4 Trends in Distributed Systems: Resuming & Foreseeing. Andrea Omicini ... [
Coulouris et al., 2012]) according to the personal view of the teacher of this
course.
Security Engineering: A Guide to Building Dependable Distributed Systems. 115
... access controls can be used to manage which principals can perform which .....
As you read through this book, you'll see that many other applications, from
burgl
Course Textbook George Coulouris, Jean Dollimore and Tim. Kindberg,
Distributed Systems: Concepts and Design. ▻ 4th Edition: http://www.cdk4.net/.
In this chapter, we discuss the general structure of distributed systems and the
networks that ... Load balancing and load sharing are discussed by [Harchol-
Balter and ... D. Comer, Internetworking with TCP/IP, Volume II, Third Edition,.
Prentice
Smart Cameras as embedded systems. • What is a smart Camera? • While
today's digital cameras capture images, smart cameras capture high-level ...
CUGS: Distributed Systems. 1. CUGS: Distributed Systems ... Architecture issues
(Coulouris et al., Ch. 2) ... Most real-time systems are distributed. ▫ Inherently ...
Web Server. Web Browser. HTML/HTTP. ASP .NET. SOAP/HTTP. WS Client add
your favourite here ... Like components, Web services can be reused, composed
into .... a text retrieval system or any other data management system providing ...
1 Middleware is Part of a Broad Set of Information Technology Trends ...
Middleware represents the confluence of two key areas of information technology
(IT): ...
directions, in an attempt to better understand the advantages and limitations of the DTM paradigm. The current ... are typically must shorter than in other transactional systems, ... between transaction processing time and replica coordination.
Classification of Operating Systems (cont.) ▫ “True” Distributed Operating System
. ○ Loosely-coupled hardware. ▫ No shared memory, but provides the “feel” of ...
transactions (i.e. proposals to make a new ledger entry), which get bundled ...... long-standing transaction malleability issues preventing the development of ...
Abstract. Computer system security is the fastest developing segment in informa- ... Honeypots are specialized devices aimed at slowing down or diverting ... define terms and develop adequate solutions cooperating with other security system.
Assume our distributed system is earth-based. h i i d fi d h h' i. Earth time is defined w.r.t. the ... What does âA h
a European project [6] and the symposium at Southampton [18]. Finally ... The driving force behind using Ada in distributed systems is the ability to create Ada programs that can be spread ... of using packages in this role, they list: It reuse of ..
Objectives. Study conceptual and practical aspects of distributed systems. ○.
Client-server model. ○. Distributed protocols. ○. Synchronous. ○.
Asynchronous.
possibilities and challenges for application design and deploy- ment. On-demand .... The challenges outlined above call for a methodology addressing the ... lenges such as multi-dimensional elasticity must be intrinsi- cally supported to ...
[email protected]. Distributed Systems Group, Information Systems Institute, Vienna University of Technology. Recommended by: Dimitrios ...
CS 213. Introduction to Computer Systems. Page 1 of 4. Distributed and Parallel
Systems. We have discussed the abstractions and implementations that make ...
to optimize the running costs and quality. In this paper, we outline our novel PaaS aiming at support- ing dynamic lifecycle development and execution of native.
cloud applications, including the whole application, application component, and within ..... refers to the cost of hosting the entire application. The programming ...
messages sent by the monitoring system or by the application processes. 2.2 The Interprocess Communication Protocol-Jipc. A Jade distributed system, or Jipc ...
â¢The purpose of the CORBA Naming service is to provide a basic mechanism by ..... â¢A distributed cinema ticketing system with which clients specify which movie ...
timesharing computers. Distributed systems ... Issues: Key distribution: How can
Alice send a shared key K. AB ..... [1] G. Coulouris, J. Dollimore and T. Kindberg,.
Distributed Computing Systems. 2. The Rise of Distributed Systems ... Definition:
a distributed system is. ▫ A collection of ... DOS (Distributed Operating Systems).
Distributed Systems REK’s adaptation of Prof. Claypool’s adaptation of Tanenbaum’s Distributed Systems Chapter 1 1
The Rise of Distributed Systems !
!
Computer hardware prices are falling and power increasing. Network connectivity is increasing. !
! !
Everyone is connected with fat pipes.
It is easy to connect hardware together. Definition: a distributed system is !
A collection of independent computers that appears to its users as a single coherent system. Distributed Computing Systems
2
Forms of Transparency in a Distributed System Transparency
Description
Access
Hide differences in data representation and how a resource is accessed
Location
Hide where a resource is located
Migration
Hide that a resource may move to another location
Relocation
Hide that a resource may be moved to another location while in use
Replication
Hide that a resource may be shared by several competitive users
Concurrency
Hide that a resource may be shared by several competitive users
Failure
Hide the failure and recovery of a resource
Persistence
Hide whether a (software) resource is in memory or on disk Distributed Computing Systems
3
Scalability Problems
!
Concept
Example
Centralized services
A single server for all users
Centralized data
A single on-line telephone book
Centralized algorithms
Doing routing based on complete information
As distributed systems grow, centralized solutions are limited.
Distributed Computing Systems
4
Hiding Communication Latency
•
This is especially important for interactive applications
•
If possible, system can do asynchronous communication.
•
The system can hide latencies. Distributed Computing Systems
5
Dividing the DNS name space into zones
1.5
Distributed Computing Systems
6
Hardware Concepts Basic organizations and memories in distributed computer systems
1.6
Distributed Computing Systems
7
Hardware Considerations !
General Classification: !
!
!
Multiprocessor – a single address space among the processors Multicomputer – each machine has its own private memory.
OS can be developed for either type of environment.
Distributed Computing Systems
8
Multiprocessor Organizations !
Uniform Memory Access [UMA] !
!
Caching is vital for reasonable performance (e.g., caches on a shared memory multiprocessor). Want to maintain cache coherency !
WriteWrite-through cache :: any changes to cache are written through to memory.
Distributed Computing Systems
9
Multiprocessors
1.7
A bus-based multiprocessor.
Distributed Computing Systems
10
Multiprocessors
A crossbar switch
An omega switching network
Distributed Computing Systems
11
Multiprocessor Organizations
!
NonNon-Uniform Memory Access [NUMA] !
!
A hierarchy where CPUs have their own memory (not the same as a cache). Access costs to memory is non-uniform.
Distributed Computing Systems
12
Replication !
Make a copy of information to increase availability and decrease centralized load. !
! !
!
Example: P2P networks (Gnutella +) distribute copies uniformly or in proportion to use. Example: CDNs (Akamai) Example: Caching is a replication decision made by client.
Issue: Consistency of replicated information !
Example: Web Browser cache Distributed Computing Systems
13
Software Concepts ! ! !
DOS (Distributed Operating Systems) NOS (Network Operating Systems) Middleware
System
Description
DOS
Tightly-coupled operating system for multi- Hide and manage processors and homogeneous hardware multicomputers resources
NOS
Loosely-coupled operating system for heterogeneous multicomputers (LAN and WAN)
Offer local services to remote clients
Middleware
Additional layer atop of NOS implementing general-purpose services
Provide distribution transparency
Distributed Computing Systems
Main Goal
14
Uniprocessor Operating Systems
!
Separating applications from operating system code through a microkernel !
Can extend to multiple computers Distributed Computing Systems
15
Network Operating System
! !
OSes can be different (Windows or Linux) Typical services: rlogin, rcp !
Fairly primitive way to share files Distributed Computing Systems
16
Network Operating System
!
Can have one computer provide files transparently for others (NFS) !
(try a “df” on the WPI hosts to see. Similar to a “mount network drive” in Windows) Distributed Computing Systems
17
Network Operating System
! !
Different clients may mount the servers in different places Inconsistencies in view make NOS’s harder, in general for users than DOS’s. ! But easier to scale by adding computers Distributed Computing Systems
18
Distributed Operating Systems
!
But no longer have shared memory ! !
Provide message passing Can try to provide distributed shared memory !
But tough to get acceptable performance Distributed Computing Systems
19
Distributed System as Middleware
Distributed Computing Systems
20
Positioning Middleware
!
Network OS’s are not transparent. Distributed OS’s are not independent of computers.
!
Middleware can help.
!
Distributed Computing Systems
21
Middleware Models ! ! !
! !
View everything as a file - Plan 9. Less strict – distributed file systems. Make all procedure calls appear to be local – Remote Procedure Calls (RPC). Distributed objects (oo model). The Web – distributed documents.
Distributed Computing Systems
22
Middleware and Openness
1.23
!
In an open middleware-based distributed system, the protocols used by each middleware layer should be the same, as well as the interfaces they offer to applications. ! If different, there will be compatibility issues ! If incomplete, then users will build their own or use lowerlayer services (frowned upon) Distributed Computing Systems
23
Comparison between Systems Distributed OS Multiproc.
Multicomp.
Network OS
Degree of transparency
Very High
High
Low
High
Same OS on all nodes
Yes
Yes
No
No
Number of copies of OS
1
N
N
N
Basis for communication
Shared memory
Messages
Files
Model specific
Resource management
Global, central
Global, distributed
Per node
Per node
Scalability
No
Moderately
Yes
Varies
Openness
Closed
Closed
Open
Open
Item
Distributed Computing Systems
Middleware -based OS
24
Client-Server Model
•
Use TCP/IP for reliable network connection. • This implies the client must establish a connection before sending the first request.
Distributed Computing Systems
25
Internet Search Engine
Distributed Computing Systems
26
Multitiered Architectures
!
Thin client (a) to Fat client (e) !
(d) and (e) popular for NOS environments Distributed Computing Systems
27
Multitiered Architectures: 3 tiers
!
Server may act as a client !
Example would be transaction monitor across multiple databases Distributed Computing Systems
28
Horizontal Distribution
!
Distribute servers across nodes !
!
E.g., Web server “farm” for load balancing
Distribute clients in peer-to-peer systems. Distributed Computing Systems
