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.  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.  FLIP Box Software Layer OS corresponding to sites 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  Two parameters used N/w Weight 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