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At least three sources of content quickly emerge on enterprise Intranets: formal,project/group, and informal.

The is the officially sanctioned and commissioned information ofthe enterprise. It usually has been reviewed for accuracy, currency, confidentiality,liability and commitment. This is the information with which the formalmanagement infrastructure is most concerned.

is intended for use within a specific group. It may be usedto communicate and share ideas, coordinate activities or manage the developmentand approval of content that eventually will become formal. Project/Groupinformation generally is not listed in the enterprise-wide directories and may beprotected by passwords or other restrictions if general access might create problems.

begins to appear on the Intranet when authors and usersdiscover how easy it is to publish within the existing infrastructure. Informalinformation is not necessarily the same thing as personal home pages. A personalfolder or directory on an Intranet server can serve as a repository for white papers,notes and concepts that may be shared with others in the enterprise to furthercommon interests, for the solicitation of comments or for some other reason. Insteadof making copies, the URL can be given to the interested parties, and the latestversion can be read and tracked as it changes. This type of informal information canbecome a powerful stimulus for the collaborative development of new concepts andideas.

There are two basic types of pages: content pages and broker pages. Content pages containthe information of value required by a user. Broker pages help users find the content pages

appropriate for their current requirements.

can take many forms. They may be static pages, like the ones you arereading here, or they may be active pages where the page content is generated "onthe fly" from a database or other repository of information. Content pages generallyare owned by an individual. Over time expect the "form and sense" of content pagesto change as more experience is gained in the areas of non-linear documents (hyper-linking), multimedia, modular content and integration of content and logic usingapplets.

also come in more than one form, but all have the same function, tohelp users find relevant information. Good broker pages serve an explicitly defined

audience or function. Many of the pages with which we already are familiar arebroker pages. A hyperlink broker page contains links to other pages, in context. Italso may have a short description of the content to which it is pointing to help theuser evaluate the possibilities. On the other hand, a search oriented broker page isnot restricted to the author's scope, but it also does not provide the same level ofcontext to help the user formulate the appropriate question.

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The Intranet Infrastructure relies on four distinct roles for managing the formal content:the Web Administrator, publishers, editors and authors.

The is responsible for facilitating cooperative opportunitiesamong the various organizations in the enterprise and administering the enterprisecontent management infrastructure. By contrast, the is responsible forthe technical infrastructure. The same person may serve in both roles, but to do sorequires that she have both of the distinctly different skill sets and enough time tocarry out both sets of responsibilities. The Web Administrator chairs the EnterpriseWeb Council.

determine what kinds of formal information will be created andmaintained by their organization. They represent their organization on theEnterprise Web Council and may create and chair an Editorial Board within theirown organization. The publishers own the processes and policies that both theenterprise and their organization require officially sanctioned information to follow.In larger organizations, they may delegate the monitoring and implementation toeditors, but the responsibility remains with the publisher.

are found in organizations that have multiple product lines or service areas.For example, Human Resources might have editors for Benefits, Compensation,Equal Opportunity and Staffing. In a line of business, the editor often is the primarymarketing person for each product line. The editor determines what officialinformation will be created for specific activities and manages the informationcreation and update process, including the formal review cycles.

create the content.

A firewall is a secure and trusted machine that sits between a private network and apublic network. The firewall machine is configured with a set of rules that determinewhich network traffic will be allowed to pass and which will be blocked or refused.

A proxy server, also known as a "proxy" or "application level gateway", is a computer thatacts as a gateway between a local network (e.g., all the computers at one company or in onebuilding) and a larger-scale network such as the Internet. Proxy servers provide increasedperformance and security. In some cases, they monitor employees' use of outside resources.

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In computer networks, a is a server (a computer system or an applicationprogram) that services the requests of itsclientsby forwarding requests to other servers. Aclient connects to the proxy server, requesting some service, such as a file, connection, webpage, or other resource, available from a different server. The proxy server provides theresource by connecting to the specified server and requesting the service on behalf of theclient. A proxy server may optionally alter the client's request or the server's response, andsometimes it may serve the request without contacting the specified server. In this case, itwould 'cache' the first request to the remote server, so it could save the information forlater, and make everything as fast as possible.

A server accelerates service requests by retrieving content saved from aprevious request made by the same client or even other clients. Caching proxies keep localcopies of frequently requested resources, allowing large organizations to significantlyreduce their upstream bandwidth usage and cost, while significantly increasingperformance. Most ISPs and large businesses have a caching proxy.

A proxy that focuses on WWW traffic is called a "web proxy". The most common use of aweb proxy is to serve as aweb cache. Most proxy programs (e.g.Squid) provide a means todeny access to certain URLs in ablacklist, thus providing content filtering. This is usuallyused in a corporate environment, though with the increasing use of Linux in smallbusinesses and homes, this function is no longer confined to large corporations. Some webproxies reformat web pages for a specific purpose or audience (e.g., cell phones and PDAs).

An anonymous proxy server (sometimes called a web proxy) generally attempts to

anonymize web surfing. These can easily be overridden by site administrators, and thusrendered useless in some cases. There are different varieties of anonymizers. One of themore common variations is the open proxy. Because they are typically difficult to track,open proxies are especially useful to those seeking online anonymity, from politicaldissidents to computer criminals.

: Some proxy servers implement a logon requirement. In large organizations,authorized users must log on to gain access to theweb. The organization can thereby trackusage to individuals.

Proxies can also be installed in order to eavesdrop upon the dataflow between clientmachines and the web. All accessed pages, as well as all forms submitted, can be capturedand analyzed by the proxy operator. For this reason, passwords to online services (such aswebmail and banking) should always be exchanged over a cryptographically securedconnection, such as SSL.

http://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Server_%28computing%29http://en.wikipedia.org/wiki/Server_%28computing%29http://en.wikipedia.org/wiki/Client_%28computing%29http://en.wikipedia.org/wiki/Client_%28computing%29http://en.wikipedia.org/wiki/Client_%28computing%29http://en.wikipedia.org/wiki/Web_cachehttp://en.wikipedia.org/wiki/Web_cachehttp://en.wikipedia.org/wiki/Web_cachehttp://en.wikipedia.org/wiki/Squid_%28software%29http://en.wikipedia.org/wiki/Squid_%28software%29http://en.wikipedia.org/wiki/Squid_%28software%29http://en.wikipedia.org/wiki/Blacklist_%28computing%29http://en.wikipedia.org/wiki/Blacklist_%28computing%29http://en.wikipedia.org/wiki/Blacklist_%28computing%29http://en.wikipedia.org/wiki/Anonymizerhttp://en.wikipedia.org/wiki/Anonymizerhttp://en.wikipedia.org/wiki/Open_proxieshttp://en.wikipedia.org/wiki/Open_proxieshttp://en.wikipedia.org/wiki/World_Wide_Webhttp://en.wikipedia.org/wiki/World_Wide_Webhttp://en.wikipedia.org/wiki/World_Wide_Webhttp://en.wikipedia.org/wiki/Eavesdrophttp://en.wikipedia.org/wiki/Eavesdrophttp://en.wikipedia.org/wiki/Eavesdrophttp://en.wikipedia.org/wiki/World_Wide_Webhttp://en.wikipedia.org/wiki/Open_proxieshttp://en.wikipedia.org/wiki/Anonymizerhttp://en.wikipedia.org/wiki/Blacklist_%28computing%29http://en.wikipedia.org/wiki/Squid_%28software%29http://en.wikipedia.org/wiki/Web_cachehttp://en.wikipedia.org/wiki/Client_%28computing%29http://en.wikipedia.org/wiki/Server_%28computing%29http://en.wikipedia.org/wiki/Computer_network

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An (also known as a "transparent proxy") combines a proxy server with agateway. Connections made by client browsers through the gateway are redirected throughthe proxy without client-side configuration (or often knowledge).

The term "forced proxy" is ambiguous. It means both "intercepting proxy" (because it filtersall traffic on the only available gateway to the Internet) and its exact opposite, "non-intercepting proxy" (because the user is forced to configure a proxy in order to access theInternet).

Main article:Open proxyBecause proxies might be used to abuse, system administrators have developed anumber of ways to refuse service to open proxies. ManyIRCnetworks automaticallytest client systems for known types of open proxy. Likewise, anemail servermay beconfigured to automatically teste-mailsenders for open proxies.

A is a proxy server that is installed in the neighborhood of one or more webservers. All traffic coming from the Internet and with a destination of one of the webservers goes through the proxy server.

Most modern firewalls distinguish between and . Afirewall proxy server is an application that acts as an intermediary between two end

systems.

Firewalls fall into four broad categories:

oooo .

firewalls work at the network level of the OSI model, or the IP layer ofTCP/IP. They are usually part of a router. A router is a device that receives packets fromone network and forwards them to another network. In a packet filtering firewall eachpacket is compared to a set of criteria before it is forwarded.

work at the session layer of the OSI model, or the TCP layer ofTCP/IP. They monitor TCP handshaking between packets to determine whether arequested session is legitimate. Information passed to remote computer through a circuitlevel gateway appears to have originated from the gateway.

http://en.wikipedia.org/wiki/Gateway_%28computer_networking%29http://en.wikipedia.org/wiki/Gateway_%28computer_networking%29http://en.wikipedia.org/wiki/Open_proxyhttp://en.wikipedia.org/wiki/Open_proxyhttp://en.wikipedia.org/wiki/Open_proxyhttp://en.wikipedia.org/wiki/IRChttp://en.wikipedia.org/wiki/IRChttp://en.wikipedia.org/wiki/IRChttp://en.wikipedia.org/wiki/Mail_transport_agenthttp://en.wikipedia.org/wiki/Mail_transport_agenthttp://en.wikipedia.org/wiki/Mail_transport_agenthttp://en.wikipedia.org/wiki/Electronic_mailhttp://en.wikipedia.org/wiki/Electronic_mailhttp://en.wikipedia.org/wiki/Electronic_mailhttp://en.wikipedia.org/wiki/Electronic_mailhttp://en.wikipedia.org/wiki/Mail_transport_agenthttp://en.wikipedia.org/wiki/IRChttp://en.wikipedia.org/wiki/Open_proxyhttp://en.wikipedia.org/wiki/Gateway_%28computer_networking%29

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, also called proxies, are similar to circuit-level gateways exceptthat they are application specific. They can filter packets at the application layer of the OSImodel. Incoming or outgoing packets cannot access services for which there is no proxy.

combine the aspects of the other three types offirewalls. They filter packets at the network layer, determine whether session packets arelegitimate and evaluate contents of packets at the application layer. They allow directconnection between client and host, alleviating the problem caused by the lack oftransparency of application level gateways.