Glossary

alternates: Different versions of the same web object. Some origin servers answer requests to the same URL with a variety of objects. The content of these objects can vary widely, depending on whether a server delivers content for different languages, targets different browsers with different presentation styles, or delivers variable content at different times of the day.
cache: Stores copies of frequently-accessed objects close to users and serves them to users when requested. Also see: object store.
cache hierarchy: Cache levels that communicate with each other. All cache hierarchies recognize the concepts of parent cache and child cache.
cache hit: An object in the cache that can be served directly to the client.
cache miss: An object that is not in the cache or that is in the cache but no longer valid. In both cases, Traffic Server must retrieve the object from the origin server.
caching web proxy server: A web proxy server with local cache storage that allows the proxy to fulfill client requests locally, using a cached copy of the origin server’s previous response.
CGI: Common Gateway Interface. A set of rules that describe how an origin server and another piece of software (a CGI program) located on the same machine communicate.
cgi-bin: The most common directory name on an origin server in which CGI programs are stored.
child cache: A cache lower in a cache hierarchy for which Traffic Server is a parent; child and parent communicate directly. See also: parent cache.
cluster: A group of Traffic Server nodes that share configuration information and can act as a single large virtual cache.
cookie: A piece of information sent by an origin server to a web browser. The browser software saves the information and sends it back to the server whenever the browser makes additional requests from the server. Cookies enable origin servers to keep track of users.
DNS: Domain Name Service. Traffic Server includes a fast, asynchronous DNS resolver to streamline conversion of hostnames to IP addresses.
explicit proxy caching: A Traffic Server configuration option, in which client software (typically a browser) must be specifically configured to send web requests to the Traffic Server proxy.
forward proxy caching: Proxy caching of content requested by web clients. Can be transparent or explicit.
full clustering: A Traffic Server cluster that distributes its cache across its nodes into a single, virtual object store, rather than replicating the cache node-by-node. See also: management-only clustering.
hierarchical live splitting: When a hierarchical deployment for streaming media performs live splitting. See also: hierarchy and live splitting.
hierarchy: Two or more Traffic Server hosts between the client and the content. One host between the client and the content is a single-level hierarchy.
HTTP: Hypertext Transfer Protocol. The client/server protocol upon which the World Wide Web is based.
ICP: Internet Cache Protocol. A protocol for proxy caches to exchange information about their content.
IP: Internet Protocol. The lowest-layer protocol under TCP/IP, responsible for end-to-end forwarding and long packet fragmentation control.
ISP: Internet Service Provider. An organization that provides access to the Internet.
JavaScript: A scripting language commonly used to create web pages. JavaScript is used to make web pages more interactive (such as to display forms and buttons). JavaScript can be used with Java, but Java is not required for JavaScript to work correctly.
L4 switch: An Ethernet switch that controls network traffic flow using Level 4 rules. The switch can intercept desired client protocol packets and direct them to a proxy for transparent operation.
live passthrough mode: The phrase used to describe when Traffic Server passes live streams from the origin server to the client.
live splitting: Occurs when Traffic Server splits one live stream from the origin server into several streams to different clients.
management-only clustering: A Traffic Server option wherein all nodes in a cluster automatically share configuration information. See also: full clustering.
Netscape log format: A standard access log format. Using the Netscape log format, you can analyze Traffic Server access log files with off-the-shelf log analysis scripts. See also: Squid log format.
news server: A server that controls access to a news group. To read and post messages to a news group, a user must connect to a news server.
NNTP: Network News Transfer Protocol. A protocol used to distribute, inquire, retrieve, and post news articles.
object store: A custom high-speed database on which Traffic Server stores all cached objects.
origin server: The web server that contains the original copy of the requested information.
PAC file: Proxy Auto-Configuration file. A specialized JavaScript function definition that a browser calls to determine how requests are handled.
parent cache: A cache higher up in a cache hierarchy to which Traffic Server can send requests.
plugin: An add-on feature that provides additional functionality to Traffic Server, such as origin server blacklisting, web content filtering, authentication, and data transformation.
proxy server: See web proxy server.
pull splitting: Occurs when a host contacts the upstream host to send payload data.
push splitting: Occurs when an upstream host sends data to the downstream host with no request from the downstream host.
reverse proxy: A option that enables Traffic Server to be configured as an origin server for convenient geographical distribution of server content. Reverse proxy also offloads static content service from servers that build dynamic content and provides a peak load buffer (or surge protector) for origin servers. Sometimes referred to as server acceleration.
router: A device that handles the connection between two or more networks. Routers look at the destination addresses of the packets passing through them and decide which route to send them on.
server acceleration: See reverse proxy.
SOCKS: A circuit-level proxy protocol that provides a tunneling mechanism for protocols that cannot be proxied conveniently.
Squid log format: A standard access log format. With the Squid log format, you can analyze Traffic Server event log files with off-the-shelf log analysis scripts. See also: Netscape log format.
SSL: Secure Sockets Layer. A protocol that enables encrypted, authenticated communications across the Internet. SSL is used mostly in communications between origin servers and web browsers.
syslog: The UNIX system logging facility.
TCP: Transmission Control Protocol. An Internet Standard transport layer protocol that provides reliable end-to-end communication by using sequenced data sent by IP.
traffic_cop: A Traffic Server process that periodically monitors the health of the traffic_server and traffic_manager processes by issuing heartbeat requests to fetch synthetic web pages.
Traffic Line: A Traffic Server command-line utility that enables you to monitor performance and change configuration settings.
traffic_manager: The Traffic Server process responsible for launching, monitoring, and reconfiguring the traffic_server process. It is also responsible for the proxy autoconfiguration port, cluster administration, and virtual IP failover.
traffic_server: A Traffic Server process that is the cache processing engine of the Traffic Server product. traffic_server is responsible for accepting connections, processing requests, and serving documents from the cache or origin server.
Traffic Shell: A Traffic Server command-line tool that enables you to monitor performance and change configuration settings.
UDP: User Datagram Protocol. The underlying transport protocol used by the data transfer protocols.
Underlying transport protocol: A protocol that transports bits. See also: Control Protocol and Data Transfer Protocol.
URL: Uniform Resource Locator. The address that defines the route to a file on the web or other Internet facility.
virtual IP failover: An option available to clustered Traffic Servers, in which Traffic Server maintains a pool of virtual IP addresses that it assigns to the nodes of a cluster. If a node fails, then the remaining nodes mask the fault and take over the failed node’s virtual interface.
web proxy server: A web server that forwards client requests to origin servers. The proxy server can deny requests according to filter rules or security limitations.
web server: A computer that provides World Wide Web services on the Internet. See also: origin server.
WPAD: Web Proxy Auto-Discovery. A protocol that allows clients to automatically locate a web proxy, providing the benefits of a proxy without the need for explicit client configuration.