COMP1321 Digital Infrastructure Richard Henson March 2016

Week 18 – Thin Clients, Connectivity, Mixed Networks, and Virtualisation n Objectives  Explain levels of distribution in client-server networking, and relate the use of different levels to organisational requirements  Explain the process of terminal emulation and how terminal services and other software can deliver this to the desktop  Explain virtualisation and install a virtual machine

A matter of Fashion or Functionality? n Very early days of networking…  no clients… (or even users!)  specialist staff only »all computer input via cards and tape »output only to printers n Original clients (or VDUS) early 1970s, really were “dumb”!  microprocessor only just been invented!  interrupt driven processing hadn’t been implemented

The dawn of the “intelligent client” n First “8 bit” processor (Intel 8008) available in 1973…  two years to develop a motherboard & operating system »expected that “users” would write their own apps  1975, the first microcomputer: The Altair »scope for “intelligence on the desktop” n By 1981, microcomputers popular in the home…  IBM PC was introduced to see whether business would make use of desktop computing…

Success of the Business Micro n Businesses used the IBM micro  applications became commercially available  large organisations wanted to exchange data… »between desktops »between desktop and server n Through OSI & IEEE802 standards, the networked PC & LANs became possible:  centralised computers could interface with microcomputers  popular early implementations: n Novell Netware n DEC PCSA

Servers provide Services n In the early days, the server (host) was king  user device VDU (Visual Display Unit) or Terminal had no processing ability  everything controlled from the centre n Once microcomputers could connect to servers  host-VDU/terminal -> server-client  clients provided richer user experience n But, servers retained control  provided client access to resources via services

Client platforms n Environment for running software… e.g.  Intel motherboard etc./Windows 7  Intel motherboard etc./AppleOS  Smartphone/Android n Sometimes useful to be able to run more than one platform on a single machine.

Clients make services accessible to users… n Servers hold secure data…  should be kept well away from users! n Users can only access data/resources on a client-server network via a request to a server n Depending on the server architecture:  make requests directly via commands inputted from a dumb terminal  make requests from an intelligent client through interprocess communication

Virtual Machines n Replacement of an existing hardware/software platform by a platform that is solely software based n Virtual Machine still has to run on an existing platform e.g.  Intel/Windows 7/8/10 client  Apple client

Virtualisation Platforms n Software environment running on top of an existing environment n Allows more than one virtual machine to run on top of a traditional hardware/software platform n Client operating system installed on top of virtualisation platform

Examples: n VMWare n Virtual Box n Citrix n Hyper-V Hardware/software platform e.g. Intel/Windows virtualisation platform Virtual machine e.g. running Windows 10 Virtual machine e.g. running Server 2008

Virtualisation (Windows 2008 Server, Citrix, VMware, etc.) n The use of software to allow a piece of hardware to run multiple operating system images at the same time  Possible to run Windows OS under Mac OS  run multiple versions of Windows OS on the same PC n Enables the creation of a “virtual” (rather than actual) version of any software environment on the desktop, e.g. Operating Systems, a server, a storage device or networks, an application

“The Cloud” n Outsourcing on a grand scale…  With connectivity via world wide web n “Back to the Future”  Quote from IBM in 1950s: »“I think there is a world market for about five computers.” attributed to J. Watson  “The cloud” will behave like just one massive mainframe computer providing all user services  no FAT clients needed… just enough processing at the client end to run a browser »could be a very small device »could use wireless protocols to connect…

Web Services and The Cloud n Companies like Amazon, Google (apps), and salesforce.com have created web services (XML/http) and made them available to a wider public for storing their data  this approach benefits companies most that are experience relatively quick growth  instead of getting new storage resources every year, organisations can quickly and easily purchase more "cloud space"

Cloud Services, the future, and Security n Cloud computing can offer applications as-a- service as well…  a future is predicted where everything is outsourced and no kind of local CPU is even needed  employees will simply have a monitor, keyboard, and mouse that will allow them to connect to the cloud for all of their resources (!)  but will this be secure? And what comeback will organisations have if something goes wrong?

What (physically) is The Cloud? n Lots of servers connected together in clusters to provide different services via the www  Attractive and powerful, but…  disadvantages of outsourcing in terms of control »and with the extra challenge that the user doesn’t know where there data physically is at a particular time… SCARY? n Server location also a matter of some concern for legal reasons…

Thanks for listening Thanks for listening