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POP3協定

wpadmin — Tue, 28 Oct 2014 08:53:03 +0000

POP:Post Office Protocol :授權與下載

授權階段:
用戶端指令:user:宣告使用者名稱 pass:密碼
伺服器回應:+OK -ERR

存取程序階段,用戶端:
list:將訊息編號列表
retr:以編號收取訊息
dele:刪除
quit

Cloud applications

wpadmin — Fri, 20 Jun 2014 06:35:15 +0000

Cloud computing is very attractive to the users:
Economic reasons.
low infrastructure investment.
low cost – customers are only billed for resources used.
Convenience and performance.
application developers enjoy the advantages of a just-in-time
infrastructure; they are free to design an application without being
concerned with the system where the application will run.
the execution time of compute-intensive and data-intensive applications
can, potentially, be reduced through parallelization. If an application can
partition the workload in
n
segments and spawn
n
instances of itself, then
the execution time could be reduced by a factor close to
n
.
✒ Cloud computing is also beneficial for the providers of computing cycles -
it typically leads to a higher level of resource utilization.

Service Level Agreement (SLA)

wpadmin — Fri, 20 Jun 2014 06:31:55 +0000

SLA – a negotiated contract between the customer and CSP; can be
legally binding or informal. Objectives:
• Identify and define the customer’s needs and constraints
including the level of resources, security, timing, and QoS.
• Provide a framework for understanding; a critical aspect of
this framework is a clear definition of classes of service and
the costs.
• Simplify complex issues; clarify the boundaries between the
responsibilities of clients and CSP in case of failures.
• Reduce areas of conflict.
• Encourage dialog in the event of disputes.
• Eliminate unrealistic expectations.
• Specifies the services that the customer receives, rather than how
the cloud service provider delivers the services.

PaaS and SaaS services from Microsoft

wpadmin — Fri, 20 Jun 2014 06:31:04 +0000

Windows Azure
- an operating system; has 3
components:
• Compute – provides a computation environment.
• Storage – for scalable storage.
• Fabric Controller – deploys, manages, and monitors
applications.
•SQL Azure
- a cloud-based version of the SQL Server.
•Azure AppFabric
, formerly .NET Services – a collection
of services for cloud applications.

PaaS services offered by Google

wpadmin — Fri, 20 Jun 2014 06:30:35 +0000

AppEngine
- a developer platform hosted on the cloud.
• Initially supported Python, Java was added later.
• The database for code development can be accessed with
GQL (Google Query Language) with a SQL-like syntax.
•Google Co-op
- allows users to create customized search engines
based on a set of facets/categories.
•Google Drive
- an online service for data storage.
•Google Base
- allows users to load structured data from different
sources to a central repository, a very large, self-describing, semi
structured, heterogeneous database .

SaaS services offered by Google

wpadmin — Fri, 20 Jun 2014 06:30:09 +0000

Gmail
- hosts Emails on Google servers and provides a web
interface to access the Email.
•Google docs
- a web-based software for building text documents,
spreadsheets and presentations.
•Google Calendar
- a browser-based scheduler; supports multiple
user calendars, calendar sharing, event search, display of
daily/weekly/monthly views, and so on.
•Google Groups
- allows users to host discussion forums to create
messages online or via Email.
•Picasa
- a tool to upload, share, and edit images.
•Google Maps
- web mapping service; offers street maps, a route
planner, and an urban business locator for numerous countries
around the world

Elastic Beanstalk

wpadmin — Fri, 20 Jun 2014 06:29:46 +0000

Handles automatically the deployment, capacity provisioning, load
balancing, auto-scaling, and monitoring functions.
• Interacts with other services including
EC2
,
S3
, SNS, Elastic Load
Balance and AutoScaling.
• The management functions provided by the service are:
• Deploy a new application version (or rollback to a previous
version).
• Access to the results reported by CloudWatch monitoring
service.
• Email notifications when application status changes or
application servers are added or removed.
• Access to server log files without needing to login to the
application servers.
• The service is available using: a Java platform, the PHP server-side
description language, or the .NET framework.

AWS services introduced in 2012 _2

wpadmin — Fri, 20 Jun 2014 06:29:22 +0000

CloudFront
- web service for content delivery.
•Elastic Load Balancer
- automatically distributes the
incoming requests across multiple instances of the
application.
•Elastic Beanstalk
- handles automatically deployment,
capacity provisioning, load balancing, auto-scaling, and
application monitoring functions.
•CloudFormation
- allows the creation of a stack
describing the infrastructure for an application.

AWS services introduced in 2012

wpadmin — Fri, 20 Jun 2014 06:28:47 +0000

Route 53
- low-latency DNS service used to manage user’s DNS
public records.
•Elastic MapReduce (EMR)
- supports processing of large amounts of
data using a hosted Hadoop running on
EC2
.
•Simple Workflow Service (SWF)
- supports workflow management;
allows scheduling, management of dependencies, and coordination of
multiple
EC2
instances.
•ElastiCache
- enables web applications to retrieve data from a
managed in-memory caching system rather than a much slower disk-
based database.
•DynamoDB
- scalable and low-latency fully managed NoSQL
database service.

Examples of Amazon Web Services

wpadmin — Fri, 20 Jun 2014 06:27:08 +0000

AWS Management Console -
allows users to access the services
offered by AWS .
•Elastic Cloud Computing (EC2) -
allows a user to launch a variety
of operating systems.
•Simple Queuing Service (SQS) -
allows multiple
EC2
instances to
communicate with one another.
•Simple Storage Service (S3),Simple DB, and Elastic Bloc Storage (EBS)
- storage services.
•Cloud Watch -
supports performance monitoring.
•Auto Scaling -
supports elastic resource management.
•Virtual Private Cloud -
allows direct migration of parallel
applications .