1 Reliable Multicast Protocols for MANET Reporter : 吳政鴻 Date : 2005/5/17

2 Outline An Overview of MANET An Overview of Reliable Multicast Protocol Automatic Retransmission reQuest Based Reliable Multicast Protocols (ARQ-Based) –Reliable Multicast Algorithm (RMA) –Reliable Adaptive Light Weight Multicast Transport protocol (RALM) –Reliable, Adaptive, Congestion-Controlled Adhoc Multicast Transport Protocol (ReAct)

3 Gossip-Based Reliable Multicast Protocols –Anonymous Gossip (AG) –Route Driven Gossip (RDG) Forward Error Correction (FEC) Based Reliable Multicast Protocols –Reliable Multicast Data Distribution Protocol (RMDP) Comparisons Conclusions

4 An Overview of MANET Definition Characteristics Limitations

5 Definition Mobile ad hoc network(MANET), or simply ad hoc network, comprises nodes that freely and dynamically self-organize into arbitrary and temporary network topology without any infrastructure support. (Chlamtac,Conti,andLiu,2003) Nodes are communication devices comprise of laptop computer, PDA, mobile phone and etc. Nodes formanet work to communicate with each other. Networking infrastructure refers to the facility of which the sole purpose is to carry the data generated by each node to the respective destination node

6 Characteristics Infrastructure-less or with minimum infrastructure support Self-organizing and self-managing Multi-hop

7 Infrastructure-less or with minimum infrastructure support A Pure ad hoc network does not have, or simply does not rely on infrastructure support (for routing, network management, and etc.) A hybrid ad hoc network consists of both client nodes and infrastructure nodes,i.e. nodes whose function is merely transporting traffic for the client nodes Hybrid networks are more common

8 Self-organizing and self- managing Since network infrastructure is not available, the nodes must organize and maintain the network by themselves

9 Multi-hop Since each node can route traffic for the others, multi-hopping is possible. Single hop ad hoc network does not form a large scale network

10 Limitations Ad hoc network is not a one size fit all measure. Its current limitations are listed below: –Killer application has not turned up –Acceptance by users is unclear –Delay caused by multi-hopping –Quality of service is difficult to be guaranteed –Prone to security threat

11 An Overview of Reliable Multicast Protocol What is Multicast Communication? What is Reliable Multicast? What is Reliable Multicast use in MANET? Three categories according to the recovery mechanisms being used

12 What is Multicast Communication? Group communication mechanism – Provides one-to-many and many-to-many communication Efficient dissemination of messages – Network-based duplication (when needed) – Multicast retransmissions – Bandwidth savings – Parallel delivery at multiple locations

13 IP Multicast Communication

14 Example IP Multicast Use (Access Grid )

15 What is Reliable Multicast? Properties similar to TCP Application-level program Uses IP Multicast as the underlying communication mechanism Reliable and ordered delivery of messages within a group Tracks group membership IETF Reliable Multicast Transport Working Group is defining standardized building blocks

16 Example Reliable Multicast Use (Remote Instrument Access)

17 What is Reliable Multicast use in MANET ? Reliable multicast becomes a very challenging research problem due to high packet loss rate pertained to MANET Reliable multicast solutions proposed for wired network can not be directly ported for MANET –link breakages –route changes –concentrated retransmissions –concentrated retransmissions and heavy overhead

18 Three categories according to the recovery mechanisms being used Automatic Retransmission Request (ARQ)- based –Lost packets are retransmitted by the sources until they are recovered at all the receivers gossip-based –multicast packets are repeatedly transmitted for a few times by a few of the multicast members in a peer-to- peer fashion Forward Error Correction (FEC)-based –embed redundant data (e.g., erasure code) in each packet before transmitting.

19 Automatic Retransmission reQuest Based Reliable Multicast Protocols (ARQ-Based) –Reliable Multicast Algorithm (RMA) –Reliable Adaptive Light Weight Multicast Transport protocol (RALM) –Reliable, Adaptive, Congestion-Controlled Adhoc Multicast Transport Protocol (ReAct)

20 Reliable Multicast Algorithm (RMA) Assumption Protocol description Advantage versus Disadvantage

21 Assumption RMA is a multicast protocol supporting reliable transmission via acknowledgement from receivers and retransmissions from the sources RMA assumes that the sources have the full knowledge of group membership via JOIN or ACK messages

22 Protocol description RMA works in two phases: –multicast –retransmission Two types of multicast messages to the group member –MKNOWN unicast –MUNKNOWN broadcast

23 Source waits for MACKs for a period of time after the messages being sent out If the source is not able to collect all the MACKs from all the group members, the source enters the retransmission phase and sends a MUNKNOWN message with a flag in RETRANSMIT field Receiver could broadcast MACK to the source (BMACK), if a return path is not valid

24 Hello Message

25 MKNOWN Message

26 MUKNOWN Message

27 MACK Message

28 BMACK Message

29 Advantage versus Disadvantage Advantage –The sender guarantees retransmissions of lost packets –less message forwarding and less bandwidth usage Disadvantage –all the receivers must send ACKs back to the sender == >> Feedback implosion

30 Reliable Adaptive Light Weight Multicast Transport protocol (RALM) Assumption Protocol description Advantage versus Disadvantage

31 Assumption RALM assumes that the group membership is known to the sources This enables the sources to maintain a Receiver List

32 Protocol description Source selects a node from the receiver list as a feedback receiver in a round- robin fashion and notifies it together with the data packets The feedback receiver is responsible for replying ACK or NACK to the source until it collects all data packets

33 If Source receives a NACK, it enters the retransmission phase by slowing down the transmission rate first and retransmits the lost packets to the group until ACK to the lost packets are received and the current feedback receiver successfully obtains all the packets

34 This single-node feedback approach is effective when packet losses are due to congestion at a bottleneck link

35 ARec B C AFee BRec C B C A B C Receiver List A D BFee CRec D

36

37

38 Advantage versus Disadvantage Advantage –RALM also reduces control overhead by requiring one receiver at a time –Effectively reduces the burden at the sender in receiving and processing the feedbacks and reduces congestion around the sender == >> Solve Feedback implosion Disadvantage –RALM works well for static MANET

39 Reliable, Adaptive, Congestion-Controlled Adhoc Multicast Transport Protocol (ReAct) Assumption Protocol description Advantage versus Disadvantage

40 Assumption source-oriented component works the same as RALM

41 Protocol description ReAct adds a new recovery mechanism “local recovery” to RALM Local recovery occurs right after the receiver detects a lost packet the receiver requests one of the upstream group members (recovery node) starting from the closest one

42 The recovery node responses with the expect packets if it has them or it rejects the request Upon receiving the rejection, the receiver will retry recovery by choosing a farther away upstream node as a recovery node Only after several failures of the local requests, the receiver sends a NACK to the source for retransmission

43 C A B Packet Loss

44 Advantage versus Disadvantage Advantage –Local recover gets missing packets faster than source-oriented retransmission, reduces the burden/congestion at the source, and alleviates potential feedback implosion problem Disadvantage –when local recovery frequently fails and source recovery is triggered all the time

45 Gossip-Based Reliable Multicast Protocols –Anonymous Gossip (AG) –Route Driven Gossip (RDG)

46 Anonymous Gossip (AG) Assumption Protocol description Advantage versus Disadvantage

47 Assumption Implements gossip-based recovery on top of a multicast operation Gossip-messages only contain sequence numbers for missing packets Routing information of MAODV at receiver side is adopted for sending gossips

48 Protocol description AG works in two phases: –multicast Source sends multicast packets in best-effort –Recovery runs at background for recovering lost packets a group member periodically transmits a gossip request message about missing and successfully received packets to a pseudo-randomly selected neighbor node

49 If receiver receiving the gossip request –non-group-member neighbor simply forwards the packet to one of its neighbors –Group-member neighbor will accept and reply the gossip message with a certain probability This procedure ends until a node replies the gossip message or the lifetime of the message expires.

50 Works in background with multicast protocol. Members “ gossip ” randomly with other members to recover lost messages. Probabilistic reliability guarantees. Multicast Protocol Classical Gossip + Probabilistic Reliability =

51 Classical Gossip S D

52 Anonymous Gossip S D

53 Informed Gossip S D

54 Advantage versus Disadvantage Advantage –AG is a reliable multicast protocol that does not require membership information. –To reduce the network traffic, gossip requests are sent to nearer members with higher probability than to farther members. –AG operates independent of topology changes Disadvantage –AG can not guarantee the missing packets will be answered eventually

55 Route Driven Gossip (RDG) Assumption Protocol description Advantage versus Disadvantage

56 Assumption RDG does not use full multicast membership information, but partial knowledge RDG builds on top of a MANET unicast routing protocol DSR

57 Protocol description each existing member will only reply to the solicitation with a probability, resulting in a partial membership view at the joining node A gossip message generated at each session contains both new data packets and packet IDs of missing packets The gossip message is sent to F (fan out parameter) other group members randomly picked up from its partial member view

58 each new data packet will be gossiped for a few number of times (quiescence threshold) to ensure its spreading

59 Data packets, digests of missing packets, view Data Structures Identifier Group identifier View active passive remove Data buffer new old J OIN RECEIVE GR EQUEST G OSSIP RECEIVE G OSSIP L EAVE fanout F quiescence threshold τ q Push Pull

60 15  9,  5, 3 9  10,  2, 8 All members receive the message. 9  3, 5 5  1,  1,  10, 15 2  1, 8

61 Advantage versus Disadvantage Advantage –RDG eliminates burdens at sources for handling retransmission; instead, every group member participates in loss recovery –The performance of the protocol can be turned through the parameters fan out and quiescence threshold Disadvantage –RDG can not guarantee reliable delivery of all the packets

62 Forward Error Correction (FEC) Based Reliable Multicast Protocols –Reliable Multicast Data Distribution Protocol (RMDP)

63 Reliable Multicast Data Distribution Protocol (RMDP) Assumption Protocol description Advantage versus Disadvantage

64 Assumption FEC transmits redundant data with the original data transmission the k packets will be encoded in to n (n > k) packets. The n packets include redundant information

65 Protocol description RMDP is a hybrid FEC+ARQ protocol for reliable distribution of bulk data receivers After it receives k different packets, it decodes for the original source data The source adjusts its sending pointer to the packet where the largest number of packets is requested by different receivers

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67 Advantage versus Disadvantage Advantage –FEC technique helps RMDP to tolerant packet losses and to recover from losses with less feedback packets to the sources ==>> Solve Feedback implosion –when errors or packet losses happen at the receiver, original data can be reconstructed using the ones received Disadvantage –RMDP incurs long packet latency because a receiver has to wait for the reception of k packets before it can decode and delivery them to applications –Using the redundant data to increase packet length

68 Comparisons

69 Conclusions classification based on the recovery mechanisms The analyses and comparisons will help in choosing a suitable reliable multicast protocol for specific network conditions

70 REFERENCES Beini Ouyang and Xiaoyan Hong, Yunjung Yi, A Comparison of Reliable Multicast Protocols for Mobile Ad Hoc Networks, IEEE, Thiagaraja Gopalsamy, Mukesh Singhal, D. Panda and P. Sadayappan, A Reliable Multicast Algorithm for Mobile Ad hoc Networks, IEEE, Ken Tang, Katia Obraczka, Sung-Ju Lee, Mario Gerla, Reliable Adaptive Lightweight Multicast Protocol, IEEE, Ken Tang, Katia Obraczka, Sung-Ju Lee, Mario Gerla, A Reliable, Congestion-Controlled Multicast Transport Protocol in Multimedia Multi-hop Network, IEEE, 2002.

71 Ranveer Chandra, Venugopalan Ramasubramanian, Kenneth P. Birman, Anonymous Gossip: Improving Multicast Reliability in Mobile Ad-Hoc Networks, IEEE, Jun Luo, Patrick Th. Eugster, Jean-Pierre Hubaux, Route Driven Gossip: Probabilistic Reliable Multicast in Ad Hoc Networks, IEEE, Luigi Rizzo, Lorenzo Vicisano, RMDP: an FEC-based Reliable Multicast protocol for wireless, CiteSeer, 1998.

72 END