, November 2013,
<https://github.com/contiki-os/contiki>.
[Contiki-ng]
Contiki-NG contributors,
"Contiki-NG: The OS for Next Generation IoT Devices
(Contiki-NG Version 4.6)", commit 3b0bc6a, December 2020,
<https://github.com/contiki-ng/contiki-ng>.
[cooja] Contiki/Cooja contributors, "Cooja Simulator for Wireless Sensor Networks (Contiki/Cooja (Contiki/
Cooja Version 2.7)", commit 7635906, November 2013, <https://github.com/contiki-
os/contiki/tree/master/tools/cooja>.
<https://github.com/contiki-os/contiki/tree/master/tools/
cooja>.
[empirical-study]
Prasant
Misra, Nadeem P., Ahmed, N., and Sanjay S. Jha, "An empirical study of
asymmetry in low-power wireless links", IEEE
Communications Magazine (Volume: Magazine, vol. 50, Issue: 7), no. 7, pp. 137-146, July
2012.
[Link_Asymmetry]
Lifeng
Sang, Anish L., Arora, A., and Hongwei H. Zhang, "On Link Asymmetry and
One-way Estimation in Wireless Sensor Networks", ACM
Transactions on Sensor Networks, Volume 6
Issue 2 pp.1-25, February vol. 6, no. 2, pp. 1-25,
DOI 10.1145/1689239.1689242, March 2010,
<https://doi.org/10.1145/1689239.1689242>.
[low-power-wireless]
Kannan
Srinivasan, Prabal K., Dutta, Arsalan P., Tavakoli, A., and
Philip P. Levis, "An
empirical study of low-power wireless", ACM Transactions
on Sensor Networks (Volume 6 Issue 2
pp.1-49), February Networks, vol. 6, no. 2, pp. 1-49,
DOI 10.1145/1689239.1689246, March 2010,
<https://doi.org/10.1145/1689239.1689246>.
[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>.
[RFC6687] Tripathi, J., Ed., de Oliveira, J., Ed., and JP. Vasseur,
Ed., "Performance Evaluation of the Routing Protocol for
Low-Power and Lossy Networks (RPL)", RFC 6687,
DOI 10.17487/RFC6687, October 2012,
<https://www.rfc-editor.org/info/rfc6687>.
[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, DOI 10.17487/RFC6998, August 2013,
<https://www.rfc-editor.org/info/rfc6998>.
[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>.
[RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A.,
and M. Richardson, Ed., "A Security Threat Analysis for
the Routing Protocol for Low-Power and Lossy Networks
(RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015,
<https://www.rfc-editor.org/info/rfc7416>.
[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>.
[RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary",
RFC 7991, DOI 10.17487/RFC7991, December 2016,
<https://www.rfc-editor.org/info/rfc7991>.
[RFC9010] Thubert, P., Ed. and M. Richardson, "Routing for RPL
(Routing Protocol for Low-Power and Lossy Networks)
Leaves", RFC 9010, DOI 10.17487/RFC9010, April 2021,
<https://www.rfc-editor.org/info/rfc9010>.
[RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
RFC 9030, DOI 10.17487/RFC9030, May 2021,
<https://www.rfc-editor.org/info/rfc9030>.
Appendix A. Example: Using ETX/RSSI Values to determine value Determine Value of S bit Bit
The combination of the downstream Received Signal Strength Indication(downstream) Indicator
(RSSI) and the upstream Expected Number of Transmissions(upstream) Transmission Count (ETX) has been
tested to determine whether a link is symmetric or asymmetric at
intermediate routers. We present two methods to obtain an ETX value
from RSSI measurement.
Method 1: In the first method, we constructed a table measuring RSSI
vs
versus ETX using the Cooja simulation [cooja] setup in the Contiki
OS
environment[contiki]. environment [contiki]. We used Contiki-2.7 running the
6LoWPAN/RPL protocol stack for the simulations. For approximating
the number of packet drops based on the RSSI values, we
implemented simple logic that drops transmitted packets with
certain pre-defined predefined ratios before handing over the packets to the
receiver. The packet drop ratio is implemented as a table lookup
of RSSI ranges mapping to different packet drop ratios with lower
RSSI ranges resulting in higher values. While this table has been
defined for the purpose of capturing the overall link behavior, in
general, it is highly recommended to conduct physical radio
measurement experiments, in
general. experiments. By keeping the receiving node at
different distances, we let the packets experience different
packet drops as per the described method. The ETX value
computation is done by another module which that is part of RPL
Objective Function implementation. Since the ETX value is
reflective of the extent of packet drops, it allowed us to prepare
a useful ETX vs versus RSSI table. ETX versus RSSI values obtained
in this way may be used as explained below:
Source -------> NodeA -------> NodeB -----> Destination
Figure 7: 6: Communication link 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 | 3840 |
+-------------------------+----------------------------------------+
+-------------------------+-----------------------+
Table 1: 3: Selection of S bit based Bit Based on Expected
ETX value Value
Method 2: One could also make use of the function
guess_etx_from_rssi() defined in the 6LoWPAN/RPL protocol stack of
Contiki-ng OS [Contiki-ng] to obtain RSSI-ETX mapping. This
function outputs an ETX value ranging between 128 and 3840 for -60
<= rssi <= -89. The function description is beyond the scope of
this document.
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 7) 6) are within, say, a 1:3
ratio. This ratio should be understood as determining the link's
symmetric/asymmetric nature. NodeA can typically know the ETX value
in the direction of NodeA -> NodeB 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 relationship, in turn turn, can be
used to estimate the ETX value at nodeA NodeA for link NodeB--->NodeA NodeB->NodeA from
the received RSSI from NodeB. Whenever nodeA NodeA determines that the
link towards the nodeB NodeB is bi-directional asymmetric bidirectional asymmetric, then the S bit is
set to 0. Afterwards, the link from NodeA to Destination remains
designated as asymmetric asymmetric, and the S bit remains set to 0.
Determination of asymmetry versus bidirectionality remains a topic of
lively discussion in the IETF.
Appendix B. Some Example AODV-RPL Message Flows
This appendix provides some example message flows showing RREQ and
RREP establishing symmetric and asymmetric routes. Also, examples
for the use of RREP_WAIT and G-RREP are included. In the examples,
router (O) is to be understood as performing the role of OrigNode.
Router (T) is to be understood as performing the role of TargNode.
Routers (R) are intermediate routers that are performing AODV-RPL
functions in order to discover one or more suitable routes between
(O) and (T).
B.1. Example control message flows Control Message Flows in symmetric Symmetric and asymmetric networks Asymmetric Networks
In the following diagram, RREQ messages are multicast from router (O)
in order to discover routes to and from router (T). The RREQ control
messages flow outward from (O). Each router along the way
establishes a single RREQ-Instance identified by RREQ-InstanceID even
if multiple RREQs are received with the same RREQ-InstanceID. In the
top half of the diagram, the routers are able to offer a symmetric
route at each hop of the path from (O) to (T). When (T) receives a
RREQ, it is then able to transmit data packets to (O). Router (T)
then prepares to send a RREP along the symmetric path that would
enable router (O) to send packets to router (T).
(R) ---RREQ(S=1)--->(R) ---RREQ(S=1)--->(R)
^ |
| |
RREQ(S=1) RREQ(S=1)
| |
| v
(O) --------->(R) --------->(R)-------->(T)
/ \ RREQ RREQ RREQ ^
| \ (S=1) (S=0) (S=0) |
| \ /
RREQ | \ RREQ (S=1) RREQ (S=0)
(S=0) | \ /
v \ RREQ (S=0) /
(R) ---->(R)------>(R)----.....--->(R)
Figure 8: 7: AODV-RPL RREQ message flow example when symmetric path
available Message Flow Example When Symmetric Path
Available
In the following diagram diagram, which results from the above RREQ message
transmission, a symmetric route is available from (T) to router (O)
via the routers in the top half of the diagram. RREP messages are
sent via unicast along the symmetric route. Since the RREP message
is transmitted via unicast, no RREP messages are sent by router (T)
to the routers in the bottom half of the diagram.
(R)<------RREP----- (R)<------RREP----- (R)
| ^
| |
RREP RREP
| |
v |
(O) ----------(R) ----------(R) --------(T)
/ \ |
| \ |
| \ (no RREP messages sent) /
| \ /
| \ /
| \ /
(R) -----(R)-------(R)----.....----(R)
Figure 9: 8: AODV-RPL RREP message flow example when symmetric path
available Message Flow Example When Symmetric Path
Available
In the following diagram, RREQ messages are multicast from router (O)
in order to discover routes to and from router (T) as before. As
shown, no symmetric route is available from (O) to (T).
(R) ---RREQ(S=0)--->(R) ---RREQ(S=0)--->(R)
^ |
| |
RREQ(S=1) RREQ(S=0)
| |
| v
(O) --------->(R) --------->(R)-------->(T)
^ \ RREQ RREQ RREQ | \
| \ (S=1) (S=0) (S=0) | |
| \ / |
| RREQ (S=1) RREQ (S=0) / (R)
| \ / |
| \ RREQ (S=0) / /
(R) ---->(R)------>(R)----.....----->(R)---
Figure 10: 9: AODV-RPL RREQ message flow when symmetric path unavailable Message Flow When Symmetric Path Unavailable
Upon receiving the RREQ in Figure 10, Router 9, router (T) then prepares to send
a RREP that would enable router (O) to send packets to router (T).
In Figure 10, 9, since no symmetric route is available from (T) to router
(O), RREP messages are sent via multicast to all neighboring routers.
(R)<------RREP----- (R)<------RREP----- (R)
| |
| |
RREP RREP
| |
| |
v v
(O)<--------- (R)<--------- (R)<------- (T)
^ \ RREP RREP RREP | \
| \ | |RREP
| \ / |
RREP | \ RREP RREP / (R)
| \ / |
| \ / /
(R)<----- (R)<----- (R)<---.....---- (R)< - RREP
RREP RREP RREP
Figure 11: 10: AODV-RPL RREQ and RREP Instances for Asymmetric Links
B.2. Example RREP_WAIT handling Handling
In Figure 12, 11, the first RREQ arrives at (T). This triggers TargNode
to start the RREP_WAIT_TIME timer.
(O) --------->(R) --------->(R)-------->(T)
RREQ RREQ RREQ
(S=1) (S=0) (S=0)
Figure 12: 11: TargNode starts Starts RREP_WAIT
In Figure 13, 12, another RREQ arrives before the RREP_WAIT_TIME timer is
expired. It could be preferable compared the previously received
RREP that caused the RREP_WAIT_TIME timer to be set.
(O) (T)
/ \ ^
| \ |
| \ /
RREQ | \ RREQ (S=1) RREQ (S=0)
(S=0) | \ /
v \ RREQ (S=0) /
(R) ---->(R)------>(R)----.....--->(R)
Figure 13: 12: Waiting TargNode receives preferable Receives Preferable RREQ
In Figure 14, 13, the RREP_WAIT_TIME timer expires. TargNode selects the
path with S=1.
(R) ---RREQ(S=1)--->(R) ---RREQ(S=1)--->(R)
^ |
| |
RREQ(S=1) RREQ(S=1)
| |
| v
(O) (T)
Figure 14: 13: RREP_WAIT expires Expires at TargNode
B.3. Example G-RREP handling Handling
In Figure 15, 14, R* has upward and downward routes to TargNode (T) that
satisfies
satisfy the OF of the RPL Instance originated by OrigNode (O) (O), and
the destination sequence number is at least as large as the sequence
number in the RREQ message.
(R) ---RREQ(S=1)--->(R) ---RREQ(S=0)--->(R)
^ |
| |
RREQ(S=1) RREQ(S=0)
| |
| v
(O) --------->(R) --------->(R)-------->(T)
/ \ RREQ RREQ RREQ ^
| \ (S=1) (S=0) (S=0) |
| \ /
RREQ | \ RREQ (S=1) /
(S=0) | \ /
v \ v
(R) ---->(R*)<------>(R)<----....--->(R)
Figure 15: 14: RREP triggers Triggers G-RREP at Intermediate Node
In Figure 16, 15, R* transmits the G-RREP DIO G-RREP-DIO back to OrigNode (O) and
forwards the incoming RREQ towards (T).
(O) (T)
\ ^
\ |
\ (RREQ) /
\ G-RREP DIO G-RREP-DIO /
\ /
\ (RREQ) (RREQ) /
(R*)------>(R)----....--->(R)
Figure 16: 15: Intermediate Node initiates Initiates G-RREP
11.
Acknowledgements
The authors thank Pascal Thubert, Rahul Jadhav, and Lijo Thomas for
their support and valuable inputs. input. The authors specially thank
Lavanya H.M H.M. for implementing AODV-RPl AODV-RPL in Contiki and conducting
extensive simulation studies.
The authors would like to acknowledge the review, feedback reviews, feedback, and
comments from the following people, in alphabetical order: Roman
Danyliw, Lars Eggert, Benjamin Kaduk, Tero Kivinen, Erik Kline,
Murray Kucherawy, Warren Kumari, Francesca Palombini, Alvaro Retana,
Ines Robles, John Scudder, Meral Shirazipour, Peter Van der Stok,
Eric
Éric Vyncke, and Robert Wilton.
Appendix D.
Contributors
Abdur Rashid Sangi
Wenzhou-Kean University
88 Daxue Rd, Ouhai,
Wenzhou, Ouhai
Wenzhou
Zhejiang Province
P.R. China Province, 325060
Kean University
1000 Morris Avenue
Union, New Jersey 07083
USA
United States of America
P.R. China
Email: sangi_bahrian@yahoo.com
Malati Hegde
Indian Institute of Science
Bangalore 560012
India
Email: malati@iisc.ac.in
Mingui Zhang
Huawei Technologies
No. 156 Beiqing Rd.
Haidian District
Beijing
100095
P.R. China
Email: zhangmingui@huawei.com
Authors' Addresses
Charles E. Perkins
Blue Meadow Networks
Saratoga, CA 95070
United States of America
Email: charliep@lupinlodge.com
S.V.R
S.V.R. Anand
Indian Institute of Science
Bangalore 560012
India
Email: anandsvr@iisc.ac.in
Satish Anamalamudi
SRM University-AP
Amaravati Campus
Amaravati, Andhra Pradesh 522 502
India
Email: satishnaidu80@gmail.com
Bing Liu
Huawei Technologies
No. 156 Beiqing Rd.
Haidian District
Beijing
100095
China
Email: remy.liubing@huawei.com