PPT-CSE 486/586 Distributed Systems

Global States Steve Ko Computer Sciences and Engineering University at Buffalo Last Time Ordering of events Many applications need it eg collaborative editing distributed storage etc Logical time. Domain Name System. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Last Time. Global states. A union of all process states. Consistent global state vs. inconsistent global state. Security --- 2. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Three . types of functions. Cryptographic hash, symmetric key crypto, asymmetric key . crypto. Cryptographic hash. Concurrency Control --- 3. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Strict execution of transactions?. Delay . both their read and write operations . on an . object until . Google Chubby Lock Service. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Paxos. is a consensus algorithm.. Proposers?. Acceptors?. Learners?. A proposer always makes sure that,. Google Chubby Lock Service. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Paxos. is a consensus algorithm.. Proposers?. Acceptors?. Learners?. A proposer always makes sure that,. Consistency --- 3. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Consistency. Linearizability. ?. Sequential consistency?. Chain replication. Primary-backup (passive) replication. Case Study: Amazon Dynamo. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. CAP Theorem?. Consistency, Availability, Partition Tolerance. Pick two. Eventual consistency?. Availability and partition tolerance over consistency. New Trends in Distributed Storage. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Two important components in a distributed file service?. Directory service. Flat file service. Gossiping. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recall: Passive Replication. Request Communication. : the request is issued to the primary RM and carries a unique request id.. Gossiping. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Consistency models. Linearizability. Sequential consistency. Causal consistency. Eventual consistency. Depending on application scenarios, one consistency model makes more sense that others.. Byzantine Fault . Tolerance --- 1. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Digital certificates. Binds a public key to its owner. Establishes a chain of trust. TLS. Reliable Multicast --- 2. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap: Multicast. How do a group of processes communicate?. Multicast. One-to-many: “Local” broadcast within a group . Gossiping. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Available copies replication?. Read and write . p. roceed with live replicas. Cannot achieve one-copy serialization itself. Paxos. --- 2. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Paxos. is a consensus algorithm.. It allows multiple acceptors accepting multiple proposals.. A proposer always makes sure that,.