message ordering and group communication ppt

CORBA compliant interface to HorusCORBA compliant interface to Horus. Exploiting fast-clustered communication using IP-Multicast. Transis is group communication layer: provide reliable multicast and membership services. Cluster management. "@type": "ImageObject", "contentUrl": "https://slideplayer.com/slide/15241940/92/images/39/Group+Service+Work+of+the+collection+of+group+modules..jpg", Failure. "@context": "http://schema.org", Safe. "description": "Horus. "name": "Extended Virtual Synchrony(cont. A machine that does not respond to messages sent to it is removed from the local view of the sender within a finite amount of time. { Questions How can we achieve group communication ?Could provide tolerance for malicious intrusion Many mechanisms for enforcing security policy in distributed systems rely on trusted nodes While no single node need to be fully trusted, the function performed by the group can be Problems Network partitions and re-merges Messages omissions and delays Communication primitives available in distributed systems are too weak (i.e. i.e. Support recovering a primary component. "description": "", }, 32 Members can totally-order past view changes events. "@context": "http://schema.org", "name": "Table Management Consistent management of replicated network tables. "@type": "ImageObject", "contentUrl": "https://slideplayer.com/slide/15241940/92/images/54/From+Group+Communication+to+Transactions.jpg", "width": "1024" Status of all Management server reported to Monitor. "@context": "http://schema.org", Does not constrain the behavior of faulty or isolated processes. Simultaneous execution and sw installation. A Flexible Group Communication SubsystemHorus A Flexible Group Communication Subsystem "contentUrl": "https://slideplayer.com/slide/15241940/92/images/26/Transis+How+different+components+of+a+partition+network+can+operate+autonomously+and+then+merge+operations+when+they+become+reconnected.jpg", Activate a daemon, run a script Management Server maintains 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 ", ", No new messages are broadcast, only remaining messages from prior regular configuration are delivered. Horus solves this by numbering the messages and uses event count synchronization variables to construct the order then its necessary. "@context": "http://schema.org", { "width": "1024"

Distributed Logging\u2026. }, 20 "description": "Adequate group communication can support a specific class of transactions in asynchronous distributed systems. every message sent is received "@context": "http://schema.org", Chapter 25 Internet Routing Internetworking Technology How routing tables are built initially How routing software updates the tables as needed. Each module is responsible for a particular protocol. "description": "Introduced in Totem. no message is received more than once. 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 However, we may want to guarantee, Discover message omission and (usually) recovers lost messages, Assume that faults do not corrupt messages ( or that message corruption can be detected), Most systems do not deal with Byzantine behavior, Faults are detected using an unreliable fault detector, based on a timeout mechanism. a1. "name": "Management Server API Status: Return status of server and its host machines. "@context": "http://schema.org", Delivery Guarantees. i.e.

"name": "A Flexible Group Communication Subsystem",

"@type": "ImageObject", "width": "1024" { }, 18 }, 2 "@context": "http://schema.org", In Transis, local views can be merged efficiently. "name": "Network partition wishlist", If another membership change is spotted (e.g. "@type": "ImageObject", In having both local and hidden view, we get the inter-relations between views at different machines. "description": "ICS 243F. Local views provided by a group service may not be accurate beacues failure detection in a system is generally unreliable. It provides support for the virtually synchronous execution model, introduced by the Isis Toolkit. A thread at bottommost layer waits for messages to arrive at the network interface. More Interesting GC PropertiesThere 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: Integrity k is well defined. { Simultaneous Execution. Safety delivery, highest delay, delivery of the mesg after all the components have received the mesg. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/53/Questions+How+can+we+achieve+group+communication.jpg", "name": "Questions How can we achieve group communication", Period before partition detected, non-primaries can continue to operate. "@type": "ImageObject", A machine that does not respond to messages sent to it is removed from the local view of the sender within a finite amount of time. Passed by reference. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/15/More+Interesting+GC+Properties.jpg", "description": "Each multicast. Regular conf members (that are still connected) start exchanging information. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/2/Group+Communication+Who+needs+group+communication.jpg",

Regular configuration may be followed and preceeded by several transitional configurations. }, 29 Causally ordered, guarantees response to a message is never delivered before request, 3. Set M: most recent membership of the group reported by transis. Architecture Central protocol => Lego BlocksEach Lego block implements a communication feature. }, 50

How different components of a partition network can operate autonomously and then merge operations when they become reconnected ? i.e. Network partition wishlistAt least one component of the network should be able to continue making updates. 1 A Modular Approach to Fault-Tolerant Broadcasts and Related Problems Author: Vassos Hadzilacos and Sam Toueg Distributed Systems: 526 U1580 Professor: Lecture 2 TCP/IP Protocol Suite Reference: TCP/IP Protocol Suite, 4 th Edition (chapter 2) 1. "@context": "http://schema.org", "description": "Provides a toolkit mechanism for distributing programming, whereby a DS is built by interconnecting fairly conventional non-distributed programs, using tools drawn from the kit. Share buttons are a little bit lower. "name": "Message_send Lookup the entry in topmost block and invokes the function. View change reporting and message delivery at different members of a group is dealt by the group service. { "contentUrl": "https://slideplayer.com/slide/15241940/92/images/8/Ordering+Service+Unordered+Single-Source+FIFO+%28SSF%29+Totally+Ordered.jpg", Protocol layers can be mixed and matched freely. Supports reliable process group communication for high availability, facilitates development of fault tolerant distributed applications. Multiple disconnected components in the network operate autonomously. The system helps abstract the user from identifying the targets and the network routes. In Transis, local views can be merged efficiently. When it receives a message, it truncates the header and sends the rest of the message to the layer above it. "name": "Simultaneous Execution", Non-primary can remain operational and wait to merge with primary. ", "name": "ISIS Tightly coupled distributed system developed over loosely coupled processors. "width": "1024" Reliable Multicast EngineIn system that do not lose messages often Use negative-ack Messages not retransmitted Positive ack are piggybacked into regular mesg Detection of lost messages detected ASAP Under high network traffic, network and underlying protocol is driven to high loss rate. Failure atomicity. (Agreed)Totally ordered, incurs higher delays, useful for supporting replicated data 4. "width": "1024" there is no guarantee regarding ordering or reliability) How can we achieve group communication Extending point-to-point networks. Speed up installation, minimize latency and network load during installation. "name": "Horus Aims to provide a very flexible environment to configure group of protocols specifically adapted to problems at hand. User accounts, network tables. Regular configuration may be followed and preceeded by several transitional configurations. Support recovering a primary component. Algorithm for determining transitional configuration. Invoke same commands on several machines. Although any combination of layers can be produced, most layers require certain semantics from the layer below them. Who needs group communication Highly available servers. "@context": "http://schema.org", }, 48 "contentUrl": "https://slideplayer.com/slide/15241940/92/images/4/Message+Passing+System.jpg", We think you have liked this presentation. 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. "@type": "ImageObject", "width": "1024" "description": "Virtual synchrony handles recovered processes as new processes. }, 40 "width": "1024" package P. set of installation requirements Rp. ", "width": "1024" Simultaneous execution and sw installation, Maintains a vector of contexts, 1 entry for each monitor it is currently interacting w/. "@context": "http://schema.org", installation multicast group Gp. there is no guarantee regarding ordering or reliability), Adequate group communication can support a specific class of transactions in asynchronous distributed systems, Transaction is a sequence of operations on objects (or on data) that satisfies, 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, Download ppt "Messaging and Group Communication". "name": "Horus: A Flexible Group Communication System", "@type": "ImageObject", { "name": "", 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 ? "name": "Messaging and Group Communication", ..The principle guarantees that a local view is reported to any member is reported to all the members, unless they crash. "@type": "ImageObject", 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. "description": "Ordering. Network partitions are real. "width": "1024" While no single node need to be fully trusted, the function performed by the group can be. { "name": "Configuration change Process in a regular or transitional configuration can deliver a configuration change message s.t. "name": "Totem Provides a Reliable totally ordered multicast service over LAN",

Use technique in Simultaneous Execution to execute installation commands. Each module is responsible for a particular protocol. "@type": "ImageObject", "contentUrl": "https://slideplayer.com/slide/15241940/92/images/10/Membership+Messages+addressed+to+the+group+are+received+by+all+group+members..jpg", It does this by stacking protocol modules one on top of the other like lego blocks. "name": "Reliability Service", "@type": "ImageObject", "width": "1024" "description": "In system that do not lose messages often. Rapid detection of, and recovery from, faults. Besides dealing with threads and memory, each stack needs to deal with endpoints, group , and message objects. Message_send is recursively sent down the stack. "contentUrl": "https://slideplayer.com/slide/15241940/92/images/36/A+Group+Communication+Subsystem.jpg", Hierarchical BroadcastEach multicast 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. }, 38 }, 7 "contentUrl": "https://slideplayer.com/slide/15241940/92/images/20/Extended+Virtual+Synchrony+Model.jpg", Assume that faults do not corrupt messages ( or that message corruption can be detected) Most systems do not deal with Byzantine behavior. Inconsistent Operations may occur in different parts of the system.