L19.sp11 - Distributed Systems Distributed Systems CS 425 /...

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Distributed Systems CS 425 / CSE 424 / ECE 428 Distributed Systems CS 425 / CSE 424 / ECE 428 Networking Reading: Chapter 3 (relevant parts) 010, I . Gupta, K. Nahrtstedt, S. Mitra, N. Vaidya, M. T. Harandi, J. Hou
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Our Distributed System Definition Our Distributed System Definition A distributed system is a collection of entities, each of which is autonomous , programmable , asynchronous and failure-prone , and communicating through an unreliable communication medium. Our interest in distributed systems involves design and implementation, maintenance, study, algorithmics Entity=a process on a device (PC, PDA) Communication Medium=Wired or wireless network Focus of this lecture
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So far… So far… Abstract distributed system – collection of processes over a communication medium Protocols/algorithms for synchronization, snapshots, multicast, election, mutual exclusion, failure detectors Will work in any distributed group of processes 1. E.g., Group of processes on computer hosts 2. E.g., Group of processes on PDAs For most of this course, we’ll focus on (1): computer hosts over the Internet
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The Internet (Internet Mapping Project, color coded by ISPs) PCs,routers, switches… =nodes links= edges
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Internet 5-Layer Networking Stack Internet 5-Layer Networking Stack Messages (UDP) or Streams (TCP) Application Transport Internet UDP or TCP packets IP datagrams Network-specific frames Message Layers Underlying network Data Link Layer This is where all distributed algorithms/techniques run
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Routing Algorithms Routing Algorithms Nodes connected in some topology. Routing algorithm runs at network layer in each node. Goal of routing algorithm: given the destination IP address in packet, determine the “next hop” thus determine the route for each packet as it travels through the net, dynamically update routing information to reflect failures, changes and congestion. Two approaches: Distance-vector (e.g., RIP) Every node knows the next-hop for each possible destination LAN Link-state (e.g., OSPF) Every node knows status of each “link” in the network In both, information maintained as a table Tables updated either Proactively – periodically, or Reactively – when a neighbor/some link status changes NETWORK/INTERNET LAYER
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Distance Vector Routing Distance Vector Routing Also termed as distributed Bellman-Ford algorithm, included in RIP (Routing Information
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This note was uploaded on 02/08/2012 for the course ECE 428 taught by Professor Hu during the Spring '08 term at University of Illinois, Urbana Champaign.

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L19.sp11 - Distributed Systems Distributed Systems CS 425 /...

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