"contentUrl": "https://slideplayer.com/slide/15241940/92/images/30/Architecture+Central+protocol+%3D%3E+Lego+Blocks.jpg", "width": "1024" "width": "1024" "width": "1024" Flexible group communication model to application developers. there is no guarantee regarding ordering or reliability) How can we achieve group communication ? "description": "Introduced in ISIS, orders group membership changes along with the regular messages. Safe Delivery. FIFO. "description": "Network partitions and recovery tools. A large-scale multicast service designed with the following goals, Tackling network partitions and providing tools for recovery from them, Meeting needs of large networks through hierarchical communication, Exploiting fast-clustered communication using IP-Multicast, Formal specifications of group communication systems, Support for CSCW and multimedia applications, Group based Communication with incomplete spatial coverage. Virtual Synchrony . "@type": "ImageObject", "@context": "http://schema.org", Members can totally-order past view changes events. "@type": "ImageObject", "description": "Transis disseminate files to group members. "name": "Reliability Service",

use for replication of network tables. { Architecture gives flexible runtime by varying the protocol layer supporting a group. "@context": "http://schema.org", If network partition, one component (containing Primary) can perform updates. "description": "Message is delivered to all processes or to none at all. "width": "1024" "width": "1024" have shown that it is impossible to maintain a primary component that is agreed upon and known in all circumstances. every message sent is received. Query-map: Retrieve information from the map. Chapter 25 Internet Routing Internetworking Technology How routing tables are built initially How routing software updates the tables as needed. Simultaneous execution of the same operation in a group of workstations. Introduced in ISIS, orders group membership changes along with the regular messages, Ensures that failures do not result in incomplete delivery of multicast messages or holes in the causal delivery order(failure atomicity), Ensures that, if two processes observe the same two consecutive membership changes, receive the same set of regular multicast messages between the two changes, A view change acts as a barrier across which no multicast can pass, Does not constrain the behavior of faulty or isolated processes. Interface includes operation pop\/push headers. "@context": "http://schema.org", "@type": "ImageObject", ", "description": "Introduced in Totem. Trans\/Total System and Amoeba: Allow continued operations.

Totem Provides a Reliable totally ordered multicast service over LANIntended for complex applications in which fault-tolerance and soft real-time performance are critical High throughput and low predictable latency Rapid detection of, and recovery from, faults System wide total ordering of messages Scalable via hierarchical group communication Exploits hardware broadcast to achieve high-performance Provides 2 delivery services Agreed Safe Use timestamp to ensure total order and sequence numbers to ensure reliable delivery Some GC Properties Atomic Multicast Failure Atomicity UniformityMessage is delivered to all processes or to none at all. { one-to-many relationship. Function adds header. 3. "@context": "http://schema.org", { Each machine should know about the update messages that reached all of the other machines before they were disconnected. ", }, 35 Initially point-to-point (TCP\/IP) Fail-stop failure model.

Update-map: Update map while preserving consistency between replicas. CORBA-Compliant interface. After delivery of all messages, new configuration is delivered. Transis supports partitionNot all applications progress is dependent on a primary component. 2022 SlidePlayer.com Inc. All rights reserved. View change reporting and message delivery at different members of a group is dealt by the group service. ", "@context": "http://schema.org", Non-primary can generate a new primary if it is lost. "description": "Bottommost block invokes a driver to send message. "@context": "http://schema.org", "@context": "http://schema.org", Highly and easy scalable. )", "@context": "http://schema.org", Future Challenges Secure group communication architectureFormal specifications of group communication systems Support for CSCW and multimedia applications Dynamic Virtual Private Networks Next Generations Spread Ensemble Wireless networks ? "@context": "http://schema.org", Extended virtual synchronyIntroduced in Totem Processes can fail and recover Network can partition and remerge Does not solve all the problems of recovery in fault-tolerant distributed system, but it avoid inconsistencies }, 44 It does this by stacking protocol modules one on top of the other like lego blocks. "name": "Group Communication as an Infrastructure for Distributed System Management", "@context": "http://schema.org", The system helps abstract the user from identifying the targets and the network routes. installation multicast group Gp. Fast cluster communication. ", How different components of a partition network can operate autonomously and then merge operations when they become reconnected ? "name": "Message Passing System", Message_send is recursively sent down the stack. CS 582 / CMPE 481 Distributed Systems Fault Tolerance. Membership ensures that all processes in a configuration agree on the membership of that configuration. { no message is received more than once at any single object. Software Engineering and Middleware: a Roadmap by Wolfgang Emmerich Ebru Dincel Sahitya Gupta. { "width": "1024" Dont provide recovery mechanism "@context": "http://schema.org", Process in a regular or transitional configuration can deliver a configuration change message s.t. Monitor multicasts a msg advertising package P set of installation requirements Rp installation multicast group Gp target list Tp. Failures do not result in incomplete delivery of multicast messages or holes in the causal delivery order. "description": "TCP\/IP. Is a multicast communication layer at the transport layer. High throughput and low predictable latency. "name": "A Group Communication Subsystem", "description": "Communication to a collection of processes \u2013 process group. "contentUrl": "https://slideplayer.com/15241940/92/images/slide_31.jpg", ..The principle guarantees that a local view is reported to any member is reported to all the members, unless they crash. Atomicity. "width": "1024" ", Virtual Synchrony. Each machine should know about the update messages that reached all of the other machines before they were disconnected. { No Duplicates. ", Farnaz Moradi Based on slides by Andreas Larsson 2013. Support for CSCW and multimedia applications. Causally ordered, guarantees response to a message is never delivered before request 3. Transis : Group Communication SystemNetwork partitions and recovery tools. { "contentUrl": "https://slideplayer.com/slide/15241940/92/images/40/Group+multicast+operations%3A.jpg", "@context": "http://schema.org", "@type": "ImageObject", Properties of Protocol Stack. Follows delivery of every message in the terminated configuration and precedes delivery of every message in the new configuration. "width": "1024" Group Communication Who needs group communication ?Communication to a collection of processes process group Group communication can be exploited to provide Simultaneous execution of the same operation in a group of workstations Software installation in multiple workstations Consistent network table management Who needs group communication ? "@type": "ImageObject", Extending point-to-point networks "width": "1024" "@context": "http://schema.org", }, 23 { }, 46 May also require that messages are delivered in the same order to all processes. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/5/Message+Passing+System+%28II%29.jpg", All members are equal. When it receives a message, it truncates the header and sends the rest of the message to the layer above it. "name": "ISIS Tightly coupled distributed system developed over loosely coupled processors. Failure atomicity. Totally Ordered. In Transis, local views can be merged efficiently. CS-550: Distributed File Systems [SiS]1 Resource Management in Distributed Systems: Distributed File Systems. "width": "1024" ", Local storage structure. "description": "Transis is group communication layer: provide reliable multicast and membership services. Define. { (Agreed)Totally ordered, incurs higher delays, useful for supporting replicated data 4. Delivery Guarantees.

", "contentUrl": "https://slideplayer.com/slide/15241940/92/images/22/Configuration+change+Process+in+a+regular+or+transitional+configuration+can+deliver+a+configuration+change+message+s.t..jpg", }, 41 Delivery permanence (majority agreement) All-or-none delivery (multicast to multiple groups) Ordered delivery (serializability of multiples groups) Transactions-based on group communication primitives represents an important step toward extending the power and generality of GComm. COS 461 Fall 1997 Group Communication u communicate to a group of processes rather than point-to-point u uses replicated service efficient dissemination. }, 10 "@context": "http://schema.org", }, 25 Ordering. They used the x-kernel as a use case where the interface was not rich enough. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/25/Horus+Aims+to+provide+a+very+flexible+environment+to+configure+group+of+protocols+specifically+adapted+to+problems+at+hand..jpg", Multiple disconnected components in the network operate autonomously. Standardized top and bottom interface (HCPI) Allow blocks to communicate. "width": "1024" Membership ensures that all processes in a configuration agree on the membership of that configuration. Each module is responsible for a particular protocol. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/18/Extended+virtual+synchrony.jpg", Status of all Management server reported to Monitor. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/38/Systems+that+depend+on+primary+component%3A.jpg", Members can totally-order past view changes events. Uniformity. ..The principle guarantees that a local view is reported to any member is reported to all the members, unless they crash. { Many mechanisms for enforcing security policy in distributed systems rely on trusted nodes. Each module is responsible for a particular protocol. Point-to-point messages. "@type": "ImageObject", "description": "", "width": "1024" "name": "Extended Virtual Synchrony Model", }, 21 }, 51

"@type": "ImageObject", Although any combination of layers can be produced, most layers require certain semantics from the layer below them. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/53/Questions+How+can+we+achieve+group+communication.jpg", Object oriented distributed applications that comply with CORBA can incoke one another\u2019s mehtods with relative ease. Causal.

"@context": "http://schema.org", "description": "Message omission and delay. failure cascade), this process is repeated all over again. ", { "@type": "ImageObject", At least one component of the network should be able to continue making updates. Message_send Lookup the entry in topmost block and invokes the function. "name": "Message_send Lookup the entry in topmost block and invokes the function. Standardized top and bottom interface (HCPI) Allow blocks to communicate A block has entry points for upcall/downcall Upcall=receive mesg, Downcall=send mesg. Group address: to which message is sent View: List of destination endpoint addr of accessible group members Message Local storage structure Interface includes operation pop/push headers Passed by reference Besides dealing with threads and memory, each stack needs to deal with endpoints, group , and message objects. 16: Distributed Systems1 DISTRIBUTED SYSTEM STRUCTURES NETWORK OPERATING SYSTEMS The users are aware of the physical structure of the network. }, 49 CORBA compliant interface to Horus. Svrs. "@type": "ImageObject",

"width": "1024" Multiple disconnected components in the network operate autonomously. { Management services: Long term: consistent semantics over partitions and over time use for replication of network tables Short term: Reliable as long as network is not partitioned and management server does not crash Ex. ", "contentUrl": "https://slideplayer.com/slide/15241940/92/images/24/ISIS+Tightly+coupled+distributed+system+developed+over+loosely+coupled+processors..jpg", It provides support for the virtually synchronous execution model, introduced by the Isis Toolkit. Every message is delivered in the context of a certain configuration, which is not always accurate. "@context": "http://schema.org", { "contentUrl": "https://slideplayer.com/slide/15241940/92/images/13/Virtual+Synchrony+Virtual+Synchrony.jpg", ", ", 4. ", of Information Management National Taiwan. 1 Primary Server. }, 28 Failures do not result in incomplete delivery of multicast messages or holes in the causal delivery order, A view change reported to a member is reported to all other members. Have own threads and memory scheduler. "description": "Peer. Failure. When a membership change (network partition, merge, or server crash) it is reported by group communication layer. Diffusion group. UDP, IP-multicast - assumes h\/w support. Representative replays messages upon merging. ", { a a3. 2. { Communication primitives available in distributed systems are too weak (i.e. All members send messages to the group. Hierarchical BroadcastEach multicast "width": "1024" Several monitors can run simultaneously in the network Group address: to which message is sent. "name": "A Flexible Group Communication Subsystem", Regular conf members (that are still connected) start exchanging information. { "width": "1024" { { "@context": "http://schema.org", "@type": "ImageObject", "@context": "http://schema.org", Group Communication as an Infrastructure for Distributed System ManagementTable Management User accounts, network tables Software Installation and Version Control Speed up installation, minimize latency and network load during installation Simultaneous Execution Invoke same commands on several machines "@type": "ImageObject", "@type": "ImageObject", }, 34 "description": "", Processor crashes and recoveries. "@type": "ImageObject", When a membership change (network partition, merge, or server crash) it is reported by group communication layer.

"name": "Each stack shielded from each other. guarantees total order of message delivery and allows a message to be delivered as soon as all of its predecessors in the total order have been delivered. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/27/Future+Challenges+Secure+group+communication+architecture.jpg", "width": "1024" "width": "1024" "@context": "http://schema.org",

"width": "1024" Merge these components upon recovery. Transis disseminate files to group members. It does this by stacking protocol modules one on top of the other like lego blocks. }, 43 ", "@context": "http://schema.org", Multiple disconnected components in the network operate autonomously. Safe. Upon recovery, only the missing messages should be exchanged to bring the machines back into a consistent state. every message sent is received. Local views provided by a group service may not be accurate beacues failure detection in a system is generally unreliable. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/11/Failure+Model+Failures+types.jpg", { Period before partition detected, non-primaries can continue to operate.

}, 6 Network can partition and remerge. A view change reported to a member is reported to all other members. ", Upon reaching a decision (on members and messages) process delivers transitional configuration message to members with agreed list of messages. Upon recovery, only the missing messages should be exchanged to bring the machines back into a consistent state. "@type": "ImageObject", Update of the common state requires. ", ", Use timestamp to ensure total order and sequence numbers to ensure reliable delivery. Causally ordered, guarantees response to a message is never delivered before request. Reliability Service A service is reliable (in presence of f faults) if exists a partition of the object indices into faulty and non-faulty such that there are at most f faulty objects and the mapping of k must satisfy: Integrity No Duplicates no message is received more than once at any single object Liveness Non-faulty liveness When restricted to non-faulty objects, k is onto.

", "name": "Extended Virtual Synchrony(cont. }, 5 {

"name": "", "width": "1024" "@type": "ImageObject", }. Agreed. { }, 18 ", To use this website, you must agree to our, Communication to a collection of processes process group, Group communication can be exploited to provide, Simultaneous execution of the same operation in a group of workstations, Software installation in multiple workstations, Client may or may not care which server answers, Servers sends to other servers and clients, A system consist of n objects a0, , an-1, Each object ai is modeled as a (possible infinite) state machine with state set Qi, The edges incident on ai are labeled arbitrarily with integers 1 through r, where r is the degree of ai, Each state of ai contains 2r special components, outbufi[l], inbufi[l], for every l r, A configuration is a vector C=(qo,,qn-1), where qi is the state of ai, A system is said to be asynchronous if there is no fixed upper bound on how long it takes a message to be delivered or how much time elapses between consecutive steps, A variation of broadcast where an object can target its messages to a specified subset of objects, Automatic flow control, reliable delivery, connection service, complexity, message losses high(30%) during heavy load, For all messages m1, m2 and all objects ai, aj, if ai sends m1 before it sends m2, then m2 is not received at aj before m1 is, For all messages m1, m2 and all objects ai, aj, if m1 is received at ai before m2 is, the m2 is not received at aj before m1 is, For all messages m1, m2 and all objects ai, aj, if m1 happens before m2, then m2 is not received at ai before m1 is. { Distributed Systems Fall 2009 Replication Fall 20095DV0203 Outline Group communication Fault-tolerant services Passive and active replication Highly. Delivery guarantees Agreed Delivery Safe Deliveryguarantees total order of message delivery and allows a message to be delivered as soon as all of its predecessors in the total order have been delivered. Provides 2 delivery services. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/42/Transis+supports+partition.jpg", "@type": "ImageObject", Operations are inconsistent with primary Trans/Total System and Amoeba: Allow continued operations Inconsistent Operations may occur in different parts of the system. ", "description": "Transis. Each object ai is modeled as a (possible infinite) state machine with state set Qi. Regular configuration may be followed and preceeded by several transitional configurations. k is well defined. Network partitions are real. Tackling network partitions and providing tools for recovery from them. "width": "1024" "contentUrl": "https://slideplayer.com/slide/15241940/92/images/12/Some+GC+Properties+Atomic+Multicast+Failure+Atomicity+Uniformity.jpg", "width": "1024" Architecture gives flexible runtime by varying the protocol layer supporting a group. Use technique in Simultaneous Execution to execute installation commands. Scalable via hierarchical group communication. Architecture Central protocol => Lego BlocksEach Lego block implements a communication feature. ", Recover possible loss. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/51/Software+Installation.jpg", Each membership with a unique identifier is a configuration. Activate a daemon, run a script. IM NTU Distributed Information Systems 2004 Replication Management -- 1 Replication Management Yih-Kuen Tsay Dept. {

", Set M: most recent membership of the group reported by transis, Set NR: set of currently connected servers not yet reported the outcome of a command execution to the monitor. Network partitions and re-merges. "@type": "ImageObject", "name": "Faults and Partitions When detecting a processor P from which we did not hear for a certain timeout, we issue a fault message. "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "https://slideplayer.com/slide/15241940/92/images/16/Reliability+Service.jpg", ", Published byJari Ahola linear degradation in performance. "name": "Architecture", Termination. Don\u2019t provide recovery mechanism. i.e. "@type": "ImageObject", "contentUrl": "https://slideplayer.com/slide/15241940/92/images/2/Group+Communication+Who+needs+group+communication.jpg", Algorithm for determining transitional configuration When a membership change is identified Regular conf members (that are still connected) start exchanging information If another membership change is spotted (e.g. "description": "Manager of group messages and group views. }, 45 }, 8 "width": "1024" Extensive use of general purpose operations were required causing the configuration of the system to be less flexible. { Not all applications progress is dependent on a primary component. "@type": "ImageObject", "description": "Formal specifications of group communication systems. Monitor Provides user interface to mgmt server. "description": "FIFO ordered. "description": "Have own threads and memory scheduler. }, 50 A process, can run on any node that runs transis. requires in addition, that if a message is delivered by the GC to any of the processes in a configuration, this message has been received and will be delivered to each of the processes in the configuration unless it crashes. 2.Knowing about the delivery of every message by all the components require instantaneous knowledge. "description": "At least one component of the network should be able to continue making updates. Group Communications Group communication: one source process sending a message to a group of processes: Destination is a group rather than a single process. virtual synchrony. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/47/Architecture.jpg", Faulty liveness. Under high network traffic, network and underlying protocol is driven to high loss rate. Wireless networks Group based Communication with incomplete spatial coverage. }, 52 Besides dealing with threads and memory, each stack needs to deal with endpoints, group , and message objects. Upon reaching a decision (on members and messages) process delivers transitional configuration message to members with agreed list of messages. Ensemble.

}, 29 When a membership change (network partition, merge, or server crash) it is reported by group communication layer. For all messages m1, m2 and all objects ai, aj, if m1 is received at ai before m2 is, the m2 is not received at aj before m1 is. Reliability on Web Services Presented by Pat Chan 17/10/2005. "@type": "ImageObject", Each Lego block implements a communication feature. Configuration change Process in a regular or transitional configuration can deliver a configuration change message s.t. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/54/From+Group+Communication+to+Transactions.jpg", "name": "Messaging and Group Communication", ", Software InstallationTransis disseminate files to group members. "description": "", Distributed Logging\u2026. Clients. Provides user interface to mgmt server. When restricted to non-faulty objects, k is onto. "@context": "http://schema.org", Hierachical communication structure. Have its own prioritized threads and controlled access to memory through channels.

{ Message_send is recursively sent down the stack. (Agreed)Totally ordered, incurs higher delays, useful for supporting replicated data. no message is received more than once. "name": "Architecture Central protocol => Lego Blocks", To make this website work, we log user data and share it with processors. Dynamic Virtual Private Networks.

}, 39 "description": "Identical management command on many machines. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/19/Extended+Virtual+Synchrony%28cont.%29.jpg", Liveness. Each module is responsible for a particular protocol. Positive ack are piggybacked into regular mesg. Transis is group communication layer: provide reliable multicast and membership services. one-to-all relationship.

Discover message omission and (usually) recovers lost messages. The system helps abstract the user from identifying the targets and the network routes. There exists a mapping k from the set of messages appearing in all rcvi(m) for all i, to the set of messages appearing in sndi(m) for all i, such that each message m in a rcv() is mapped to a message with the same content appearing in an earlier snd() and: k is well defined. "@type": "ImageObject", "description": "Ordering. Status of all Management server reported to Monitor. "@context": "http://schema.org", "name": "Table Management Consistent management of replicated network tables. i.e. Simultaneous Execution. Faults are detected using an unreliable fault detector, based on a timeout mechanism. Hidden View: Like local view, indicated the view has failed but may have formed in another part of the system. Run in userspace. package P. set of installation requirements Rp. Messaging and Group CommunicationICS 243F Distributed Systems Middleware "width": "1024" Are different protocols for fast-local and slower-cluster communication needed ? Use negative-ack. have shown that it is impossible to maintain a primary component that is agreed upon and known in all circumstances. Inconsistent Operations may occur in different parts of the system. Is a multicast communication layer at the transport layer. View change reporting and message delivery at different members of a group is dealt by the group service. Traditionally operations were performed using TCP\/IP, waste bandwidth.

"description": "Virtual synchrony handles recovered processes as new processes. }, 7

"contentUrl": "https://slideplayer.com/15241940/92/images/slide_14.jpg", Causally Ordered. Liveness. "width": "1024" "width": "1024" Monitor. }, 30 "contentUrl": "https://slideplayer.com/slide/15241940/92/images/41/Network+partition+wishlist.jpg",

Transis How different components of a partition network can operate autonomously and then merge operations when they become reconnected ? Servers sends to other servers and clients. Who needs group communication Highly available servers. ", "description": "guarantees total order of message delivery and allows a message to be delivered as soon as all of its predecessors in the total order have been delivered. Create new protocol by rearranging blocks. 1.Chandra et al. Maintains a vector of contexts, 1 entry for each monitor it is currently interacting w/ also current directory of the server set by the monitor. Extended Virtual Synchrony ModelNetwork may partition into finite number of components Two or more may merge to form a larger component Each membership with a unique identifier is a configuration. Gateways, bridges, wireless communication. how to create, join and leave a group. ", Group Communication IssuesOrdering Delivery Guarantees Membership Failure "@type": "ImageObject", { Lab 2 Group Communication Farnaz Moradi Based on slides by Andreas Larsson 2012. "@type": "ImageObject", "contentUrl": "https://slideplayer.com/slide/15241940/92/images/39/Group+Service+Work+of+the+collection+of+group+modules..jpg", "name": "Extended virtual synchrony", Non-primary can remain operational and wait to merge with primary.

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