Re: Fully parallel Scheme-based language w/ evaluator
- From: "Vzalamataz Portnoy" <nester@xxxxxxxxxx>
- Date: Thu, 16 Aug 2007 10:18:52 -0500
Yeah, what i was saying is meant to encourage the project. I have some kind
of a book, about the organization services architecure SOA, where Schema is
mentioned in the title. Seems to be a winning formula for a network of
conferencing in parallel. I'm working on aircraft to aircraft cell calls
for the majors. I get too much static on the line. I canb't understand
nothing either.. bon vitale
This is from Windows Server 2003 for Dummies. This book talks about using
Windows Server 2003 and networks in simple - and irreverent - terms. Nothing
is too highfalutin to be mocked, nor too arcane to state in plain English.
You'll find everything you need to know about Windows Server 2003 and
networking in here, so you'll be able to find your way around - without
having to learn lots of jargon or obtain an advanced degree in computer
science along the way.
We want you to enjoy yourself. If networking really is a big deal, it's
important that you be able to get the most out of it.
This book is designed so you can pick it up and start reading at any point -
like you might read a reference book.
In Parts I and II, networking basics are covered:
Concepts and Terminology in Part I, and The Design and Deployment of Network
Hardware in Part II.
In Parts III through V, you'll find ample coverage of:
Windows Server 2003 and Related Networking Topics.
Part III covers installation and configuration of Windows Server 2003,
whereas Part IV covers its Maintenance and Management.
Part V completes this picture with chapters on a variety of Troubleshooting
Topics.
Part 1 - 2 Networking Basics
Part 3 - 5 Windows Server 2003 and Related Networking Topics
Text's Chapters
Each chapter is divided into freestanding sections in which each section
relates to the chapter's major theme. For example, the chapter on installing
network interface cards, or NICs, contains the following collection of
information:
A description of a NIC and how it works
The various PC buses for which NICs are available
How to begin the installation process by documenting your current
configuration
How to insert a NIC into a PC
How to configure a NIC after it's installed in your PC
What to do when Plug and Play fails to live up to its promises
Troubleshooting techniques to try when NIC installation doesn't work on the
first (or second) try
Each chapter section supplies just the facts you need to make networking
with Windows Server 2003 easy to use.
How to Use This Book
This book works like a reference, so start with a topic that interests you.
Table of Contents
You can use the table of contents to identify general areas of interest or
broad topics.
Index
The index, however, is your best tool for identifying detailed concepts,
related topics, or particular Windows Server 2003 capabilities, tools, or
controls.
After you find what you need, you can close the book and tackle whatever
task you've set for yourself - without having to grapple with unrelated
details. However, you may want to work directly from the book to make sure
you keep things straight.
Never Worked on a Network
If you've never worked on a network before, it's a good idea to read Part
I - II Networking Basics, in their entirety.
Likewise, if you're new to Windows Server 2003, you might want to read all
of Parts III and IV. Otherwise, dig in wherever your fancy moves you!
Windows 2003 Help
This book occasionally suggests that you consult the Windows Server 2003
online help, printed manuals, and Resource Kit and even Microsoft's TechNet
CD for additional information. In most cases though, you will find
everything you need to know about a particular topic right here - except for
some of the bizarre details that abound in Windows Server 2003.
In addition, a whole world of Web information about Windows Server 2003 is
available on the Internet, and the Microsoft Web site at
http://www.microsoft.com/windowsserver2003/default.mspx is not a bad place
to start looking for such information.
How This Book Is Organized
The book is divided into six major parts, each of which consists of two to
seven chapters.
The Six Major Parts of Windows Server 2003 for Dummies
Part I: Laying the Network Foundation
Part I covers networking concepts and terminology, including the basics of
networked communications and what makes networks work - usually, some
magical combination of hardware and software.
Look here for discussions about networking terms and concepts, such as
client, server, protocol, and topology.
If you're not familiar with networks, this part should come in handy. If
you're already a seasoned networker, you can skip this part (and Part II).
Part II: Hooking Up the Hardware
Part II covers everything you need to know to build or extend a network or
simply to understand what's really happening on an existing network. It
starts with coverage of network design and layout principles, and continues
with a discussion of how to install and configure NICs in a PC.
After that, it examines the wiring that links network devices and talks
about how multiple networks can interconnect.
Part II concludes with a review of all the software components you're likely
to encounter on a Windows 2003-based network and why you need them.
Part III: Servers, Start Your Engines!
Part III tackles Windows Server 2003 head on, starting with its installation
and configuration. It covers the issues involved in installing and
configuring network hardware specifically for Windows Server 2003.
It also covers how to install and manage print servers and services on a
Windows 2003-based network, how to handle Transmission Control
Protocol/Internet Protocol (TCP/IP) addresses, and how to set up and manage
directory services, domains, and trust relationships in a Windows 2003-based
environment.
Part III is where you figure out how to put the basic pieces of a network
together using Windows Server 2003.
Part IV: Running Your Network
Part IV picks up where Part III leaves off - that is, it talks about living
with and managing a Windows 2003-based network after the initial
installation and configuration phase is complete.
Part IV begins with a discussion of how to manage users and groups on a
Windows 2003-based network, including details on profiles, policies, and
local and global groups.
Next, it covers how Windows 2003 controls access to NTFS files and
directories, and how to manage network-accessible file system resources
called shares.
After a network's users, groups, and data assets are in place, rebuilding
such a setup from scratch can be a real pain. That's where a backup comes
in handy, so Part IV covers the ins and outs of backing up and restoring a
Windows Server 2003 machine, plus other aspects of fault tolerance.
Lastly, a review of network security principles and practices should help to
prepare you to protect your data from accidental loss and from would-be
hackers and crackers.
Part V: Troubleshooting
Part V takes a long, hard look at the common causes of trouble on Windows
2003-based networks and explores those areas that are most likely to fall
prey to trouble. It begins with a look at some key Windows 2003 tools for
troubleshooting systems, and then continues on to explore tips, tricks, and
techniques for troubleshooting a Windows 2003-based network.
Part V concludes by exploring the handling of problems with Active
Directory.
Part VI: The Part of Tens
Part VI follows the grand tradition of For Dummies books, all of which
include "The Part of Tens." Here, you'll find lists of information, tips,
tricks, and suggestions, all organized into short and convenient chapters.
This supplemental information is designed to be both helpful and informative
and is supplied at no extra charge.
Beginning the Notes for Windows Server 2003 for Dummies
Concepts and Terminology
Part I: Laying the Network Foundation
Part I covers networking concepts and terminology, including the basics of
networked communications and what makes networks work - usually, some
magical combination of hardware and software. Look here for discussions
about networking terms and concepts, such as client, server, protocol, and
topology.
If you're not familiar with networks, this part should come in handy. If
you're already a seasoned networker, you can skip this part (and Part II).
Chapter 1 - Making Networks Make Sense
Chapter 2 - Networking the Client/Server Way
Chapter 3 - Matters of Protocol
Chapter 4 - My Kingdom for a Topology
In this introductory part of the book, you get background material about
local area networks, or LANs. We present the barest essentials: how
computers communicate with each other, why communication isn't a bad thing,
and what makes networks work.
We also cover vital concepts, including protocols, which are the rules of
communication that computers use to exchange information, and topologies,
which are the ways in which network wiring can be arranged.
Along the way, you discover all kinds of basic network terminology and
concepts that you must know when you work with Windows Server 2003.
Introduction
If you've ever used a cell phone or watched a TV show, you've used a
network, perhaps without even realizing it. The world's modern
communications infrastructure, including wired and wireless telephones,
cable and broadcast TV, and the Internet, depends on networks. Windows
Server 2003 needs a network, too. Using Windows Server 2003 without a
network is like using a telephone that's not plugged into the wall. Its
real value comes from its capability to connect you with other people or
services.
Servers exist to provide file, print, directory, Web, security, and other
services to clients across a network.
The main components governing a LAN configuration are usually centered on
the different types of computer which make up the network, the manner in
which the computers are linked, the network technology employed and the NOS.
How the computers are linked and their prospective roles or tasks within the
network depends on the network configuration.
Four possible configurations are:
File Server Network - in a file server network composed of PCs, the
applications and data are usually stored on the server computer. The bulk
of the processing is done on the PCs/nodes.
A computer which takes on the role of a file server is usually a machine
which carries out specialist network tasks. These specialist tasks can
include the role of say, 'banker', whereby the server computer is dealing
application software to the various terminals or nodes, as well as
supporting the NOS and thereby controlling the flow of data around the
network.
With a file server network, the actual server usually supplies a range of
different applications which all the individual nodes can access. Each
individual node then processes its ovn data in conjunction with the
particular application it is using.
Client/Server Network - in a client server network processing can be shared
between the computers.
Client/server computing is nothing new. It has been around for quite some
time. Basically it involves splitting database processing among two or ore
processes - one on the client and the other on the server. Sometimes both
processes execute on the same computer, but having the processing occur o
two different processors is more common because of the increase in
performance.
In the client/server model, the client (also called the front end) provides
the user interface, receives input from the user, processes it, and then
sends a request to the database server over the network. The server (also
called the back end) is the program that receives the database request,
processes it and returns the requested information to the client (and to the
user).
A client process sends requests to a server process, which responds to the
requests. The client process, free from the overhead of processing the
transactions (data processing), can do other things. The processing between
the client and the server is cooperative, meaning that the client is
proactive and the server is reactive. This way of operating is primarily
what distinguishes the client/server paradigm from other models, such as the
older centralized database access model that most mainframe systems support.
Usually the client communicates with the server over a network, such as
Ethernet or Token Ring, by using a communications protocol such as TCP/IP,
Named Pipes, or IPX/SPX. With the new networking technology, databas
servers and clients can be as close, or as far away from each other as
needed. The concepts remain the same.
The software that sits between the application and the database is known as
middleware. Middleware is any software that facilitates the connection
between the client and the server. As client/server application use has
increased, so has interest in middleware. ODBC is an example of a
middleware product. Middleware provides a flexible and cost effective
method of obtaining a remote database connection. See Chapter 27 of Windows
3.1 Connectivity Secrets.. pps. 823 -835. ODBC is middlewarethat provides
connectivitybetween windows applications that run on PCs and existing data -
no matter what format the data is stored in or on what platform the data
resides.
For example, as a developer you can create a Windows application that is
able to seamlessly access enterprise services auch as databases, mail,
shared calendars, or remote procedure calls. It would need to be a service
which is WOSA-compliant (Windows open service architecture). A single API
communicates with all services, making your application development efforts
much less complicated.
LOWER LEVELS OF SYSTEM (DBMS and File Storage)
A computerized information storage and retrieval system will allow users to
work with a DBMS, which allows for record addition, record deletion, and
record update. Also permitted are file update procedures using record
importing from other files or applications.
An overview of IDC Web databases and their components would be as follows:
IIS (Microsoft Information Server)
Installed on an NT Server
Web server and database connector component
ODBC (Open Database Connectivity) Driver
Installed on the NT Server
Interface between IIS and thge Access 97 database
IDC (Internet Database Connector) Files
contain the SQL query information, etc. that IIS uses
HTX (HTML extension) files
Contain formatting tags and database field placeholders
IIS merges the result of the IDC query file with the formatting
instructions of the HTX file and returns HTML code
In client/server networks the relationship betwen the node or client
computer and the server is much more subtle. The client computer accesses
the server's applications but the processing is usually shared between the
client and the server. Client /server networks are more likely to be found
in a corporate environment. In addition, the niodes have more often than
not access to very process-intensive applications. As a result,
client/server networks usually employ minicomputers or mainframes as the
server. One particular computer, the IBM AS400 has proved to be the market
leader as a server computer in contemporary client/server systems.
Mainframe Network - a terminal/node on a mainframe network may, in some
situations, contain practically no processing facilities. In this type of
network the node is just a window on the central computer. In the diagram
all the processing and data storage is done by the mainframe. The node
simply calls up the required services as/when needed.
Mainframe servers can act as pivotal data stores or provide necessary
processing facilities. The structure of the network will determine the type
of computer employed as a server, and the tasks such as data processing
which it will perform.
The server is generally a dededicated machine, and is not used for anything
else.
Peer-to-Peer Networking - with a PC peer-to-peer network, the other nodes on
the network simply access that node which has the required information.
Peer-to-peer computing has become increasingly popular, within the PC
computer market. The nodes access each other for the required applications
or service. This strategy is a common concept with PC LANs, whereby the
computers use each other's hard disk for the required application or share
common peripheral equipment such as printers.
Linking coputers in a peer-to-peer network is more straight forward than
linking is for file server networks. The reason is there is no central
server to which all of the computers have to connect. The PC computers can
connect to the network cable at any convenient point. With sites and
buildings being in the shapes that they are, this can prove to be a
considerable saving of wiring expense.
Three-tier Client/Server Network - the main difference between this
configuration and a conventional client/server system is that the bulk of
the management software execution which details the processing tasks as
conducted between client and server is performed, by an intermediate server
computer. Although this is an expensive option it appears to minimise
processing management problems.
In this chapter, we introduce you to the various components that make up a
Windows Server 2003-based network and briefly discuss how each one works.
What's This about a Network?
A network requires at least two computers linked in a way that enables them
to talk to each other.
Most networks use electrical wires of some type to convey signals and data
between computers. However, numerous types of networking media, including
wireless technologies and fiber-optic cables, also support networked
connections.
A network's key ingredients always include some type of physical connection
that allows computers to talk (and listen) to some kind of communications
medium. Even if the network medium is wireless, something must physically
connect computers to an antenna or to a similar device that allows those
computers to broadcast and receive signals.
Cables and connections are essential, but they are purely decorative and can
serve no useful purpose without software.
No hardware means no connections!
Networking requires working connections to enable computers to communicate
with each other. Networking hardware creates connections between computers
and a network and defines the medium (or media) that allows information to
flow from sender to receiver.
Network Devices
Hardware plays an important role in networking. Not only does it attach
computers to a network, but it also interconnects multiple networks to
manage how and when data flows from one network to another. From the most
basic perspective, computers need the following hardware to talk to each
other on a typical network:
A network interface card (NIC) plugs into a computer and attaches to a
network cable (or other medium, if something else is used). It turns
computer bits into signals on the wire for outgoing stuff and turns incoming
signals into bits for incoming stuff.
Connectors make it possible to attach a network interface to the network
medium. For wireless media, connectors attach antennas or other broadcast
devices to interfaces. Connectors bring all the separate pieces of
networking hardware together, so to speak.
Cables convey signals from sender to receiver, using either electrical
signals for wire cables or light pulses for fiber-optic cable. In the case
of wireless media, the medium consists of the broadcast frequencies used to
transmit information between senders and receivers.
Additional network devices tie bigger, more complex networks together. These
devices range from relatively simple hubs used to interconnect interfaces on
star-wired networks (see Chapters 4 and 7) to repeaters used to link
individual cable segments, as well as bridges, routers, and gateways (see
Chapter 7).
A simple view of networking
Networking boils down to these three critical requirements:
-
Connections include the necessary hardware to connect a computer to a
network, plus cables (called the network medium) that ferry messages between
computers. The hardware that hooks a computer to a network is called a
network interface. In most cases, attaching a PC to a network requires
inserting an adapter board called a network interface card (NIC). Without a
physical connection, a computer can't use the network.
One of networking's primary advantages is that a network takes what you do
at your desk - and lets you do what you do more efficiently by allowing you
to interact with remote resources and data. This means you can access a
file on a server as if it's part of your own disk drive, send a job to a
printer elsewhere on the network as if it were hooked directly to your
machine, and so on.
Sharing resources remains the most highly touted benefit of networking
because it connects your desktop computer to file stores, printers,
applications, and information resources that would otherwise be inaccessible
or too expensive to add to every desktop computer.
IP Addresses
When addressing a network, poor addressing contributes to almost all
large-scale network failures. Why? Because routing stability (and the
stability of the routers) is directly tied to the number of routes
propagated through the network and the amount of work that must be done each
time the topology of the network changes.
Both of these factors are impacted by summarization, and summarization is
dependent on addressing (see Figure 2-1). See the section "IP Addressing and
Summarization" later in this chapter for an explanation of how summarization
works in IP.
Directed broadcasts are often used with network operating systems that use
broadcasts for client-to-server communications. A directed broadcast can be
generated using an IP helper address on the interface of the router to which
the workstations are connected.
The issue of network broadcasts is not clear in my thinking, yet the
summarization of traffic seems to be the opposite of what a broadcast would
be. These issues have to be clarified.further, of course.
The ISO model does not bind any particular network standard, such as TCP/IP
to the model. The ISO bases the layers on their function, rather than
specific existing network standards, and the model is therefore open,
robust, and suitable to be used to explore existing network specificatons
and to design the standards of the future. Used in this way, we have a
starting point for our definition of a network which allows us to build up
the components we need to create a network which does what we want. From a
development standpoint, defining the networking based upon a layered model,
allows for the development of new technologies that take advantage of
existing hardware and software by using underlying layers that are already
in place.
Where these services are connected depends on network topology issues (such
as addressing and redundancy, which will be covered in Advanced IP Network
Design (CCIE Professional Development) Chapters 2 through 4 in more detail),
traffic flow, and architecture issues.
We can have application servers which connect to the periphery and also to
the data integration and common services, such as mainframes and server
farms, where most data storage would be placed. In the case of connections
to external routing domains, it's almost always best to provide a buffer
zone between the external domain and the network core.
Devices in the core should have enough routing information to intelligently
switch a packet destined to any end device in the network; core routers
should not use
default routes to reach internal destinations (the local network). However,
this doesn't mean a router in this layer should have a path to each
individual subnet in every corner of the network. Summary routes can, and
should, be used to reduce the size of the core routing table. Default routes
should be used for reaching external destinations, such as hosts on the
Internet.
Essentially what is being considered in the paragaph above is the issue of
wiring, within the Data Link Layer. The routers are the connection to the
Physical Layer. The routers are used to move data (in packets) across the
network. And the Data Link provides the necessary logic needed to transmit
information to different nodes on our network.
Other common services, such as mainframes and server farms, are often
connected more directly to the core.
The mechanics of requesting resources depend on having access to the right
software tools to determine when network requests are necessary. The
software delivers the request to a server whose job is to listen for such
requests and to satisfy all legitimate ones. Ultimately, a server's job is
to make resources available to all authorized users. This feature makes
sharing possible and helps explain the most powerful benefit of networking -
namely, to provide a single, consistent way for multiple users to obtain
secure and managed access to files, printers, scanners, data, applications,
and more.
Network Addressing
A node is any device that is connected to a network. For our purposes, it
usually refers to a computer.
Networks are not isolated entities. A network can consist of many nodes,
using many different hardware layers and Data Link Layers. The Network
Layer provides the necessary addressing scheme to let one network
communicate with another. For heterogenous networks to exist, there must be
a common way of identifying nodes at a higher level. The Network Layer
provides this addressing scheme.
Because network components can vary widely, how would one network
communicate with another? At the Data Layer, a low-level addressing scheme
identifies individual nodes and is specific to the hardware underneath it.
For heterogenous networks to exist, there must be a common way of
identifying nodes at a higher level. The Network Layer provides this
addressing scheme.
Once a common addressing method is available, we need to worry about the
most efficient way to communicate between our different networks. An simple
network arrangement each distinct network - subnet will have a single
connection to each other. A typical university or business setting has
hundreds of individual subnets.
Moving data efficiently and reliable between the subnets is often a
monumental task and is referred to as routing.
The Network Layer is used to find the best route to take. Each node in each
subnet must know that, if necessary it can send information over an
alternative route, which will deliver it as well as a primary route.
The Transport Layer takes information to be sent, and breaks it into
individual Datagrams that are sent and reassembled into a complete message
by the Transport Layer at the receiving node. The Transport Layer may also
supply a signaling service for the remote node (time-stamp) so that the
sending node is notified when its data is received successfully by the
receiving node. Many types of data errors are handled by the Transport
Layer.
Addressing Subnets
In a peer-to-peer network, any machine that can be a client can also act as
a server. Unlike client/server networks, no special purpose machine acts as
a server. On a peer-to-peer network, all machines are more or less alike in
capability and in the services they offer. If you use the built-in
networking included in Windows XP Professional, Windows 2000 Professional,
Windows NT Workstation, or Windows 95, 98, SE, or Me, you're using this type
of networking software.
Figuring out whether a network is functioning is both easy and hard, and
most observers, including novices and experts alike, agree that telling when
a network's not working is easier than telling when it is! A client must
know how to ask for services from the network and must state precisely what
it's requesting. Likewise, a server must know how to recognize and evaluate
incoming requests for its services and how to respond appropriately. Only
then can a network work correctly.
Understanding how this constant stream of requests and replies works means
looking a little deeper into how clients state their requests and how
servers satisfy them. In the following sections, we examine the mechanics of
this give-and-take.
Knowing how to ask for network services requires some ability to distinguish
between what's available locally on a client machine and what's available
remotely from the network. Determining what's local and what's remote is the
key to handling network access correctly. This determination depends on
specialized software to handle the job in the background, so users don't
necessarily have to know the difference.
Most modern operating systems include built-in networking capabilities to
augment their control over local resources and devices.
Certain modern operating systems can be called network operating systems
(NOSs) when they create network server environments. Their built-in
networking capabilities include a range of network services as part and
parcel of the underlying operating system. Windows Server 2003 certainly
fits this bill because it offers a broad range of powerful, flexible
networking capabilities.
In Windows Server 2003, Windows XP Professional, Windows 2000, Windows NT,
Windows 9x, Macintosh, and UNIX operating systems, and through add-ons to
DOS and Windows 3. x, a special piece of software known as a redirector
keeps track of what's local and what's remote when users or applications
request resources. The redirector takes generic requests for services and
sends any that can't be satisfied locally to the appropriate service
provider elsewhere on the network (in other words, to the appropriate
server). Therefore, if you ask for a file that resides on a server elsewhere
on the network, the redirector hands your request off to that machine and
makes sure that the results of that request are delivered properly.
Right out of the box, Windows Server 2003 understands the differences
between local and remote resources. The same is true for most modern desktop
operating systems, including Windows XP Professional, Windows 2000 Server
and Professional, Windows NT Server and Workstation, Windows 9x, the
Macintosh OS, as well as that old (but still modern) warhorse, UNIX.
E-mail clients and Web browsers represent good examples of applications with
sophisticated, built-in networking capabilities. On the other hand, file
system access tools, such as Windows Explorer, My Computer, and My
Documents, rely on the redirector to furnish them with views of (and access
to) shared files and printers elsewhere on the network.
For a computer to use network services, the computer must know how to ask
for them. That's what a requester does. But knowing what to ask for is as
important as knowing how to ask. In most cases, applications supply the
necessary information about network services that they want to access,
either through information supplied from a requester or through knowledge
built directly into an application itself.
Please note that applications with built-in networking knowledge offer
transparent access to network services because the applications know how to
ask for services and, often, what to ask for on the user's behalf.
Programmers design such computer applications to be transparent to keep the
applications out of sight and out of mind; therefore, the user remains
blissfully unaware of cumbersome networking details and trivia.
But File managers, printer controls, and other tools with access to both
local and remote resources, however, require users to be able to tell the
difference between what's local and what's remote. In fact, such tools
usually force users to request access to remote resources explicitly and
directly.
Increasingly, finding out which services a network can provide is becoming
more and more implicit. This is why all editions of Windows Server 2003
support a set of directory services to catalog and describe the services
that the network can deliver to its users.
Windows Server 2003 all versions also support the Distributed File System
that allows directories on multiple machines all around a network to appear
as a single network drive to users. Therefore, users don't have to know
where individual files or folders reside. Perhaps this is by the
integration of AD and DNS. Read O'Reilly Acive Directory Services.
Such sophisticated mechanisms make it easier than ever before for users to
request and access resources implicitly without having to know how to
request those resources or having to determine exactly where they reside.
Nevertheless, some explicit knowledge about such things is necessary if you
want to make the most of Windows Server 2003's networking capabilities.
Sharing Resources
The mechanics of requesting resources depend on having access to the right
software tools to determine when network requests are necessary. The
software delivers the request to a server whose job is to listen for such
requests and to satisfy all legitimate ones. Ultimately, a server's job is
to make resources available to all authorized users. This feature makes
sharing possible and helps explain the most powerful benefit of networking -
namely, to provide a single, consistent way for multiple users to obtain
secure and managed access to files, printers, scanners, data, applications,
and more.
The secret to sharing is to find a way to make sure that everyone can obtain
access to a shared resource. For example, for access to print services, a
temporary storage space must hold incoming print jobs until each one's turn
to be printed comes up. Therefore, sharing a printer means not only
providing access to the device itself, but also keeping track of who's in
line, providing a place where pending jobs can reside, and sometimes
notifying users when a print job has
been successfully completed. All these mechanisms make sharing work easier
and explain why servers are so important to any network
Because servers bring services and data together in a single machine,
servers provide a natural point of control and maintenance for the important
devices, services, and data on a network, which are, of course, the things
that everybody wants to share.
Windows Networking Trends
Microsoft is leaping into a new era in which local networking and Internet
access is integrated unlike ever before. Windows Server 2003 is Microsoft's
next step toward a goal of end-to-end communication structures that enable
companies and individuals to electronically communicate easily, efficiently,
and securely. Windows Server 2003 is built on technology from Windows 2000,
which in turn was built on technology from Windows NT. The Windows Server
2003
family embraces serveral types of servers, including the following:
Windows Server 2003 Web Edition - a server system optimized for web serving
and hosting. This edition supports up to four (4) processors and 2 gig
bytes of RAM memory, per computer.
Windows Server 2003 Standard Edition - a server designed to replace Windows
2000 server. It can be used as a member server or as a domain controller on
small to medium sized networks. Supports up to four (4) processors and 4
gig bytes of RAM memory, per computer. This Edition is also the subject of
the book Windows Server 2003 for Dummies.
Windows Server 2003 Enterprise Edition - this is similar to the Windows
Server 2003 Standard Edition, but it has lots of bells and whistles. It
allows you to use up to 8 CPUs and 32 gig bytes of RAM memory, on a single
server. It supports 8 node clustering (combinines the computers in such a
way that they all share the workload to support a single large application
or network service.
Windows Server 2003 DataCenter Edition - This is a high-end Windows
operating system that supports even more CPUs and RAM than Windows Server
2003, Enterprise Edition (up to 64 CPUs and 64GB of RAM). It has the same
features as the Enterprise Edition, plus more. Windows Server 2003,
Datacenter Edition can support more than 10,000 simultaneous users in
certain situations and up to eight-node clustering.
Although these versions given above vary, they're more alike than different.
Therefore, this book can help you master the basics for any of these types
of Windows Server 2003 products.
Based on the capabilities of Windows Server 2003, we see the following
trends emerging for Windows networking in this millennium:
Use of Active Directory - Active Directory is Microsoft's name for the
directory services supported by Windows Server 2003. Active Directory makes
it easier for users to identify and access network resources and for
applications to use such resources directly and automatically. Currently,
you can't see much evidence of this capability, but it will change the way
we use Windows - and networks - in the future.
Access to Dynamic Disk Storage - Windows Server 2003 supports a variety of
sophisticated directory-sharing technologies. Dynamic disk storage enables
network administrators to define collections of files and directories
gathered from multiple servers around a network and present them to users as
if the files and directories reside on a single network drive. This makes
creating, identifying, and accessing collections of shared files easier.
Consistent Naming Services - Part of locating resources on a network is
knowing their names (or how to find them). Windows Server 2003 uses a single
enhanced method to translate human-intelligible names for network resources
into computer-intelligible network addresses, which makes managing and
interacting with network resources far simpler.
Web-based Management Console - In Windows Server 2003, a single Microsoft
Management Console (MMC) plays host to management tools (called MMC
snap-ins) for all system services, resources, and facilities. This console
makes the Windows Server 2003 interface simpler and its many capabilities
more visually consistent and therefore easier to learn and manage. In fact,
this capability works on any computer with a suitable Web browser (and an
administrative password).
Simplified Web-content Creation and Delivery - One of the primary goals of
the Windows Server 2003 family is to bring high-end, high-profit Web
services and applications to end users (that is, customers) in an efficient
manner. Through the use of optimized Web tools, new programming language
structures, and content development architectures, Windows Server 2003 is
poised to revolutionize how enterprise Web sites are created, deployed, and
maintained.
As all these capabilities are used, the trends in Windows networking should
be clear:
Easier, more straightforward access to all network resources.
Simplified administration and management of such resources.
More sophisticated tools and techniques to describe, deliver and control
network resources.
Client/Server Networking
As mentioned in the earlier section, it's all about sharing resources. For
most applications, using Windows Server 2003 in a networked environment
means buying into the client/server model. To help you understand this
networking model, which best explains why it's necessary for Windows Server
2003 to exist, we explore the client/server model in detail in this chapter.
Along the way, you discover more about the types of capabilities and
services that make client/server networks work and the various ways that
clients and servers interact on such networks.
What happens when a client requests a service from a server?
There is a three-part simple model for networking, which requires that
connections, communications, and services all be available and working.
The software on the client computer handles the communications and services
necessary for the network to operate. Here's a list of software that you
normally find on a networked client computer, starting from the hardware
level (or as close as software can get to hardware) and working up to the
applications that request network services.
Servers Deliver Services
The software on the client computer handles the communications and services
necessary for the network to operate. Here's a list of software that you
normally find on a networked client computer, starting from the hardware
level (or as close as software can get to hardware) and working up to the
applications that request network services.
The listener process checks the identity and the associated permissions of
the client, and if the client is who it says it is and has the correct
permissions for the service, the listener process grants the request for
service.
It does so by starting a temporary process (called an execution thread in
Windows-speak; think of this as a very small program) that exists just long
enough to handle whatever service the client requests - after which, the
temporary process (execution thread) disappears.
What usually happens on most server operating systems - including Windows
Server 2003 - is that the listener process simply recognizes that a request
has arrived.
For example, a request for a particular file on a server would result in the
creation of a temporary process that exists just long enough to copy the
requested file across the network. As soon as the copy completes, the
temporary process (thread - no longer executing) goes poof.
Using a listener process to create short-lived execution threads allows a
server to handle large numbers of requests, because the listener process
never stays busy for long handling individual requests. As soon as the
listener process creates a thread to handle one request, it checks for other
pending requests and handles them if necessary; otherwise, the listener
process goes back to listening for new incoming requests. Typically, a
server has one or more listener processes for each service that the server
supports.
Request/Reply Architecture
Servers are demand-driven. That is, their job is to respond to requests for
services from clients. A server rarely initiates activity. This reactive
mode of server operation helps explain why the client/server model is also
known as a request/response or a request/reply architecture, in which
clients make requests and servers respond or reply to them.
Software - Clients Request Services
The software on the client computer handles the communications and services
necessary for the network to operate. Here's a list of software that you
normally find on a networked client computer, starting from the hardware
level (or as close as software can get to hardware) and working up to the
applications that request network services.
Network driver: A special-purpose piece of software that enables a computer
to send data from the computer's central processing unit (CPU) to the NIC
when an outgoing message is ready to be sent. The network driver also
forwards a request for immediate attention (called an interrupt) to the CPU
when an incoming message arrives. You might say that the driver allows the
PC to communicate with the NIC, which in turn communicates with the network.
Protocol stack: A collection of communications software that provides the
type of "shared language" necessary for successful networking. The protocol
stack governs which formats network messages can assume, and it defines a
set of rules for how to interpret their contents. Two computers must use the
same protocol stack to communicate. We cover protocol stacks throughly in
Chapter 3.
Redirector: A redirector, or equivalent software, issues requests for remote
resources or services to the protocol stack and receives the incoming
replies from the protocol stack. With a redirector running in the
background, applications don't need to be explicitly network aware, because
the redirector handles network connections.
Network-aware application: Network-aware applications understand when
service requests can be satisfied locally or must be satisfied remotely. In
the latter case, a redirector may be present, but it may not necessarily
handle certain types of network services (such as e-mail or Web-page
access). However, the redirector can handle other types of network services,
such as providing access to a file stored elsewhere on the network that's
applied as an attachment to an e-mail message. In such a case, the
redirector grabs a copy of that file across the network and attaches it to
the outgoing e-mail message.
When a client makes a request for a resource or service that requires access
to the network, either the application (if it's network aware) or a
redirector (if the application isn't network aware) formulates a formal
request for a remote service. Satisfying the request may involve the
transfer of a small amount of data (as when requesting a listing of a
directory on a machine elsewhere on the network). However, it may also
involve transferring a large amount of data (as when sending a large file
off to be printed or when copying a large file from the client machine to a
server). The request is ferried through the protocol stack that the client
and server have in common. For short requests, a handful of short messages
travel from the client and are reassembled and handled by the server. For
large information transfers, the client breaks up the file into hundreds or
thousands of small information packages, each of which is shipped across the
network separately and then reassembled on the receiving end.
KEY CONCEPT The protocol stack tells the network driver to send little
packages of data (called frames or packets) from the computer, through the
NIC, and across the network to the intended recipient (the server). On the
receiving end, the same thing happens in reverse, with a few additional
considerations that you find out about in the following section.
Servers Deliver Services
In the preceding section, you found out that clients ask for services and
that servers provide them. What handling requests on the server side really
means is that a special bit of software, called a listener process, runs
continuously on the server and listens for requests for a particular
service. When a request arrives, the listener process handles it as quickly
as possible.
Servers thread through a maze of requests
What usually happens on most server operating systems - including Windows
Server 2003 - is that the listener process simply recognizes that a request
has arrived. The listener process checks the identity and the associated
permissions of the client, and if the client is who it says it is and has
the correct permissions for the service, the listener process grants the
request for service. It does so by starting a temporary process (called an
execution thread in Windows-speak; think of this as a very small program)
that exists just long enough to handle whatever service the client
requests - after which, the temporary process disappears. For example, a
request for a particular file on a server would result in the creation of a
temporary process that exists just long enough to copy the requested file
across the network.
As soon as the copy completes, the temporary process goes poof! Using a
listener process to create short-lived execution threads allows a server to
handle large numbers of requests, because the listener process never stays
busy for long handling individual requests. As soon as the listener process
creates a thread to handle one request, it checks for other pending requests
and handles them if necessary; otherwise, the listener process goes back to
listening for new incoming requests. Typically, a server has one or more
listener processes for each service that the server supports.
KEY CONCEPT Servers are demand-driven. That is, their job is to respond to
requests for services from clients. A server rarely initiates activity. This
reactive mode of server operation helps explain why the client/server model
is also known as a request/response or a request/reply architecture, in
which clients make requests and servers respond or reply to them.
Other than the necessary listener processes and a set of service
applications that actually perform services, servers need the same hardware
components that clients do. Servers need one or more NICs with a working
connection to the network to allow data to enter and leave the server.
Software is similar on the server side
On the software side, servers also need the following elements so that their
services can be available across the network:
Network drivers enable the server to communicate with its NIC. This software
lurks in the background and exists only to tie the computer to the NIC.
Protocol stacks send and receive messages across the network. This software
also lurks in the background and provides a common language shared with
clients used to ferry information across the network.
Service applications respond to requests for service and formulate replies
to those requests. This software runs in the foreground and does the useful
work. The service application includes the listener process, the temporary
execution threads, and some type of configuration or management console so
that it can be installed, configured, and altered as needed. Typical service
applications include directory services (Active Directory), database engines
(SQL Server or Oracle), and e-mail servers (Exchange).
Remember Most if not all, software that resides on a server, is network
aware because delivering information across a network is a server's primary
function.
The Session Layer manages the opening and closing of connections, and
assures the Layers above that each connection has its chance to send and
receive data. By opening multiple connection to several websites, atthe
same time you will be putting the Session Layer to use. Most of today's
computers are capable of multitasking and providing many sorts of services
over the Internet. They must call upon the Session Layer of the network in
order to serve their data to other machines in an efficient manner. Most
data transmitted over a network is not in the form of a sibgle packet.
Typically two or more nodes open connections between themselves and exchange
multiple packets. It is possible for multiple connections to be made to a
single machine. A Web page server would conform with this definition.
The Presentaion Layer provides a simple service to our Network Model. It
prepares data for the trip across the network and readies the data for use
within an end user application when the journey is done. Syntax for
communicating with a remote machine may be defined in the Presentation
Layer. As a translator for the data that the Application Layer wants to
send, it may be used to provide secure communications over a network
(encryption). Compression of data before sending it along through the
network, to the receiver node's Presentation Layer, can be useful.
It's up to the Presentation Layer to translate the URL into an appropriately
worded request that another machine will be able to recognize. the
Presentation Layer makes data presentable to the applications that use the
network; also presentable to the network itself. The URL will be translated
into a request that another machine will be able to recognize. Typing a URL
into an application i.e., Internet Explorer means nothing to the network.
The Application Layer is the last part of the OSI model to consider. The
Application Layer provides the final interface to the network that we, the
end users, use to access network services. You've interacted with the
Application Layer of the TCP/IP protocol if you've used a Web browser, a
mail reader, or anything else over the Internet. An application is called
by the name Application Layer. The Internet Explorer, Netscape Navigator,
Outlook, Eudora etc., are all examples of the Application Layer. Each of
the application programs mentioned is a layer of the model, and the final
product which we have been building up to. It is the resulting application
that hides all the inner workings of the network.
The sections above were taken from Using TCP/IP Special Edition by John Ray
publ. QUE 1999, chapter 1 Understanding Network Layers.
The Hardware/Physical Layer
The first layer, the hardware/physical layer provides the foundation that
the following layers wil build upon. Hardware refers to the computer,
network cable, satallite dishes, or any other physical devices you choose to
use when linking two or more computers. This concept includes the actual
physical wiring, and also the electrical signals that travel through the
wires.
Along with the inclusion of the elecrtrical signals that travel through the
wires, the hardware must also have the ability for determining when a signal
problem has occurred and for notifying upper levels (of the OSI model) of
the trouble.
This all happens at a level which we don't need to worry about. The
signaling properties are handled by the hardware that we have chosen to use,
to link the computers.
The Data Link Layer
The data link layer provides the bridge between hardware and software. It
must communicate physically with the physical/hardware layer, then prepare
data to be sent, and receive incoming data. Then it verifies the
correctness of the data (no collisions) before making it available to the
next layer. The data network is necessary for the data to flow Imagine a
unit of data, called a frame or packet, is to betransmitted over our physcal
layer. The data link layer must be capable of creating the packet holding
our information, identifying the destination of the remote machine or node
(that will receive the data), and providing low level error checking to
identify any problems. Define a node as any device that is connected to a
network. For our purposes, it usually refers to a computer. These notes
above are taken from Using TCP/IP publ. QUE 1999 pps. 9-11.
Data is transmitted across an ethernet network in the form of discrete
pieces of information. These pieces are known as packets or frames. A
frame has a structure that identifies where the packet is going, where it is
headed, the type of information contained in the frame, the data to be
transmitted, and Cyclic Redundancy Check (CRC) that hleps detect errors that
occur in transmission.
Typedef :
Destination 6 bytes
Source 6 bytes
Type 2 bytes
Data 46-1500 bytes
CRC 4 bytes
} Frame;
As you can see above, thae amount of data transmitted in each frame is
extremely small, a maximum of 1500 bytes. In my connections using Internet
I use the size of 576 bytes, which was advised by the site dslreports.com.
This is the maximum transmission unit (MaxMTU) size which is used by any
connection which uses the telephone lines. I would suppose that could be a
data segment of 558 bytes (576 -18 bytes).
Network Layer
The network layer is referred to a the IP module at times. The network
layer implements the "IP" in TCP/IP. The Internet Protocol allows packets
to be routed across different types of hardware and Data Link Layers. t
provides only an addressing scheme and a mechanism to fragment packets for
transmission across networks that allow very limited frame sizes.
The IP module takes data from the TCP module, applies the appropriate
addressing informaton to the data, and delivers it to the Data Link Layer.
The data will travel devices called Routers or Gateways which provide the
necessary links to the other networks.
The Session Layer
Normally, routers forward traffic based only on the final destination
address, but there are times when you want the router to make a forwarding
decision based on the source address, the type of traffic, or some other
criteria. These types of forwarding decisions, based on some criteria or
policy the system administrator has configured, are called policy-based
routing.
As the packets travel back and forthe between nodes, they carry both the
data that the end-user wanted to send and extra information that is used by
the protocol to help guarantee that the packets are delivered successfully.
A router can be configured to make a forwarding decision based on several
things,including:
Source address
Source/destination address pair
Destination address
IP packet type (TCP, UDP, ICMP, and so on)
Service type (Telnet, FTP, SMTP)
Precedence bits in the IP header
Typically, configuring policy-based routing consists of the following three
steps:
1. Build a filter to separate the traffic that needs a specific policy
applied from the normal traffic.
2. Build a policy.
3. Implement the policy.
On a Cisco router, a policy is built using route maps and is implemented
with interface commands. For example, in the network illustrated in Figure
1-3, the system administrator has decided it would be best to send Telnet
over the lower speed Frame Relay link and send the remaining traffic over
the satellite link.
IP addresses consist of four parts, each one representing eight binary
digits (bits), or an octet. Each octet can represent the numbers between 0
and 255, so there are 232, or 4,294,967,296 possible IP addresses.
To provide hierarchy, IP addresses are divided into two parts: the network
and the host. The network portion represents the network the host is
attached to; this
literally represents a wire or physical segment. The host portion uniquely
identifies each host on the network.
The IP address is divided into these two parts by the mask (or the subnet
mask). Each bit in the IP address, where the corresponding bit in the mask
is set to one, is part of the network address. Each bit in the IP address,
where the corresponding bit in the mask is set to zero, is part of the host
address.
Application Layer
Common services consist of anything a large number of users on the network
access on a regular basis, such as server farms, connections to external
routing domains (partners or the Internet, for example), and mainframes.
Where these services are connected depends on network topology issues (such
as addressing and redundancy, which will be covered in Chapters 2 through 4
in more detail), traffic flow, and architecture issues. In the case of
connections to external routing domains, it's almost always best to provide
a buffer zone between the external domain and the network core.
Other common services, such as mainframes and server farms, are often
connected more directly to the core. These could be the stovepipe
applications.
Figure 1-5 illustrates one possible set of connections to common services.
All external routing domains in this network are attached to a single DMZ,
and highspeed devices, which a large portion of the enterprise must access,
are placed on a common high-speed segment off the core.
The following are two typical methods of attaching these types of resources
to your network:
Attaching them directly to your network's core
Attaching them through a DeMilitarized Zone (DMZ)
Workstations/Clients, Desktop Machines
One of the key goals that drives networking is to interconnect all the
desktops in an organization, whether they run a DOS, Windows, UNIX, Linux,
or Macintosh operating system, so that they can communicate and share
resources.
Some of the resources shared by workstations include large disk arrays,
expensive color or laser printers, CD-ROM jukeboxes, and high-speed Internet
connections (all of which would be too expensive to connect to every desktop
machine.
Because workstations are where requests for services originate, such
machines are known as network clients, or more simply, as clients.
When you call such a machine a workstation, you emphasize its capability to
support an individual user more or less independently. When you call such a
machine a client, you focus on its connection to the network. It's a machine
that sits on your desk and is connected to a network.
Servers
Networking is about obtaining access to shared services. Because networks
are useless unless you can do something with them, access to services is
what networking is all about.
Computers that provide services to clients are generically called servers. A
server's job is to listen for requests from clients for whatever service or
services it offers, and to satisfy any valid requests for its services. In
fact, validating service requests is an important part of what servers do -
you wouldn't want just anyone to be able to print the salaries for everyone
in your company just because a user asks a print server to do so. You want
that server to verify that Bob is allowed to access that file before you let
him print it!
Throughout this book, you find out more about such validations and other key
aspects of what it takes for a server to provide services.
Network Drive
When you request a file from a network drive, a file server is probably
involved.
Network Directory
When you poke around in the network directory - you guessed it! - a
directory server is pulling the strings. For every service, some type of
server handles and responds to requests. Sometimes, a single server
provides many services; at other times, a server provides only a single
service.
Common Pathways - Networking
A common pathway must exist between any computer that requests services and
any computer whose job it is to satisfy such requests. Just as you need a
highway to drive from one city to another, you need a pathway over which
your computer can send and receive data. On a network, that's the job of the
media that tie all the various pieces together.
When you observe how all the pieces fit together - workstations, servers,
and media - you get a reasonably complete view of your network. Figure 1-1
depicts a simple network diagram that shows these purely physical elements
of a network. Notice that clients (desktop machines) outnumber servers, and
that media tie all the pieces together.
Networking follows the law of supply and demand, so the more clients you
have, the more (or bigger) servers you'll need. And the more work will get
accomplished.
What a Network is Doing
Figuring out whether a network is functioning is both easy and hard, and
most observers, including novices and experts alike, agree that telling when
a network's not working is easier than telling when it is!
A client must know how to ask for services from the network and must state
precisely what it's requesting.
Likewise, a server must know how to recognize and evaluate incoming requests
for its services and how to respond appropriately. Only then can a network
work correctly.
Understanding how this constant stream of requests and replies works means
looking a little deeper into how clients state their requests and how
servers satisfy them. In the following sections, we examine the mechanics of
this give-and-take.
Knowing how to ask is where the game begins
Knowing how to ask for network services requires some ability to distinguish
between what's available locally on a client machine and what's available
remotely from the network. Determining what's local and what's remote is the
key to handling network access correctly. This determination depends on
specialized software to handle the job in the background, so users don't
necessarily have to know the difference.
A computer's main control program is called its operating system (OS)
because it defines the software environment that lets a computer operate and
run the applications and system services that get things accomplished on a
machine. Most modern operating systems include built-in networking
capabilities to augment their control over local resources and devices.
Network Operating Systems
Certain modern operating systems can be called network operating systems
(NOSs) when they create network server environments. Their built-in
networking capabilities include a range of network services as part and
parcel of the underlying operating system. Windows Server 2003 certainly
fits this bill because it offers a broad range of powerful, flexible
networking capabilities.
Right out of the box, Windows Server 2003 understands the differences
between local and remote resources. The same is true for most modern desktop
operating systems, including Windows XP Professional, Windows 2000 Server
and Professional, Windows NT Server and Workstation, Windows 9x, the
Macintosh OS, as well as that old (but still modern) warhorse, UNIX.
KEY CONCEPT In Windows Server 2003, Windows XP Professional, Windows 2000,
Windows NT, Windows 9x, Macintosh, and UNIX operating systems, and through
add-ons to DOS and Windows 3. x, a special piece of software known as a
redirector keeps track of what's local and what's remote
when users or applications request resources. The redirector takes generic
requests for services and sends any that can't be satisfied locally to the
appropriate service provider elsewhere on the network (in other words, to
the appropriate server). Therefore, if you ask for a file that resides on a
server elsewhere on the network, the redirector hands your request off to
that machine and makes sure that the results of that request are delivered
properly.
For a computer to use network services, the computer must know how to ask
for them. That's what a requester does. But knowing what to ask for is as
important as knowing how to ask. In most cases, applications supply the
necessary information about network services that they want to access,
either through information supplied from a requester or through knowledge
built directly into an application itself.
E-mail clients and Web browsers represent good examples of applications with
sophisticated, built-in networking capabilities. On the other hand, file
system access tools, such as Windows Explorer, My Computer, and My
Documents, rely on the redirector to furnish them with views of (and access
to) shared files and printers elsewhere on the network.
Please note that applications with built-in networking knowledge offer
transparent access to network services because the applications know how to
ask for services and, often, what to ask for on the user's behalf.
Programmers design such computer applications to be transparent to keep the
applications out of sight and out of mind; therefore, the user remains
blissfully unaware of cumbersome networking details and trivia. File
managers, printer controls, and other tools
with access to both local and remote resources, however, require users to be
able to tell the difference between what's local and what's remote. In fact,
such tools usually force users to request access to remote resources
explicitly and directly.
Increasingly, finding out which services a network can provide is becoming
more and more implicit. This is why all editions of Windows Server 2003
support a set of directory services to catalog and describe the services
that the network can deliver to its users.
Likewise, Windows Server 2003 support the Distributed File System that
allows directories on multiple machines all around a network to appear as a
single network drive to users. Therefore, users don't have to know where
individual files or folders reside.
Such sophisticated mechanisms make it easier than ever before for users to
request and access resources implicitly without having to know how to
request those resources or having to determine exactly where they reside.
Nevertheless, some explicit knowledge about such things is necessary if you
want to make the most of Windows Server 2003's networking capabilities.
Other than the necessary listener processes and a set of service
applications that actually perform services, servers need the same hardware
components that clients do.
Servers need one or more NICs with a working connection to the network to
allow data to enter and leave the server.
Software is similar on the server side
On the software side, servers also need the following elements so that their
services can be available across the network:
Network drivers enable the server to communicate with its NIC. This software
lurks in the background and exists only to tie the computer to the NIC.
Protocol stacks send and receive messages across the network. This software
also lurks in the background and provides a common language shared with
clients used to ferry information across the network.
Service applications respond to requests for service and formulate replies
to those requests. This software runs in the foreground and does the useful
work. The service application includes the listener process, the temporary
execution threads, and some type of configuration or management console so
that it can be installed, configured, and altered as needed. Typical service
applications include directory services (Active Directory), database engines
(SQL Server or Oracle), and e-mail servers (Exchange).
Remember Most if not all, software that resides on a server, is network
aware because delivering information across a network is a server's primary
function.
Decodong a Client/Server Conversation
You may be wondering what the steps are in a conversation between a client
and server.
The following sequence presents a typical request to print a file on a
network printer (and, by necessity, through a print server) from a
spreadsheet program:
Assume that a network printer is set as the default printer for the
designated print job. A user requests print services in the spreadsheet
program by clicking the printer icon or by choosing File®Print.
1. The spreadsheet program formats the spreadsheet and then builds an
appropriate print file. A print file includes the text and graphics that
make up a file's content. It also includes instructions on how (bold,
italic, and so forth) and where (top, bottom, left, right) to place the
elements to be printed.
2. The spreadsheet program sends the print file to the printer.
3. The local networking software (assuming it's a Windows XP redirector)
recognizes that the printer is on the network and sends a print request to
print that file to the print server. The redirector accesses name and
network address information through a Windows networking service (called the
Browse Service, which talks to a browser server on the network) to figure
out where to send the print file.
4. On the server side, the listener process recognizes and checks out the
user's print request. We'll assume it's legal, so the listener process
creates a temporary execution thread to handle delivery of the incoming
print file packets from the client. This temporary thread tells the client
to start sending the print file.
5. Having now obtained permission to start shipping the file, the protocol
stack on the client chops the file up into small chunks (called packets)
that are delivered to the temporary thread on the server.
6. The temporary thread on the server oversees delivery of the file and
places it into a temporary holding area (called a spool file) where the
print server stores all pending print jobs. The print server places the job
in the print queue, which stores the print jobs in the order in which they
are received.
7. When the print job reaches the head of the queue, the server creates
another temporary thread to ship the job to the printer. In many cases, a
different protocol carries data from the server to the printer than the one
the client uses to ship data to the server in the first place.
8. In a final (and optional) step, the print server creates another
temporary thread to send a message to the client computer stating that the
print job is complete. Here, the same protocol used to transport the file
from the client to the server is often used to send this message back to the
client.
9. What's worth noting here is that a kind of conversation occurs between
client and server. The client initiates this conversation when it asks for
permission to print, and then it sends the print job to the print server.
The server takes over from there, storing the incoming print file in its
spool file, managing the queue, and then printing the file when its turn
comes. The conversation ends when the server sends notification of job
completion to the client. Requests for other services, such as access to a
database server, an e-mail server, or even a file server, are similar to the
previous interchange. In such cases, the conversation usually ends when the
server sends a data table, message, or file in reply to the client's
initiating requests. This request/reply sequence is really what makes modern
networks
work.
"Eli Gottlieb" <eligottlieb@xxxxxxxxx> wrote in message
news:46c3a06b$0$31912$4c368faf@xxxxxxxxxxxxxxxxx
Vzalamataz Portnoy wrote:across
Yesterday, i read about the issues involved with using time-stamping
physicalthe network which involves the protocol stack, and especially the
waslayer, and the networking signals. I was using it on a network, yet it
differentnot very well known to me. After research, i find out that there is a
collision avoidance built into the networking layer. Yet when two
usefulapplications are running, across the network the timestamping can be
aunder some conditions which involve the asynchronous (two-way) speed of
Atresponse to the time-stamping field in the packet, when it is active.
algorithmstimes the time-stamp packet will take up more cycles than processing the
data and sending the stream. And from what I know about parallel
in(beginner's books) this would apply to any microchip which is involved
ofparallel programs, since it is a centrol control which is at the heart
1/2multi-application systems. It might do you some good to target an
instruction at that part of your processor chip. You want to give it
advancethe period of a unit of time to advance (time period advance), else
it by your command (event list).Could you explain that in a way that saves me the time and money of a
The match search was about MAC and timestamp it came up with some decent
parallel network hits.
Think Ahead (call later)
networking course? I unfortunately cannot understand what you said or
how it applies to parallel languages.
--
Eli Z. Gottlieb
.
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