Web Development Glossary

Nov 19, 2006 by Charles Torvalds

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This glossary defines some of the common terminology related to Apache in particular, and web serving in general. More information on each concept is provided in the links.

Access Control: The restriction of access to network realms. In an Apache context usually the restriction of access to certain URLs.
See: Authentication, Authorization, and Access Control
Account: The term "account" is often used synonymously with username here at DynDNS. Both terms describe the name you use to log in to our system. An account is not the same as a hostname, which may be named differently.
age: The age of a response is the time since it was sent by, or successfully validated with, the origin server.
Alias: See cname.
Algorithm: An unambiguous formula or set of rules for solving a problem in a finite number of steps. Algorithms for encryption are usually called Ciphers.
APache eXtension Tool (apxs): A perl script that aids in compiling module sources into Dynamic Shared Objects ( dsos) and helps install them in the Apache Web server.
See: Manual Page: <a href="/aa/docs/2.0/programs/apxs.html">apxs</a>
A Record: An A Record, short for Address Record, allows a numeric ipaddress to map to a more human-readable domain. An A Record may also be referred to as a host or hostname.
Authoritative Nameserver: A nameserver which has been configured to provide answers for a specific domain, rather than simply getting and caching data about domains from other nameservers.
Authentication: The positive identification of a network entity such as a server, a client, or a user.
See: Authentication, Authorization, and Access Control
Advisory Committee: An Advisory Committee is a formal advisory body made up of representatives from the Internet community to advise ICANN on a particular issue or policy area. Several are mandated by the ICANN Bylaws and others may be created as needed. Advisory committees have no legal authority to act for ICANN, but report their findings and make recommendations to the ICANN Board.
AfriNIC - The Afican Network Information Center: AfriNIC is a Regional Internet Registry (RIR), and is a non-profit membership organization responsible for the administration and registration of Internet Protocol (IP) addresses in the Africa region.
ALAC - At-Large Advisory Committee: ICANN's At-Large Advisory Committee (ALAC) is responsible for considering and providing advice on the activities of the ICANN, as they relate to the interests of individual Internet users (the "At-Large" community). ICANN, as a private sector, non-profit corporation with technical management responsibilities for the Internet's domain name and address system, will rely on the ALAC and its supporting infrastructure to involve and represent in ICANN a broad set of individual user interests. On 31 October 2002, the ICANN Board adopted New Bylaws that establish the ALAC and authorize its supporting At-Large organizations. (Article XI, Section 2(4) of the New Bylaws.) The New Bylaws, which are the result of ICANN's 2002 reform process, went into effect on 15 December 2002. ALAC is to eventually consist of ten members selected by Regional At-Large Organizations, supplemented by five members selected by ICANN's Nominating Committee. To allow the ALAC to begin functioning immediately, the Transition Article of the Interim Bylaws provides for the Board to appoint ten members (two from each of ICANN's five regions) to an Interim ALAC. Underpinning the ALAC will be a network of self-organizing, self-supporting At-Large Structures throughout the world involving individual Internet users at the local or issue level. The At-Large Structures (either existing organizations or newly formed for this purpose) will self-organize into five Regional At-Large Organizations (one in each ICANN region - Africa, Asia-Pacific, Europe, Latin America/Caribbean, and North America). The Regional At-Large Organizations will manage outreach and public involvement and will be the main forum and coordination point in each region for public input to ICANN.
APNIC - The Asia Pacific Network Information Centre: APNIC is a Regional Internet Registry (RIR), and is a non-profit membership organization responsible for the administration and registration of Internet Protocol (IP) addresses in the Asia-Pacific region, including Japan, Korea, China, and Australia.
ARIN - American Registry for Internet Numbers: ARIN is a Regional Internet Registry (RIR), and is a non-profit membership organization established for the purpose of the administration and registration of Internet Protocol (IP) addresses in North America, parts of the Caribbean, and sub-Saharan Africa.
ASO - Address Supporting Organization: The ASO advises the ICANN Board of Directors on policy issues relating to the allocation and management of Internet Protocol (IP) addresses. The ASO selects two Directors for the ICANN Board.

BIND: BIND (Berkeley Internet Name Domain) is an implementation of the dns protocol. The BIND DNS server is used on the vast majority of Internet name servers, and is the reference implementation of the DNS specification.

content negotiation: The mechanism for selecting the appropriate representation when servicing a request, as described in section 12. The representation of entities in any response can be negotiated (including error responses).
CNAME: A CNAME, or Canonical Name, is an alias for a host record. When a name server looks up a name and finds a CNAME record, it instead looks up the canonical name. A typical CNAME might be used to redirect a subdomain (such as mail.website.com), to a mail host (webmail.yourisp.com).
cache: A program's local store of response messages and the subsystem that controls its message storage, retrieval, and deletion. A cache stores cacheable responses in order to reduce the response time and network bandwidth consumption on future, equivalent requests. Any client or server may include a cache, though a cache cannot be used by a server that is acting as a tunnel.
cacheable: A response is cacheable if a cache is allowed to store a copy of the response message for use in answering subsequent requests. The rules for determining the cacheability of HTTP responses are defined in section 13. Even if a resource is cacheable, there may be additional constraints on whether a cache can use the cached copy for a particular request.
Caching: Caching is a process where DNS servers store copies of information they receive from other DNS servers. This reduces the number of requests a DNS server needs to make. The amount of time that data is cached for is determined by its ttl.
Client: A client is any device or application that connects to a server.
Cloaking: Cloaking is a method of redirection which hides the actual URL of your site from the viewer's address bar via frames. Cloaking for non-credited users results in a popup ad being displayed the first time the page is accessed. Users who have purchased any of our services will automatically have the advertising popup removed.
Certificate: A data record used for authenticating network entities such as a server or a client. A certificate contains X.509 information pieces about its owner (called the subject) and the signing certificationauthority (called the issuer), plus the owner's publickey and the signature made by the CA. Network entities verify these signatures using CA certificates.
See: SSL/TLS Encryption
Certificate Signing Request (CSR): An unsigned certificate for submission to a certificationauthority, which signs it with the privatekey of their CA Certificate. Once the CSR is signed, it becomes a real certificate.
See: SSL/TLS Encryption
Certification Authority (CA): A trusted third party whose purpose is to sign certificates for network entities it has authenticated using secure means. Other network entities can check the signature to verify that a CA has authenticated the bearer of a certificate.
See: SSL/TLS Encryption
Cipher: An algorithm or system for data encryption. Examples are DES, IDEA, RC4, etc.
See: SSL/TLS Encryption
Ciphertext: The result after plaintext is passed through a cipher.
See: SSL/TLS Encryption
Common Gateway Interface (CGI): A standard definition for an interface between a web server and an external program that allows the external program to service requests. The interface was originally defined by NCSA but there is also an RFC project.
See: Dynamic Content with CGI
Configuration Directive: See: directive
Configuration File: A text file containing directive that control the configuration of Apache.
See: Configuration Files
CONNECT: An HTTP method for proxying raw data channels over HTTP. It can be used to encapsulate other protocols, such as the SSL protocol.
Context: An area in the configurationfile where certain types of directive are allowed.
See: Terms Used to Describe Apache Directives
ccNSO - The Country-Code Names Supporting Organization: The ccNSO is in the process of being established, with the ccNSO Assistance Group preparing the recommendations that are currently under discussion. Upon completion, the purpose of the ccNSO is to engage and provide leadership in activities relevant to country-code top-level domains (ccTLDs). This is achieved by 1) Developing policy recommendations to the ICANN Board, 2) Nurturing consensus across the ccNSO's community, including the name-related activities of ccTLDs; and 3) Coordinating with other ICANN SO's, Committees, or constituencies under ICANN. The ccNSO selects one person to serve on the board.
CCTLD - Country Code Top Level Domain: Two letter domains, such as .uk (United Kingdom), .de (Germany) and .jp (Japan) (for example), are called country code top level domains (ccTLDs) and correspond to a country, territory, or other geographic location. The rules and policies for registering domain names in the ccTLDs vary significantly and ccTLD registries limit use of the ccTLD to citizens of the corresponding country. Some ICANN-accredited registrars provide registration services in the ccTLDs in addition to registering names in .biz, .com, .info, .name, .net and .org, however, ICANN does not specifically accredit registrars to provide ccTLD registration services. For more information regarding registering names in ccTLDs, including a complete database of designated ccTLDs and managers, please refer to http://www.iana.org/cctld/cctld.htm.

Digital Signature: An encrypted text block that validates a certificate or other file. A certificationauthority creates a signature by generating a hash of the Public Key embedded in a Certificate, then encrypting the hash with its own Private Key. Only the CA's public key can decrypt the signature, verifying that the CA has authenticated the network entity that owns the Certificate.
See: SSL/TLS Encryption
Directive: A configuration command that controls one or more aspects of Apache's behavior. Directives are placed in the configurationfile
See: Directive Index
Dynamic Shared Object (DSO): module compiled separately from the Apache <a href="/aa/docs/2.0/programs/httpd.html">httpd</a> binary that can be loaded on-demand.
See: Dynamic Shared Object Support
DNS: DNS (the Domain Name System) provides mapping of hostname to ipaddress and back again.
DNSBL: A DNS-based Blackhole List, or DNSBL, is a record created by an Internet site contaning a list of IP addresses. A DNSBL may be queried by other devices or applications. The list is often (but not strictly) a collection of addresses which have been blocked due to abuse.
Delegate: To specify in DNS which nameserver handle a specific domain. See also delegation.
Delegation: Used to refer to the current set of nameservers to which a domain has been delegated. Before a nameserver is officially assigned to a domain, it must completely delegate.
Domain: A domain, or domain name, is what identifies a group of computers on the Internet. An example would be dyndns.com, which is the domain for many computers that use our service, where the name of a particular computer (in this case, the web server) would be www. In other words, the full name of the computer is www.dyndns.com. A domain name is fullyqualifieddomainname when it is a complete hostname, e.g. "example.homeip.net" instead of simply "example".
Dynamic: In the context of an ip, dynamic implies that it changes frequently. Often times, a person's IP address may change each ti me that his or her computer reconnects to the Internet, regardless of dial-up or broadband service. Dynamic DNS is a service for users with Dynamic IP Adresses. Similarly, a service is also offered to users with a static address.
Dynamic DNS: Dynamic DNS is a term used to describe services that alias a dynamic ip to a static hostname. This is the type of service we initially offered, and we plan to continue offering. Many ISPs charge, some up to $200/month, just for a static IP address. We emulate this ability for little or no charge.
Domain Name Resolvers: Scattered across the Internet are thousands of computers - called "Domain Name Resolvers" or just plain "resolvers" - that routinely cache the information they receive from queries to the root servers. These resolvers are located strategically with Internet Service Providers (ISPs) or institutional networks. They are used to respond to a user's request to resolve a domain name - that is, to find the corresponding IP address.
DNS - Domain Name System: The Domain Name System (DNS) helps users to find their way around the Internet. Every computer on the Internet has a unique address - just like a telephone number - which is a rather complicated string of numbers. It is called its "IP address" (IP stands for "Internet Protocol"). IP Addresses are hard to remember. The DNS makes using the Internet easier by allowing a familiar string of letters (the "domain name") to be used instead of the arcane IP address. So instead of typing 207.151.159.3, you can type www.internic.net. It is a "mnemonic" device that makes addresses easier to remember.

entity: The information transferred as the payload of a request or response. An entity consists of metainformation in the form of entity-header fields and content in the form of an entity-body, as described in section 7.
Environment Variable (env-variable): Named variables managed by the operating system shell and used to store information and communicate between programs. Apache also contains internal variables that are referred to as environment variables, but are stored in internal Apache structures, rather than in the shell environment.
See: Environment Variables in Apache
Export-Crippled: Diminished in cryptographic strength (and security) in order to comply with the United States' Export Administration Regulations (EAR). Export-crippled cryptographic software is limited to a small key size, resulting in Ciphertext which usually can be decrypted by brute force.
See: SSL/TLS Encryption
explicit expiration time: The time at which the origin server intends that an entity should no longer be returned by a cache without further validation.

first-hand: A response is first-hand if it comes directly and without unnecessary delay from the origin server, perhaps via one or more proxies. A response is also first-hand if its validity has just been checked directly with the origin server.
freshness lifetime: The length of time between the generation of a response and its expiration time.
fresh: A response is fresh if its age has not yet exceeded its freshness lifetime.
Filter: A process that is applied to data that is sent or received by the server. Input filters process data sent by the client to the server, while output filters process documents on the server before they are sent to the client. For example, the INCLUDES output filter processes documents for ssi.
See: Filters
Fully-Qualified Domain-Name (FQDN): The unique name of a network entity, consisting of a hostname and a domain name that can resolve to an IP address. For example, www is a hostname, example.com is a domain name, and www.example.com is a fully-qualified domain name.
FTP server: FTP stands for File Transfer Protocol. An FTP server is simply a file server, a simple way for people to access files on a particular computer from any other computer with Internet access. DynDNS does not provide FTP access as part of its service.
Fully Qualified Domain Name: A Fully Qualified domain is a complete hostname, like that which you would use when connecting to a server on the Internet. Fully qualified hostnames must be used when updating with a client, e.g., if your hostname is "myhost.dnsalias.net", you must provide that entire hostname to the client, not simply "myhost".

gateway: A server which acts as an intermediary for some other server. Unlike a proxy, a gateway receives requests as if it were the origin server for the requested resource; the requesting client may not be aware that it is communicating with a gateway.
gTLD Servers: The gTLD servers are a set of nameservers which contain information about all domains in the com, net, and org top-level domains.
GAC - Governmental Advisory Committee: The GAC is an advisory committee comprising appointed representatives of national governments, multi-national governmental organizations and treaty organizations, and distinct economies. Its function is to advise the ICANN Board on matters of concern to governments. The GAC will operate as a forum for the discussion of government interests and concerns, including consumer interests. As an advisory committee, the GAC has no legal authority to act for ICANN, but will report its findings and recommendations to the ICANN Board. The Chairman of the GAC is Sharil Tarmizi of Malaysia. The Secretariat of the GAC is based at the European Commission.
gTLD - Generic Top Level Domain: Most TLDs with three or more characters are referred to as "generic" TLDs, or "gTLDs". They can be subdivided into two types, "sponsored" TLDs (sTLDs) and "unsponsored TLDs (uTLDs), as described in more detail below. In the 1980s, seven gTLDs (.com, .edu, .gov, .int, .mil, .net, and .org) were created. Domain names may be registered in three of these (.com, .net, and .org) without restriction; the other four have limited purposes. Over the next twelve years, various discussions occurred concerning additional gTLDs, leading to the selection in November 2000 of seven new TLDs for introduction. These were introduced in 2001 and 2002. Four of the new TLDs (.biz, .info, .name, and .pro) are unsponsored. The other three new TLDs (.aero, .coop, and .museum) are sponsored. Generally speaking, an unsponsored TLD operates under policies established by the global Internet community directly through the ICANN process, while a sponsored TLD is a specialized TLD that has a sponsor representing the narrower community that is most affected by the TLD. The sponsor thus carries out delegated policy-formulation responsibilities over many matters concerning the TLD. A Sponsor is an organization to which is delegated some defined ongoing policy-formulation authority regarding the manner in which a particular sponsored TLD is operated. T he sponsored TLD has a Charter, which defines the purpose for which the sponsored TLD has been created and will be operated. The Sponsor is responsible for developing policies on the delegated topics so that the TLD is operated for the benefit of a defined group of stakeholders, known as the Sponsored TLD Community, that are most directly interested in the operation of the TLD. The Sponsor also is responsible for selecting the registry operator and to varying degrees for establishing the roles played by registrars and their relationship with the registry operator. The Sponsor must exercise its delegated authority according to fairness standards and in a manner that is representative of the Sponsored TLD Community.
GNSO - Generic Names Supporting Organization: The GNSO is the successor to the responsibilities of the Domain Name Supporting Organization (DNSO; see below) that relate to the generic top-level domains. The GNSO is the body of six constituencies, as follows: the Commercial and Business constituency, the gTLD Registry constituency, the ISP constituency, the non-commercial constituency, the registrar's constituency, and the IP constituency.

Handler: An internal Apache representation of the action to be performed when a file is called. Generally, files have implicit handlers, based on the file type. Normally, all files are simply served by the server, but certain file types are "handled" separately. For example, the cgi-script handler designates files to be processed as cgi.
See: Apache's Handler Use
Hash: A mathematical one-way, irreversable algorithm generating a string with fixed-length from another string of any length. Different input strings will usually produce different hashes (depending on the hash function).
Header: The part of the http request and response that is sent before the actual content, and that contains meta-information describing the content.
.htaccess: A configurationfile that is placed inside the web tree and applies configuration directive to the directory where it is placed and all sub-directories. Despite its name, this file can hold almost any type of directive, not just access-control directives.
See: Configuration Files
httpd.conf: The main Apache configurationfile. The default location is /usr/local/apache2/conf/httpd.conf, but it may be moved using run-time or compile-time configuration.
See: Configuration Files
HyperText Transfer Protocol (HTTP): The standard transmission protocol used on the World Wide Web. Apache implements version 1.1 of the protocol, referred to as HTTP/1.1 and defined by RFC 2616.
HTTPS: The HyperText Transfer Protocol (Secure), the standard encrypted communication mechanism on the World Wide Web. This is actually just HTTP over ssl.
See: SSL/TLS Encryption
Hostname: A hostname (also referred to as a "host"), is a computer's unique name on the Internet, which points to that computer's IP address.
heuristic expiration time: An expiration time assigned by a cache when no explicit expiration time is available.

IP Address: An IP address is a numeric representation of a computer's location on a network. It is similar to your street address, except it is for computers. IP addresses look something like 207.127.235.88. They are often hard to remember numbers, and they certainly don't tell you very much about a computer. That is why we provide aliasing services. IP addresses can be static or dynamic.
ISP: ISP stands for Internet Service Provider. Your ISP is the company that provides you with access to the Internet, and assigns you an IP address. Examples include AOL, UUNet, and MCI.
IANA - Internet Assigned Numbers Authority: The IANA is the authority originally responsible for the oversight of IP address allocation, the coordination of the assignment of protocol parameters provided for in Internet technical standards, and the management of the DNS, including the delegation of top-level domains and oversight of the root name server system. Under ICANN, the IANA continues to distribute addresses to the Regional Internet Registries, coordinate with the IETF and others to assign protocol parameters, and oversee the operation of the DNS.
ICANN: The Internet Corporation for Assigned Names and Numbers (ICANN) is an internationally organized, non-profit corporation that has responsibility for Internet Protocol (IP) address space allocation, protocol identifier assignment, generic (gTLD) and country code (ccTLD) Top-Level Domain name system management, and root server system management functions. Originally, the Internet Assigned Numbers Authority (IANA) and other entities performed these services under U.S. Government contract. ICANN now performs the IANA function. As a private-public partnership, ICANN is dedicated to preserving the operational stability of the Internet; to promoting competition; to achieving broad representation of global Internet communities; and to developing policy appropriate to its mission through bottom-up, consensus-based processes. The DNS translates the domain name you type into the corresponding IP address, and connects you to your desired website. The DNS also enables email to function properly, so the email you send will reach the intended recipient.
IDNs - Internationalized Domain Names: Internationalized Domain Names, or IDNs, are web addresses in your own language. Many efforts are underway in the Internet community to make domain names available in character sets other than ASCII. These "internationalized domain name" (IDN) efforts were the subject of a 25 September 2000 resolution by the ICANN Board of Directors, in which it recognized "that it is important that the Internet evolve to be more accessible to those who do not use the ASCII character set," but stressed that "the internationalization of the Internet's domain name system must be accomplished through standards that are open, non-proprietary, and fully compatible with the Internet's existing end-to-end model and that preserve globally unique naming in a universally resolvable public name space."
IETF - Internet Engineering Task Force: The IETF is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual.
IP - Internet Protocol: The communications protocol underlying the Internet, IP allows large, geographically diverse networks of computers to communicate with each other quickly and economically over a variety of physical links. An Internet Protocol Address is the numerical address by which a location in the Internet is identified. Computers on the Internet use IP addresses to route traffic and establish connections among themselves; people generally use the human-friendly names made possible by the Domain Name System.
ISOC - The Internet Society: The Int ernet Society is the international organization for global cooperation and coordination for the Internet and its internetworking technologies and applications. ISOC membership is open to any interested person.
ISP - Internet Service Provider: An ISP is a company, which provides access to the Internet to organizations and/or individuals. Access services provided by ISPs may include web hosting, email, VoIP (voice over IP), and support for many other applications.

LACNIC - Latin American and Caribbean Internet Addresses Registry: LACNIC is a Regional Internet Registry (RIR) for Latin America and the Caribbean.

Method: In the context of http, an action to perform on a resource, specified on the request line by the client. Some of the methods available in HTTP are GET, POST, and PUT.
Message Digest: A hash of a message, which can be used to verify that the contents of the message have not been altered in transit.
See: SSL/TLS Encryption
MIME-type: A way to describe the kind of document being transmitted. Its name comes from that fact that its format is borrowed from the Multipurpose Internet Mail Extensions. It consists of a major type and a minor type, separated by a slash. Some examples are text/html, image/gif, and application/octet-stream. In HTTP, the MIME-type is transmitted in the Content-Type header.
See: mod_mime
Module: An independent part of a program. Much of Apache's functionality is contained in modules that you can choose to include or exclude. Modules that are compiled into the Apache <a href="/aa/docs/2.0/programs/httpd.html">httpd</a> binary are called static modules, while modules that are stored separately and can be optionally loaded at run-time are called dynamic modules or dso. Modules that are included by default are called base modules. Many modules are available for Apache that are not distributed as part of the Apache HTTP Server tarball. These are referred to as third-party modules.
See: Module Index
Module Magic Number (MMN): Module Magic Number is a constant defined in the Apache source code that is associated with binary compatibility of modules. It is changed when internal Apache structures, function calls and other significant parts of API change in such a way that binary compatibility cannot be guaranteed any more. On MMN change, all third party modules have to be at least recompiled, sometimes even slightly changed in order to work with the new version of Apache.
Mail eXchanger (MX): A Mail eXchanger is a type of DNS record that allows you to control the delivery of mail for a given domain or subdomain. Multiple MX records may be present, in case the primary exchanger fails.

Nameserver: A nameserver is a server which has been set up to answer DNS queries, and provide information about a certain set of domain.

origin server: The server on which a given resource resides or is to be created.
OpenSSL: The Open Source toolkit for SSL/TLS
See http://www.openssl.org/#

proxy: An intermediary program which acts as both a server and a client for the purpose of making requests on behalf of other clients. Requests are serviced internally or by passing them on, with possible translation, to other servers. A proxy MUST implement both the client and server requirements of this specification. A "transparent proxy" is a proxy that does not modify the request or response beyond what is required for proxy authentication and identification. A "non-transparent proxy" is a proxy that modifies the request or response in order to provide some added service to the user agent, such as group annotation services, media type transformation, protocol reduction, or anonymity filtering. Except where either transparent or non-transparent behavior is explicitly stated, the HTTP proxy requirements apply to both types of proxies.
Pass Phrase: The word or phrase that protects private key files. It prevents unauthorized users from encrypting them. Usually it's just the secret encryption/decryption key used for cipher.
See: SSL/TLS Encryption
Plaintext: The unencrypted text.
Private Key: The secret key in a publickeycryptography system, used to decrypt incoming messages and sign outgoing ones.
See: SSL/TLS Encryption
Proxy: An intermediate server that sits between the client and the origin server. It accepts requests from clients, transmits those requests on to the origin server, and then returns the response from the origin server to the client. If several clients request the same content, the proxy can deliver that content from its cache, rather than requesting it from the origin server each time, thereby reducing response time.
See: mod_proxy
Public Key: The publicly available key in a publickeycryptography system, used to encrypt messages bound for its owner and to decrypt signatures made by its owner.
See: SSL/TLS Encryption
Public Key Cryptography: The study and application of asymmetric encryption systems, which use one key for encryption and another for decryption. A corresponding pair of such keys constitutes a key pair. Also called Asymmetric Cryptography.
See: SSL/TLS Encryption
PTR Records: PTR records are a reverse lookup for an A record. Due to the nature of DNS and the way reverse lookups work, PTR records can only be controlled by your ISP.
Phishing: Phishing refers to an attempt to fraudulently acquire sensitive information, such as passwords and credit card details, by posing as a trustworthy person or business in an apparently official electronic communication, such as an email, instant message, or website.
Pseudo-Static: The term pseudo-static, which is used in the Custom DNS service, has to do with how long other DNS servers will cache a particular host's IP. It is a compromise between the dynamic and the static settings. It is most appropriate for those people who have an IP address that is mostly static, but occasionally changes.

resource: A network data object or service that can be identified by a URI, as defined in section 3.2. Resources may be available in multiple representations (e.g. multiple languages, data formats, size, and resolutions) or vary in other ways.
Regular Expression (Regex): A way of describing a pattern in text - for example, "all the words that begin with the letter A" or "every 10-digit phone number" or even "Every sentence with two commas in it, and no capital letter Q". Regular expressions are useful in Apache because they let you apply certain attributes against collections of files or resources in very flexible ways - for example, all .gif and .jpg files under any "images" directory could be written as "/images/.*(jpg|gif)$". Apache uses Perl Compatible Regular Expressions provided by the PCRE library.
Reverse Proxy: A proxy server that appears to the client as if it is an origin server. This is useful to hide the real origin server from the client for security reasons, or to load balance.
Registrar: Your registrar is the organization through whom you've registered your domain. DynDNS, for example, is a registrar for com/net/org domains (and some others).
Root Servers: The root servers are nameservers that all other nameservers on the Internet know about, and contain very basic information about the DNS system, which will lead other servers along the path to finding out specific information about a host.
representation: An entity included with a response that is subject to content negotiation, as described in section 12. There may exist multiple representations associated with a particular response status.
RGP - Redemption Grace Period: Problems and complaints relating to deletion of domain-name registrations are very common. Businesses and consumers are losing the rights to their domain names through registration deletions caused by mistake, inadvertence, or fraud. Current procedures for correcting these mistakes have proven inadequate. To move toward a solution to these problems ICANN developed the RGP. How it works: Now, the "delete" of a domain name (whether inside or outside of any applicable grace period) will result in a 30-day Deleted Name Redemption Grace Period. This grace period will allow the domain name registrant, registrar, and/or registry time to detect and correct any mistaken deletions. During this 30-day period, the deleted name will be placed on REGISTRY-HOLD, which will cause the name to be removed from the zone. (The domain name will not function/resolve.) This feature will help ensure notice to the registrant that the name is subject to deletion at the end of the RGP, even if the contact data the registrar has for the registrant is no longer accurate. During the Redemption Grace Period, registrants can redeem their registrations through registrars. Registrars would redeem the name in the registry for the original registrant by paying renewal fees, plus a service charge, to the registry operator. Any party requesting redemption would be required to prove its identity as the original registrant of the name. After the 30-day period when the domain name can be redeemed, there is a 5-day period when the domain essentially is pending deletion. This timeframe is implemented to facilitate notice to all registrars before a domain is finally deleted.
Registrar: Domain names ending with .aero, .biz, .com, .coop, .info, .museum, .name, .net, .org, and .pro can be registered through many different companies (known as "registrars") that compete with one another. The registrar you choose will ask you to provide various contact and technical information that makes up the registration. The registrar will then keep records of the contact information and submit the technical information to a central directory known as the "registry." This registry provides other computers on the Internet the information necessary to send you e-mail or to find your web site. You will also be required to enter a registration contract with the registrar, which sets forth the terms under which your registration is accepted and will be maintained.
Registry: The "Registry" is the authoritative, master database of all domain names registered in each Top Level Domain. The registry operator keeps the master database and also generates the "zone file" which allows computers to route Internet traffic to and from top-level domains anywhere in the world. Internet users don't interact directly with the registry operator; users can register names in TLDs including .biz, .com, .info, .net, .name, .org by using an ICANN-Accredited Registrar.
RIR - Regional Internet Registry: There are currently five RIRs: AfriNIC, APNIC, ARIN, LACNIC and RIPE NCC. These non-profit organizations are responsible for distributing IP addresses on a regional level to Internet service providers and local registries.
RIPE and RIPE NCC - RÃƒÂ©seaux IP EuropÃƒÂ©ens: RIPE is an open and voluntary organization, which consists of European Internet service providers. The RIPE NCC acts as the Regional Internet Registry (RIR) for Europe and surrounding areas, performs coordination activities for the organizations participating in RIPE, and allocates blocks of IP address space to its Local Internet Registries (LIRs), which then assign the addresses to end-users.
Root Servers: The root servers contain the IP addresses of all the TLD registries - both the global registries such as .com, .org, etc. and the 244 country-specific registries such as .fr (France), .cn (China), etc. This is critical information. If the information is not 100% correct or if it is ambiguous, it might not be possible to locate a key registry on the Internet. In DNS parlance, the information must be unique and authentic.

stale: A response is stale if its age has passed its freshness lifetime.
semantically transparent: A cache behaves in a "semantically transparent" manner, with respect to a particular response, when its use affects neither the requesting client nor the origin server, except to improve performance. When a cache is semantically transparent, the client receives exactly the same response (except for hop-by-hop headers) that it would have received had its request been handled directly by the origin server.
server: An application program that accepts connections in order to service requests by sending back responses. Any given program may be capable of being both a client and a server; our use of these terms refers only to the role being performed by the program for a particular connection, rather than to the program's capabilities in general. Likewise, any server may act as an origin server, proxy, gateway, or tunnel, switching behavior based on the nature of each request.
Secure Sockets Layer (SSL): A protocol created by Netscape Communications Corporation for general communication authentication and encryption over TCP/IP networks. The most popular usage is HTTPS, i.e. the HyperText Transfer Protocol (HTTP) over SSL.
See: SSL/TLS Encryption
Server Side Includes (SSI): A technique for embedding processing directives inside HTML files.
See: Introduction to Server Side Includes
Session: The context information of a communication in general.
SSLeay: The original SSL/TLS implementation library developed by Eric A. Young
Symmetric Cryptography: The stu dy and application of Ciphers that use a single secret key for both encryption and decryption operations.
See: SSL/TLS Encryption
Secondary DNS: Secondary DNS is one of our paid service offerings. It provides backup DNS servers that download information from your primary DNS server and share its load.
Spam: Spam is defined as unsolicited commercial or bulk e-mail (UCE or UBE). A close synonym would be "junk mail".
Static: Static means unchanging, not moving. In the context of an ip, it means that the address stays the same each time that you logon or connect to the Internet. Most static IP addresses are on permanent connections, that stay on the Internet all the time, but some are on home dialup connections. Connections that are not static are called dynamic.
Subdomain: A subdomain is somewhere in-between a domain name and a hostname (see above). A subdomain adds another level to a domain; an example would be is.mine.nu, a subdomain of mine.nu. Users who have purchased upgrade credit(s) can delegate a static host that they own to their own DNS server(s), or to the Custom DNS service.
SESAC - Security and Stability Advisory Committee: The President's standing committee on the security and stability of the Internet's naming and address allocation systems. Their charter includes a focus on risk analysis and auditing. SESAC consists of approximately 20 technical experts from industry and academia as well as operators of Internet root servers, registrars, and TLD registries.
SO - Supporting Organizations: The SOs are the three specialized advisory bodies that will advise the ICANN Board of Directors on issues relating to domain names (GNSO and CCNSO) and, IP addresses (ASO).

tunnel: An intermediary program which is acting as a blind relay between two connections. Once active, a tunnel is not considered a party to the HTTP communication, though the tunnel may have been initiated by an HTTP request. The tunnel ceases to exist when both ends of the relayed connections are closed.
Tarball: A package of files gathered together using the tar utility. Apache distributions are stored in compressed tar archives or using pkzip.
Transport Layer Security (TLS): The successor protocol to SSL, created by the Internet Engineering Task Force (IETF) for general communication authentication and encryption over TCP/IP networks. TLS version 1 and is nearly identical with SSL version 3.
See: SSL/TLS Encryption
TTL: TTL stands for "Time To Live" and is the amount of time in seconds that a DNS record will be cached by an outside DNS server.
Tarpitting: Tarpitting refers to the practice of attempting to starve the resources of a spammer or hacker by holding open a connection until it times out. This tactic is, in general, not particularly effective, and, when used in combination with any of our MailHop services, can cause serious problems, and should not be used.
TLD - Top-level Domain: TLDs are the names at the top of the DNS naming hierarchy. They appear in domain names as the string of letters following the last (rightmost) ".", such as "net" in "www.example.net". The administrator for a TLD controls what second-level names are recognized in that TLD. The administrators of the "root domain" or "root zone" control what TLDs are recognized by the DNS. Commonly used TLDs include .com, .net, .edu, .jp, .de, etc.

user agent: The client which initiates a request. These are often browsers, editors, spiders (web-traversing robots), or other end user tools.
upstream/downstream: Upstream and downstream describe the flow of a message: all messages flow from upstream to downstream. inbound/outbound Inbound and outbound refer to the request and response paths for messages: "inbound" means "traveling toward the origin server", and "outbound" means "traveling toward the user agent"
Uniform Resource Locator (URL): The name/address of a resource on the Internet. This is the common informal term for what is formally called a uniformresourceidentifier. URLs are usually made up of a scheme, like http or https, a hostname, and a path. A URL for this page is /aa/docs/2.0/glossary.html.
Uniform Resource Identifier (URI): A compact string of characters for identifying an abstract or physical resource. It is formally defined by RFC 2396. URIs used on the world-wide web are commonly referred to as url.
URL: A Uniform Resource Locator, or URL, is used as a standard way of specifying the location of a web page or other object on the Internet. URLs often appear on web pages as links to other sites.
Update: Updating is simply the process of changing the information associated with a host in our system. This is usually performed by a client when the user's dynamic ip changes.
Upload: To upload means to copy a file from the local system you are working on to a (usually larger) "host" or "server". DynDNS does not allow uploading to its servers; any web page you want to host using our service, you must store and host on your own machine connected to the Internet.
UDRP - Uniform Dispute Resolution Policy: All ICANN-accredited registrars follow a uniform dispute resolution policy. Under that policy, disputes over entitlement to a domain-name registration are ordinarily resolved by court litigation between the parties claiming rights to the registration. Once the courts rule who is entitled to the registration, the registrar will implement that ruling. In disputes arising from registrations allegedly made abusively (such as "cybersquatting" and cyberpiracy"), the uniform policy provides an expedited administrative procedure to allow the dispute to be resolved without the cost and delays often encountered in court litigation.

validator: A protocol element (e.g., an entity tag or a Last-Modified time) that is used to find out whether a cache entry is an equivalent copy of an entity.
variant: A resource may have one, or more than one, representation(s) associated with it at any given instant. Each of these representations is termed a `varriant'. Use of the term `variant' does not necessarily imply that the resource is subject to content negotiation.
Virtual Hosting: Serving multiple websites using a single instance of Apache. IP virtual hosting differentiates between websites based on their IP address, while name-based virtual hosting uses only the name of the host and can therefore host many sites on the same IP address.
See: Apache Virtual Host documentation

Web Redirection: Web Redirection (otherwise known as HTTP redirection) allows a short hostname to be substituted in the place of a longer, ugly, hard-to-remember (or otherwise unwanted) URL.
Wildcard: Wildcards add an alias to *.yourhost.ourdomain.ext pointing to the same IP address as entered for yourhost.ourdomain.ext.
W3C - World Wide Web Consortium: The W3C is an international industry consortium founded in October 1994 to develop common protocols that promote the evolution of the World Wide Web and ensure its interoperability. Services provided by the Consortium include: a repository of information about the World Wide Web for developers and users; reference code implementations to embody and promote standards; and various prototype and sample applications to demonstrate use of new technology.
WIPO - World Intellectual Property Organization: WIPO is an intergovernmental organization based in Geneva, Switzerland responsible for the promotion of the protection of intellectual rights throughout the world. It is one of the 16 specialized agencies of the United Nations system of organizations.
WHOIS: Information about who is responsible for domain names is publicly available to allow rapid resolution of technical problems and to permit enforcement of consumer protection, trademark, and other laws. The registrar will make this information available to the public on a "Whois" site. It is however possible to register a domain in the name of a third party, as long as they agree to accept responsibility -- ask your registrar for further details.

X.509: An authentication certificate scheme recommended by the International Telecommunication Union (ITU-T) which is used for SSL/TLS authentication.
See: SSL/TLS Encryption

Webmaster Glossary Links

W3C Architecture Domain - Terms
Hypertext Terms
Weaving the Web - Berners-Lee
Web Accessibility glossary
Quality Assurance glossary
WebmasterWorld
Google Glossary
Dublin Core
Glossary of Ask.com Search Results Terminology
Yahoo! Web Hosting Glossary

Web Development Glossary

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