Mobile Ad hoc Networks Working Group C. Perkins
Internet-Draft Futurewei
Intended status: Standards Track S. Ratliff
Expires: September 8, 2015 Idirect
J. Dowdell
Airbus Defence and Space
L. Steenbrink
HAW Hamburg, Dept. Informatik
V. Mercieca
Airbus Defence and Space
March 7, 2015
Dynamic MANET On-demand (AODVv2) Routing
draft-ietf-manet-aodvv2-07
Abstract
The revised Ad Hoc On-demand Distance Vector (AODVv2) routing
protocol is intended for use by mobile routers in wireless, multihop
networks. AODVv2 determines unicast routes among AODVv2 routers
within the network in an on-demand fashion, offering rapid
convergence in dynamic topologies.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 8, 2015.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Data Elements and Notational Conventions . . . . . . . . . . 9
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 10
5. AODVv2 Message Transmission . . . . . . . . . . . . . . . . . 12
6. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Route Table Entry . . . . . . . . . . . . . . . . . . . . 12
6.2. Next-hop Router Adjacency Monitoring and Blacklists . . . 14
6.3. Router Clients and Client Networks . . . . . . . . . . . 16
6.4. Sequence Numbers . . . . . . . . . . . . . . . . . . . . 16
6.5. Table for Multicast RteMsgs . . . . . . . . . . . . . . . 17
7. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. The Cost() function . . . . . . . . . . . . . . . . . . . 19
7.2. The LoopFree() function . . . . . . . . . . . . . . . . . 19
7.3. Default Metric type . . . . . . . . . . . . . . . . . . . 19
7.4. Alternate Metrics . . . . . . . . . . . . . . . . . . . . 20
8. AODVv2 Protocol Operations . . . . . . . . . . . . . . . . . 20
8.1. Evaluating Incoming Routing Information . . . . . . . . . 20
8.2. Applying Route Updates To Route Table Entries . . . . . . 22
8.3. Route Maintenance . . . . . . . . . . . . . . . . . . . . 23
8.4. Route Table Entry Timeouts . . . . . . . . . . . . . . . 24
8.5. Route Discovery, Retries and Buffering . . . . . . . . . 24
8.6. Suppressing Redundant RteMsgs . . . . . . . . . . . . . . 26
9. AODVv2 Protocol Messages . . . . . . . . . . . . . . . . . . 27
9.1. RREQ Messages . . . . . . . . . . . . . . . . . . . . . . 27
9.1.1. RREQ Generation . . . . . . . . . . . . . . . . . . . 29
9.1.2. RREQ Reception . . . . . . . . . . . . . . . . . . . 30
9.1.3. RREQ Regeneration . . . . . . . . . . . . . . . . . . 31
9.2. RREP Messages . . . . . . . . . . . . . . . . . . . . . . 32
9.2.1. RREP Generation . . . . . . . . . . . . . . . . . . . 33
9.2.2. RREP Reception . . . . . . . . . . . . . . . . . . . 34
9.2.3. RREP Regeneration . . . . . . . . . . . . . . . . . . 35
9.3. RERR Messages . . . . . . . . . . . . . . . . . . . . . . 36
9.3.1. RERR Generation . . . . . . . . . . . . . . . . . . . 37
9.3.2. RERR Reception . . . . . . . . . . . . . . . . . . . 39
9.3.3. RERR Regeneration . . . . . . . . . . . . . . . . . . 40
9.4. RREP_Ack Messages . . . . . . . . . . . . . . . . . . . . 41
9.4.1. RREP_Ack Generation . . . . . . . . . . . . . . . . . 41
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9.4.2. RREP_Ack Reception . . . . . . . . . . . . . . . . . 42
10. Representing AODVv2 data elements using RFC 5444 . . . . . . 42
11. Simple Internet Attachment . . . . . . . . . . . . . . . . . 43
12. Optional Features . . . . . . . . . . . . . . . . . . . . . . 44
12.1. Expanding Rings Multicast . . . . . . . . . . . . . . . 45
12.2. Precursor Lists and Notifications . . . . . . . . . . . 45
12.2.1. Overview . . . . . . . . . . . . . . . . . . . . . . 45
12.2.2. Precursor Notification Details . . . . . . . . . . . 46
12.3. Multicast RREP Response to RREQ . . . . . . . . . . . . 46
12.4. Intermediate RREP . . . . . . . . . . . . . . . . . . . 47
12.5. Message Aggregation Delay . . . . . . . . . . . . . . . 47
13. Administratively Configurable Parameters and Timer Values . . 47
13.1. Timers . . . . . . . . . . . . . . . . . . . . . . . . . 47
13.2. Protocol Constants . . . . . . . . . . . . . . . . . . . 48
13.3. Administrative (functional) controls . . . . . . . . . . 49
13.4. Other administrative parameters and lists . . . . . . . 49
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50
14.1. AODVv2 Message Types Specification . . . . . . . . . . . 50
14.2. Message TLV Type Specification . . . . . . . . . . . . . 50
14.3. Address Block TLV Specification . . . . . . . . . . . . 51
14.4. MetricType Number Allocation . . . . . . . . . . . . . . 51
15. Security Considerations . . . . . . . . . . . . . . . . . . . 51
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 53
17.1. Normative References . . . . . . . . . . . . . . . . . . 53
17.2. Informative References . . . . . . . . . . . . . . . . . 54
Appendix A. Example Algorithms for AODVv2 Protocol Operations . 55
A.1. Subroutines for AODVv2 Operations . . . . . . . . . . . . 59
A.1.1. Process_Routing_Info . . . . . . . . . . . . . . . . 59
A.1.2. Fetch_Route_Table_Entry . . . . . . . . . . . . . . . 60
A.1.3. Update_Route_Table_Entry . . . . . . . . . . . . . . 61
A.1.4. Create_Route_Table_Entry . . . . . . . . . . . . . . 61
A.1.5. LoopFree . . . . . . . . . . . . . . . . . . . . . . 62
A.1.6. Fetch_Rte_Msg_Table_Entry . . . . . . . . . . . . . . 63
A.1.7. Update_Rte_Msg_Table . . . . . . . . . . . . . . . . 63
A.1.8. Build_RFC_5444_message_header . . . . . . . . . . . . 65
A.2. Example Algorithms for AODVv2 RREQ Operations . . . . . . 65
A.2.1. Generate_RREQ . . . . . . . . . . . . . . . . . . . . 65
A.2.2. Receive_RREQ . . . . . . . . . . . . . . . . . . . . 66
A.2.3. Regenerate_RREQ . . . . . . . . . . . . . . . . . . . 67
A.3. Example Algorithms for AODVv2 RREP Operations . . . . . . 69
A.3.1. Generate_RREP . . . . . . . . . . . . . . . . . . . . 69
A.3.2. Receive_RREP . . . . . . . . . . . . . . . . . . . . 70
A.3.3. Regenerate_RREP . . . . . . . . . . . . . . . . . . . 72
A.4. Example Algorithms for AODVv2 RERR Operations . . . . . . 73
A.4.1. Generate_RERR . . . . . . . . . . . . . . . . . . . . 74
A.4.2. Receive_RERR . . . . . . . . . . . . . . . . . . . . 75
A.4.3. Regenerate_RERR . . . . . . . . . . . . . . . . . . . 77
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A.5. Example Algorithms for AODVv2 RREP_Ack Operations . . . . 78
A.5.1. Generate_RREP_Ack . . . . . . . . . . . . . . . . . . 78
A.5.2. Receive_RREP_Ack . . . . . . . . . . . . . . . . . . 78
A.5.3. Timeout_RREP_Ack . . . . . . . . . . . . . . . . . . 78
Appendix B. Changes since revision ...-06.txt . . . . . . . . . 78
Appendix C. Changes between revisions 5 and 6 . . . . . . . . . 80
Appendix D. Changes from revision ...-04.txt . . . . . . . . . . 81
Appendix E. Changes from revision ...-03.txt . . . . . . . . . . 82
Appendix F. Changes from revision ...-02.txt . . . . . . . . . . 82
Appendix G. Features of IP needed by AODVv2 . . . . . . . . . . 83
Appendix H. Multi-homing Considerations . . . . . . . . . . . . 84
Appendix I. Shifting Network Prefix Advertisement Between AODVv2
Routers . . . . . . . . . . . . . . . . . . . . . . 84
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 84
1. Overview
The revised Ad Hoc On-demand Distance Vector (AODVv2) routing
protocol [formerly named DYMO] enables on-demand, multihop unicast
routing among AODVv2 routers in mobile ad hoc networks
[MANETs][RFC2501]. The basic operations of the AODVv2 protocol are
route discovery and route maintenance. Route discovery is performed
when an AODVv2 router must transmit a packet towards a destination
for which it does not have a route. Route maintenance is performed
to avoid prematurely expunging routes from the route table, and to
avoid dropping packets when a route breaks.
During route discovery, the originating AODVv2 router (RREQ_Gen)
multicasts a Route Request message (RREQ) to find a route toward some
target destination. Using a hop-by-hop regeneration algorithm, each
AODVv2 router receiving the RREQ message records a route toward the
originator. When the target's AODVv2 router (RREP_Gen) receives the
RREQ, it records a route toward RREQ_Gen and generates a Route Reply
(RREP) unicast toward RREQ_Gen. Each AODVv2 router that receives the
RREP stores a route toward the target, and again unicasts the RREP
toward the originator. When RREQ_Gen receives the RREP, routes have
then been established between RREQ_Gen (the originating AODVv2
router) and RREP_Gen (the target's AODVv2 router) in both directions.
Route maintenance consists of two operations. In order to maintain
routes, AODVv2 routers extend route lifetimes upon successfully
forwarding a packet. When a data packet is received to be forwarded
but there is no valid route for the destination, then the AODVv2
router of the source of the packet is notified via a Route Error
(RERR) message. Each upstream router that receives the RERR marks
the route as Invalid. Before such an upstream AODVv2 router could
forward a packet to the same destination, it would have to perform
route discovery again for that destination. RERR messages are also
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used to notify upstream routers when routes break (say, due to loss
of a link to a neighbor).
AODVv2 uses sequence numbers to assure loop freedom [Perkins99],
similarly to AODV. Sequence numbers enable AODVv2 routers to
determine the temporal order of AODVv2 route discovery messages,
thereby avoiding use of stale routing information.
See Section 10 for the mapping of AODVv2 data elements to RFC 5444
Address Block, Address TLV, and Message TLV formats. Security for
authentication of AODVv2 routers, and/or encryption of traffic is
dealt with by the underlying transport mechanism (e.g., by using the
techniques for Authentication, Integrity, and Confidentiality
documented in [RFC5444]).
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]. In addition, this document uses terminology from
[RFC5444], and defines the following terms:
Adjacency
A bi-directional relationship between neighboring AODVv2 routers
for the purpose of exchanging routing information. Not every pair
of neighboring routers will necessarily form an adjacency.
Monitoring of adjacencies where packets are being forwarded is
required (see Section 6.2).
AckReq
Request for acknowledgement (of an RREP message).
AODVv2 Router
An IP addressable device in the ad-hoc network that performs the
AODVv2 protocol operations specified in this document.
Current_Time
The current time as maintained by the AODVv2 router.
Data Element
A named object used within AODVv2 protocol messages
Disregard
Ignore for further processing.
Handling Router (HandlingRtr)
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HandlingRtr denotes the AODVv2 router receiving and handling an
AODVv2 message.
Invalid route
A route that cannot be used for forwarding.
MANET
A Mobile Ad Hoc Network as defined in [RFC2501].
MetricList
The metrics associated with the addresses in an AddressList.
Node
An IP addressable device in the ad-hoc network. A node may be an
AODVv2 router, or it may be a device in the network that does not
perform any AODVv2 protocol operations. All nodes in this
document are either AODVv2 Routers or else Router Clients.
OrigAddr
An IP address of the Originating Node used as a data element
within AODVv2 messages.
OrigAddrMetric
The metric associated with the route to OrigAddr.
OrigSeqNum
The Sequence Number maintained by OrigNode for OrigAddr.
Originating Node (OrigNode)
The Originating Node is the node that launched the application
requiring communication with the Target Address. If OrigNode is a
Router Client, its AODVv2 router (RREQ_Gen) has the responsibility
to generate a AODVv2 RREQ message on behalf of OrigNode as
necessary to discover a route.
PktSource
The source address of a packet sent to an unreachable address.
PrefixLengthList
The prefix lengths associated with addresses in an AddressList.
Reactive
A protocol operation is called "reactive" if it is performed only
in reaction to specific events. As used in this document,
"reactive" is synonymous with "on-demand".
Routable Unicast IP Address
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A routable unicast IP address is a unicast IP address that is
scoped sufficiently to be forwarded by a router. Globally-scoped
unicast IP addresses and Unique Local Addresses (ULAs).[RFC4193]
are examples of routable unicast IP addresses.
Route Error (RERR)
A RERR message is used to indicate that an AODVv2 router does not
have a route toward one or more particular destinations.
Route Reply (RREP)
A RREP message is used to establish a route between the Target
Address and the Originating Address, at all the AODVv2 routers
between them.
Route Request (RREQ)
An AODVv2 router uses a RREQ message to discover a valid route to
a particular destination address, called the Target Address. An
AODVv2 router processing a RREQ receives routing information for
the Originating Address.
Router Client
A node that requires the services of an AODVv2 router for route
discovery and maintenance. An AODVv2 router is always its own
client, so that its list of client IP addresses is never empty.
Router Interface
An interface supporting the transmission or reception of Router
Messages.
RREP Generating Router (RREP_Gen)
The RREP Generating Router is the AODVv2 router that serves
TargNode. RREP_Gen generates the RREP message to advertise a
route towards TargAddr from OrigAddr.
RREQ Generating Router (RREQ_Gen)
The RREQ Generating Router is the AODVv2 router that serves
OrigNode. RREQ_Gen generates the RREQ message to discover a route
for TargAddr.
Sequence Number (SeqNum)
A Sequence Number is an unsigned integer maintained by an AODVv2
router to avoid re-use of stale messages. The router associates
SeqNum with an IP address of one or more of its network
interfaces. The value zero (0) is reserved to indicate that the
Sequence Number for an address is unknown.
SeqNumList
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The list of Sequence Numbers associated with addresses in an
AddressList, used in RERR messages.
TargAddr
An IP address of the Target Node used as a data element within
AODVv2 messages.
TargAddrMetric
The metric associated with the route to TargAddr.
TargSeqNum
The Sequence Number maintained by TargNode for TargAddr.
Target Node (TargNode)
The node hosting the IP address towards which a route is needed.
Type-Length-Value structure (TLV)
A generic way to represent information, for example as used in
[RFC5444].
Unreachable Address
An address for which a valid route is not known.
upstream
In the direction from TargAddr to OrigAddr.
Valid route
A route that can be used for forwarding.
ValidityTime
The duration of time for which a route should be considered to be
a valid route.
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3. Data Elements and Notational Conventions
This document uses the Data Elements and conventions found in Table 1
and Table 2.
+--------------------+----------------------------------------------+
| Data Elements | Meaning |
+--------------------+----------------------------------------------+
| msg_hop_limit | Number of hops allowable for the message |
| msg_hop_count | Number of hops traversed so far by the |
| | message |
| AckReq | Acknowledgement Requested for RREP |
| MetricType | The metric type for values in MetricList |
| PktSource | Source address of a data packet |
| AddressList | A list of IP addresses |
| OrigAddr | IP address of the Originating Node |
| TargAddr | IP address of the Target Node |
| UnreachableAddress | An unreachable IP address |
| PrefixLengthList | Routing prefixes associated with addresses |
| | in AddressList |
| SeqNum | Sequence Number, used in RERR messages |
| SeqNumList | A list of SeqNums |
| OrigSeqNum | Originating Node Sequence Number |
| TargSeqNum | Target Node Sequence Number |
| MetricList | Metric values for routes to addresses in |
| | AddressList |
| OrigAddrMetric | Metric value for route to OrigAddr |
| TargAddrMetric | Metric value for route to TargAddr |
| ValidityTime | Included in ValidityTimeList |
| ValidityTimeList | ValidityTime values for routes to Addresses |
| | in AddressList |
+--------------------+----------------------------------------------+
Table 1
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+------------------------+------------------------------------------+
| Notation | Meaning |
+------------------------+------------------------------------------+
| Route[Address] | A route table entry towards Address |
| Route[Address].{field} | A field in such a route table entry |
| -- | -- |
| RREQ_Gen | AODVv2 router originating an RREQ |
| RREP_Gen | AODVv2 router responding to an RREQ |
| RERR_Gen | AODVv2 router originating an RERR |
| RteMsg | Either RREQ or RREP |
| RteMsg.{field} | Field in RREQ or RREP |
| AdvRte | A route advertised in an incoming RteMsg |
| HandlingRtr | Handling Router |
+------------------------+------------------------------------------+
Table 2
4. Applicability Statement
The AODVv2 routing protocol is a reactive routing protocol designed
for stub (i.e., non-transit) or disconnected (i.e., from the
Internet) mobile ad hoc networks (MANETs). AODVv2 handles a wide
variety of mobility patterns by determining routes on-demand. AODVv2
also handles a wide variety of traffic patterns. In networks with a
large number of routers, AODVv2 is best suited for relatively sparse
traffic scenarios where any particular router forwards packets to
only a small percentage of the AODVv2 routers in the network, due to
the on-demand nature of route discovery and route maintenance.
AODVv2 supports routers with multiple interfaces, as long as each
interface has its own (unicast routeable) IP address; the set of all
network interfaces supporting AODVv2 is administratively configured
in a list (namely, AODVv2_INTERFACES).
Ad Hoc networks have been deployed in many circumstances, including
for emergency and disaster relief. In those circumstances, it is
sometimes the case that the simple ability to communicate is much
more important than being assured of secure operations. AODVv2 is
very well suited for such reactive scenarios. For other ad hoc
networking applications, in which insecure operation could negate the
value of establishing communication paths, it is important for
neighboring AODVv2 nodes to establish security associations with one
another.
Although AODVv2 is closely related to AODV [RFC3561], and shares some
features of DSR [RFC4728], AODVv2 is not interoperable with either of
those other two protocols.
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AODVv2 is applicable to memory constrained devices, since only a
little routing state is maintained in each AODVv2 router. Routes
that are not needed for forwarding data do not have to be maintained,
in contrast to proactive routing protocols that require routing
information to all routers within the MANET be maintained.
In addition to routing for its own local applications, each AODVv2
router can also route on behalf of other non-routing nodes (in this
document, "Router Clients") that are directly reachable via its
network interfaces. Each AODVv2 router, if serving router clients
other than itself, SHOULD be configured with information about the IP
addresses of its clients, using any suitable method. In the initial
state, no AODVv2 router is required to have information about the
relationship between any other AODVv2 router and its Router Clients
(see Section 6.3).
The coordination among multiple AODVv2 routers to distribute routing
information correctly for a shared address (i.e. an address that is
advertised and can be reached via multiple AODVv2 routers) is not
described in this document. The AODVv2 router operation of shifting
responsibility for a routing client from one AODVv2 router to another
is described in Appendix I. Address assignment procedures are
entirely out of scope for AODVv2. A Router Client SHOULD NOT be
served by more than one AODVv2 router at any one time.
AODVv2 routers perform route discovery to find a route toward a
particular destination. AODVv2 routers MUST must be configured to
respond to RREQs for themselves and their clients. When AODVv2 is
the only protocol interacting with the forwarding table, AODVv2 MAY
be configured to perform route discovery for all unknown unicast
destinations.
By default, AODVv2 only supports bidirectional links. In the case of
possible unidirectional links, blacklists (see Section 6.2) SHOULD be
used, or other means (e.g. adjacency establishment with only
neighboring routers that have bidirectional communication as
indicated by NHDP [RFC6130]) of assuring and monitoring bi-
directionality are recommended. Otherwise, persistent packet loss or
persistent protocol failures could occur. If received over a link
that is unidirectional, metric information from incoming AODVv2
messages MUST NOT be used for route table updates.
The routing algorithm in AODVv2 may be operated at layers other than
the network layer, using layer-appropriate addresses. The routing
algorithm makes use of some persistent state; if there is no
persistent storage available for this state, recovery can impose a
performance penalty (e.g., in case of AODVv2 router reboots).
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5. AODVv2 Message Transmission
In its default mode of operation, AODVv2 sends messages using the
parameters for port number and IP protocol specified in [RFC5498].
Unless otherwise specified, the address for AODVv2 multicast messages
(for example, RREQ or RERR) is the link-local multicast address LL-
MANET-Routers [RFC5498]. All AODVv2 routers MUST subscribe to LL-
MANET-Routers [RFC5498] to receive AODVv2 messages. Implementations
are free to choose their own heuristics for reducing multicast
overhead. Some methods for doing so are described in [RFC6621].
AODVv2 does not specify which method should be used to restrict the
set of AODVv2 routers that have the responsibility to regenerate
multicast packets. Note that multicast packets MAY be sent via
unicast. For example, this may occur for certain link-types (non-
broadcast media), for manually configured router adjacencies, or in
order to improve robustness.
When multiple interfaces are available, a node transmitting a
multicast packet to LL-MANET-Routers MUST send the packet on all
interfaces that have been configured for AODVv2 operation.
Similarly, AODVv2 routers MUST subscribe to LL-MANET-Routers on all
their AODVv2 interfaces.
The IPv4 TTL (IPv6 Hop Limit) field for all packets containing AODVv2
messages is set to 255. If a packet is received with a value other
than 255, any AODVv2 message contained in the packet MUST be
disregarded by AODVv2. This mechanism, known as "The Generalized TTL
Security Mechanism" (GTSM) [RFC5082] helps to assure that packets
have not traversed any intermediate routers.
IP packets containing AODVv2 protocol messages SHOULD be given
priority queuing and channel access.
6. Data Structures
6.1. Route Table Entry
The route table entry is a conceptual data structure.
Implementations MAY use any internal representation so long as it
provides access to the information specified below.
A route table entry has the following fields:
Route.Address
An address or address prefix of a node
Route.PrefixLength
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The length of the address or prefix. If the value of
Route.PrefixLength is less than the length of Route.Address, the
route can be thought of as a route to the subnet on which
Route.Address resides. A PrefixLength is stored for every route
in the route table.
Route.SeqNum
The Sequence Number associated with Route.Address, as obtained
from the last packet that successfully updated this route table
entry.
Route.NextHop
The IP address of the adjacent AODVv2 router used for the path
toward the Route.Address
Route.NextHopInterface
The interface used to send packets toward Route.Address
Route.LastUsed
The time that this route was last used to forward a packet
Route.LastSeqNum
The time that the destination SeqNum for this route was last
updated
Route.ExpirationTime
The time at which this route must be marked as Invalid
Route.MetricType
The type of the metric for the route towards Route.Address
Route.Metric
The cost of the route towards Route.Address expressed in units
consistent with Route.MetricType
Route.State
The last *known* state (one of Active, Idle, or Invalid) of the
route
Route.Timed
TRUE if the route was specified to have a ValidityTime
Route.Precursors (optional)
A list of upstream neighbors using the route
A route table entry (i.e., a route) is in one of the following
states:
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Active
An Active route is in current use for forwarding packets. An
Active route is maintained continuously by AODVv2 and is
considered to remain active as long as it is used at least once
during every ACTIVE_INTERVAL, or if the Route.Timed flag is true.
When a route that is not a timed route is no longer active the
route becomes an Idle route.
Idle
An Idle route can be used for forwarding packets, even though it
is not in current use. If an Idle route is used to forward a
packet, it becomes an Active route once again. After an Idle
route remains idle for MAX_IDLETIME, it becomes an Invalid route.
Invalid
A route marked as Invalid cannot be used for forwarding, but the
sequence number information MAY be maintained until the
destination sequence number has not had any updates for
MAX_SEQNUM_LIFETIME; after that time, old sequence number
information may no longer be valid and the Invalid route MUST be
expunged.
MAX_SEQNUM_LIFETIME is the time after a reboot during which an AODVv2
router MUST NOT respond to any routing messages that require
information about its Sequence Number. Thus, if all other AODVv2
routers expunge routes to the rebooted router after that time
interval, the rebooted AODVv2 router's sequence number will not be
considered stale by any other AODVv2 router in the MANET.
The invalidation of a Timed route is controlled by the ExpirationTime
time of the route table entry (instead of MAX_IDLETIME). Until that
time, a Timed route can be used for forwarding packets. A route is
indicated to be a Timed route by the setting of the Timed flag in the
route table entry. Afterwards, the route MAY be expunged; otherwise
the route must be must be marked as Invalid.
6.2. Next-hop Router Adjacency Monitoring and Blacklists
Neighboring routers MAY form an adjacency based on AODVv2 messages,
other protocols (e.g. NDP [RFC4861] or NHDP [RFC6130]), or manual
configuration. Loss of a routing adjacency may also be indicated
similarly. AODVv2 routers SHOULD monitor connectivity to adjacent
routers along active routes. In the absence of other information
about bidirectional connectivity, the default approach for AODVv2
routers to monitor connectivity to neighboring AODVv2 routers is to
include the AckReq data element in RREP messages, and send RREP_Ack
messages to fulfill the requests (see Sections 9.2 and 9.4).
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However, when routers perform other operations such as those from the
list below, these can also be used as indications of connectivity.
o Neighborhood discovery [RFC6130], if that protocol is implemented
by its neighbors
o Route timeout
o Lower layer trigger that a link is broken
o TCP timeouts
o Promiscuous listening
o Other monitoring mechanisms or heuristics
For example, receipt of a Neighborhood Discovery message would signal
a connection to the sender. In this case, the AODVv2 router doesn't
need to request an acknowledgement in the RREP. Similarly, if AODVv2
received notification of a timeout, this may possibly be due to a
disconnection, and the AODVv2 router SHOULD attempt to verify
connectivity by including AckReq data element when sending a RREP to
that neighbor.
When a link to a neighbor is determined to be unidirectional, either
by failure to respond with a RREP_Ack as requested, or by some other
means, the neighbor MUST be placed in a blacklist. However, the
blacklisted neighbor SHOULD NOT be permanently blacklisted; after a
certain time (MAX_BLACKLIST_TIME), it SHOULD once again be considered
as a viable neighbor for route discovery operations.
For this purpose, a list of blacklisted routers along with their time
of removal SHOULD be maintained:
Blacklist.Router
An IP address of the router that did not verify bidirectional
connectivity.
Blacklist.RemoveTime
The time at which Blacklist.Router MAY be removed from the
blacklist.
RREQs received from a blacklisted router, or any router over a link
that is known to be incoming-only, MUST be disregarded.
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6.3. Router Clients and Client Networks
An AODVv2 router may offer routing services to other nodes that are
not AODVv2 routers; such nodes are called Router Clients in this
document.
For this purpose, CLIENT_ADDRESSES must be configured on each AODVv2
router with the following information:
Client IP address
The IP address of the node that requires routing service from the
AODVv2 router.
Client Prefix Length
The length of the routing prefix associated with the client IP
address.
The list of Routing Clients for an AODVv2 router is never empty,
since an AODVv2 router is always its own client as well. If the
Client Prefix Length is not the full length of the Client IP address,
then the prefix defines a Client Network. If an AODVv2 router is
configured to serve a Client Network, then the AODVv2 router MUST
serve every node that has an address within the range defined by the
routing prefix of the Client Network.
6.4. Sequence Numbers
Sequence Numbers allow AODVv2 routers to evaluate the freshness of
routing information. Each AODVv2 router in the network MUST maintain
its own sequence number (SeqNum). Each RREQ and RREP generated by an
AODVv2 router includes its SeqNum. Each AODVv2 router MUST ensure
that its SeqNum is monotonically increasing. The router can ensure
this by incrementing SeqNum whenever it generates RREQ or RREP .
A router receiving a RREQ or RREP message uses the Sequence Number in
the message to determine the freshness of a route update: if a new
Sequence Number in the message is lower than the one stored in the
route table, the stored information for that route is considered
stale.
As a consequence, loop freedom is assured.
If the router has multiple network interfaces, it can use the same
SeqNum for the IP addresses of all of them, or it can assign
different SeqNums for use with different IP addresses. However, the
router MUST NOT use multiple SeqNums for any particular IP address.
A Router Client has the same SeqNum as the IP address of the network
interface that the AODVv2 router uses to forward packets to that
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Router Client. Similarly, a route to a subnet has the same SeqNum as
the IP address of the network interface that the AODVv2 router uses
to forward packets to that subnet. The Sequence Number fulfills the
same role as the "Destination Sequence Number" of DSDV [Perkins94],
and as the AODV Sequence Number in RFC 3561[RFC3561].
An AODVv2 router increments its SeqNum as follows. Most of the time,
SeqNum is incremented by simply adding one (1). But when the SeqNum
has the value of the largest possible number representable as a
16-bit unsigned integer (i.e., 65,535), it MUST be incremented by
setting to one (1). In other words, the sequence number after 65,535
is 1.
An AODVv2 router SHOULD maintain its SeqNum in persistent storage.
If an AODVv2 router's SeqNum is lost, it MUST take the following
actions to avoid the danger of routing loops. First, the AODVv2
router MUST set Route.State := Invalid for each entry. Furthermore
the AODVv2 router MUST wait for at least MAX_SEQNUM_LIFETIME before
transmitting or regenerating any AODVv2 RREQ or RREP messages. If an
AODVv2 protocol message is received during this waiting period, the
AODVv2 router SHOULD perform normal route table entry updates, but
not forward the message to other nodes. If, during this waiting
period, a data packet is received to be forwarded to another
destination that is not among the router's Clients, then the AODVv2
router MUST transmit a RERR message indicating that no route is
available. However, packets destined to a Client are forwarded as
usual. At the end of the waiting period the AODVv2 router sets its
SeqNum to one (1) and begins performing AODVv2 protocol operations
again.
6.5. Table for Multicast RteMsgs
Two multicast RteMsgs (i.e., RREQ or RREP) are considered to be
"comparable" if they have the same Message Type, OrigAddr, TargAddr,
and MetricType. When RteMsgs are flooded in a MANET, an AODVv2
router may well receive such comparable RteMsgs from its neighbors.
A router, after receiving a RteMsg, MUST check against previous
RteMsgs to assure that its response message would contain information
that is not redundant. Otherwise, multicast RteMsgs are likely to be
regenerated repeatedly with almost no additional benefit, but
generating a great deal of unnecessary signaling traffic and
interference. See Section 8.6 regarding suppression of redundant
RteMsgs.
To avoid transmission of redundant RteMsgs, while still enabling the
proper handling of earlier RteMsgs that may have somehow been delayed
in the network, each AODVv2 router keeps a list of certain
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information about recently received RteMsgs. This list is called the
AODVv2 Multicast RteMsg Table -- or, more briefly, the RteMsg Table.
Each entry in the RteMsg Table has the following fields:
o Message Type (either RREQ or RREP)
o OrigAddr
o TargAddr
o OrigSeqNum (if present)
o TargSeqNum (if present)
o MetricType
o Timestamp (Current_Time at the time the entry is updated)
The RteMsg Table is maintained so that no two entries in the RteMsg
Table are comparable -- that is, all RteMsgs represented in the
RteMsg Table either have different Message Types, different OrigAddr,
different TargAddr, or different metric types. If two RteMsgs have
the same Message Type, MetricType, OrigAddr, and TargAddr, the
information from the one with the older Sequence Number is not needed
in the table; in case they have the same Sequence Number, the one
with the greater Metric value is not needed; in case they have the
same Metric as well, it does not matter which table entry is
maintained. Whenever a RteMsg Table entry is updated, its Timestamp
field MUST also set to be the Current_Time.
7. Metrics
Metrics measure a cost or quality associated to a route or a link.
They can account for various characteristics such as latency, delay,
financial, energy, etc. A metric value is included in each routing
table entry. Determining whether to use incoming information about a
route requires comparing metric values. Whenever an AODV router
receives metric information in an incoming message, the received
value of the metric is as measured by the neighbor router, and does
not reflect the cost of traversing the link to that neighbor.
Each metric has a MetricType, which is allocated by IANA as specified
in [RFC6551]. Apart from its default metric type as detailed in
Section 7.3, AODVv2 enables the use of monotonically increasing
metrics, whose data type depends on the metric used. Using non-
default metrics in a RteMsg requires the inclusion of the MetricType
data element. Routes are looked up according to metric type, and
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intermediate routers handling a RteMsg assign the same metric type to
all metric information in the RteMsg.
For each type of metric, a maximum value is defined, denoted
MAX_METRIC[i] where 'i' is the MetricType. AODVv2 cannot store
routes in its route table that cost more than MAX_METRIC[i].
7.1. The Cost() function
In order to simplify the description of storing accumulated route
costs in the route table, a Cost() function is defined. This
function returns the Cost of traversing a Route ('Cost(R)') or a Link
('Cost(L)'). Cost(L) for DEFAULT_METRIC_TYPE is specified in
Section 7.3. The Cost() function for other metrics is beyond the
scope of this document.
7.2. The LoopFree() function
Since determining loop freedom is known to depend on comparing the
Cost(R1) of advertised route update information to the Cost(R2) of an
existing stored route using the same metric type, AODVv2 invokes a
function called "LoopFree(R1, R2)". LoopFree(R1, R2) returns TRUE
when R1 is guaranteed to not rely on the route R2, i.e. R2 is not a
subroute of the route R1. An AODVv2 router invokes LoopFree() to
compare an advertised route to a stored route. The advertised route
is referred to as AdvRte and is used as parameter R1. The stored
route is referred to as Route and is used as parameter R2.
7.3. Default Metric type
The default MetricType (DEFAULT_METRIC_TYPE) is HopCount (but see
Section 7.4). HopCount is the only metric described in detail in
this document. For the HopCount metric, Cost(L) is always 1, and
Cost(R) is the hop count between the router and the destination.
MAX_METRIC[DEFAULT_METRIC_TYPE] is defined to be MAX_HOPCOUNT.
MAX_HOPCOUNT MUST be larger than the AODVv2 network diameter.
Otherwise, AODVv2 protocol messages may not reach their intended
destinations.
Using MetricType DEFAULT_METRIC_TYPE, LoopFree (AdvRte, Route) is
TRUE when Cost(AdvRte) <= Cost(Route). The specification of Cost(R)
and LoopFree(AdvRte, Route) for metric types other than
DEFAULT_METRIC_TYPE is beyond the scope of this document.
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7.4. Alternate Metrics
Some applications may require metric information other than HopCount,
which has traditionally been the default metric associated with
routes in MANET. It is well known that reliance on HopCount can
cause selection of the worst possible route in some situations. For
this reason, AODVv2 enables route selection based on metric
information other than HopCount -- in other words, based on
"alternate metrics".
The range and data type of each such alternate metric may be
different. For instance, the data type might be integers, or
floating point numbers, or restricted subsets thereof. It is out of
the scope of this document to specify for alternate metrics the
Cost(L) and Cost(R) functions, or their return type. Where necessary
these should take into account any differences in the link cost in
each direction.
8. AODVv2 Protocol Operations
In this section, operations are specified for updating the route
table using information within AODVv2 RteMsgs (either RREQ or RREP),
and due to timeouts. AdvRte is the route advertised by the RteMsg.
RteMsgs include IP addresses as well as possibly the SeqNum and the
prefix lengths associated with those IP addresses. The AdvRte also
includes the metric measured from the neighbor transmitting the
RteMsg to the IP address originating the route update. All SeqNum
comparisons use signed 16-bit arithmetic.
8.1. Evaluating Incoming Routing Information
After determining that the incoming information is correctly
formatted and contains values in the correct ranges, the AODVv2
router will use the information to update local routing information
if possible. This section explains how to determine whether the
incoming information should be used to update the route table, and
how to perform the update.
The incoming RteMsg may be a RREQ or a RREP. If it is a RREQ, it
contains information about a route to OrigAddr. Prefix length
information in a RREQ, if present, describes the subnet on which
OrigAddr resides. If it is a RREP, it contains information about a
route to TargAddr. AdvRte is used to denote the route information
contained in the RteMsg. AdvRte has the following properties:
o AdvRte.Address = OrigAddr (in RREQ) or TargAddr (in RREP).
o AdvRte.SeqNum = OrigSeqNum (in RREQ) or TargSeqNum (in RREP).
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o AdvRte.MetricType = RteMsg.MetricType, if present, else
DEFAULT_METRIC_TYPE.
o AdvRte.Metric = RteMsg.Metric.
o AdvRte.Cost = AdvRte.Metric + Cost(L) according to the indicated
MetricType, where L is the link from the advertising router.
o AdvRte.ValidityTime = ValidityTime in the RteMsg, if present.
In the description below, Route denotes the stored routing table
entry and HandlingRtr is the router receiving the RteMsg.
HandlingRtr MUST process the incoming information as follows. If the
routing table does not contain an entry matching AdvRte's Address and
MetricType, create a new route table entry according to the procedure
in Section 8.2. Otherwise determine whether or not to use AdvRte for
updating the route entry (Route) matching the AdvRte's Address and
MetricType as follows:
1. Check whether AdvRte is stale (AdvRte.SeqNum < Route.SeqNum).
* If AdvRte's sequence number is newer, HandlingRtr MUST use
AdvRte to update the Route.
* If stale, using the incoming information might result in a
routing loops. In this case the HandlingRtr MUST NOT use
AdvRte to update the Route.
* If the SeqNums are equal, continue checking as below.
2. Check whether AdvRte advertises a more costly route (AdvRte.Cost
>= Route.Metric).
* If the advertised route's cost is the same or greater than the
stored route, and the stored route is valid, the incoming
information does not offer any improvement and SHOULD NOT be
used to update the stored route table entry.
* If the advertised route's cost is lower than the stored route,
AdvRte offers improvement and SHOULD be used to update the
stored route table entry.
* If the advertised route's cost is the same or greater than the
stored route, but the stored route's state is Invalid,
continue processing to see whether there is a danger of a
routing loop.
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3. Check whether the information is safe against loops (LoopFree
(AdvRte, Route) == TRUE).
* If LoopFree (see Section 7.2) returns false, using the
incoming information might cause a routing loop. AdvRte MUST
NOT be used to update the stored route table entry.
4. If the advertised route can be used to update the route table
entry, follow the procedure in Section 8.2.
The above conditions about whether to use AdvRte for updating an
existing route table entry correspond to the following logic:
(AdvRte.SeqNum > Route.SeqNum) OR
((AdvRte.SeqNum == Route.SeqNum) AND
[((Route.State == Invalid) && LoopFree (AdvRte, Route)) OR
(AdvRte.Cost < Route.Metric) ])
To briefly summarize, AdvRte must satisfy the following conditions
compared to the existing route table entry before it can be used:
o AdvRte is more recent, (i.e., AdvRte.SeqNum > Route.SeqNum) OR
o AdvRte is not stale and can safely restore an invalid route (i.e.
LoopFree (AdvRte, Route) == TRUE), OR
o AdvRte is not stale and is less costly.
If the route has been updated based on information in a received
RREQ, the AODVv2 router MAY force regeneration of the RREQ, to ensure
the most recent information is propagated to other routers, but it
MAY suppress this to avoid extra control traffic.
8.2. Applying Route Updates To Route Table Entries
To apply the route update, a route table entry for AdvRte.Address is
either found to already exist in the route table, or else a new route
table entry for AdvRte.Address is created and inserted into the route
table. If the route table entry had to be created, or if the state
is Invalid, the state is set to be Idle. The fields of route table
entry are assigned as follows:
o If AdvRte.PrefixLength exists, then Route.PrefixLength :=
AdvRte.PrefixLength. Otherwise, Route.PrefixLength := maximum
length for address family (either 32 or 128).
o Route.SeqNum := AdvRte.SeqNum
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o Route.NextHop := IP.SourceAddress (i.e., the address from which
the RteMsg was received)
o Route.NextHopInterface is set to the interface on which RteMsg was
received
o Route.MetricType := AdvRte.MetricType
o Route.Metric := AdvRte.Cost
o Route.LastUsed := Current_Time
o Route.LastSeqnum := Current_Time
o If RteMsg.ValidityTime is included, then
Route.ExpirationTime := Current_Time + RteMsg.ValidityTime and
Route.Timed := TRUE. Otherwise, Route.Timed := FALSE and
Route.ExpirationTime := MAXTIME.
With these assignments to the route table entry, a route has been
made available, and the route can be used to send any buffered data
packets (and subsequently to forward any incoming data packets) for
Route.Address. An updated route entry also fulfills any outstanding
route discovery (RREQ) attempts for Route.Address. Any retry timers
for the RREQ SHOULD be cancelled.
8.3. Route Maintenance
AODVv2 routers attempt to maintain active routes. Before using a
route to forward a packet, an AODVv2 router MUST check the status of
the route as specified in Section 8.4. If the route has been marked
as Invalid, it cannot be used for forwarding. Otherwise, set
Route.LastUsed := Current_Time, Route.State := Active, and forward
the packet to the route's next hop. .
When a routing problem is encountered, an AODVv2 router (denoted
RERR_Gen) sends the RERR to quickly notify upstream routers. Two
kinds of routing problems can trigger generation of a RERR message.
The first happens when the router receives a packet but does not have
a valid route for the destination of the packet. The second case
happens immediately upon detection of a broken link (see Section 6.2)
for an valid route.
Optionally, if a precursor list is maintained for the route, see
Section 12.2 for precursor lifetime operations.
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8.4. Route Table Entry Timeouts
During normal operation, AODVv2 does not require any explicit
timeouts to manage the lifetime of a route. At any time, any route
table entry can be examined and then either expunged or marked as
Invalid according to the following rules.
The following rules are used to manage the state of route table
entries:
o If Current_Time > Route.ExpirationTime, set Route.State :=
Invalid.
o If (Current_Time - Route.LastUsed) > (ACTIVE_INTERVAL +
MAX_IDLETIME), and if (Route.Timed == FALSE), set Route.State :=
Invalid.
o If (Current_Time - Route.LastUsed) > ACTIVE_INTERVAL, and if
(Route.Timed == FALSE), set Route.State := Idle.
o If (Current_Time - Route.LastSeqNum > MAX_SEQNUM_LIFETIME), and
the route is Invalid, the route table entry MUST be expunged. If
the route is not invalid and MAX_SEQNUM_LIFETIME has expired, the
SeqNum information should be removed from the route, to avoid
problems with boot sequence and lost SeqNum behaviour.
Memory constrained devices MAY choose to expunge routes from the
AODVv2 route table at other times, but MUST adhere to the following
rules:
o An Active route MUST NOT be expunged.
o An Idle route SHOULD NOT be expunged.
o Any Invalid route MAY be expunged (least recently used first).
If precursor lists are maintained for the route (as described in
Section 12.2) then the precursor lists must also be expunged at the
same time that the route itself is expunged.
8.5. Route Discovery, Retries and Buffering
AODVv2 message types RREQ and RREP are together known as Routing
Messages (RteMsgs) and are used to discover a route between an
Originating and Target Address, denoted by OrigAddr and TargAddr.
The constructed route is bidirectional, enabling packets to flow
between OrigAddr and TargAddr. RREQ and RREP have similar
information and function, but have some differences in their rules
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for handling. When a node receives a RREQ or a RREP, the node then
creates or updates a route to the OrigAddr or the TargAddr
respectively (see Section 8.1). The main difference between the two
messages is that, by default, RREQ messages are multicast to solicit
a RREP, whereas RREP is unicast as a response to RREQ.
When an AODVv2 router needs to forward a data packet from a node
(with IP address OrigAddr) in its set of router clients, and it does
not have a forwarding route toward the packet's IP destination
address (TargAddr), the AODVv2 router (RREQ_Gen) generates a RREQ (as
described in Section 9.1.1) to discover a route toward TargAddr.
Subsequently RREQ_Gen awaits reception of an RREP message (see
Section 9.2.1) or other route table update (see Section 8.2) to
establish a route toward TargAddr. The RREQ message contains routing
information to enable RREQ recipients to route packets one hop
towards the OrigAddr, and the RREP message contains routing
information to enable RREP recipients to route packets one hop
towards the TargAddr.
After issuing a RREQ, as described above RREQ_Gen awaits a RREP
providing a bidirectional route toward the Target Address. If the
RREP is not received within RREQ_WAIT_TIME, RREQ_Gen MAY retry the
Route Discovery by generating another RREQ. Route Discovery SHOULD
be considered to have failed after DISCOVERY_ATTEMPTS_MAX and the
corresponding wait time for a RREP response to the final RREQ. After
the attempted Route Discovery has failed, RREQ_Gen MUST wait at least
RREQ_HOLDDOWN_TIME before attempting another Route Discovery to the
same destination.
To reduce congestion in a network, repeated attempts at route
discovery for a particular Target Address SHOULD utilize a binary
exponential backoff.
Data packets awaiting a route SHOULD be buffered by RREQ_Gen. This
buffer SHOULD have a fixed limited size (BUFFER_SIZE_PACKETS or
BUFFER_SIZE_BYTES). Determining which packets to discard first is a
matter of policy at each AODVv2 router; in the absence of policy
constraints, by default older data packets SHOULD be discarded first.
Buffering of data packets can have both positive and negative effects
(albeit usually positive). Nodes without sufficient memory available
for buffering SHOULD be configured to disable buffering by
configuring BUFFER_SIZE_PACKETS = 0 and BUFFER_SIZE_BYTES = 0. This
will affect the latency required for launching TCP applications to
new destinations.
If a route discovery attempt has failed (i.e., DISCOVERY_ATTEMPTS_MAX
attempts have been made without receiving a RREP) to find a route
toward the Target Address, any data packets buffered for the
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corresponding Target Address MUST BE dropped and a Destination
Unreachable ICMP message (Type 3) SHOULD be delivered to the source
of the data packet. The code for the ICMP message is 1 (Host
unreachable error). If RREQ_Gen is not the source (OrigNode), then
the ICMP is sent to OrigAddr.
8.6. Suppressing Redundant RteMsgs
When RREQ messages are flooded in a MANET, an AODVv2 router may
receive similar RREQ messages from more than one of its neighbours.
To avoid processing and transmission associated with redundant
RteMsgs, while still enabling proper handling of earlier RteMsgs that
may have somehow been delayed in the network, it is necessary for
each AODVv2 router store information about RteMsgs which it has
recently received (see the RteMsg table defined in Section 6.5).
When a RREQ is received, it is checked against the RteMsg Table to
see if it contains redundant information. If so it does not need to
be processed.
For RREQ messages, the process for comparison is as follows:
o Look for a "comparable" entry in the RteMsg Table with the same
MsgType, OrigAddr, TargAddr, and MetricType.
o If there is none, create an entry to store information about the
received RREQ, and continue to regenerate the RREQ.
o If there is an entry, and it has a lower SeqNum for OrigAddr than
the received RREQ, update it using the new RREQ and continue to
regenerate the RREQ.
o If there is an entry and it has a higher SeqNum for OrigAddr than
the received RREQ, do not replace the entry and do not process the
RREQ.
o If there is an entry and it has the same SeqNum for OrigAddr and a
higher Metric than the received RREQ, update it with the new RREQ
information.
o If there is an entry and it has the same SeqNum for OrigAddr and a
Metric less than or equal to the received RREQ, do not replace the
entry and do not regenerate the RREQ.
o In all cases, update the timestamp field, since other comparable
RREQs may still be traversing the network.
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The process of comparison for optional multicast RREP messages is
analogous, substituting RREP for RREQ, and TargAddr for OrigAddr.
Entries in the RteMsg Table MUST be deleted after
MAX_SEQNUM_LIFETIME, but should be maintained for at least
RteMsg_ENTRY_TIME in order to account for long-lived RREQs traversing
the network.
9. AODVv2 Protocol Messages
This section specifies the data elements and values required in
AODVv2 protocol messages, namely RREQ, RREP, RERR, and RREP_Ack.
To avoid congestion, each AODVv2 router's rate of packet/message
generation SHOULD be limited. The rate and algorithm for limiting
messages (CONTROL_TRAFFIC_LIMIT) is left to the implementor and
should be administratively configurable. AODVv2 messages SHOULD be
discarded in the following order of preference: RREQ, RREP, RERR, and
finally RREP_Ack.
See Section 10 for the mapping of AODVv2 data elements to RFC 5444
Message TLVs, Address Blocks, and Address TLVs.
9.1. RREQ Messages
RREQ messages are used in Route Discovery operations to request a
route to a specified Target address. RREQ messages have the
following general format:
+-----------------------------------------------------------------+
| msg_hop_limit, msg_hop_count |
+-----------------------------------------------------------------+
| MetricType (optional) |
+-----------------------------------------------------------------+
| AddressList := {OrigAddr, TargAddr} |
+-----------------------------------------------------------------+
| PrefixLengthList := {PrefixLength for OrigAddr, null}(optional) |
+-----------------------------------------------------------------+
| OrigSeqNum, (optional) TargSeqNum |
+-----------------------------------------------------------------+
| MetricList := {Metric for OrigAddr, null} |
+-----------------------------------------------------------------+
| ValidityTimeList := {ValidityTime for OrigAddr, null}(optional) |
+-----------------------------------------------------------------+
Figure 1: RREQ message structure
RREQ Data Elements
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msg_hop_limit
The remaining number of hops allowed for dissemination of the
RREQ message.
msg_hop_count
The number of hops already traversed during dissemination of
the RREQ message.
MetricType
If MetricType != DEFAULT_METRIC_TYPE, the MetricType element is
included and defines the MetricType associated with the entries
in the MetricList.
AddressList
AddressList contains OrigAddr and TargAddr.
PrefixLengthList
PrefixLengthList contains the length of the prefix for
OrigAddr, if OrigAddr resides on a Client Network with a prefix
length shorter than the number of bits of the address family
for OrigAddr.
OrigSeqNum
OrigSeqNum or TargSeqNum is REQUIRED and carries the
destination sequence number associated with OrigNode.
TargSeqNum
TargSeqNum is optional and carries a destination sequence
number associated with TargNode.
MetricList
The MetricList data element is REQUIRED, and carries the route
metric information associated with OrigAddr.
ValidityTimeList
The ValidityTimeList is optional and carries the length of time
that the sender is willing to offer a route towards OrigAddr.
RREQ messages carry information about OrigAddr and TargAddr, as
identified in the context of the RREQ_Gen. The OrigSeqNum MUST
appear. Both MAY appear in the same RREQ when SeqNum is available
for both OrigAddr and TargAddr.
The OrigSeqNum data element in a RteMsg MUST apply only to OrigAddr.
The other address in the AddressList is TargAddr.
If the TargSeqNum data element appears, then it MUST apply only to
TargAddr. The other address in the AddressList is OrigAddr.
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9.1.1. RREQ Generation
Upon receiving an IP packet from one of its Router Clients, it often
happens that an AODVv2 router has no valid route to the destination.
In this case the AODVv2 router is responsible for generating a RREQ
and associated data elements on behalf of its client OrigNode. The
router is referred to as RREQ_Gen. Before creating a RREQ, RREQ_Gen
should check if an RREQ has recently been sent for this destination
and a response is awaited, or if the limit of AODVv2 RREQ retries has
been reached.
In constructing the RREQ, RREQ_Gen uses AddressList, OrigSeqNum,
MetricList, and optionally MetricType, PrefixLengthList, TargSeqNum,
and ValidityTime.
RREQ_Gen follows the steps in this section. OrigAddr MUST be a
unicast address. The order of data elements is illustrated
schematically in Figure 1. RREQ_Gen SHOULD include TargSeqNum, if a
previous value of the TargAddr's SeqNum is known (e.g. from an
invalid route table entry using longest-prefix matching). If
TargSeqNum is not included, AODVv2 routers handling the RREQ assume
that RREQ_Gen does not have that information.
1. Set msg_hop_limit to MAX_HOPCOUNT.
2. Set msg_hop_count to zero, if including it.
3. Include the MetricType data element if requesting a route for a
non-default metric type.
4. Set AddressList := {OrigAddr, TargAddr}.
5. For the PrefixLengthList:
* If OrigAddr resides on a subnet of Router Clients, set
PrefixLengthList := { OrigAddr subnet's prefix, null }.
* Otherwise, the PrefixLengthList is omitted.
6. For the Sequence Number List:
* Increment the SeqNum as specified in Section 6.4.
* Set OrigSeqNum to the new value of SeqNum.
* If an Invalid route exists matching TargAddr using longest
prefix matching, include TargSeqNum and set it to the sequence
number on the Invalid route. Otherwise omit TargSeqNum.
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7. Set MetricList := { Route[OrigAddr].Metric, null }.
8. If the RREQ_Gen wishes to limit the time that the route to
OrigAddr may be used, include the ValidityTime data element.
9.1.2. RREQ Reception
Upon receiving an RREQ, an AODVv2 router performs the following
steps.
1. A router MUST handle RREQs only from neighbors. RREQs from nodes
that are not neighbors MUST be disregarded.
2. Check whether the sender is on the blacklist of AODVv2 routers
(see Section 6.2). If not, continue processing. Otherwise,
check the Blacklist Remove Time.
* If Current_Time < Remove Time, ignore this RREQ for further
processing.
* If Current_Time >= Remove Time, remove the Blacklist entry and
continue processing.
3. Verify that the message contains the required data elements:
msg_hop_limit, OrigAddr, TargAddr, OrigSeqNum, OrigAddrMetric,
and verify that OrigAddr and TargAddr are valid addresses
(routable and unicast). If not, ignore this message for further
processing.
4. If the MetricType data element is present, check that the
MetricType is known.
* If not, ignore this RREQ for further processing.
* Otherwise continue processing .
5. Verify that OrigAddrMetric <= {MAX_METRIC[MetricType] -
Cost(Link)}.
* If not, ignore this RREQ for further processing.
* Otherwise continue processing .
6. Process the route to OrigAddr as specified in Section 8.1.
7. Check if the message is a duplicate or redundant by comparing to
entries in the RteMsg table as described in Section 8.6.
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* If duplicate or redundant, ignore this RREQ for further
processing.
* Otherwise save the information in the RteMsg table to identify
future duplicates and continue processing.
8. Check if the TargAddr belongs to one of the Router Clients.
* If so, generate a RREP as specified in Section 9.2.1.
* Otherwise, continue to RREQ regeneration.
9.1.3. RREQ Regeneration
Unless the router is prepared to advertise the new route, it halts
processing. By sending a RREQ, a router advertises that it will
forward packets to the OrigAddr contained in the RREQ according to
the information enclosed. The router MAY choose not to regenerate
the RREQ, though this could decrease connectivity in the network or
result in non-optimal paths.
The circumstances under which a router MAY choose not to regenerate a
RREQ are not specified in this document. Some examples may include
the router being heavily loaded and not advertising routing for more
traffic, or being low on energy and having to reduce energy expended
for sending AODVv2 messages or packet forwarding.
The procedure for RREQ regeneration is as follows:
1. Check the msg_hop_limit.
* If it is zero, do not regenerate.
* Otherwise, decrement the value by one.
2. Check if msg_hop_count is present and greater than or equal to
MAX_HOPCOUNT
* If so, do not regenerate.
* Otherwise, increment msg_hop_count by one.
3. Change OrigAddrMetric to match the route table entry for
OrigAddr, which should match the advertised value in the received
RREQ plus the cost of the link to the router which forwarded the
RREQ.
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4. If the incoming RREQ contains a ValidityTimeList, it MUST be
copied into the regenerated RREQ. If not present, and the
regenerating router wishes to limit the time that its route to
OrigAddr may be used, set ValidityTimeList := {ValidityTime for
OrigAddr, null}.
If the received RREQ was unicast, the regenerated RREQ can be unicast
to the next hop address of the route towards TargAddr, if known.
Otherwise, the RREQ SHOULD be multicast to the LL-MANET-Routers IP
and MAC address [RFC5498], [RFC4291].
9.2. RREP Messages
RREP messages are used to offer a route to a target address, and are
sent in response to a RREQ message. RREP messages have the following
general format:
+-----------------------------------------------------------------+
| msg_hop_limit, msg_hop_count |
+-----------------------------------------------------------------+
| AckReq (optional), MetricType (optional) |
+-----------------------------------------------------------------+
| AddressList := {OrigAddr,TargAddr} |
+-----------------------------------------------------------------+
| PrefixLengthList := {null, PrefixLength for TargAddr(optional)} |
+-----------------------------------------------------------------+
| TargSeqNum |
+-----------------------------------------------------------------+
| MetricList := {null, metric for TargAddr} |
+-----------------------------------------------------------------+
| ValidityTimeList := {null, ValidityTime for TargAddr}(optional) |
+-----------------------------------------------------------------+
Figure 2: RREP message structure
RREP Data Elements
msg_hop_limit
The remaining number of hops allowed for dissemination of the
RREP message.
msg_hop_count
The number of hops already traversed during dissemination of
the RREP message.
AckReq
Acknowledgement Requested by sender (optional).
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MetricType
If MetricType != DEFAULT_METRIC_TYPE, the MetricType associated
with route to TargAddr.
AddressList
AddressList contains OrigAddr and TargAddr.
PrefixLengthList
PrefixLengthList contains the length of the prefix for
TargAddr, if TargAddr resides on a Client Network with a prefix
length shorter than the number of bits of the address family
for TargAddr.
TargSeqNum
TargSeqNum is REQUIRED and carries the destination sequence
number associated with TargNode.
MetricList
The MetricList data element is REQUIRED, and carries the route
metric information associated with TargAddr.
ValidityTimeList
The ValidityTimeList is optional and carries the length of time
that the sender is willing to offer a route towards TargAddr.
RREP messages carry information about OrigAddr and TargAddr, as known
in the context of the RREP_Gen. The TargSeqNum MUST appear. It MUST
apply only to TargAddr. The other address in the AddressList is
OrigAddr.
9.2.1. RREP Generation
This section specifies the generation of an RREP by an AODVv2 router
(RREP_Gen) that provides connectivity for TargAddr, thus enabling the
establishment of a route between OrigAddr and TargAddr. In
constructing the RREP, AODVv2 uses AddressList, TargSeqNumber List,
MetricList, and optionally AckReq, MetricType, PrefixLengthList and/
or ValidityTimeList. These elements are then used to create a
RFC5444 message; see Section 10 for details.
The AckReq data element indicates that an acknowledgement to the RREP
has been requested. If no corresponding RREP_Ack is received within
the RREP_Ack_SENT_TIMEOUT, the next hop is added to the blacklist as
discussed in Section 6.2.
The procedure for RREP generation is as follows:
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1. Set msg_hop_limit to the msg_hop_count from the received RREQ
message.
2. Set msg_hop_count, if including it, to zero.
3. Include the AckReq data element if RREP_Ack is requested from the
next hop (as described in Section 6.2).
4. If MetricType is not DEFAULT_METRIC_TYPE, include the MetricType
data element and set the type accordingly.
5. Set the Address List := {OrigAddr, TargAddr}.
6. For the PrefixLengthList:
* If TargAddr resides on a subnet of Router Clients, set
PrefixLengthList := {null, TargAddr subnet's prefix}.
* Otherwise, no PrefixLengthList is needed.
7. For the TargSeqNum:
* RREP_Gen increments its SeqNum as specified in Section 6.4.
* Set TargSeqNum := the new value of SeqNum.
8. Set MetricList := { null, Route[TargAddr].Metric }.
9. If the RREP_Gen wishes to limit the time that the route to
TargAddr may be used, set ValidityTimeList := {null, TargAddr
ValidityTime}.
By default, the RREP is sent by unicast to the IP address of the next
hop of the RREP_Gen's route to OrigAddr.
9.2.2. RREP Reception
Upon receiving an RREP, an AODVv2 router performs the following
steps.
1. A router MUST handle RREPs only from neighbors. RREPs from nodes
that are not neighbors MUST be disregarded.
2. Verify that the RREP message contains the required data elements:
msg_hop_limit, OrigAddr, TargAddr, TargAddrMetric, TargSeqNum,
and verify that OrigAddr and TargAddr are valid addresses
(routable and unicast). If not, ignore this RREP message for
further processing.
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3. If the MetricType data element is present, check that the
MetricType is known.
* If not, ignore this RREP for further processing.
* Otherwise continue processing .
4. Verify that TargAddrMetric <= {MAX_METRIC[MetricType] -
Cost(Link)}.
* If not, ignore this RREP for further processing.
* Otherwise continue processing .
5. Process the route to TargAddr as specified in Section 8.1.
6. If the AckReq data element is present, send a RREP_Ack as
specified in Section 9.4.
7. Check if the message is a duplicate or redundant by comparing to
entries in the RREP table as described in Section 8.6.
* If duplicate or redundant, ignore this RREP for further
processing.
* Otherwise save the information in the RREP table to identify
future duplicates and continue processing.
8. Check if the OrigAddr belongs to one of the Router Clients.
* If so, the RREP satisfies a previously sent RREQ. Processing
is complete and data can now be forwarded along the route.
Any packets from OrigAddr that were buffered for later
delivery SHOULD be transmitted.
* Otherwise, continue to RREP regeneration.
9.2.3. RREP Regeneration
Similar to rules for RREQ regeneration, unless the router is prepared
to advertise the route to TargAddr, it halts processing. By
forwarding a RREP, a router advertises that it will forward packets
to the TargAddr contained in the RREP according to the information
enclosed. The router MAY choose not to regenerate the RREP, for the
same reasons as mentioned under RREQ regeneration Section 9.1.3,
though this could decrease connectivity in the network or result in
non-optimal paths.
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If no valid route exists to OrigAddr, a RERR SHOULD be transmitted to
TargAddr as specified in Section 9.3.1 and the RREP should not be
regenerated.
The procedure for RREP regeneration is as follows:
1. Check the msg_hop_limit.
* If it is zero, do not regenerate.
* Otherwise, decrement the value by one.
2. If msg_hop_count is present, then:
* If msg_hop_count >= MAX_HOPCOUNT, do not regenerate.
* Otherwise, increment msg_hop_count by one.
3. The RREP SHOULD be unicast to the next hop on the route to
OrigAddr. If no valid route exists to OrigAddr, a RERR SHOULD be
transmitted to TargAddr as specified in Section 9.3.1.
4. Change TargAddrMetric to match the route table entry for
TargAddr, which should match the advertised value in the received
RREP plus the cost of the link to the router which forwarded the
RREP.
5. Include the AckReq data element if this device requires
acknowledgement of the RREP message.
6. If the incoming RREP contains a ValidityTimeList, it MUST be
copied into the regenerated RREP. If not present, and the
regenerating router wishes to limit the time that its route to
TargAddr may be used, set ValidityTimeList := {null, ValidityTime
for TargAddr}.
The RREP SHOULD be unicast to the next hop on the route to OrigAddr.
9.3. RERR Messages
An RERR message is generated by a AODVv2 router (i.e., RERR_Gen) in
order to notify upstream routers that packets cannot be delivered to
one or more destinations. An RERR message has the following general
structure:
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+-----------------------------------------------------------------+
| msg_hop_limit |
+-----------------------------------------------------------------+
| PktSource (optional), MetricType (optional) |
+-----------------------------------------------------------------+
| RERR AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList for UnreachableAddresses (optional) |
+-----------------------------------------------------------------+
| SeqNumList (one entry per address) |
+-----------------------------------------------------------------+
Figure 3: RERR message structure
RERR Data Elements
msg_hop_limit
The remaining number of hops allowed for dissemination of the
RERR message.
PktSource
The IP address of the unreachable destination triggering RERR
generation. If this RERR message was triggered by a broken
link, the PktSource data element is not required.
MetricType
If MetricType != DEFAULT_METRIC_TYPE, the MetricType associated
with routes affected by a broken link.
RERR AddressList
A list of IP addresses not reachable by the AODVv2 router
transmitting the RERR.
PrefixLengthList
PrefixLengthList contains the prefix lengths associated with
the addresses in the RERR AddressList, if any of them reside on
a Client Network with a prefix length shorter than the number
of bits of their address family.
SeqNumList
The list of sequence numbers associated with the
UnreachableAddresses in the RERR AddressList.
9.3.1. RERR Generation
There are two types of events which trigger generation of a RERR
message. The first is the arrival of a packet for which there is no
route to the destination address. This can be a packet forwarded by
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the routing process, or a RREP when there is no route to OrigAddr.
In this case, exactly one UnreachableAddress will be included in
RERR's AddressList (either the Destination Address of the IP header
from a data packet, or the OrigAddr found in the AddressList of an
RREP message). RERR_Gen MUST discard the packet or message that
triggered generation of the RERR.
The second type of event happens when a link breaks. All routes
(whether valid or not) that use the broken link MUST be marked as
Invalid. If the broken link was not used by any Active route, no
RERR message is generated. Every Invalid route reported in the RERR
MUST have the same MetricType. If the broken link affects routes to
destinations that have different MetricTypes, multiple RERR messages
must be generated.
If an AODVv2 router receives an ICMP packet to or from the address of
one of its client nodes, it simply forwards the ICMP packet, and does
not generate any RERR message.
In constructing the RERR, AODVv2 uses MetricType, AddressList,
SeqNumList, MetricList, and in some cases PktSource and
PrefixLengthList. These elements are then used to create a RFC5444
message; see Section 10 for details.
The procedure for RERR generation is as follows:
1. Set msg_hop_limit to MAX_HOPCOUNT.
2. If the RERR was triggered by an Undeliverable Packet, the
PktSource data element MUST be included, containing the source IP
address of the Undeliverable Packet.
3. Include the MetricType data element if reporting a Invalid route
for a non-default metric type.
4. For the RERR AddressList:
* If the RERR was triggered by an undeliverable packet, insert
the destination IP address of the undeliverable packet, or if
the packet was a RREP, insert the OrigAddr.
* If the RERR was triggered by a broken link, include the
addresses of all previously Active routes which are now
Invalid, up to the limit imposed by the MTU (interface
"Maximum Transfer Unit") of the physical medium. If there are
too many such previously Active routes, additional RERR
messages should be constructed and transmitted to contain the
remaining addresses. If the configuration option
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ENABLE_IDLE_IN_RERR is enabled, include any previously Idle
routes which are now Invalid, as long as the packet size of
the RERR does not exceed the MTU.
5. If there are destinations reported in the RERR AddressList that
have associated subnet prefixes in the route table, insert those
prefixes in the PrefixLengthList; otherwise, omit the
PrefixLengthList.
6. If known, the sequence numbers associated with the routes to the
addresses in the RERR AddressList SHOULD be included in the
SeqNumList; otherwise, omit the SeqNumList.
If the RERR is sent in response to an Undeliverable Packet:
o It SHOULD be sent unicast to the next hop towards the source IP
address of the packet which triggered the RERR.
o Otherwise the RERR MUST be sent to the multicast IP and MAC
address for LL-MANET-Routers.
If the RERR is sent in response to a broken link:
o If precursor lists are maintained for the addresses in the RERR
AddressList (see Section 12.2), the RERR SHOULD be unicast to the
precursors.
o Otherwise the RERR MUST be sent to the multicast IP and MAC
address for LL-MANET-Routers.
9.3.2. RERR Reception
Upon receiving an RERR, the following steps are performed.
1. If the message does not contain the msg_hop_limit and at least
one UnreachableAddress, do not process the RERR.
2. If the MetricType data element is present, check that the
MetricType is known.
* If not, ignore this RERR for further processing.
* Otherwise continue processing .
3. For each UnreachableAddress,
* Check that the address is valid (routable and unicast).
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* Check that there is a valid route with the same MetricType
matching the address using longest prefix matching.
* Check that the route's next hop is the sender of the RERR.
* Check that the route's next hop interface is the interface on
which the RERR was received.
* Check that the Unreachable Address SeqNum is either unknown,
or is greater than the route's SeqNum.
* If any of the above are false, the UnreachableAddress does not
need to be advertised in a regenerated RERR.
* If all of the above are true:
+ If the route's prefix length is the same as the
UnreachableAddress's prefix length, set the route state to
Invalid.
+ If the prefix length is shorter than the original route,
the route MUST be expunged from the routing table, since it
is a sub-route of the larger route which is reported to be
Invalid.
+ If the prefix length is different, create a new route with
the UnreachableAddress and its prefix, and set the state to
Invalid.
If there are no UnreachableAddresses which need to be advertised in a
regenerated RERR, take no further action.
Otherwise regenerate the RERR as specified in Section 9.3.3.
9.3.3. RERR Regeneration
The procedure for RERR regeneration is as follows:
1. Check the msg_hop_limit.
* If it is zero, do not regenerate.
* Otherwise, decrement the value by one.
2. If the PktSource data element was included in the original RERR,
copy it into the regenerated RERR.
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3. If the MetricType data element was included in the original RERR
copy it into the regenerated RERR.
4. For the RERR AddressList, include all UnreachableAddresses which
have been determined to need regeneration.
5. For the PrefixLengthList, insert the prefix lengths associated
with the addresses in the RERR AddressList.
6. For the SeqNumList, include the sequence numbers corresponding to
the addresses in the RERR AddressList.
If the original RERR contained the PktSource data element, and a
route exists to the source address, the regenerated RERR MUST be sent
unicast to the next hop of the route towards PktSource.
Otherwise, if precursor lists are maintained, the regenerated RERR
SHOULD be sent to the active precursors of the Invalid routes as
specified in Section 12.2.
Otherwise the regenerated RERR MUST be sent to the multicast IP and
MAC address for LL-MANET-Routers.
9.4. RREP_Ack Messages
RREP_Ack is modeled on the RREP_Ack message type from AODV [RFC3561].
RREP_Ack messages have the following general format:
+-----------------------------------------------------------------+
| msg_hop_limit := 1 |
+-----------------------------------------------------------------+
Figure 4: RREP_Ack message structure
RREP_Ack Data Elements
msg_hop_limit
The remaining number of hops allowed for dissemination of the
RREP_Ack message.
9.4.1. RREP_Ack Generation
This section specifies the generation of an RREP_Ack by an AODVv2
router. The procedure is as follows:
1. Set msg_hop_limit := 1.
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The RREP_Ack is sent by unicast to the IP address of router that
inserted a AckReq data element into a RREP message.
9.4.2. RREP_Ack Reception
Upon receiving an RREP_Ack, an AODVv2 router performs the following
steps.
1. A router MUST handle RREP_Acks only from neighbors. RREP_Acks
from nodes that are not neighbors MUST be disregarded.
2. The router checks whether the sender's IP address is in the
blacklist. If so, the IP address is deleted from the blacklist.
3. The router checks whether an RREP_Ack message was expected from
the sending IP address. If so, the router records that the
required RREP_Ack has been received and cancels the associated
timeout.
10. Representing AODVv2 data elements using RFC 5444
AODVv2 specifies that all control plane messages between Routers
SHOULD use the Generalised Mobile Ad-hoc Network Packet and Message
Format [RFC5444], which provides a multiplexed transport for multiple
protocols. AODVv2 therefore specifies Route Messages comprising data
elements that map to message elements in RFC5444 but, in line with
the concept of use, does not specify which order the messages should
be arranged in an RFC5444 packet. An implementation of an RFC5444
parser may choose to optimise the content of certain message elements
to reduce control plane overhead. For handling of messages that
contain unknown TLV types, the parser SHOULD ignore the information
for processing, but preserve it unmodified for forwarding.
Here is a brief summary of the RFC 5444 format.
A packet formatted according to RFC 5444 contains zero or more
messages.
A message contains a message header, message TLV block, and zero
or more address blocks.
Each address block MAY also have one or more associated TLV
blocks; each TLV block MAY encode multiple TLVs. Each TLV value
in an Address TLV block is associated with exactly one of the
addresses in the address block.
The following table shows how AODVv2 data elements are represented in
RFC 5444 messages.
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+------------------------+------------------------------------------+
| Data Element | RFC 5444 Message Representation |
+------------------------+------------------------------------------+
| msg_hop_limit | RFC 5444 Message Header <msg-hop-limit> |
| msg_hop_count | RFC 5444 Message Header <msg-hop-count> |
| AckReq | Acknowledgement Request Message TLV |
| MetricType | The Metric Type Message TLV |
| PktSource | The Packet Source Message TLV |
| RteMsg AddressList | RFC 5444 Address Block |
| - OrigAddr | |
| - TargAddr | |
| - PrefixLengthList | |
| RERR AddressList | RFC 5444 Address Block |
| - UnreachableAddress | |
| - PrefixLengthList | |
| SeqNumList | Sequence Number Address Block TLV |
| - SeqNum | |
| OrigSeqNum | Originating Node Sequence Number Address |
| | Block TLV |
| TargSeqNum | Target Node Sequence Number Address |
| | Block TLV |
| MetricList | Metric Address Block TLV |
| - OrigAddrMetric | - corresponds to OrigAddr |
| - TargAddrMetric | - corresponds to TargAddr |
| ValidityTimeList | VALIDITY_TIME Address Block TLV |
| - ValidityTime | |
+------------------------+------------------------------------------+
Table 3
If a packet contains only a single AODVv2 message and no packet TLVs,
it need only include a minimal Packet-Header [RFC5444]. The length
of an address (32 bits for IPv4 and 128 bits for IPv6) inside an
AODVv2 message is indicated by the msg-addr-length (MAL) in the msg-
header. Although the addresses in an Address Block may appear in any
order, each TLV value in a TLV Block is associated with exactly one
Address in the Address Block. So, for instance, the ordering of the
OrigAddrMetric and TargAddrMetric values in the MetricList is
determined by the order of OrigAddr and TargAddr in the preceding
RteMsg Address List. See Section 14.2 for more information about
AODVv2 Message TLVs. See Section 14.3 for more information about
AODVv2 Address Block TLVs.
11. Simple Internet Attachment
Simple Internet attachment means attachment of a stub (i.e., non-
transit) network of AODVv2 routers to the Internet via a single
Internet AODVv2 router (called IAR).
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As in any Internet-attached network, AODVv2 routers, and their
clients, wishing to be reachable from hosts on the Internet MUST have
IP addresses within the IAR's routable and topologically correct
prefix (e.g. 191.0.2.0/24).
/-------------------------\
/ +----------------+ \
/ | AODVv2 Router | \
| | 191.0.2.2/32 | |
| +----------------+ | Routable
| +-----+--------+ Prefix
| | Internet | /191.0.2/24
| | AODVv2 Router| /
| | 191.0.2.1 |/ /---------------\
| | serving net +------+ Internet \
| | 191.0.2/24 | \ /
| +-----+--------+ \---------------/
| +----------------+ |
| | AODVv2 Router | |
| | 191.0.2.3/32 | |
\ +----------------+ /
\ /
\-------------------------/
Figure 5: Simple Internet Attachment Example
When an AODVv2 router within the AODVv2 MANET wants to discover a
route toward a node on the Internet, it uses the normal AODVv2 route
discovery for that IP Destination Address. The IAR MUST respond to
RREQ on behalf of all Internet destinations.
When a packet from a node on the Internet destined for a node in the
AODVv2 MANET reaches the IAR, if the IAR does not have a route toward
that destination it will perform normal AODVv2 route discovery for
that destination.
12. Optional Features
Some optional features of AODVv2, associated with AODV, are not
required by minimal implementations. These features are expected to
apply in networks with greater mobility, or larger node populations,
or requiring reduced latency for application launches. The optional
features are as follows:
o Expanding Rings Multicast
o Precursor lists.
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o Multicast RREP Response to RREQ
o Intermediate RREPs (iRREPs): Without iRREP, only the destination
can respond to a RREQ.
o Reporting Multiple UnreachableAddresses: a RERR message can carry
more than one Unreachable Address for cases when a single link
breakage causes other destinations to become unreachable from an
intermediate router.
o Message Aggregation Delay.
12.1. Expanding Rings Multicast
For multicast RREQ, msg_hop_limit MAY be set in accordance with an
expanding ring search as described in [RFC3561] to limit the RREQ
propagation to a subset of the local network and possibly reduce
route discovery overhead.
12.2. Precursor Lists and Notifications
This section specifies an interoperable enhancement to AODVv2 (and
possibly other reactive routing protocols) enabling more economical
RERR notifications to traffic sources upon determination that a route
needed to forward such traffic to its destination has become Invalid.
12.2.1. Overview
In many circumstances, there can be several sources of traffic for a
certain destination. Each such source of traffic is known as a
"precursor" for the destination, as well as all upstream routers
between the forwarding AODVv2 router and the traffic source. There
is no need to keep track of upstream routers any farther away than
the next hop. For each destination, an AODVv2 router MAY choose to
keep track of the upstream neighbors that have provided traffic for
that destination.
Moreover, any particular link to an adjacent AODVv2 router may be a
path component of multiple routes towards various destinations. The
precursors for all destinations using the next hop across any link
are collectively known as the precursors for that next hop.
When an AODVv2 router marks a route as Invalid, the precursors of the
Invalid route should be notified (using RERR) about the change in
status of their route to the destination of that Invalid route.
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12.2.2. Precursor Notification Details
During normal operation, each AODVv2 router wishing to maintain
precursor lists as described above, maintains a precursor table and
updates the table whenever the node forwards traffic to one of the
destinations in its route table. For each precursor in the precursor
list, a record must be maintained to indicate whether the precursor
has been used for recent traffic (in other words, whether the
precursor is an Active precursor). So, when traffic arrives from a
precursor, the Current_Time is used to mark the time of last use for
the precursor list element associated with that precursor.
When an AODVv2 router detects that a link is broken, then for each
Active precursor using that next hop, the node MAY notify the
precursor using either unicast or multicast RERR:
unicast RERR to each Active precursor
This option is applicable when there are few Active precursors
compared to the number of neighboring AODVv2 routers.
multicast RERR to RERR_PRECURSORS
RERR_PRECURSORS is, by default, LL-MANET-Routers [RFC5498]. This
option is typically preferable when there are many precursors,
since fewer packet transmissions are required.
Each neighbor receiving the RERR MAY then execute the same procedure
until all upstream routers have received the RERR notification.
12.3. Multicast RREP Response to RREQ
The RREQ Target Router (RREP_Gen) MAY, as an alternative to
unicasting a RREP, be configured to use multicast to distribute
routing information about the route toward TargAddr. RREP_Gen does
this as described in Section 9.2.1, but multicasting the RREP to LL-
MANET-Routers [RFC5498]. Routers receiving the multicast RREP must
perform RteMsg suppression (see Section 8.6).
Broadcast RREP response to incoming RREQ was originally specified to
handle unidirectional links, but it is expensive. Due to the
significant overhead, AODVv2 routers MUST NOT use multicast RREP
unless configured to do so by setting the administrative parameter
USE_MULTICAST_RREP. This technique can be used to find the best
return path rather than follow the same path as the RREQ took.
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12.4. Intermediate RREP
This specification has been published as a separate Internet Draft
[I-D.perkins-irrep].
12.5. Message Aggregation Delay
The aggregation of multiple messages into a packet is specified in
RFC 5444 [RFC5444].
Implementations MAY choose to briefly delay transmission of messages
for the purpose of aggregation (into a single packet) or to improve
performance by using jitter [RFC5148].
13. Administratively Configurable Parameters and Timer Values
AODVv2 uses various configurable parameters of various types:
o Timers
o Protocol constants
o Administrative (functional) controls
o Other administrative parameters and lists
The tables in the following sections show the parameters along their
definitions and default values (if any).
Note: several fields have limited size (bits or bytes). These sizes
and their encoding may place specific limitations on the values that
can be set. For example, <msg-hop-count> is a 8-bit field and
therefore MAX_HOPCOUNT cannot be larger than 255.
13.1. Timers
AODVv2 requires certain timing information to be associated with
route table entries. The default values are as follows:
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+------------------------+---------------+
| Name | Default Value |
+------------------------+---------------+
| ACTIVE_INTERVAL | 5 second |
| MAX_IDLETIME | 200 seconds |
| MAX_BLACKLIST_TIME | 200 seconds |
| MAX_SEQNUM_LIFETIME | 300 seconds |
| RteMsg_ENTRY_TIME | 12 seconds |
| RREQ_WAIT_TIME | 2 seconds |
| RREP_Ack_SENT_TIMEOUT | 1 second |
| RREQ_HOLDDOWN_TIME | 10 seconds |
+------------------------+---------------+
Table 4: Timing Parameter Values
The above timing parameter values have worked well for small and
medium well-connected networks with moderate topology changes. The
timing parameters SHOULD be administratively configurable for the
network where AODVv2 is used. Ideally, for networks with frequent
topology changes the AODVv2 parameters should be adjusted using
either experimentally determined values or dynamic adaptation. For
example, in networks with infrequent topology changes MAX_IDLETIME
may be set to a much larger value.
13.2. Protocol Constants
AODVv2 protocol constants typically do not require changes. The
following table lists these constants, along with their values and a
reference to the specification describing their use.
+------------------------+-----------------+------------------------+
| Name | Default Value | Description |
+------------------------+-----------------+------------------------+
| DISCOVERY_ATTEMPTS_MAX | 3 | Section 8.5 |
| MAX_HOPCOUNT | 20 hops | Section 7 |
| MAX_METRIC[i] | Specified only | Section 7 |
| | for HopCount | |
| MAXTIME | [TBD] | Maximum expressible |
| | | clock time Section 8.4 |
+------------------------+-----------------+------------------------+
Table 5: Parameter Values
These values MUST have the same values for all AODVv2 routers in the
ad hoc network. If the configured values are different, the
following consequences may be observed:
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o DISCOVERY_ATTEMPTS_MAX: some nodes are likely to be more
successful at finding routes, but at the cost of additional
control traffic for unsuccessful attempts.
o MAX_HOPCOUNT: If some nodes use a value that is too small, they
would not be able to discover routes to distant addresses.
o MAX_METRIC[DEFAULT_METRIC_TYPE]: MUST always be the maximum
expressible metric of type DEFAULT_METRIC_TYPE. No
interoperability problems due to variations on different nodes,
but if a lesser value is used, route comparisons may exhibit
overly restrictive behavior.
o MAXTIME: Variations on different nodes would not cause problems
for interoperability. If a lesser value is used, route state
management may exhibit overly restrictive behavior.
13.3. Administrative (functional) controls
The following administrative controls may be used to change the
operation of the network, by enabling optional behaviors. These
options are not required for correct routing behavior, although they
may potentially reduce AODVv2 protocol messaging in certain
situations. The default behavior is typically to NOT enable the
options. Inconsistent settings at different nodes in the network
will not result in protocol errors. In the case of inconsistent
settings for DEFAULT_METRIC_TYPE, inconsistent setting might result
in messages specifying metric types unknown to some nodes and
consequent poor performance.
+------------------------+------------------------------------+
| Name | Description |
+------------------------+------------------------------------+
| DEFAULT_METRIC_TYPE | 3 (i.e, Hop Count (see [RFC6551])) |
| ENABLE_IDLE_IN_RERR | Section 9.3.1 |
| ENABLE_IRREP | Section 9.1.1 |
| USE_MULTICAST_RREP | Section 12.3 |
+------------------------+------------------------------------+
Table 6: Administratively Configured Controls
13.4. Other administrative parameters and lists
The following table lists contains AODVv2 parameters which should be
administratively configured for each node.
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+-----------------------+-----------------------+-----------------+
| Name | Default Value | Cross Reference |
+-----------------------+-----------------------+-----------------+
| AODVv2_INTERFACES | | Section 4 |
| BUFFER_SIZE_PACKETS | 2 | Section 8.5 |
| BUFFER_SIZE_BYTES | MAX_PACKET_SIZE [TBD] | Section 8.5 |
| CLIENT_ADDRESSES | AODVv2_INTERFACES | Section 6.3 |
| CONTROL_TRAFFIC_LIMIT | TBD [50 packets/sec?] | Section 9 |
+-----------------------+-----------------------+-----------------+
Table 7: Other Administrative Parameters
14. IANA Considerations
This section specifies several RFC 5444 message types, message tlv-
types, and address tlv-types. Also, a new registry of 16-bit
alternate metric types is specified.
14.1. AODVv2 Message Types Specification
+----------------------------------------+----------+
| Name of AODVv2 Message | Type |
+----------------------------------------+----------+
| Route Request (RREQ) | 10 (TBD) |
| Route Reply (RREP) | 11 (TBD) |
| Route Error (RERR) | 12 (TBD) |
| Route Reply Acknowledgement (RREP_Ack) | 13 (TBD) |
+----------------------------------------+----------+
Table 8: AODVv2 Message Types
14.2. Message TLV Type Specification
+-----------------------------+----------+----------+---------------+
| Name of Message TLV | Type | Length | Cross |
| | | (octets) | Reference |
+-----------------------------+----------+----------+---------------+
| AckReq (Acknowledgment | 10 (TBD) | 0 | Section 6.2 |
| Request) | | | |
| PktSource (Packet Source) | 11 (TBD) | 4 or 16 | Section 9.3.1 |
| MetricType | 12 (TBD) | 1 | Section 9.3 |
+-----------------------------+----------+----------+---------------+
Table 9: Message TLV Types
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14.3. Address Block TLV Specification
+----------------------------+-----------+------------+-------------+
| Name of Address Block TLV | Type | Length | Value |
+----------------------------+-----------+------------+-------------+
| Metric | 10 (TBD) | depends on | Section 9.1 |
| | | MetricType | |
| Sequence Number (SeqNum) | 11 (TBD) | 2 octets | Section 9.1 |
| Originating Node Sequence | 12 (TBD) | 2 octets | Section 9.1 |
| Number (OrigSeqNum) | | | |
| Target Node Sequence | 13 (TBD) | 2 octets | Section 9.1 |
| Number (TargSeqNum) | | | |
| VALIDITY_TIME | 1 | 1 octet | [RFC5497] |
+----------------------------+-----------+------------+-------------+
Table 10: Address Block TLV (AddrTLV) Types
14.4. MetricType Number Allocation
Metric types are identified according to the assignments as specified
in [RFC6551]. The metric type of the Hop Count metric is assigned to
be 3, in order to maintain compatibility with that existing table of
values from RFC 6551.
+-----------------------+----------+-------------+
| Name of MetricType | Type | Metric Size |
+-----------------------+----------+-------------+
| Unallocated | 0 -- 2 | TBD |
| Hop Count | 3 - TBD | 1 octet |
| Unallocated | 4 -- 254 | TBD |
| Reserved | 255 | Undefined |
+-----------------------+----------+-------------+
Table 11: Metric Types
15. Security Considerations
The objective of the AODVv2 protocol is for each router to
communicate reachability information about addresses for which it is
responsible. Positive routing information (i.e. a route exists) is
distributed via RREQ and RREP messages. Negative routing information
(i.e. a route does not exist) is distributed via RERRs. AODVv2
routers store the information contained in these messages in order to
properly forward data packets, and they generally provide this
information to other AODVv2 routers.
This section does not mandate any specific security measures.
Instead, this section describes various security considerations and
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potential avenues to secure AODVv2 routing. Security for
authentication of AODVv2 routers, and/or encryption of traffic is
dealt with by the underlying transport mechanism (e.g., by using the
techniques for Authentication, Integrity, and Confidentiality
documented in [RFC5444]). The most important security mechanisms for
AODVv2 routing are integrity/authentication and confidentiality.
In situations where routing information or router identity are
suspect, integrity and authentication techniques SHOULD be applied to
AODVv2 messages. In these situations, routing information that is
distributed over multiple hops SHOULD also verify the integrity and
identity of information based on originator of the routing
information.
A digital signature could be used to identify the source of AODVv2
messages and information, along with its authenticity. A nonce or
timestamp SHOULD also be used to protect against replay attacks. S/
MIME and OpenPGP are two authentication/integrity protocols that
could be adapted for this purpose.
In situations where confidentiality of AODVv2 messages is important,
cryptographic techniques can be applied.
In certain situations, for example sending a RREP or RERR, an AODVv2
router could include proof that it has previously received valid
routing information to reach the destination, at one point of time in
the past. In situations where routers are suspected of transmitting
maliciously erroneous information, the original routing information
along with its security credentials SHOULD be included.
Note that if multicast is used, any confidentiality and integrity
algorithms used MUST permit multiple receivers to handle the message.
Routing protocols, however, are prime targets for impersonation
attacks. In networks where the node membership is not known, it is
difficult to determine the occurrence of impersonation attacks, and
security prevention techniques are difficult at best. However, when
the network membership is known and there is a danger of such
attacks, AODVv2 messages must be protected by the use of
authentication techniques, such as those involving generation of
unforgeable and cryptographically strong message digests or digital
signatures. While AODVv2 does not place restrictions on the
authentication mechanism used for this purpose, IPsec Authentication
Message (AH) is an appropriate choice for cases where the nodes share
an appropriate security association that enables the use of AH.
In particular, routing messages SHOULD be authenticated to avoid
creation of spurious routes to a destination. Otherwise, an attacker
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could masquerade as that destination and maliciously deny service to
the destination and/or maliciously inspect and consume traffic
intended for delivery to the destination. RERR messages SHOULD be
authenticated in order to prevent malicious nodes from disrupting
routes between communicating nodes.
If the mobile nodes in the ad hoc network have pre-established
security associations, the purposes for which the security
associations are created should include that of authorizing the
processing of AODVv2 control packets. Given this understanding, the
mobile nodes should be able to use the same authentication mechanisms
based on their IP addresses as they would have used otherwise.
Most AODVv2 messages are transmitted to the multicast address LL-
MANET-Routers [RFC5498]. It is therefore required for security that
AODVv2 neighbors exchange security information that can be used to
insert an ICV [RFC6621] into the AODVv2 message block [RFC5444].
This enables hop-by-hop security. For destination-only RREP
discovery procedures, AODVv2 routers that share a security
association SHOULD use the appropriate mechanisms as specified in RFC
6621. The establishment of these security associations is out of
scope for this document.
16. Acknowledgments
AODVv2 is a descendant of the design of previous MANET on-demand
protocols, especially AODV [RFC3561] and DSR [RFC4728]. Changes to
previous MANET on-demand protocols stem from research and
implementation experiences. Thanks to Elizabeth Belding and Ian
Chakeres for their long time authorship of AODV. Additional thanks
to Derek Atkins, Emmanuel Baccelli, Abdussalam Baryun, Ramon Caceres,
Thomas Clausen, Christopher Dearlove, Ulrich Herberg, Henner Jakob,
Luke Klein-Berndt, Lars Kristensen, Tronje Krop, Koojana Kuladinithi,
Kedar Namjoshi, Alexandru Petrescu, Henning Rogge, Fransisco Ros,
Pedro Ruiz, Christoph Sommer, Lotte Steenbrink, Romain Thouvenin,
Richard Trefler, Jiazi Yi, Seung Yi, and Cong Yuan, for their reviews
AODVv2 and DYMO, as well as numerous specification suggestions.
17. References
17.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
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[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized Mobile Ad Hoc Network (MANET) Packet/Message
Format", RFC 5444, February 2009.
[RFC5497] Clausen, T. and C. Dearlove, "Representing Multi-Value
Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497, March
2009.
[RFC5498] Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network
(MANET) Protocols", RFC 5498, March 2009.
[RFC6551] Vasseur, JP., Kim, M., Pister, K., Dejean, N., and D.
Barthel, "Routing Metrics Used for Path Calculation in
Low-Power and Lossy Networks", RFC 6551, March 2012.
17.2. Informative References
[I-D.perkins-irrep]
Perkins, C. and I. Chakeres, "Intermediate RREP for
dynamic MANET On-demand (AODVv2) Routing", draft-perkins-
irrep-02 (work in progress), November 2012.
[Perkins94]
Perkins, C. and P. Bhagwat, "Highly Dynamic Destination-
Sequenced Distance-Vector Routing (DSDV) for Mobile
Computers", Proceedings of the ACM SIGCOMM '94 Conference
on Communications Architectures, Protocols and
Applications, London, UK, pp. 234-244, August 1994.
[Perkins99]
Perkins, C. and E. Royer, "Ad hoc On-Demand Distance
Vector (AODV) Routing", Proceedings of the 2nd IEEE
Workshop on Mobile Computing Systems and Applications, New
Orleans, LA, pp. 90-100, February 1999.
[RFC2501] Corson, M. and J. Macker, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, January 1999.
[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
Demand Distance Vector (AODV) Routing", RFC 3561, July
2003.
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[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
[RFC4728] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
Routing Protocol (DSR) for Mobile Ad Hoc Networks for
IPv4", RFC 4728, February 2007.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
Considerations in Mobile Ad Hoc Networks (MANETs)", RFC
5148, February 2008.
[RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
RFC 6130, April 2011.
[RFC6621] Macker, J., "Simplified Multicast Forwarding", RFC 6621,
May 2012.
Appendix A. Example Algorithms for AODVv2 Protocol Operations
The following subsections show example algorithms for protocol
operations required by AODVv2, including RREQ, RREP, RERR, and
RREP_Ack.
Processing for RREQ, RREP, and RERR messages follows the following
general outline:
1. Receive incoming message.
2. Update route table as appropriate.
3. Respond as needed, often regenerating the incoming message with
updated information.
Once the route table has been updated, the information contained
there is known to be the most recent available information for any
fields in the outgoing message. For this reason, the algorithms are
written as if outgoing message field values are assigned from the
route table information, even though it is often equally appropriate
to use fields from the incoming message.
AODVv2_algorithms:
o Process_Routing_Info
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o Fetch_Route_Table_Entry
o Update_Route_Table_Entry
o Create_Route_Table_Entry
o LoopFree
o
o Update_Rte_Msg_Table
o
o Generate_RREQ
o Receive_RREQ
o Regenerate_RREQ
o
o Generate_RREP
o Receive_RREP
o Regenerate_RREP
o
o Generate_RERR
o Receive_RERR
o Regenerate_RERR
o
o Generate_RREP_Ack
o Receive_RREP_Ack
o Timeout RREP_Ack
The following lists indicate the meaning of the field names used in
subsequent sections to describe message processing for the above
algorithms.
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RteMsg parameters, where rteMsg can be inRREQ, outRREQ, inRREP or
outRREP:
rteMsg.hopLimit
rteMsg.hopCount
rteMsg.ackReq (RREP only, optional)
rteMsg.metricType (optional)
rteMsg.origAddr
rteMsg.targAddr
rteMsg.origPrefixLen (optional)
rteMsg.targPrefixLen (optional)
rteMsg.origSeqNum (RREQ only)
rteMsg.targSeqNum (optional in RREQ)
rteMsg.origAddrMetric (RREQ only)
rteMsg.targAddrMetric (RREP only)
rteMsg.validityTime
rteMsg.nbrIP
AdvRte has the following properties as described in Section 8.1:
AdvRte.Address = OrigAddr (in a RREQ) or TargAddr (in a RREP)
AdvRte.PrefixLength = PrefixLength for OrigAddr (in a RREQ) or
TargAddr (in a RREP), or if not present, the maximum address
length for the address family of AdvRte.Address
AdvRte.SeqNum = SeqNum for OrigAddr (in a RREQ) or for TargAddr
(in a RREP)
AdvRte.MetricType = RteMsg.MetricType, if present, else
DEFAULT_METRIC_TYPE
AdvRte.Metric = RteMsg.Metric
AdvRte.Cost = AdvRte.Metric + Cost(L) according to the indicated
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MetricType, where L is the link from the advertising router
AdvRte.ValidityTime = ValidityTime in the RteMsg, if present
AdvRte.NextHopIP = IP source of the RteMsg
AdvRte.NextHopIntf = interface the RteMsg was received on
AdvRte.HopCount = value from RteMsg header
AdvRte.HopLimit = value from RteMsg header
AdvRte.AckReq = true/false whether present in RteMsg (optional in
RREP)
A route table entry has properties as described in Section 6.1:
Route.Address
Route.PrefixLength
Route.SeqNum
Route.NextHop
Route.NextHopInterface
Route.LastUsed
Route.LastSeqNum
Route.ExpirationTime
Route.MetricType
Route.Metric
Route.State
Route.Timed
Route.Precursors (optional)
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A.1. Subroutines for AODVv2 Operations
A.1.1. Process_Routing_Info
/* Compare incoming route information to stored route, maybe use
linkMetric: either Cost(inRREQ.netif) or (inRREP.netif) */
Process_Routing_Info (advRte)
{
rte := Fetch_Route_Table_Entry (advRte);
if (rte exists)
{
rte := Create_Route_Table_Entry(advRte);
return rte;
}
if (!LoopFree(advRte, rte))
{ /* incoming route cannot be guaranteed loop free */
return null;
}
/* rule from 8.1 */
if (
(AdvRte.SeqNum > Route.SeqNum) /* stored route is stale */
OR
((AdvRte.SeqNum == Route.SeqNum) /* same SeqNum */
AND
[((Route.State == Invalid)) /* advRte can repair stored */
OR
(AdvRte.Cost < Route.Metric)])) /* advRte is better */
{
Update_Route_Table_Entry (rte, advRte);
}
return rte;
}
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A.1.2. Fetch_Route_Table_Entry
/* lookup a route table entry matching an advertised route */
Fetch_Route_Table_Entry (advRte)
{
foreach (rteTableEntry in rteTable)
{
if (rteTableEntry.Address == advRte.Address AND
rteTableEntry.MetricType == advRte.MetricType)
return rteTableEntry;
}
return null;
}
/* lookup a route table entry matching address and metric type */
Fetch_Route_Table_Entry (destination, metricType)
{
foreach (rteTableEntry in rteTable)
{
if (rteTableEntry.Address == destination AND
rteTableEntry.MetricType == MetricType)
return rteTableEntry;
}
return null;
}
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A.1.3. Update_Route_Table_Entry
/* update a route table entry using AdvRte in received RteMsg */
Update_Route_Table_Entry (rte, advRte);
{
rte.SeqNum := advRte.SeqNum;
rte.NextHop := advRte.NextHopIp;
rte.NextHopInterface := advRte.NextHopIntf;
rte.LastUsed := Current_Time;
rte.LastSeqNum := Current_Time;
if (validityTime)
{
rte.ExpirationTime := Current_Time + advRte.validityTime;
rte.Timed := true;
}
else
{
rte.Timed := false;
rte.ExpirationTime := MAXTIME;
}
rte.Metric := advRte.Cost;
if (rte.State == Invalid)
rte.State := Idle;
}
A.1.4. Create_Route_Table_Entry
/* Create a route table entry from address and prefix length */
Create_Route_Table_Entry (address, prefixLength,
seqNum, metricType)
{
rte := allocate_memory();
rte.Address := address;
rte.PrefixLength := prefixLength;
rte.SeqNum := seqNum;
rte.MetricType := metricType;
}
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/* Create a route table entry from the advertised route */
Create_Route_Table_Entry(advRte)
{
rte := allocate_memory();
rte.Address := advRte.Address;
if (advRte.PrefixLength)
rte.PrefixLength := advRte.PrefixLength;
else
rte.PrefixLength := maxPrefixLenForAddressFamily;
rte.SeqNum := advRte.SeqNum;
rte.NextHop := advRte.NextHopIp;
rte.NextHopInterface := advRte.NextHopIntf;
rte.LastUsed := Current_Time
rte.LastSeqnum := Current_Time
if (validityTime)
{
rte.ExpirationTime := Current_Time + advRte.ValidityTime;
rte.Timed := true;
}
else
{
rte.Timed := false;
rte.ExpirationTime := MAXTIME;
}
rte.MetricType := advRte.MetricType;
rte.Metric := advRte.Metric;
rte.State := Idle;
}
A.1.5. LoopFree
/* return TRUE if the route R2 is LoopFree compared to R1 */
LoopFree(advRte, rte)
{
if (advRte.Cost < rte.Cost)
return true;
else
return false;
}
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A.1.6. Fetch_Rte_Msg_Table_Entry
/* Find an entry in the RteMsg table matching the given
message's msg-type, OrigAddr, TargAddr, MetricType */
Fetch_Rte_Msg_Table_Entry (rteMsg)
{
foreach (entry in RteMsgTable)
{
if (entry.msg-type == rteMsg.msg-type AND
entry.OrigAddr == rteMsg.OrigAddr AND
entry.TargAddr == rteMsg.TargAddr AND
entry.MetricType == rteMsg.MetricType)
{
return entry;
}
}
return NULL;
}
A.1.7. Update_Rte_Msg_Table
/* update the multicast route message suppression table based
on the received RteMsg, return true if it was created or
the SeqNum was updated (i.e. it needs to be regenerated) */
Update_Rte_Msg_Table(rteMsg)
{
/* search for a comparable entry */
entry := Fetch_Rte_Msg_Table_Entry(rteMsg)
/* if there is none, create one (see 6.5 and 8.6) */
if (entry does not exist)
{
entry.MessageType := rteMsg.msg_type
entry.OrigAddr := rteMsg.OrigAddr
entry.TargAddr := rteMsg.TargAddr
entry.OrigSeqNum := rteMsg.OrigSeqNum (if present)
entry.TargSeqNum := rteMsg.TargSeqNum (if present)
entry.MetricType := rteMsg.MetricType (if present) or
DEFAULT_METRIC_TYPE
entry.Timestamp := Current_Time
return true;
}
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/* if current entry is stale */
if ( (rteMsg.msg-type == RREQ AND
entry.OrigSeqNum < rteMsg.OrigSeqNum)
OR
(rteMsg.msg-type == RREP AND
entry.TargSeqNum < rteMsg.TargSeqNum))
{
entry.OrigSeqNum := rteMsg.OrigSeqNum (if present)
entry.TargSeqNum := rteMsg.TargSeqNum (if present)
entry.Timestamp := Current_Time
return true;
}
/* if received rteMsg is stale */
if ( (rteMsg.msg-type == RREQ AND
entry.OrigSeqNum > rteMsg.OrigSeqNum)
OR
(rteMsg.msg-type == RREP AND
entry.TargSeqNum > rteMsg.TargSeqNum))
{
entry.Timestamp := Current_Time
return false;
}
/* if same SeqNum but rteMsg has lower metric */
if (entry.Metric > rteMsg.Metric)
entry.Metric := rteMsg.Metric
entry.Timestamp := Current_Time
return false;
}
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A.1.8. Build_RFC_5444_message_header
/* This pseudocode shows possible RFC 5444 actions, and
would not be performed by the AODVv2 implementation.
It is shown only to provide more understanding about
the AODVv2 message that will be constructed by RFC 5444 */
Build_RFC_5444_message_header (msgType, Flags,
AddrFamily, Size, hopLimit, hopCount, tlvLength)
{
/* Build RFC 5444 message header fields */
msg-type := msgType
MF (Message Flags) := Flags
MAL (Message Address Length) := 3 for IPv4, 15 for IPv6
msg-size := Size (octets - counting MsgHdr, AddrBlk, AddrTLVs)
msg-hop-limit := hopLimit
if (hopCount != 0) /* hopCount == 0 means do not include */
msg-hop-count := hopCount
msg.tlvs-length := tlvLength
}
A.2. Example Algorithms for AODVv2 RREQ Operations
A.2.1. Generate_RREQ
Generate_RREQ
{
/* Increment sequence number */
mySeqNum := (1 + mySeqNum) /* from nonvolatile storage */
/* Marshall parameters */
outRREQ.hopLimit := MAX_HOPCOUNT /* RFC 5444 */
outRREQ.hopCount := (if included) 0
outRREQ.metricType := if not DEFAULT_METRIC_TYPE,
metric type needed by application
outRREQ.origAddr := IP address of Router Client which generated
the packet to be forwarded
outRREQ.targAddr := destination IP address in
the packet to be forwarded
outRREQ.origPrefixLen := if included, the prefix length
associated with the Router Client
outRREQ.origSeqNum := mySeqNum
outRREQ.targSeqNum := if known from route table,
target sequence number
outRREQ.origAddrMetric := 0 (default) or
MIN_METRIC(outRREQ.metricType)
outRREQ.validityTime := if included, the validity time
for route to OrigAddr
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if (outRREQ.metricType != DEFAULT_METRIC_TYPE)
{ /* Build MetricType Message TLV */
metricMsgTlv.value := outRREQ.metricType
}
/* Build Address Blk */
AddrBlk := outRREQ.origAddr and outRREQ.targAddr addresses
/* using prefix length information from
outRREQ.origPrefixLen if necessary */
/* Include each available Sequence Number in appropriate
Address Block TLV */
/* OrigSeqNum Address Block TLV */
origSeqNumAddrBlkTlv.value := outRREQ.origSeqNum
/* TargSeqNum Address Block TLV */
if (outRREQ.targSeqNum is known)
{
targSeqNumAddrBlkTlv.value := outRREQ.targSeqNum
}
/* Build Metric Address Block TLV */
metricAddrBlkTlv.value := outRREQ.origAddrMetric
if (outRREQ.validityTime is required)
{
/* Build VALIDITY_TIME Address Block TLV */
VALIDITY_TIMEAddrBlkTlv.value := outRREQ.validityTime
}
/* multicast RFC 5444 message to LL-MANET-Routers */
}
A.2.2. Receive_RREQ
Receive_RREQ (inRREQ)
{
if (inRREQ.nbrIP present in blacklist) {
if (blacklist_expiration_time < current_time)
return; /* don't process or regenerate RREQ... */
else
remove nbrIP from blacklist;
}
if (inRREQ does not contain msg_hop_limit, OrigAddr,
TargAddr, OrigSeqNum, OrigAddrMetric)
return;
if (inRREQ.origAddr and inRREQ.targAddr are not valid
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routable and unicast addresses)
return;
if (inRREQ.metricType is present but an unknown value)
return;
if (inRREQ.origAddrMetric >
MAX_METRIC[inRREQ.metricType] - Cost(Link)
return;
/* Extract inRREQ values */
advRte.Address = inRREQ.origAddr
advRte.PrefixLength = inRREQ.origPrefixLen (if present),
or the maximum address length for the
address family of advRte.Address
advRte.SeqNum = inRREQ.origSeqNum
advRte.MetricType = inRREQ.metricType (if present),
else DEFAULT_METRIC_TYPE
advRte.Metric = inRREQ.origAddrMetric
advRte.Cost = inRREQ.origAddrMetric + Cost(L)
according to the indicated MetricType, where
L is the link from the advertising router
advRte.ValidityTime = inRREQ.validityTime (if present)
advRte.NextHopIP = inRREQ.nbrIP
advRte.NextHopIntf = interface the RteMsg was received on
advRte.HopCount = inRREQ.hopCount
advRte.HopLimit = inRREQ.hopLimit
rte = Process_Routing_Info (advRte)
/* update the RteMsgTableand determine if the RREQ needs
to be regenerated */
regenerate = Update_Rte_Msg_Table(inRREQ)
if (inRREQ.targAddr is in Router Client list)
Generate_RREP(inRREQ, rte)
else if (regenerate)
Regenerate_RREQ(inRREQ, rte)
}
A.2.3. Regenerate_RREQ
Regenerate_RREQ (inRREQ, rte) /* called from receive_RREQ(),
rte is the route to OrigAddr */
{
outRREQ.hopLimit := inRREQ.hopLimit - 1
if (outRREQ.hopLimit == 0)
return; /* don't regenerate */
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if (inRREQ.hopCount exists)
{
if (inRREQ.hopCount >= MAX_HOPCOUNT)
return; /* don't regenerate */
outRREQ.hopCount := inRREQ.hopCount + 1
}
/* Marshall parameters */
outRREQ.metricType := rte.MetricType
outRREQ.origAddr := rte.Address
outRREQ.targAddr := inRREQ.targAddr
outRREQ.origPrefixLen := rte.PrefixLength
(if not equal to address length)
outRREQ.origSeqNum := rte.SeqNum
outRREQ.targSeqNum := inRREQ.targSeqNum /* if present */
outRREQ.origAddrMetric := rte.Metric
outRREQ.validityTime := rte.ValidityTime or length of time
HandlingRtr wishes to advertise route to OrigAddr
if (outRREQ.metricType != DEFAULT_METRIC_TYPE)
{ /* Build MetricType Message TLV */
metricMsgTlv.value := outRREQ.metricType
}
/* Build Address Block */
AddrBlk := outRREQ.origAddr and outRREQ.targAddr addresses
using prefix length information from outRREQ.origPrefixLen
if necessary
/* Include available Sequence Numbers in Address Block TLV */
/* OrigSeqNum Address Block TLV */
origSeqNumAddrBlkTlv.value := outRREQ.origSeqNum
/* TargSeqNum Address Block TLV */
if (outRREQ.targSeqNum is known) {
targSeqNumAddrBlkTlv.value := outRREQ.targSeqNum
}
/* Build Metric Address Block TLV */
metricAddrBlkTlv.value = outRREQ.origAddrMetric
if (outRREQ.validityTime is required)
{
/* Build VALIDITY_TIME Address Block TLV */
VALIDITY_TIMEAddrBlkTlv.value = outRREQ.validityTime
}
Build_RFC_5444_message_header (RREQ, 4, IPv4 or IPv6, NN,
outRREQ.hopLimit, outRREQ.hopCount, tlvLength)
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/* multicast RFC 5444 message to LL-MANET-Routers, or if
inRREQ was unicast the message can be unicast to the next
hop on the route to TargAddr, if known */
}
A.3. Example Algorithms for AODVv2 RREP Operations
A.3.1. Generate_RREP
Generate_RREP(inRREQ, rte)
{
/* Increment Sequence Number */
mySeqNum := (1 + mySeqNum) /* from nonvolatile storage */
/* Marshall parameters */
outRREP.hopLimit := inRREQ.hopCount
outRREP.hopCount := 0
/* Include the AckReq when:
- previous RREP does not seem to enable any data flow, OR
- when RREQ is received from same OrigAddr after RREP was
unicast to rte.nextHop
*/
outRREP.ackReq := if included, TRUE otherwise FALSE
if (rte.metricType != DEFAULT_METRIC_TYPE)
outRREP.metricType := rte.metricType
outRREP.origAddr := rte.Address
outRREP.targAddr := inRREQ.targAddr
outRREP.targPrefixLen := rte.PrefixLength
(if not equal to address length)
outRREP.targSeqNum := mySeqNum
outRREP.targAddrMetric := 0 (default) or
MIN_METRIC(rte.metricType)
outRREP.validityTime := (if included) the validity time
for route to TargAddr
if (outRREP.ackReq == TRUE)
{
/* include AckReq Message TLV */
}
if (outRREP.metricType != DEFAULT_METRIC_TYPE)
{ /* Build MetricType Message TLV */
metricMsgTlv.value := outRREP.metricType
}
/* Build Address Block */
AddrBlk := outRREP.origAddr and outRREP.targAddr addresses
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using prefix length information from outRREP.targPrefixLen
if necessary
/* TargSeqNum Address Block TLV */
targSeqNumAddrBlkTlv.value := outRREP.targSeqNum
/* Build Metric Address Block TLV containing TargAddr metric */
metricAddrBlkTlv.value := outRREP.targAddrMetric
if (outRREP.validityTime is required)
{
/* Build VALIDITY_TIME Address Block TLV */
VALIDITY_TIMEAddrBlkTlv.value = outRREP.validityTime
}
Build_RFC_5444_message_header (RREP, 4, IPv4 or IPv6, NN,
outRREP.hopLimit, outRREQ.hopCount, tlvLength)
/* unicast RFC 5444 message to rte[OrigAddr].NextHop */
}
A.3.2. Receive_RREP
Receive_RREP (inRREP)
{
if (inRREP.nbrIP present in blacklist) {
if (blacklist_expiration_time < current_time)
return; /* don't process or regenerate RREQ... */
else
remove nbrIP from blacklist;
}
if (inRREP does not contain msg_hop_limit, OrigAddr,
TargAddr, TargSeqNum, TargAddrMetric)
return;
if (inRREP.origAddr and inRREQ.targAddr are not
valid routable and unicast addresses)
return;
if (inRREP.metricType is present but an unknown value)
return;
if (inRREP.targAddrMetric >
MAX_METRIC[MetricType] - Cost(Link)
return;
/* Extract inRREP values */
advRte.Address := inRREP.targAddr
advRte.PrefixLength := inRREP.targPrefixLen f present), or the
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maximum address length for address family of advRte.Address
advRte.SeqNum := inRREP.targSeqNum
advRte.MetricType := inRREP.metricType (if present),
else DEFAULT_METRIC_TYPE
advRte.Metric := inRREP.targAddrMetric
advRte.Cost := inRREP.targAddrMetric + Cost(L) according to
inRREP's MetricType. L is the link from the advertising router
advRte.ValidityTime := inRREP.validityTime (if present)
advRte.NextHopIP := inRREP.nbrIP
advRte.NextHopIntf := interface the RteMsg was received on
advRte.HopCount := inRREP.hopCount
advRte.HopLimit := inRREP.hopLimit (if included)
rte := Process_Routing_Info (advRte)
if (inRREP includes AckReq data element)
Generate_RREP_Ack(inRREP)
/* update the RteMsgTable and determine if the RREP needs
to be regenerated */
regenerate := Update_Rte_Msg_Table(inRREP)
if (inRREP.targAddr is in the Router Client list)
send_buffered_packets(rte) /* start to use the route */
else if (regenerate)
Regenerate_RREP(inRREP, rte)
}
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A.3.3. Regenerate_RREP
Regenerate_RREP(inRREP, rte)
{
if (rte does not exist)
{
Generate_RERR(inRREP)
return;
}
outRREP.hopLimit := inRREP.hopLimit - 1
if (outRREP.hopLimit == 0) /* don't regenerate */
return;
if (inRREP.hopCount exists)
{
if (inRREP.hopCount >= MAX_HOPCOUNT)
return; /* don't regenerate */
outRREP.hopCount := inRREP.hopCount + 1
}
/* Marshall parameters */
/* Include the AckReq when:
- previous unicast RREP seems not to enable data flow, OR
- when RREQ is received from same OrigAddr after RREP
was unicast to rte.nextHop
*/
outRREP.ackReq := true or false whether to include
if (rte.metricType != DEFAULT_METRIC_TYPE)
outRREP.metricType := rte.metricType
outRREP.origAddr := inRREP.origAddr
outRREP.targAddr := rte.Address
outRREP.targPrefixLen := rte.PrefixLength
(if not equal to address length)
outRREP.targSeqNum := rte.SeqNum
outRREP.targAddrMetric := rte.Metric
outRREP.validityTime := (if included) the validity time
for route to TargAddr
outRREP.nextHop := rte.nextHop
if (outRREP.ackReq == TRUE)
{
/* include AckReq Message TLV */
}
if (outRREP.metricType != DEFAULT_METRIC_TYPE)
{ /* Build MetricType Message TLV */
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metricMsgTlv.value := outRREP.metricType
}
/* Build Address Block */
AddrBlk := {outRREP.origAddr and outRREP.targAddr}
using prefix length information from
outRREP.targPrefixLen if necessary
/* TargSeqNum Address Block TLV */
targSeqNumAddrBlkTlv.value := outRREP.targSeqNum
/* Build Metric Address Block TLV containing TargAddrMetric*/
metricAddrBlkTlv.value := outRREP.targAddrMetric
if (outRREP.validityTime is required)
{
/* Build VALIDITY_TIME Address Block TLV */
VALIDITY_TIMEAddrBlkTlv.value := outRREP.validityTime
}
Build_RFC_5444_message_header (RREP, 4, IPv4 or IPv6, NN,
outRREP.hopLimit, 0, tlvLength)
/* unicast RFC 5444 message to rte[OrigAddr].NextHop */
}
A.4. Example Algorithms for AODVv2 RERR Operations
RERR message parameters, where RERR can be inRERR or outRERR:
RERR.hopLimit := the maximum number of hops this RERR can traverse
RERR.pktSource := source IP of unforwardable packet (if present)
RERR.metricType := metric type for routes to unreachable
destinations
RERR.unreachableAddressList[] := addresses of unreachable
destinations
RERR.prefixLengthList[] := prefix lengths of unreachable
destinations
RERR.seqNumList[] := sequence numbers for unreachable destinations
RERR.intf := the interface on which the RERR was received
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A.4.1. Generate_RERR
There are two parts to this function, based on whether it was
triggered by an undeliverable packet or a broken link to neighboring
AODVv2 router.
Generate_RERR(error_type, triggerPkt, brokenLinkNbrIp)
/* error_type is either undeliverable_packet or broken_link */
{
switch (error_type)
{
case (broken_link):
/* a RERR will be required for each MetricType */
foreach metric type in use
{
num-broken-addr := 0
precursors[] := new empty precursor list
outRERR.hopLimit := MAX_HOPCOUNT
outRERR.metricType := the metric type for this loop
/* find routes which are now Invalid */
foreach (rte in route table)
{
if (brokenLinkNbrIp == rte.nextHop AND
rte.MetricType == outRERR.metricType AND
(rte.State == Active OR
(rte.State == Idle AND ENABLE_IDLE_IN_RERR)))
{
rte.State := Invalid;
precursors += rte.Precursors (if any)
outRERR.unreachableAddressList[num-broken-addr] :=
rte.Address
outRERR.prefixLengthList[num-broken-addr] :=
rte.PrefixLength
outRERR.seqNumList[num-broken-addr] := rte.SeqNum
num-broken-addr := num-broken-addr + 1
}
}
if (0 != num-broken-addr)
{ /* build and send RFC5444 message as below, then
repeat loop for other MetricTypes */ }
}
case (undeliverable_packet):
num-broken-addr=1
outRERR.hopLimit := MAX_HOPCOUNT
outRERR.pktSource := triggerPkt.srcIP or
triggerPkt.targAddr if packet was a RREP
/* optional to include outRERR.metricType */
outRERR.unreachableAddressList[0] := triggerPkt.destIP or
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triggerPkt.origAddr if packet was a RREP
}
if (triggerPkt exists)
{ /* Build PktSource Message TLV */
pktSourceMessageTlv.value := outRERR.pktSource
}
if (outRERR.metricType != DEFAULT_METRIC_TYPE)
{ /* Build MetricType Message TLV */
metricMsgTlv.value := outRERR.metricType
}
/* The remaining steps add address, prefix length
and sequence number information for each
UnreachableAddress, while conforming to the allowed MTU.
If the MTU is reached, a new message MUST be created. */
/* Build Address Block */
AddrBlk := outRERR.unreachableAddressList[]
using prefix length information from
outRERR.prefixLengthList[] if necessary
/* Add SeqNum Address Block TLV including index values */
seqNumAddrBlkTLV := outRERR.seqNumList[]
Build_RFC_5444_message_header (RERR, 4, IPv4 or IPv6, NN,
outRERR.hopLimit, 0, tlvLength)
if (undeliverable_packet)
/* unicast outRERR to rte[outRERR.pktSource].NextHop */
else if (broken_link)
/* unicast to precursors, or multicast to LL-MANET-Routers */
}
A.4.2. Receive_RERR
Receive_RERR (inRERR)
{
if (inRERR does not contain msg_hop_limit and at least
one UnreachableAddress)
return;
if (inRERR.metricType is present but an unknown value)
return;
/* Extract inRERR values, copy relevant UnreachableAddresses,
their prefix lengths, and sequence numbers to outRERR */
num-broken-addr := 0;
precursors[] := new empty list of type precursors/;
foreach (unreachableAddress in inRERR.unreachableAddressList)
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{
if (unreachableAddress is not valid routable
and unicast address)
continue;
/* find a matching route table entry, assume
DEFAULT_METRIC_TYPE if no MetricType included */
rte := Fetch_Route_Table_Entry (unreachableAddress,
inRERR.metricType)
if (rte does not exist)
continue;
if (rte.State == Invalid)/* ignore already invalid routes */
continue;
if (rte.NextHop != inRERR.nbrIP OR
rte.NextHopInterface != inRERR.intf)
continue;
if (unreachableAddress SeqNum (if known) < rte.SeqNum)
continue;
/* keep a note of all precursors of newly Invalid routes */
precursors += rte.Precursors (if any)
/* assume prefix length is address length if not included*/
if (rte.PrefixLength != unreachableAddress prefixLength)
{
/* create new route with unreachableAddress information */
invalidRte := Create_Route_Table_Entry(unreachableAddress,
unreachableAddress prefixLength,
unreachableAddress seqNum, inRERR.metricType)
invalidRte.State := Invalid
if (rte.PrefixLength > unreachableAddress prefixLength)
expunge_route(rte);
rte := invalidRte;
}
else if (rte.PrefixLength == unreachableAddress prefixLength)
rte.State := Invalid;
outRERR.unreachableAddressList[num-broken-addr] :=rte.Address
outRERR.prefixLengthList[num-broken-addr] := rte.PrefixLength
outRERR.seqNumList[num-broken-addr] := rte.SeqNum
num-broken-addr := num-broken-addr + 1
}
if (num-broken-addr)
Regenerate_RERR(outRERR, inRERR, precursors)
}
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A.4.3. Regenerate_RERR
Regenerate_RERR (outRERR, inRERR, precursors)
{
/* Marshal parameters */
outRERR.hopLimit := inRERR.hopLimit - 1
if (outRERR.hopLimit == 0) /* don't regenerate */
return;
outRERR.pktSource := inRERR.pktSource (if included)
outRERR.metricType := inRERR.MetricType (if included)
or DEFAULT_METRIC_TYPE
/* UnreachableAddressList[], SeqNumList[], and
PrefixLengthList[] are already up-to-date */
if (outRERR.pktSource exists)
{
/* Build PktSource Message TLV */
pktSourceMessageTlv.value := outRERR.pktSource
}
if (outRERR.metricType != DEFAULT_METRIC_TYPE)
{
/* Build MetricType Message TLV */
metricMsgTlv.value := outRERR.metricType
}
/* Build Address Block */
AddrBlk := outRERR.unreachableAddressList[] using prefix length
information from outRERR.prefixLengthList[] if necessary
/* Add SeqNum AddressBlock TLV including index values */
seqNumAddrTLV := outRERR.seqNumList[]
Build_RFC_5444_message_header (RERR, 4, IPv4 or IPv6, NN,
outRERR.hopLimit, 0, tlvLength)
if (outRERR.pktSource exists) {
/* unicast RFC 5444 message to outRERR.pktSource */
} else if (number of precursors == 1) {
/* unicast RFC 5444 message to precursors[0] */
} else if (number of precursors > 1) {
/* unicast RFC 5444 message to all precursors, or multicast
RFC 5444 message to RERR_PRECURSORS if preferable */
} else {
/* multicast RFC 5444 message to LL-MANET-Routers */
}
}
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A.5. Example Algorithms for AODVv2 RREP_Ack Operations
A.5.1. Generate_RREP_Ack
/* To be sent when RREP includes the AckReq data element */
Generate_RREP_Ack(inRREP)
{
Build_RFC_5444_message_header (RREP_Ack, 4, IPv4 or IPv6, NN,
1, 0, 0)
/* unicast RFC 5444 message to inRREP.nbrIP */
}
A.5.2. Receive_RREP_Ack
Receive_RREP_Ack(inRREP_Ack)
{
/* cancel timeout event for the node sending RREP_Ack */
}
A.5.3. Timeout_RREP_Ack
Timeout_RREP_Ack(outRREP)
{
/* insert unresponsive node into blacklist */
}
Appendix B. Changes since revision ...-06.txt
This section lists the changes since AODVv2 revision ...-06.txt
o Added Victoria Mercieca as co-author.
o Reorganized protocol message descriptions into major subsections
for each protocol message. For protocol messages, organized
processing into Generation, Reception, and Regeneration
subsections.
o Separated RREQ and RREP message processing description into
separate major subsection which had previously been combined into
RteMsg description.
o Enlarged RREQ Table function to include similar processing for
optional flooded RREP messages. The table name has been
correspondingly been changed to be the Table for Multicast
RteMsgs.
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o Moved sections for Multiple Interfaces and AODVv2 Control Message
Generation Limits to be major subsections of the AODVv2 Protocol
Operations section.
o Reorganized the protocol message processing steps into the
subsections as previously described, adopting a more step-by-step
presentation.
o Coalesced the router states Broken and Expired into a new combined
state named the Invalid state. No changes in processing are
required for this.
o Merged the sections describing Next-hop Router Adjacency
Monitoring and Blacklists.
o Specified that routes created during Route Discovery are marked as
Idle routes. If they are used for carrying data they become
Active routes.
o Added Route.LastSeqnum information to route table, so that route
activity and sequence number validity can be tracked separately.
An active route can still forward traffic even if the sequence
number has not been refreshed within MAX_SEQNUM_LIFETIME.
o Mandated implementation of RREP_Ack as response to AckReq Message
TLV in RREP messages. Added field to RREP_Ack to ensure
correspondence to the correct AckReq message.
o Added explanations for what happens if protocol constants are
given different values on different AODVv2 routers.
o Specified that AODVv2 implementations are free to choose their own
heuristics for reducing multicast overhead, including RFC 6621.
o Added appendix to identify AODVv2 requirements from OS
implementation of IP and ICMP.
o Deleted appendix showing example RFC 5444 packet formats.
o Clarification on the use of RFC 5497 VALIDITY_TIME.
o In Terminology, deleted superfluous definitions, added missing
definitions.
o Numerous editorial improvements and clarifications.
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Appendix C. Changes between revisions 5 and 6
This section lists the changes between AODVv2 revisions ...-05.txt
and ...-06.txt.
o Added Lotte Steenbrink as co-author.
o Reorganized section on Metrics to improve readability by putting
specific topics into subsections.
o Introduced concept of data element, which is used to clarify the
method of enabling RFC 5444 representation for AODVv2 data
elements. A list of Data Elements was introduced in section 3,
which provides a better understanding of their role than was
previously supplied by the table of notational devices.
o Replaced instances of OrigNode by OrigAddr whenever the more
specific meaning is appropriate. Similarly for instances of other
node versus address terminology.
o Introduced concepts of PrefixLengthList and MetricList in order to
avoid use of index-based terminology such as OrigNdx and TargNdx.
o Added section 5, "AODVv2 Message Transmission", describing the
intended interface to RFC 5444.
o Included within the main body of the specification the mandatory
setting of the TLV flag thassingleindex for TLVs OrigSeqNum and
TargSeqNum.
o Removed the Route.Timed state. Created a new flag for route table
entries known as Route.Timed. This flag can be set when the route
is in the active state. Previous description would require that
the route table entry be in two states at the same time, which
seems to be misleading. The new flag is used to clarify other
specification details for Timed routes.
o Created table 3 to show the correspondence between AODVv2 data
elements and RFC 5444 message components.
o Replaced "invalid" terminology by the more specific terms "broken"
or "expired" where appropriate.
o Eliminated the instance of duplicate specification for inclusion
of OrigNode (now, OrigAddr) in the message.
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o Corrected the terminology to be Mid instead of Tail for the
trailing address bits of OrigAddr and TargAddr for the example
message formats in the appendices.
o Repaired remaining instances of phraseology that could be
construed as indicating that AODV only supports a single network
interface.
o Numerous editorial improvements and clarifications.
Appendix D. Changes from revision ...-04.txt
This section lists the changes between AODVv2 revisions ...-04.txt
and ...-05.txt.
o Normative text moved out of definitions into the relevant section
of the body of the specification.
o Editorial improvements and improvements to consistent terminology
were made. Replaced "retransmit" by the slightly more accurate
term "regenerate".
o Issues were resolved as discussed on the mailing list.
o Changed definition of LoopFree as suggested by Kedar Namjoshi and
Richard Trefler to avoid the failure condition that they have
described. In order to make understanding easier, replaced
abstract parameters R1 by RteMsg and R2 by Route to reduce the
level of abstraction when the function LoopFree is discussed.
o Added text to clarify that different metrics may have different
data types and different ranges of acceptable values.
o Added text to section "RteMsg Structure" to emphasize the proper
use of RFC 5444.
o Included within the main body of the specification the mandatory
setting of the TLV flag thassingleindex for TLVs OrigSeqNum and
TargSeqNum.
o Made more extensive use of the AdvRte terminology, in order to
better distinguish between the incoming RREQ or RREP message
(i.e., RteMsg) versus the route advertised by the RteMsg (i.e.,
AdvRte).
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Appendix E. Changes from revision ...-03.txt
This section lists the changes between AODVv2 revisions ...-03.txt
and ...-04.txt.
o An appendix was added to exhibit algorithmic code for
implementation of AODVv2 functions.
o Numerous editorial improvements and improvements to consistent
terminology were made. Terminology related to prefix lengths was
made consistent. Some items listed in "Notational Conventions"
were no longer used, and so deleted.
o Issues were resolved as discussed on the mailing list.
o Appropriate instances of "may" were changed to "MAY".
o Definition inserted for "upstream".
o Route.Precursors included as an *optional* route table field
o Reworded text to avoid use of "relevant".
o Deleted references to "DestOnly" flag.
o Refined statements about MetricType TLV to allow for omission when
MetricType == HopCount.
o Bulletized list in section 8.1
o ENABLE_IDLE_UNREACHABLE renamed to be ENABLE_IDLE_IN_RERR
o Transmission and subscription to LL-MANET-Routers converted to
MUST from SHOULD.
Appendix F. Changes from revision ...-02.txt
This section lists the changes between AODVv2 revisions ...-02.txt
and ...-03.txt.
o The "Added Node" feature was removed. This feature was intended
to enable additional routing information to be carried within a
RREQ or a RREP message, thus increasing the amount of topological
information available to nodes along a routing path. However,
enlarging the packet size to include information which might never
be used can increase congestion of the wireless medium. The
feature can be included as an optional feature at a later date
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when better algorithms are understood for determining when the
inclusion of additional routing information might be worthwhile.
o Numerous editorial improvements and improvements to consistent
terminology were made. Instances of OrigNodeNdx and TargNodeNdx
were replaced by OrigNdx and TargNdx, to be consistent with the
terminology shown in Table 2.
o Example RREQ and RREP message formats shown in the Appendices were
changed to use OrigSeqNum and TargSeqNum message TLVs instead of
using the SeqNum message TLV.
o Inclusion of the OrigNode's SeqNum in the RREP message is not
specified. The processing rules for the OrigNode's SeqNum were
incompletely specified in previous versions of the draft, and very
little benefit is foreseen for including that information, since
reverse path forwarding is used for the RREP.
o Additional acknowledgements were included, and contributors names
were alphabetized.
o Definitions in the Terminology section capitalize the term to be
defined.
o Uncited bibliographic entries deleted.
o Ancient "Changes" sections were deleted.
Appendix G. Features of IP needed by AODVv2
AODVv2 needs the following:
o information that IP routes are requested
o information that packets are flowing
o the ability to queue packets.
A reactive protocol reacts when a route is needed. One might say
that a route is requested when an application tries to send a packet.
The fundamental concept of reactive routing is to avoid creating
routes that are not needed, and the way that has been used to know
whether a route is needed is when an application tries to send a
packet.
If an application tries to send a packet, and the route is not
available, the packet has to wait until the route is available.
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Appendix H. Multi-homing Considerations
This non-normative information is provided simply to document the
results of previous efforts to enable multi-homing. The intention is
to simplify the task of future specification if multihoming becomes
needed for reactive protocol operation.
Multi-homing is not supported by the AODVv2 specification. There has
been previous work indicating that it can be supported by expanding
the sequence number to include the AODVv2 router's IP address as a
parsable field of the SeqNum. Otherwise, comparing sequence numbers
would not work to evaluate freshness. Even when the IP address is
included, there isn't a good way to compare sequence numbers from
different IP addresses, but at least a handling node can determine
whether the two given sequence numbers are comparable. If the route
table can store multiple routes for the same destination, then multi-
homing can work with sequence numbers augmented by IP addresses.
This non-normative information is provided simply to document the
results of previous efforts to enable multi-homing. The intention is
to simplify the task of future specification if multihoming becomes
needed for reactive protocol operation.
Appendix I. Shifting Network Prefix Advertisement Between AODVv2
Routers
Only one AODVv2 router within a MANET SHOULD be responsible for a
particular address at any time. If two AODVv2 routers dynamically
shift the advertisement of a network prefix, correct AODVv2 routing
behavior must be observed. The AODVv2 router adding the new network
prefix must wait for any existing routing information about this
network prefix to be purged from the network. Therefore, it must
wait at least ROUTER_SEQNUM_AGE_MAX_TIMEOUT after the previous AODVv2
router for this address stopped advertising routing information on
its behalf.
Authors' Addresses
Charles E. Perkins
Futurewei Inc.
2330 Central Expressway
Santa Clara, CA 95050
USA
Phone: +1-408-330-4586
Email: charliep@computer.org
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Stan Ratliff
Idirect
13861 Sunrise Valley Drive, Suite 300
Herndon, VA 20171
USA
Email: ratliffstan@gmail.com
John Dowdell
Airbus Defence and Space
Celtic Springs
Newport, Wales NP10 8FZ
United Kingdom
Email: john.dowdell@airbus.com
Lotte Steenbrink
HAW Hamburg, Dept. Informatik
Berliner Tor 7
D-20099 Hamburg
Germany
Email: lotte.steenbrink@haw-hamburg.de
Victoria Mercieca
Airbus Defence and Space
Celtic Springs
Newport, Wales NP10 8FZ
United Kingdom
Email: victoria.mercieca@airbus.com
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