draft-ietf-manet-aodv-01.txt   draft-ietf-manet-aodv-02.txt 
Mobile Ad Hoc Networking Working Group Charles Perkins Mobile Ad Hoc Networking Working Group Charles E. Perkins
INTERNET DRAFT Sun Microsystems INTERNET DRAFT Sun Microsystems Laboratories
10 August 1998 Elizabeth M. Royer 20 November 1998 Elizabeth M. Royer
University of California, Santa Barbara University of California, Santa Barbara
Ad Hoc On Demand Distance Vector (AODV) Routing Ad Hoc On Demand Distance Vector (AODV) Routing
draft-ietf-manet-aodv-01.txt draft-ietf-manet-aodv-02.txt
Status of This Memo Status of This Memo
This document is a submission by the Mobile Ad Hoc Networking Working This document is a submission by the Mobile Ad Hoc Networking Working
Group of the Internet Engineering Task Force (IETF). Comments should Group of the Internet Engineering Task Force (IETF). Comments should
be submitted to the manet@itd.nrl.navy.mil mailing list. be submitted to the manet@itd.nrl.navy.mil mailing list.
Distribution of this memo is unlimited. Distribution of this memo is unlimited.
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
skipping to change at page 1, line 45 skipping to change at page 1, line 45
Abstract Abstract
The Ad Hoc On-Demand Distance Vector (AODV) routing protocol is The Ad Hoc On-Demand Distance Vector (AODV) routing protocol is
intended for use by mobile nodes in an ad hoc network characterized intended for use by mobile nodes in an ad hoc network characterized
by frequent changes in link connectivity to each other caused by frequent changes in link connectivity to each other caused
by relative movement. It offers quick adaptation to dynamic by relative movement. It offers quick adaptation to dynamic
link conditions, low processing and memory overhead, low network link conditions, low processing and memory overhead, low network
utilization, and establishment of both unicast and multicast routes utilization, and establishment of both unicast and multicast routes
between sources and destinations which are loop free at all times. between sources and destinations which are loop free at all times.
It makes use of destination sequence numbers, which are a novel means It makes use of destination sequence numbers, which are a novel means
of ensuring loop freedom even in the face of anomalous delivery of ensuring loop freedom even in the face of anomalous delivery of
of routing control messages, and which solve classical problems routing control messages, and solving classical problems associated
associated with distance vector protocols, including the problem of with distance vector protocols, including the problem of ``counting
"counting to infinity". to infinity''.
Contents Contents
Status of This Memo i Status of This Memo i
Abstract i Abstract i
1. Introduction 2 1. Introduction 1
2. Overview 2 2. Overview 1
3. AODV Terminology 4 3. AODV Terminology 3
4. Route Request Message Format 6 4. Route Request (RREQ) Message Format 5
5. Route Reply Message Format 8 5. Route Reply (RREP) Message Format 6
6. Multicast Route Invalidation Message Format 10 6. Node Operation - Unicast 7
6.1. Maintaining Route Utilization Records . . . . . . . . . . 7
6.2. Generating Route Requests (RREQs) . . . . . . . . . . . . 8
6.3. Forwarding Route Requests . . . . . . . . . . . . . . . . 8
6.4. Generating Route Replies (RREPs) . . . . . . . . . . . . 9
6.5. Maintaining Local Connectivity . . . . . . . . . . . . . 10
6.6. Initiating Triggered Route Replies (Triggered RREPs) . . 11
7. Node Operation - Unicast 11 7. Multicast Route Activation (MACT) Message Format 12
7.1. Maintaining Route Utilization Records . . . . . . . . . . 11
7.2. Generating Route Requests . . . . . . . . . . . . . . . . 11
7.3. Forwarding Route Requests . . . . . . . . . . . . . . . . 12
7.4. Generating Route Replies . . . . . . . . . . . . . . . . 13
7.5. Generating Hello Messages . . . . . . . . . . . . . . . . 13
7.6. Initiating Triggered Route Replies . . . . . . . . . . . 14
7.7. Detecting Link Breakage . . . . . . . . . . . . . . . . . 15
8. Node Operation - Multicast 15 8. Node Operation - Multicast 13
8.1. Maintaining Multicast Tree Utilization Records . . . . . 15 8.1. Maintaining Multicast Tree Utilization Records . . . . . 13
8.2. Generating Multicast Route Requests . . . . . . . . . . . 15 8.2. Generating Multicast RREQs . . . . . . . . . . . . . . . 13
8.3. Forwarding Multicast Route Requests . . . . . . . . . . . 17 8.3. Forwarding Multicast Route Requests . . . . . . . . . . . 14
8.4. Generating Multicast Route Replies . . . . . . . . . . . 17 8.4. Generating Multicast Route Replies . . . . . . . . . . . 14
8.5. Route Deletion and Multicast Tree Pruning . . . . . . . . 18 8.5. Forwarding Route Replies . . . . . . . . . . . . . . . . 15
8.6. Repairing Link Breakages . . . . . . . . . . . . . . . . 20 8.6. Route Deletion and Multicast Tree Pruning . . . . . . . . 16
8.7. Initiating Triggered Route Replies . . . . . . . . . . . 22 8.7. Repairing Link Breakages . . . . . . . . . . . . . . . . 17
8.8. Initiating Triggered Route Replies . . . . . . . . . . . 19
9. Configuration Parameters 22 9. Quality of Service 20
10. Extensions 24 10. AODV and Aggregated Networks 20
11. Security Considerations 24 11. Using AODV with Other Networks 21
12. Extensions 21
12.1. Hello Interval Extension Format . . . . . . . . . . . . . 22
12.2. Multicast Group Leader Extension Format . . . . . . . . . 22
12.3. Multicast Group Information Extension Format . . . . . . 23
12.4. Maximum Delay Extension Format . . . . . . . . . . . . . 24
12.5. Minimum Bandwidth Extension Format . . . . . . . . . . . 24
13. Configuration Parameters 25
14. Security Considerations 26
1. Introduction 1. Introduction
The Ad-Hoc On-Demand Distance Vector (AODV) algorithm enables The Ad Hoc On-Demand Distance Vector (AODV) algorithm enables
dynamic, self-starting, multihop routing between participating mobile dynamic, self-starting, multihop routing between participating mobile
nodes wishing to establish and maintain an ad-hoc network. AODV nodes wishing to establish and maintain an ad hoc network. AODV
allows mobile nodes to obtain routes quickly for new destinations, allows mobile nodes to obtain routes quickly for new destinations,
and does not require nodes to maintain routes to destinations that and does not require nodes to maintain routes to destinations that
are not in active communication. Additionally, AODV allows for the are not in active communication. Additionally, AODV allows for the
formation of multicast groups whose membership is free to change formation of multicast groups whose membership is free to change
during the lifetime of the network. AODV also defines timely during the lifetime of the network. AODV allows mobile nodes to
responses to link breakages and changes in network topology. The respond quickly to link breakages and changes in network topology.
operation of AODV is loop free, and by avoiding the Bellman-Ford The operation of AODV is loop free, and by avoiding the Bellman-Ford
"counting to infinity" problem offers quick convergence when the ``counting to infinity'' problem offers quick convergence when the
ad-hoc network topology changes (typically, when a node moves in the ad hoc network topology changes (typically, when a node moves in the
network). network).
One distinguishing feature of AODV is its use of a destination One distinguishing feature of AODV is its use of a destination
sequence number for each route entry. The destination sequence sequence number for each route entry. The destination sequence
number is created by the destination or the multicast grouphead for number is created by the destination or the multicast group leader
any usable route information it sends to requesting nodes. Using for any usable route information it sends to requesting nodes. Using
destination sequence numbers ensures loop freedom and is simple to destination sequence numbers ensures loop freedom and is simple to
program. Given the choice between two routes to a destination, a program. Given the choice between two routes to a destination, a
requesting node always selects the one with the greatest sequence requesting node always selects the one with the greatest sequence
number. number.
Another feature of AODV is that link breakages cause immediate Another feature of AODV is that link breakages cause immediate
notifications to be sent to the affected set of nodes, but only that notifications to be sent to the affected set of nodes, but only that
set of nodes. set of nodes.
2. Overview 2. Overview
Route Requests (RREQs), Route Replies (RREPs), and Multicast Route Requests (RREQs), Route Replies (RREPs), and Multicast
Route Invalidations (MINVs) are the three message types defined Route Activations (MACTs) are the three message types defined by
by AODV. These message types are handled by UDP, and normal IP AODV. These message types are handled by UDP, and normal IP header
header processing applies. So, for instance, the requesting node processing applies. So, for instance, the requesting node is
is expected to use its IP address as the source IP address for the expected to use its IP address as the source IP address for the
messages. The range of dissemination of broadcast RREQs can be messages. The range of dissemination of broadcast RREQs can be
indicated by the TTL in the IP header. Fragmentation is typically indicated by the TTL in the IP header. Fragmentation is typically
not required. not required.
As long as the endpoints of a communication connection have valid As long as the endpoints of a communication connection have valid
routes to each other, AODV does not play any role. When a route routes to each other, AODV does not play any role. When a route
to a new destination (either a single node or a multicast group) to a new destination (either a single node or a multicast group)
is needed, the node uses a broadcast RREQ to find a route to the is needed, the node uses a broadcast RREQ to find a route to the
destination. A route can be determined when the request reaches destination. A route can be determined when the RREQ reaches either
either the destination itself, or an intermediate node with a fresh the destination itself, or an intermediate node with a fresh enough
enough route to the destination. The route is made available by route to the destination. The route is made available by unicasting
unicasting a RREP back to the source of the RREQ. Since each node a RREP back to the source of the RREQ. Since each node receiving the
receiving the request keeps track of a route back to the source of request caches a route back to the source of the request, the RREP
the request, the RREP can be unicast back from the destination to the can be unicast back from the destination to the source, or from any
source, or from any intermediate node that is able to satisfy the intermediate node that is able to satisfy the request back to the
request back to the source. In the multicast scenario, RREQs are source. RREQs are also used when a node wishes to join a multicast
also used when a node wishes to join a multicast group. A special group. A join flag in the RREQ informs nodes that when receiving the
join flag in the RREQ lets nodes know that when they receive the RREP, they are not just setting route pointers but are also setting
RREP, they are not just setting route pointers but are actually multicast route pointers, which will be used if the route is selected
grafting a branch on to the multicast tree. to be added onto the tree.
If a RREP is broadcast to the limited broadcast address In case AODV cannot rely on lower-level mechanisms for neighborhood
(255.255.255.255), and has a TTL of one, and a destination address determination, a special ``hello'' message is defined for use at the
of the node itself with metric 0, then it is received by all the network layer.
node's neighbors, and treated by them as a "hello" message. This
hello message is a local advertisement for the continued presence of For multicast groups, a ``Group Hello'' message is broadcast across
the node. Neighbors that are using routes through the broadcasting the network by the multicast group leader. The message carries
node will continue to mark the routes as valid. If hello messages multicast group and corresponding group leader IP addresses. This
from a particular node stop coming, the neighbor can assume that the
node has moved away. When that happens, the neighbor will mark the
link to the node as broken, and may trigger a notification to some of
its other neighbors that the link has broken. Hello messages also
carry multicast group and corresponding grouphead IP addresses. This
information is used for repairing multicast trees after a previously information is used for repairing multicast trees after a previously
disconnected portion of the network containing part of the multicast disconnected portion of the network containing part of the multicast
tree becomes reachable once again. tree becomes reachable once again.
Since AODV is a routing protocol, it deals with route table Since AODV is a routing protocol, it deals with route table
management. AODV assumes the following fields exist in each route management. Route table information must be kept even for ephemeral
table entry: routes, such as are created to temporarily keep track of reverse
paths towards nodes originating RREQs. AODV assumes the following
fields exist in each route table entry:
- Destination IP Address - Destination IP Address
- Destination Sequence Number - Destination Sequence Number
- Hop Count - Hop Count
- Next Hop - Next Hop
- Lifetime - Lifetime
- Routing Flags
This information must be kept even for ephemeral routes, such as are The following information is stored in each entry of the multicast
created to temporarily keep track of reverse paths towards nodes route table for multicast tree routes:
originating RREQs. For multicast tree routes, the Next Hop field is
likely to contain more than one entry. For multicast tree routes,
the following information is stored in each entry of the multicast
route table:
- Multicast Group IP Address - Multicast Group IP Address
- Multicast Grouphead IP Address - Multicast Group Leader IP Address
- Hop Count - Multicast Group Sequence Number
- Hop Count to next Multicast Group member
- Hop Count to Multicast Group leader
- Next Hops - Next Hops
- Lifetime - Lifetime
Here the Hop Count corresponds to the distance in hops to the
multicast grouphead. Also, the Next Hops field is a linked list of
structures, each of which contain the fields:
- Node IP Address The Next Hops field is a linked list of structures, each of which
- Active Flag contains the IP address of a neighbor in the multicast tree.
The Active Flag indicates whether the link has actually been set, or The IP Address of a Next Hop is only used to forward multicast
whether an MINV messages is still pending (see Section 8.5). messages after a MACT message has activated the route (see
Section 8.6).
3. AODV Terminology 3. AODV Terminology
This section defines terminology used with AODV that is not already This protocol specification uses conventional meanings [1] for
defined in [2]. capitalized words such as MUST, SHOULD, etc., to indicate requirement
levels for various protocol features. This section defines other
terminology used with AODV that is not already defined in [2].
multicast grouphead forwarding node
A node which agrees to forward packets destined for another
destination node, by retransmitting them to a next hop which is
closer to the destination along a path which has been set up
using routing control messages.
group leader
A node which is a member of the given multicast group and which A node which is a member of the given multicast group and which
is the first such group member in the connected portion of is the first such group member in the connected portion of
the network. This node is responsible for initializing the the network. This node is responsible for initializing and
multicast group destination sequence number. maintaining the multicast group destination sequence number.
multicast tree multicast tree
The tree containing all nodes which are members of the The tree containing all nodes which are members of the
multicast group and all nodes which are needed to connect the multicast group and all nodes which are needed to connect the
multicast group members. multicast group members.
multicast route table multicast route table
The table were ad-hoc nodes keep routing (including next hops) The table where ad hoc nodes keep routing (including next hops)
information for various multicast groups. information for various multicast groups.
request table request table
The table where ad-hoc nodes keep information concerning the The table where ad hoc nodes keep information concerning the
first node to request to join a multicast group. There is one first node to request to join a multicast group. There is one
entry in the table for each multicast group for which the node entry in the table for each multicast group for which the node
has received a RREQ with the J flag set (see Section 8.2. has received a RREQ with the `J' flag set (see Section 8.2).
route table
The table where ad-hoc nodes keep routing (including next hop)
information for various destinations. For IPv6, this can be
associated with the Destination Cache.
triggered update
An unsolicited route update transmitted by an intermediate node subnet leader
along the path to the destination.
This protocol specification uses conventional meanings [1] for A node which is a member of the subnet defined by a specific
capitalized words such as MUST, SHOULD, etc., to indicate requirement routing prefix, and which offers reachability to every other
levels for various protocol features. node with the same routing prefix. The subnet leader is
responsible for initializing and maintaining the destination
sequence number for every node on the subnet.
4. Route Request Message Format 4. Route Request (RREQ) Message Format
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |J|R| Reserved | Hop Count | | Type |J|R| Reserved | Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Broadcast ID | | Broadcast ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IP address | | Destination IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 6, line 28 skipping to change at page 5, line 28
| Source IP address | | Source IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Sequence Number | | Source Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of the Route Request message is illustrated above, and The format of the Route Request message is illustrated above, and
contains the following fields: contains the following fields:
Type xx Type xx
J Join flag; set when source node wants to join J Join flag; set when source node wants to join a
multicast group. multicast group.
R Repair flag; set when a node wants to initiate R Repair flag; set when a node wants to initiate
a repair to connect two previously disconnected a repair to connect two previously disconnected
portions of the multicast tree. portions of the multicast tree.
Reserved Sent as 0; ignored on reception. Reserved Sent as 0; ignored on reception.
Hop Count The number of hops from the Source IP Address to the Hop Count The number of hops from the Source IP Address to
node handling the request. the node handling the request.
Broadcast ID Broadcast ID A sequence number uniquely identifying the
A sequence number identifying the particular RREQ particular RREQ when taken in conjunction with the
uniquely when taken in conjunction with the source source node's IP address.
node's IP address.
Destination IP Address Destination IP Address
The IP address of the destination for which a route The IP address of the destination for which a route
is desired. is desired.
Destination Sequence Number Destination Sequence Number
The last sequence number received in the past by the The last sequence number received in the past by
source for any route towards the destination. the source for any route towards the destination.
Source IP Address Source IP Address
The IP address of the node which originated the Route The IP address of the node which originated the
Request. Route Request.
Source Sequence Number Source Sequence Number
The current sequence number for route information The current sequence number to be used for route
generated by the source of the route request. entries pointing to (and generated by) the source
of the route request.
Extension:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Multicast Grouphead IP Addr...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...Multicast Grouphead IP Addr | Multicast Group Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx
Length
The length of the extension field.
Multicast Grouphead IP Address
The IP Address of the Multicast Grouphead. This
extension is only used when a route to the Multicast
Grouphead is known.
Multicast Group Hop Count
The distance in hops of the node sending the RREQ from
the Multicast Grouphead. This extension is only used for
route rebuilding.
This extension is included only when a route to the multicast When a node wishes to repair a multicast tree, it appends the
grouphead is known. Multicast Group Leader extension (see Section 12.2).
5. Route Reply Message Format 5. Route Reply (RREP) Message Format
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |L| Reserved | Hop Count | | Type |L|R|U| Reserved| Prefix Size | Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IP address | | Destination IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Sequence Number | | Destination Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime | | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of the Route Reply message is illustrated above, and The format of the Route Reply message is illustrated above, and
contains the following fields: contains the following fields:
Type xx Type xx
Reserved L If the `L' bit is set, the message is a ``hello''
Sent as 0; ignored on reception.
Hop Count
The number of hops from the Source IP Address to the
Destination IP Address. For multicast route requests
this indicates the number of hops to the multicast
grouphead.
L If the 'L' bit is set, the message is a "hello"
message and contains a list of the node's neighbors. message and contains a list of the node's neighbors.
Destination IP Address R Repair flag; set when a node wants to initiate
The IP address of the destination for which a route is a repair to connect two previously disconnected
supplied. portions of the multicast tree.
Destination Sequence Number
The destination sequence number associated to the
route.
Lifetime The time for which nodes receiving the RREP consider
the route to be valid.
Extension:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Multicast Group IP Address ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Multicast Group IP Address | Multicast Grouphead IP Addr ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Multicast Grouphead IP Addr | Multicast Group Seq Number ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Multicast Group Seq Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx
Length
The length of the extension field.
Multicast Group IP Address
The IP Address of the Multicast Group.
Multicast Grouphead IP Address
The IP Address of the Multicast Grouphead.
Multicast Group Sequence Number
The current sequence number of the Multicast Group.
This extension is included when responding to a multicast group route
request.
6. Multicast Route Invalidation Message Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Reserved | Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of the Multicast Route Invalidation message is illustrated U Update flag; set in a Group Hello, when the group
above, and contains the following fields: leader information has changed.
Type xx Reserved Sent as 0; ignored on reception.
Reserved Prefix Size If nonzero, the Prefix Size specifies that the
Sent as 0; ignored on reception. indicated route vector may be used for any nodes
with the same routing prefix (as defined by the
Prefix Size) as the requested destination.
Hop Count Hop Count The number of hops from the Source IP Address to
The number of hops from the Source IP Address to the the Destination IP Address. For multicast route
Destination IP Address. requests this indicates the number of hops to the
multicast group leader.
Destination IP Address Destination IP Address
The IP address of the Multicast Group for which a route The IP address of the destination for which a route
is supplied. is supplied.
Destination Sequence Number Destination Sequence Number
The destination sequence number associated to the The destination sequence number associated to the
Multicast Group. route.
Source IP Address
The IP address of the node which originated the Route
Request.
Source Sequence Number
The current sequence number for route information
generated by the source of the route request.
Extensions:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Next Hop IP Address...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...Next Hop IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx
Length Lifetime The time for which nodes receiving the RREP consider
The length of the extension field the route to be valid.
Next Hop IP Address When the RREP is sent for a multicast destination, the Multicast
The IP address of the node chosen to be the next hop for Group Information extension is appended (see Section 12.3).
the multicast tree.
This extension is included when a source node wishes to invalidate Note that the Prefix Size allows a Subnet Leader to supply a route
all but one of the routes set up by RREPs. It is not included when a for every host in the subnet defined by the routing prefix, which
multicast tree member is pruning itself from the tree. is determined by the IP address of the Subnet Leader and the Prefix
Size. In order to make use of this feature, the Subnet Leader has to
guarantee reachability to all the hosts sharing the indicated subnet
prefix. The Subnet Leader is also responsible for maintaining the
Destination Sequence Number for the whole subnet.
7. Node Operation - Unicast 6. Node Operation - Unicast
This section describes the scenarios under which nodes generate This section describes the scenarios under which nodes generate
RREQs and RREPs for unicast communication, and how the fields in the RREQs and RREPs for unicast communication, and how the fields in the
message are handled. message are handled.
7.1. Maintaining Route Utilization Records 6.1. Maintaining Route Utilization Records
For each valid route maintained by a node (containing a finite For each valid route maintained by a node (containing a finite
metric), the node also maintains a list of those neighbors that are metric), the node also maintains a list of those neighbors that
actively using the route. This active-list of neighbors will receive are actively using the route. This active-list of neighbors will
notifications from the node in the event of detection of a link receive notifications from the node in the event of detection of a
breakage. link breakage. A neighbor is on the active list if it has sent any
packet to the node to be forwarded to the destination within the last
ACTIVE_ROUTE_TIMEOUT milliseconds.
7.2. Generating Route Requests 6.2. Generating Route Requests (RREQs)
A node broadcasts a RREQ when it determines that it needs a route to A node broadcasts a RREQ when it determines that it needs a route to
a destination and does not have one available. This can happen if a destination and does not have one available. This can happen if
the destination is previously unknown to the node, or if a previously the destination is previously unknown to the node, or if a previously
valid route to the destination expires. Routes can become invalid valid route to the destination expires or is broken (i.e., an
if they time out (the Lifetime associated with the route expires), infinite metric is associated with the route). When a route table
or else if a link breakage results in an infinite metric being entry is marked with an infinite metric, its expiration time is also
associated with the route. When a route table entry is marked updated to be the current time plus BAD_LINK_LIFETIME milliseconds.
with an infinite metric, its expiration time is also updated to be After the expiration time, the route MAY be expunged from the node's
the current time plus BAD_LINK_LIFETIME milliseconds. After the route table.
expiration time, the route MAY be expunged from the node's route
table.
After broadcasting a RREQ a node waits for a RREP, and if the After broadcasting a RREQ a node waits for a RREP, and if the reply
reply is not received within RREP_WAIT_TIME seconds, the node may is not received within RREP_WAIT_TIME milliseconds, the node may
rebroadcast the RREQ. The RREQ may be rebroadcast up to a maximum of rebroadcast the RREQ. The RREQ may be rebroadcast up to a maximum of
RREQ_RETRIES times. Each rebroadcast has to increment the Broadcast RREQ_RETRIES times. Each rebroadcast has to increment the Broadcast
ID field. The node MAY choose to use larger TTL values in the IP ID field. The node MAY choose to use larger TTL values in the IP
header field, or wait for longer times for the RREP to arrive. header field, or wait for longer times for the RREP to arrive.
7.3. Forwarding Route Requests 6.3. Forwarding Route Requests
When a node receives a broadcast RREQ, it first checks to see whether When a node receives a broadcast RREQ, it first checks to see
it has received a RREQ with the same Source IP Address and broadcast whether it has received a RREQ with the same Source IP Address and
ID fields within the last BCAST_ID_SAVE milliseconds. If such a RREQ a broadcast ID field of equal unsigned integer value within the
has been received, the node silently discards the newly received last BCAST_ID_SAVE milliseconds. If such a RREQ has been received,
RREQ. Otherwise, the node checks to see whether it has a route to the node silently discards the newly received RREQ. Otherwise, the
the destination. If the node does not have a route, it rebroadcasts node checks to see whether it has a route to the destination. If
the RREQ from its interface(s) with the same field values, but using the node does not have a route, it rebroadcasts the RREQ from its
its own IP address in the IP header of the outgoing RREQ. The TTL or interface(s) but using its own IP address in the IP header of the
hop limit field in the outgoing IP header is decreased by one. The outgoing RREQ. The TTL or hop limit field in the outgoing IP header
Hop Count field in the broadcast RREQ message is incremented by one, is decreased by one. The Hop Count field in the broadcast RREQ
to account to the new hop through the intermediate node. In this message is incremented by one, to account for the new hop through the
case, the node also creates a reverse route to the Source IP Address intermediate node. In this case, the node also creates or updates a
in its routing table with next hop equal to the IP address of the reverse route to the Source IP Address in its routing table with next
neighboring node that sent the broadcast RREQ (often not equal to the hop equal to the IP address of the neighboring node that sent the
Source IP Address field in the RREQ message). This reverse route broadcast RREQ (often not equal to the Source IP Address field in the
might be used for an eventual RREP back to the original node making RREQ message). This reverse route might be used for an eventual RREP
the RREQ (identified by the Source IP Address). The reverse route is back to the node which originated the RREQ (identified by the Source
put into the route table with lifetime REV_ROUTE_LIFE milliseconds. IP Address). If no route exists for the Source IP address, or if an
existing route would expire too soon, the reverse route is put into
the route table with lifetime REV_ROUTE_LIFE milliseconds.
If, on the other hand, the node does have a route for the If, on the other hand, the node does have a route for the
destination, it compares the destination sequence number (dest-seqno) destination, it compares the destination sequence number (dest-seqno)
for that route with the Destination Sequence Number field of the for that route with the Destination Sequence Number field of the
incoming RREQ. If the node's existing dest-seqno is smaller than incoming RREQ. If the node's existing dest-seqno is smaller than
the Destination Sequence Number field of the RREQ, the node again the Destination Sequence Number field of the RREQ, the node again
rebroadcasts the RREQ just as if it did not have a route to the rebroadcasts the RREQ just as if it did not have a route to the
destination at all. destination at all.
If the node has a route to the destination, and the node's existing If the node has a route to the destination, and the node's existing
dest-seqno is greater than or equal to the Destination Sequence dest-seqno is greater than or equal to the Destination Sequence
Number of the RREQ, then the node generates a RREP as discussed Number of the RREQ, then the node generates a RREP as discussed
further in section 7.4. further in section 6.4.
7.4. Generating Route Replies 6.4. Generating Route Replies (RREPs)
If a node receives a route request for a destination, and has a If a node receives a route request for a destination, and has a
fresh enough route to satisfy the request, the node generates a RREP fresh enough route to satisfy the request, the node generates a
message and unicasts it back to the node indicated by the Source RREP message and unicasts it back to the node indicated by the
IP Address field of the received RREQ. First, the node copies over Source IP Address field of the received RREQ. If the node is not the
its destination sequence number from the entry in its route table, destination node, it copies over the destination sequence number from
or if the generating node is the node itself, it uses a destination the route table entry. If the generating node is the destination
sequence number at least equal to a sequence number generated after itself, it uses a destination sequence number at least equal to a
the last detected change in its neighbor set. If the node has not sequence number generated after the last detected change in its
detected any change in its set of neighbors since it last incremented neighbor set and at least equal to the destination sequence number in
its destination sequence number, it may use the same destination the RREQ. If the destination node has not detected any change in its
sequence number. set of neighbors since it last incremented its destination sequence
number, it may use the same destination sequence number.
As part of the process of generating the RREP, the generating node As part of the process of generating the RREP, the generating node
creates or updates an entry in its routing table for the Source creates or updates an entry in its routing table for the Source
IP Address, if necessary as described in section 7.3. The Source IP Address, if necessary as described in section 6.3. The Source
Sequence Number is put into the route entry, along with the Hop Count Sequence Number is put into the route entry, along with the Hop Count
from the RREQ. The expiration time for the route table entry is set from the RREQ. The expiration time for the route table entry is set
to the current time plus ACTIVE_ROUTE_TIMEOUT seconds. to the current time plus ACTIVE_ROUTE_TIMEOUT milliseconds.
If the generating node is not the destination node, then the If the generating node is not the destination node, then the
generating node calculates the Hop Count between the Source IP generating node places its distance in hops from the destination
Address and the Destination IP Address by adding together the Hop in the Hop Count field. If the generating node is the destination
Count from the RREQ and the hop count stored in the route table entry node, it places the value zero in the Hop Count field. The Hop Count
for the destination node. If, on the other hand, the generating node field is incremented by one at each hop as the RREP is forwarded to
is the destination node itself, the Hop Count field in the RREP is the source. When the RREP reaches the source, the Hop Count will
simply equal to the Hop Count received in the RREQ. represent the distance, in hops, of the destination from the source.
If the node is not the destination node, it calculates the Lifetime If the node is not the destination node, it calculates the Lifetime
field of the RREP by subtracting the current time from the expiration field of the RREP by subtracting the current time from the expiration
time in its route table entry. Otherwise, if the generating node is time in its route table entry. Otherwise, if the generating node
also the destination node, it copies the value MY_ROUTE_TIMEOUT into is also the destination node, it copies the value MY_ROUTE_TIMEOUT
the Lifetime field of the RREP. into the Lifetime field of the RREP. Each node MAY make a separate
determination about its value MY_ROUTE_TIMEOUT.
If the generating node is not the node indicated by the Destination If the generating node is not the node indicated by the Destination
IP Address, then it puts the next hop towards the destination in the IP Address, then it puts the next hop towards the destination in the
active-list for the reverse path route entry. active-list for the reverse path route entry.
7.5. Generating Hello Messages 6.5. Maintaining Local Connectivity
Every node generates a "hello" message once every HELLO_INTERVAL Each forwarding node SHOULD keep track of which of its neighbors are
milliseconds. This hello message is a broadcast RREP with TTL = 1, active next hops (i.e., which next hops have been used to forward
and the message fields set as follows: packets towards some destination within the last ACTIVE_ROUTE_TIMEOUT
milliseconds). Each forwarding node SHOULD attempt to determine
which of its active next hop neighbors are actually within its
broadcast range by using the following procedure.
When a forwarding node receives a (unicast or multicast) packet
from one of its active neighbors, and retransmits the packet to
the next hop, the node SHOULD NOT transmit any additional data for
NEXT_HOP_WAIT milliseconds. Instead, the node SHOULD listen to see
if the next hop retransmitted the packet. If the retransmission is
detected, the node can assume that the next hop is still within its
broadcast range, and can then resume transmission. Otherwise, the
node SHOULD attempt to detect a response from the next hop, using the
following methods:
- Any suitable link-layer indication, e.g. a link-layer
acknowledgement, or a CTS to receive the packet, or a RTS the
packet to its own downstream next hop.
- Receiving a ICMP ACK message from the next hop.
- A RREQ unicast to the next hop, asking for a route to the next
hop.
- An ICMP Echo Request message unicast to the next hop.
The ICMP ACK message SHOULD be sent to a forwarding node by a next
hop which is also the destination IP address shown in the IP header
of the packet, when the destination has not sent any packets to the
forwarding node within the last HELLO_INTERVAL milliseconds. If the
next hop cannot be detected by any of these methods, the forwarding
node MUST assume that the link is broken, and take corrective action
by following the methods specified in Section 6.6.
A node MAY detect a link breakage by listening for broadcasts
and ``hello'' messages from its set of neighbors. If it has
received hello messages from a neighbor, but misses more than
ALLOWED_HELLO_LOSS consecutive broadcasts or hello messages from
that neighbor, the node MUST assume that its neighbor is no longer
in the neighborhood. When this happens, the node SHOULD proceed as
in Section 6.6. A node SHOULD assume that a hello message has been
missed if it is not received within 2.1 times the duration of the
HELLO_INTERVAL.
A node MAY offer connectivity information by broadcasting local
``hello'' messages as follows. Every HELLO_INTERVAL milliseconds,
the node checks whether it has sent a broadcast (e.g., a RREQ) within
the last HELLO_INTERVAL. If it has not, it MAY generate a ``hello''
message. This hello message is a broadcast RREP with TTL = 1, and
the message fields set as follows:
Destination IP Address Destination IP Address
the node's IP address, The node's IP address.
Destination Sequence Number Destination Sequence Number
the latest sequence number The node's latest sequence number.
Hop Count 0 Hop Count 0
Lifetime (1 + ALLOWED_HELLO_LOSS) * HELLO_INTERVAL Lifetime (1 + ALLOWED_HELLO_LOSS) * HELLO_INTERVAL
The Hello Messages MAY also contain extensions denoting the In addition to regular Hello messages, each multicast group
multicast groups which are known to the node, along with the groups' leader will also broadcast a Group Hello message system-wide every
corresponding groupheads. These extensions can be used by nodes GROUP_HELLO_INTERVAL milliseconds. This system-wide Group Hello
which have just joined the network to fill in their Request Table message has IP TTL value greater than the diameter of the network
up-to-date request information. The information is also used for and is initialized to a hop count of zero. The hop count value is
route rebuilding, as is described later. incremented by one by each node as the message is forwarded. This
Group Hello message contains the IP Addresses of the Multicast Groups
The extensions have the following format: for which the node is the Group Leader, along with the corresponding
multicast group sequence numbers. Nodes in the multicast tree can
Multicast Group IP Address use these messages to update their current distance from the group
IP address of known multicast group leader. The information in the message is also used for merging
partitioned multicast trees, as is described later. See Section 12.3
Multicast Grouphead IP Address for extensions needed to complete a GROUP_HELLO message.
IP Address of corresponding multicast grouphead
7.6. Initiating Triggered Route Replies 6.6. Initiating Triggered Route Replies (Triggered RREPs)
A node can trigger an unsolicited RREP if either it detects a link A node can trigger an unsolicited RREP if either it detects a link
breakage for a next hop along an active route in its route table, or breakage for a next hop along an active route in its route table, or
if it receives a RREP from a neighbor with an infinite metric for an if it receives a RREP from a neighbor with an infinite metric for an
active route (i.e., containing a Destination IP Address for which active route (i.e., containing a Destination IP Address for which
there is a route table entry with a nonempty active-list) there is a route table entry with a nonempty active-list)
The unsolicited RREP is unicast to each neighbor in the nonempty The unsolicited RREP is broadcast to inform each neighbor in the
active-list for the route to that destination. The contents of the nonempty active-list for the route to that destination. The contents
RREP fields are set as follows: of the RREP fields are set as follows:
L 0 L 0
Hop Count 65,535 Hop Count 255 (= infinity)
Destination IP Address Destination IP Address
The destination in the broken route The destination in the broken route
Destination Sequence Number Destination Sequence Number
One plus the destination sequence number recorded in One plus the destination sequence number recorded for
the route. the route.
7.7. Detecting Link Breakage 7. Multicast Route Activation (MACT) Message Format
A node can detect a link breakage by listening for "hello" messages 0 1 2 3
from its set of neighbors. If it has received hello messages from 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
a particular neighbor, but misses more than ALLOWED_HELLO_LOSS +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
consecutive hello messages from that neighbor, the node can presume | Type |P|G| Reserved |
that the particular neighbor is no longer able to maintain a direct +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
link with the mobile node. When this happens, the node should assume | Multicast Group IP address |
that its link with the former neighbor has been broken, and proceed +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
as in Section 7.6. A node should assume that a hello message has | Source IP address |
been missed if it is not received within 1.5 times the duration of +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
the HELLO_INTERVAL. | Source Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Alternatively, the node can use any physical-layer or link-layer The format of the Multicast Route Activation message is illustrated
methods to detect link breakages with nodes it has considered as above, and contains the following fields:
neighbors.
Type xx
P Prune flag; set when a node wishes to prune itself
from the tree, unset when the node is activating a
tree link.
G Group Leader flag; set by a multicast tree member that
fails to repair a multicast tree link breakage, and
indicates to the group member receiving the message
that it should become the new multicast group leader.
Reserved Sent as 0; ignored on reception.
Multicast Group IP Address
The IP address of the Multicast Group for which a
route is supplied.
Source IP Address
The IP address of the node which originated the Route
Request.
Source Sequence Number
The current sequence number for route information
generated by the source of the route request.
To prune itself from the tree (i.e., inactivate its last link to the
multicast tree), a multicast tree member sends an MACT with the 'P'
flag = 1 to the next hop. A multicast tree member that has more than
one next hop to the multicast tree SHOULD NOT try to prune itself
from the multicast tree.
8. Node Operation - Multicast 8. Node Operation - Multicast
This section describes the scenarios under which nodes generate This section describes the scenarios under which nodes generate
RREQs, RREPs, and MINVs for multicast communication, and how the RREQs, RREPs, and MACTs for multicast communication, and how the
fields in the messages are handled. fields in the messages are handled.
8.1. Maintaining Multicast Tree Utilization Records 8.1. Maintaining Multicast Tree Utilization Records
For each valid multicast group (containing a finite metric) of For each multicast tree to which a node belongs, either because it
which a node is a part, either because it is a member of the group is a member of the group or because it is a router for the multicast
or because it is a router for the multicast tree, the node also tree, the node also maintains a list of next hops -- i.e., those
maintains a list of those neighbors that are likewise a part of the neighbors that are likewise a part of the multicast tree. This
multicast tree. This active-list of neighbors is used for forwarding list of next hops is used for forwarding messages received for
messages received for the multicast group. A node will forward such the multicast group. A node will forward a multicast message to
a message to every neighbor listed as a part of the multicast tree, every such next hop, except that neighbor from which the message
except that neighbor from which the message arrived. arrived. If there are multiple next hops, the forwarding operation
MAY be performed by broadcasting the multicast packet to the node's
neighbors; only the neighbors that belong to the multicast tree will
continue to forward the multicast packet.
8.2. Generating Multicast Route Requests 8.2. Generating Multicast RREQs
A node sends a route request (RREQ) either when it determines that it A node sends a multicast RREQ either when it determines that it
should be a part of a multicast group, and it is not already a member should be a part of a multicast group, and it is not already a member
of that group, or when it has a message to send to the multicast of that group, or when it has a message to send to the multicast
group but does not have a route to that group. If the node wishes to group but does not have a route to that group. If the node wishes
join the multicast group, it sets the flag J in the RREQ; otherwise, to join the multicast group, it sets the `J' flag in the RREQ;
it leaves the flag unset. The destination address of the RREQ is otherwise, it leaves the flag unset. The destination address of
always set to the multicast group address. If the node has a record the RREQ is always set to the multicast group address. If the node
of another node (the multicast grouphead) requesting to be a member knows the group leader and has a route to it, the node will place
of that multicast group, it has two options. If the node has a known the group leader's address in the Multicast Group Leader extension
route to the grouphead, it will place the address of that node in (Section 12.2), and will unicast the RREQ to the corresponding next
the extension field and will unicast the RREQ to the corresponding hop for that destination. Otherwise, if the node does not have a
next hop for that destination. Otherwise, if the node does not have route to the group leader, or if it does not know who the multicast
a route to the grouphead, or if it does not know who the multicast group leader is, it will broadcast the RREQ and will not include the
grouphead is, it will broadcast the RREQ with destination IP address extension field.
set to the IP address of the multicast group, and it will not include
the extension field.
These scenarios can occur during initialization of a node, when a
node discovers it should be a member of a multicast group, or when
a previously valid branch of the multicast tree expires. Branches
of the multicast tree become invalid if they time out (the Lifetime
associated with the route expires), or if a link breakage results in
an infinite metric being associated with the route.
The process of waiting for a RREP to a RREQ with a multicast The process of waiting for a RREP to a RREQ with a multicast
destination address is the same as that described in Section 7.2. destination address is the same as that described in Section 6.2.
The node may resend the RREQ up to RREQ_RETRIES times if a RREP is The node may resend the RREQ up to RREQ_RETRIES times if a RREP
not received. If the original RREQ was unicast to a specific node is not received. If a RREQ was unicast to a group leader and a
and a RREP is not received within RREP_WAIT_TIME seconds, the node RREP is not received within RREP_WAIT_TIME milliseconds, the node
will broadcast the next RREQ (and all subsequent RREQs for that will broadcast subsequent RREQs for that multicast group across
multicast group) across the network. The destination IP address of the network. If a RREP is not received after RREQ_RETRIES total
the rebroadcast is set to the address of the multicast group, and requests, the node may assume that there are no other members of that
the extension field containing the multicast grouphead address is particular group within the connected portion of the network. If it
not included. If a RREP is not received after RREQ_RETRIES total wanted to join the multicast group, it MAY then become the multicast
requests, the node may assume that there are no other members of group leader for that multicast group and initialize the destination
that particular group within the network. If it wanted to join the sequence number of the multicast group. Otherwise, if it only wanted
multicast group, it will then become the multicast grouphead for that to send packets to that group without actually joining the group, it
multicast group and initialize the destination sequence number of will drop the packets it had for that group.
the multicast group. Otherwise, if it only wanted to send packets
to that group without actually joining the group, it will drop the
packets it had for that group.
Each node in the network receiving a RREQ message with the J flag Each node in the network receiving a RREQ message with the `J' flag
set, i.e. every member of the network, checks their Request Table set MAY check its request table to see whether there is already an
to see whether there is already an entry for this multicast group. entry for this multicast group. If there is no entry for the group,
If there is no entry for the group, the node records the IP Address the node records the IP Address of the node which sent the RREQ,
of the node which sent the RREQ, together with the IP address of together with the IP address of the group for which it requested to
the group for which it requested to be a member, in the Request be a member, in the Request Table. Because the first node to request
Table. Because the first node to request to be in a group becomes membership in a group becomes the multicast group leader, entries
the multicast grouphead, entries in the Request Table represent in the Request Table represent multicast group leaders. If the
multicast groupheads. If a node wishes to join or send a message to multicast group leader changes at any time, the nodes will note this
a multicast group in the future, it will first consult its Request change by updating their Request Table so that the node IP address
Table to see if another node had previously requested to join that matches that of the new group leader. If the node wishes to join or
group. Based on the existence or nonexistence of an entry for the send a message to a multicast group, it first consults its Request
multicast group in the Request Table, the node will then send the Table. Based on the existence of an entry for the multicast group
RREQ as described at the beginning of the section. in this table, the node will then send the RREQ as described at the
beginning of this section.
8.3. Forwarding Multicast Route Requests 8.3. Forwarding Multicast Route Requests
The operation of nodes forwarding RREQs for multicast is similar The operation of nodes forwarding RREQs for multicast is similar
to that for the reception and forwarding of RREQs as described in to that for the reception and forwarding of RREQs as described in
Section 7.3, with the following exceptions. If the RREQ is a join Section 6.3, with one exception. If the RREQ is a join request, when
request, when the node creates a reverse route to the Source IP the node creates a reverse route to the Source IP Address, it places
Address, it places a route pointer in its multicast routing table, in the information in its Multicast Route table. The generation of the
addition to its (unicast) routing table. Further, a node can only route reply (RREP) message is discussed in the following section.
respond to a join RREQ if it is a member of the multicast tree. The
generation of the route reply (RREP) message is discussed in the
following section.
8.4. Generating Multicast Route Replies 8.4. Generating Multicast Route Replies
If a node receives a multicast join route request for a multicast If a node receives a multicast join RREQ for a multicast group, and
group, and it is already a member of the multicast tree for that it is already a member of the multicast tree for that group, the
group, the node updates its route and multicast route tables and node updates its Multicast Route Table and then generates a RREP
then generates a RREP message. It unicasts the RREP back to the message. It unicasts the RREP back to the node indicated by the
node indicated by the Source IP Address field of the received Source IP Address field of the received RREQ. The RREP contains
RREQ. The RREP contains the current destination sequence number for the current sequence number for the multicast group, the distance
the multicast group, as well as the IP address of the multicast of the responding node from the nearest multicast group member,
grouphead. and the IP address of the group leader. Further information about
the multicast group leader is entered into the Multicast Group
If a node receives a multicast join route request for a multicast Information extension (see Section 12.3).
group and it is not already a member of the multicast tree for that
group, it will rebroadcast the RREQ to its neighbors.
If a node receives a multicast route request that is not a join A node can only respond to a join RREQ if it is a member of the
message, it can reply if it has a route to the multicast tree. multicast tree. If a node receives a multicast route request that is
Otherwise it will continue forwarding the message. not a join message, it can reply if it has a route to the multicast
tree. Otherwise it will continue forwarding the message. If a node
receives a multicast join route request for a multicast group and it
is not already a member of the multicast tree for that group, it will
rebroadcast the RREQ to its neighbors.
In the event that a node receives a unicasted multicast route request In the event that a node receives a unicasted multicast route request
that specifies its own IP address as the destination address (i.e. that specifies its own IP address as the destination address (i.e.,
the source node believes this destination node to be the multicast the source node believes this destination node to be the multicast
grouphead), but the node is in fact not the grouphead, it can simply group leader), but the node is in fact not the group leader, it
ignore the RREQ. The source node will time out after RREP_WAIT_TIME can simply ignore the RREQ. The source node will time out after
seconds and will broadcast a new RREQ without the grouphead address RREP_WAIT_TIME milliseconds and will broadcast a new RREQ without the
specified. group leader address specified.
Every time the Multicast Grouphead sends an RREP in response to a
RREQ, it increments the multicast group sequence number by one and
attaches the new value of the sequence number to the RREP.
Regardless of whether the multicast grouphead or an intermediate node Regardless of whether the multicast group leader or an intermediate
generates the RREP, the RREP fields are set as follows: node generates the RREP, the RREP fields are set as follows:
Hop Count The distance in hops the node initiating the RREP Hop Count Distance of the responding node to the nearest
is from the multicast grouphead. This field is multicast group member.
incremented by each node that forwards the RREP along
the route to the source.
Destination IP Address Destination IP Address
The IP address of the destination for which a route The IP address of the node which supplies a route to
is supplied, in this case the multicast grouphead. the multicast group.
Destination Sequence Number Destination Sequence Number
The destination sequence number associated with the The destination sequence number of the node which
route to the grouphead. supplies a route to the multicast group.
Lifetime The time for which nodes receiving the RREP consider Lifetime The time for which nodes receiving the RREP consider
the route to be valid. the route to be valid.
Multicast Group IP Address The Multicast Group Information extension described in Section 12.3
The IP Address of the Multicast Group. is also included.
Multicast Grouphead IP Address 8.5. Forwarding Route Replies
The IP Address of the Multicast Grouphead.
Multicast Group Sequence Number If an intermediate node receives a RREP in response to a RREQ that it
The current sequence number of the Multicast Group. has transmitted (or retransmitted on behalf of some other node), it
increments the Hop Count and forward the RREP along the path to the
source of the RREQ.
8.5. Route Deletion and Multicast Tree Pruning When the node receives more than one RREP for the same RREQ, it
operates in a manner similar to the source node by saving the route
information with the greatest sequence number, and beyond that the
lowest hop count; it discards all other RREPs. This node forwards
the first RREP towards the source of the RREQ, and then forwards
later RREPs only if they have a greater sequence number or smaller
metric.
When a node broadcasts an RREQ message, it is likely to receive more 8.6. Route Deletion and Multicast Tree Pruning
When a node broadcasts a RREQ message, it is likely to receive more
than one reply since any node in the multicast tree can respond. than one reply since any node in the multicast tree can respond.
If the RREQ was a join request, the RREP message traveling back If the RREQ was a join request, the RREP message traveling back to
to the node which originated the request sets up route pointers, the node which originated the request sets up route pointers, which
effectively grafting a branch onto the multicast tree. If multiple may eventually graft a branch onto the multicast tree. If multiple
branches to the same destination are created in such a manner, a branches to the same destination are created in such a manner, a
loop will be formed. Hence, in order to prevent the formation of loop will be formed. Hence, in order to prevent the formation of
any such loops, it is necessary to delete all but one of the routes any such loops, it is necessary to activate only one of the routes
created by the RREP messages. The RREP containing the largest created by the RREP messages. The RREP containing the largest
destination sequence number is chosen to be the added branch to the destination sequence number is chosen to be the added branch to the
multicast tree. In the event that a node receives more than one multicast tree. In the event that a node receives more than one
RREP with the same (largest) sequence number, it selects the first RREP with the same (largest) sequence number, it selects the first
one with the smallest hop count, i.e. the shortest distance to the one with the smallest hop count, i.e., the shortest distance to a
multicast grouphead. After waiting for RREP_WAIT_TIME seconds, member of the multicast group. After waiting for RREP_WAIT_TIME
the node must then deactivate all routes created by other RREPs. milliseconds, the node must choose the route it wishes to use as
This is accomplished by broadcasting a multicast-invalidate (MINV) its link to the multicast tree. This is accomplished by sending a
message. The Destination IP Address of the MINV packet is set to the Multicast Activation (MACT) message. The Destination IP Address of
IP address of the multicast group, and the IP address of the next hop the MACT packet is set to the IP address of the multicast group. The
along the branch which was added to the multicast tree is included node will unicast this message to the selected next hop, effectively
in an extension field. The Hop Count field of the MINV is set to 1. activating the route. After receiving this message, the node's
All nodes receiving this message whose address does not match that neighbor to which the MACT was sent activates the route entry for the
listed in the extension field of the packet will delete the multicast link in the multicast route table, thereby finalizing the creation of
tree pointer to the node from which the packet came. The node which the tree branch. All neighbors not receiving this message will time
was chosen as the next hop sets the 'active' flag for the sending out and delete that node as a next hop for the multicast group in
node to true, thereby finalizing the creation of the tree branch. their route tables, having never activated the route entry for that
next hop.
Various scenarios exist for the nodes receiving the MINV message.
If the node receiving this message is a member of the multicast
group, it will not forward the MINV any further. If it is not a
member of the multicast group and no other nodes use it as a router
for the multicast group, it will propagate the MINV further up the
tree, effectively removing (pruning) itself from the multicast tree.
The Destination IP Address of the propagated MINV message is set
to the IP address of the multicast group, and the extension field
indicating the next hop is not included. The lack of the next hop
extension field indicates to all nodes receiving the packet that
their multicast tree route pointer to this source node (if such a
route pointer exists) should be deleted. If the next hop selected
by the source node's MINV message was not previously a multicast
tree member, it will have propagated the original RREQ further up
the network in search of nodes which are tree members. Thus it is
possible that this node also received more than one RREP. When the
node receives more than one RREP for the same RREQ, it operates in
a manner similar to the source node by saving the route information
with the greatest sequence number, and beyond that the lowest hop
count; it discards all other RREPs. This node forwards the first
RREP towards the source of the RREQ, and then forwards later RREPs
only if they have a greater sequence number or smaller metric. When
the node receives an MINV announcing it as the next hop, it will
send its own MINV announcing the node it has chosen as its next hop,
and so on up the tree, until a node which was already a part of the
multicast tree is reached. If a node receives an MINV and discovers
it was not chosen as the next hop and is not otherwise a part of the
multicast tree, it will delete the tree pointers and send an MINV
without the next hop extension field to prune itself from the tree.
When a source node sends an MINV selecting a next hop, it sets the Two scenarios exist for a neighboring node receiving the MACT
'active' flag for this next hop to true. If the next hop also needs message. If this node was previously a member of the multicast
to send an MINV message specifying which node it has chosen as its tree, it will not propagate the MACT message any further. However,
next hop, it lists the IP address of this next hop in the next hop if the next hop selected by the source node's MACT message was not
extension of the MINV. Upon receiving this MINV message, the source previously a multicast tree member, it will have propagated the
node will not delete the tree pointer to this node (even though its original RREQ further up the network in search of nodes which are
IP address is not listed in the next hop extension) because the tree members. Thus it is possible that this node also received more
'active' flag has already been set. than one RREP, as noted in section 8.5.
To prevent the possibility of multicast group data messages being When the node receives an MACT announcing it as the next hop, it will
delivered to the source node from multiple neighboring nodes before send its own MACT announcing the node it has chosen as its next hop,
the MINV messages is broadcast, no node is allowed to forward a data and so on up the tree, until a node which was already a part of the
packet to this source node before the reception of the MINV message. multicast tree is reached.
The nodes know they have not yet received the MINV message because
the 'active' flag for that tree branch remains unset. Only after
receiving the MINV and setting the 'active' flag can the node to
which the MINV is addressed forward any multicast group data packets
to the node.
If a multicast group member revokes its member status and wishes to If a multicast group member revokes its member status and wishes to
remove itself from the multicast tree, it can do so if it is not a remove itself from the multicast tree, it can do so if it is not a
multicast router for any other nodes in the multicast group. If this multicast router for any other nodes in the multicast group (i.e.,
is the case, it may broadcast an MINV message without the next hop if it is a leaf node). If this is the case, it may unicast to its
extension and with the Destination IP Address set to the IP address next hop on the tree an MACT message with the 'P' flag set and with
of the multicast group to prune itself from the tree. Similarly, the Destination IP Address set to the IP address of the multicast
if the node receiving this message is not a member of the multicast group in order to prune itself from the tree. Similarly, if the node
group and does not have any other nodes routing through it, it may receiving this message is not a member of the multicast group and
send its own MINV message up the tree. does not have any other nodes routing through it, it may send its own
MACT message up the tree.
8.6. Repairing Link Breakages 8.7. Repairing Link Breakages
When a link breakage is detected between two nodes on the multicast Branches of the multicast tree become invalid if they time out
tree, the node upstream of the break (i.e. the node which is further (the Lifetime associated with the route expires), or if a link
from the multicast grouphead) is responsible for initiating the breakage results in an infinite metric being associated with the
repair of the broken link. In order to build the route back up, this route. When a link breakage is detected between two nodes on the
node will broadcast a RREQ with destination IP address set to the IP multicast tree, the node downstream of the break (i.e., the node
address of the grouphead and with the J flag set. The destination which is further from the multicast group leader) is responsible
sequence number of the RREQ is the last known sequence number of the for initiating the repair of the broken link. In order to build
multicast group. The Multicast Group Hop Count field is set to the the route back up, this node will broadcast a RREQ with destination
distance of the source node from the multicast grouphead. Only a IP address set to the IP address of the group leader and with the
node which has a hop count for the multicast group smaller than the `J' flag set. The destination sequence number of the RREQ is the
indicated value can respond. This hop count requirement is included last known sequence number of the multicast group. The Multicast
to prevent nodes on the same side of the break as the node initiating Group Hop Count field is set to the distance of the source node from
the repair from replying to the RREQ. The RREQ is broadcast using an the multicast group leader. Only a node which has a hop count for
expanding rings search. Because of the high probability that other the multicast group less than or equal to the indicated value can
nearby nodes can be used to rebuild the route to the grouphead, the respond. This hop count requirement is included to prevent nodes
on the same side of the break as the node initiating the repair
from replying to the RREQ. The RREQ is broadcast using an expanding
rings search. Because of the high probability that other nearby
nodes can be used to rebuild the route to the group leader, the
original RREQ is broadcast with a TTL (time to live) field value original RREQ is broadcast with a TTL (time to live) field value
equal to the Multicast Group Hop Count. In this way, the effects of equal to the Multicast Group Hop Count. In this way, the effects of
the link breakage may be localized. If no reply is received within the link breakage may be localized. If no reply is received within
RREP_WAIT_TIME seconds, the RREQ will be rebroadcast with a larger RREP_WAIT_TIME milliseconds, all subsequent RREQs (up to RREQ_RETRIES
TTL value, and so on until the message is broadcast across the entire total attempts) will be broadcast across the entire network. Any
network or until the route is rebuilt. Any node that is a part of node that is a part of the multicast tree and that has a multicast
the multicast tree and which had a multicast group hop count smaller group hop count smaller than that contained in the RREQ can return
than that contained in the RREQ can return an RREP. If there is more a RREP. If there is more than one RREP received at the originating
than one RREP received at the originating node, route deletions occur node, route deletions occur as described in the previous section.
as described in the previous section.
If no response is received after RREQ_RETRIES broadcasts, it can be If no response is received after RREQ_RETRIES broadcasts, it can be
assumed that the network has become partitioned and the multicast assumed that the network has become partitioned and the multicast
tree cannot be repaired at this time. In this situation, the tree cannot be repaired at this time. In this situation, if the
node which had initiated the route rebuilding becomes the new node which had initiated the route rebuilding was a multicast group
multicast grouphead for its part of the multicast tree partition. member, it will become the new multicast group leader for its part of
It broadcasts a RREP with an infinity metric and with the multicast the multicast tree partition. It broadcasts a Group Hello with the
group address extension field containing the corresponding multicast multicast group address extension field containing the corresponding
group IP address included. All nodes receiving this RREP update multicast group IP address included. The `U' flag in the Group Hello
their Request Tables to indicate the new grouphead information. is set, indicating that there has been a change in the group leader
Nodes which are a part of the multicast group also update the information. All nodes receiving this message update their Request
grouphead information for that group in their Multicast Route Table Tables to indicate the new group leader information. Nodes which are
to indicate the new grouphead. All nodes will change the information a part of the multicast tree also update the group leader information
in their hello messages to reflect this update. for that group in their Multicast Route Table to indicate the new
group leader. On the other hand, if the node which had initiated the
repair is not a multicast group member, there are two possibilities.
If it only has one next hop for the multicast tree, it will unicast
a MACT message, with the 'P' flag set, to its next hop, thereby
indicating that it is pruning itself from the tree. The node
receiving this message will note that it is coming from its upstream
link, i.e., from a node that is closer to the group leader than it
is. If the node receiving this message is a multicast group member,
it will become the new group leader and will broadcast a Group
Hello message as indicated above. If it is not a multicast group
member and it only has one other next hop link, it will similarly
prune itself from the tree and this process will continue until a
multicast group member is reached. On the other hand, if the node
which initiated the rebuilding is not a group member and it has more
than one next hop for the tree, it cannot prune itself, since doing
so would partition the tree. It instead chooses one of its next hops
and sends an MACT with the 'G' flag set. This flag indicates that
the next group member to receive this message should become the new
group leader. If the node's next hop is a group member, this node
will become the group leader. Otherwise, the node will unicast its
own MACT message with the 'G' flag set to one of its next hops, and
so on until a group member is reached.
In the event that the link break could not be repaired, the multicast In the event that the link break can not be repaired, the multicast
tree will remain partitioned until the two parts of the network tree will remain partitioned until the two parts of the network
become connected once again. A node from one partition of the become connected once again. A node from one partition of the
network will know that it has come into contact with a node from network will know that it has come into contact with a node from the
the other side of the network by noting the difference in the hello other partition of the network by noting the difference in the Group
message multicast group information. The node who is a part of the Hello message multicast group leader information. A node which is a
network partition with the lower grouphead IP address will initiate part of the network partition with the lower group leader IP address
the tree repair. It will unicast a RREQ message with the R flag set and which is also a member of the multicast tree can initiate the
back to the multicast grouphead of its partition in order to get tree repair. It will unicast a RREQ message with the `R' flag set
back to the multicast group leader of its partition in order to get
permission to rebuild the tree. The node must seek permission to permission to rebuild the tree. The node must seek permission to
rebuild the tree in order to prevent multiple nodes from attempting rebuild the tree in order to prevent multiple nodes from attempting
to rebuild the tree if contact between the two partitions is to rebuild the tree if contact between the two partitions is
re-established in more than one place. Multiple repairs would create re-established in more than one place. Multiple repairs would create
loops within the multicast tree. Additionally, since the node loops within the multicast tree. The group leader is the only node
initiating the repair is not necessarily a multicast tree member, it which can respond to a RREQ with the `R' flag set. It will respond
may itself have become disconnected from the multicast grouphead on to the request by sending a RREP granting permission to one and only
its side of the partition, and so the lack of reply will prevent it
from attempting to repair the tree. The grouphead is the only node
which can respond to an RREQ with the R flag set. It will respond to
the request by sending an RREP granting permission to one and only
one node to rebuild the tree. Any nodes which requested permission one node to rebuild the tree. Any nodes which requested permission
and which do not receive an RREP will time out and not attempt the and which do not receive a RREP will time out and not attempt the
repair. As the RREP travels back to the node, it will establish a repair. As the RREP travels back to the node, it will establish a
multicast tree branch if one did not already exist. After receiving multicast tree branch if one did not already exist. After receiving
the RREP, the node which sent the repair request will unicast a RREQ the RREP, the node which sent the repair request will unicast a RREQ
to the grouphead of the other network partition, using the node it to the group leader of the other network partition, using the node
had received the hello message from as the next hop. This RREQ will it had received the Group Hello message from as the next hop. This
contain the current value of the partitions multicast group sequence RREQ will contain the current value of the partitions multicast group
number. Upon receiving the RREQ, the multicast grouphead will take sequence number. Upon receiving the RREQ, the multicast group leader
the larger of its and the received multicast group sequence number, will take the larger of its and the received multicast group sequence
increment this value by one, and respond with a RREP. As the RREP number, increment this value by one, and respond with a RREP. This
is propagated back to the source node, a branch on to the multicast is the group leader which will become the leader of the reconnected
tree is added. When the initiating node receives the RREP, it will multicast tree. As the RREP is propagated back to the source node, a
broadcast across the network an RREP with an infinity metric and the branch on to the multicast tree is added. When the initiating node
multicast group address extension field containing the corresponding receives the RREP, the tree will be reconnected. The next time the
multicast group IP address, and with the multicast grouphead IP group leader broadcasts a Group Hello, it will set the `U' flag to
address and multicast group sequence number fields set to show the indicate that there is a change in the group leader information and
updated information. All nodes receiving this RREP (i.e. the entire group members should update the corresponding information. The node
connected portion of the network), will have the updated multicast which was the group leader of the other partition will also note this
group information for that group. The node which was the grouphead message and update its tables to indicate that the other group leader
of the other partition will also note this message and update its is now the multicast group leader for the entire network.
tables to indicate that the other grouphead is now the multicast
grouphead for the entire network.
8.7. Initiating Triggered Route Replies 8.8. Initiating Triggered Route Replies
A node can trigger an unsolicited RREP if it has an entry in its A node can trigger an unsolicited RREP if it sends a RREQ to join
Request Table for a multicast group, sends a RREQ to join the a multicast group and after RREQ_RETRIES times does not receives
multicast group, and after RREQ_RETRIES times does not receives a a response. The node will then become the new multicast group
response. The node will then become the new multicast grouphead, and leader, and it will broadcast a RREP with infinity TTL (a Group
it will broadcast a RREP with infinity metric and with the multicast Hello message) and with the multicast group IP Address / Sequence
group / grouphead extension information set to reflect that it is number extension information set to reflect that it is now the group
now the grouphead for the multicast group. In addition, in order to leader for the multicast group. In addition, in order to ensure
ensure nodes maintain consistent and up-to-date information about nodes maintain consistent and up-to-date information about who the
who the multicast groupheads are, any node which is a grouphead for multicast group leaders are, any node which is a group leader for a
a multicast group will broadcast an unsolicited RREP containing its multicast group will broadcast such a Group Hello across the network
IP Address and the multicast group IP address for which it is the every GROUP_HELLO_INTERVAL milliseconds. The contents of the RREP
grouphead across the network every RREP_UPDATE seconds. The contents fields (including the Multicast Group Information Extension) are set
of the RREP fields are set as follows: as follows:
L 0 L 0
Hop Count 65,535 Hop Count 0
Destination IP Address Destination IP Address
The IP Address of the node sending the RREP. The IP Address of the node sending the Group Hello.
Destination Sequence Number Destination Sequence Number
One plus the destination sequence number recorded in The node's latest destination sequence number.
the route.
Multicast Group IP Address Multicast Group IP Address
The IP Address of the Multicast Group of which the The IP Address of the Multicast Group for which the
node just became the grouphead. node is the group leader.
Multicast Grouphead IP Address
The IP Address of the new Multicast Grouphead, i.e.
the node sending the RREP.
Multicast Group Sequence Number Multicast Group Sequence Number
The Sequence Number of the multicast group, as set by One plus the last known sequence number of the
the new multicast grouphead. multicast group.
9. Configuration Parameters
This section gives default values for some important values
associated with AODV protocol operations.
ACTIVE_ROUTE_TIMEOUT 3000
ALLOWED_HELLO_LOSS 2
BAD_LINK_LIFETIME 2 * RREP_WAIT_TIME
BCAST_ID_SAVE 3000 Nodes receiving the Group Hello incrememt the Hop Count field by one
before forwarding the message.
HELLO_INTERVAL 1000 9. Quality of Service
NET_DIAMETER 35 AODV currently provides some minimal controls to enable mobile nodes
in an ad hoc network to specify, as part of a RREQ, certain Quality
of Service parameters that a route to a destination must satisfy.
In particular, a RREQ MAY include a Maximum Delay extension (see
Section 12.4) or a Minimum Bandwidth extension (see Section 12.5).
NODE_TRAVERSAL_TIME 40 If, after establishment of such a route, any node along the path
detects that the requested Quality of Service parameters can no
longer be maintained, that node MUST originate a ICMP QOS_LOST
message back to the node which had originally requested the now
unavailable parameters.
MY_ROUTE_TIMEOUT 6000 10. AODV and Aggregated Networks
REV_ROUTE_LIFE RREP_WAIT_TIME AODV has been designed for use by mobile nodes with IP addresses
that are not necessarily related to each other, to create an ad hoc
network. However, in some cases a collection of mobile nodes MAY
operate in a fixed relationship to each other and share a common
subnet prefix, moving together within an area where an ad hoc network
has formed. Call such a collection of nodes a ``subnet''. In this
case, it is possible for a single node within the subnet to advertise
reachability for all other nodes on the subnet, by responding with
a RREP message to any RREQ message requesting a route to any node
with the subnet routing prefix. Call the single node the ``subnet
router''. In order for a subnet router to operate the AODV protocol
for the whole subnet, it has to maintain a destination sequence
number for the entire subnet. In any such RREP message sent by the
subnet router, the Prefix Length field of the RREP message MUST be
set to the length of the subnet prefix. Other nodes sharing the
subnet prefix SHOULD NOT issue RREP messages.
RREP_UPDATE 5000 11. Using AODV with Other Networks
RREP_WAIT_TIME 3 * NODE_TRAVERSAL_TIME * NET_DIAMETER / 2 In some configurations, an ad hoc network may be able to provide
connectivity between external routing domains that do not use
AODV. If the points of contact to the other networks can act as
subnet routers (see section 10) for any relevant networks within
the external routing domains, then the ad hoc network can maintain
connectivity to the external routing domains. Indeed, the external
routing networks can use the ad hoc network defined by AODV as a
transit network.
RREQ_RETRIES 3 In order to provide this feature, a point of contact to an external
network (call it an Infrastructure Router) has to act as a ``subnet
router'' for every subnet of interest within the external network
for which the Infrastructure Router can provide reachability. This
includes the need for maintaining a destination sequence number for
that external subnet.
Note that the network may contain more than NET_DIAMETER ** 2 nodes. If multiple Infrastructure Routers offer reachability to the same
NET_DIAMETER measures the number of "cells" (typically wireless) that external subnet, those Infrastructure Routers have to cooperate (by
would have to be placed end to end in order to cover the area of the means outside the scope of this specification) to provide consistent
network. AODV semantics for ad hoc access to those subnets.
10. Extensions 12. Extensions
RREQ, RREP, and MINV messages may have further extensions defined RREQ, RREP, and MACT messages have extensions defined in this version
in future versions of the protocol. These extensions will have the (and, possibly, future versions) of the protocol. Extensions have
following format: the following format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | type-specific data ... | Type | Length | type-specific data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type xx Type xx
Length The length of the type-specific data, not including the Length The length of the type-specific data, not including the
Type and Length fields of the extension. Type and Length fields of the extension.
Extensions with types between 128 and 255 may NOT be skipped. The Extensions with types between 128 and 255 may NOT be skipped. The
rules for extensions will be spelled out more fully, and conform with rules for extensions will be spelled out more fully, and conform with
the rules for handling IPv6 options. the rules for handling IPv6 options.
11. Security Considerations 12.1. Hello Interval Extension Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Hello Interval ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Hello Interval, continued |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx
Length The length of the extension field.
Hello Interval
The number of milliseconds between successive
transmissions of a ``hello'' message (RREP).
The Hello Interval extension MAY be appended to a RREP message with
TTL == 1, to be used by a neighboring receiver in determine how long
to wait for subsequent such RREP messages.
12.2. Multicast Group Leader Extension Format
This extension is appended to a RREQ by a node wishing to repair a
multicast tree.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Multicast Group Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multicast Group Leader IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx
Length The length of the extension.
Multicast Group Hop Count
The distance in hops of the node sending the RREQ from
the Multicast Group Leader.
Multicast Group Leader IP Address
The IP Address of the Multicast Group Leader.
This extension is only used for rebuilding a multicast tree branch.
In that case, a route to the Multicast Group Leader was known before
the need for the repair was discovered, and the IP address of the
group leader is placed in the extension field.
12.3. Multicast Group Information Extension Format
The following extension is used to carry additional information for
the RREP message (see Section 5) when sent to establish a route to a
multicast destination.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Multicast Group IP Address ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Multicast Group IP Address | Multicast Group Seq Number ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Multicast Group Seq Number | Multicast Group Ldr IP Addr ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.. Multicast Group Ldr IP Addr |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx
Length The length of the extension field.
Multicast Group IP Address
The IP Address of the Multicast Group.
Multicast Group Seq Number
The current sequence number of the Multicast Group.
Multicast Group Ldr IP Addr
The IP Address of the current Multicast Group Leader.
This extension is included when responding to a multicast group
RREQ. It is also used by a multicast group leader when sending a
Group Hello. The extension fields indicate which group the node
is the group leader of and the current sequence number for that
group. For a Group Hello the Multicast Group Ldr IP Address field
is not included, since this information is already indicated by the
Destination IP Address field of the message.
12.4. Maximum Delay Extension Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Max Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx
Length The length of the extension field.
Max Delay The number of seconds allowed for a transmission from
the source to the destination.
The Maximum Delay Extension can be appended to a RREQ by a requesting
node in order to place a maximum bound on the acceptable time
delay experienced on any acceptable path from the source to the
destination.
Before forwarding the RREQ, an intermediate node MUST compare its
NODE_TRAVERSAL_TIME to the (remaining) Max Delay indicated in the
Maximum Delay Extension. If the Max Delay is less, the node MUST
discard the RREQ and not process it any further. Otherwise, the
node subtracts NODE_TRAVERSAL_TIME from the Max Delay value in
the extension and continues processing the RREQ as specified in
Section 6.3.
12.5. Minimum Bandwidth Extension Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Minimum Bandwidth ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Minimum Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx
Length The length of the extension field.
Minimum Bandwidth
The amount of bandwidth (in kilobits/sec) needed
for acceptable transmission from the source to the
destination.
The Minimum Bandwidth Extension can be appended to a RREQ by a
requesting node in order to specify the minimal amount of bandwidth
that must be made available along acceptable path from the source to
the destination.
Before forwarding the RREQ, an intermediate node MUST compare its
available link capacity to the Minimum Bandwidth indicated in the
extension. If the requested amount of bandwidth is not available,
the node MUST discard the RREQ and not process it any further.
Otherwise, the node continues processing the RREQ as specified in
Section 6.3.
13. Configuration Parameters
This section gives default values for some important values
associated with AODV protocol operations. A particular
mobile node may wish to change certain of the parameters, in
particular the NET_DIAMETER, MY_ROUTE_TIMEOUT, MY_TRAVERSAL_TIME,
ALLOWED_HELLO_LOSS, RREQ_RETRIES, and possibly the HELLO_INTERVAL. In
the latter case, the node should advertise the HELLO_INTERVAL in its
``hello'' messages, by appending a Hello Interval Extension to the
RREP message.
ACTIVE_ROUTE_TIMEOUT 3000
ALLOWED_HELLO_LOSS 2
BAD_LINK_LIFETIME 2 * RREP_WAIT_TIME
BCAST_ID_SAVE 30000
GROUP_HELLO_INTERVAL 5000
HELLO_INTERVAL 1000
MTREE_BUILD 2 * REV_ROUTE_LIFE
NET_DIAMETER 35
NEXT_HOP_WAIT NODE_TRAVERSAL_TIME + 10
NODE_TRAVERSAL_TIME 40
MY_TRAVERSAL_TIME NODE_TRAVERSAL_TIME
MY_ROUTE_TIMEOUT 6000
REV_ROUTE_LIFE RREP_WAIT_TIME
RREP_WAIT_TIME 3 * NODE_TRAVERSAL_TIME * NET_DIAMETER / 2
RREQ_RETRIES 2
Note that the network may contain more than NET_DIAMETER ** 2 nodes.
NET_DIAMETER measures the number of ``cells'' (typically wireless)
that would have to be placed end to end in order to stretch across
the network at its widest point.
14. Security Considerations
Currently, AODV does not specify any special security measures. Currently, AODV does not specify any special security measures.
Route protocols, however, are prime targets for impersonation Route protocols, however, are prime targets for impersonation
attacks, and must be protected by use of authentication techniques attacks, and must be protected by use of authentication techniques
involving generation of unforgeable and cryptographically strong involving generation of unforgeable and cryptographically strong
message digests or digital signatures. It is expected that, in message digests or digital signatures. It is expected that, in
environments where security is an issue, that IPSec authentication environments where security is an issue, that IPSec authentication
headers will be deployed along with the necessary key management to headers will be deployed along with the necessary key management to
distribute keys to the members of the ad hoc network using AODV. distribute keys to the members of the ad hoc network using AODV.
skipping to change at page 25, line 19 skipping to change at page 27, line 19
[2] Charles E. Perkins. Terminology for Ad-Hoc Networking. [2] Charles E. Perkins. Terminology for Ad-Hoc Networking.
draft-ietf-manet-terms-00.txt, November 1997. (work in draft-ietf-manet-terms-00.txt, November 1997. (work in
progress). progress).
Author's Address Author's Address
Questions about this memo can be directed to: Questions about this memo can be directed to:
Charles E. Perkins Charles E. Perkins
Sun Microsystems Networking and Security Center
Sun Microsystems Laboratories
901 San Antonio Rd. 901 San Antonio Rd.
Palo Alto, CA 94303 Palo Alto, CA 94303
USA USA
1 650 786 6464 +1 650 786 6464
1 650 786 6445 (fax) +1 650 786 6445 (fax)
cperkins@eng.sun.com cperkins@eng.sun.com
Elizabeth M. Royer Elizabeth M. Royer
Dept of Electrical and Computer Engineering Dept. of Electrical and Computer Engineering
University of California, Santa Barbara University of California, Santa Barbara
Santa Barbara, CA 93106 Santa Barbara, CA 93106
1 805 893 7788 +1 805 893 7788
1 805 893 3262 (fax) +1 805 893 3262 (fax)
eroyer@alpha.ece.ucsb.edu eroyer@alpha.ece.ucsb.edu
 End of changes. 

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