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Protocols For Distributed Systems

Protocols For Distributed Systems. Protocols used by network systems are not effective to distributed system Special requirements are needed here. They are in cases of: Transparency Client server based communication Group Communication Security Network Management Scalability.

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Protocols For Distributed Systems

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  1. Protocols For Distributed Systems

  2. Protocols used by network systems are not effective to distributed system Special requirements are needed here. They are in cases of: Transparency Client server based communication Group Communication Security Network Management Scalability Issues & Need of new protocols

  3. Transparency • Must be location independent because process can be migrated leading to change in identifiers Client server based communication • Must be Simple, Connectionless, support Request Response behavior Group Communication • Should support flexible transfer of n data n entities

  4. Security • Messages should be encrypted only if the path cannot be trusted because it is expensive Network Management • Adding & removing of node should be done automatically Scalability • Protocol should be scalable

  5. Introduction of Protocols • Two Communication Protocols are designed to achieve higher throughput & fast response in distributed system & to solve the issues mentioned • VMTP: Versatile Message Transport Protocol • FLIP:Fast Local Internet Protocol

  6. VMTP • Provides Group Communication , Security & efficient Client Server Communication • Connectionless protocol supports Request-Response behavior between Client & Server • Entities identified by 64-bit identifier which is unique, stable & independent of host address • Allows entities to be migrated & handled independent of network layer addressing

  7. Portion of entity identifier space reserved for group identifiers , identify a group of zero or more entities • VMTP provides Selective Transmission • Packets of message divided into packet group which contains maximum of 64 kilobytes of segment data(viewed as a sequence of segment block having 512 bytes • 32 bit mask in segment • When a packet is received , delivery mask ORed together to obtain a bit map

  8. VMTP uses a rate-based flow control mechanism • Packets in a packet group are spaced out with in for packet gaps to reduced the arrival rate at Receiver • Allows Client Server Communication • Optimization is used in VMTP -> differentiate between idempotent & non idempotent operations • Idempotent operation-> executions can be repeated no: of times without their being any side effect

  9. VMTP provides rich collection of optional facilities -> expands its functionality & efficiency in various site

  10. FLIP • Connectionless protocol used in AMEOBA Distributed Systems • Features are Transparency, Security, easy Network Management, Group Communication & C-S Communication • Identifies entities as Network Service Access Points(NSAP’s) with location independent 64-bit identifier • Sites on internetwork have more than one NSAP’s connected by a FLIP Box

  11. Software Layer OS corresponding to sites • FLIP Box Run on a separate communication process • Routing table is maintained-> dynamic cache mapping NSAP address on data-link address • FLIP messages are transmitted between NSAP’s • Path is selected on the basis of information stored in routing table of each FLIP Box N/w Weight • Two parameters used Security bit

  12. Three calls are provided in FLIP for sending messages • FLIP_Unicast • FLIP_Multicast • FLIP_Broadcast • Mechanisms provided for sending sensitive messages -> Security

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