draft-ietf-manet-aodv-02.txt   draft-ietf-manet-aodv-03.txt 
Mobile Ad Hoc Networking Working Group Charles E. Perkins Mobile Ad Hoc Networking Working Group Charles E. Perkins
INTERNET DRAFT Sun Microsystems Laboratories INTERNET DRAFT Sun Microsystems Laboratories
20 November 1998 Elizabeth M. Royer 25 June 1999 Elizabeth M. Royer
University of California, Santa Barbara University of California, Santa Barbara
Samir R. Das
University of Texas, San Antonio
Ad Hoc On Demand Distance Vector (AODV) Routing Ad Hoc On-Demand Distance Vector (AODV) Routing
draft-ietf-manet-aodv-02.txt draft-ietf-manet-aodv-03.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
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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. It offers
by frequent changes in link connectivity to each other caused quick adaptation to dynamic link conditions, low processing and
by relative movement. It offers quick adaptation to dynamic memory overhead, low network utilization, and establishment of both
link conditions, low processing and memory overhead, low network unicast and multicast routes between sources and destinations. It
utilization, and establishment of both unicast and multicast routes uses destination sequence numbers to ensure loop freedom at all times
between sources and destinations which are loop free at all times. (even in the face of anomalous delivery of routing control messages),
It makes use of destination sequence numbers, which are a novel means solving problems (such as ``counting to infinity'') associated with
of ensuring loop freedom even in the face of anomalous delivery of classical distance vector protocols.
routing control messages, and solving classical problems associated
with distance vector protocols, including the problem of ``counting
to infinity''.
Contents Contents
Status of This Memo i Status of This Memo i
Abstract i Abstract i
1. Introduction 1 1. Introduction 1
2. Overview 1 2. Overview 2
3. AODV Terminology 3 3. AODV Terminology 4
4. Route Request (RREQ) Message Format 5 4. Route Request (RREQ) Message Format 6
5. Route Reply (RREP) Message Format 6 5. Route Reply (RREP) Message Format 7
6. Node Operation - Unicast 7 6. Node Operation - Unicast 8
6.1. Maintaining Route Utilization Records . . . . . . . . . . 7 6.1. Maintaining Route Utilization Records . . . . . . . . . . 8
6.2. Generating Route Requests (RREQs) . . . . . . . . . . . . 8 6.2. Maintaining Associations between Services and IP Addresses 9
6.3. Forwarding Route Requests . . . . . . . . . . . . . . . . 8 6.3. Generating Route Requests (RREQs) . . . . . . . . . . . . 9
6.4. Generating Route Replies (RREPs) . . . . . . . . . . . . 9 6.3.1. Controlling RREQ broadcasts . . . . . . . . . . . 10
6.5. Maintaining Local Connectivity . . . . . . . . . . . . . 10 6.4. Forwarding RREQs . . . . . . . . . . . . . . . . . . . . 10
6.6. Initiating Triggered Route Replies (Triggered RREPs) . . 11 6.4.1. Handling Route Requests (RREQs) for IP
Destinations . . . . . . . . . . . . . . . 11
6.4.2. Handling Route Requests (RREQs) for Services . . 11
6.5. Generating Route Replies (RREPs) for IP Destinations . . 12
6.6. Generating Route Replies (RREPs) for Services . . . . . . 12
6.7. Hello Messages . . . . . . . . . . . . . . . . . . . . . 13
6.8. Maintaining Local Connectivity . . . . . . . . . . . . . 14
6.9. Initiating Triggered Route Replies (Triggered RREPs) . . 14
7. Multicast Route Activation (MACT) Message Format 12 7. Multicast Route Activation (MACT) Message Format 15
8. Node Operation - Multicast 13 8. Node Operation - Multicast 16
8.1. Maintaining Multicast Tree Utilization Records . . . . . 13 8.1. Maintaining Multicast Tree Utilization Records . . . . . 16
8.2. Generating Multicast RREQs . . . . . . . . . . . . . . . 13 8.2. Generating Multicast RREQs . . . . . . . . . . . . . . . 17
8.3. Forwarding Multicast Route Requests . . . . . . . . . . . 14 8.3. Forwarding Multicast Route Requests . . . . . . . . . . . 17
8.4. Generating Multicast Route Replies . . . . . . . . . . . 14 8.4. Generating Multicast Route Replies . . . . . . . . . . . 18
8.5. Forwarding Route Replies . . . . . . . . . . . . . . . . 15 8.5. Forwarding Route Replies . . . . . . . . . . . . . . . . 19
8.6. Route Deletion and Multicast Tree Pruning . . . . . . . . 16 8.6. Route Deletion and Multicast Tree Pruning . . . . . . . . 19
8.7. Repairing Link Breakages . . . . . . . . . . . . . . . . 17 8.7. Repairing Link Breakages . . . . . . . . . . . . . . . . 20
8.8. Initiating Triggered Route Replies . . . . . . . . . . . 19 8.8. Initiating Triggered Route Replies . . . . . . . . . . . 23
9. Quality of Service 20 9. Broadcast 23
10. AODV and Aggregated Networks 20 10. Quality of Service 24
11. Using AODV with Other Networks 21 11. AODV and Aggregated Networks 24
12. Extensions 21 12. Using AODV with Other Networks 25
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 13. Service Location with AODV 25
14. Security Considerations 26 14. Extensions 26
14.1. Hello Interval Extension Format . . . . . . . . . . . . . 26
14.2. Multicast Group Leader Extension Format . . . . . . . . . 27
14.3. Multicast Group Information Extension Format . . . . . . 27
14.4. Maximum Delay Extension Format . . . . . . . . . . . . . 29
14.5. Minimum Bandwidth Extension Format . . . . . . . . . . . 29
14.6. Service Resolution Extension Format . . . . . . . . . . . 30
15. Configuration Parameters 30
16. Security Considerations 31
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 allows mobile nodes to during the lifetime of the network. AODV allows mobile nodes to
respond quickly to link breakages and changes in network topology. respond quickly to link breakages and changes in network topology.
The 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 group leader number is created by the destination or the multicast group leader
for 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
skipping to change at page 2, line 10 skipping to change at page 2, line 21
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 RREQ reaches either destination. A route can be determined when the RREQ reaches either
the destination itself, or an intermediate node with a fresh enough the destination itself, or an intermediate node with a 'fresh enough'
route to the destination. The route is made available by unicasting route to the destination. A 'fresh enough' route is an unexpired
a RREP back to the source of the RREQ. Since each node receiving the route entry for the destination whose associated sequence number is
request caches a route back to the source of the request, the RREP at least as great as that contained in the RREQ. The route is made
can be unicast back from the destination to the source, or from any available by unicasting a RREP back to the source of the RREQ. Since
intermediate node that is able to satisfy the request back to the each node receiving the request caches a route back to the source of
source. RREQs are also used when a node wishes to join a multicast the request, the RREP can be unicast back from the destination to
group. A join flag in the RREQ informs nodes that when receiving the the source, or from any intermediate node that is able to satisfy
the request back to the source. A RREQ can be conditioned by
requirements on the path to the destination, namely bandwidth or
delay bounds. A RREQ can also be used to access specific service
entities and at the same time discover the IP address of the desired
service.
RREQs are also used when a node wishes to join a multicast group.
A join flag in the RREQ informs nodes that when receiving the
RREP, they are not just setting route pointers but are also setting RREP, they are not just setting route pointers but are also setting
multicast route pointers, which will be used if the route is selected multicast route pointers, which will be used if the route is selected
to be added onto the tree. to be added onto the tree.
In case AODV cannot rely on lower-level mechanisms for neighborhood For multicast groups, a Group Hello message is periodically broadcast
determination, a special ``hello'' message is defined for use at the across the network by the multicast group leader. The message
network layer. carries multicast group and corresponding group leader IP addresses.
This information is used for repairing multicast trees after a
For multicast groups, a ``Group Hello'' message is broadcast across previously disconnected portion of the network containing part of the
the network by the multicast group leader. The message carries multicast tree becomes reachable once again.
multicast group and corresponding group leader IP addresses. This
information is used for repairing multicast trees after a previously
disconnected portion of the network containing part of the multicast
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. Route table information must be kept even for ephemeral management. Route table information must be kept even for ephemeral
routes, such as are created to temporarily keep track of reverse routes, such as are created to temporarily store reverse paths
paths towards nodes originating RREQs. AODV assumes the following towards nodes originating RREQs. AODV uses the following fields with
fields exist in each route table entry: each route table entry:
- Destination IP Address - Destination IP Address
- Destination Sequence Number - Destination Sequence Number
- Hop Count - Hop Count (number of hops needed to reach destination)
- Last Hop Count (described in subsection 6.3.1)
- Next Hop - Next Hop
- Lifetime
- List of Precursors (described in Section 6.1)
- Lifetime (expiration time of the route)
- Routing Flags - Routing Flags
The following information is stored in each entry of the multicast The following information is stored in each entry of the multicast
route table for multicast tree routes: route table for multicast tree routes:
- Multicast Group IP Address - Multicast Group IP Address
- Multicast Group Leader IP Address - Multicast Group Leader IP Address
- Multicast Group Sequence Number - Multicast Group Sequence Number
- Hop Count to next Multicast Group member - Hop Count to next Multicast Group member
- Hop Count to Multicast Group leader - Hop Count to Multicast Group leader
- Next Hops - Next Hops
- Lifetime - Lifetime
The Next Hops field is a linked list of structures, each of which The Next Hops field is a linked list of structures, each of which
contains the IP address of a neighbor in the multicast tree. contains the following fields:
The IP Address of a Next Hop is only used to forward multicast - IP address of a neighbor in the multicast tree
messages after a MACT message has activated the route (see
Section 8.6). - Direction of the link
- Enabled Flag
The direction of the link is relative to the location of the group
leader, i.e. UPSTREAM is a next hop towards the group leader, and
DOWNSTREAM is a next hop away from the group leader. A node on the
multicast tree must necessarily have only one UPSTREAM link. The IP
Address of a Next Hop MUST NOT be used to forward multicast messages
until after a MACT message has enabled the route (see Section 8.6).
In order to assist applications in resolving IP addresses for their
service needs, each node maintains a list of associations between
service types and IP addresses. If no IP address is known for a
service, then the RREQ message can be used with the `S' bit set to
find such an IP address. If an IP address is known for a service,
but no path is known for the IP address, then the RREQ message
with the `S' bit reset is used as before to find a path to the IP
destination address. The association between a service type and IP
address expires after SERVICE_ADDR_TIMEOUT milliseconds. If the
service is still needed, the association must be re-established by
issuing another RREQ.
3. AODV Terminology 3. AODV Terminology
This protocol specification uses conventional meanings [1] for This protocol specification uses conventional meanings [1] for
capitalized words such as MUST, SHOULD, etc., to indicate requirement capitalized words such as MUST, SHOULD, etc., to indicate requirement
levels for various protocol features. This section defines other levels for various protocol features. This section defines other
terminology used with AODV that is not already defined in [2]. terminology used with AODV that is not already defined in [2].
active route
A routing table entry with an unexpired Lifetime and a finite
metric in the Hop Count field. A routing table may contain
entries that are not active. Only active entries can be used
to forward data packets.
forwarding node forwarding node
A node which agrees to forward packets destined for another A node which agrees to forward packets destined for another
destination node, by retransmitting them to a next hop which is destination node, by retransmitting them to a next hop which is
closer to the destination along a path which has been set up closer to the destination along a path which has been set up
using routing control messages. using routing control messages.
group leader 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
is the first such group member in the connected portion of and which is typically the first such group member in the
the network. This node is responsible for initializing and connected portion of the network. This node is responsible for
maintaining the multicast group destination sequence number. initializing and maintaining the multicast group destination
sequence number.
group leader table
The table where ad hoc nodes keep information concerning each
multicast group and its corresponding group leader. There is
one entry in the table for each multicast group for which the
node has received a Group Hello (see Section 8.2).
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 where 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
The table where ad hoc nodes keep information concerning the
first node to request to join a multicast group. There is one
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).
subnet leader subnet leader
A node which is a member of the subnet defined by a specific A node which is a member of the subnet defined by a specific
routing prefix, and which offers reachability to every other routing prefix, and which offers reachability to every other
node with the same routing prefix. The subnet leader is node with the same routing prefix. The subnet leader is
responsible for initializing and maintaining the destination responsible for initializing and maintaining the destination
sequence number for every node on the subnet. sequence number for every node on the subnet.
4. Route Request (RREQ) 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|S| Reserved | Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Broadcast ID | | Broadcast ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IP address | | Destination address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Sequence Number | | Destination Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 1
J Join flag; set when source node wants to join a 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.
S Service Location; set when a node wants to discover
a service rather than a particular IP address.
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 Hop Count The number of hops from the Source IP Address to
the node handling the request. the node handling the request.
Broadcast ID A sequence number uniquely identifying the Broadcast ID A sequence number uniquely identifying the
particular RREQ when taken in conjunction with the particular RREQ when taken in conjunction with the
source node's IP address. source node's IP address.
Destination IP Address Destination Address
The IP address of the destination for which a route The address of the service or destination for
is desired. which a route is desired. If the `S' bit is zero,
this address is an IP address. If the `S' bit
is set, the first 16 bits of the address is the
Protocol number and the last 16 bits of the address
is the Port number for the desired service (see
section 13).
Destination Sequence Number Destination Sequence Number
The last sequence number received in the past by The last sequence number received in the past by
the 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 The IP address of the node which originated the
Route Request. Route Request.
Source Sequence Number Source Sequence Number
The current sequence number to be used for route The current sequence number to be used for route
entries pointing to (and generated by) the source entries pointing to (and generated by) the source
of the route request. of the route request.
When a node wishes to repair a multicast tree, it appends the When a node wishes to repair a multicast tree, it appends the
Multicast Group Leader extension (see Section 12.2). Multicast Group Leader extension (see Section 14.2). When a node
wishes to discover a route to a server for a particular application,
instead of discovering a route to an IP address, the node sets the
Protocol and Port number into the Destination Address field, sets the
`S' bit, and takes the actions specified in Section 13.
5. Route Reply (RREP) 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|R|U| Reserved| Prefix Size | Hop Count | | Type |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 2
L If the `L' bit is set, the message is a ``hello''
message and contains a list of the node's neighbors.
R Repair flag; set when a node wants to initiate R Repair flag; set when a node is responding
a repair to connect two previously disconnected to a repair request to connect two previously
portions of the multicast tree. disconnected portions of the multicast tree.
U Update flag; set in a Group Hello, when the group U Update flag; set in a Group Hello, when the group
leader information has changed. leader information has changed.
Reserved Sent as 0; ignored on reception. Reserved Sent as 0; ignored on reception.
Prefix Size If nonzero, the Prefix Size specifies that the Prefix Size If nonzero, the Prefix Size specifies that the
indicated route vector may be used for any nodes indicated next hop may be used for any nodes with
with the same routing prefix (as defined by the the same routing prefix (as defined by the Prefix
Prefix Size) as the requested destination. Size) as the requested destination.
Hop Count The number of hops from the Source IP Address to Hop Count The number of hops from the Source IP Address to
the Destination IP Address. For multicast route the Destination IP Address. For multicast route
requests this indicates the number of hops to the requests this indicates the number of hops to the
multicast group leader. multicast tree member sending the RREP.
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 supplied. is supplied.
Destination Sequence Number Destination Sequence Number
The destination sequence number associated to the The destination sequence number associated to the
route. route.
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.
When the RREP is sent for a multicast destination, the Multicast When the RREP is sent for a multicast destination, the Multicast
Group Information extension is appended (see Section 12.3). Group Information extension is appended (see Section 14.3).
Note that the Prefix Size allows a Subnet Leader to supply a route Note that the Prefix Size allows a Subnet Leader to supply a route
for every host in the subnet defined by the routing prefix, which for every host in the subnet defined by the routing prefix, which
is determined by the IP address of the Subnet Leader and the Prefix 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 Size. In order to make use of this feature, the Subnet Leader has to
guarantee reachability to all the hosts sharing the indicated subnet guarantee reachability to all the hosts sharing the indicated subnet
prefix. The Subnet Leader is also responsible for maintaining the prefix. The Subnet Leader is also responsible for maintaining the
Destination Sequence Number for the whole subnet. Destination Sequence Number for the whole subnet.
6. 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.
6.1. 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 Hop
metric), the node also maintains a list of those neighbors that Count metric) as a routing table entry, the node also maintains a
are actively using the route. This active-list of neighbors will list of precursors that may be forwarding packets on this route.
receive notifications from the node in the event of detection of a These precursors will receive notifications from the node in the
link breakage. A neighbor is on the active list if it has sent any event of detection of the loss of the next hop link. The list of
packet to the node to be forwarded to the destination within the last precursors in a routing table entry contains those neighboring nodes
ACTIVE_ROUTE_TIMEOUT milliseconds. to which a route reply was generated or forwarded.
6.2. Generating Route Requests (RREQs) Each time a route is used to forward a data packet, its Lifetime
field is updated to be current time plus ACTIVE_ROUTE_TIMEOUT.
6.2. Maintaining Associations between Services and IP Addresses
Whenever a node needs to contact a server for a particular service
type, it consults its list of associations between service types and
IP addresses. If there is no entry for a server of the desired type,
the mobile node has to issue a RREQ with the `S' bit set.
Each entry in the service type table is valid only for
SERVICE_ADDR_TIMEOUT milliseconds, and MUST be deleted after
that amount of time. Since this timeout is much longer than that for
typical routes to IP destinations, it will often happen that a valid
association exists between a service type and an IP address, when no
valid route is available to the associated IP address.
6.3. 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 (or service) and does not have one available. This can
the destination is previously unknown to the node, or if a previously happen if the destination is previously unknown to the node, or if a
valid route to the destination expires or is broken (i.e., an previously valid route to the destination expires or is broken (i.e.,
infinite metric is associated with the route). When a route table an infinite metric is associated with the route). When a route table
entry is marked with an infinite metric, its expiration time is also entry is marked with an infinite metric, its Lifetime is also updated
updated to be the current time plus BAD_LINK_LIFETIME milliseconds. to be the current time plus BAD_LINK_LIFETIME milliseconds. After
After the expiration time, the route MAY be expunged from the node's the Lifetime expires, the route MAY be expunged from the node's route
route table. table.
After broadcasting a RREQ a node waits for a RREP, and if the reply After broadcasting a RREQ, a node waits for a RREP. If the RREP
is not received within RREP_WAIT_TIME milliseconds, 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, up to a maximum of RREQ_RETRIES times. Each
RREQ_RETRIES times. Each rebroadcast has to increment the Broadcast rebroadcast MUST increment the Broadcast ID field.
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.
6.3. Forwarding Route Requests Data packets waiting for a route (i.e., waiting for a RREP after RREQ
has been sent) SHOULD be buffered. The buffering SHOULD be FIFO. If
a RREQ has been rebroadcast RREQ_RETRIES times without receiving any
RREP, all data packets destined for the corresponding destination
SHOULD be dropped from the buffer.
6.3.1. Controlling RREQ broadcasts
To prevent unncessary network-wide broadcasts of RREQs, the
source node SHOULD use an expanding ring search technique as an
optimization. In an expanding ring search, the source node initially
uses a TTL = TTL_START in the RREQ packet IP header and sets the
timeout for receiving a RREP to 2 * TTL * NODE_TRAVERSAL_TIME
milliseconds. Upon timeout, the source rebroadcasts the RREQ with
the TTL incremented by TTL_INCREMENT. This continues until the
TTL set in the RREQ reaches TTL_THRESHOLD, beyond which a TTL =
NET_DIAMETER is used for each rebroadcast. Each time, the timeout
for receiving a RREP is calculated as before. Each rebroadcast
increments the Broadcast ID field in the RREQ packet. The RREQ
can be rebroadcast with TTL = NET_DIAMETER up to a maximum of
RREQ_RETRIES times.
When a RREP is received, the Hop Count used in the RREP packet is
remembered as Last Hop Count in the routing table. When a new route
to the same destination is required at a later time (e.g., upon route
loss), the TTL in the RREQ IP header is initially set to this Last
Hop Count plus TTL_INCREMENT. Thereafter, following each timeout the
TTL is incremented by TTL_INCREMENT until TTL = TTL_THRESHOLD is
reached. Beyond this TTL = NET_DIAMETER is used as before.
As a further optimization, timeouts MAY be determined dynamically via
measurements, instead of using a statically configured value related
to NODE_TRAVERSAL_TIME. To accomplish this, the RREQ may carry the
timestamp via an extension field as defined in Section 14 to be
carried back by the RREP packet (again via an extension field). The
difference between the current time and this timestamp will determine
the route discovery latency. The timeout may be set to be a small
factor of the average of the last few route discovery latencies
for the concerned destination. These latencies may be recorded as
additional fields in the routing table.
If the optimizations described in this section are used, an expired
routing table entry should not be expunged too early. Otherwise, the
soft states corresponding to the route (e.g., Last Hop Count) will be
lost. In such cases, a longer routing table entry expunge time may
be specified. In general, any routing table entry waiting for a RREP
should not be expunged before the timeout for receiving RREP.
6.4. Forwarding RREQs
When a node receives a broadcast RREQ, it first checks to see When a node receives a broadcast RREQ, it first checks to see
whether it has received a RREQ with the same Source IP Address and whether it has received a RREQ with the same Source IP Address and a
a broadcast ID field of equal unsigned integer value within the Broadcast ID field of equal unsigned integer value within the last
last BCAST_ID_SAVE milliseconds. If such a RREQ has been received, BCAST_ID_SAVE milliseconds. If such a RREQ has been received, the
the node silently discards the newly received RREQ. Otherwise, the node silently discards the newly received RREQ. The rest of this
node checks to see whether it has a route to the destination. If subsection describes actions taken for RREQs that are not discarded.
the node does not have a route, it rebroadcasts the RREQ from its
interface(s) but using its own IP address in the IP header of the
outgoing RREQ. The TTL or hop limit field in the outgoing IP header
is decreased by one. The Hop Count field in the broadcast RREQ
message is incremented by one, to account for the new hop through the
intermediate node. In this case, the node also creates or updates a
reverse route to the Source IP Address in its routing table with next
hop equal to the IP address of the neighboring node that sent the
broadcast RREQ (often not equal to the Source IP Address field in the
RREQ message). This reverse route might be used for an eventual RREP
back to the node which originated the RREQ (identified by the Source
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 6.4.1. Handling Route Requests (RREQs) for IP Destinations
destination, it compares the destination sequence number (dest-seqno)
for that route with the Destination Sequence Number field of the If the `S' bit is not set, the node checks to see whether it has
incoming RREQ. If the node's existing dest-seqno is smaller than a route to the destination. If the node does not have a route,
the Destination Sequence Number field of the RREQ, the node again it rebroadcasts the RREQ from its interface(s) but using its own
rebroadcasts the RREQ just as if it did not have a route to the IP address in the IP header of the outgoing RREQ. The TTL or hop
destination at all. limit field in the outgoing IP header is decreased by one. The Hop
Count field in the broadcast RREQ message is incremented by one, to
account for the new hop through the intermediate node. The node
also creates or updates a reverse route to the Source IP Address
in its routing table with next hop equal to the IP address of the
neighboring node that sent the broadcast RREQ (often not equal to the
Source IP Address field in the RREQ message). This reverse route
might be used for an eventual RREP back to the node which originated
the RREQ (identified by the Source IP Address). If no route exists
for the Source IP Address, or if an existing route will 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 the requested route, it
compares the destination sequence number (dest-seqno) for that route
with the Destination Sequence Number field of the incoming RREQ.
If the node's existing dest-seqno is smaller than 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 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 6.4. further in section 6.5.
6.4. Generating Route Replies (RREPs) 6.4.2. Handling Route Requests (RREQs) for Services
If the `S' bit is set in the RREQ message header, and if a node can
resolve the service type indicated by the requested in the RREQ,
and if the node has a valid route to the resolved IP address for
the service type, then the node can generate a RREP as specified
in section 6.6. Otherwise, if the node has already rebroadcast a
RREQ with the same Broadcast ID from the same source node, it MUST
silently discard the RREQ. Otherwise the node MUST rebroadcast the
RREQ.
6.5. Generating Route Replies (RREPs) for IP Destinations
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 fresh enough route to satisfy the request, the node generates a
RREP message and unicasts it back to the node indicated by the RREP message and unicasts it back to the node indicated by the
Source IP Address field of the received RREQ. If the node is not the Source IP Address field of the received RREQ. If the node is not the
destination node, it copies over the destination sequence number from destination node, it copies over the destination sequence number from
the route table entry. If the generating node is the destination the route table entry. If the generating node is the destination
itself, it uses a destination sequence number at least equal to a itself, it uses a destination sequence number at least equal to a
sequence number generated after the last detected change in its sequence number generated after the last detected change in its
neighbor set and at least equal to the destination sequence number in neighbor set and at least equal to the destination sequence number in
the RREQ. If the destination node has not detected any change in its the RREQ. If the destination node has not detected any change in its
set of neighbors since it last incremented its destination sequence set of neighbors since it last incremented its destination sequence
number, it may use the same destination sequence number. 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 6.3. The Source IP Address, if necessary as described in section 6.4. 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 Lifetime for the route table entry is set to the
to the current time plus ACTIVE_ROUTE_TIMEOUT milliseconds. 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 places its distance in hops from the destination generating node places its distance in hops from the destination
in the Hop Count field. If the generating node is the destination in the Hop Count field. If the generating node is the destination
node, it places the value zero in the Hop Count field. The Hop Count node, it places the value zero in the Hop Count field. The Hop Count
field is incremented by one at each hop as the RREP is forwarded to field is incremented by one at each hop as the RREP is forwarded to
the source. When the RREP reaches the source, the Hop Count will the source. When the RREP reaches the source, the Hop Count will
represent the distance, in hops, of the destination from the source. 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 time in its route table entry. Otherwise, if the generating node
is also the destination node, it copies the value MY_ROUTE_TIMEOUT is also the destination node, it copies the value MY_ROUTE_TIMEOUT
into the Lifetime field of the RREP. Each node MAY make a separate into the Lifetime field of the RREP. Each node MAY make a separate
determination about its value MY_ROUTE_TIMEOUT. 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. precursor list for the reverse path route entry. In addition, the
generating node puts the last hop node (from which it received the
6.5. Maintaining Local Connectivity RREQ, as indicated by the source IP address field in the IP header)
into the precursor list for the forward path towards the destination.
Each forwarding node SHOULD keep track of which of its neighbors are
active next hops (i.e., which next hops have been used to forward
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 6.6. Generating Route Replies (RREPs) for Services
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. If a node hosts a service at the protocol and port number indicated
in the RREQ, it generates a RREP and sends it back to the requesting
node. The generating node copies the value MY_ROUTE_TIMEOUT into
the Lifetime field of the RREP, and puts the value zero for the Hop
Count. The destination sequence number is inserted just as indicated
in the previous section.
- A RREQ unicast to the next hop, asking for a route to the next If a node has a current resolution for the service type to an IP
hop. address, and if it has a valid route for that IP address, it SHOULD
generate a RREP and send it back to the requesting node. The
generating node copies the remaining value for the lifetime of the
valid route into the Lifetime field of the RREP, and puts the value
zero for the Hop Count. The destination sequence number is inserted
just as indicated in the previous section.
- An ICMP Echo Request message unicast to the next hop. In order to indicate to the source of the RREQ the particular service
for which the RREQ was sent, the generating node includes a Service
Resolution extension (see section 14.6).
The ICMP ACK message SHOULD be sent to a forwarding node by a next The mechanism for forwarding route replies is described in section
hop which is also the destination IP address shown in the IP header 8.3.
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 6.7. Hello Messages
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 A node MAY offer connectivity information by broadcasting local Hello
``hello'' messages as follows. Every HELLO_INTERVAL milliseconds, messages as follows. Every HELLO_INTERVAL milliseconds, the node
the node checks whether it has sent a broadcast (e.g., a RREQ) within checks whether it has sent a broadcast (e.g., a RREQ) within the
the last HELLO_INTERVAL. If it has not, it MAY generate a ``hello'' last HELLO_INTERVAL. If it has not, it MAY generate a broadcast RREP
message. This hello message is a broadcast RREP with TTL = 1, and with TTL = 1, called a Hello message, with the message fields set as
the message fields set as follows: follows:
Destination IP Address Destination IP Address
The node's IP address. The node's IP address.
Destination Sequence Number Destination Sequence Number
The node's latest sequence number. The node's latest sequence number.
Hop Count 0 Hop Count 0
Lifetime (1 + ALLOWED_HELLO_LOSS) * HELLO_INTERVAL Lifetime ALLOWED_HELLO_LOSS * HELLO_INTERVAL
In addition to regular Hello messages, each multicast group A node MAY determine connectivity by listening for packets from
leader will also broadcast a Group Hello message system-wide every its set of neighbors. If it receives no packets for more than
GROUP_HELLO_INTERVAL milliseconds. This system-wide Group Hello ALLOWED_HELLO_LOSS * HELLO_INTERVAL milliseconds, the node SHOULD
message has IP TTL value greater than the diameter of the network assume that the link to this neighbor is currently broken. When this
and is initialized to a hop count of zero. The hop count value is happens, the node SHOULD proceed as in Section 6.9.
incremented by one by each node as the message is forwarded. This
Group Hello message contains the IP Addresses of the Multicast Groups
for which the node is the Group Leader, along with the corresponding
multicast group sequence numbers. Nodes in the multicast tree can
use these messages to update their current distance from the group
leader. The information in the message is also used for merging
partitioned multicast trees, as is described later. See Section 12.3
for extensions needed to complete a GROUP_HELLO message.
6.6. Initiating Triggered Route Replies (Triggered RREPs) 6.8. Maintaining Local Connectivity
A node can trigger an unsolicited RREP if either it detects a link Each forwarding node SHOULD keep track of its active next hops (i.e.,
breakage for a next hop along an active route in its route table, or which next hops have been used to forward packets towards some
if it receives a RREP from a neighbor with an infinite metric for an destination within the last ACTIVE_ROUTE_TIMEOUT milliseconds). This
active route (i.e., containing a Destination IP Address for which is done by updating the Lifetime field of a routing table entry used
there is a route table entry with a nonempty active-list) to forward data packets to current time plus ACTIVE_ROUTE_TIMEOUT
milliseconds. For purposes of efficiency, each node may try to
learn which of these active next hops are really a neighbor at the
current time using one or more of the available link or network layer
mechansisms, as described below.
The unsolicited RREP is broadcast to inform each neighbor in the - Any suitable link layer notification, such as those provided by
nonempty active-list for the route to that destination. The contents IEEE 802.11, can be used to determine connectivity, each time
of the RREP fields are set as follows: a packet is transmitted to an active next hop. For example,
absence of a link layer ACK or failure to get a CTS after sending
RTS, even after the maximum number of retransmission attempts,
will indicate loss of the link to this active next hop.
L 0 - Passive acknowledgment can be used when the next hop is expected
to forward the packet, by listening to the channel for a
transmission attempt made by the next hop. If transmission is
not detected within NEXT_HOP_WAIT milliseconds or the next hop is
not a forwarding node (and thus is never supposed to transmit the
packet) one of the following methods should be used to determine
connectivity.
* Receiving an ICMP ACK message from the next hop. The ICMP
ACK message SHOULD be sent to a forwarding node by a next hop
which is also the destination as in the in the IP header of
the packet. This should be done only when this destination
has not sent any packets to the concerned forwarding node
within the last HELLO_INTERVAL milliseconds.
* 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.
If a link to the next hop cannot be detected by any of these methods,
the forwarding node SHOULD assume that the link is broken, and take
corrective action by following the methods specified in Section 6.9.
6.9. Initiating Triggered Route Replies (Triggered RREPs)
A node can send a Triggered RREP (also called unsolcited RREP) if
either it detects a link breakage for an active next hop in its
routing table, or if it receives a RREP from a neighbor with an
infinite metric for an active route.
The Triggered RREP is sent to each node in the precursor list for the
routing table entry for that destination. The contents of the RREP
fields are set as follows:
Hop Count 255 (= infinity) 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 for One plus the destination sequence number recorded for
the route. the route.
7. Multicast Route Activation (MACT) Message Format 7. Multicast Route Activation (MACT) Message Format
0 1 2 3 0 1 2 3
skipping to change at page 12, line 16 skipping to change at page 15, line 25
Destination Sequence Number Destination Sequence Number
One plus the destination sequence number recorded for One plus the destination sequence number recorded for
the route. the route.
7. Multicast Route Activation (MACT) Message Format 7. Multicast Route Activation (MACT) 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 |P|G| Reserved | | Type |P|G|U| Reserved | Hopcount |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multicast Group IP address | | Multicast Group IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IP address | | Source IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Sequence Number | | Source Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of the Multicast Route Activation message is illustrated The format of the Multicast Route Activation message is illustrated
above, and contains the following fields: above, and contains the following fields:
skipping to change at page 12, line 39 skipping to change at page 15, line 48
P Prune flag; set when a node wishes to prune itself P Prune flag; set when a node wishes to prune itself
from the tree, unset when the node is activating a from the tree, unset when the node is activating a
tree link. tree link.
G Group Leader flag; set by a multicast tree member that G Group Leader flag; set by a multicast tree member that
fails to repair a multicast tree link breakage, and fails to repair a multicast tree link breakage, and
indicates to the group member receiving the message indicates to the group member receiving the message
that it should become the new multicast group leader. that it should become the new multicast group leader.
U Update flag; set when a multicast tree member has
repaired a broken tree link and is now a new distance
from the group leader.
Reserved Sent as 0; ignored on reception. Reserved Sent as 0; ignored on reception.
Hop Count The distance of the sending node from the multicast
group leader. Used only when the 'U' flag is set;
otherwise sent as 0.
Multicast Group IP Address Multicast Group IP Address
The IP address of the Multicast Group for which a The IP address of the Multicast Group for which a
route is supplied. route is supplied.
Source IP Address Source IP Address
The IP address of the node which originated the Route The IP address of the sending node.
Request.
Source Sequence Number Source Sequence Number
The current sequence number for route information The current sequence number for route information
generated by the source of the route request. generated by the source of the route request.
To prune itself from the tree (i.e., inactivate its last link to the 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' multicast tree), a multicast tree member sends a MACT with the 'P'
flag = 1 to the next hop. A multicast tree member that has more than flag = 1 to its next hop on the multicast tree. A multicast tree
one next hop to the multicast tree SHOULD NOT try to prune itself member that has more than one next hop to the multicast tree SHOULD
from the multicast tree. 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 MACTs 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 multicast tree to which a node belongs, either because it For each multicast tree to which a node belongs, either because it
skipping to change at page 13, line 46 skipping to change at page 17, line 16
A node sends a multicast 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 group but does not have a route to that group. If the node wishes
to join the multicast group, it sets the `J' flag in the RREQ; to join the multicast group, it sets the `J' flag in the RREQ;
otherwise, it leaves the flag unset. The destination address of otherwise, it leaves the flag unset. The destination address of
the RREQ is always set to the multicast group address. If the node the RREQ is always set to the multicast group address. If the node
knows the group leader and has a route to it, the node will place knows the group leader and has a route to it, the node will place
the group leader's address in the Multicast Group Leader extension the group leader's address in the Multicast Group Leader extension
(Section 12.2), and will unicast the RREQ to the corresponding next (Section 14.2), and will unicast the RREQ to the corresponding next
hop for that destination. Otherwise, if the node does not have a hop for that destination. Otherwise, if the node does not have a
route to the group leader, or if it does not know who the multicast route to the group leader, or if it does not know who the multicast
group leader is, it will broadcast the RREQ and will not include the group leader is, it will broadcast the RREQ and will not include the
extension field. extension field.
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 6.2. destination address is the same as that described in Section 6.3.
The node may resend the RREQ up to RREQ_RETRIES times if a RREP The node may resend the RREQ up to RREQ_RETRIES additional times if
is not received. If a RREQ was unicast to a group leader and a a RREP is not received. If a RREQ was unicast to a group leader and
RREP is not received within RREP_WAIT_TIME milliseconds, the node a RREP is not received within RREP_WAIT_TIME milliseconds, the node
will broadcast subsequent RREQs for that multicast group across will broadcast subsequent RREQs for that multicast group across the
the network. If a RREP is not received after RREQ_RETRIES total network. If a RREP is not received after RREQ_RETRIES additional
requests, the node may assume that there are no other members of that requests, the node may assume that there are no other members of that
particular group within the connected portion of the network. If it particular group within the connected portion of the network. If it
wanted to join the multicast group, it MAY then become the multicast wanted to join the multicast group, it MAY then become the multicast
group leader for that multicast group and initialize the destination group leader for that multicast group and initialize the destination
sequence number of the multicast group. Otherwise, if it only wanted sequence number of the multicast group. Otherwise, if it only wanted
to send packets to that group without actually joining the group, it to send packets to that group without actually joining the group, it
will drop the packets it had for that group. will drop the packets it had for that group.
Each node in the network receiving a RREQ message with the `J' flag If the node wishes to join or send a message to a multicast group,
set MAY check its request table to see whether there is already an it first consults its Group Leader Table. Based on the existence of
entry for this multicast group. If there is no entry for the group, an entry for the multicast group in this table, the node will then
the node records the IP Address of the node which sent the RREQ, formulate and send the RREQ as described at the beginning of this
together with the IP address of the group for which it requested to section.
be a member, in the Request Table. Because the first node to request
membership in a group becomes the multicast group leader, entries
in the Request Table represent multicast group leaders. If the
multicast group leader changes at any time, the nodes will note this
change by updating their Request Table so that the node IP address
matches that of the new group leader. If the node wishes to join or
send a message to a multicast group, it first consults its Request
Table. Based on the existence of an entry for the multicast group
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 6.3, with one exception. If the RREQ is a join request, when Section 6.4, with one exception. If the RREQ is a join request, when
the node creates a reverse route to the Source IP Address, it places the node creates a reverse route to the Source IP Address, it places
the information in its Multicast Route table. The generation of the the information in its Multicast Route table. The generation of the
route reply (RREP) message is discussed in the following section. 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 RREQ for a multicast group, and If a node receives a multicast join RREQ for a multicast group, and
it is already a member of the multicast tree for that group, the it is already a member of the multicast tree for that group, the
node updates its Multicast Route Table and then generates a RREP node updates its Multicast Route Table and then generates a RREP
message. It unicasts the RREP back to the node indicated by the message. It unicasts the RREP back to the node indicated by the
Source IP Address field of the received RREQ. The RREP contains Source IP Address field of the received RREQ. The RREP contains the
the current sequence number for the multicast group, the distance current sequence number for the multicast group, the distance of the
of the responding node from the nearest multicast group member, responding node from the multicast group leader, and the IP address
and the IP address of the group leader. Further information about of the group leader. Further information about the multicast group
the multicast group leader is entered into the Multicast Group leader is entered into the Multicast Group Information extension (see
Information extension (see Section 12.3). Section 14.3).
A node can only respond to a join RREQ if it is a member of the A node can only respond to a join RREQ if it is a member of the
multicast tree. If a node receives a multicast route request that is multicast tree. If a node receives a multicast route request that
not a join message, it can reply if it has a route to the multicast is not a join message, it can reply if it has a current route to the
tree. Otherwise it will continue forwarding the message. If a node multicast tree. Otherwise it will continue forwarding the request.
receives a multicast join route request for a multicast group and it If a node receives a join route request for a multicast group and it
is not already a member of the multicast tree for that group, it will is not already a member of the multicast tree for that group, it will
rebroadcast the RREQ to its neighbors. 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
group leader), but the node is in fact not the group leader, it group leader), but the node is in fact not the group leader, it
can simply ignore the RREQ. The source node will time out after can simply ignore the RREQ. The source node will time out after
RREP_WAIT_TIME milliseconds and will broadcast a new RREQ without the RREP_WAIT_TIME milliseconds and will broadcast a new RREQ without the
group leader address specified. group leader address specified.
Regardless of whether the multicast group leader or an intermediate Regardless of whether the multicast group leader or a multicast tree
node generates the RREP, the RREP fields are set as follows: member generates the RREP, the RREP fields are set as follows:
Hop Count Distance of the responding node to the nearest Hop Count 0
multicast group member.
Destination IP Address Destination IP Address
The IP address of the node which supplies a route to The IP address of the node which supplies a route to
the multicast group. the multicast group.
Destination Sequence Number Destination Sequence Number
The destination sequence number of the node which The destination sequence number of the node which
supplies a route to the multicast group. 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.
The Multicast Group Information extension described in Section 12.3 The Multicast Group Information extension described in Section 14.3
is also included. is also included.
8.5. Forwarding Route Replies 8.5. Forwarding Route Replies
If an intermediate node receives a RREP in response to a RREQ that it If an intermediate node receives a RREP in response to a RREQ that
has transmitted (or retransmitted on behalf of some other node), it it has transmitted (or retransmitted on behalf of some other node),
increments the Hop Count and forward the RREP along the path to the it increments the Hop Count and Multicast Group Hopcount fields and
source of the RREQ. forwards the RREP along the path to the source of the RREQ.
When the node receives more than one RREP for the same RREQ, it When the node receives more than one RREP for the same RREQ, it saves
operates in a manner similar to the source node by saving the route the route information with the greatest sequence number, and beyond
information with the greatest sequence number, and beyond that the that the lowest hop count; it discards all other RREPs. This node
lowest hop count; it discards all other RREPs. This node forwards forwards the first RREP towards the source of the RREQ, and then
the first RREP towards the source of the RREQ, and then forwards forwards later RREPs only if they have a greater sequence number or
later RREPs only if they have a greater sequence number or smaller smaller metric.
metric.
8.6. Route Deletion and Multicast Tree Pruning 8.6. Route Deletion and Multicast Tree Pruning
When a node broadcasts a RREQ message, it is likely to receive more 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 to If the RREQ was a join request, the RREP message traveling back to
the node which originated the request sets up route pointers, which the node which originated the request sets up route pointers, which
may eventually graft 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
loop will be formed. Hence, in order to prevent the formation of will be formed. Hence, in order to prevent the formation of any such
any such loops, it is necessary to activate only one of the routes loops, it is necessary to activate only one of the routes created
created by the RREP messages. The RREP containing the largest by the RREP messages. The RREP containing the largest destination
destination sequence number is chosen to be the added branch to the sequence number is chosen to be the added branch to the multicast
multicast tree. In the event that a node receives more than one tree. In the event that a node receives more than one RREP with
RREP with the same (largest) sequence number, it selects the first the same (largest) sequence number, it selects the first one with
one with the smallest hop count, i.e., the shortest distance to a the smallest hop count, i.e., the shortest distance to a member of
member of the multicast group. After waiting for RREP_WAIT_TIME the multicast tree. After waiting for RREP_WAIT_TIME milliseconds,
milliseconds, the node must choose the route it wishes to use as the node must choose the route it wishes to use as its link to
its link to the multicast tree. This is accomplished by sending a the multicast tree. This is accomplished by sending a Multicast
Multicast Activation (MACT) message. The Destination IP Address of Activation (MACT) message. The Destination IP Address field of the
the MACT packet is set to the IP address of the multicast group. The MACT packet is set to the IP address of the multicast group. The
node will unicast this message to the selected next hop, effectively node unicasts this message to the selected next hop, effectively
activating the route. After receiving this message, the node's activating the route. After receiving this message, the node's
neighbor to which the MACT was sent activates the route entry for the neighbor to which the MACT was sent activates the route entry for the
link in the multicast route table, thereby finalizing the creation of link in the multicast route table, thereby finalizing the creation of
the tree branch. All neighbors not receiving this message will time the tree branch. All neighbors not receiving this message time out
out and delete that node as a next hop for the multicast group in and delete that node as a next hop for the multicast group in their
their route tables, having never activated the route entry for that route tables, having never activated the route entry for that next
next hop. hop.
Two scenarios exist for a neighboring node receiving the MACT Two scenarios exist for a neighboring node receiving the MACT
message. If this node was previously a member of the multicast message. If this node was previously a member of the multicast
tree, it will not propagate the MACT message any further. However, tree, it does not propagate the MACT message any further. However,
if the next hop selected by the source node's MACT message was not if the next hop selected by the source node's MACT message was not
previously a multicast tree member, it will have propagated the previously a multicast tree member, it will have propagated the
original RREQ further up the network in search of nodes which are original RREQ further up the network in search of nodes which are
tree members. Thus it is possible that this node also received more tree members. Thus it is possible that this node also received more
than one RREP, as noted in section 8.5. than one RREP, as noted in section 8.5.
When the node receives an MACT announcing it as the next hop, it will When the node receives a MACT announcing it as the next hop, it sends
send its own MACT announcing the node it has chosen as its next hop, its own MACT announcing the node it has chosen as its next hop, and
and so on up the tree, until a node which was already a part of the so on up the tree, until a node which was already a part of the
multicast tree is reached. multicast tree is reached.
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 (i.e., multicast router for any other nodes in the multicast group (i.e.,
if it is a leaf node). If this is the case, it may unicast to its if it is a leaf node). If this is the case, it may unicast to its
next hop on the tree an MACT message with the 'P' flag set and with next hop on the tree a MACT message with the 'P' flag set and with
the Destination IP Address set to the IP address of the multicast the Destination IP Address set to the IP address of the multicast
group in order to prune itself from the tree. Similarly, if the node group in order to prune itself from the tree. Similarly, if the node
receiving this message is not a member of the multicast group and receiving this message is not a member of the multicast group and
does not have any other nodes routing through it, it may send its own does not have any other nodes routing through it, it may send its own
MACT message up the tree. MACT message up the tree.
8.7. Repairing Link Breakages 8.7. Repairing Link Breakages
Branches of the multicast tree become invalid if they time out Branches of the multicast tree become invalid if they time out (the
(the Lifetime associated with the route expires), or if a link Lifetime associated with the route expires), or if a link breakage
breakage results in an infinite metric being associated with the results in an infinite metric being associated with the route. When
route. When a link breakage is detected between two nodes on the a link breakage is detected between two nodes on the multicast tree,
multicast tree, the node downstream of the break (i.e., the node the node downstream of the break (i.e., the node which is further
which is further from the multicast group leader) is responsible from the multicast group leader) is responsible for initiating the
for initiating the repair of the broken link. In order to build repair of the broken link. In order to build the route back up,
the route back up, this node will broadcast a RREQ with destination this node broadcasts a RREQ with destination IP address set to the
IP address set to the IP address of the group leader and with the IP address of the group leader and with the `J' flag set. The
`J' flag set. The destination sequence number of the RREQ is the destination sequence number of the RREQ is the last known sequence
last known sequence number of the multicast group. The Multicast number of the multicast group. The Multicast Group Hop Count field
Group Hop Count field is set to the distance of the source node from is set to the distance of the source node from the multicast group
the multicast group leader. Only a node which has a hop count for leader. Only a node which has a hop count for the multicast group
the multicast group less than or equal to the indicated value can less than or equal to the indicated value can respond. This hop
respond. This hop count requirement is included to prevent nodes count requirement is included to prevent nodes on the same side of
on the same side of the break as the node initiating the repair the break as the node initiating the repair from replying to the
from replying to the RREQ. The RREQ is broadcast using an expanding RREQ. The RREQ is broadcast using an expanding rings search. Because
rings search. Because of the high probability that other nearby of the high probability that other nearby nodes can be used to
nodes can be used to rebuild the route to the group leader, the rebuild the route to the group leader, the original RREQ is broadcast
original RREQ is broadcast with a TTL (time to live) field value with a TTL (time to live) field value equal to the Multicast
equal to the Multicast Group Hop Count. In this way, the effects of Group Hop Count. In this way, the effects of the link breakage
the link breakage may be localized. If no reply is received within may be localized. If no reply is received within RREP_WAIT_TIME
RREP_WAIT_TIME milliseconds, all subsequent RREQs (up to RREQ_RETRIES milliseconds, all subsequent RREQs (up to RREQ_RETRIES additional
total attempts) will be broadcast across the entire network. Any attempts) will be broadcast across the entire network. Any node that
node that is a part of the multicast tree and that has a multicast is a part of the multicast tree and that has a multicast group hop
group hop count smaller than that contained in the RREQ can return count smaller than that contained in the RREQ can return a RREP. If
a RREP. If there is more than one RREP received at the originating there is more than one RREP received at the originating node, route
node, route deletions occur as described in the previous section. deletions occur as described in the previous section.
If no response is received after RREQ_RETRIES broadcasts, it can be At the end of the discovery period, the node selects its next hop
assumed that the network has become partitioned and the multicast and unicasts a MACT message to that node to activate the link, as
tree cannot be repaired at this time. In this situation, if the described in Section 8.6. Additionally, since the node was repairing
node which had initiated the route rebuilding was a multicast group a tree breakage, it is likely that it is now a different distance
member, it will become the new multicast group leader for its part of from the group leader than it was before the break. If this is the
the multicast tree partition. It broadcasts a Group Hello with the case, it must inform its DOWNSTREAM next hops of their new distance
multicast group address extension field containing the corresponding from the group leader. It does this by sending its downstream next
multicast group IP address included. The `U' flag in the Group Hello hops a MACT message with the 'U' flag set, and the Hopcount field
is set, indicating that there has been a change in the group leader set to the node's new distance from the group leader. This 'U' flag
information. All nodes receiving this message update their Request indicates that multicast tree nodes should update their distance from
Tables to indicate the new group leader information. Nodes which are the group leader. If these nodes have downstream next hops, they in
a part of the multicast tree also update the group leader information turn must send a MACT message with a set 'U' flag to their next hops,
for that group in their Multicast Route Table to indicate the new and so on. The Hopcount field is incremented by one each time the
group leader. On the other hand, if the node which had initiated the packet is received.
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 If a node attempting to repair a tree link breakage does not receive
a MACT message, with the 'P' flag set, to its next hop, thereby a response after RREQ_RETRIES attempts, it can be assumed that the
indicating that it is pruning itself from the tree. The node network has become partitioned and the multicast tree cannot be
receiving this message will note that it is coming from its upstream repaired at this time. In this situation, if the node which had
link, i.e., from a node that is closer to the group leader than it initiated the route rebuilding was a multicast group member, it will
is. If the node receiving this message is a multicast group member, become the new multicast group leader for its part of the multicast
it will become the new group leader and will broadcast a Group tree partition. It broadcasts a Group Hello with the multicast
Hello message as indicated above. If it is not a multicast group group address extension field containing the corresponding multicast
member and it only has one other next hop link, it will similarly group IP address included. The `U' flag in the Group Hello is
prune itself from the tree and this process will continue until a set, indicating that there has been a change in the group leader
multicast group member is reached. On the other hand, if the node information. All nodes receiving this message update their Group
which initiated the rebuilding is not a group member and it has more Leader Table to indicate the new group leader information. Nodes
than one next hop for the tree, it cannot prune itself, since doing which are a part of the multicast tree also update the group leader
so would partition the tree. It instead chooses one of its next hops information for that group in their Multicast Route Table to indicate
and sends an MACT with the 'G' flag set. This flag indicates that the new group leader.
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 On the other hand, if the node which had initiated the repair is
will become the group leader. Otherwise, the node will unicast its not a multicast group member, there are two possibilities. If it
own MACT message with the 'G' flag set to one of its next hops, and only has one next hop for the multicast tree, it will unicast a MACT
so on until a group member is reached. 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 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 a 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 can 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 the network will know that it has come into contact with a node from
other partition of the network by noting the difference in the Group the other partition of the network by noting the difference in
Hello message multicast group leader information. A node which is a the Group Hello message multicast group leader information. The
part of the network partition with the lower group leader IP address multicast group leader with the lower IP address initiates the
and which is also a member of the multicast tree can initiate the tree repair. For the purposes of this explanation, call this node
tree repair. It will unicast a RREQ message with the `R' flag set GL1. GL1 unicasts a RREQ with both the 'J' and 'R' flags set to
back to the multicast group leader of its partition in order to get the group leader of the other network partition (GL2), using the
permission to rebuild the tree. The node must seek permission to node it had received the Group Hello message from as the next hop.
rebuild the tree in order to prevent multiple nodes from attempting This RREQ contains the current value of the partitions multicast
to rebuild the tree if contact between the two partitions is group sequence number. If any node that receives the RREQ is a
re-established in more than one place. Multiple repairs would create member of GL2's multicast tree, it MUST forward the RREQ along
loops within the multicast tree. The group leader is the only node its upstream link, i.e. towards the group leader. This prevents
which can respond to a RREQ with the `R' flag set. It will respond any loops from being formed after the repair. Upon receiving the
to the request by sending a RREP granting permission to one and only RREQ, GL2 takes the larger of its and the received multicast group
one node to rebuild the tree. Any nodes which requested permission sequence number, increments this value by one, and responds with
and which do not receive a RREP will time out and not attempt the a RREP. This is the group leader which will become the leader of
repair. As the RREP travels back to the node, it will establish a the reconnected multicast tree. The 'R' flag of the RREP is set,
multicast tree branch if one did not already exist. After receiving indicating that this RREP is in response to a repair request. As
the RREP, the node which sent the repair request will unicast a RREQ the RREP is propagated back to GL1, nodes add the incoming and
to the group leader of the other network partition, using the node outgoing links to the Multicast Route Table next hop entries if these
it had received the Group Hello message from as the next hop. This entries do not already exist. The nodes also enable these entries,
RREQ will contain the current value of the partitions multicast group thereby adding the branch on to the multicast tree. If a node that
sequence number. Upon receiving the RREQ, the multicast group leader was previously a member of GL1's tree receives the RREP, it MUST
will take the larger of its and the received multicast group sequence forward the packet along its link to its group leader (G1). It then
number, increment this value by one, and respond with a RREP. This changes the direction of the next hop link associated with GL1 to
is the group leader which will become the leader of the reconnected downstream and sets the direction of the link on which it received
multicast tree. As the RREP is propagated back to the source node, a the RREP to upstream. When the GL1 receives the RREP, it sets the
branch on to the multicast tree is added. When the initiating node link from which it received the RREP as its upstream link. The tree
receives the RREP, the tree will be reconnected. The next time the is now reconnected. The next time GL2 broadcasts a Group Hello, it
group leader broadcasts a Group Hello, it will set the `U' flag to sets the `U' flag to indicate that there is a change in the group
indicate that there is a change in the group leader information and leader information and group members should update the corresponding
group members should update the corresponding information. The node information. GL1 also notes this message and updates its tables
which was the group leader of the other partition will also note this to indicate that the other group leader is now the multicast group
message and update its tables to indicate that the other group leader leader for the entire network. Additionally, all network nodes
is now the multicast group leader for the entire network. update their Group Leader Table to reflect the new group leader
information.
8.8. Initiating Triggered Route Replies 8.8. Initiating Triggered Route Replies
A node can trigger an unsolicited RREP if it sends a RREQ to join A node can trigger an unsolicited RREP if it sends a RREQ to join
a multicast group and after RREQ_RETRIES times does not receives a multicast group and after RREQ_RETRIES times does not receives
a response. The node will then become the new multicast group a response. The node will then become the new multicast group
leader, and it will broadcast a RREP with infinity TTL (a Group leader, and it will broadcast a RREP with infinity TTL (a Group
Hello message) and with the multicast group IP Address / Sequence Hello message) and with the multicast group IP Address / Sequence
number extension information set to reflect that it is now the group number extension information set to reflect that it is now the group
leader for the multicast group. In addition, in order to ensure leader for the multicast group. In addition, in order to ensure
nodes maintain consistent and up-to-date information about who the nodes maintain consistent and up-to-date information about who the
multicast group leaders are, any node which is a group leader for a multicast group leaders are, any node which is a group leader for a
multicast group will broadcast such a Group Hello across the network multicast group will broadcast such a Group Hello across the network
every GROUP_HELLO_INTERVAL milliseconds. The contents of the RREP every GROUP_HELLO_INTERVAL milliseconds. The contents of the RREP
fields (including the Multicast Group Information Extension) are set fields (including the Multicast Group Information Extension) are set
as follows: as follows:
L 0
Hop Count 0 Hop Count 0
Destination IP Address Destination IP Address
The IP Address of the node sending the Group Hello. The IP Address of the node sending the Group Hello.
Destination Sequence Number Destination Sequence Number
The node's latest destination sequence number. The node's latest destination sequence number.
Multicast Group IP Address Multicast Group IP Address
The IP Address of the Multicast Group for which the The IP Address of the Multicast Group for which the
node is the group leader. node is the group leader.
Multicast Group Sequence Number Multicast Group Sequence Number
One plus the last known sequence number of the One plus the last known sequence number of the
multicast group. multicast group.
Nodes receiving the Group Hello incrememt the Hop Count field by one Nodes receiving the Group Hello increment the Hop Count field and the
before forwarding the message. Multicast Tree Hop Count Extension field by one before forwarding the
message.
9. Quality of Service 9. Broadcast
When a node wishes to generate a broadcast, it sends the broadcast
packet to address 255.255.255.255. AODV does not define any valid
behavior for transmissions to any directed broadcast address.
Every node maintains a list to keep track of which broadcast packets
have already been received and retransmitted. The list contains, for
each distinct broadcast packet received, the source IP address and
the IP ident value from the IP header of the broadcast packet.
When a node receives a packet broadcast to address 255.255.255.255,
it checks the source IP address and the IP ident value of the
broadcast packet's IP header. The node then checks to see whether
the broadcast packet has already been received in the past, and thus
whether it has already retransmitted the broadcast packet. If there
is no existing list entry containing the same IP source address and
IP ident value, the node retransmits the broadcast packet. If there
is such a list entry with matching source IP address and IP ident
field, the node silently discards the broadcast packet.
List entries SHOULD be kept for at least BROADCAST_RECORD_TIME
before the node expunges the record. BROADCAST_RECORD_TIME
is a configurable parameter, but it MUST be at least equal to
RREP_WAIT_TIME.
10. Quality of Service
AODV currently provides some minimal controls to enable mobile nodes AODV currently provides some minimal controls to enable mobile nodes
in an ad hoc network to specify, as part of a RREQ, certain Quality 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. of Service parameters that a route to a destination must satisfy.
In particular, a RREQ MAY include a Maximum Delay extension (see In particular, a RREQ MAY include a Maximum Delay extension (see
Section 12.4) or a Minimum Bandwidth extension (see Section 12.5). Section 14.4) or a Minimum Bandwidth extension (see Section 14.5).
If, after establishment of such a route, any node along the path If, after establishment of such a route, any node along the path
detects that the requested Quality of Service parameters can no detects that the requested Quality of Service parameters can no
longer be maintained, that node MUST originate a ICMP QOS_LOST longer be maintained, that node MUST originate a ICMP QOS_LOST
message back to the node which had originally requested the now message back to the node which had originally requested the now
unavailable parameters. unavailable parameters.
10. AODV and Aggregated Networks 11. AODV and Aggregated Networks
AODV has been designed for use by mobile nodes with IP addresses 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 that are not necessarily related to each other, to create an ad hoc
network. However, in some cases a collection of mobile nodes MAY network. However, in some cases a collection of mobile nodes MAY
operate in a fixed relationship to each other and share a common operate in a fixed relationship to each other and share a common
subnet prefix, moving together within an area where an ad hoc network subnet prefix, moving together within an area where an ad hoc network
has formed. Call such a collection of nodes a ``subnet''. In this 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 case, it is possible for a single node within the subnet to advertise
reachability for all other nodes on the subnet, by responding with reachability for all other nodes on the subnet, by responding with
a RREP message to any RREQ message requesting a route to any node a RREP message to any RREQ message requesting a route to any node
with the subnet routing prefix. Call the single node the ``subnet with the subnet routing prefix. Call the single node the ``subnet
router''. In order for a subnet router to operate the AODV protocol router''. In order for a subnet router to operate the AODV protocol
for the whole subnet, it has to maintain a destination sequence for the whole subnet, it has to maintain a destination sequence
number for the entire subnet. In any such RREP message sent by the 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 subnet router, the Prefix Length field of the RREP message MUST be
set to the length of the subnet prefix. Other nodes sharing the set to the length of the subnet prefix. Other nodes sharing the
subnet prefix SHOULD NOT issue RREP messages. subnet prefix SHOULD NOT issue RREP messages.
11. Using AODV with Other Networks 12. Using AODV with Other Networks
In some configurations, an ad hoc network may be able to provide In some configurations, an ad hoc network may be able to provide
connectivity between external routing domains that do not use connectivity between external routing domains that do not use
AODV. If the points of contact to the other networks can act as AODV. If the points of contact to the other networks can act as
subnet routers (see section 10) for any relevant networks within subnet routers (see Section 11) for any relevant networks within
the external routing domains, then the ad hoc network can maintain the external routing domains, then the ad hoc network can maintain
connectivity to the external routing domains. Indeed, the external connectivity to the external routing domains. Indeed, the external
routing networks can use the ad hoc network defined by AODV as a routing networks can use the ad hoc network defined by AODV as a
transit network. transit network.
In order to provide this feature, a point of contact to an external 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 network (call it an Infrastructure Router) has to act as the subnet
router'' for every subnet of interest within the external network router for every subnet of interest within the external network for
for which the Infrastructure Router can provide reachability. This which the Infrastructure Router can provide reachability. This
includes the need for maintaining a destination sequence number for includes the need for maintaining a destination sequence number for
that external subnet. that external subnet.
If multiple Infrastructure Routers offer reachability to the same If multiple Infrastructure Routers offer reachability to the same
external subnet, those Infrastructure Routers have to cooperate (by external subnet, those Infrastructure Routers have to cooperate (by
means outside the scope of this specification) to provide consistent means outside the scope of this specification) to provide consistent
AODV semantics for ad hoc access to those subnets. AODV semantics for ad hoc access to those subnets.
12. Extensions 13. Service Location with AODV
It is possible to use AODV's basic RREQ and RREP messages to locate
services within an ad hoc network. There are two extensions defined
for this purpose:
- Service Discovery
- Service Resolution
The basic operation of RREQ and RREP messages remains the same,
except that additional functionality is defined to distinguish
between the roles of IP path discovery and service location. The
time for which a path to an IP address remains valid is likely to
be relatively short, and to depend upon the mobility factor of the
mobile node. Aging out such paths, to protect against using stale
paths, is controlled by the timeout parameter ACTIVE_ROUTE_TIMEOUT.
The association between a service and an IP address, on the other
hand, is likely to remain valid for a much longer time. The timeout
parameter SERVICE_ASSOCIATION_TIMEOUT specifies how long a node may
continue to associate a particular service with a particular IP
address. So, for instance, the first time that a mobile node needs
access to a particular service, it will issue a RREQ with the `S' bit
set, and acquire a suitable path to the service. Subsequent attempts
to connect to the same service may be carried out by issuing a RREQ
with the `S' bit cleared, which then amount to the regular operation
of trying to establish a routing path to a known IP destination
address.
14. Extensions
RREQ, RREP, and MACT messages have extensions defined in this version RREQ, RREP, and MACT messages have extensions defined in this version
(and, possibly, future versions) of the protocol. Extensions have (and, possibly, future versions) of the protocol. Extensions have
the 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 ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 22, line 5 skipping to change at page 26, line 32
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.
12.1. Hello Interval Extension Format 14.1. Hello Interval Extension 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 | Hello Interval ... | Type | Length | Hello Interval ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Hello Interval, continued | ... Hello Interval, continued |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx Type xx
Length The length of the extension field. Length The length of the extension field.
Hello Interval Hello Interval
The number of milliseconds between successive The number of milliseconds between successive
transmissions of a ``hello'' message (RREP). transmissions of a Hello message.
The Hello Interval extension MAY be appended to a RREP message with 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 TTL == 1, to be used by a neighboring receiver in determine how long
to wait for subsequent such RREP messages. to wait for subsequent such RREP messages (i.e., Hello messages; see
section 6.7).
12.2. Multicast Group Leader Extension Format 14.2. Multicast Group Leader Extension Format
This extension is appended to a RREQ by a node wishing to repair a This extension is appended to a RREQ by a node wishing to repair a
multicast tree. multicast tree.
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 | Multicast Group Hop Count | | Type | Length | Multicast Group Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multicast Group Leader IP Address | | Multicast Group Leader IP Address |
skipping to change at page 23, line 7 skipping to change at page 27, line 39
the Multicast Group Leader. the Multicast Group Leader.
Multicast Group Leader IP Address Multicast Group Leader IP Address
The IP Address of the Multicast Group Leader. The IP Address of the Multicast Group Leader.
This extension is only used for rebuilding a multicast tree branch. This extension is only used for rebuilding a multicast tree branch.
In that case, a route to the Multicast Group Leader was known before 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 the need for the repair was discovered, and the IP address of the
group leader is placed in the extension field. group leader is placed in the extension field.
12.3. Multicast Group Information Extension Format 14.3. Multicast Group Information Extension Format
The following extension is used to carry additional information for The following extension is used to carry additional information for
the RREP message (see Section 5) when sent to establish a route to a the RREP message (see Section 5) when sent to establish a route to a
multicast destination. multicast destination.
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 | Multicast Group IP Address ... | Type | Length | Multicast Group Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Multicast Group IP Address | Multicast Group Seq Number ... | Multicast Group IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Multicast Group Seq Number | Multicast Group Ldr IP Addr .. | Multicast Group Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multicast Group Leader IP Address / Multicast Tree Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.. Multicast Group Ldr IP Addr |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx Type xx
Length The length of the extension field. Length The length of the extension field.
Multicast Group Hop Count
The distance of the node from the Multicast Group Leader.
Multicast Group IP Address Multicast Group IP Address
The IP Address of the Multicast Group. The IP Address of the Multicast Group.
Multicast Group Seq Number Multicast Group Sequence Number
The current sequence number of the Multicast Group. The current sequence number of the Multicast Group.
Multicast Group Ldr IP Addr Multicast Group Leader IP Address
The IP Address of the current Multicast Group Leader. The IP Address of the current Multicast Group Leader.
This extension is included when responding to a multicast group Multicast Tree Hop Count
RREQ. It is also used by a multicast group leader when sending a The number of hops the packet has travelled off of the
Group Hello. The extension fields indicate which group the node multicast tree.
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 This extension is included when responding to a multicast group RREQ.
In this case, the last field is used as the Multicast Group Leader IP
Address. The extension 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 last field is the Multicast Tree Hop
Count. This field is incremented once each time it is received by a
non-tree node.
14.4. Maximum Delay Extension 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 | Max Delay | | Type | Length | Max Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx Type xx
Length The length of the extension field. Length The length of the extension field.
skipping to change at page 24, line 31 skipping to change at page 29, line 31
node in order to place a maximum bound on the acceptable time node in order to place a maximum bound on the acceptable time
delay experienced on any acceptable path from the source to the delay experienced on any acceptable path from the source to the
destination. destination.
Before forwarding the RREQ, an intermediate node MUST compare its Before forwarding the RREQ, an intermediate node MUST compare its
NODE_TRAVERSAL_TIME to the (remaining) Max Delay indicated in the NODE_TRAVERSAL_TIME to the (remaining) Max Delay indicated in the
Maximum Delay Extension. If the Max Delay is less, the node MUST Maximum Delay Extension. If the Max Delay is less, the node MUST
discard the RREQ and not process it any further. Otherwise, the discard the RREQ and not process it any further. Otherwise, the
node subtracts NODE_TRAVERSAL_TIME from the Max Delay value in node subtracts NODE_TRAVERSAL_TIME from the Max Delay value in
the extension and continues processing the RREQ as specified in the extension and continues processing the RREQ as specified in
Section 6.3. Section 6.4.
12.5. Minimum Bandwidth Extension Format 14.5. Minimum Bandwidth Extension 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 | Minimum Bandwidth ... | Type | Length | Minimum Bandwidth ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Minimum Bandwidth | ... Minimum Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type xx Type xx
skipping to change at page 25, line 15 skipping to change at page 30, line 15
The Minimum Bandwidth Extension can be appended to a RREQ by a The Minimum Bandwidth Extension can be appended to a RREQ by a
requesting node in order to specify the minimal amount of bandwidth requesting node in order to specify the minimal amount of bandwidth
that must be made available along acceptable path from the source to that must be made available along acceptable path from the source to
the destination. the destination.
Before forwarding the RREQ, an intermediate node MUST compare its Before forwarding the RREQ, an intermediate node MUST compare its
available link capacity to the Minimum Bandwidth indicated in the available link capacity to the Minimum Bandwidth indicated in the
extension. If the requested amount of bandwidth is not available, extension. If the requested amount of bandwidth is not available,
the node MUST discard the RREQ and not process it any further. the node MUST discard the RREQ and not process it any further.
Otherwise, the node continues processing the RREQ as specified in Otherwise, the node continues processing the RREQ as specified in
Section 6.3. Section 6.4.
13. Configuration Parameters 14.6. Service Resolution Extension Format
This section gives default values for some important values 0 1 2 3
associated with AODV protocol operations. A particular 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
mobile node may wish to change certain of the parameters, in +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
particular the NET_DIAMETER, MY_ROUTE_TIMEOUT, MY_TRAVERSAL_TIME, | Type | Length | Protocol |
ALLOWED_HELLO_LOSS, RREQ_RETRIES, and possibly the HELLO_INTERVAL. In +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
the latter case, the node should advertise the HELLO_INTERVAL in its | Port |
``hello'' messages, by appending a Hello Interval Extension to the +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
RREP message.
ACTIVE_ROUTE_TIMEOUT 3000 Type xx
ALLOWED_HELLO_LOSS 2 Length The length of the extension field.
BAD_LINK_LIFETIME 2 * RREP_WAIT_TIME Protocol
Either 6, to indicate TCP, or 17, to indicate UDP.
Support for other protocols are remains undefined.
BCAST_ID_SAVE 30000 Port The port number at which service applications await
application protocol messages sent over TCP or UDP,
as indicated by the ``Protocol'' field.
GROUP_HELLO_INTERVAL 5000 The Service Discoveery Extension Format can be appended to a RREQ by
a requesting node in order to discover the IP address, and a route to
that address, at which a service application is available.
HELLO_INTERVAL 1000 Note that a service is likely to remain in operation at a particular
IP address for a time (SERVICE_RESIDENCE_TIME) that is much longer
than the amount of time that the route to that IP address will remain
available.
MTREE_BUILD 2 * REV_ROUTE_LIFE 15. Configuration Parameters
NET_DIAMETER 35 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, 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. Choice of these
parameters may affect the performance of the protocol.
Parameter Name Value
---------------------- -----
ACTIVE_ROUTE_TIMEOUT 3,000
ALLOWED_HELLO_LOSS 2
BAD_LINK_LIFETIME 2 * RREP_WAIT_TIME
BCAST_ID_SAVE 30,000
BROADCAST_RECORD_TIME RREP_WAIT_TIME
GROUP_HELLO_INTERVAL 5,000
HELLO_INTERVAL 1,000
MTREE_BUILD 2 * REV_ROUTE_LIFE
MY_ROUTE_TIMEOUT 2 * ACTIVE_ROUTE_TIMEOUT
NET_DIAMETER 35
NEXT_HOP_WAIT NODE_TRAVERSAL_TIME + 10 NEXT_HOP_WAIT NODE_TRAVERSAL_TIME + 10
NODE_TRAVERSAL_TIME 40 NODE_TRAVERSAL_TIME 40
MY_TRAVERSAL_TIME NODE_TRAVERSAL_TIME
MY_ROUTE_TIMEOUT 6000
REV_ROUTE_LIFE RREP_WAIT_TIME REV_ROUTE_LIFE RREP_WAIT_TIME
RREP_WAIT_TIME 3 * NODE_TRAVERSAL_TIME * NET_DIAMETER / 2 RREP_WAIT_TIME 3 * NODE_TRAVERSAL_TIME * NET_DIAMETER / 2
RREQ_RETRIES 2 RREQ_RETRIES 2
SERVICE_ADDR_TIMEOUT 300,000
TTL_START 1
TTL_INCREMENT 2
TTL_THRESHOLD 7
Note that the network may contain more than NET_DIAMETER ** 2 nodes. NET_DIAMETER measures the maximum possible number of hops between
NET_DIAMETER measures the number of ``cells'' (typically wireless) two nodes in the network. NODE_TRAVERSAL_TIME is a conservative
that would have to be placed end to end in order to stretch across estimate of the average one hop traversal time for packets and should
the network at its widest point. include queueing delays, interrupt processing times and tranfer
times. ACTIVE_ROUTE_TIMEOUT SHOULD be set to a longer value (at
least 10,000 milliseconds) if link-layer indications are used to
detect link breakages such as in IEEE 802.11 standard. TTL_START
should be set to at least 2 if hello messages are used for local
connectivity information. Performance of the AODV protocol is
sensitive to the chosen values of these constants, which often depend
on the characteristics of the underlying link layer protocol, radio
technologies etc.
14. Security Considerations 16. 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 line 1283 skipping to change at page 33, line 35
+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
Samir R. Das
Division of Computer Science
University of Texas at San Antonio
San Antonio, TX 78249
+1 210-458-5537
+1 210-458-4437 (fax)
samir@cs.utsa.edu
 End of changes. 

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