Mobile Ad hoc Networks Working Group C. Perkins
Internet-Draft Futurewei
Intended status: Experimental S. Ratliff
Expires: October 22, 2016 Idirect
J. Dowdell
Airbus Defence and Space
L. Steenbrink
HAW Hamburg, Dept. Informatik
V. Mercieca
Airbus Defence and Space
April 20, 2016
Ad Hoc On-demand Distance Vector Version 2 (AODVv2) Routing
draft-ietf-manet-aodvv2-15
Abstract
The Ad Hoc On-demand Distance Vector Version 2 (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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on October 22, 2016.
Copyright Notice
Copyright (c) 2016 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
(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 9
4. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. InterfaceSet . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Router Client Set . . . . . . . . . . . . . . . . . . . . 11
4.3. Neighbor Set . . . . . . . . . . . . . . . . . . . . . . 12
4.4. Sequence Numbers . . . . . . . . . . . . . . . . . . . . 12
4.5. Local Route Set . . . . . . . . . . . . . . . . . . . . . 13
4.6. Multicast Route Message Set . . . . . . . . . . . . . . . 15
4.7. Route Error (RERR) Set . . . . . . . . . . . . . . . . . 17
5. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6. AODVv2 Protocol Operations . . . . . . . . . . . . . . . . . 19
6.1. Initialization . . . . . . . . . . . . . . . . . . . . . 19
6.2. Next Hop Monitoring . . . . . . . . . . . . . . . . . . . 20
6.3. Neighbor Set Update . . . . . . . . . . . . . . . . . . . 21
6.4. Interaction with the Forwarding Plane . . . . . . . . . . 23
6.5. Message Transmission . . . . . . . . . . . . . . . . . . 24
6.6. Route Discovery, Retries and Buffering . . . . . . . . . 25
6.7. Processing Received Route Information . . . . . . . . . . 26
6.7.1. Evaluating Route Information . . . . . . . . . . . . 27
6.7.2. Applying Route Updates . . . . . . . . . . . . . . . 29
6.8. Suppressing Redundant Messages Using the Multicast Route
Message Set . . . . . . . . . . . . . . . . . . . . . . . 31
6.9. Suppressing Redundant Route Error Messages using the
Route Error Set . . . . . . . . . . . . . . . . . . . . . 33
6.10. Local Route Set Maintenance . . . . . . . . . . . . . . . 34
6.10.1. LocalRoute State Changes . . . . . . . . . . . . . . 34
6.10.2. Reporting Invalid Routes . . . . . . . . . . . . . . 36
7. AODVv2 Protocol Messages . . . . . . . . . . . . . . . . . . 36
7.1. Route Request (RREQ) Message . . . . . . . . . . . . . . 37
7.1.1. RREQ Generation . . . . . . . . . . . . . . . . . . . 38
7.1.2. RREQ Reception . . . . . . . . . . . . . . . . . . . 39
7.1.3. RREQ Regeneration . . . . . . . . . . . . . . . . . . 40
7.2. Route Reply (RREP) Message . . . . . . . . . . . . . . . 41
7.2.1. RREP Generation . . . . . . . . . . . . . . . . . . . 42
7.2.2. RREP Reception . . . . . . . . . . . . . . . . . . . 44
7.2.3. RREP Regeneration . . . . . . . . . . . . . . . . . . 45
7.3. Route Reply Acknowledgement (RREP_Ack) Message . . . . . 46
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7.3.1. RREP_Ack Generation . . . . . . . . . . . . . . . . . 46
7.3.2. RREP_Ack Reception . . . . . . . . . . . . . . . . . 46
7.4. Route Error (RERR) Message . . . . . . . . . . . . . . . 47
7.4.1. RERR Generation . . . . . . . . . . . . . . . . . . . 48
7.4.2. RERR Reception . . . . . . . . . . . . . . . . . . . 49
7.4.3. RERR Regeneration . . . . . . . . . . . . . . . . . . 51
8. RFC 5444 Representation . . . . . . . . . . . . . . . . . . . 51
8.1. Route Request Message Representation . . . . . . . . . . 53
8.1.1. Message Header . . . . . . . . . . . . . . . . . . . 53
8.1.2. Message TLV Block . . . . . . . . . . . . . . . . . . 53
8.1.3. Address Block . . . . . . . . . . . . . . . . . . . . 53
8.1.4. Address Block TLV Block . . . . . . . . . . . . . . . 53
8.2. Route Reply Message Representation . . . . . . . . . . . 54
8.2.1. Message Header . . . . . . . . . . . . . . . . . . . 54
8.2.2. Message TLV Block . . . . . . . . . . . . . . . . . . 54
8.2.3. Address Block . . . . . . . . . . . . . . . . . . . . 55
8.2.4. Address Block TLV Block . . . . . . . . . . . . . . . 55
8.3. Route Reply Acknowledgement Message Representation . . . 56
8.3.1. Message Header . . . . . . . . . . . . . . . . . . . 56
8.3.2. Message TLV Block . . . . . . . . . . . . . . . . . . 56
8.3.3. Address Block . . . . . . . . . . . . . . . . . . . . 56
8.3.4. Address Block TLV Block . . . . . . . . . . . . . . . 57
8.4. Route Error Message Representation . . . . . . . . . . . 57
8.4.1. Message Header . . . . . . . . . . . . . . . . . . . 57
8.4.2. Message TLV Block . . . . . . . . . . . . . . . . . . 57
8.4.3. Address Block . . . . . . . . . . . . . . . . . . . . 57
8.4.4. Address Block TLV Block . . . . . . . . . . . . . . . 58
9. Simple External Network Attachment . . . . . . . . . . . . . 58
10. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 59
10.1. Timers . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.2. Protocol Constants . . . . . . . . . . . . . . . . . . . 62
10.3. Local Settings . . . . . . . . . . . . . . . . . . . . . 63
10.4. Network-Wide Settings . . . . . . . . . . . . . . . . . 63
10.5. MetricType Allocation . . . . . . . . . . . . . . . . . 63
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 64
11.1. RFC 5444 Message Types . . . . . . . . . . . . . . . . . 64
11.2. RFC 5444 Address Block TLV Types . . . . . . . . . . . . 64
11.3. ADDRESS_TYPE TLV Values . . . . . . . . . . . . . . . . 65
12. Security Considerations . . . . . . . . . . . . . . . . . . . 65
12.1. Availability . . . . . . . . . . . . . . . . . . . . . . 66
12.1.1. Denial of Service . . . . . . . . . . . . . . . . . 66
12.1.2. Malicious RERR messages . . . . . . . . . . . . . . 67
12.1.3. False Confirmation of Link Bidirectionality . . . . 68
12.1.4. Message Deletion . . . . . . . . . . . . . . . . . . 68
12.2. Confidentiality . . . . . . . . . . . . . . . . . . . . 69
12.3. Integrity . . . . . . . . . . . . . . . . . . . . . . . 69
12.3.1. Message Insertion . . . . . . . . . . . . . . . . . 69
12.3.2. Message Modification - Man in the Middle . . . . . . 70
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12.3.3. Replay Attacks . . . . . . . . . . . . . . . . . . . 70
12.4. Protection Mechanisms . . . . . . . . . . . . . . . . . 71
12.4.1. Confidentiality and Authentication . . . . . . . . . 71
12.4.2. Integrity and Trust using ICVs . . . . . . . . . . . 71
12.4.3. Replay Protection using Timestamps . . . . . . . . . 71
12.4.4. Application to AODVv2 . . . . . . . . . . . . . . . 71
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 74
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 74
14.1. Normative References . . . . . . . . . . . . . . . . . . 74
14.2. Informative References . . . . . . . . . . . . . . . . . 75
Appendix A. AODVv2 Draft Updates . . . . . . . . . . . . . . . . 77
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 77
1. Overview
The Ad hoc On-Demand Distance Vector Version 2 (AODVv2) protocol
enables dynamic, self-starting, multihop routing between
participating mobile nodes wishing to establish and maintain an ad
hoc network. The basic operations of the AODVv2 protocol are route
discovery and route maintenance. AODVv2 does not require nodes to
maintain routes to destinations that are not in active communication.
AODVv2 allows mobile nodes to respond to link breakages and changes
in network topology in a timely manner. The operation of AODVv2 is
loop-free, and by avoiding the Bellman-Ford "counting to infinity"
problem offers quick convergence when the ad hoc network topology
changes (typically, when a node moves in the network). When links
break, AODVv2 causes the affected set of nodes to be notified so that
they are able to invalidate the routes using the lost link.
One distinguishing feature of AODVv2 is its use of a destination
sequence number for each route entry. The destination sequence
number is created by the destination to be included along with any
route information it sends to requesting nodes. Using destination
sequence numbers ensures loop freedom and is simple to program.
Given the choice between two routes to a destination, a requesting
node is required to select the one with the greatest sequence number.
Compared to AODV [RFC3561], AODVv2 has moved some features out of the
scope of the document, notably intermediate route replies, expanding
ring search, and precursor lists. However, the document has been
designed to allow their specification in a separate document. Hello
messages and local repair have been removed. AODVv2 provides a
mechanism for the use of multiple metric types. Message formats have
been updated and made compliant with [RFC5444]. AODVv2 control
messages are defined as sets of data, which are mapped to message
elements using the Generalized MANET Packet/Message Format defined in
[RFC5444] and sent using the parameters in [RFC5498]. Verification
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of link bidirectionality has been substantially improved, and
additional refinements made for route timeouts and state management.
AODVv2 is an Experimental protocol. The purpose of the experiment
with AODVv2 is to gain information on the behavior of the protocol in
real-world deployments, furthering the knowledge base of both
reactive protocols in general, and with AODVv2 in particular.
Another goal of the experiment is to determine if sufficient demand
exists for the AODVv2 protocol to prompt an effort to bring the
protocol to Standards Track.
The basic operations of the AODVv2 protocol are route discovery and
route maintenance.
An AODVv2 router is configured to perform route discovery on behalf
of a configured set of IP addresses known as Router Clients. Route
discovery is performed when an AODVv2 router needs to forward an IP
packet from one of its Router Clients, but does not have a valid
route to the packet's destination. AODVv2 routers use Route Request
(RREQ) and Route Reply (RREP) messages to carry route information
between the originator of the route discovery and the router
responsible for the target, establishing a route to both endpoints on
all intermediate routers. A metric value is included to represent
the cost of the route contained within the message. AODVv2 uses
sequence numbers to identify stale routing information, and compares
route metric values to determine if advertised routes could form
loops.
Route maintenance includes confirming bidirectionality of links to
next hop AODVv2 routers, issuing Route Error (RERR) messages,
reacting to received Route Error messages, and extending and
enforcing route timeouts.
The on-demand nature of AODVv2 requires signals to be exchanged
between AODVv2 and the forwarding plane. These signals indicate
when: a packet is to be forwarded, in order to initiate route
discovery; packet forwarding fails, in order to initiate route error
reporting; a packet is successfully forwarded, for route maintenance.
Security for authentication of AODVv2 routers and encryption of
control messages is accomplished using the TIMESTAMP and ICV TLVs
defined in [RFC7182].
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
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[RFC2119]. In addition, this document uses terminology from
[RFC5444], and defines the following terms:
AddressList
A list of IP addresses as used in AODVv2 messages.
AckReq
Used in a Route Reply message to indicate the IP address of the
router from which a Route Reply Acknowledgement is expected.
AdvRte
A route advertised in an incoming route message.
AODVv2 Router
An IP addressable device in the ad hoc network that performs the
AODVv2 protocol operations specified in this document.
CurrentTime
The current time as maintained by the AODVv2 router.
ENAR (External Network Access Router)
An AODVv2 router with an interface to an external, non-AODVv2
network.
InterfaceSet
The set of all network interfaces supporting AODVv2.
Invalid route
A route that cannot be used for forwarding but still contains
useful sequence number information.
LocalRoute
An entry in the Local Route Set as defined in Section 4.5.
MANET
A Mobile Ad Hoc Network as defined in [RFC2501].
MetricType
The metric type for a metric value included in a message.
MetricTypeList
A list of metric types associated with the addresses in the
AddressList of a Route Error message.
Neighbor
An AODVv2 router from which an RREQ or RREP message has been
received. Neighbors exchange routing information and verify
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bidirectionality of the link to a neighbor before installing a
route via that neighbor into the Local Route Set.
OrigAddr
The source IP address of the IP packet triggering route discovery.
OrigMetric
The metric value associated with the route to OrigAddr (and any
other addresses included in the given prefix length).
OrigPrefixLen
The prefix length, in bits, configured in the Router Client entry
which includes OrigAddr.
OrigSeqNum
The sequence number of the AODVv2 router which originated the
Route Request on behalf of OrigAddr.
PktSource
The source address of the IP packet which triggered a Route Error
message.
PrefixLengthList
A list of routing prefix lengths associated with the addresses in
the AddressList of a message.
Reactive
Performed only in reaction to specific events. In AODVv2, routes
are requested only when data packets need to be forwarded. In
this document, "reactive" is synonymous with "on-demand".
RERR (Route Error)
The AODVv2 message type used to indicate that an AODVv2 router
does not have a valid LocalRoute toward one or more particular
destinations.
RERR_Gen (RERR Generating Router)
The AODVv2 router generating a Route Error message.
RerrMsg (RERR Message)
A Route Error (RERR) message.
Routable Unicast IP Address
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.
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Router Client
An address or address range configured on an AODVv2 router, on
behalf of which that router will initiate and respond to route
discoveries. These addresses may be used by the AODVv2 router
itself or by non-routing devices that are reachable without
traversing another AODVv2 router.
RREP (Route Reply)
The AODVv2 message type used to reply to a Route Request message.
RREP_Gen (RREP Generating Router)
The AODVv2 router that generates the Route Reply message, i.e.,
the router configured with TargAddr as a Router Client.
RREQ (Route Request)
The AODVv2 message type used to discover a route to TargAddr and
distribute information about a route to OrigAddr.
RREQ_Gen (RREQ Generating Router)
The AODVv2 router that generates the Route Request message, i.e.,
the router configured with OrigAddr as a Router Client.
RteMsg (Route Message)
A Route Request (RREQ) or Route Reply (RREP) message.
SeqNum
The sequence number maintained by an AODVv2 router to indicate
freshness of route information.
SeqNumList
A list of sequence numbers associated with the addresses in the
AddressList of a message.
TargAddr
The target address of a route request, i.e., the destination
address of the IP packet triggering route discovery.
TargMetric
The metric value associated with the route to TargAddr (and any
other addresses included in the given prefix length).
TargPrefixLen
The prefix length, in bits, configured in the Router Client entry
which includes TargAddr.
TargSeqNum
The sequence number of the AODVv2 router which originated the
Route Reply on behalf of TargAddr.
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Unreachable Address
An address reported in a Route Error message, as described in
Section 7.4.1.
Upstream
In the direction from destination to source (from TargAddr to
OrigAddr).
ValidityTime
The length of time the route described by the message is offered.
Valid route
A route that can be used for forwarding, as described in
Section 7.4.1.
This document uses the notational conventions in Table 1 to simplify
the text.
+-----------------------+------------------------------------+
| Notation | Meaning |
+-----------------------+------------------------------------+
| Route[Address] | A route toward Address |
| Route[Address].Field | A field in a route toward Address |
| RteMsg.Field | A field in either RREQ or RREP |
+-----------------------+------------------------------------+
Table 1: Notational Conventions
3. Applicability Statement
The AODVv2 routing protocol is a reactive routing protocol intended
for use in mobile ad hoc wireless networks. A reactive protocol only
sends messages to discover a route when there is data to send on that
route. Therefore, a reactive routing protocol requires certain
interactions with the forwarding plane (for example, to indicate when
a packet is to be forwarded, in order to initiate route discovery).
The set of signals exchanged between AODVv2 and the forwarding plane
are discussed in Section 6.4.
AODVv2 is designed for stub or disconnected mobile ad hoc networks,
i.e., non-transit networks or those not connected to the internet.
AODVv2 can, however, be configured to perform gateway functions when
attached to external networks, as discussed in Section 9.
AODVv2 handles a wide variety of mobility and traffic patterns by
determining routes on-demand. In networks with a large number of
routers, AODVv2 is best suited for relatively sparse traffic
scenarios where each router forwards IP packets to a small percentage
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of other AODVv2 routers in the network. In this case fewer routes
are needed, and therefore less control traffic is produced. Data
packets may be buffered until a route to their destination is
available, as described in Section 6.6.
AODVv2 provides for message integrity and security against replay
attacks by using integrity check values, timestamps and sequence
numbers, as described in Section 12. If security associations can be
established, encryption can be used for AODVv2 messages to ensure
that only trusted routers participate in routing operations.
Since the route discovery process aims for a route to be established
in both directions along the same path, uni-directional links are not
suitable. AODVv2 will detect and exclude those links from route
discovery. The route discovered is optimised for the requesting
router, and the return path may not be the optimal route.
AODVv2 is applicable to memory constrained devices, since only a
little routing state is maintained in each AODVv2 router. AODVv2
routes that are not needed for forwarding data do not need to be
maintained. On routers unable to store persistent AODVv2 state,
recovery can impose a performance penalty (e.g., in case of AODVv2
router reboot), since if a router loses its sequence number, there is
a delay before the router can resume full operations. This is
described in Section 6.1.
AODVv2 supports routers with multiple interfaces and multiple IP
addresses per interface. A router may also use the same IP address
on multiple interfaces. AODVv2 requires only that each interface
configured for AODVv2 has at least one unicast IP address. Address
assignment procedures are out of scope for AODVv2.
AODVv2 supports Router Clients with multiple interfaces, as long as
each interface is configured with its own unicast IP address. Multi-
homing of a Router Client IP address is not supported by AODVv2, and
therefore an IP address SHOULD NOT be configured as a Router Client
on more than one AODVv2 router at any one time.
The routing algorithm in AODVv2 MAY be operated at layers other than
the network layer, using layer-appropriate addresses.
4. Data Structures
4.1. InterfaceSet
The InterfaceSet is a conceptual data structure which contains
information about all interfaces available to AODVv2. Each element
in the InterfaceSet MUST contain the following:
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Interface.Id
An identifier that is unique in node-local scope and that allows
the AODVv2 implementation to identify exactly one local network
interface.
If multiple interfaces of the AODVv2 router are configured for use by
AODVv2, they MUST be configured in the InterfaceSet.
Otherwise the InterfaceSet MAY be empty.
4.2. Router Client Set
An AODVv2 router provides route discovery services for its own local
applications and for other non-routing devices that are reachable
without traversing another AODVv2 router. The addresses used by
these devices, and the AODVv2 router itself, are configured in the
Router Client Set. An AODVv2 router will only originate Route Request
and Route Reply messages on behalf of configured Router Client
addresses.
Router Client Set entries MUST contain:
RouterClient.IPAddress
An IP address or the start of an address range that requires route
discovery services from the AODVv2 router.
RouterClient.PrefixLength
The length, in bits, of the routing prefix associated with the
RouterClient.IPAddress. If a prefix length is included, the
AODVv2 router MUST provide connectivity for all addresses within
that prefix.
RouterClient.Cost
The cost associated with reaching this address or address range.
A Router Client address MUST NOT be served by more than one AODVv2
router at any one time. To shift responsibility for a Router Client
to a different AODVv2 router, correct AODVv2 routing behavior MUST be
observed; The AODVv2 router adding the Router Client MUST wait for
any existing routing information about this Router Client to be
purged from the network, i.e., at least MAX_SEQNUM_LIFETIME since the
last SeqNum update on the router which is removing this Router
Client.
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4.3. Neighbor Set
A Neighbor Set MUST be maintained with information about neighboring
AODVv2 routers. Neighbor Set entries are stored when AODVv2 messages
are received. If the Neighbor is chosen as a next hop on an
installed route, the link to the Neighbor MUST be tested for
bidirectionality and the result stored in this set. A route will
only be considered valid when the link is confirmed to be
bidirectional.
Neighbor Set entries MUST contain:
Neighbor.IPAddress
An IP address of the neighboring router, learned from the source
IP address of a received route message.
Neighbor.State
Indicates whether the link to the neighbor is bidirectional.
There are three possible states: Confirmed, Unknown, and
Blacklisted. Unknown is the initial state. Confirmed indicates
that the link to the neighbor has been confirmed as bidirectional.
Blacklisted indicates that the link to the neighbor is uni-
directional. Section 6.2 discusses how to monitor link
bidirectionality.
Neighbor.ResetTime
When the value of Neighbor.State is Blacklisted, this indicates
the time at which the value of Neighbor.State will revert to
Unknown. By default this value is calculated at the time the
router is blacklisted and is equal to CurrentTime +
MAX_BLACKLIST_TIME. When the value of Neighbor.State is not
Blacklisted, this time is set to INFINITY_TIME.
Neighbor.Interface
The interface on which the link to the neighbor was established.
4.4. Sequence Numbers
Sequence numbers enable AODVv2 routers to determine the temporal
order of route discovery messages, identifying stale routing
information so that it can be discarded. The sequence number
fulfills the same roles as the "Destination Sequence Number" of DSDV
[Perkins94], and the AODV Sequence Number in [RFC3561].
Each AODVv2 router in the network MUST maintain its own sequence
number. All RREQ and RREP messages created by an AODVv2 router
include the router's sequence number, reported as a 16-bit unsigned
integer. Each AODVv2 router MUST ensure that its sequence number is
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strictly increasing, and that it is incremented by one (1) whenever
an RREQ or RREP is created, except when the sequence number is 65,535
(the maximum value of a 16-bit unsigned integer), in which case it
MUST be reset to one (1). The value zero (0) is reserved to indicate
that the sequence number is unknown.
An AODVv2 router MUST only attach its own sequence number to
information about a route to one of its configured Router Clients,
all route messages regenerated by other routers retain the
originator's sequence number. Tod determine staleness, the
previously stored sequence number associated with the originator, is
subtracted from the incoming sequence number. The result of the
subtraction is to be interpreted as a signed 16-bit integer, and if
less than zero, the information in the new AODVv2 message is stale
and MUST be discarded.
This, along with the processes in Section 6.7.1, ensures loop
freedom.
An AODVv2 router SHOULD maintain its sequence number in persistent
storage. If the sequence number is lost, the router MUST follow the
procedure in Section 6.1 to safely resume routing operations with a
new sequence number.
4.5. Local Route Set
All AODVv2 routers MUST maintain a Local Route Set, containing
information about routes learned from AODVv2 route messages. The
Local Route Set is stored separately from the forwarding plane's
routing table (referred to as Routing Information Base (RIB)), which
may be updated by other routing protocols operating on the AODVv2
router as well. The Routing Information Base is updated using
information from the Local Route Set. Alternatively, implementations
MAY choose to modify the Routing Information Base directly.
Routes learned from AODVv2 route messages are referred to in this
document as LocalRoutes, and MUST contain the following information:
LocalRoute.Address
An address, which, when combined with LocalRoute.PrefixLength,
describes the set of destination addresses this route includes.
LocalRoute.PrefixLength
The prefix length, in bits, associated with LocalRoute.Address.
LocalRoute.SeqNum
The sequence number associated with LocalRoute.Address, obtained
from the last route message that successfully updated this entry.
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LocalRoute.NextHop
The source IP address of the IP packet containing the AODVv2
message advertising the route to LocalRoute.Address, i.e. an IP
address of the AODVv2 router used for the next hop on the path
toward LocalRoute.Address.
LocalRoute.NextHopInterface
The interface used to send IP packets toward LocalRoute.Address.
LocalRoute.LastUsed
If this route is installed in the Routing Information Base, the
time it was last used to forward an IP packet.
LocalRoute.LastSeqNumUpdate
The time LocalRoute.SeqNum was last updated.
LocalRoute.ExpirationTime
The time at which this LocalRoute MUST be marked as Invalid. An
AODVv2 router MAY be offered a route for a limited time. In this
case, the route is referred to as a timed route. If a route is
not timed, LocalRoute.ExpirationTime is INFINITY_TIME.
LocalRoute.MetricType
The type of metric associated with this route.
LocalRoute.Metric
The cost of the route toward LocalRoute.Address expressed in units
consistent with LocalRoute.MetricType.
LocalRoute.State
The last known state (Unconfirmed, Idle, Active, or Invalid) of
the route.
There are four possible states for a LocalRoute:
Unconfirmed
A route learned from a Route Request message, which has not yet
been confirmed as bidirectional. It MUST NOT be used for
forwarding IP packets, and therefore it is not referred to as a
valid route. This state only applies to routes learned through
RREQ messages.
Idle
A route which has been learned from a route message, and has also
been confirmed, but has not been used in the last ACTIVE_INTERVAL.
It is able to be used for forwarding IP packets, and therefore it
is referred to as a valid route.
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Active
A route which has been learned from a route message, and has also
been confirmed, and has been used in the last ACTIVE_INTERVAL. It
is able to be used for forwarding IP packets, and therefore it is
referred to as a valid route.
Invalid
A route which has expired or been lost. It MUST NOT be used for
forwarding IP packets, and therefore it is not referred to as a
valid route. Invalid routes contain sequence number information
which allows incoming information to be assessed for freshness.
When the Local Route Set is stored separately from the Routing
Information Base, routes are added to the Routing Information Base
when LocalRoute.State is valid (set to Active or Idle), and removed
from the Routing Information Base when LocalRoute.State becomes
Invalid.
Changes to LocalRoute state are detailed in Section 6.10.1.
Multiple valid routes for the same address and prefix length but for
different metric types may exist in the Local Route Set, but the
decision of which of these routes to install in the Routing
Information Base to use for forwarding is outside the scope of
AODVv2.
4.6. Multicast Route Message Set
A route message (RteMsg) is either a Route Request or Route Reply
message. RREQ messages are multicast by default and regenerated
multiple times, and RREP messages will be multicast when the link to
the next router is not known to be bidirectional. Multiple similar
route messages might be received by any one router during one route
discovery attempt. The AODVv2 router does not need to regenerate or
respond to every one of these messages.
The Multicast Route Message Set is a conceptual set which contains
information about previously received multicast route messages, so
that incoming route messages can be compared with previously received
messages to determine if the incoming information is redundant or
stale, and the router can avoid sending redundant control traffic.
Multicast Route Message Set entries MUST contain the following
information:
RteMsg.MessageType
Either RREQ or RREP.
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RteMsg.OrigAddr
The source address of the IP packet triggering the route request.
RteMsg.OrigPrefixLen
The prefix length associated with RteMsg.OrigAddr, originally from
the Router Client entry on RREQ_Gen which includes
RteMsg.OrigAddr.
RteMsg.TargAddr
The destination address of the IP packet triggering the route
request.
RteMsg.TargPrefixLen
The prefix length associated with RteMsg.TargAddr, originally from
the Router Client entry on RREP_Gen which includes
RteMsg.TargAddr. If RteMsg is a RREQ, RteMsg.TargPrefixLen MUST
equal address length.
RteMsg.OrigSeqNum
The sequence number associated with the route to OrigAddr, if
RteMsg is an RREQ.
RteMsg.TargSeqNum
The sequence number associated with the route to TargAddr, if
RteMsg is an RREP.
RteMsg.MetricType
The metric type of the route requested.
RteMsg.Metric
The metric value received in the RteMsg.
RteMsg.Timestamp
The last time this Multicast Route Message Set entry was updated.
RteMsg.RemoveTime
The time at which this entry MUST be removed from the Multicast
Route Message Set. This is set to CurrentTime +
MAX_SEQNUM_LIFETIME, whenever the sequence number of this entry
(RteMsg.OrigSeqNum for an RREQ, or RteMsg.TargSeqNum for an RREP)
is updated.
RteMsg.AckReqAddr
The address from which a RREP_Ack is expected, if RteMsg is a RREP
that contains an AckReq.
RteMsg.Interface
The interface on which the message was received.
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The Multicast Route Message Set is maintained so that no two entries
have the same MessageType, OrigAddr, TargAddr, and MetricType. See
Section 6.8 for details about updating this set.
4.7. Route Error (RERR) Set
Each sent RERR message SHOULD be recorded in a conceptual set called
the Route Error (RERR) Set. Each entry contains the following
information:
RerrMsg.Timeout
The time after which the entry SHOULD be deleted.
RerrMsg.AddressList
The AddressList of the RERR to be recorded.
RerrMsg.PktSource:
The PktSource of the RERR to be recorded, if any.
See section Section 6.9 for instructions on how to update the set.
5. Metrics
Metrics measure a cost or quality associated with a route or a link,
e.g., latency, delay, financial cost, energy, etc. Metric values are
reported in Route Request and Route Reply messages.
In Route Request messages, the metric describes the cost of the route
from OrigAddr (and any other addresses included in the prefix length
of RREQ_Gen's Router Client entry for OrigAddr) to the router sending
the Route Request. For RREQ_Gen, this is the cost associated with
the Router Client entry which includes OrigAddr. For routers which
regenerate the RREQ, this is the cost from OrigAddr to the
regenerating router, combining the metric value from the received
RREQ message with knowledge of the link cost from the sender to the
receiver, i.e., the incoming link cost. This updated route cost is
included when regenerating the Route Request message, and used to
install a route back toward OrigAddr.
Similarly, in Route Reply messages, the metric reflects the cost of
the route from TargAddr (and any other addresses included in the
prefix length of RREP_Gen's Router Client entry for TargAddr) to the
router sending the Route Reply. For RREP_Gen, this is the cost
associated with the Router Client entry which includes TargAddr. For
routers which regenerate the RREP, this is the cost from TargAddr to
the regenerating router, combining the metric value from the received
RREP message with knowledge of the link cost from the sender to the
receiver, i.e., the incoming link cost. This updated route cost is
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included when regenerating the Route Reply message, and used to
install a route back toward TargAddr.
Assuming link metrics are symmetric, the cost of the routes installed
in the Local Route Set at each router will be correct. While this
assumption is not always correct, calculating incoming/outgoing
metric data is outside of scope of this document. The route
discovered is optimised for the requesting router, and the return
path may not be the optimal route.
AODVv2 enables the use of multiple metric types. Each route
discovery attempt indicates the metric type which is requested for
the route. Only one metric type MUST be used in each route discovery
attempt.
For each MetricType, AODVv2 requires:
o A MetricType number, to indicate the metric type of a route.
MetricType numbers allocated are detailed in Section 10.5.
o A maximum value, denoted MAX_METRIC[MetricType]. This MUST always
be the maximum expressible metric value of type MetricType. Field
lengths associated with metric values are found in Section 10.5.
If the cost of a route exceeds MAX_METRIC[MetricType], the route
is ignored.
o A function for incoming link cost, denoted Cost(L). Using
incoming link costs means that the route learned has a path
optimized for the direction from OrigAddr to TargAddr.
o A function for route cost, denoted Cost(R).
o A function to analyze routes for potential loops based on metric
information, denoted LoopFree(R1, R2). LoopFree verifies that a
route R2 is not a sub-section of another route R1. An AODVv2
router invokes LoopFree() as part of the process in Section 6.7.1,
when an advertised route (R1) and an existing LocalRoute (R2) have
the same destination address, metric type, and sequence number.
LoopFree returns FALSE to indicate that an advertised route is not
to be used to update a stored LocalRoute, as it may cause a
routing loop. In the case where the existing LocalRoute is
Invalid, it is possible that the advertised route includes the
existing LocalRoute and came from a router which did not yet
receive notification of the route becoming Invalid, so the
advertised route should not be used to update the Local Route Set,
in case it forms a loop to a broken route.
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AODVv2 currently supports cost metrics where Cost(R) is strictly
increasing, by defining:
o Cost(R) := Sum of Cost(L) of each link in the route
o LoopFree(R1, R2) := ( Cost(R1) <= Cost(R2) )
Implementers MAY consider other metric types, but the definitions of
Cost and LoopFree functions for such types are undefined, and
interoperability issues need to be considered.
6. AODVv2 Protocol Operations
The AODVv2 protocol's operations include managing sequence numbers,
monitoring next hop AODVv2 routers on discovered routes and updating
the Neighbor Set, performing route discovery and dealing with
requests from other routers, processing incoming route information
and updating the Local Route Set, updating the Multicast Route
Message Set and suppressing redundant messages, and reporting broken
routes. These processes are discussed in detail in the following
sections.
6.1. Initialization
During initialization where an AODVv2 router does not have
information about its previous sequence number, or if its sequence
number is lost at any point, the router resets its sequence number to
one (1). However, other AODVv2 routers may still hold sequence
number information that this router previously issued. Since
sequence number information is removed if there has been no update to
the sequence number in MAX_SEQNUM_LIFETIME, the initializing router
MUST wait for MAX_SEQNUM_LIFETIME before it creates any messages
containing its new sequence number. It can then be sure that the
information it sends will not be considered stale.
During this wait period, the router is permitted to do the following:
o Process information in a received RREQ or RREP message to learn a
route to the originator or target of that route discovery
o Regenerate a received RREQ or RREP
o Send an RREP_Ack
o Maintain valid routes in the Local Route Set
o Create, process and regenerate RERR messages
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6.2. Next Hop Monitoring
To ensure AODVv2 routers Routers do not establish routes over uni-
directional links, AODVv2 routers MUST verify that the link to the
next hop router is bidirectional before marking a route as valid in
the Local Route Set.
AODVv2 provides a mechanism for testing bidirectional connectivity
during route discovery, and blacklisting routers where bidirectional
connectivity is not available. If a route discovery is retried by
RREQ_Gen, the blacklisted routers can be excluded from the process,
and a different route can be discovered. Further, a route is not to
be used for forwarding until the bidirectionality of the link to the
next hop is confirmed. AODVv2 routers do not need to monitor
bidirectionality for links to neighboring routers which are not used
as next hops on routes in the Local Route Set.
o Bidirectional connectivity to upstream routers is tested by
requesting acknowledgement of RREP messages by including an
AckReq, which MUST be answered by sending an RREP_Ack. Receipt of
an RREP_Ack within RREP_Ack_SENT_TIMEOUT proves that bidirectional
connectivity exists. Otherwise, a link is determined to be
unidirectional. All AODVv2 routers MUST support this process,
which is explained in Section 7.2 and Section 7.3.
o For the downstream router, receipt of an RREP message containing
the route to TargAddr is confirmation of bidirectionality , since
an RREP message is a reply to a RREQ message which previously
crossed the link in the opposite direction.
To assist with next hop monitoring, a Neighbor Set (Section 4.3) is
maintained. When an RREQ or RREP is received, search for an entry in
the Neighbor Set where all of the following conditions are met:
o Neighbor.IPAddress == IP address from which the RREQ or RREP was
received
o Neighbor.Interface == Interface on which the RREQ or RREP was
received.
If such an entry does not exist, a new entry is created as described
in Section 6.3. While the value of Neighbor.State is Unknown,
acknowledgement of RREP messages sent to that neighbor MUST be
requested. If an acknowledgement is not received within the timeout
period, the neighbor MUST have Neighbor.State set to Blacklisted. If
an acknowledgement is received within the timeout period,
Neighbor.State is set to Confirmed. While the value of
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Neighbor.State is Confirmed, the request for an acknowledgement of
any other RREP message is unnecessary.
When routers perform other operations such as those from the list
below, these MAY be used as additional indications of connectivity:
o NHDP HELLO Messages [RFC6130]
o Route timeout
o Lower layer triggers, e.g. message reception or link status
notifications
o TCP timeouts
o Promiscuous listening
o Other monitoring mechanisms or heuristics
If such an external process signals that the link to a neighbor is
bidirectional, the AODVv2 router MAY update the matching Neighbor Set
entry by changing the value of Neighbor.State to Confirmed, e.g.
receipt of a Neighborhood Discovery Protocol HELLO message with the
receiving router listed as a neighbor. If an external process
signals that a link is not bidirectional, the the value of
Neighbor.State MAY be changed to Blacklisted, e.g. notification of a
TCP timeout.
6.3. Neighbor Set Update
On receipt of an RREQ or RREP message, the Neighbor Set MUST be
checked for an entry with Neighbor.IPAddress which matches the source
IP address of a packet containing the AODVv2 message. If no matching
entry is found, a new entry is created.
A new Neighbor Set entry is created as follows:
o Neighbor.IPAddress := Source IP address of the received route
message
o Neighbor.State := Unknown
o Neighbor.ResetTime := INFINITY_TIME
o Neighbor.Interface := Interface on which the RREQ or RREP was
received. MUST equal Interface.Id of one of the entries in the
InterfaceSet (see Section 4.1).
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If the message is one of the following:
o an RREP which answers a RREQ sent within RREQ_WAIT_TIME over the
same interface as Neighbor.Interface
o an RREP_Ack which answers a RREP sent within RREP_Ack_SENT_TIMEOUT
over the same interface as Neighbor.Interface
the link to the neighbor is bidirectional and the Neighbor Set entry
is updated as follows:
o Neighbor.State := Confirmed
o Neighbor.ResetTime := INFINITY_TIME
If the Multicast Route Message Set contains an entry where:
o RteMsg.MessageType == RREP
o RteMsg.AckReqAddr == Neighbor.IPAddress
o RteMsg.Interface == Neighbor.Interface
o RteMsg.Timestamp + RREP_Ack_SENT_TIMEOUT < CurrentTime
the link is considered to be uni-directional and the Neighbor Set
entry is updated as follows:
o Neighbor.State := Blacklisted
o Neighbor.ResetTime := CurrentTime + MAX_BLACKLIST_TIME
When the Neighbor.ResetTime is reached, the Neighbor Set entry is
updated as follows:
o Neighbor.State := Unknown
If an external mechanism reports a link as broken, the Neighbor Set
entry SHOULD be removed.
Route requests from neighbors with Neighbor.State set to Blacklisted
are ignored to avoid persistent IP packet loss or protocol failures.
Neighbor.ResetTime allows the neighbor to again be allowed to
participate in route discoveries after MAX_BLACKLIST_TIME, in case
the link between the routers has become bidirectional.
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6.4. Interaction with the Forwarding Plane
The signals descried in the following are conceptual signals, and can
be implemented in various ways. Conformant implementations of AODVv2
are not mandated to implement the forwarding plane separately from
the control plane or data plane; these signals and interactions are
identified simply as assistance for implementers who may find them
useful.
AODVv2 requires signals from the forwarding plane:
o A packet cannot be forwarded because a route is unavailable:
AODVv2 needs to know the source and destination IP addresses of
the packet. If the source of the packet is configured as a Router
Client, the router should initiate route discovery to the
destination. If it is not a Router Client, the router should
create a Route Error message.
o A packet is to be forwarded: AODVv2 needs to check the state of
the route to ensure it is still valid.
o Packet forwarding succeeds: AODVv2 needs to update the record of
when a route was last used to forward a packet.
o Packet forwarding failure occurs: AODVv2 needs to create a Route
Error message.
AODVv2 needs to send signals to the forwarding plane:
o A route discovery is in progress: buffering might be configured
for packets requiring a route, while route discovery is attempted.
o A route discovery failed: any buffered packets requiring that
route should be discarded, and the source of the packet should be
notified that the destination is unreachable (using an ICMP
Destination Unreachable message). Route discovery fails if an
RREQ cannot be generated because the control message generation
limit has been reached, or if an RREP is not received within
RREQ_WAIT_TIME (see Section 6.6).
o A route discovery is not permitted: any buffered packets requiring
that route should be discarded. A route discovery will not be
attempted if the source address of the packet needing a route is
not configured as a Router Client.
o A route discovery succeeded: install a corresponding route into
the Routing Information Base and begin transmitting any buffered
packets.
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o A route has been made invalid: remove the corresponding route from
the Routing Information Base.
o A route has been updated: update the corresponding route in the
Routing Information Base.
6.5. Message Transmission
AODVv2 sends [RFC5444] formatted messages using the parameters for
port number and IP protocol specified in [RFC5498]. Mapping of
AODVv2 data to [RFC5444] messages is detailed in Section 8. AODVv2
multicast messages are sent to the link-local multicast address LL-
MANET-Routers [RFC5498]. All AODVv2 routers MUST subscribe to LL-
MANET-Routers on all AODVv2 interfaces [RFC5498] to receive AODVv2
messages. Note that multicast messages 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, an AODVv2 router transmitting
a multicast message to LL-MANET-Routers MUST send the message on all
interfaces that have been configured for AODVv2 operation, as given
in the InterfaceSet (Section 4.1).
To avoid congestion, each AODVv2 router's rate of message generation
SHOULD be limited (CONTROL_TRAFFIC_LIMIT) and administratively
configurable. Messages SHOULD NOT be sent more frequently than one
message per (1 / CONTROL_TRAFFIC_LIMIT)th of a second. If this
threshold is reached, messages MUST be sent based on their priority:
o Highest priority SHOULD be given to RREP_Ack messages. This
allows links between routers to be confirmed as bidirectional and
avoids undesired blacklisting of next hop routers.
o Second priority SHOULD be given to RERR messages for undeliverable
IP packets. This avoids repeated forwarding of packets over
broken routes that are still in use by other routers.
o Third priority SHOULD be given to RREP messages in order that
RREQs do not time out.
o Fourth priority SHOULD be given to RREQ messages.
o Fifth priority SHOULD be given to RERR messages for newly
invalidated routes.
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o Lowest priority SHOULD be given to RERR messages generated in
response to RREP messages which cannot be regenerated. In this
case the route request will be retried at a later point.
To implement the congestion control, a queue length is set. If the
queue is full, in order to queue a new message, a message of lower
priority must be removed from the queue. If this is not possible,
the new message MUST be discarded. The queue should be sorted in
order of message priority
6.6. Route Discovery, Retries and Buffering
AODVv2's RREQ and RREP messages are used for route discovery. RREQ
messages are multicast to solicit an RREP, whereas RREP are unicast
where possible. The constants used inSection 6.7.1 this section are
defined in Section 10.
When an AODVv2 router needs to forward an IP packet (with source
address OrigAddr and destination address TargAddr) from one of its
Router Clients, it needs a route to TargAddr in its Routing
Information Base. If no route exists, the AODVv2 router generates
(RREQ_Gen) and multicasts a Route Request message (RREQ), on all
configured interfaces, containing OrigAddr and TargAddr. The
procedure for this is described in Section 7.1.1. Each generated
RREQ results in an increment to the router's sequence number. The
AODVv2 router generating an RREQ is referred to as RREQ_Gen.
Buffering might be configured for IP packets awaiting a route for
forwarding by RREQ_Gen, if sufficient memory is available. Buffering
of IP packets might have both positive and negative effects. Real-
time traffic, voice, and scheduled delivery may suffer if packets are
buffered and subjected to delays, but TCP connection establishment
will benefit if packets are queued while route discovery is performed
[Koodli01]. Recommendations for appropriate buffer methods are out
of scope for this specification. Determining which packets to
discard first when the buffer is full is a matter of policy at each
AODVv2 router. Note that using different or no buffer methods does
not affect interoperability.
RREQ_Gen awaits reception of a Route Reply message (RREP) containing
a route toward TargAddr. This can be achieved by monitoring the
entry in the Multicast Route Message Table that corresponds to the
generated RREP. When CurrentTime exceeds RteMsg.Timestamp +
RREQ_WAIT_TIME and no RREP has been received, RREQ_Gen will retry the
route discovery.
To reduce congestion in a network, repeated attempts at route
discovery for a particular target address utilize a binary
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exponential backoff: for each additional attempt, the time to wait
for receipt of the RREP is multiplied by 2. If the requested route
is not learned within the wait period, another RREQ is sent, up to a
total of DISCOVERY_ATTEMPTS_MAX. This is the same technique used in
AODV [RFC3561].
Through the use of bidirectional link monitoring and blacklists (see
Section 6.2) uni-directional links on initial selected route will be
ignored on subsequent route discovery attempts.
Route discovery is considered to have failed after
DISCOVERY_ATTEMPTS_MAX and the corresponding wait time for an RREP
response to the final RREQ. After the attempted route discovery has
failed, RREQ_Gen waits at least RREQ_HOLDDOWN_TIME before attempting
another route discovery to the same destination, in order to avoid
repeatedly generating control traffic that is unlikely to discover a
route. Any IP packets buffered for TargAddr are also dropped and a
Destination Unreachable ICMP message (Type 3) with a code of 1 (Host
Unreachable Error) is delivered to the source of the packet, so that
the application knows about the failure.
If RREQ_Gen does receive a route message containing a route to
TargAddr within the timeout, it processes the message according to
Section 7. When a valid LocalRoute entry is created in the Local
Route Set, the route is also installed in the Routing Information
Base, and the router will begin sending the buffered IP packets. Any
retry timers for the corresponding RREQ are then cancelled.
During route discovery, all routers on the path learn a route to both
OrigAddr and TargAddr, so that routes are constructed in both
directions. The route is optimized for the forward route.
6.7. Processing Received Route Information
All AODVv2 route messages contain a route. A Route Request (RREQ)
contains a route toward OrigAddr (and other addresses as indicated by
OrigPrefixLen), and a Route Reply (RREP) contains a route toward
TargAddr (and other addresses as indicated by TargPrefixLen). All
AODVv2 routers that receive a route message are able to store the
route contained within it in their Local Route Set. Incoming
information is first checked to verify that it is both safe to use
and offers an improvement to existing information, as explained in
Section 6.7.1. If these checks pass, the Local Route Set MUST be
updated according to Section 6.7.2.
In the processes below, RteMsg is used to denote the route message,
AdvRte is used to denote the route contained within it, and
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LocalRoute denotes an existing entry in the Local Route Set which
matches AdvRte on address, prefix length, and metric type.
AdvRte has the following properties:
o AdvRte.Address := network address given by combining
RteMsg.OrigAddr and RteMsg.OrigPrefixLen (in RREQ) or
RteMsg.TargAddr and RteMsg.TargPrefixLen (in RREP)
o AdvRte.PrefixLength := RteMsg.OrigPrefixLen (in RREQ) or
RteMsg.TargPrefixLen (in RREP). If no prefix length was included
in RteMsg, prefix length is the address length, in bits, of
RteMsg.OrigAddr (in RREQ) or RteMsg.TargAddr (in RREP)
o AdvRte.SeqNum := RteMsg.OrigSeqNum (in RREQ) or RteMsg.TargSeqNum
(in RREP)
o AdvRte.NextHop := RteMsg.IPSourceAddress (an address of the
sending interface of the router from which the RteMsg was
received)
o AdvRte.MetricType := RteMsg.MetricType
o AdvRte.Metric := RteMsg.Metric
o AdvRte.Cost := Cost(R) using the cost function associated with the
route's metric type, i.e. Cost(R) = AdvRte.Metric + Cost(L), as
described in Section 5, where L is the link from the advertising
router
o AdvRte.ValidityTime := RteMsg.ValidityTime, if included
6.7.1. Evaluating Route Information
An incoming advertised route (AdvRte) is compared to existing
LocalRoutes to determine whether the advertised route is to be used
to update the AODVv2 Local Route Set. The incoming route information
MUST be processed as follows:
1. Search for LocalRoutes in the Local Route Set matching AdvRte's
address, prefix length and metric type
* If no matching LocalRoute exists, AdvRte MUST be used to
update the Local Route Set and no further checks are required.
* If matching LocalRoutes are found, continue to Step 2.
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2. Compare sequence numbers using the technique described in
Section 4.4
* If AdvRte is more recent than all matching LocalRoutes, AdvRte
MUST be used to update the Local Route Set and no further
checks are required.
* If AdvRte is stale, AdvRte MUST NOT be used to update the
Local Route Set. Ignore AdvRte for further processing.
* If the sequence numbers are equal, continue to Step 3.
3. Check that AdvRte is safe against routing loops compared to all
matching LocalRoutes (see Section 5)
* If LoopFree(AdvRte, LocalRoute) returns FALSE, ignore AdvRte
for further processing. AdvRte MUST NOT be used to update the
Local Route Set because using the incoming information might
cause a routing loop.
* If LoopFree(AdvRte, LocalRoute) returns TRUE, continue to Step
4.
4. Compare route costs
* If AdvRte is better than all matching LocalRoutes, it SHOULD
be used to update the Local Route Set because it offers
improvement. If it is not used to update the Local Route Set,
the existing non-optimal LocalRoute will continue to be used,
causing data traffic to use a non-optimal route.
* If AdvRte is equal in cost and LocalRoute is valid, AdvRte
SHOULD NOT be used to update the Local Route Set because it
will offer no improvement.
* If AdvRte is worse and LocalRoute is valid, ignore AdvRte for
further processing. AdvRte MUST NOT be used to update the
Local Route Set because it does not offer any improvement.
* If AdvRte is not better (i.e., it is worse or equal) but
LocalRoute is Invalid, AdvRte SHOULD be used to update the
Local Route Set because it can safely repair the existing
Invalid LocalRoute.
If the advertised route is to be used to update the Local Route Set,
the procedure in Section 6.7.2 MUST be followed. If not, non-optimal
routes will remain in the Local Route Set.
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For information on how to apply these changes to the Routing
Information Base, see Section 4.5.
6.7.2. Applying Route Updates
After determining that AdvRte is to be used to update the Local Route
Set (as described in Section 6.7.1), the following procedure applies.
If AdvRte is learned from an RREQ message, the link to the next hop
neighbor may not be confirmed as bidirectional (see Section 4.3).
The route will offer improvement to the Local Route Set if the
neighbor can be confirmed. If there is no existing matching route,
AdvRte allows a corresponding RREP to be sent. If a matching entry
already exists, AdvRte offers potential improvement.
The route update is applied as follows:
1. If no existing entry in the Local Route Set matches AdvRte's
address, prefix length and metric type, continue to Step 4 and
create a new entry in the Local Route Set.
2. If two matching LocalRoutes exist in the Local Route Set, one is
a valid route, and one is an Unconfirmed route, AdvRte may offer
further improvement to the Unconfirmed route, or may offer an
update to the valid route.
* If AdvRte.NextHop's Neighbor.State is Unknown, the advertised
route may offer improvement to the existing valid route, if
the link to the next hop can be confirmed as bidirectional.
Continue processing from Step 5 to update the existing
Unconfirmed LocalRoute.
* If AdvRte.NextHop's Neighbor.State is Confirmed, the
advertised route offers an update or improvement to the
existing valid route. Continue processing from Step 5 to
update the existing valid LocalRoute.
3. If only one matching LocalRoute exists in the Local Route Set:
* If AdvRte.NextHop's Neighbor.State is Confirmed, continue
processing from Step 5 to update the existing LocalRoute.
* If AdvRte.NextHop's Neighbor.State is Unknown, AdvRte may
offer improvement the existing LocalRoute, if the link to
AdvRte.NextHop can be confirmed as bidirectional.
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* If LocalRoute.State is Unconfirmed, AdvRte is an improvement
to an existing Unconfirmed route. Continue processing from
Step 5 to update the existing LocalRoute.
* If LocalRoute.State is Invalid, AdvRte can replace the
existing LocalRoute. Continue processing from Step 5 to
update the existing LocalRoute.
* If LocalRoute.State is Active or Idle, AdvRte SHOULD be stored
as an additional entry in the Local Route Set, with
LocalRoute.State set to Unconfirmed. Continue processing from
Step 4 to create a new LocalRoute.
4. Create an entry in the Local Route Set and initialize as follows:
* LocalRoute.Address := AdvRte.Address
* LocalRoute.PrefixLength := AdvRte.PrefixLength
* LocalRoute.MetricType := AdvRte.MetricType
5. Update the LocalRoute as follows:
* LocalRoute.SeqNum := AdvRte.SeqNum
* LocalRoute.NextHop := AdvRte.NextHop
* LocalRoute.NextHopInterface := interface on which RteMsg was
received
* LocalRoute.Metric := AdvRte.Cost
* LocalRoute.LastUsed := CurrentTime
* LocalRoute.LastSeqNumUpdate := CurrentTime
* LocalRoute.ExpirationTime := CurrentTime + AdvRte.ValidityTime
if a validity time exists, otherwise INFINITY_TIME
6. If a new LocalRoute was created, or if the existing
LocalRoute.State is Invalid or Unconfirmed, update LocalRoute as
follows:
* LocalRoute.State := Unconfirmed (if the next hop's
Neighbor.State is Unknown)
* LocalRoute.State := Idle (if the next hop's Neighbor.State is
Confirmed)
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7. If an existing LocalRoute.State changed from Invalid or
Unconfirmed to become Idle, any matching Unconfirmed LocalRoute
with worse metric value SHOULD be expunged.
8. If an existing LocalRoute was updated with a better metric value,
any matching Unconfirmed LocalRoute with worse metric value
SHOULD be expunged.
9. If this update results in LocalRoute.State of Active or Idle,
which matches a route request which is still in progress, the
associated route request retry timers SHOULD be cancelled.
If this update to the Local Route Set results in two LocalRoutes to
the same address, the best LocalRoute will be Unconfirmed. In order
to improve the route used for forwarding, the router SHOULD try to
determine if the link to the next hop of that LocalRoute is
bidirectional, by using that LocalRoute to forward future RREPs and
request acknowledgements (see Section 7.2.1).
6.8. Suppressing Redundant Messages Using the Multicast Route Message
Set
When route messages are flooded in a MANET, an AODVv2 router may
receive multiple similar messages. Regenerating every one of these
gives little additional benefit, and generates unnecessary signaling
traffic and might generate unnecessary interference.
Each AODVv2 router stores information about recently received route
messages in the AODVv2 Multicast Route Message Set (Section 4.6).
Entries in the Multicast Route Message Set SHOULD be maintained for
at least RteMsg_ENTRY_TIME after the last Timestamp update in order
to account for long-lived RREQs traversing the network. An entry
MUST be deleted when the sequence number is no longer valid, i.e.,
after MAX_SEQNUM_LIFETIME. Memory-constrained devices MAY remove the
entry before this time.
Received route messages are tested against previously received route
messages, and if determined to be redundant, regeneration or response
can be avoided.
To determine if a received message is redundant:
1. Search for an entry in the Multicast Route Message Set with the
same MessageType, OrigAddr, TargAddr, Interface and MetricType
* If there is no entry, the message is not redundant.
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* If there is an entry, continue to Step 2.
2. Compare sequence numbers using the technique described in
Section 4.4
* For RREQ messages, use OrigSeqNum of the entry for comparison.
For RREP messages, use TargSeqNum of the entry for comparison.
* If the entry has an older sequence number than the received
message, the message is not redundant.
* If the entry has a newer sequence number than the received
message, the message is redundant.
* If the entry has the same sequence number, continue to Step 3.
3. Compare the metric values
* If the entry has a Metric value that is worse than or equal to
the metric in the received message, the message is redundant.
* If the entry has a Metric value that is better than the metric
in the received message, the message is not redundant.
If the message is redundant, update the Timestamp and RemoveTime on
the entry, since matching route messages are still traversing the
network and this entry should be maintained. This message MUST NOT
be regenerated or responded to.
If the message is not redundant, create an entry or update the
existing entry.
To update a Multicast Route Message Set entry, set:
o RteMsg.MessageType := the message type of the received message
o RteMsg.OrigAddr := OrigAddr from the message
o RteMsg.OrigPrefixLen := the prefix length associated with OrigAddr
o RteMsg.TargAddr := TargAddr from the message
o RteMsg.TargPrefixLen := the prefix length associated with TargAddr
o RteMsg.OrigSeqNum := the sequence number associated with OrigAddr,
if present in the received message
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o RteMsg.TargSeqNum := the sequence number associated with TargAddr,
if present in the received message
o RteMsg.Metric := the metric value associated with OrigAddr in a
received RREQ or TargAddr in a received RREP
o RteMsg.MetricType := the metric type associated with RteMsg.Metric
o RteMsg.Timestamp := CurrentTime
o RteMsg.RemoveTime := CurrentTime + MAX_SEQNUM_LIFETIME
Where the message is determined not redundant before Step 3, it MUST
be regenerated or responded to. When a message is determined to be
not redundant in Step 3, it MAY be suppressed to avoid extra control
traffic. However, since the processing of the message will result in
an update to the Local Route Set, the message SHOULD be regenerated
or responded to, to ensure other routers have up-to-date information
and the best metrics. If the message is not regenerated, the best
route may not be found. Regeneration or response is to be performed
using the processes outlined in Section 7.
6.9. Suppressing Redundant Route Error Messages using the Route Error
Set
In order to avoid flooding the network with RERR messages when a
stream of IP packets to an unreachable address arrives, an AODVv2
router SHOULD avoid creating duplicate messages by determining
whether an equivalent RERR has recently been sent. This is achieved
with the help of the Route Error Set (see Section 4.7).
To determine if a received RERR is redundant:
1. Search for an entry in the Route Error Set where:
* RerrMsg.AddressList == RERR.AddressList
* RerrMsg.PktSource == RERR.PktSource
If a matching entry is found, no further processing is required
and the RERR SHOULD NOT be sent.
2. If no matching entry is found, a new entry with the following
properties is created:
* RerrMsg.Timeout := CurrentTime + RERR_TIMEOUT
* RerrMsg.AddressList == RERR.AddressList
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* RerrMsg.PktSource == RERR.PktSource
6.10. Local Route Set Maintenance
Route maintenance involves monitoring LocalRoutes in the Local Route
Set, updating LocalRoute.State to handle route timeouts and reporting
routes that become Invalid.
6.10.1. LocalRoute State Changes
During normal operation, AODVv2 does not require any explicit
timeouts to manage the lifetime of a route. At any time, any
LocalRoute MAY be examined and updated according to the rules below.
If timers are not used to prompt updates of LocalRoute.State, the
LocalRoute.State MUST be checked before IP packet forwarding and
before any operation based on LocalRoute.State.
Route timeout behaviour is as follows:
o An Unconfirmed route MUST be expunged at MAX_SEQNUM_LIFETIME after
LocalRoute.LastSeqNumUpdate.
o An Idle route MUST become Active when used to forward an IP
packet. If the route is not used to forward an IP packet within
MAX_IDLETIME, LocalRoute.State MUST become Invalid.
o An Active route which is a timed route (i.e., with
LocalRoute.ExpirationTime not equal to INFINITY_TIME) remains
Active until LocalRoute.ExpirationTime, after which it MUST become
Invalid. If it it not a timed route, it MUST become Idle if the
route is not used to forward an IP packet within ACTIVE_INTERVAL.
o An Invalid route SHOULD remain in the Local Route Set, since
LocalRoute.SeqNum is used to classify future information about
LocalRoute.Address as stale or fresh.
o In all cases, if the time since LocalRoute.LastSeqNumUpdate
exceeds MAX_SEQNUM_LIFETIME, LocalRoute.SeqNum must be set to
zero. This is required to ensure that any AODVv2 routers
following the initialization procedure can safely begin routing
functions using a new sequence number. A LocalRoute with
LocalRoute.State set to Active or Idle can remain in the Local
Route Set after removing the sequence number, for exmple if the
route is reliably carrying traffic. If LocalRoute.State is
Invalid, or later becomes Invalid, the LocalRoute MUST be expunged
from the Local Route Set.
LocalRoutes can become Invalid before a timeout occurs:
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o If an external mechanism reports a link as broken, all LocalRoutes
using that link for LocalRoute.NextHop MUST immediately have
LocalRoute.State set to Invalid.
o LocalRoute.State MUST immediately be set to Invalid if a Route
Error (RERR) message is received where:
* The sender is LocalRoute.NextHop or PktSource is a Router
Client address
* There is an Address in AddressList which matches
LocalRoute.Address, and:
+ The prefix length associated with this Address, if any,
matches LocalRoute.PrefixLength
+ The sequence number associated with this Address, if any, is
newer or equal to LocalRoute.SeqNum (see Section 4.4)
+ The metric type associated with this Address matches
LocalRoute.MetricType
LocalRoutes are also updated when Neighbor.State is updated:
o While the value of Neighbor.State is set to Unknown, any routes in
the Local Route Set using that neighbor as a next hop MUST have
LocalRoute.State set to Unconfirmed.
o When the value of Neighbor.State is set to Confirmed, the
Unconfirmed routes in the Local Route Set using that neighbor as a
next hop MUST have LocalRoute.State set to Idle. Any other
matching LocalRoutes with metric values worse than
LocalRoute.Metric MUST be expunged from the Local Route Set.
o When the value of Neighbor.State is set to Blacklisted, any valid
routes in the Local Route Set using that neighbor for their next
hop MUST have LocalRoute.State set to Invalid.
o When a Neighbor Set entry is removed, all routes in the Local
Route Set using that neighbor as next hop MUST have
LocalRoute.State set to Invalid.
Memory constrained devices MAY choose to expunge routes from the
AODVv2 Local Route Set before LocalRoute.ExpirationTime, but MUST
adhere to the following rules:
o An Active route MUST NOT be expunged, as it is in use. If
deleted, IP traffic forwarded to this router will prompt
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generation of a Route Error message, and it will be necessary for
a Route Request to be generated by the originator's router to re-
establish the route.
o An Idle route SHOULD NOT be expunged, as it is still valid for
forwarding IP traffic. If deleted, this could result in dropped
IP packets and a Route Request could be generated to re-establish
the route.
o Any Invalid route MAY be expunged. Least recently used Invalid
routes SHOULD be expunged first, since the sequence number
information is less likely to be useful.
o An Unconfirmed route MUST NOT be expunged if it was installed
within the last RREQ_WAIT_TIME, because it may correspond to a
route discovery in progress. A Route Reply message might be
received which needs to use the LocalRoute.NextHop information.
Otherwise, it MAY be expunged.
6.10.2. Reporting Invalid Routes
When LocalRoute.State changes from Active to Invalid as a result of a
broken link or a received Route Error (RERR) message, other AODVv2
routers MUST be informed by sending an RERR message containing
details of the invalidated route.
An RERR message MUST also be sent when an AODVv2 router receives an
IP packet to forward on behalf of another router but does not have a
valid route in its Routing Information Base for the destination of
the packet.
An RERR message MUST also be sent when an AODVv2 router receives an
RREP message to regenerate, but the LocalRoute to the OrigAddr in the
RREP has been lost or is marked as Invalid.
The packet or message triggering the RERR MUST be discarded.
Generation of an RERR message is described in Section 7.4.1.
7. AODVv2 Protocol Messages
AODVv2 defines four message types: Route Request (RREQ), Route Reply
(RREP), Route Reply Acknowledgement (RREP_Ack), and Route Error
(RERR).
Each AODVv2 message is defined as a set of data. Rules for the
generation, reception and regeneration of each message type are
described in the following sections. Section 8 discusses how the
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data is mapped to [RFC5444] Message TLVs, Address Blocks, and Address
TLVs.
7.1. Route Request (RREQ) Message
Route Request messages are used in route discovery operations to
request a route to a specified target address. RREQ messages have
the following contents:
+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| OrigSeqNum, (optional) TargSeqNum |
+-----------------------------------------------------------------+
| MetricType |
+-----------------------------------------------------------------+
| OrigMetric |
+-----------------------------------------------------------------+
| ValidityTime (optional) |
+-----------------------------------------------------------------+
Figure 1: RREQ message contents
AddressList
Contains OrigAddr and TargAddr, the source and destination
addresses of the IP packet for which a route is requested.
OrigAddr and TargAddr MUST be routable unicast addresses.
PrefixLengthList
Contains OrigPrefixLen, i.e., the length, in bits, of the prefix
associated with the Router Client entry which includes OrigAddr.
If omitted, the prefix length is equal to OrigAddr's address
length in bits.
OrigSeqNum
The sequence number associated with OrigAddr.
TargSeqNum
A sequence number associated with an existing Invalid route to
TargAddr. This MAY be included if available.
MetricType
The metric type associated with OrigMetric.
OrigMetric
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The metric value associated with the LocalRoute to OrigAddr (and
to any other addresses included in the given prefix length), as
seen from the sender of the message.
ValidityTime
The length of time that the message sender is willing to offer a
route toward OrigAddr (and any other addresses included in the
given prefix length). Omitted if no time limit is imposed.
7.1.1. RREQ Generation
An RREQ is generated when an IP packet needs to be forwarded for a
Router Client, and no valid route currently exists for the packet's
destination in the Routing Information Base.
Before creating an RREQ, the router SHOULD check the Multicast Route
Message Set to see if an RREQ has recently been sent for the
requested destination. If so, and the wait time for a reply has not
yet been reached, the router SHOULD continue to await a response
without generating a new RREQ. If the timeout has been reached, a
new RREQ MAY be generated. If buffering is configured, incoming IP
packets awaiting this route SHOULD be buffered until the route
discovery is completed.
If the limit for the rate of AODVv2 control message generation has
been reached, no message SHOULD be generated.
To generate the RREQ, the router (referred to as RREQ_Gen) follows
this procedure:
1. Set AddressList := {OrigAddr, TargAddr}
2. For the PrefixLengthList:
* If OrigAddr is part of an address range configured as a Router
Client, set PrefixLengthList := {RouterClient.PrefixLength,
null}. This allows receiving routers to learn a route to all
the addresses included by the prefix length, not only to
OrigAddr.
* Otherwise, omit PrefixLengthList.
3. For OrigSeqNum:
* Increment the router SeqNum as specified in Section 4.4.
* Set OrigSeqNum := SeqNum.
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4. For TargSeqNum:
* If an Invalid route exists in the Local Route Set matching
TargAddr using longest prefix matching and has a valid
sequence number, set TargSeqNum := LocalRoute.SeqNum.
* If no Invalid route exists in the Local Route Set matching
TargAddr, or the route doesn't have a sequence number, omit
TargSeqNum.
5. Include MetricType and set the type accordingly
6. Set OrigMetric := RouterClient.Cost for the Router Client entry
which includes OrigAddr
7. Include ValidityTime if advertising that the route to OrigAddr
(and any other addresses included in the given prefix length) via
this router is offered for a limited time, and set ValidityTime
accordingly
This AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8) which is handed to the RFC5444 multiplexer
for further processing. By default, the multiplexer is instructed to
multicast the message to LL-MANET- Routers on all interfaces
configured for AODVv2 operation.
7.1.2. RREQ Reception
Upon receiving a Route Request, an AODVv2 router performs the
following steps:
1. Check and update the Neighbor Set according to Section 6.3
* If the sender has Neighbor.State set to Blacklisted, ignore
this RREQ for further processing.
2. Verify that the message contains the required data: OrigAddr,
TargAddr, OrigSeqNum, and OrigMetric, and that OrigAddr and
TargAddr are valid addresses (routable and unicast)
* If not, ignore this RREQ for further processing.
3. Check that the MetricType is supported and configured for use
* If not, ignore this RREQ for further processing.
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4. Verify that the cost of the advertised route will not exceed the
maximum allowed metric value for the metric type (Metric <=
MAX_METRIC[MetricType] - Cost(L))
* If it will, ignore this RREQ for further processing.
5. Process the route to OrigAddr (and any other addresses included
in the given prefix length) as specified in Section 6.7
6. Check if the information in the message is redundant by comparing
to entries in the Multicast Route Message Set, following the
procedure in Section 6.8
* If redundant, ignore this RREQ for further processing.
* If not redundant, continue processing.
7. Check if the TargAddr belongs to one of the Router Clients
* If so, generate an RREP as specified in Section 7.2.1.
* If not, continue to RREQ regeneration.
7.1.3. RREQ Regeneration
By regenerating an RREQ, a router advertises that it will forward IP
packets to the OrigAddr contained in the RREQ (and to other addresses
included in the given prefix length) according to the information
enclosed. The router MAY choose not to regenerate the RREQ, for
example if the router is heavily loaded or low on energy and
therefore unwilling to advertise routing capability for more traffic.
This could, however, decrease connectivity in the network or result
in non-optimal paths.
The RREQ SHOULD NOT be regenerated if the limit for the rate of
AODVv2 control message generation has been reached.
The procedure for RREQ regeneration is as follows:
1. Set AddressList, PrefixLengthList, sequence numbers and
MetricType to the values in the received RREQ
2. Set OrigMetric := LocalRoute[OrigAddr].Metric
3. If the received RREQ contains a ValidityTime, or if the
regenerating router wishes to limit the time that it offers a
route to OrigAddr (and any other addresses included in the given
prefix length), the regenerated RREQ MUST include ValidityTime
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* The ValidityTime is either the time limit the previous AODVv2
router specified, or the time limit this router wishes to
impose, whichever is lower.
This AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8) which is handed to the RFC5444 multiplexer
for further processing. By default, the multiplexer is instructed to
multicast the message to LL-MANET-Routers on all interfaces
configured for AODVv2 operation. However, the regenerated RREQ can
be unicast to the next hop address of the LocalRoute toward TargAddr,
if known.
7.2. Route Reply (RREP) Message
When a Route Request message is received, requesting a route to a
target address (TargAddr) which is configured as part of a Router
Client entry, a Route Reply message is sent in response. The RREP
offers a route to TargAddr (and any other addresses included in the
prefix length).
RREP messages have the following contents:
+-----------------------------------------------------------------+
| AckReq (optional) |
+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| TargSeqNum |
+-----------------------------------------------------------------+
| MetricType |
+-----------------------------------------------------------------+
| TargMetric |
+-----------------------------------------------------------------+
| ValidityTime (optional) |
+-----------------------------------------------------------------+
Figure 2: RREP message contents
AckReq
The address of the intended next hop of the RREP. This is
included when the link to the next hop toward OrigAddr is not
known to be bidirectional. It indicates that an acknowledgement
of the RREP is requested by the sender from the intended next hop
(see Section 6.2).
AddressList
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Contains OrigAddr and TargAddr, the source and destination
addresses of the IP packet for which a route is requested.
OrigAddr and TargAddr MUST be routable unicast addresses.
PrefixLengthList
Contains TargPrefixLen, i.e., the length, in bits, of the prefix
associated with the Router Client entry which includes TargAddr.
If omitted, the prefix length is equal to TargAddr's address
length, in bits.
TargSeqNum
The sequence number associated with TargAddr.
MetricType
The metric type associated with TargMetric.
TargMetric
The metric value associated with the LocalRoute to TargAddr (and
any other addresses included in the given prefix length), as seen
from the sender of the message.
ValidityTime
The length of time that the message sender is willing to offer a
route toward TargAddr (and any other addresses included in the
given prefix length). Omitted if no time limit is imposed.
7.2.1. RREP Generation
A Route Reply message is generated when a Route Request for a Router
Client of the AODVv2 router arrives. This is the case when
RteMsg.TargAddr matches an address which is configured as a Router
Client of the AODVv2 router.
Before creating an RREP, the router SHOULD check if the corresponding
RREQ is redundant, i.e., a Route Reply has already been generated in
response to the RREQ, or if the limit for the rate of AODVv2 control
message generation has been reached. If so, the RREP SHOULD NOT be
created.
The RREP will follow the path of the route to OrigAddr. If the best
route to OrigAddr in the Local Route Set is Unconfirmed, the link to
the next hop neighbor is not yet confirmed as bidirectional (as
described in Section 6.2). In this case the RREP MUST include AckReq
set to the intended next hop address. The AckReq indicates that an
acknowledgement to the RREP is requested from the intended next hop
router in the form of a Route Reply Acknowledgement (RREP_Ack). If
the best route to OrigAddr in the Local Route Set is valid, the link
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to the next hop neighbor is already confirmed as bidirectional, and
the AckReq can be omitted.
Implementations MAY allow a number of retries of the RREP if a
requested acknowledgement is not received within
RREP_Ack_SENT_TIMEOUT, doubling the timeout with each retry, up to a
maximum of RREP_RETRIES, using the same exponential backoff described
in Section 6.6 for RREQ retries. The acknowledgement MUST be
considered to have failed after the wait time for an RREP_Ack
response to the final RREP.
To generate the RREP, the router (also referred to as RREP_Gen)
follows this procedure:
1. If the link to the next hop router toward OrigAddr is not known
to be bidirectional, include the AckReq with the address of the
intended next hop router (see Section 8.2.3)
2. Set Address List := {OrigAddr, TargAddr}
3. For the PrefixLengthList:
* If TargAddr is part of an address range configured as a Router
Client, set PrefixLengthList := {null,
RouterClient.PrefixLength}. This allows receiving routers to
learn a route to all the addresses included by the prefix
length, not only to TargAddr.
* Otherwise, omit PrefixLengthList.
4. For the TargSeqNum:
* Increment the router SeqNum as specified in Section 4.4.
* Set TargSeqNum := SeqNum.
5. Include MetricType and set the type to match the MetricType in
the received RREQ message
6. Set TargMetric := RouterClient.Cost for the Router Client entry
which includes TargAddr
7. Include ValidityTime if advertising that the route to TargAddr
(and any other addresses included in the given prefix length) via
this router is offered for a limited time, and set ValidityTime
accordingly
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This AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8) which is handed to the RFC5444 multiplexer
for further processing. If the Neighbor Set contains an entry for
the neighbor stored as LocalRoute[OrigAddr].NextHop, with
Neighbor.State set to Confirmed, the multiplexer is instructed to
unicast the RREP to LocalRoute[OrigAddr].NextHop. Otherwise, it
multicasts the RREP to LL-MANET-Routers. The RREP MUST be sent over
the same interface on which the RREQ that triggered it was received.
7.2.2. RREP Reception
Upon receiving a Route Reply, an AODVv2 router performs the following
steps:
1. Verify that the message contains the required data: OrigAddr,
TargAddr, TargSeqNum, and TargMetric, and that OrigAddr and
TargAddr are valid addresses (routable and unicast)
* If not, ignore this RREP for further processing.
2. Check that the MetricType is supported and configured for use
* If not, ignore this RREP for further processing.
3. If this RREP does not correspond to a RREQ generated or
regenerated in the last RREQ_WAIT_TIME, ignore for further
processing.
4. Update the Neighbor Set according to Section 6.3
5. Verify that the cost of the advertised route does not exceed the
maximum allowed metric value for the metric type (Metric <=
MAX_METRIC[MetricType] - Cost(L))
* If it does, ignore this RREP for further processing.
6. If the AckReq is present, check the intended recipient of the
received RREP:
* If there is an entry in the Router Client Set where
RouterClient.IPAddress matches the address associated with
the AckReq (see Section 8.2.3), the receiving router is the
intended recipient. Send an acknowledgement as specified in
Section 7.3 and continue processing.
* Otherwise, ignore this RREP for further processing.
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7. Process the route to TargAddr (and any other addresses included
in the given prefix length) as specified in Section 6.7
8. Check if the message is redundant by comparing to entries in the
Multicast Route Message Set (Section 6.8)
* If redundant, ignore this RREP for further processing.
* If not redundant, save the information in the Multicast Route
Message Set to identify future redundant RREP messages and
continue processing.
9. Check if the OrigAddr belongs to one of the Router Clients
* If so, no further processing is necessary.
* If not, continue to Step 10.
10. Check if a valid (Active or Idle) or Unconfirmed LocalRoute
exists to OrigAddr
* If so, continue to RREP regeneration.
* If not, a Route Error message SHOULD be transmitted to
TargAddr according to Section 7.4.1 and the RREP SHOULD be
discarded and not regenerated.
7.2.3. RREP Regeneration
A received Route Reply message is regenerated toward OrigAddr. By
regenerating a RREP, a router advertises that it will forward IP
packets to TargAddr.
The RREP SHOULD NOT be regenerated if CONTROL_TRAFFIC_LIMIT has been
reached. Otherwise, the router MUST regenerate the RREP.
The procedure for RREP regeneration is as follows:
1. If the link to the next hop router toward OrigAddr is not known
to be bidirectional, include the AckReq with the address of the
intended next hop router
2. Set AddressList, PrefixLengthList, TargSeqNum and MetricType to
the values in the received RREP
3. Set TargMetric := LocalRoute[TargAddr].Metric
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4. If the received RREP contains a ValidityTime, or if the
regenerating router wishes to limit the time that it will offer a
route to TargAddr (and any other addresses included in the given
prefix length), the regenerated RREP MUST include ValidityTime
* The ValidityTime is either the time limit the previous AODVv2
router specified, or the time limit this router wishes to
impose, whichever is lower.
This AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8) which is handed to the RFC5444 multiplexer
for further processing. If the Neighbor Set contains an entry for
the neighbor stored as LocalRoute[OrigAddr].NextHop, with
Neighbor.State set to Confirmed, the multiplexer is instructed to
unicast the RREP to LocalRoute[OrigAddr].NextHop. Otherwise, it
multicasts the RREP to LL-MANET-Routers. The RREP MUST be sent over
LocalRoute[OrigAddr].NextHopInterface.
7.3. Route Reply Acknowledgement (RREP_Ack) Message
The Route Reply Acknowledgement is a response to a Route Reply
message. When the RREP_Ack message is received by the sender of the
RREP, it confirms that the link between the two routers is
bidirectional (see Section 6.2). The RREP_Ack has no further data.
7.3.1. RREP_Ack Generation
An RREP_Ack MUST be generated if a received Route Reply includes an
AckReq with an address matching one of the receiving router's IP
addresses. The RREP_Ack SHOULD NOT be generated if the limit for the
rate of AODVv2 control message generation has been reached.
There is no further data in an RREP_Ack. The [RFC5444]
representation is discussed in Section 8. The RREP_Ack is unicast,
by default, to the source IP address of the RREP message that
requested it. It MUST be sent over the same interface on which the
RREP that triggered it was received.
7.3.2. RREP_Ack Reception
Upon receiving an RREP_Ack, an AODVv2 router performs the following
steps:
1. Check if the RREP_Ack was expected:
* Check if the Multicast Route Message Set contains an entry
where:
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+ RteMsg.MessageType == RREP
+ RteMsg.AckReqAddr matches the source IP address of the
RREP_Ack
+ RteMsg.Timestamp > CurrentTime - RREP_Ack_SENT_TIMEOUT
+ RteMsg.Interface matches the interface on which the
RREP_Ack was received
* If it does, the router cancels any associated timeouts and
processing continues to Step 2.
* Otherwise no actions are required and processing ends.
2. Update the Neighbor Set according to Section 6.3
7.4. Route Error (RERR) Message
A Route Error message is generated by an AODVv2 router to notify
other AODVv2 routers of routes that are no longer available. An RERR
message has the following contents:
+-----------------------------------------------------------------+
| PktSource (optional) |
+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| SeqNumList (optional) |
+-----------------------------------------------------------------+
| MetricTypeList |
+-----------------------------------------------------------------+
Figure 3: RERR message contents
PktSource
The source address of the IP packet triggering the RERR. If the
RERR is triggered by a broken link, PktSource is not required.
AddressList
The addresses of the routes not available through RERR_Gen.
PrefixLengthList
The prefix lengths, in bits, associated with the routes not
available through RERR_Gen. These values indicate whether routes
represent a single device or an address range.
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SeqNumList
The sequence numbers of the routes not available through RERR_Gen
(where known).
MetricTypeList
The metric types associated with the routes not available through
RERR_Gen.
7.4.1. RERR Generation
A Route Error message is generated when an AODVv2 router (also
referred to as RERR_Gen) needs to report that a destination is not
reachable. There are three events that cause this response:
o When an IP packet that has been forwarded from another router, but
cannot be forwarded further because there is no valid route in the
Routing Information Base for its destination, the source of the
packet needs to be informed that the route to the destination of
the packet does not exist. The RERR generated MUST include
PktSource set to the source address of the IP packet, and MUST
contain only one unreachable address in the AddressList, i.e., the
destination address of the IP packet. RERR_Gen MUST discard the
IP packet that triggered generation of the RERR. The prefix
length, sequence number and metric type SHOULD be included if
known from an existing Invalid LocalRoute to the unreachable
address.
o When an RREP message cannot be regenerated because the LocalRoute
to OrigAddr has been lost or is Invalid, RREP_Gen needs to be
informed that the route to OrigAddr does not exist. The RERR
generated MUST include PktSource set to the TargAddr of the RREP,
and MUST contain only one unreachable address in the AddressList,
the OrigAddr from the RREP. RERR_Gen MUST discard the RREP
message that triggered generation of the RERR. The prefix length,
sequence number and metric type SHOULD be included if known from
an Invalid LocalRoute to the unreachable address.
o When a link breaks, multiple LocalRoutes may become Invalid, and
the RERR generated MAY contain multiple unreachable addresses.
The RERR MUST include MetricTypeList. PktSource is omitted. All
previously Active LocalRoutes that used the broken link MUST be
reported. The AddressList, PrefixLengthList, SeqNumList, and
MetricTypeList will contain entries for each LocalRoute which has
become Invalid. An RERR message is only sent if an Active
LocalRoute becomes Invalid, though an AODVv2 router can also
include Idle LocalRoutes that become Invalid if the configuration
parameter ENABLE_IDLE_IN_RERR is set (see Section 10.3).
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The RERR SHOULD NOT be generated if CONTROL_TRAFFIC_LIMIT has been
reached. The RERR also SHOULD NOT be generated if it is a duplicate,
as determined by Section 6.9.
Incidentally, if an AODVv2 router receives an ICMP error packet to or
from the address of one of its Router Clients, it forwards the ICMP
packet in the same way as any other IP packet, and will not generate
any RERR message based on the contents of the ICMP packet.
To generate the RERR, the router follows this procedure:
1. If necessary, include PktSource and set the value as given above
2. For each LocalRoute that needs to be reported:
* Insert LocalRoute.Address into the AddressList.
* Insert LocalRoute.PrefixLength into PrefixLengthList, if known
and not equal to the address length.
* Insert LocalRoute.SeqNum into SeqNumList, if known.
* Insert LocalRoute.MetricType into MetricTypeList.
The AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8).
If the RERR is sent in response to an undeliverable IP packet or RREP
message, i.e., if PktSource is included, the RERR SHOULD be sent
unicast to the next hop on the route to PktSource. It MUST be sent
over the same interface on which the undeliverable IP packet was
received. If there is no route to PktSource, the RERR SHOULD be
multicast to LL-MANET-Routers. If the RERR is sent in response to a
broken link, i.e., PktSource is not included, the RERR is, by
default, multicast to LL-MANET-Routers.
7.4.2. RERR Reception
Upon receiving a Route Error, an AODVv2 router performs the following
steps:
1. Verify that the message contains the required data: at least one
unreachable address
* If not, ignore this RERR for further processing.
2. For each address in the AddressList, check that:
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* The address is valid (routable and unicast)
* The MetricType is supported and configured for use
* There is a LocalRoute with the same MetricType matching the
address using longest prefix matching
* Either the LocalRoute's next hop is the sender of the RERR and
the next hop interface is the interface on which the RERR was
received, or PktSource is present in the RERR and is a Router
Client address
* The unreachable address' sequence number is either unknown, or
is greater than the LocalRoute's sequence number
If any of the above are false the address does not match a
LocalRoute and MUST NOT be processed or regenerated in a RERR.
If all of the above are true, the LocalRoute which matches the
address is no longer valid. If the LocalRoute was previously
Active, it MUST be reported in a regenerated RERR. If the
LocalRoute was previously Idle, it MAY be reported in a
regenerated RERR, if ENABLE_IDLE_IN_RERR is configured. The
Local Route Set MUST be updated according to these rules:
* If the LocalRoute's prefix length is the same as the
unreachable address' prefix length, set LocalRoute.State to
Invalid.
* If the LocalRoute's prefix length is longer than the
unreachable address' prefix length, the LocalRoute MUST be
expunged from the Local Route Set, since it is a sub-route of
the route which is reported to be Invalid.
* If the prefix length is different, create a new LocalRoute
with the unreachable address, and its prefix length and
sequence number, and set LocalRoute.State to Invalid. These
Invalid routes are retained to avoid processing stale
messages.
* Update the sequence number on the existing LocalRoute, if the
reported sequence number is determined to be newer using the
comparison technique described in Section 4.4.
3. If there are previously Active LocalRoutes that MUST be reported,
as identified in step 2.:
* Regenerate the RERR as detailed in Section 7.4.3.
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7.4.3. RERR Regeneration
The Route Error message SHOULD NOT be regenerated if
CONTROL_TRAFFIC_LIMIT has been reached.
The procedure for RERR regeneration is as follows:
1. If PktSource was included in the original RERR, and PktSource is
not a Router Client, copy it into the regenerated RERR
2. For each LocalRoute that needs to be reported as identified in
Section 7.4.1:
* Insert LocalRoute.Address into the AddressList.
* Insert LocalRoute.PrefixLength into PrefixLengthList, if known
and not equal to the address length.
* Insert LocalRoute.SeqNum into SeqNumList, if known.
* Insert LocalRoute.MetricType into MetricTypeList.
The AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8). If the RERR contains PktSource, the
regenerated RERR SHOULD be sent unicast to the next hop on the
LocalRoute to PktSource. It MUST be sent over the same interface on
which the undeliverable IP packet was received. If there is no route
to PktSource, or PktSource is a Router Client, it SHOULD be multicast
to LL-MANET-Routers. If the RERR is sent in response to a broken
link, the RERR is, by default, multicast to LL-MANET-Routers.
8. RFC 5444 Representation
AODVv2 specifies that all control messages between routers MUST use
the Generalized Mobile Ad Hoc Network Packet/Message Format
[RFC5444], and therefore AODVv2's route messages comprise data which
is mapped to message elements in [RFC5444].
[RFC5444] provides a multiplexed transport for multiple protocols.
An [RFC5444] implementation MAY choose to optimize the content of
certain elements during message creation to reduce control message
overhead.
A brief summary of the [RFC5444] format:
1. A packet contains zero or more messages
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2. A message contains a Message Header, one Message TLV Block, zero
or more Address Blocks, and one Address Block TLV Block per
Address Block
3. The Message TLV Block MAY contain zero or more Message TLVs
4. An Address Block TLV Block MAY include zero or more Address Block
TLVs
5. Each TLV value in an Address Block TLV Block can be associated
with all of the addresses, or with a contiguous set of addresses,
or with a single address in the Address Block
AODVv2 does not require access to the [RFC5444] packet header.
In the message header, AODVv2 uses <msg-type> and <msg-addr-length>.
The <msg-addr-length> field indicates the length of any addresses in
the message, using <msg-addr-length> := (address length in octets -
1), i.e. 3 for IPv4 and 15 for IPv6.
The addresses in an Address Block MAY appear in any order, and values
in a TLV in the Address Block TLV Block must be associated with the
correct address in the Address Block by the [RFC5444] implementation.
To indicate which value is associated with each address, the AODVv2
message representation uses lists where the order of the addresses in
the AODVv2 AddressList matches the order of values in other data
lists, e.g., the order of SeqNums in the SeqNumList in an RERR.
[RFC5444] maps this information to Address Block TLVs associated with
the relevant addresses in the Address Block.
Each address included in the Address Block is identified as OrigAddr,
TargAddr, PktSource, or Unreachable Address by including an
ADDRESS_TYPE TLV in the Address Block TLV Block.
The following sections show how AODVv2 data is represented in
[RFC5444] messages. AODVv2 makes use of the VALIDITY_TIME Address
Block TLV from [RFC5497], and defines (in Section 11) a number of new
TLVs. To calculate the time-value for the VALIDITY_TIME Address
Block TLV, the value of C is defined in Section 10.2.
Where the extension type of a TLV is set to zero, this is the default
[RFC5444] value and the extension type will not be included in the
message.
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8.1. Route Request Message Representation
8.1.1. Message Header
+-------+---------------+--------+
| Data | Header Field | Value |
+-------+---------------+--------+
| None | <msg-type> | RREQ |
+-------+---------------+--------+
8.1.2. Message TLV Block
AODVv2 does not define any Message TLVs for an RREQ message.
8.1.3. Address Block
An RREQ contains two addresses, OrigAddr and TargAddr, and each
address has an associated prefix length. If the prefix length has
not been included in the AODVv2 message, it is equal to the address
length in bits.
+-------------------------+------------------------------+
| Data | Address Block |
+-------------------------+------------------------------+
| OrigAddr/OrigPrefixLen | <address> + <prefix-length> |
| TargAddr/TargPrefixLen | <address> + <prefix-length> |
+-------------------------+------------------------------+
8.1.4. Address Block TLV Block
Address Block TLVs are always associated with one or more addresses
in the Address Block. The following sections show the TLVs that
apply to each address.
8.1.4.1. Address Block TLVs for OrigAddr
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+--------------+---------------+------------+-----------------------+
| Data | TLV Type | Extension | Value |
| | | Type | |
+--------------+---------------+------------+-----------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_ORIGADDR |
| OrigSeqNum | SEQ_NUM | 0 | Sequence number of |
| | | | RREQ_Gen, the router |
| | | | which initiated route |
| | | | discovery. |
| OrigMetric | PATH_METRIC | MetricType | Metric value for the |
| /MetricType | | | route to OrigAddr, |
| | | | using MetricType. |
| ValidityTime | VALIDITY_TIME | 0 | ValidityTime for |
| | | | route to OrigAddr, |
| | | | represented as |
| | | | detailed in |
| | | | [RFC5497]. |
+--------------+---------------+------------+-----------------------+
8.1.4.2. Address Block TLVs for TargAddr
+------------+--------------+-------------+-------------------------+
| Data | TLV Type | Extension | Value |
| | | Type | |
+------------+--------------+-------------+-------------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_TARGADDR |
| TargSeqNum | SEQ_NUM | 0 | The last known |
| | | | TargSeqNum for |
| | | | TargAddr. |
+------------+--------------+-------------+-------------------------+
8.2. Route Reply Message Representation
8.2.1. Message Header
+-------+---------------+--------+
| Data | Header Field | Value |
+-------+---------------+--------+
| None | <msg-type> | RREP |
+-------+---------------+--------+
8.2.2. Message TLV Block
AODVv2 does not define any Message TLVs for an RREP message.
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8.2.3. Address Block
An RREP contains a minimum of two addresses, OrigAddr and TargAddr,
and each address has an associated prefix length. If the prefix
length has not been included in the AODVv2 message, it is equal to
the address length in bits.
It MAY also contain the address of the intended next hop, in order to
request acknowledgement to confirm bidirectionality of the link, as
described in Section 6.2. The prefix length associated with this
address is equal to the address length in bits.
+-------------------------+------------------------------+
| Data | Address Block |
+-------------------------+------------------------------+
| OrigAddr/OrigPrefixLen | <address> + <prefix-length> |
| TargAddr/TargPrefixLen | <address> + <prefix-length> |
| AckReq | <address> + <prefix-length> |
+-------------------------+------------------------------+
8.2.4. Address Block TLV Block
Address Block TLVs are always associated with one or more addresses
in the Address Block. The following sections show the TLVs that
apply to each address.
8.2.4.1. Address Block TLVs for OrigAddr
+-------+---------------+-----------------+--------------------+
| Data | TLV Type | Extension Type | Value |
+-------+---------------+-----------------+--------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_ORIGADDR |
+-------+---------------+-----------------+--------------------+
8.2.4.2. Address Block TLVs for TargAddr
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+--------------+---------------+------------+-----------------------+
| Data | TLV Type | Extension | Value |
| | | Type | |
+--------------+---------------+------------+-----------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_TARGADDR |
| TargSeqNum | SEQ_NUM | 0 | Sequence number of |
| | | | RREP_Gen, the router |
| | | | which created the |
| | | | RREP. |
| TargMetric | PATH_METRIC | MetricType | Metric value for the |
| /MetricType | | | route to TargAddr, |
| | | | using MetricType. |
| ValidityTime | VALIDITY_TIME | 0 | ValidityTime for |
| | | | route to TargAddr, |
| | | | represented as |
| | | | detailed in |
| | | | [RFC5497]. |
+--------------+---------------+------------+-----------------------+
8.2.4.3. Address Block TLVs for AckReq Intended Recipient Address
+-------+---------------+-----------------+------------------+
| Data | TLV Type | Extension Type | Value |
+-------+---------------+-----------------+------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_INTEND |
+-------+---------------+-----------------+------------------+
8.3. Route Reply Acknowledgement Message Representation
8.3.1. Message Header
+-------+---------------+-----------+
| Data | Header Field | Value |
+-------+---------------+-----------+
| None | <msg-type> | RREP_Ack |
+-------+---------------+-----------+
8.3.2. Message TLV Block
AODVv2 does not define any Message TLVs for an RREP_ack message.
8.3.3. Address Block
AODVv2 does not define an Address Block for an RREP_Ack message.
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8.3.4. Address Block TLV Block
AODVv2 does not define any Address Block TLVs for an RREP_Ack
message.
8.4. Route Error Message Representation
Route Error Messages MAY be split into multiple [RFC5444] messages
when the desired contents would exceed the MTU. However, all of the
resulting messages MUST have the same message header as described
below. If PktSource is included in the AODVv2 message, it MUST be
included in all of the resulting [RFC5444] messages.
8.4.1. Message Header
+-------+---------------+--------+
| Data | Header Field | Value |
+-------+---------------+--------+
| None | <msg-type> | RERR |
+-------+---------------+--------+
8.4.2. Message TLV Block
AODVv2 does not define any Message TLVs for an RERR message.
8.4.3. Address Block
The Address Block in an RERR MAY contain PktSource, the source
address of the IP packet triggering RERR generation, as detailed in
Section 7.4. The prefix length associated with PktSource is equal to
the address length in bits.
Address Block always contains one address per route that is no longer
valid, and each address has an associated prefix length. If a prefix
length has not been included for this address, it is equal to the
address length in bits.
+------------------------------+------------------------------------+
| Data | Address Block |
+------------------------------+------------------------------------+
| PktSource | <address> + <prefix-length> for |
| | PktSource |
| AddressList/PrefixLengthList | <address> + <prefix-length> for |
| | each unreachable address in |
| | AddressList |
+------------------------------+------------------------------------+
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8.4.4. Address Block TLV Block
Address Block TLVs are always associated with one or more addresses
in the Address Block. The following sections show the TLVs that
apply to each type of address in the RERR.
8.4.4.1. Address Block TLVs for PktSource
+------------+---------------+----------------+---------------------+
| Data | TLV Type | Extension Type | Value |
+------------+---------------+----------------+---------------------+
| PktSource | ADDRESS_TYPE | 0 | ADDRTYPE_PKTSOURCE |
+------------+---------------+----------------+---------------------+
8.4.4.2. Address Block TLVs for Unreachable Addresses
+----------------+--------------+------------+----------------------+
| Data | TLV Type | Extension | Value |
| | | Type | |
+----------------+--------------+------------+----------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_UNREACHABLE |
| SeqNumList | SEQ_NUM | 0 | Sequence number |
| | | | associated with |
| | | | invalid route to the |
| | | | unreachable address. |
| MetricTypeList | PATH_METRIC | MetricType | None. Extension Type |
| | | | set to MetricType of |
| | | | the route to the |
| | | | unreachable address. |
+----------------+--------------+------------+----------------------+
9. Simple External Network Attachment
Figure 4 shows a stub (i.e., non-transit) network of AODVv2 routers
which is attached to an external network via a single External
Network Access Router (ENAR). The interface to the external network
MUST NOT be configured in the InterfaceSet.
As in any externally-attached network, AODVv2 routers and Router
Clients that wish to be reachable from the external network MUST have
IP addresses within the ENAR's routable and topologically correct
prefix (e.g., 191.0.2.0/24 in Figure 4). This AODVv2 network and
networks attached to routers within it will be advertised to the
external network using procedures which are out of scope for this
specification.
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/-------------------------\
/ +----------------+ \
/ | AODVv2 Router | \
| | 191.0.2.2/32 | |
| +----------------+ | Routable
| +-----+--------+ Prefix
| | ENAR | /191.0.2.0/24
| | AODVv2 Router| /
| | 191.0.2.1 |/ /---------------\
| | serving net +------+ External \
| | 191.0.2.0/24 | \ Network /
| +-----+--------+ \---------------/
| +----------------+ |
| | AODVv2 Router | |
| | 191.0.2.3/32 | |
\ +----------------+ /
\ /
\-------------------------/
Figure 4: Simple External Network Attachment Example
When an AODVv2 router within the AODVv2 MANET wants to discover a
route toward an address on the external network, it uses the normal
AODVv2 route discovery for that IP Destination Address. The ENAR
MUST respond to RREQ on behalf of all external network destinations,
e.g., destinations not on the configured 191.0.2.0/24 network. RREQs
for addresses inside the AODVv2 network, e.g. destinations on the
configured 191.0.2.0/24 network, are handled using the standard
processes described in Section 7. Note that AODvv2 does not support
RREQs for prefixes that do not equal address length.
When an IP packet from an address on the external network destined
for an address in the AODVv2 MANET reaches the ENAR, if the ENAR does
not have a route toward that destination in its Routing Information
Base, it will perform normal AODVv2 route discovery for that
destination.
Configuring the ENAR as a default router is outside the scope of this
specification.
10. Configuration
AODVv2 uses various parameters which can be grouped into the
following categories:
o Timers
o Protocol constants
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o Administrative parameters and controls
This section show the parameters along with their definitions and
default values (if any).
Note that several fields have limited size (bits or bytes). These
sizes and their encoding may place specific limitations on the values
that can be set.
10.1. Timers
AODVv2 requires certain timing information to be associated with
Local Route Set entries and message replies. The default values are
as follows:
+------------------------+----------------+
| Name | Default Value |
+------------------------+----------------+
| ACTIVE_INTERVAL | 5 second |
| MAX_IDLETIME | 200 seconds |
| MAX_BLACKLIST_TIME | 200 seconds |
| MAX_SEQNUM_LIFETIME | 300 seconds |
| RERR_TIMEOUT | 3 seconds |
| RteMsg_ENTRY_TIME | 12 seconds |
| RREQ_WAIT_TIME | 2 seconds |
| RREP_Ack_SENT_TIMEOUT | 1 second |
| RREQ_HOLDDOWN_TIME | 10 seconds |
+------------------------+----------------+
Table 2: 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. Ideally,
for networks with frequent topology changes the AODVv2 parameters
SHOULD be adjusted using experimentally determined values or dynamic
adaptation. For example, in networks with infrequent topology
changes MAX_IDLETIME MAY be set to a much larger value. If the
values were configured differently, the following consequences may be
observed:
o If MAX_SEQNUM_LIFETIME was configured differently across the
network, and any of the routers lost their sequence number or
rebooted, this could result in their next route messages being
classified as stale at any AODVv2 router using a greater value for
MAX_SEQNUM_LIFETIME. This would delay route discovery from and to
the re-initializing router.
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o Routers with lower values for ACTIVE_INTERVAL + MAX_IDLETIME will
invalidate routes more quickly and free resources used to maintain
them. This can affect bursty traffic flows which have quiet
periods longer than ACTIVE_INTERVAL + MAX_IDLETIME. A route which
has timed out due to perceived inactivity is not reported. When
the bursty traffic resumes, it would cause a RERR to be generated,
and the traffic itself would be dropped. This route would be
removed from all upstream routers, even if those upstream routers
had larger ACTIVE_INTERVAL or MAX_IDLETIME values. A new route
discovery would be required to re-establish the route, causing
extra routing protocol traffic and disturbance to the bursty
traffic.
o Routers with lower values for MAX_BLACKLIST_TIME would allow
neighboring routers to participate in route discovery sooner than
routers with higher values. This could result in failed route
discoveries if un-blacklisted links are still uni-directional.
Since RREQs are retried, this would not affect success of route
discovery unless this value was so small as to un-blacklist the
router before the RREQ is retried. This value need not be
consistent across the network since it is used for maintaining a
1-hop blacklist. However it MUST be greater than RREQ_WAIT_TIME.
o Routers with lower values for RERR_TIMEOUT may create more RERR
messages than routers with higher values. This value should be
large enough that a RERR will reach all routers using the route
reported within it before the timer expires, so that no further
data traffic will arrive, and no duplicated RERR messages will be
generated.
o Routers with lower values for RteMsg_ENTRY_TIME may not consider
received redundant multicast route messages as redundant, and may
regenerate these messages unnecessarily.
o Routers with lower values for RREQ_WAIT_TIME may send more
frequent RREQ messages and wrongly determine that a route does not
exist, if the delay in receiving an RREP is greater than this
interval.
o Routers with lower values for RREP_Ack_SENT_TIMEOUT may wrongly
determine links to neighbors to be unidirectional if an RREP_Ack
is delayed longer than this timeout.
o Routers with lower values for RREQ_HOLDDOWN_TIME will retry failed
route discoveries sooner than routers with higher values. This
may be an advantage if the network topology is frequently
changing, or may unnecessarily cause more routing protocol
traffic.
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MAX_SEQNUM_LIFETIME MUST be configured to have the same values for
all AODVv2 routers in the network.
10.2. 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 section describing their use.
+------------------------+---------+--------------------------------+
| Name | Default | Description |
+------------------------+---------+--------------------------------+
| DISCOVERY_ATTEMPTS_MAX | 3 | Section 6.6 |
| RREP_RETRIES | 2 | Section 7.2.1 |
| MAX_METRIC[MetricType] | [TBD] | Section 5 |
| MAX_METRIC[HopCount] | 255 | Section 5 and Section 7 |
| INFINITY_TIME | [TBD] | Maximum expressible clock time |
| | | (Section 6.7.2) |
| C | 1/1024 | Constant used in validity time |
| | | calculation [RFC5497] |
+------------------------+---------+--------------------------------+
Table 3: AODVv2 Constants
MAX_METRIC[MetricType] MUST always be the maximum expressible metric
value of type MetricType. Field lengths associated with metric
values are found in Section 10.5.
These protocol constants MUST have the same values for all AODVv2
routers in the ad hoc network. If the values were configured
differently, the following consequences may be observed:
o DISCOVERY_ATTEMPTS_MAX: Routers with higher values are likely to
be more successful at finding routes, at the cost of additional
control traffic.
o RREP_RETRIES: Routers with lower values are more likely to
blacklist neighbors when there is a temporary fluctuation in link
quality.
o MAX_METRIC[MetricType]: No interoperability problems due to
variations on different routers, but routers with lower values may
exhibit overly restrictive behavior during route comparisons.
o INFINITY_TIME: No interoperability problems due to variations on
different routers, but if a lower value is used, route state
management may exhibit overly restrictive behavior.
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o C: Routers with lower values will invalidate timed routes before
routers with higher values, which will cause Route Error messages
to be generated and the route will effectively take on the shorter
validity time.
10.3. Local Settings
The following table lists AODVv2 parameters which SHOULD be
administratively configured for each router:
+------------------------+------------------------+--------------+
| Name | Default Value | Description |
+------------------------+------------------------+--------------+
| InterfaceSet | | Section 4.1 |
| BUFFER_SIZE_PACKETS | 2 | Section 6.6 |
| BUFFER_SIZE_BYTES | MAX_PACKET_SIZE [TBD] | Section 6.6 |
| CONTROL_TRAFFIC_LIMIT | [TBD - 50 pkts/sec?] | Section 7 |
+------------------------+------------------------+--------------+
Table 4: Configuration for Local Settings
10.4. Network-Wide Settings
The following administrative controls MAY be used to change the
operation of the network. The same settings SHOULD be used across
the network. Inconsistent settings at different routers in the
network will not result in protocol errors, but poor performance may
result.
+----------------------+-----------+----------------+
| Name | Default | Description |
+----------------------+-----------+----------------+
| ENABLE_IDLE_IN_RERR | Disabled | Section 7.4.1 |
+----------------------+-----------+----------------+
Table 5: Configuration for Network-Wide Settings
10.5. MetricType Allocation
The metric types used by AODVv2 are identified according to a new
table to be created and maintained by IANA. All implementations MUST
use these values.
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+---------------------+----------+--------------------+
| Name of MetricType | Type | Metric Value Size |
+---------------------+----------+--------------------+
| Unassigned | 0 | Undefined |
| Hop Count | 1 | 1 octet |
| Unallocated | 2 - 254 | TBD |
| Reserved | 255 | Undefined |
+---------------------+----------+--------------------+
Table 6: AODVv2 Metric Types
11. IANA Considerations
This section specifies several [RFC5444] message types and address
tlv-types required for AODVv2.
11.1. RFC 5444 Message Types
This specification defines four Message Types, to be allocated from
the 0-223 range of the "Message Types" namespace defined in
[RFC5444], as specified in Table 7.
+-----------------------------------------+-----------+
| Name of 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 7: AODVv2 Message Types
11.2. RFC 5444 Address Block TLV Types
This specification defines three Address Block TLV Types, to be
allocated from the "Address Block TLV Types" namespace defined in
[RFC5444], as specified in Table 8.
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+------------------------+----------+---------------+---------------+
| Name of TLV | Type | Length | Reference |
| | | (octets) | |
+------------------------+----------+---------------+---------------+
| PATH_METRIC | 11 (TBD) | depends on | Section 7 |
| | | MetricType | |
| SEQ_NUM | 12 (TBD) | 2 | Section 7 |
| ADDRESS_TYPE | 13 (TBD) | 1 | Section 8 |
+------------------------+----------+---------------+---------------+
Table 8: AODVv2 Address Block TLV Types
11.3. ADDRESS_TYPE TLV Values
These values are used in the [RFC5444] Address Type TLV discussed in
Section 8. All implementations MUST use these values.
+---------------+--------+
| Address Type | Value |
+---------------+--------+
| ORIGADDR | 0 |
| TARGADDR | 1 |
| UNREACHABLE | 2 |
| PKTSOURCE | 3 |
| INTEND | 4 |
| UNSPECIFIED | 255 |
+---------------+--------+
Table 9: AODVv2 Address Types
12. Security Considerations
This section describes various security considerations and potential
avenues to secure AODVv2 routing. The main objective of the AODVv2
protocol is for each router to communicate reachability information
about addresses for which it is responsible, and for routes it has
learned from other AODVv2 routers.
Networks using AODVv2 to maintain connectivity and establish routes
on demand may be vulnerable to certain well-known types of threats,
which will be detailed in the following. Some of the threats
described can be mitigated or eliminated. Tools to do so will be
described also.
Since route messages are regenerated at each router, AODVv2 assumes a
security model of transitive trust. The sender of a message MUST be
trusted in order for receiving one-hop neighbours to store the
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routing information it provides and regenerate the message to their
own one-hop neighbours.
Routes are installed based on information received from trusted
neighbours. Therefore a chain of trust back to the originator of a
message is assumed by any router using the routing information
received.
Since messages are regenerated rather than forwarded, the message
concepts known as RREQ, RREP and RERR do not travel as a single
unchanged entity between source and destination, and therefore
message integrity cannot be assured end-to-end between OrigAddr and
TargAddr.
The on-demand nature of AODVv2 route discovery automatically reduces
the vulnerability to route disruption. Since control traffic for
updating route tables is diminished, there is less opportunity for
attack and failure.
12.1. Availability
Threats to AODVv2 which reduce availability are considered below.
12.1.1. Denial of Service
Flooding attacks using RREQ amount to a (BLIND) denial of service for
route discovery: By issuing RREQ messages for targets that don't
exist, an attacker can flood the network, blocking resources and
drowning out legitimate traffic. The effect of this attack is
dampened by the fact that duplicate RREQ messages are dropped
(preventing the network from DDoSing itself). Processing
requirements for AODVv2 messages are typically quite small, however
AODVv2 routers receiving RREQs do allocate resources in the form of
Neighbor Set, Local Route Set and Multicast Route Message Set
entries. The attacker can maximize their impact on set growth by
changing OrigAddr for each RREQ. If a specific node is to be
targeted, this attack may be carried out in a DISTRIBUTED fashion,
either by compromising its direct neighbors or by specifying the
target's address as TargAddr. Note that it might be more economical
for the attacker to simply jam the medium; an attack which AODVv2
cannot defend itself against.
Mitigation:
o If AODVv2 routers always verify that the sender of the RERR
message is trusted, this threat is reduced. Processing
requirements would typically be dominated by calculations to
verify integrity. This has the effect of reducing (but by no
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means eliminating) AODVv2's vulnerability to denial of service
attacks.
o Authentication of senders can prevent foreign nodes from DoSing an
AODVv2 router. However, this does not protect the network if an
attacker has access to an already authorized router.
12.1.2. Malicious RERR messages
RERR messages are designed to cause removal of installed routes. A
malicious node could send an RERR message with false information to
attempt to get other routers to remove a route to one or more
specific destinations, therefore disrupting traffic to the advertised
destinations.
Routes will be deleted if an RERR is received, withdrawing a route
for which the sender is the receiver's next hop, and when the RERR
includes the MetricType of the installed route, and includes either
no sequence number for the route, or includes a greater sequence
number than the sequence number stored with that route in the
receiver's Local Route Set. Routes will also be deleted if a received
RERR contains a PktSource address corresponding to a Router Client.
The information necessary to construct a malicious RERR could be
learned by eavesdropping, either by listening to AODVv2 messages or
by watching data packet flows.
Since the RERR is multicast, it can be received by many routers in
the ad hoc network, and will be regenerated when processing results
in an active route being removed. This threat could have serious
impact on applications communicating by way of the sender of the RERR
message.
o The set of routers which use the malicious router as a next hop
may be targeted with a malicious RERR with no PktSource address
included, if the RERR contains routes for which the malicious
router is a next hop from the receiving router. However, since
the sender of the RERR message is either malicious or broken, it
is better that it is not used as a next hop for these routes
anyway.
o A single router which does not use the malicious router as part of
its route may be targeted with a malicious RERR with a PktSource
address included.
o Replayed RERR messages could be used to disrupt active routes.
Mitigation:
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o Protection against eavesdropping of AODVv2 messages would mitigate
this attack to some extent, but eavesdropping of data packets can
also be used to deduce the information about which routes could be
targeted.
o Protection against a malicious router becoming part of a route
will mitigate the attack where a set of routers are targeted.
This will not protect against the attack if a PktSource address is
included.
o By only regenerating RERR messages where active routes are
removed, the spread of the malicious RERR is limited.
o Including sequence numbers in RERR messages offers protection
against attacks using replays of these RERR messages.
o If AODVv2 routers always verify that the sender of the RERR
message is trusted, this threat is reduced.
12.1.3. False Confirmation of Link Bidirectionality
Links could be erroneously treated as bidirectional if malicious
unsolicited or spoofed RREP messages were to be accepted. This would
result in a route being installed which could not in fact be used to
forward data to the destination, and may divert data packets away
from the intended destination.
There is a window of RREQ_WAIT_TIME after an RREQ is sent, in which
any malicious router could send an RREP in response, in order for the
link to the malicious router to be deemed as bidirectional.
Mitigation:
o Ignoring unsolicited RREP and RREP_Ack messages partially
mitigates against this threat.
o If AODVv2 routers always verify that the sender of the RERR
message is trusted, this threat is reduced.
12.1.4. Message Deletion
A malicious router could decide not to regenerate a RREQ or RREP or
RERR message. Not regenerating a RERR or RREP message would disrupt
route discovery. Not regenerating a RERR message would result in the
source of data packets continuing to maintain and use the route, and
further RERR messages being generated by the sender of the non-
regenerated RERR. A malicious router could intentionally disrupt
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traffic flows by not allowing the source of data traffic to re-
discover a new route when one breaks.
Failing to send a RREP_Ack would also disrupt route establishment, by
not allowing the reverse route to be validated. Return traffic which
needs that route will prompt a new route discovery, wasting resources
and incurring a slight delay but not disrupting the ability for
applications to communicate.
Mitigation:
o None. also note that malicious router would have to wait for a
route to break before it could perform this attack.
12.2. Confidentiality
Passive inspection (eavesdropping) of AODVv2 control messages could
enable unauthorized devices to gain information about the network
topology, since exchanging such information is the main purpose of
AODVv2.
Eavesdropping of data traffic could allow a malicious device to
obtain information about how data traffic is being routed. With
knowledge of source and destination addresses, malicious messages
could be constructed to disrupt normal operation.
12.3. Integrity
Integrity of route information can be compromised in the following
types of attack:
12.3.1. Message Insertion
Valid route set entries can be replaced or modified by maliciously
constructed AODVv2 messages, destroying existing routes and the
network's integrity. Any router may pose as another router by
sending RREQ, RREP, RREP_Ack and RERR messages in its name.
o Sending an RREQ message with false information can disrupt traffic
to OrigAddr, if the sequence number attached is not stale compared
to any existing information about OrigAddr. Since RREQ is
multicast and likely to be received by all routers in the ad hoc
network, this threat could have serious impact on applications
communicating with OrigAddr. The actual threat to disrupt routes
to OrigAddr is reduced by the AODVv2 mechanism of marking RREQ-
derived routes as "Unconfirmed" until the link to the next hop is
confirmed.
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o Sending an RREP message with false information can disrupt traffic
to TargAddr. Since RREP is unicast, and ignored if a
corresponding RREQ was not recently sent, this threat is
minimized, and is restricted to receivers along the path from
OrigAddr to TargAddr.
o Sending an RREP_Ack message with false information can cause the
route advertised to a target address in an RREP to be erroneously
accepted even though the route would contain a unidirectional link
and thus not be suitable for most traffic. Since RREP_Ack is
unicast, and ignored if a RREP was not sent recently to the sender
of the RREP_Ack, this threat is minimized and is strictly local to
the RREP transmitter expecting the acknowledgement. Unsolicited
RREP_Acks are ignored.
o Sending an RERR message with false information is discussed in
Section 12.1.2.
Mitigation: * If AODVv2 routers always verify that the sender of a
message is trusted, this threat is reduced.
12.3.2. Message Modification - Man in the Middle
Any AODVv2 router can regenerate messages with modified data.
Mitigation:
o If AODVv2 routers verify the integrity of AODVv2 messages, then
the threat of disruption is minimized. A man in the middle with
no knowledge of the shared secret key used to calculate an
integrity check value MAY modify a message but the message will be
rejected when it fails an integrity check.
12.3.3. Replay Attacks
Replaying of RREQ or RREP messages would be of less use to an
attacker, since they would be dropped immediately due to their stale
sequence number. RERR messages MAY or MAY NOT include sequence
numbers and are therefore susceptible to replay attacks. RREP_Ack
messages do not include sequence numbers and are therefore
susceptible to replay attacks.
Mitigation:
o Use of timestamps or sequence numbers prevents replay attacks.
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12.4. Protection Mechanisms
12.4.1. Confidentiality and Authentication
Encryption MAY be used for AODVv2 messages. If the routers share a
packet-level security association, the message data can be encrypted
prior to message transmission. The establishment of such security
associations is outside the scope of this specification. Encryption
will not only protect against unauthorized devices obtaining
information about network topology (eavesdropping) but will ensure
that only trusted routers participate in routing operations.
12.4.2. Integrity and Trust using ICVs
Cryptographic Integrity Check Values (ICVs) can be used to ensure
integrity of received messages, protecting against man in the middle
attacks. Further, by using ICVs, only those routers with knowledge
of a shared secret key are allowed to participate in routing
information exchanges. [RFC7182] defines ICV TLVs for use with
[RFC5444].
The data contained in AODVv2 routing protocol messages MUST be
verified using Integrity Check Values, to avoid the use of message
data if the message has been tampered with.
The method of distribution of shared secret keys is out of the scope
of this protocol. Key management is not specified for the following
reasons:
12.4.3. Replay Protection using Timestamps
Replay attacks MUST be prevented by using timestamps or sequence
numbers in messages. [RFC7182] defines a TIMESTAMP TLV for use with
[RFC5444].
The data contained in AODVv2 routing protocol messages MUST be
protected with a TIMESTAMP value to ensure the protection against
replaying of the message. Sequence numbers can be used as
timestamps, since they are known to be strictly increasing.
12.4.4. Application to AODVv2
Implementations of AODVv2 MUST support ICV TLVs using type-extensions
1 and 2, hash-function HASH_FUNCTION, and cryptographic function
CRYPTOGRAPHIC_FUNCTION. An ICV MUST be included with every message.
The ICV value MAY be truncated as specified in [RFC7182].
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Implementations of AODVv2 MUST support a TIMESTAMP TLV using type-
extension 0. The timestamp used is a sequence number, and therefore
the length of the <TIMESTAMP-value> field matches the AODVv2 sequence
number defined in Section 4.4. The TIMESTAMP TLV MUST be included in
RREP_Ack and RERR messages.
When more than one message is included in an RFC5444 packet, using a
single ICV Packet TLV or single TIMESTAMP Packet TLV is more
efficient than including ICV and TIMESTAMP Message TLVs in each
message created. In this case, the RFC5444 multiplexer MUST be
instructed to include the Packet TLVs in packets containing AODVv2
messages, or MUST be selected because it always performs these
additions. If the multiplexer is not capable of adding the Packet
TLVs, the TLVs MUST be included as Message TLVs in each AODVv2
message in the packet.
After message generation but before transmission, the ICV and
TIMESTAMP TLVs MUST be added according to each message type as
detailed in the following sections. The following steps list the
generic procedure to be performed:
1. The considerations in Section 8 of [RFC7182] are followed,
removing existing ICV TLVs and adjusting the size and flags
fields.
2. The ICV is calculated over the fields specified below, depending
on message type. This value MAY be truncated (as specified in
[RFC7182]).
3. If the TIMESTAMP is to be included, add the TIMESTAMP TLV,
updating size fields as necessary.
4. Add the ICV TLV, updating size fields as necessary.
5. The changes made in Step 1 are reversed to re-add any existing
ICV TLVs and adjusting the size and flags fields.
The ICV MUST be verified at the receiver. Verification of a received
ICV value is performed by repeating Step 1 and Step 2. If the ICV
value calculated from the received message or packet does not match
the value of <ICV-data> in the received message or packet, the
validation fails and the AODVv2 message MUST be discarded.
Verification of a received TIMESTAMP value is performed differently
depending on message type.
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12.4.4.1. RREQ Generation and Reception
Since OrigAddr is included in the RREQ, the ICV can be calculated and
verified using all of the message contents. This provides message
integrity and endpoint authentication, because trusted routers MUST
hold the shared key in order to calculate the ICV value. The ICV TLV
has type extension := 1.
Since RREQ_Gen's sequence number is incremented for each new RREQ,
replay protection is already afforded and no extra timestamp
mechanism is required.
12.4.4.2. RREP Generation and Reception
Since TargAddr is included in the RREP, the ICV can be calculated and
verified using all of the message contents. This provides message
integrity and endpoint authentication, because trusted routers MUST
hold the shared key in order to calculate the ICV value. The ICV TLV
has type extension := 1.
Since RREP_Gen's sequence number is incremented for each new RREP,
replay protection is afforded and no extra timestamp mechanism is
required.
12.4.4.3. RREP_Ack Generation and Reception
The RREP_Gen uses the source IP address of the RREP_Ack to identify
the sender to look up whether the RREP_Ack is expected and update the
Neighbor Set, and so the ICV MUST be calculated using the message
contents and the IP source address. The ICV TLV has type extension
:= 2 in order to accomplish this. This provides message integrity
and endpoint authentication, because trusted routers MUST hold the
shared key in order to calculate the ICV value.
The message MUST also include a timestamp to protect against replay
attacks, using TargSeqNum from the RREP as the value in the TIMESTAMP
TLV. Verification of a received TIMESTAMP value is performed by
comparing the sequence number in the <TIMESTAMP-value> field with the
sequence number in a recently sent RREP awaiting acknowledgement from
the sender of the RREP_Ack. If the sequence number is not equal, the
AODVv2 message MUST be discarded.
12.4.4.4. RERR Generation and Reception
The receiver of the RERR MUST use the source IP address of the RERR
to identify the sender to look up routes using that sender as next
hop, and so the ICV MUST be calculated using the message contents and
the IP source address. The ICV TLV has type extension := 2 in order
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to accomplish this. This provides message integrity and endpoint
authentication, because trusted routers MUST hold the shared key in
order to calculate the ICV value.
The message MUST also include a timestamp to protect against replay
attacks, incrementing and using RERR_Gen's sequence number as the
value in the TIMESTAMP TLV. Verification of a received TIMESTAMP
value is performed by comparing the sequence number in the
<TIMESTAMP-value> field with the last seen sequence number from the
sender of the RERR. If the sequence number is not greater, the
AODVv2 message MUST be discarded.
13. 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, Justin Dean, Christopher Dearlove, Fatemeh Ghassemi,
Ulrich Herberg, Henner Jakob, Ramtin Khosravi, Luke Klein-Berndt,
Lars Kristensen, Tronje Krop, Koojana Kuladinithi, Kedar Namjoshi,
Keyur Patel, Alexandru Petrescu, Henning Rogge, Fransisco Ros, Pedro
Ruiz, Christoph Sommer, Romain Thouvenin, Richard Trefler, Jiazi Yi,
Seung Yi, Behnaz Yousefi, and Cong Yuan, for their reviews of AODVv2
and DYMO, as well as numerous specification suggestions.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
Demand Distance Vector (AODV) Routing", RFC 3561,
DOI 10.17487/RFC3561, July 2003,
<http://www.rfc-editor.org/info/rfc3561>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
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[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<http://www.rfc-editor.org/info/rfc5082>.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized Mobile Ad Hoc Network (MANET) Packet/Message
Format", RFC 5444, DOI 10.17487/RFC5444, February 2009,
<http://www.rfc-editor.org/info/rfc5444>.
[RFC5497] Clausen, T. and C. Dearlove, "Representing Multi-Value
Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497,
DOI 10.17487/RFC5497, March 2009,
<http://www.rfc-editor.org/info/rfc5497>.
[RFC5498] Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network
(MANET) Protocols", RFC 5498, DOI 10.17487/RFC5498, March
2009, <http://www.rfc-editor.org/info/rfc5498>.
[RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
and D. Barthel, "Routing Metrics Used for Path Calculation
in Low-Power and Lossy Networks", RFC 6551,
DOI 10.17487/RFC6551, March 2012,
<http://www.rfc-editor.org/info/rfc6551>.
[RFC7182] Herberg, U., Clausen, T., and C. Dearlove, "Integrity
Check Value and Timestamp TLV Definitions for Mobile Ad
Hoc Networks (MANETs)", RFC 7182, DOI 10.17487/RFC7182,
April 2014, <http://www.rfc-editor.org/info/rfc7182>.
14.2. Informative References
[I-D.perkins-irrep]
Perkins, C., "Intermediate RREP for dynamic MANET On-
demand (AODVv2) Routing", draft-perkins-irrep-03 (work in
progress), May 2015.
[Koodli01]
Koodli, R. and C. Perkins, "Fast handovers and context
transfers in mobile networks", Proceedings of the ACM
SIGCOMM Computer Communication Review 2001, Volume 31
Issue 5, 37-47, October 2001.
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[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, S. and J. Macker, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501,
DOI 10.17487/RFC2501, January 1999,
<http://www.rfc-editor.org/info/rfc2501>.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<http://www.rfc-editor.org/info/rfc4193>.
[RFC4728] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
Routing Protocol (DSR) for Mobile Ad Hoc Networks for
IPv4", RFC 4728, DOI 10.17487/RFC4728, February 2007,
<http://www.rfc-editor.org/info/rfc4728>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<http://www.rfc-editor.org/info/rfc4861>.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
Considerations in Mobile Ad Hoc Networks (MANETs)",
RFC 5148, DOI 10.17487/RFC5148, February 2008,
<http://www.rfc-editor.org/info/rfc5148>.
[RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
RFC 6130, DOI 10.17487/RFC6130, April 2011,
<http://www.rfc-editor.org/info/rfc6130>.
[Sholander02]
Sholander, P., Coccoli, P., Oakes, T., and S. Swank, "A
Portable Software Implementation of a Hybrid MANET Routing
Protocol", 2002.
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Appendix A. AODVv2 Draft Updates
This section lists the changes between AODVv2 revisions ...-14.txt
and ...-15.txt.
o Shortened Terminology descriptions of Unreachable Address,
Unreachable Route, Valid Route and add references to sections
explaining the details.
o Clarified language regarding empty Message TLV Blocks and Address
Blocks.
o Removed reference to RFC6551 from MetricType Allocation.
o Removed Message Aggregation Delay extension.
o Detailed what happens if the specified timers aren't the same
across the network.
o RERRs SHOULD be MULTICAST instead of MUST (which enables precursor
lists).
o RREP_Ack Reception: clarified wording regarding blacklist check.
o Removed "approaching the limit" verbiage.
o Added instructions on which messages to drop on congestion.
o Revised set vs. table wording
o Added note that AODVv2 was intended for use in mobile ad hoc
wireless networks.
o Changed language to clarify that the RFC5444 multiplexer sends the
messages, not AODVv2.
o Added instructions on how to use the Multicast Route Message Set
to check whether an RREP_Ack or RREP was received in time.
o Removed optional features.
o Moved AODVv2 to the Experimental Track.
Authors' Addresses
Perkins, et al. Expires October 22, 2016 [Page 77]
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Charles E. Perkins
Futurewei Inc.
2330 Central Expressway
Santa Clara, CA 95050
USA
Phone: +1-408-330-4586
Email: charliep@computer.org
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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