Mobile Ad hoc Networks Working Group C. Perkins
Internet-Draft
Intended status: Standards Track I. Chakeres
Expires: September 13, 2012 CenGen
March 12, 2012
Dynamic MANET On-demand (AODVv2) Routing
draft-ietf-manet-dymo-22
Abstract
The Dynamic MANET On-demand (AODVv2) routing protocol is intended for
use by mobile routers in wireless, multihop networks. AODVv2
determines unicast routes among AODVv2 routers within the network in
an on-demand fashion, offering on-demand convergence in dynamic
topologies.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 13, 2012.
Copyright Notice
Copyright (c) 2012 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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
Perkins & Chakeres Expires September 13, 2012 [Page 1]
Internet-Draft AODVv2 March 2012
described in the Simplified BSD License.
Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Applicability Statement . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Route Table Entry . . . . . . . . . . . . . . . . . . . . 7
4.2. AODVv2 Messages . . . . . . . . . . . . . . . . . . . . . 8
4.2.1. Generalized Packet and Message Structure . . . . . . . 9
4.2.2. Routing Message (RteMsg) - RREQ and RREP . . . . . . . 10
4.2.3. Route Error (RERR) . . . . . . . . . . . . . . . . . . 11
5. Detailed Operation . . . . . . . . . . . . . . . . . . . . . . 12
5.1. AODVv2 Sequence Numbers . . . . . . . . . . . . . . . . . 12
5.1.1. Maintaining A Node's Own Sequence Number . . . . . . . 12
5.1.2. Numerical Operations on OwnSeqNum . . . . . . . . . . 13
5.1.3. OwnSeqNum Rollover . . . . . . . . . . . . . . . . . . 13
5.1.4. Actions After OwnSeqNum Loss . . . . . . . . . . . . . 13
5.2. AODVv2 Routing Table Operations . . . . . . . . . . . . . 13
5.2.1. Judging Routing Information's Usefulness . . . . . . . 13
5.2.2. Creating or Updating a Route Table Entry with
Received Preferable Routing Information . . . . . . . 15
5.2.3. Route Table Entry Timeouts . . . . . . . . . . . . . . 16
5.3. Routing Messages . . . . . . . . . . . . . . . . . . . . . 16
5.3.1. RREQ Creation . . . . . . . . . . . . . . . . . . . . 16
5.3.2. RREP Creation . . . . . . . . . . . . . . . . . . . . 17
5.3.3. RteMsg Handling . . . . . . . . . . . . . . . . . . . 18
5.4. Route Discovery . . . . . . . . . . . . . . . . . . . . . 21
5.5. Route Maintenance . . . . . . . . . . . . . . . . . . . . 22
5.5.1. Active Next-hop Router Adjacency Monitoring . . . . . 22
5.5.2. Updating Route Lifetimes During Packet Forwarding . . 23
5.5.3. RERR Generation . . . . . . . . . . . . . . . . . . . 23
5.5.4. RERR Handling . . . . . . . . . . . . . . . . . . . . 24
5.6. Unknown Message and TLV Types . . . . . . . . . . . . . . 25
5.7. Advertising Network Addresses . . . . . . . . . . . . . . 25
5.8. Simple Internet Attachment . . . . . . . . . . . . . . . . 25
5.9. Multiple Interfaces . . . . . . . . . . . . . . . . . . . 27
5.10. AODVv2 Control Packet/Message Generation Limits . . . . . 27
6. Administratively Configured Parameters and Timer Values . . . 27
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
7.1. AODVv2 Message Types Specification . . . . . . . . . . . . 30
7.2. Message and Address Block TLV Type Specification . . . . . 30
7.3. Address Block TLV Specification . . . . . . . . . . . . . 31
8. Security Considerations . . . . . . . . . . . . . . . . . . . 31
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 32
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Perkins & Chakeres Expires September 13, 2012 [Page 2]
Internet-Draft AODVv2 March 2012
10.1. Normative References . . . . . . . . . . . . . . . . . . . 33
10.2. Informative References . . . . . . . . . . . . . . . . . . 33
Appendix A. Changes since the Previous Version . . . . . . . . . 34
Appendix B. Proposed additional changes for LOADng conformance . 34
Appendix C. Shifting Responsibility for an Address Between
AODVv2 Routers . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 35
Perkins & Chakeres Expires September 13, 2012 [Page 3]
Internet-Draft AODVv2 March 2012
1. Overview
The Dynamic MANET On-demand (AODVv2) routing protocol enables on-
demand, multihop unicast routing among participating AODVv2 routers.
The basic operations of the AODVv2 protocol are route discovery and
route maintenance. Route discovery is performed when an AODVv2
router receives a packet from a node under its responsibility to a
destination for which it does not have a route. Route maintenance is
performed to help ensure that the route being used to forward packets
from the source to the destination remains operational.
During route discovery, the originator's AODVv2 router initiates
dissemination of a Route Request (RREQ) throughout the network to
find a route to a particular destination, via the AODVv2 router
responsible for this destination. During this hop-by-hop
dissemination process, each intermediate AODVv2 router records a
route to the originator. When the target's AODVv2 router receives
the RREQ, it responds with a Route Reply (RREP) sent hop-by-hop
toward the originating AODVv2 router. Each intermediate AODVv2
router that receives the RREP creates a route to the target, and then
the RREP is unicast hop-by-hop toward the originator. When the
originator's AODVv2 router receives the RREP, routes have then been
established between the originating AODVv2 router and the target
AODVv2 router in both directions.
Route maintenance consists of two operations. In order to preserve
routes in use, AODVv2 routers extend route lifetimes upon
successfully forwarding a packet. In order to react to changes in
the network topology, AODVv2 routers monitor traffic being forwarded.
When a data packet is received for forwarding and a route for the
destination is not known or the route is broken, then the AODVv2
router of the source of the packet is notified. A Route Error (RERR)
is sent toward the packet source to indicate the route to particular
destination addresses is invalid or missing. When the source's
AODVv2 router receives the RERR, it deletes the route. If this
source's AODVv2 router later receives a packet for forwarding to the
same destination, it will need to perform route discovery again for
that destination.
AODVv2 uses sequence numbers to ensure loop freedom [Perkins99].
Sequence numbers enable AODVv2 routers to determine the temporal
order of AODVv2 route discovery messages, thereby avoiding use of
stale routing information.
2. Applicability Statement
The AODVv2 routing protocol is designed for stub or disconnected
Perkins & Chakeres Expires September 13, 2012 [Page 4]
Internet-Draft AODVv2 March 2012
mobile ad hoc networks (MANETs). AODVv2 handles a wide variety of
mobility patterns by dynamically determining routes on-demand.
AODVv2 also handles a wide variety of traffic patterns. In networks
with a large number of routers, AODVv2 is best suited for sparse
traffic scenarios where routers forward packets to only a small
portion of the other AODVv2 routers, due to the on-demand nature of
route discovery and route maintenance.
AODVv2 is applicable to memory constrained devices, since little
routing state is maintained in each AODVv2 router. Only routing
information related to active sources and destinations is maintained,
in contrast to most proactive routing protocols that require routing
information to all routers within the routing region be maintained.
AODVv2 supports routers with multiple interfaces participating in the
MANET. AODVv2 routers can also perform routing on behalf of other
nodes, attached via participating or non-participating interfaces.
AODVv2 routers perform route discovery to find a route to a
particular destination. Therefore, AODVv2 routers MUST be configured
to initiate and respond to route discovery on behalf of certain
nodes, identified by address. When AODVv2 is the only protocol
interacting with the forwarding table, AODVv2 MAY be configured to
perform route discovery for all unknown unicast destinations.
At any time within an AODVv2 routing region, only one AODVv2 router
SHOULD be responsible for, i.e. "own", any particular address.
Coordination among multiple AODVv2 routers to distribute routing
information correctly for a shared address (i.e. an address that is
advertised and can be reached via multiple AODVv2 routers) is not
described in this document. The router behavior for shifting
responsibility for an address from one AODVv2 router to another is
mentioned in Appendix C.
AODVv2 only utilizes bidirectional links. In the case of possible
unidirectional links, either blacklists (see Section 7.2) or other
means (e.g. adjacency establishment with only neighboring routers
that have bidirectional communication as indicated by NHDP
[I-D.ietf-manet-nhdp]) of ensuring and monitoring bi-directionality
is recommended. Otherwise, persistent packet loss may occur.
The routing algorithm in AODVv2 may be operated at layers other than
the network layer, using layer-appropriate addresses.
3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
Perkins & Chakeres Expires September 13, 2012 [Page 5]
Internet-Draft AODVv2 March 2012
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Additionally, this document uses some terminology from [RFC5444].
This document defines the following terminology:
Adjacency
A relationship between selected bi-directional neighboring routers
for the purpose of exchanging routing information. Not every pair
of neighboring routers will necessarily form an adjacency.
Neighboring routers may form an adjacency based several different
pieces of information or protocols; for example, exchange of
AODVv2 routing messages, other protocols (e.g. NDP [RFC4861] or
NHDP [I-D.ietf-manet-nhdp]), or manual configuration. Similarly,
loss of a routing adjacency may also be based upon several pieces
of information, and monitoring of adjacencies where packets are
being forwarded is required (see Section 5.5.1).
Distance (Dist)
A metric of the distance a message or piece of information has
traversed. The minimum value of distance is the number of IP hops
traversed. The maximum value is 65,535.
AODVv2 Sequence Number (SeqNum)
An AODVv2 Sequence Number is maintained by each AODVv2 router
process. This sequence number is used by other AODVv2 routers to
identify the temporal order of routing information generated and
ensure loop-free routes.
Multihop-capable Unicast IP Address
A multihop-capable unicast IP address is a unicast IP address that
when put into the IP.SourceAddress or IP.DestinationAddress field
is scoped sufficiently to be forwarded by a router. Globally-
scoped unicast IP addresses and Unique Local Addresses (ULAs) are
examples of multihop-capable unicast IP addresses.
Originating Node (OrigNode)
The originating node is the source, its AODVv2 router creates a
AODVv2 control message on its behalf in an effort to disseminate
some routing information. The originating node is also referred
to as a particular message's originator.
Route Error (RERR)
A RERR message is used to indicate that an AODVv2 router does not
have a forwarding route to one or more particular addresses.
Perkins & Chakeres Expires September 13, 2012 [Page 6]
Internet-Draft AODVv2 March 2012
Route Reply (RREP)
A RREP message is used to disseminate routing information about
the RREP TargetNode to the RREP OrigNode and the AODVv2 routers
between them.
Route Request (RREQ)
A RREQ message is used to discover a valid route to a particular
destination address, called the RREQ TargetNode. When an AODVv2
router processes a RREQ, it learns routing information on how to
reach the RREQ OrigNode.
Target Node (TargetNode)
The TargetNode is the ultimate destination of a message.
This Node (ThisNode)
ThisNode corresponds to the AODVv2 router process currently
performing a calculation or attending to a message.
Type-Length-Value structure (TLV)
A generic way to represent information, please see [RFC5444] for
additional information.
Unreachable Node (UnreachableNode)
An UnreachableNode is a node for which a forwarding route is
unknown.
4. Data Structures
4.1. Route Table Entry
The route table entry is a conceptual data structure.
Implementations may use any internal representation that conforms to
the semantics of a route as specified in this document.
Conceptually, a route table entry has the following fields:
Route.Address
The (host or network) destination address of the node(s)
associated with the routing table entry.
Route.Prefix
Indicates that the associated address is a network address, rather
than a host address. The value is the length of the netmask/
prefix.
Perkins & Chakeres Expires September 13, 2012 [Page 7]
Internet-Draft AODVv2 March 2012
Route.SeqNum
The AODVv2 SeqNum associated with this routing information.
Route.NextHopAddress
The IP address of the adjacent AODVv2 router on the path toward
the Route.Address.
Route.NextHopInterface
The interface used to send packets toward the Route.Address.
Route.Forwarding
A flag indicating whether this Route can be used for forwarding
data packets. This flag MAY be provided for management and
monitoring.
Route.Broken
A flag indicating whether this Route is broken. This flag is set
to true if the next-hop becomes unreachable or in response to
attending to a RERR (see Section 5.5.4).
The following field is optional:
Route.Dist
A dimensionless metric indicating the distance traversed before
reaching the Route.Address node.
Not including optional information may cause performance degradation,
but it will not cause the protocol to operate incorrectly.
In addition to a route table data structure, each route table entry
may have several timers associated with the information. These
timers/timeouts are discussed in Section 5.2.3.
4.2. AODVv2 Messages
When describing AODVv2 protocol messages, it is necessary to refer to
fields in several distinct parts of the overall packet. These
locations include the IP header, the UDP header, and fields from
[RFC5444]. This document uses the following notation conventions.
Information found in the table.
Perkins & Chakeres Expires September 13, 2012 [Page 8]
Internet-Draft AODVv2 March 2012
+---------------------------+-------------------+
| Information Location | Notational Prefix |
+---------------------------+-------------------+
| IP header | IP. |
| UDP header | UDP. |
| RFC5444 message header | MsgHdr. |
| RFC5444 message TLV | MsgTLV. |
| RFC5444 address blocks | AddBlk. |
| RFC5444 address block TLV | AddTLV. |
+---------------------------+-------------------+
Table 1
4.2.1. Generalized Packet and Message Structure
AODVv2 messages conform to the generalized packet and message format
as described in [RFC5444]. Here is a brief description of the
format. A packet is made up of messages. A message is made up of a
message header, message TLV block, and zero or more address blocks.
Each of the address blocks may also have an associated address TLV
block.
For interoperability with other AODVv2 routers, all AODVv2 messages
specified in this document SHOULD sent using the IP protocol number
(138) reserved for manet protocols [RFC5498]; or the UDP destination
port (269) reserved for manet protocols [RFC5498] and IP protocol
number for UDP.
Most AODVv2 messages are sent with the IP destination address set to
the link-local multicast address LL-MANET-Routers [RFC5498] unless
otherwise stated. Therefore, all AODVv2 routers SHOULD subscribe to
LL-MANET-Routers [RFC5498] for receiving control packets. Note that
multicast packets MAY be sent via unicast. For example, this may
occur for certain link-types (non broadcast mediums), improved
robustness, or manually configured router adjacencies.
Unicast AODVv2 messages (e.g. RREP) unless otherwise specified in
this document are sent with the IP destination set to the
Route.NextHopAddress of the route to the TargetNode.
The IPv4 TTL (IPv6 Hop Limit) field for all packets containing AODVv2
messages is set to 255. If a packet is received with a value other
than 255, it is discarded. This mechanism helps to ensures that
packets have not passed through any intermediate routers, and it is
known as GTSM [RFC5082].
The length of an address (32 bits for IPv4 and 128 bits for IPv6)
inside an AODVv2 message depends on the msg-addr-length (MAL) in the
Perkins & Chakeres Expires September 13, 2012 [Page 9]
Internet-Draft AODVv2 March 2012
msg-header, as specified in [RFC5444].
AODVv2 control packets SHOULD be given priority queuing and channel
access.
4.2.2. Routing Message (RteMsg) - RREQ and RREP
Routing Messages (RteMsgs) are used to disseminate routing
information. There are two AODVv2 message types that are considered
to be routing messages (RteMsgs): RREQ and RREP. They contain very
similar information and function, but have slightly different
handling rules. The main difference between the two messages is that
RREQ messages generally solicit a RREP, whereas a RREP is the
response to RREQ.
RteMsg creation and handling are described in Section 5.3.
A RteMsg requires the following information:
IP.SourceAddress
The IP address of the node currently sending this packet. This
field is generally filled automatically by the operating system
and should not require special handling.
IP.DestinationAddress
The IP address of the packet destination. For multicast RREQ the
IP.DestinationAddress is set to LL-MANET-Routers [RFC5498]. For
unicast RREP the IP.DestinationAddress is set to the
NextHopAddress toward the RREP TargetNode.
IP.ProtocolNumber and UDP.DestinationPort
The IP Protocol Number 138 (manet) has been reserved for MANET
protocols [RFC5498]. In addition to using this IP protocol
number, AODVv2 may use the UDP port 269 (manet) [RFC5498] in
conjunction with the IP Protocol Number 17 (UDP).
MsgHdr.HopLimit
The remaining number of hops this message is allowed to traverse.
AddBlk.TargetNode.Address
The IP address of the message TargetNode. In a RREQ the
TargetNode is the destination address for which route discovery is
being performed. In a RREP the TargetNode is the RREQ OrigNode
address. The TargetNode address is the first address in a routing
message.
Perkins & Chakeres Expires September 13, 2012 [Page 10]
Internet-Draft AODVv2 March 2012
AddBlk.OrigNode.Address
The IP address of the originator and its associated prefix length.
In a RREQ the OrigNode is the source's address and prefix. In a
RREP the OrigNode is the RREQ TargetNode's address and prefix for
which a RREP is being generated. This address is the second
address in the message for RREQ.
OrigNode.AddTLV.SeqNum
The AODVv2 sequence number of the originator's AODVv2 router.
A RteMsg may optionally include the following information:
TargetNode.AddTLV.SeqNum
The last known AODVv2 sequence number of the TargetNode.
TargetNode.AddTLV.Dist
The last known Distance to the TargetNode.
AddBlk.AdditionalNode.Address
The IP address of an additional node that can be reached via the
AODVv2 router adding this information. Each
AdditionalNode.Address MUST include its prefix. Each
AdditionalNode.Address MUST also have an associated Node.SeqNum in
the address TLV block.
AdditionalNode.AddTLV.SeqNum
The AODVv2 sequence number associated with this routing
information.
OrigNode.AddTLV.Dist
A metric of the distance to reach the associated OrigNode.Address.
This field is incremented by at least one at each intermediate
AODVv2 router.
AdditionalNode.AddTLV.Dist
A metric of the distance to reach the associated
AdditionalNode.Address. This field is incremented by at least one
at each intermediate AODVv2 router.
4.2.3. Route Error (RERR)
A RERR message is used to disseminate the information that a route is
not available for one or more particular addresses.
RERR creation and handling are described in Section 5.5.
A RERR requires the following information:
Perkins & Chakeres Expires September 13, 2012 [Page 11]
Internet-Draft AODVv2 March 2012
IP.SourceAddress
The IP address of the AODVv2 router that sent this packet. This
field is generally filled automatically by the operating system
and should not require special handling.
IP.DestinationAddress
For multicast RERR messages, The IP address is set to LL-MANET-
Routers [RFC5498]. For unicast RERR messages, the IP address is
set to the NextHopAddress.
IP.ProtocolNumber and UDP.DestinationPort
The IP Protocol Number 138 (manet) has been reserved for MANET
protocols [RFC5498]. In addition to using this IP protocol
number, AODVv2 may use the UDP port 269 (manet) [RFC5498] in
conjunction with the IP Protocol Number 17 (UDP).
MsgHdr.HopLimit
The remaining number of hops this message is allowed to traverse.
AddBlk.UnreachableNode.Address
The address of an UnreachableNode and its associated prefix
length. Multiple unreachable addresses may be included in a RERR.
A Route Error may optionally include the following information:
UnreachableNode.AddTLV.SeqNum
The last known AODVv2 sequence number of the unreachable node. If
a SeqNum for an address is zero (0) or not included, it is assumed
to be unknown. This case occurs when a node receives a message to
forward to a destination for which it does not have any
information in its routing table.
5. Detailed Operation
5.1. AODVv2 Sequence Numbers
AODVv2 sequence numbers allow AODVv2 routers to judge the freshness
of routing information and ensure loop freedom.
5.1.1. Maintaining A Node's Own Sequence Number
AODVv2 requires that each AODVv2 router in the network maintain its
own AODVv2 sequence number (OwnSeqNum) on behalf of the addresses for
which it is responsible. OwnSeqNum a 16-bit unsigned integer. The
circumstances for ThisNode to increment its OwnSeqNum are described
in Section 5.3.
Perkins & Chakeres Expires September 13, 2012 [Page 12]
Internet-Draft AODVv2 March 2012
5.1.2. Numerical Operations on OwnSeqNum
When ThisNode increments its OwnSeqNum it MUST do so by treating the
sequence number value as an unsigned number.
5.1.3. OwnSeqNum Rollover
Incrementing an OwnSeqNum whose value is the largest largest possible
number representable as a 16-bit unsigned integer (i.e., 65,535),
SHOULD be set to one (1). In other words, the sequence number after
65,535 is 1.
5.1.4. Actions After OwnSeqNum Loss
An AODVv2 router SHOULD maintain its sequence number in persistent
storage.
If an AODVv2 router's OwnSeqNum is lost, it MUST take certain actions
to avoid creating routing loops. To prevent this possibility after
OwnSeqNum loss an AODVv2 router MUST wait for at least
ROUTE_DELETE_TIMEOUT before fully participating in the AODVv2 routing
protocol. If an AODVv2 control message is received during this
waiting period, the AODVv2 router SHOULD handle it normally but MUST
NOT transmit or retransmit any AODVv2 messages. If a data packet is
received for forwarding to another destination during this waiting
period, the AODVv2 router MUST generate a RERR message indicating
that this route is not available and reset its waiting timeout. At
the end of the waiting period the AODVv2 router sets its OwnSeqNum to
one (1) and begins participating.
The longest a node need wait is ROUTE_SEQNUM_AGE_MAX_TIMEOUT. At the
end of the maximum waiting period a node SHOULD set its OwnSeqNum to
one (1) and begins participating.
5.2. AODVv2 Routing Table Operations
5.2.1. Judging Routing Information's Usefulness
Given a route table entry (Route.SeqNum, Route.Dist, and
Route.Broken) and new incoming routing information for a particular
node in a RteMsg (Node.SeqNum, Node.Dist, and RteMsg message type -
RREQ/RREP), the quality of the new routing information is evaluated
to determine its usefulness. Incoming routing information is
classified as follows:
Perkins & Chakeres Expires September 13, 2012 [Page 13]
Internet-Draft AODVv2 March 2012
1. Stale
If Node.SeqNum - Route.SeqNum < 0 (using signed 16-bit arithmetic)
the incoming information is stale. Using stale routing
information is not allowed, since doing so might result in routing
loops.
(Node.SeqNum - Route.SeqNum < 0)
using signed 16-bit arithmetic
2. Loop-possible
If Node.SeqNum == Route.SeqNum the incoming information may cause
loops if used; in this case additional information MUST be
examined. If Route.Dist or Node.Dist is unknown or zero (0), then
the routing information is loop-possible. If Node.Dist >
Route.Dist + 1, then the routing information is loop-possible.
Using loop-possible routing information is not allowed, otherwise
routing loops may be formed.
(Node.SeqNum == Route.SeqNum) AND
((Node.Dist is unknown) OR
(Route.Dist is unknown) OR
(Node.Dist > Route.Dist + 1))
3. Disfavored or equivalent
In case of known equal SeqNum, the information is disfavored in
multiple cases: (case i) if Node.Dist == Route.Dist + 1 (it is a
greater distance route) AND Route.Broken == false; (case ii) if
Node.Dist == Route.Dist (equal distance route) AND Route.Broken ==
false AND this RteMsg is a RREQ. This condition reduces the
number of RREQ flooded by stopping forwarding of RREQ with
equivalent distance.
((Node.SeqNum == Route.SeqNum) AND
(((Node.Dist == Route.Dist + 1) AND (Route.Broken == false)) OR
((Node.Dist == Route.Dist) AND
(RteMsg is RREQ) AND (Route.Broken == false))))
4. Preferable
Incoming routing information that does not match any of the above
criteria is loop-free and better than the information existing in
the routing table. Information is always preferable if
Node.SeqNum - Route.SeqNum > 0 (using signed 16-bit arithmetic).
In the case of equal sequence numbers, the information is
preferable in multiple cases: (case i) if Node.Dist < Route.Dist;
(case ii) if Node.Dist == Route.Dist + 1 AND Route.Broken == true
(a broken route is being repaired); (case iii) if Node.Dist ==
Route.Dist AND it is a RREP (RREP with equal distance are
forwarded) OR Route.Broken == true (a broken route is being
Perkins & Chakeres Expires September 13, 2012 [Page 14]
Internet-Draft AODVv2 March 2012
repaired). For completeness, we provide the following (optimized)
pseudo-code.
(Node.SeqNum - Route.SeqNum > 0) OR
using signed 16-bit arithmetic
((Node.SeqNum == Route.SeqNum) AND
((Node.Dist < Route.Dist) OR
((Node.Dist == Route.Dist + 1) AND (Route.Broken == true)) OR
((Node.Dist == Route.Dist) AND
((RteMsg is RREP) OR (Route.Broken == true)))))
5.2.2. Creating or Updating a Route Table Entry with Received
Preferable Routing Information
The route table entry is populated with the following information:
1. the Route.Address is set to Node.Address,
2. the Route.Prefix is set to the Node.Prefix.
3. the Route.SeqNum is set to the Node.SeqNum,
4. the Route.NextHopAddress is set to the node that transmitted this
AODVv2 RteMsg packet (i.e., the IP.SourceAddress),
5. the Route.NextHopInterface is set to the interface that this
AODVv2 packet was received on,
6. the Route.Broken flag is set to false,
7. if known, the Route.Dist is set to the Node.Dist,
Fields without known values are not populated with any value.
The timer for the minimum delete timeout (ROUTE_AGE_MIN) is set to
ROUTE_AGE_MIN_TIMEOUT. The timer for the maximum delete timeout
(ROUTE_SEQNUM_AGE_MAX) is set to Node.AddTLV.VALIDITY_TIME [RFC5497]
if included; otherwise, ROUTE_SEQNUM_AGE_MAX is set to
ROUTE_SEQNUM_AGE_MAX_TIMEOUT. The usage of these timers and others
are described in Section 5.2.3.
At this point, a forwarding route has been created and the
Route.Forwarding flag set. Afterward, the route can be used to send
any queued data packets and forward any incoming data packets for
Route.Address. This route also fulfills any outstanding route
discovery attempts for Node.Address.
Perkins & Chakeres Expires September 13, 2012 [Page 15]
Internet-Draft AODVv2 March 2012
5.2.3. Route Table Entry Timeouts
5.2.3.1. Minimum Delete Timeout (ROUTE_AGE_MIN)
When an AODVv2 router transmits a RteMsg, other AODVv2 routers expect
the transmitting AODVv2 router to have a forwarding route to the
RteMsg originator. After updating a route table entry, it SHOULD be
maintained for at least ROUTE_AGE_MIN. Failure to maintain the
information might result in lost messages/packets, or in the worst
case scenario several duplicate messages.
After the ROUTE_AGE_MIN timeout a route can safely be deleted.
5.2.3.2. Maximum Sequence Number Delete Timeout (ROUTE_SEQNUM_AGE_MAX)
Sequence number information is time sensitive, and MUST be deleted
after a time in order to ensure loop-free routing.
After the ROUTE_SEQNUM_AGE_MAX timeout a route's sequence number
information MUST be discarded.
5.2.3.3. Recently Used Timeout (ROUTE_USED)
When a route is used to forward data packets, this timer is set to
expire after ROUTE_USED_TIMEOUT. This operation is also discussed in
Section 5.5.2.
If a route has not been used recently, then a timer for ROUTE_DELETE
is set to ROUTE_DELETE_TIMEOUT.
5.2.3.4. Delete Information Timeout (ROUTE_DELETE)
As time progresses the likelihood that old routing information is
useful decreases, especially if the network nodes are mobile.
Therefore, old information SHOULD be deleted.
After the ROUTE_DELETE timeout if a forwarding route exists it SHOULD
be removed, and the routing table entry SHOULD also be deleted.
5.3. Routing Messages
5.3.1. RREQ Creation
Before an AODVv2 router creates a RREQ it SHOULD increment its
OwnSeqNum by one (1) according to the rules specified in Section 5.1.
Incrementing OwnSeqNum will ensure that all nodes with existing
routing information will consider this new information preferable to
existing routing table information. If the sequence number is not
Perkins & Chakeres Expires September 13, 2012 [Page 16]
Internet-Draft AODVv2 March 2012
incremented, certain AODVv2 routers might not consider this
information preferable, if they have existing better routing
information.
First, ThisNode adds the AddBlk.TargetNode.Address to the RREQ; the
unicast IP Destination Address for which a forwarding route does not
exist.
If a previous value of the TargetNode.SeqNum is known (from a routing
table entry using longest-prefix matching), it SHOULD be placed in
TargetNode.AddTLV.SeqNum in all but the last RREQ attempt. If a
TargetNode.SeqNum is not included, it is assumed to be unknown by
handling nodes. This operation ensures that no intermediate AODVv2
routers reply, and ensures that the TargetNode's AODVv2 router
increments its sequence number.
Next, the node adds AddBlk.OrigNode.Address, its prefix, and the
OrigNode.AddTLV.SeqNum (OwnSeqNum) to the RteMsg.
The OrigNode.Address is the address of the source for which this
AODVv2 router is initiating this route discovery. The
OrigNode.Address MUST be a unicast address. This information will be
used by nodes to create a route toward the OrigNode, enabling
delivery of a RREP, and eventually used for proper forwarding of data
packets.
If OrigNode.Dist is included it is set to a number greater than zero
(0).
The MsgHdr.HopLimit SHOULD be set to MSG_HOPLIMIT.
For RREQ, the MsgHdr.HopLimit MAY be set in accordance with an
expanding ring search as described in [RFC3561] to limit the RREQ
propagation to a subset of the local network and possibly reduce
route discovery overhead.
The IP.DestinationAddress for multicast RREQ is set to LL-MANET-
Routers. For links that do not support multicast or situations in
which unicast messaging is preferred, the IP.DestinationAddress for
unicast RREQ is set to the NextHopAddress.
5.3.2. RREP Creation
First, the AddBlk.TargetNode.Address is added to the RREP. The
TargetNode is the ultimate destination of this RREP; the RREQ
OrigNode.Address.
Next, AddBlk.OrigNode.Address and prefix are added to the RREP. The
Perkins & Chakeres Expires September 13, 2012 [Page 17]
Internet-Draft AODVv2 March 2012
AddBlk.OrigNode.Address is the RREQ TargetNode.Address. The
AddBlk.OrigNode.Address MUST be a unicast IP address. ThisNode
SHOULD advertise the largest known prefix containing
AddBlk.OrigNode.Address.
When the RteMsg TargetNode's AODVv2 router creates a RREP, if the
TargetNode.SeqNum was not included in the RREQ, ThisNode MUST
increment its OwnSeqNum by one (1) according to the rules specified
in Section 5.1.
If TargetNode.SeqNum was included in the RteMsg and TargetNode.SeqNum
- OwnSeqNum < 0 (using signed 16-bit arithmetic), OwnSeqNum SHOULD be
incremented by one (1) according to the rules specified in
Section 5.1.
If TargetNode.SeqNum is included in the RteMsg and TargetNode.SeqNum
== OwnSeqNum (using signed 16-bit arithmetic) and OrigNode.Dist will
not be included in the RREP being generated, OwnSeqNum SHOULD be
incremented by one (1) according to the rules specified in
Section 5.1.
If OwnSeqNum is not incremented the routing information might be
considered stale. In this case, the RREP might not reach the RREP
Target.
After any of the sequence number operations above, the RREP
OrigNode.AddTLV.SeqNum (OwnSeqNum) MUST also be added to the RREP.
Other AddTLVs in the RREP for the OrigNode and TargetNode SHOULD be
included and set accordingly. If OrigNode.Dist is included it is set
to a number greater than zero (0) and less than or equal to 65,535.
The Distance value will influence judgment of the routing information
(Section 5.2.1) against known information at other AODVv2 routers
that handle this RteMsg.
The MsgHdr.HopLimit is set to MSG_HOPLIMIT.
The IP.DestinationAddress for RREP is set to the IP address of the
Route.NextHopAddress for the route to the RREP TargetNode.
5.3.3. RteMsg Handling
First, ThisNode examines the RteMsg to ensure that it contains the
required information: MsgHdr.HopLimit, AddBlk.TargetNode.Address,
AddBlk.OrigNode.Address, and OrigNode.AddTLV.SeqNum. If the required
information do not exist, the message is discarded and further
processing stopped.
Perkins & Chakeres Expires September 13, 2012 [Page 18]
Internet-Draft AODVv2 March 2012
Next, ThisNode MAY selectively attend to messages based upon
information in the message. ThisNode SHOULD only handle messages
from adjacent AODVv2 routers. If ThisNode chooses not to handle this
message, the message is discarded and further processing stopped.
ThisNode checks if the AddBlk.OrigNode.Address is a valid multihop-
capable (e.g. site or global scope) unicast address. If the address
is not a valid unicast address, the message is discarded and further
processing stopped.
ThisNode also checks whether AddBlk.OrigNode.Address is an address
handled by this AODVv2 router. If this node is the originating
AODVv2 router, the RteMsg is dropped.
ThisNode checks if the AddBlk.TargetNode.Address is a valid multihop-
capable unicast address. If the address is not a valid unicast
address, the message is discarded and further processing stopped.
Next, ThisNode checks whether its routing table has an entry to the
AddBlk.OrigNode.Address using longest-prefix matching [RFC1812]. If
a route with a valid Route.SeqNum does not exist, then the new
routing information is considered preferable and a new route table
entry is created and updated as described in Section 5.2.2. If a
route table entry does exists and it has a known Route.SeqNum, the
incoming routing information is compared with the route table entry
following the procedure described in Section 5.2.1. If the incoming
routing information is considered preferable, the route table entry
is updated as described in Section 5.2.2.
For each address (except the TargetNode) in the RteMsg that includes
AddTLV.Dist information, the AddTLV.Dist information MAY be
incremented. If the resulting Distance value for the OrigNode is
greater than 65,535, the message is discarded. If the resulting
Distance value for another node is greater than 65,535, the
associated address and its information are removed from the RteMsg.
The updated Distance value will influence judgment of the routing
information (Section 5.2.1).
After handling the OrigNode's routing information, then each address
that is not the TargetNode MAY be considered for creating and
updating routes. Creating and updating routes to other nodes can
eliminate RREQ for those IP destinations, in the event that data
needs to be forwarded to the IP destination(s) now or in the near
future.
For each of the additional addresses considered, ThisNode first
checks the that the address is a multihop-capable unicast address.
If the address is not a unicast address, the address and all related
Perkins & Chakeres Expires September 13, 2012 [Page 19]
Internet-Draft AODVv2 March 2012
information MUST be removed.
If the routing table does not have a matching route with a known
Route.SeqNum for this additional address using longest-prefix
matching, then a route is created and updated as described in
Section 5.2.2. If a route table entry exists with a known
Route.SeqNum, the incoming routing information is compared with the
route table entry following the procedure described in Section 5.2.1.
If the incoming routing information is considered preferable, the
route table entry is updated as described in Section 5.2.2.
If the routing information for an AdditionalNode.Address is not
considered preferable, then it is removed from the RteMsg. Removing
this information ensures that the information is not propagated.
At this point, if the routing information for the OrigNode was not
preferable then this RteMsg SHOULD be discarded and no further
processing of this message SHOULD be performed.
If the ThisNode is the AODVv2 router responsible for the TargetNode
and this RteMsg is a RREQ, then ThisNode responds with a RREP to the
RREQ OrigNode (the new RREP's TargetNode). The procedure for issuing
a new RREP is described in Section 5.3.2. At this point, ThisNode
need not perform any more operations for the RteMsg being processed.
As an alternative to issuing a RREP, ThisNode MAY choose to
distribute routing information about ThisNode (the RREQ TargetNode)
more widely. That is, ThisNode MAY optionally perform a route
discovery; by issuing a RREQ with ThisNode listed as the TargetNode,
using the procedure in Section 5.3.1. At this point, ThisNode need
not perform any more operations for the RteMsg being processed.
If the resulting Distance value for the OrigNode is greater than
65,535, the message is discarded. If the resulting Distance value
for another node is greater than 65,535, the associated address and
its information are removed from the RteMsg.
Next, the MsgHdr.HopLimit is decremented by one (1). If this
RteMsg's MsgHdr.HopLimit is greater than or equal to one (1),
ThisNode is not the TargetNode, AND this RteMsg is a RREQ, then the
current RteMsg (altered by the procedure defined above) SHOULD be
sent to the IP.DestinationAddress LL-MANET-Routers [RFC5498]. If the
RREQ is unicast, the IP.DestinationAddress is set to the
NextHopAddress.
If this RteMsg's MsgHdr.HopLimit is greater than or equal to one (1),
ThisNode is not the TargetNode, AND this RteMsg is a RREP, then the
current RteMsg is sent to the Route.NextHopAddress for the RREP's
Perkins & Chakeres Expires September 13, 2012 [Page 20]
Internet-Draft AODVv2 March 2012
TargetNode.Address. If no forwarding route exists to
TargetNode.Address, then a RERR SHOULD be issued to the OrigNode of
the RREP.
By sending the updated RteMsg, ThisNode advertises that it will route
for addresses contained in the outgoing RteMsg based on the
information enclosed. ThisNode MAY choose not to send the RteMsg,
though not resending this RteMsg could decrease connectivity in the
network or result in a non-shortest distance path.
Some examples of why ThisNode might choose to not re-issue a RteMsg
are: if ThisNode does not want to advertise routing for the contained
addresses because it is already heavily loaded; if ThisNode has
already issued nearly identical routing information (e.g. ThisNode
had recently issued a RteMsg with nearly the same distance); or if
ThisNode is low on energy and does not want to expend energy for
control message sending or packet forwarding. The exact
circumstances producing such behavior are not specified in this
document.
5.4. Route Discovery
When a source's AODVv2 router needs to forward a data packet on
behalf of an attached node and it does not have a forwarding route to
the data packet's unicast IP destination address, ThisNode sends a
RREQ (described in Section 5.3.1) to discover a route to the
particular destination (TargetNode).
After issuing a RREQ, the OrigNode AODVv2 router waits for a route to
be created to the TargetNode. If a route is not created within
RREQ_WAIT_TIME, ThisNode may again try to discover a route by issuing
another RREQ using the procedure defined in Section 5.3.1 again.
Route discovery SHOULD be considered failed after
DISCOVERY_ATTEMPTS_MAX and the final RREQ's corresponding
RREQ_WAIT_TIME.
To reduce congestion in a network, repeated attempts at route
discovery for a particular TargetNode SHOULD utilize an exponential
backoff.
For example, the first time an AODVv2 router issues a RREQ, it waits
RREQ_WAIT_TIME for a route to the TargetNode. If a route is not
found within that time, the AODVv2 router MAY send another RREQ. If
a route is not found within two (2) times the current waiting time,
another RREQ MAY be sent. No more than DISCOVERY_ATTEMPTS_MAX route
discovery attempts SHOULD be made before considering route discovery
for this destination to have failed. For each additional attempt,
the waiting time for the previous RREQ is multiplied by two (2) so
Perkins & Chakeres Expires September 13, 2012 [Page 21]
Internet-Draft AODVv2 March 2012
that the waiting time conforms to a binary exponential backoff.
Data packets awaiting a route SHOULD be buffered by the source's
AODVv2 router. This buffer SHOULD have a fixed limited size
(BUFFER_SIZE_PACKETS or BUFFER_SIZE_BYTES) and older data packets
SHOULD be discarded first.
Buffering of data packets can have both positive and negative
effects, and therefore buffer settings (BUFFER_DURING_DISCOVERY)
SHOULD be administratively configurable or intelligently controlled.
If a route discovery attempt has failed (i.e. an attempt or multiple
attempts have been made without receiving a RREP) to find a route to
the TargetNode, any data packets buffered for the corresponding
TargetNode are dropped and a Destination Unreachable ICMP message
SHOULD be delivered to the source.
5.5. Route Maintenance
A RERR SHOULD be issued if a data packet is to be forwarded and it
cannot be delivered to the next-hop because no forwarding route for
the IP.DestinationAddress exists; RERR generation is described in
Section 5.5.3.
Upon this condition, an ICMP Destination Unreachable message SHOULD
NOT be generated unless this router is responsible for the
IP.DestinationAddress and that IP.DestinationAddress is known to be
unreachable.
In addition to inability to forward a data packet, a RERR SHOULD be
issued immediately after detecting a broken link (see Section 5.5.1)
of a forwarding route to quickly notify AODVv2 routers that certain
routes are no longer available. If a newly unavailable route has not
been used recently (indicated by ROUTE_USED), the RERR SHOULD NOT be
generated.
5.5.1. Active Next-hop Router Adjacency Monitoring
Nodes MUST monitor connectivity to adjacent next-hop AODVv2 routers
on forwarding routes. This monitoring can be accomplished by one or
several mechanisms, including:
o Neighborhood discovery [I-D.ietf-manet-nhdp]
o Route timeout
o Lower layer feedback that a particular adjacent router is no
longer reachable
Perkins & Chakeres Expires September 13, 2012 [Page 22]
Internet-Draft AODVv2 March 2012
o Other monitoring mechanisms or heuristics
Upon determining that a next-hop AODVv2 router is unreachable,
ThisNode MUST remove the affected forwarding routes (those with an
unreachable next-hop) and unset the Route.Forwarding flag. ThisNode
also flags the associated routes in AODVv2's routing table as Broken.
For each broken route the timer for ROUTE_DELETE is set to
ROUTE_DELETE_TIMEOUT.
5.5.2. Updating Route Lifetimes During Packet Forwarding
To avoid removing the forwarding route to reach the IP.SourceAddress,
ThisNode SHOULD set the "ROUTE_USED" timeout to the value
ROUTE_USED_TIMEOUT for the route to the IP.SourceAddress upon
receiving a data packet. If the timer for ROUTE_DELETE is set, it is
removed.
To avoid removing the forwarding route to the IP.DestinationAddress
that is being used, ThisNode SHOULD set the "ROUTE_USED" timeout to
the value ROUTE_USED_TIMEOUT for the route to the
IP.DestinationAddress upon sending a data packet. If the timer for
ROUTE_DELETE is set, it is removed.
5.5.3. RERR Generation
A RERR informs AODVv2 routers that a route to certain destinations is
not available through ThisNode.
When creating a new RERR, the address of the first UnreachableNode
(IP.DestinationAddress from a data packet or RREP.TargetNode.Address)
is inserted into an Address Block AddBlk.UnreachableNode.Address. If
a prefix is known for the UnreachableNode.Address, it SHOULD be
included. Otherwise, the UnreachableNode.Address is assumed to be a
host address with a full length prefix. If a value for the
UnreachableNode's SeqNum (UnreachableNode.AddTLV.SeqNum) is known, it
SHOULD be placed in the RERR. The MsgHdr.HopLimit is set to
MSG_HOPLIMIT.
If SeqNum information is not known or not included in the RERR, all
nodes handling the RERR will assume their routing information
associated with the UnreachableNode is no longer valid and flag those
routes as broken.
A multicast RERR is sent to the IP.DestinationAddress LL-MANET-
Routers [RFC5498]. Sending the RERR to the LL-MANET-Routers address
notifies all nearby AODVv2 routers that might depend on the now
broken link. If the RERR is unicast, the IP.DestinationAddress is
set to the NextHopAddress.
Perkins & Chakeres Expires September 13, 2012 [Page 23]
Internet-Draft AODVv2 March 2012
At this point, the packet or message that forced generation of this
RERR SHOULD be discarded.
5.5.4. RERR Handling
First, ThisNode examines the RteMsg to ensure that it contains the
required information: MsgHdr.HopLimit and
AddBlk.UnreachableNode.Address. If the required information do not
exist, the message is discarded and further processing stopped.
Next, ThisNode MAY selectively handle messages based upon information
in the message. ThisNode MAY choose to only handle messages from
adjacent AODVv2 routers. If ThisNode chooses not to handle this
message, the message is discarded and further processing stopped.
When an AODVv2 router handles a RERR, it examines each
UnreachableNode's information. The attending AODVv2 router removes
the forwarding route, unsets the Route.Forwarding flag, sets the
Route.Broken flag, and the timer for ROUTE_DELETE is set to
ROUTE_DELETE_TIMEOUT for each UnreachableNode.Address found using
longest prefix matching that meets all of the following conditions:
1. The UnreachableNode.Address is a multihop-capable unicast
address.
2. The Route.NextHopAddress is the same as the RERR
IP.SourceAddress.
3. The Route.NextHopInterface is the same as the interface on which
the RERR was received.
4. The Route.SeqNum is zero (0), unknown, OR the
UnreachableNode.SeqNum is zero (0), unknown, OR Route.SeqNum -
UnreachableNode.SeqNum <= 0 (using signed 16-bit arithmetic).
During handling if Route.SeqNum is zero (0) or unknown and
UnreachableNode.SeqNum exists in the RERR and is not zero (0), then
Route.SeqNum MAY be set to UnreachableNode.SeqNum. Setting
Route.SeqNum can reduce future RERR handling and forwarding.
Each UnreachableNode that did not result in a broken route is removed
from the RERR, since propagation of this information will not result
in any benefit.
Each UnreachableNode that did result in a broken route SHOULD remain
in the RERR.
If any UnreachableNode was removed, all other information (AddTLVs)
Perkins & Chakeres Expires September 13, 2012 [Page 24]
Internet-Draft AODVv2 March 2012
associated with the removed address(es) MUST also be removed.
After handling if Route.SeqNum is known and an UnreachableNode.SeqNum
is not included in the RERR, then Route.SeqNum (i.e.
UnreachableNode.SeqNum) MAY be added to the RERR. Including
UnreachableNode.SeqNum can reduce future RERR handling and
forwarding.
If no UnreachableNode addresses remain in the RERR, no other handling
is required and the RERR is discarded.
If handling continues, the MsgHdr.HopLimit is decremented by one (1).
Further, if this RERR's new MsgHdr.HopLimit is greater than one (1)
and at least one unreachable node address remains in the RERR, then
the updated RERR SHOULD be sent.
A multicast RERR is sent to the IP.DestinationAddress LL-MANET-
Routers [RFC5498]. If the RERR is unicast, the IP.DestinationAddress
is set to the NextHopAddress.
5.6. Unknown Message and TLV Types
If a message with an unknown type is received, the message is
discarded.
For handling of messages that contain unknown TLV types, the default
behavior is to leave the information in control messages unmodified.
Although, this behavior (UNKNOWN_TYPES) MAY be administratively
controlled.
5.7. Advertising Network Addresses
AODVv2 routers specify the prefix length for each advertised address.
Any nodes (other than the advertising AODVv2 router) within the
advertised prefix MUST NOT participate in the AODVv2 protocol
directly. For example, advertising 192.0.2.1 with a prefix length of
24 indicates that all nodes with the matching 192.0.2.X are reachable
through this AODVv2 router.
5.8. Simple Internet Attachment
Simple Internet attachment consists of a stub network of AODVv2
routers connected to the Internet via a single Internet AODVv2 router
(IDR).
AODVv2 routers, and hosts behind these routers, wishing to be
reachable from hosts on the Internet MUST have IP addresses within
the IDR's routable and topologically correct prefix (e.g.
Perkins & Chakeres Expires September 13, 2012 [Page 25]
Internet-Draft AODVv2 March 2012
192.0.2.0/24).
The IDR is responsible for generating RREQ to find nodes within the
AODVv2 Region on behalf of nodes on the Internet, as well as
responding to route requests from the AODVv2 region on behalf of the
nodes on the Internet.
/--------------------------\
/ Internet \
\ /
\------------+-------------/
|
Routable & |
Topologically |
Correct |
Prefix |
+-----+------+
| Internet |
/------| AODVv2 |-------\
/ | Router | \
/ |192.0.2.1/32| \
| |Responsible | |
| | for | |
| |AODVv2 Region | |
| |192.0.2.0/24| |
| +------------+ |
| +--------------+ |
| | AODVv2 Router | |
| | 192.0.2.2/32 | |
| +--------------+ |
| +--------------+ |
| | AODVv2 Router | |
| | 192.0.2.3/32 | |
\ +--------------+ /
\ /
\---------------------------/
Figure 1: Simple Internet Attachment Example
When an AODVv2 router within the AODVv2 Region wants to discover a
route to a node on the Internet, it uses the normal AODVv2 route
discovery for that IP Destination Address. The IDR is responsible
for properly responding to RREQ on behalf of the Internet
destination.
When a packet from a node on the Internet destined for a node in the
AODVv2 region reaches the IDR, if the IDR does not have a route to
that destination it will perform normal AODVv2 route discovery for
Perkins & Chakeres Expires September 13, 2012 [Page 26]
Internet-Draft AODVv2 March 2012
that destination.
5.9. Multiple Interfaces
AODVv2 may be used with multiple interfaces; therefore, the
particular interface over which packets arrive MUST be known whenever
a packet is received. Whenever a new route is created, the interface
through which the Route.Address can be reached is also recorded in
the route table entry.
When multiple interfaces are available, a node transmitting a
multicast packet with IP.DestinationAddress set to LL-MANET-Routers
SHOULD send the packet on all interfaces that have been configured
for AODVv2 operation.
Similarly, AODVv2 routers should subscribe to LL-MANET-Routers on all
their AODVv2 interfaces.
5.10. AODVv2 Control Packet/Message Generation Limits
To ensure predictable control overhead, AODVv2 router's rate of
packet/message generation SHOULD be limited. The rate and algorithm
for limiting messages (CONTROL_TRAFFIC_LIMITS) is left to the
implementor and should be administratively configurable or
intelligently controlled. AODVv2 control messages SHOULD be
discarded in the following order of preference: RREQ, RREP, and
finally RERR.
6. Administratively Configured Parameters and Timer Values
AODVv2 contains several parameters which MUST be administratively
configured. The list of these follows:
Required Administratively Configured Parameters
+------------------------+------------------------------------------+
| Name | Description |
+------------------------+------------------------------------------+
| RESPONSIBLE_ADDRESSES | List of addresses or routing prefixes, |
| | for which this AODVv2 router is |
| | responsible. If, RESPONSIBLE_ADDRESSES |
| | is zero, this AODVv2 router is only |
| | responsible for its own addresses. |
| AODVv2_INTERFACES | List of the interfaces participating in |
| | AODVv2 routing protocol. |
+------------------------+------------------------------------------+
Perkins & Chakeres Expires September 13, 2012 [Page 27]
Internet-Draft AODVv2 March 2012
Table 2
AODVv2 contains a number of timers. The default timing parameter
values follow:
Default Timing Parameter Values
+------------------------------+-------------------+
| Name | Value |
+------------------------------+-------------------+
| ROUTE_TIMEOUT | 5 seconds |
| ROUTE_AGE_MIN_TIMEOUT | 1 second |
| ROUTE_SEQNUM_AGE_MAX_TIMEOUT | 60 seconds |
| ROUTE_USED_TIMEOUT | ROUTE_TIMEOUT |
| ROUTE_DELETE_TIMEOUT | 2 * ROUTE_TIMEOUT |
| ROUTE_RREQ_WAIT_TIME | 2 seconds |
| UNICAST_MESSAGE_SENT_TIMEOUT | 1 second |
+------------------------------+-------------------+
Table 3
The above timing parameter values work well for small and medium
well-connected networks with moderate topology changes.
The timing parameters SHOULD be administratively configurable for the
network where AODVv2 is used. Ideally, for networks with frequent
topology changes the AODVv2 parameters should be adjusted using
either experimentally determined values or dynamic adaptation. For
example, in networks with infrequent topology changes
ROUTE_USED_TIMEOUT may be set to a much larger value.
Default Parameter Values
+------------------------+-------+----------------------------------+
| Name | Value | Description |
+------------------------+-------+----------------------------------+
| MSG_HOPLIMIT | 10 | This value MUST be larger than |
| | hops | the AODVv2 network diameter. |
| | | Otherwise, routing messages may |
| | | not reach their intended |
| | | destinations. |
| DISCOVERY_ATTEMPTS_MAX | 3 | The number of route discovery |
| | | attempts to make before |
| | | indicating that a particular |
| | | address is not reachable. |
+------------------------+-------+----------------------------------+
Table 4
Perkins & Chakeres Expires September 13, 2012 [Page 28]
Internet-Draft AODVv2 March 2012
In addition to the above parameters and timing values, several
administrative options exist. These options have no influence on
correct routing behavior, although they may potentially reduce AODVv2
routing control messaging in certain situations. The default
behavior is to NOT enable any of these options; and although many of
these options can be administratively controlled, they may be better
served by intelligent control. The following table enumerates
several of the options.
Administratively Controlled Options
+-------------------------+-----------------------------------------+
| Name | Description |
+-------------------------+-----------------------------------------+
| BUFFER_DURING_DISCOVERY | Whether and how much data to buffer |
| | during route discovery. |
| UNKNOWN_TYPES | What action to take when an unknown TLV |
| | type is received. The default action |
| | is to forward this information |
| | unmodified. Another action would be to |
| | remove this information. |
| CONTROL_TRAFFIC_LIMITS | AODVv2 control messaging SHOULD be |
| | limited to avoid consuming all the |
| | network bandwidth. |
+-------------------------+-----------------------------------------+
Table 5
Note: several fields have limited size (bits or bytes) these sizes
and their encoding may place specific limitations on the values that
can be set. For example, MsgHdr.HopLimit is a 8-bit field and
therefore MSG_HOPLIMIT cannot be larger than 255.
7. IANA Considerations
In its default mode of operation, AODVv2 uses the UDP port MANET
[RFC5498] to carry protocol packets. AODVv2 also uses the link-local
multicast address LL-MANET-Routers [RFC5498].
This section specifies several message types, message tlv-types, and
address tlv-types.
Perkins & Chakeres Expires September 13, 2012 [Page 29]
Internet-Draft AODVv2 March 2012
7.1. AODVv2 Message Types Specification
AODVv2 Message Types
+------------------------+----------+
| Name | Type |
+------------------------+----------+
| Route Request (RREQ) | 10 - TBD |
| Route Reply (RREP) | 11 - TBD |
| Route Error (RERR) | 12 - TBD |
+------------------------+----------+
Table 6
7.2. Message and Address Block TLV Type Specification
Message TLV Types
+-------------------+------+--------+-------------------------------+
| Name | Type | Length | Value |
+-------------------+------+--------+-------------------------------+
| Unicast Response | 10 - | 0 | Indicates to the processing |
| Request | TBD | octets | node that the previous hop |
| | | | (IP.SourceAddress) expects a |
| | | | unicast message within |
| | | | UNICAST_MESSAGE_SENT_TIMEOUT. |
| | | | Any unicast packet will serve |
| | | | this purpose, and it MAY be |
| | | | an ICMP REPLY message. If a |
| | | | message is not sent, then the |
| | | | previous hop can assume that |
| | | | the link is unidirectional |
| | | | and MAY blacklist the link to |
| | | | this node. |
+-------------------+------+--------+-------------------------------+
Table 7
Perkins & Chakeres Expires September 13, 2012 [Page 30]
Internet-Draft AODVv2 March 2012
7.3. Address Block TLV Specification
Address Block TLV Types
+----------------+------------+----------+--------------------------+
| Name | Type | Length | Value |
+----------------+------------+----------+--------------------------+
| AODVv2 | 10 - TBD | up to 2 | The AODVv2 sequence num |
| Sequence | | octets | associated with this |
| Number | | | address. The sequence |
| (AODVv2SeqNum) | | | number may be the last |
| | | | known sequence number. |
| Distance | 11 - TBD | up to 2 | A metric of the distance |
| | | octets | traversed by the |
| | | | information associated |
| | | | with this address. |
| VALIDITY_TIME | 1[RFC5497] | | The maximum amount of |
| | | | time that information |
| | | | can be maintained before |
| | | | being deleted. The |
| | | | VALIDITY_TIME TLV is |
| | | | defined in [RFC5497]. |
+----------------+------------+----------+--------------------------+
Table 8
8. Security Considerations
The objective of the AODVv2 protocol is for each router to
communicate reachability information to addresses for which it is
responsible. Positive routing information (i.e. a route exists) is
distributed via RteMsgs and negative routing information (i.e. a
route does not exist) via RERRs. AODVv2 routers that handle these
messages store the contained information to properly forward data
packets, and they generally provide this information to other AODVv2
routers.
This section does not mandate any specific security measures.
Instead, this section describes various security considerations and
potential avenues to secure AODVv2 routing.
The most important security mechanisms for AODVv2 routing are
integrity/authentication and confidentiality.
In situations where routing information or router identity are
suspect, integrity and authentication techniques SHOULD be applied to
AODVv2 messages. In these situations, routing information that is
Perkins & Chakeres Expires September 13, 2012 [Page 31]
Internet-Draft AODVv2 March 2012
distributed over multiple hops SHOULD also verify the integrity and
identity of information based on originator of the routing
information.
A digital signature could be used to identify the source of AODVv2
messages and information, along with its authenticity. A nonce or
timestamp SHOULD also be used to protect against replay attacks.
S/MIME and OpenPGP are two authentication/integrity protocols that
could be adapted for this purpose.
In situations where confidentiality of AODVv2 messages is important,
cryptographic techniques can be applied.
In certain situations, like sending a RREP or RERR, an AODVv2 router
could include proof that it has previously received valid routing
information to reach the destination, at one point of time in the
past. In situations where routers are suspected of transmitting
maliciously erroneous information, the original routing information
along with its security credentials SHOULD be included.
Note that if multicast is used, any confidentiality and integrity
algorithms used must permit multiple receivers to handle the message.
9. 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-Royer for
her long time authorship of AODVv2. Additional thanks to Luke Klein-
Berndt, Pedro Ruiz, Fransisco Ros, Koojana Kuladinithi, Ramon
Caceres, Thomas Clausen, Christopher Dearlove, Seung Yi, Romain
Thouvenin, Tronje Krop, Henner Jakob, Alexandru Petrescu, Christoph
Sommer, Cong Yuan, Lars Kristensen, and Derek Atkins for reviewing of
AODVv2, as well as several specification suggestions.
Many good ideas from LOADng [I-D.clausen-lln-loadng] are shaping this
evolution of the [manet] reactive routing protocol specification.
Thanks are due to T. Clausen, A. Colin de Verdiere, J. Yi, A.
Niktash, Y. Igarashi, SATOH. H., and U. Herberg for their
development of LOADng and sharing details for ensuring
appropriateness of AODVv2 for LLNs.
10. References
Perkins & Chakeres Expires September 13, 2012 [Page 32]
Internet-Draft AODVv2 March 2012
10.1. Normative References
[RFC1812] Baker, F., "Requirements for IP Version 4 Routers",
RFC 1812, June 1995.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized Mobile Ad Hoc Network (MANET) Packet/Message
Format", RFC 5444, February 2009.
[RFC5497] Clausen, T. and C. Dearlove, "Representing Multi-Value
Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497,
March 2009.
[RFC5498] Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network
(MANET) Protocols", RFC 5498, March 2009.
10.2. Informative References
[I-D.chakeres-manet-manetid]
Chakeres, I., "MANET_ID TLV",
draft-chakeres-manet-manetid-03 (work in progress),
February 2008.
[I-D.clausen-lln-loadng]
Clausen, T., Verdiere, A., Yi, J., Niktash, A., Igarashi,
Y., and U. Herberg, "The LLN On-demand Ad hoc Distance-
vector Routing Protocol - Next Generation (LOADng)",
draft-clausen-lln-loadng-01 (work in progress),
October 2011.
[I-D.ietf-manet-nhdp]
Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
draft-ietf-manet-nhdp-15 (work in progress),
December 2010.
[I-D.ietf-ospf-multi-instance]
Lindem, A., Roy, A., and S. Mirtorabi, "OSPFv2 Multi-
Instance Extensions", draft-ietf-ospf-multi-instance-09
(work in progress), January 2012.
Perkins & Chakeres Expires September 13, 2012 [Page 33]
Internet-Draft AODVv2 March 2012
[Perkins99]
Perkins, C. and E. Belding-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.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
Demand Distance Vector (AODV) Routing", RFC 3561,
July 2003.
[RFC4728] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
Routing Protocol (DSR) for Mobile Ad Hoc Networks for
IPv4", RFC 4728, February 2007.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
Considerations in Mobile Ad Hoc Networks (MANETs)",
RFC 5148, February 2008.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
Appendix A. Changes since the Previous Version
o Protocol renamed to be AODVv2
o Intermediate RREPs (iRREPs) are to be put into new document.
Without iRREP, only the destination can respond to a RREQ.
o Precursor lists not supported, based on reported performance loss.
o Routing Messages MUST be originated with the MsgHdr.HopLimit set
to MSG_HOPLIMIT. Previously, this was not mandated.
o Adding additional unreachable destinations to RERR is not
specified in this document, to match LOADng behavior.
Appendix B. Proposed additional changes for LOADng conformance
Perkins & Chakeres Expires September 13, 2012 [Page 34]
Internet-Draft AODVv2 March 2012
o Revise message formats to be compatible with LOADng requirements,
removing RFC 5444 headers for minimal packet size
o Adding RREP-ACK message type instead of relying on reception of
arbitrary packets as sufficient response to establish
bidirectionality.
Appendix C. Shifting Responsibility for an Address Between AODVv2
Routers
Only one AODVv2 router within a routing region SHOULD be responsible
for a particular address at any time. If two AODVv2 routers
dynamically pass responsibility of an address correct AODVv2 routing
behavior must be observed. The AODVv2 router adding the new address
must wait for any exiting routing information about this address to
be purged from the network. Therefore, it must wait at least
ROUTER_SEQNUM_AGE_MAX_TIMEOUT after the previous AODVv2 router for
this address stopped participating and advertising routing
information on its behalf.
Authors' Addresses
Charles E. Perkins
Central Expressway
San Jose, CA 95050
USA
Phone: +1-408-421-1172
Email: charliep@computer.org
Ian D Chakeres
CenGen
9250 Bendix Road North
Columbia, Maryland 21045
USA
Email: ian.chakeres@gmail.com
URI: http://www.ianchak.com/
Perkins & Chakeres Expires September 13, 2012 [Page 35]
