Reliable Multicast Protocols for MANET 授課：童曉儒 教授 國立屏東科技大學 資管 系 1
Outline • An Overview of MANET • An Overview of Reliable Multicast Protocol • Automatic Retransmission re. Quest 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 (Re. Act) 2
• 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 3
An Overview of MANET • Definition • Characteristics • Limitations 4
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, and. Liu, 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 5
Characteristics • Infrastructure-less or with minimum infrastructure support • Self-organizing and self-managing • Multi-hop 6
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 7
Self-organizing and selfmanaging • Since network infrastructure is not available, the nodes must organize and maintain the network by themselves 8
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 9
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 10
An Overview of Reliable Multicast Protocol • • What is Multicast Communication? What is Reliable Multicast use in MANET? Three categories according to the recovery mechanisms being used 11
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 12
IP Multicast Communication 13
Example IP Multicast Use (Access Grid ) 14
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 15
Example Reliable Multicast Use (Remote Instrument Access) 16
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 and heavy overhead 17
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-topeer fashion • Forward Error Correction (FEC)-based – embed redundant data (e. g. , erasure code) in each packet before transmitting. 18
• Automatic Retransmission re. Quest 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 (Re. Act) 19
Reliable Multicast Algorithm (RMA) • Assumption • Protocol description • Advantage versus Disadvantage 20
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 21
Protocol description • RMA works in two phases: – multicast – retransmission • Two types of multicast messages to the group member – MKNOWN • unicast – MUNKNOWN • broadcast 22
• 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 23
Hello Message 24
MKNOWN Message 25
MUKNOWN Message 26
MACK Message 27
BMACK Message 28
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 29
Reliable Adaptive Light Weight Multicast Transport protocol (RALM) • Assumption • Protocol description • Advantage versus Disadvantage 30
Assumption • RALM assumes that the group membership is known to the sources • This enables the sources to maintain a Receiver List 31
Protocol description • Source selects a node from the receiver list as a feedback receiver in a roundrobin 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 32
• 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 33
• This single-node feedback approach is effective when packet losses are due to congestion at a bottleneck link 34
Receiver List B B A A C C B B D C C A Fee Rec Rec Rec C B D 35
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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 38
Reliable, Adaptive, Congestion-Controlled Adhoc Multicast Transport Protocol (Re. Act) • Assumption • Protocol description • Advantage versus Disadvantage 39
Assumption • source-oriented component works the same as RALM 40
Protocol description • Re. Act 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 41
• 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 42
A C B Packet Loss 43
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 44
• Gossip-Based Reliable Multicast Protocols – Anonymous Gossip (AG) – Route Driven Gossip (RDG) 45
Anonymous Gossip (AG) • Assumption • Protocol description • Advantage versus Disadvantage 46
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 47
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 48
• 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. 49
Multicast Protocol + Classical Gossip = Probabilistic Reliability • Works in background with multicast protocol. • Members “gossip” randomly with other members to recover lost messages. • Probabilistic reliability guarantees. 50
Classical Gossip S D 51
Anonymous Gossip S D 52
Informed Gossip S D 53
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 54
Route Driven Gossip (RDG) • Assumption • Protocol description • Advantage versus Disadvantage 55
Assumption • RDG does not use full multicast membership information, but partial knowledge • RDG builds on top of a MANET unicast routing protocol DSR 56
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 57
• each new data packet will be gossiped for a few number of times (quiescence threshold) to ensure its spreading 58
Data Structures Identifier Group identifier 4 5 0 5 JOIN RECEIVEGREQUEST 1 Data buffer • new 0 3 • old 0 GOSSIP 5 RECEIVEGOSSIP 1 View LEAVE • active • passive • remove 1 0 2 1 fanout Push Pull F quiescence threshold τq Data packets, digests of missing packets, view 59
15 9, 10 9 3, 5 5 1, 19 10 1, 13 13 10, 15 2 1, 8 15 5, 3 9 10, 13 10 2, 8 All members receive the message. 60
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 61
• Forward Error Correction (FEC) Based Reliable Multicast Protocols – Reliable Multicast Data Distribution Protocol (RMDP) 62
Reliable Multicast Data Distribution Protocol (RMDP) • Assumption • Protocol description • Advantage versus Disadvantage 63
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 64
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 65
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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 67
Comparisons 68
Conclusions • classification based on the recovery mechanisms • The analyses and comparisons will help in choosing a suitable reliable multicast protocol for specific network conditions 69
REFERENCES • Beini Ouyang and Xiaoyan Hong, Yunjung Yi, “A Comparison of Reliable Multicast Protocols for Mobile Ad Hoc Networks”, Proceedings. IEEE 8 -10 April 2005 Page(s): 339 - 344 , Southeast. Con, 2005. • Thiagaraja Gopalsamy, Mukesh Singhal, D. Panda and P. Sadayappan, “A Reliable Multicast Algorithm for Mobile Ad hoc Networks”, Proceedings. 22 nd International Conference on 2 -5 July 2002 Page(s): 563 - 570, Distributed Computing Systems, 2002. • Ken Tang, Katia Obraczka, Sung-Ju Lee, Mario Gerla, “Reliable Adaptive Lightweight Multicast Protocol”, IEEE International Conference on Volume 2, 11 -15 May 2003 Page(s): 1054 - 1058 vol. 2 , Communications, 2003. ICC '03. • Ken Tang, Katia Obraczka, Sung-Ju Lee, Mario Gerla, “A Reliable, Congestion-Controlled Multicast Transport Protocol in Multimedia Multi-hop Network”, Proceedings of IEEE WPMC 2002, Honolulu, USA, October 2002, pp. 252 -256. 70
• Ranveer Chandra, Venugopalan Ramasubramanian, Kenneth P. Birman, “Anonymous Gossip: Improving Multicast Reliability in Mobile Ad-Hoc Networks”, International Conference on Distributed Computing Systems, April 2001, pp. 275 -283. • Jun Luo, Patrick Th. Eugster, Jean-Pierre Hubaux, “Route Driven Gossip: Probabilistic Reliable Multicast in Ad Hoc Networks”, INFOCOM’ 03, San Francisco, CA, March 2003, pp. 2229 -2239. • Luigi Rizzo, Lorenzo Vicisano, “RMDP: an FEC-based Reliable Multicast protocol for wireless”, ACM Mobile Computing and Communications Reviews, Apr. 1998, 2(2): 23 -31. 71
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