Saturday, August 21, 2010

LDAP

The Lightweight Directory Access Protocol (LDAP) is an application protocol for querying and modifying data of directory services implemented in Internet Protocol (IP) networks.

A directory is a set of objects with attributes organized logically in a hierarchical manner. A simple example is the telephone directory, which consists of a list of names (of either persons or organizations) organized alphabetically, with each name having an address and phone number associated with it.

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A directory information tree often reflects various political, geographic, and/or organizational boundaries, depending on the model chosen. LDAP deployments today tend to use Domain Name System (DNS) names for structuring the topmost levels of the hierarchy. Deeper inside the directory might appear entries representing people, organizational units, printers, documents, groups of people or anything else that represents a given tree entry (or multiple entries).

The latest version of LDAP is Version 3, which is specified in a series of Internet Engineering Task Force (IETF) Standard Track Requests for comments (RFCs) as detailed in RFC 4510

Protocol overview

A client starts an LDAP session by connecting to an LDAP server, called a Directory System Agent (DSA), by default onTCP port 389. The client then sends an operation request to the server, and the server sends responses in return. With some exceptions, the client does not need to wait for a response before sending the next request, and the server may send the responses in any order.

The client may request the following operations:

§ Start TLS — use the LDAPv3 Transport Layer Security (TLS) extension for a secure connection

§ Bind — authenticate and specify LDAP protocol version

§ Search — search for and/or retrieve directory entries

§ Compare — test if a named entry contains a given attribute value

§ Add a new entry

§ Delete an entry

§ Modify an entry

§ Modify Distinguished Name (DN) — move or rename an entry

§ Abandon — abort a previous request

§ Extended Operation — generic operation used to define other operations

§ Unbind — close the connection (not the inverse of Bind)

In addition the server may send "Unsolicited Notifications" that are not responses to any request, e.g. before it times out a connection.

A common alternate method of securing LDAP communication is using an SSL tunnel. This is denoted in LDAP URLs by using the URL scheme "ldaps". The default port for LDAP over SSL is 636. The use of LDAP over SSL was common in LDAP Version 2 (LDAPv2) but it was never standardized in any formal specification. This usage has been deprecated along with LDAPv2, which was officially retired in 2003.

LDAP is defined in terms of ASN.1, and protocol messages are encoded in the binary format BER. It uses textual representations for a number of ASN.1 fields/types, however.

Directory structure

dn: cn=John Doe,dc=example,dc=com

cn: John Doe

givenName: John

sn: Doe

telephoneNumber: +1 888 555 6789

telephoneNumber: +1 888 555 1232

mail: john@example.com

manager: cn=Barbara Doe,dc=example,dc=com

objectClass: inetOrgPerson

objectClass: organizationalPerson

objectClass: person

objectClass: top

Saturday, August 14, 2010

IP Addressing A Simplified Tutorial

Classless Inter-Domain Routing (CIDR) is a methodology of allocating IP addresses and routing Internet Protocol packets. It was introduced in 1993 to replace the prior addressing architecture of classful network design in the Internet with the goal to slow the growth of routing tables on routers across the Internet, and to help slow the rapid exhaustion of IPv4 addresses.

IP addresses are described as consisting of two groups of bits in the address: the most significant part is the network address which identifies a whole network or subnet and the least significant portion is the host identifier, which specifies a particular host interface on that network. This division is used as the basis of traffic routing between IP networks and for address allocation policies. Classful network design for IPv4 sized the network address as one or more 8-bit groups, resulting in the blocks of Class A, B, or C addresses. Classless Inter-Domain Routing allocates address space to Internet service providers and end users on any address bit boundary, instead of on 8-bit segments. In IPv6, however, the host identifier has a fixed size of 64 bits by convention, and smaller subnets are never allocated to end users.

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Wednesday, April 28, 2010

Introducing Microsoft SQL Server 2008 R2


SQL Server 2008 R2 was announced at TechEd 2009, and was released to manufacturing on April 21, 2010 . SQL Server 2008 R2 adds certain features to SQL Server 2008 including master data management system branded asMaster Data Services, a centralized console to manage multiple SQL Server instances, and support for more than 64 logical processors.

PART I Database Administration

CHAPTER 1 SQL Server 2008 R2 Editions and Enhancements
CHAPTER 2 Multi-Server Administration
CHAPTER 3 Data-Tier Applications
CHAPTER 4 High Availability and Virtualization Enhancements
CHAPTER 5 Consolidation and Monitoring

PART II Business Intelligence Development

CHAPTER 6 Scalable Data Warehousing
CHAPTER 7 Master Data Services
CHAPTER 8 Complex Event Processing with StreamInsight
CHAPTER 9 Reporting Services Enhancements
CHAPTER 10 Self-Service Analysis with PowerPivot

Wednesday, April 14, 2010

Proxy Server ?

Proxy Server ?


A proxy server is a computer that sits between a client and a server to intercept requests. There are several uses of a proxy server, but the most common is to speed network traffic by caching pages or files that are requested often. By doing so, the proxy server can deliver the request quickly, only polling the server when required. In this way, a proxy server not only speeds up network traffic, but also relieves server load. Major Internet hubs and Internet Service Providers (ISPs) employ dozens of proxy servers.

Filtering or censorship is another use for a proxy server. A company that provides Internet connectivity to its employees might configure a proxy server to block requests for certain websites. It can also filter content based on configurable criteria to help enforce acceptable use policies.

If a proxy server does not require a Web browser to be configured to use the proxy, it’s called a transparent proxy server. Otherwise, the Web browser must point to the proxy in order to use it. Companies favor the former, as employees cannot bypass it by reconfiguring their Web browsers. A proxy server is also commonly used as a firewall. It can scan for malware, viruses, and other threats, safeguarding the main server and network.

Secure Sockets Layer (SSL) servers used to create Virtual Private Networks (VPNs) sometimes use https proxies. These proxies speed traffic over secure channels and check for viruses in tunneled communications. The https proxy server can encrypt, decrypt, and cache encrypted data. Regular proxy servers cannot cache encrypted data for security reasons, and therefore serve no purpose in a VPN. There are differences of opinion as to whether https proxy servers create potential security risks.

Yet another use for a proxy server is to provide anonymous Web surfing. Many services provide proxies for the public to use to protect their online anonymity. The customer’s requests go to the website’s proxy server, which strips the customer’s Internet protocol (IP) address and sends them on their way. The information gets routed back to the proxy, which then forwards the pages to the customer’s browser. As far as the Internet is concerned, the only IP address on the remote server(s) is the proxy’s IP address. Only the proxy server knows the customer’s IP address. Companies that run anonymous proxy servers generally claim to wipe proxy server logs often to protect customer privacy.

Another model includes a network of volunteer proxy servers. This model uses encryption to obfuscate the original IP address and ultimate route a request takes. As the request makes its way through the Internet from one proxy server to the next, each server in the middle can only read the adjacent steps in the chain. Contents, origin, and ultimate destination are all unavailable.

The final proxy server decrypts the contents and delivers the request to the server without a plain text record of where the request originated. The page or file then returns the same way, through a series of encrypted steps. This system thwarts traffic analysis and protects privacy while protecting the proxy servers themselves.

Friday, February 19, 2010

PHP

PHP: Hypertext Preprocessor


PHP: Hypertext Preprocessor (the name being a recursive acronym) is a widely used, general-purpose scripting language that was originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document. As a general-purpose programming language, PHP code is processed by an interpreter application in command-line mode performing desired operating system operations and producing program output on its standard output channel. It may also function as a graphical application. PHP is available as a processor for most modern web servers and as standalone interpreter on most operating systems and computing platforms.

PHP was originally created by Rasmus Lerdorf in 1995[1] and has been in continuous development ever since. The main implementation of PHP is now produced by The PHP Group and serves as the de facto standard for PHP as there is no formal specification. PHP is free software released under the PHP License, which is incompatible with the GNU General Public License (GPL) because restrictions exist regarding the use of the term PHP.
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