Jaringan Informasi Pengantar Sistem Terdistribusi oleh Ir. Risanuri Hidayat, M.Sc.

Motivation ● Share resources ● Personalise environments ● Location independence ● People & information are distributed ● Performance & cost ● Modularity & expandability ● Availability & reliability ● Scalability

Goal ● Performance ● Reliability ● Scalability ● Consistency ● Security

Issues Design ● Naming ● Communication ● Software structure – well-defined interfaces – abstractions/layering & support services ● Scale ● Partial failure – detection, masking & tolerance – recovery Security ● Centralized systems: – can rely on physical security – Users understand what trust to assign to the system – System administrators are responsible ● Distributed systems: – None of the above applies ! – Hard to know what is being trusted or what can be trusted

Transparency ● Access ● Location ● Concurrency ● Replication ● Failure ● Mobility ● Performance – Reconfiguration – Scale

Definition Colouris ● System of networked computers that – communicate and coordinate their actions only by passing messages ● concurrent execution of programs ● no global clock ● components fail independently of one another Tanenbaum ● A collection of independent computers that appear to the users as a single coherent system – autonomous computers ● connected by a network – software specifically designed to provide an integrated computing facility

Definition Lamport ● “You know you have a distributed system when the crash of a computer you’ve never heard of stops you from getting any work done.” – inter-dependencies – shared state – independent failure of components ● partial failures

Clock dan Sinkronisasi

Server Cluster

Interaksi Peer to peer

Mobile Code Example: Applets

Thin Client-Compute Server Thin Client Application Process Network computer or PC Compute server network

IPC

Interaksi Client-Server Remote Procedure Call

Interaksi C-S ● Multi-tier

Interaksi C-S

● Asinkron RPC

Web ● TCP/IP ● DNS ● HTTP ● HTML ● Caching ● Server clusters

Layering Hardware Host-to-Host Connectivity Request-Reply Channel Message Stream Channel Application Programs

Protocol Graph

OSI Network Architecture Application Data Link Network Transport Session Presentation Physical Network Data Link Physical Network Data Link Physical -> raw bits Data Link -> frames Network -> packets Transport -> process-to-process Application Data Link Network Transport Session Presentation Physical

Internet Architecture Network IP TCPUDP Application Transport Datagrams Messages (UDP) Streams (TCP)

Encapsulation App Data RRPData HHP RRP App Data RRPData HHP RRP DataHHP