Server / client (detail):
Client (computing):
-A client is a piece of computer hardware or software that accesses a service made available by a server. The server is often (but not always) on another computer system, in which case the client accesses the service by way of a network.
-The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network. These dumb terminals were clients of the time-sharing mainframe computer.
-Servers set up listening sockets, and clients initiate connections that a server may accept. Web browsers are clients that connect to web servers and retrieve web pages for display.
-Online chat uses a variety of clients, which vary depending on the chat protocol being used.
-Multiplayer online games may run as Game Clients on each local computer.
-Increasingly, existing large client applications are being switched to websites, making the browser a sort of universal client. This avoids the hassle of downloading a large piece of software onto any computer you want to use the application on. An example of this is the rise of webmail.
-In personal computers and computer workstations, the difference between client and server operating system is often just a matter of marketing - the server version may contain more operating system components, allow more simultaneous logins, and may be more expensive, while the client version may contain more end-user software.
Types clients:
There are three types of clients in a heterogeneous computing environment: diskless, dataless, and datashare.
1- A diskless client has no mass storage of its own. All file access is provided by the distributed file system. A diskless client boots, loads applications, and stores its data on servers.
2-A dataless client has only enough local mass storage to enable it to boot and perhaps, load applications. All of its data is kept on servers.
3-A datashare client can function more autonomously. It has some applications and some data stored locally but, at the same time, may have some data and applications stored remotely.
Server (computing):
In most common use.
-Servers often provide essential services across a network, either to private users inside a large organization or to public users via the Internet
In the context of client-server architecture,Client/server architecture products conform to a software-design model called client/server. Using the client/server model, you can place an application or client on one computer and the database server on another computer, but they can also be located on the same computer. Client applications issue requests for services and data from the database server. The database server responds by providing the services and data that the client requested
Hardware requirements for servers vary, depending on the server application.-
-Absolute CPU speed is not usually as critical to a server as it is to a desktop machine[citation [needed
-Servers' duties to provide service to many users over a network lead to different requirements such as fast network connections and high I/O throughput. Since servers are usually accessed over a network, they may run in headless mode without a monitor or input device.
Processes that are not needed for the server's function are not used.-
-Many servers do not have a graphical user interface (GUI) as it is unnecessary and consumes resources that could be allocated elsewhere. Similarly, audio and USB interfaces may be omitted.
-- Servers often run for long periods without interruption and availability must often be very high, making hardware reliability and durability extremely important.
-To increase reliability, most servers use memory with error detection and correction, redundant disks, redundant power supplies and so on .
-As servers need a stable power supply, good Internet access, increased security and are also noisy, it is usual to store them in dedicated server centers or special rooms
-Many servers take a long time for the hardware to start up and load the operating system.
Server Operating Systems:
Server OSes are designed from the ground up to provide platforms for multi-user, frequently business-critical, networked applications. As such, the focus of such operating systems tends to be security, stability and collaboration, rather than user interface.
Common applications for server Oses:
1-Application services (including databases)
2-Web site services
3-E-mail, groupware and messaging
4-Terminal services
5-Caching
Things to look for in a server OS:
1-Administration - what tools are available and how easy are they to use.
2-Security - perhaps the most important feature, and the hardest to judge and get right. In general, the more tasks a server performs, the more potential holes hackers have to get in.
3-Stability - downtime is an organisational killer
4-Features - does it have the specific services
5-Performance - is the server OS, and the hardware platform it runs on, fast enough for your needs?
6-Hardware requirements - whether the server OS can run on Intel or AMD hardware, or whether it requires a proprietary platform
7-Scalability - how many clients can reasonably access this system, and how far can the OS scale in the future (to new hardware or more processors, for instance) if needed.
8-TCO - how much the ancillary costs of the operating system are - in terms of productivity, administration and downtime.
9-Third-party applications - what products are available for the platforms that aren't covered by the basic set included in the OS.
Types of servers:
- Application server, a server dedicated to running certain software applications
- Catalog server, a central search point for information across a distributed network
- Communications server, carrier-grade computing platform for communications networks
- Compute server, a server intended for intensive (esp. scientific) computations
- Database server, provides database services to other computer programs or computers
- Fax server, provides fax services for clients
- File server, provides remote access to files
- Game server, a server that video game clients connect to in order to play online together
- Home server, a server for the home
- Name server or DNS
- Print server, provides printer services
- Proxy server, acts as an intermediary for requests from clients seeking resources from other servers
- Sound server, provides multimedia broadcasting, streaming.
- Standalone server, an emulator for client–server (web-based) programs
- Web server, a server that HTTP clients connect to in order to send commands and receive responses along with data contents
Networks server / client:
The simplest client/server network consists of a client computer networked to a server computer, with processing split between the two types of machines.This is called a two-tiered client/server architecture. Whereas simple client/server networks can be found in small businesses,
most corporations have more complex, multitiered (often called N-tier) client/server architectures in which the work of the entire network is balanced over several different levels of servers, depending on the kind of service being requested.
Components of Client Server Network
1- Workstations: Workstations are the computers that are subordinate to servers. They send requests to servers to access shared programs, files and databases, and are governed by policies defined by servers.
2- Servers: A server "services" requests from workstations and can perform many functions as a central repository of files, programs, databases and management policies.
3- Network Devices :- Network devices provide the communication path for servers and workstations. They act as connectors and route data in and out of the network
4- Other components like scanner,printer, etc can also be connected to network architecture.
: Features server
1-They have large storage capacity
2-They are able to provide information to many computers simultaneously, therefore have large RAM
3-Its processor speed is high, as it may have to execute multi-tasking too
DISADVANTAGES OF CLIENT-SERVER
1-Dependability - when the server goes down, operations cease
2-Lack of mature tools - it is a relatively new technology and needed tools are lacking
e.g.. Automated client software distribution
3-Lack of scalability - network operating systems (e.g.. Novell Netware, Windows NT Server) are not very scalable.
4-Higher than anticipated costs
5-Can cause network congestion
Local Client-Server Networks
Many home networks utilize client-server systems without even realizing it. Broadband routers, for example, contain DHCP servers that provide IP addresses to the home computers (DHCP clients). Other types of network servers found in home include print servers and backup servers.
Servers types: (Types of servers for local networks)
1-File Server
Is a computer with high specifications in speed and storage, processing and uses this type of servers in case files used by most of the members of the network
3-Data Base Server
4-Printer Server
5-Administration & Management Server
