Duplicate address detection and autoconfiguration in OLSR Saadi

Duplicate address detection and autoconfiguration in OLSR Saadi Boudjit; Cedric Adjih; Anis Laouiti; Paul Muhlethaler Hipercom Project National Institute in Computer science and Control INRIA - France June 30 2004 DFSG SDGHIPERCOM

Outline n OLSR Overview n Autoconfiguration n Auto. Configuration in IPv 6 n Auto. Configuration in Ad Hoc networks n DAD-MPR flooding algorithm and Autoconfiguration in OLSR n Conclusion 2

OLSR Overview n n 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. 3

OLSR Overview n n 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: n n Computed to all nodes Routes computed independently of traffic - OLSR Gateways: Host and Network Association “HNA” messages 4

Auto. Configuration n What is the autoconfiguration ? n n n 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 ? n Manual configuration is impractical in large scale Manets; n User-friendliness is necessary for new emerging applications like wireless internet. 5

Auto. Configuration in IPv 6 n Automatic configuration Two methods : n n 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; 6

Stateless Auto. Configuration IPv 6 Router IPv 6 Address 2001: 0660: 1000: : ID 4 IPv 6 Address 2001: 0660: 1000: : ID 2 “Neighbor Advertisement” Message IPV 6 LAN MAC address MAC 5 Link-local Address fe 80: : ID 5 “Neighbor Sollicitation” Message IPv 6 Address 2001: 0660: 1000: : ID 3 “Neighbor Sollicitation “ Message MAC address MAC 1 Link-local Address fe 80: : ID 1 Unique Address … 7

Stateless Auto. Configuration IPv 6 Router IPv 6 Address 2001: 0660: 1000: : ID 4 IPv 6 Address 2001: 0660: 1000: : ID 2 “Router Advertisement” Message Bit M Prefix 2001: 0660: 1000 IPV 6 LAN “Router Sollicitation” Message ff 02: : 2 IPv 6 Address 2001: 0660: 1000: : ID 3 MAC address MAC 1 Link-local Address fe 80: : ID 1 IPv 6 global unicast address 2001: 0660: 1000: : ID 1 8

Stateful Auto. Configuration IPv 6 Router IPv 6 Address 2001: 0660: 1000: : ID 4 IPv 6 Address 2001: 0660: 1000: : ID 2 DHCP Server IPv 6 Address 2001: 0660: 1000: : ID IPV 6 LAN “DHCP Advertisement” Message containing its IPv 6 address IPv 6 Address 2001: 0660: 1000: : ID 3 “DHCP Sollicitation” Message ff 02: : 1: 2 DHCP Client MAC address MAC 1 Link-local Address fe 80: : ID 1 unique address… 9

Stateful Auto. Configuration IPv 6 Router IPv 6 Address 2001: 0660: 1000: : ID 4 IPv 6 address 2001: 0660: 1000: : ID 2 DHCP Server IPv 6 Address 2001: 0660: 1000: : ID IPV 6 LAN “DHCP response” Message, extension=2001: 0660: 1000: : IPv 6 address 2001: 0660: 1000: : ID 3 “DHCP request” Message, address extension DHCP client MAC address MAC 1 Link-local address fe 80: : ID 1 Unique address… IPv 6 global unicast address 2001: 0660: 1000: : ID 1 10

Auto. Configuration in Ad Hoc networks More difficult in MANET environment than that in hardwired networks due to: n Instability of mobile nodes; n Openness of Ad Hoc networks; n Absence of a central administration. 11

Auto. Configuration in Ad Hoc networks Scenario 1 : A mobile node joins and then leaves a MANET once. A B MANET - An unused IP address is allocated to a node on it’s arrival and becomes free on it’s departure. 12

Auto. Configuration in Ad Hoc networks Scenario 2 : Network partitions and merges B Partition 2 A A Partition 1 (a) (b) - 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. 13

Auto. Configuration in Ad Hoc networks Scenario 3 : Merger of two independent MANETS A B MANET 1 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. 14

Auto. Configuration in Ad Hoc networks 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. 15

1 - Conflict-detection allocation 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 IPv 6 Networks Saadi Boudjit, Pascale Minet, Cedric Adjih, Anis Laouiti HIPERCOM Project, INRIA, France 16

2 - Conflict-free allocation 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) 17

3 - Best-effort allocation 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 18

4 - Summary of DAD algorithms Conflict-free allocation algorithms Conflict-detection allocation algorithms Best-effort allocation algorithms Active DAD algorithms Passive DAD algorithms Distribute additional control information in the network to prevent address duplication Continuously monitor routing protocol control traffic to detect address duplicates 19

Auto. Configuration in OLSR Our autoconfiguration mechanism is divided into two parts: 1 - Initial address assignment (2 ways) n n 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”: n Periodic broadcast of MAD messages; n MAD messages must reach all the nodes in the network. 20

Auto. Configuration in OLSR 1 - Initial address assignment HELLO HELLO Temporary address 21

Auto. Configuration in OLSR 1 - Initial address assignment DR MAD MAD UNIQUE ADDRESS CONFIRMATION Unique address 22

Auto. Configuration in OLSR 2 - Proactive DAD After a node being configured, it must periodically broadcast MAD(Multiple Address Declaration) messages containing: n An identifier of the node (Node ID); n 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. 23

Auto. Configuration in OLSR 2 - Proactive DAD MAD MAD MAD A configured node MAD messages will reach all the nodes in the network 24

Auto. Configuration in OLSR A node detects and address conflict if: n It receives a MAD message having the same address as its own, but with a different identifier. 25

Auto. Configuration in OLSR Possibilities for MAD diffusion: n Pure flooding n Drawbacks: n n n Not using the optimizations of the underlying routing protocol; High bandwidth consumption MPR flooding n Drawbacks: n n 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. 26

Auto. Configuration in OLSR Illustration: • Two conflicting nodes X 1 and X 2 in the 2 -hop neighbors of node I; • Node I could not calculate its MPR set correctly; • MAD messages of X 1 and X 2 can not be propagated throughout the entire network; • Consequently, nodes X 1 and X 2 will not detect the address conflict. 27

Auto. Configuration in OLSR n n n 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. 28

DAD-MPR flooding algorithm Rules added to the classical MPR flooding algorithm: Rule 1: n The MAD duplicate message detection will be based on the node originator address, the message sequence number, plus the node identifier; Rule 2: n 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. n In this case the MAD TTL value must be set to 1 to avoid the transmission of the MAD message beyond the conflicting nodes; 29

Proof of correctness • We assume that there are only two nodes in conflict , A 1 and A 2, 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 A 1 and d-i of A 2 for i є {1, …, d-1}; • Those sets contain nodes that are precisely on a shortest path from A 1 to A 2; • Hence several cases can occur, depending on on the distance d, 30

Proof of correctness • distance d = 1 , 2 • Nodes A 1 and A 2 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 Rule 2, the nodes A 1 and A 2 will receive the MAD messages of each other; 31

Proof of correctness • distance d = 3 • Nodes A 1 and A 2 calculate their MPR set correctly. A 1 chooses B as an MPR to reach node C, and A 2 chooses C as MPR to reach B; • Nodes B and C don’t choose each other as MPR, consequently, A 1 MAD messages will never reach A 2, and A 2 MAD messages will never reach A 1; • Node B detects that one of its 1 -hop neighbors, A 1, has the same address as the one contained in the MAD message originating from node A 2 using Rule 2, node B relay the MAD message of A 2 to reach A 1; • By the same manner, MAD messages of A 1 will reach A 2 and the conflict will be detected; 32

Proof of correctness • distance d = 4 • Nodes A 1 and A 2 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 A 1 and A 2 will reach all the intermediary nodes B, C, and D; • Node C looks to the nodes A 1 and A 2 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 (A 1 and A 2) receives the MAD messages generated by the other node and then detects the conflict. 33

Proof of correctness • distance d ≥ 5 • Nodes A 1 and A 2 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 A 1 and A 2 will be correctly propagated to the nodes A 2 and A 1 respectively; 34

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 35

Questions. . . . ? ? ? 36