Duplicate address detection and autoconfiguration in OLSR Saadi Boudjit; Cedric Adjih; Anis Laouiti; Paul Muhlethaler Hipercom Project National Institute

Duplicate address detection and autoconfiguration in OLSR

Saadi Boudjit; Cedric Adjih; Anis Laouiti; Paul Muhlethaler

Hipercom ProjectNational Institute in Computer science and Control

INRIA - France

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Outline OLSR Overview

Autoconfiguration

AutoConfiguration in IPv6

AutoConfiguration in Ad Hoc networks

DAD-MPR flooding algorithm and Autoconfiguration in OLSR

Conclusion

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OLSR Overview

OLSR: Proactive MPR flooding Among the 1-hop neighbors of node m, only a

subset of nodes are selected as MPRs and hence retransmit the messages of m.

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OLSR Overview

Recently: RFC 3626 (IETF/MANET) Link State protocol

- Periodic messages

- Neighbor sensing:“HELLO” messages: list of neighbors

- Topology discovery (Topology Control):List of neighbors sent to the whole net (in “TC” messages)

- Routes: Computed to all nodes Routes computed independently of traffic

- OLSR Gateways: Host and Network Association “HNA” messages

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AutoConfiguration

What is the autoconfiguration ?

Automatic assignment of parameters which are necessary to a node to join a network (IP address for example);

But also automatic reassignment of network parameters in case of conflict.

Why ad hoc networks need autoconfiguration ?

Manual configuration is impractical in large scale Manets;

User-friendliness is necessary for new emerging applications like wireless internet.

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AutoConfiguration in IPv6

Automatic configuration

Two methods :

Stateless Address Autoconfiguration Periodic broadcast of the network related information by the Router;

Stateful Address Autoconfiguration Hosts rely on a DHCP server to acquire the network related information,

necessary to its configuration;

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Stateless AutoConfiguration

IPv6 RouterIPv6 Address 2001:0660:1000::ID4 IPv6 Address 2001:0660:1000::ID2

IPv6 Address 2001:0660:1000::ID3

MAC address MAC1

IPV6 LAN

Link-local Address fe80::ID1

“Neighbor Advertisement” Message MAC address MAC5Link-local Address fe80::ID5

“Neighbor Sollicitation” Message

Unique Address …

“Neighbor Sollicitation “ Message

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Stateless AutoConfiguration


IPv6 Address 2001:0660:1000::ID3

MAC address MAC1

IPV6 LAN

Link-local Address fe80::ID1

“Router Sollicitation” Message ff02::2

“Router Advertisement” MessageBit MPrefix 2001:0660:1000

IPv6 global unicast address 2001:0660:1000::ID1

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Stateful AutoConfiguration

DHCP ServerIPv6 Address 2001:0660:1000::ID

IPv6 Address 2001:0660:1000::ID3


MAC address MAC1

IPV6 LAN

Link-local Address fe80::ID1unique address…

DHCP Client

“DHCP Sollicitation” Message ff02::1:2

“DHCP Advertisement” Message containing its IPv6 address

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Stateful AutoConfiguration

DHCP ServerIPv6 Address 2001:0660:1000::ID

IPv6 address 2001:0660:1000::ID3

IPv6 RouterIPv6 Address 2001:0660:1000::ID4 IPv6 address 2001:0660:1000::ID2

MAC address MAC1

IPV6 LAN

Link-local address fe80::ID1Unique address…

DHCP client

“DHCP request” Message, address extension

“DHCP response” Message, extension=2001:0660:1000::

IPv6 global unicast address 2001:0660:1000::ID1

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More difficult in MANET environment than that in hardwired networks due to:

Instability of mobile nodes;

Openness of Ad Hoc networks;

Absence of a central administration.

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MANET

A

B

Scenario 1 : A mobile node joins and then leaves a MANET once.

- An unused IP address is allocated to a node on it’s arrival and becomes free on it’s departure.

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Scenario 2 : Network partitions and merges


Partition 2

APartition 1

A

B

(a) (b)

Partition 1

Partition 2

- If one or more configured nodes go out of others’ transmission range The network becomes partitioned;

- When these nodes approach each other, the partitions merge later Possibility of address conflict.

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Scenario 3 : Merger of two independent MANETS

A

MANET 1

B

MANET 2

- There may be some duplicate addresses in both of them Some(or all) nodes in one MANET may need to change their addresses.

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Solutions :

Several solutions have been proposed, which can be divided into the following three categories:

(1) Conflict-detection allocation algorithms;

(2) Conflict-free allocation algorithms;

(3) Best-effort allocation algorithms.


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Principle :

1- A new node chooses an IP address tentatively, and requests for approval from all the configured nodes in the network;

2- If the conflict is found by veto from a node with the same IP address, the procedure is repeated until there is no duplicate address.

Illustration: OLSR for IPv6 Networks

Saadi Boudjit, Pascale Minet, Cedric Adjih, Anis Laouiti

HIPERCOM Project, INRIA, France

1- Conflict-detection allocation

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Principle :

1- A node taking part in allocation assigns an unused IP address to a new node;

2- This is achieved by the assumption that the nodes taking part in allocation have disjoint address pools. Thus they could be sure that the allocated addresses are different.

3- Every time when a mobile node joins, an address pool is divided into halves between it and a configured node.

Illustration: DCDP(Dynamic Configuration and Distribution Protocol)

Sajal K.Das - University of Texas (USA) Archan Misra, Subir Das, Anthony Mc Auley – Telcordia

Technologies(USA)

2- Conflict-free allocation

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Principle :

1- The nodes responsible for allocation try to assign an unused IP address to a new node as far as they know The same free IP address in the global address pool could be assigned to two or more new nodes arriving at almost the same time ;

2- The new node uses conflict detection to guarantee that it is a free IP address;

Illustration: DDHCP(Distributed Dynamic Host Configuration Protocol)

Sanket Nesargi, Ravi Prakash

3- Best-effort allocation

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4- Summary of DAD algorithms

Best-effort allocation algorithms

Conflict-detection allocation algorithms

Conflict-free allocation algorithms

Passive DAD algorithmsActive DAD algorithms

Distribute additional control information in the network to prevent address duplication

Continuously monitor routing protocol control traffic to detect address duplicates

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Our autoconfiguration mechanism is divided into two parts:

1- Initial address assignment (2 ways) The arriving node can perform a random selection in a well

known pool of addresses;

One of the neighbors selects the address on behalf of the arriving node.

2- Duplicate Address Detection “Proactive DAD”: Periodic broadcast of MAD messages;

MAD messages must reach all the nodes in the network.

AutoConfiguration in OLSR

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HELLO

HELLO

HELLO

HELLO

HELLO

1- Initial address assignment

Temporary address

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MAD

DR

UNIQUE ADDRESS CONFIRMATION

MAD

MAD

1- Initial address assignment

Unique address

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2- Proactive DAD

After a node being configured, it must periodically broadcast MAD(Multiple Address Declaration) messages containing:

An identifier of the node (Node ID);

The list of interface addresses of the node on which OLSR is running;

In order to perform DAD when a merge of two previously disconnected MANETs occur.

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MAD

MADMAD

MAD

MAD

MAD

2- Proactive DAD

A configured node

MAD messages will reach all the nodes in the network

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A node detects and address conflict if:

It receives a MAD message having the same address as its own, but with a different identifier.

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Possibilities for MAD diffusion:

Pure flooding Drawbacks:

Not using the optimizations of the underlying routing protocol; High bandwidth consumption

MPR flooding Drawbacks:

MPR calculation is based on the assumption that there is no address duplication in the neighborhood of a node.

Therefore, OLSR relaying optimization rules may not be sufficient to ensure diffusion in some conflictual cases.

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Illustration:

• Two conflicting nodes X1 and X2 in the 2-hop neighbors of node I;

• Node I could not calculate its MPR set correctly;

• MAD messages of X1 and X2 can not be propagated throughout the entire network;

• Consequently, nodes X1 and X2 will not detect the address conflict.

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New rules are added to the classical MPR flooding algorithm for MAD message diffusion;

The set is called DAD-MPR flooding, for Duplicate Address Detecting MPR flooding;

In the absence of packet loss, the DAD-MPR flooding algorithm will allow a MAD message to reach all the nodes in the network.

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DAD-MPR flooding algorithm

Rules added to the classical MPR flooding algorithm:Rule1: The MAD duplicate message detection will be based on the

node originator address, the message sequence number, plus the node identifier;

Rule2: If a given node N receives a MAD message from a neighbor M,

it will repeat this message if one of its 1-hop neighbors has the same address as the one contained in the MAD message.

In this case the MAD TTL value must be set to 1 to avoid the transmission of the MAD message beyond the conflicting nodes;

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Proof of correctness

• We assume that there are only two nodes in conflict ,A1 and A2, in the network and they are d hops away from each other;

• We denote by Ni the set of nodes which are exactly at distance i of A1 and d-i of A2 for i є {1, …, d-1};

• Those sets contain nodes that are precisely on a shortest path from A1 to A2;

• Hence several cases can occur, depending on on the distance d,

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• distance d = 1 , 2

• Nodes A1 and A2 are in the radio range of each other, the conflict will be detected by both nodes;

• Node B detects the conflict and by applying the Rule2, the nodes A1 and A2 will receive the MAD messages of each other;

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• distance d = 3

• Nodes A1 and A2 calculate their MPR set correctly. A1 chooses B as an MPR to reach node C, and A2 chooses C as MPR to reach B;

• Nodes B and C don’t choose each other as MPR, consequently, A1 MAD messages will never reach A2, and A2 MAD messages will never reach A1;

• Node B detects that one of its 1-hop neighbors, A1, has the same address as the one contained in the MAD message originating from node A2 using Rule2, node B relay the MAD message of A2 to reach A1;

• By the same manner, MAD messages of A1 will reach A2 and the conflict will be detected;

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• distance d = 4

• Nodes A1 and A2 don’t have duplications in their 1-hop and 2-hop neighbors, they calculate their MPR set properly;

• Nodes B and D don’t have duplications in their 1-hop and 2-hop neighbors, they calculate their MPR set properly;

• The MAD messages of A1 and A2 will reach all the intermediary nodes B, C, and D;

• Node C looks to the nodes A1 and A2 as a single node, say A C chooses only one node between B and D as an MPR to cover A;

• Therefore, we are sure that one of the two nodes (A1 and A2) receives the MAD messages generated by the other node and then detects the conflict.

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• distance d ≥ 5

• Nodes A1 and A2 and all the intermediary nodes don’t have duplications in their 1-hop and 2-hop neighbors;

• Hence all the intermediary nodes calculate their MPR set correctly;

• Using the classical MPR flooding algorithm, the MAD messages of A1 and A2 will be correctly propagated to the nodes A2 and A1 respectively;

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Conclusion

- Proposed:- changes to the classical MPR flooding algorithm- Duplicate address detection algorithm

- relies on two procedures - very well integrated with OLSR - originality: proactive DAD - low complexity- Future work includes the adoption of: - Refinements for address conflict resolution - Handling the case of multiple conflicts - Taking into account the case of nodes with multiple

interfaces - Considering implementation issues in more details

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Questions ...............................??????

Documents

Duplicate address detection and autoconfiguration in OLSR Saadi Boudjit; Cedric Adjih; Anis Laouiti; Paul Muhlethaler Hipercom Project National Institute