In standard DNS, an authoritative DNS nameserver is one that has knowledge of the DNS domain to which the origin server belongs.
In GRM deployments, GRM DNS servers interact with authoritative DNS nameservers to resolve DNS queries for unrecognized domains and to perform other functions, such as zone transfers.
In the context of GRM, the GRM DNS server can appear to be the authoritative DNS server for a content provider, if a GRM DNS server takes over DNS for the existing CDN namespace. In this case, the GRM DNS server assumes the identity of the authoritative DNS nameserver (also referred to as the back-end DNS nameserver), and subsequently resolves all DNS queries for domains associated with the CDN namespace. DNS queries for non-CDN domains and other DNS operations are proxied through the GRM DNS server to the back-end DNS nameserver.
The authoritative DNS nameserver for the CDN. The GRM DNS server must use the back-end DNS nameserver to resolve DNS queries for non-CDN domains and to perform other DNS operations. These operations are proxied through the GRM DNS server to the back-end DNS nameserver.
The location in which objects are stored until they expire or are replaced by an updated version.
The process by which a NetCache appliance receives a request for an object and can resolve the request from its cache rather than having to fetch the object from the origin server.
The process by which a NetCache appliance receives a request for an object but that object is not in the cache. The NetCache appliance then attempts to fetch the object from the origin server.
Network appliances on which the GRM agent software is enabled that have been identified in the GRM server configuration as a center cache. Edge caches are located in edge groups, such as POPs, that are remote from the data center. Edge caches in a particular edge group serve only the clients associated with that edge group.
See Classless Inter-Domain Routing.
A type of network routing that uses the network mask instead of the address class to determine the destination network.
Two or more NetCache appliances or firewalls over which the NetCache appliance distributes requests for the purposes of load balancing and failover.
A network service provider that distributes content and services to optimize content delivery and charges a fee to do so.
Any company in the business of aggregating or producing content for delivery via the Internet.
Information sent by a Web server to a client about a particular Web page. This information is generally used to maintain user-specific information and to adjust the appearance of a particular page accordingly, allowing for more personalized content. However, a Web page with a cookie attached to it requires special attention and might be uncacheable.
Domain Name Service (DNS) is the standard mechanism on the Internet for advertising and accessing a variety of information about computer hosts. DNS handles mapping between host names, which humans find convenient, and Internet addresses, which computers require. DNS makes host information available throughout the Internet, distributed among many sites and organizations, not just in a single central site.
One of two types of software on a NetCache appliance that restricts access to Web sites. It identifies the sites that contain content in various categories, maintains lists of those sites in control files, and restricts access accordingly.
Network appliances on which the GRM agent software is enabled that have been identified in the GRM server configuration as an edge cache. Edge caches are located in edge groups, such as POPs, in a location remote from the data center. Edge caches in a particular edge group serve only the clients associated with that edge group.
A group remote from the data center in which edge caches are located, such as a POP, are referred to as edge groups. Edge groups are identified in the GRM server configuration.
Edge caches in a particular edge group serve only the clients associated with that edge group.
The process by which an alternate system takes over and emulates the primary system if the primary system becomes unusable. See also takeover.
The component of a news server that accepts news feeds from other news servers. The Feeder server might be on the same computer as other news server software components or it might be on a different computer.
A server or device deployed between a LAN and the external WAN to control all inbound and outbound traffic, thus the enhancing security of the network behind the firewall.
See network flap.
From the client's perspective, a forward proxy operates on behalf of a client Web browser or media player. A forward proxy can handle requests for a virtually unlimited number of servers. Forward proxy servers are located close to the client. NetCache appliances operating as Web caches, news caches, and streaming media caches are forward proxies.
File Transfer Protocol.
The complete name of a specific computer on the Internet, consisting of the computer's host name and its domain name. A host's FQDN consists of its host name and its domain name, separated by a period. For example, the host euler, located in the domain netapp.com, has an FQDN of euler.netapp.com.
A predecessor of the HTTP protocol, and is seldom used today.
A generic term to refer to NetCache appliances on which the GRM agent software is enabled. In the GRM server configuration, a cache on which the GRM agent software is installed can be identified as a center cache or an edge cache.
A NetCache appliance that is typically located in a CDN data center and is configured as a GRM server. A NetCache appliance can be configured as a GRM DNS server, if DNS-based redirection is desired, or as a GRM L7 server, if application-layer (L7) based redirection is desired.
A repeating signal transmitted from one appliance to another that indicates that the appliance is in operation. Heartbeat information is also stored on disk.
Hypertext Transport Protocol Secure. A variant of HTTP used for accessing secure Web servers. See also Secure Sockets Layer (SSL).
Internet Content Adaptation Protocol. A high-level protocol that provides a common format for requesting services from a server.
Internet Cache Protocol. The method by which a hierarchy of NetCache appliances can communicate with each other. A derivative of UDP, ICP enables NetCache to query other caches for individual Web pages.
The unique numerical address of a computer that is attached to a TCP/IP network, for example, 198.95.226.66.
You can use the NetCache appliance IP spoofing feature to configure NetCache to use the client IP address as the source address when communicating with servers. Requests originating from a client retain the client's source address even if requests are passed through a chain of proxy-cache servers. The requests, therefore, appear to originate from the client rather than from the NetCache appliance.
Switches typically include multiple methods for handling traffic. When this guide refers to L4 or L7 switches, it refers to a feature on a switch that can support transparent proxying; that is, a feature that operates on the L4 or L7 layer of the OSI model. Switch names vary by vendor.
Lightweight Directory Access Protocol server. LDAP is a client-server protocol for accessing a directory service. NetCache can be configured to point to an LDAP server for authentication of user requests.
A live media stream occurs in real time, like the news program on a television set. Some organizations record a live media stream and then broadcast the media stream to their employees or customers at a specified time. All users who have requested the media stream see the same media stream at the same time. Users are not able to rewind or fast-forward a live media stream.
See also stream, on-demand media stream, and streaming media.
See Server Load Balancer.
1,048,576 bytes, or 1,024 KB. Unit of measure for computer storage.
The streaming media control protocol used in Windows Media 3 & 4 streams.
See Microsoft Media Streaming.
Process by which NetCache receives a live stream through the multicast transport protocol from a streaming server that is configured to support multicast streaming. If set for multicast input for streaming media, NetCache always attempts to receive data from the upstream streaming server through multicast.
Process by which NetCache sends the live stream to clients through the multicast transport protocol regardless of how the stream is received from the streaming server. If set for multicast output for streaming media, when a client requests a multicast stream, NetCache always sends the received data to the client through multicast, regardless of how the stream was received.
Process by which NetCache delivers live content to a large number of clients. In the multicast streaming model, NetCache receives one copy of the requested stream through an IP multicast channel from the streaming server. A network of routers then splits the stream to all clients on the local network that are listening for a multicast broadcast at the group address. See also unicast streaming.
The Internet encompasses more than 95,000 networks worldwide. The networks in the Internet are linked together in the United States at several major intersection points. One type of intersection point is a Network Access Point. There are three NAPs. These NAPs ensure the continued broad-based access to the Internet.
A Route Arbiter server is located at each NAP. The server provides access to the Routing Arbiter Database. ISPs can query Route Arbiter servers to validate the reachability information advertised by an autonomous system. (An autonomous system is a collection of networks and gateways with its own internal mechanism for collecting routing information and passing it to other independent systems.)
Network routes that change rapidly over a short period of time. Flapping routes strain routers and can lead to broken connections if clients' packets switch between paths with different characteristics; for example, paths that include transparent redirection to a NetCache appliance and paths that do not implement transparency.
A NetCache appliance that is configured to accept news requests from clients and to fetch NNTP objects from a news server or another NetCache appliance that connects to a news server.
Network News Transfer Protocol. A news transmission protocol for the Internet that can be used to transport news from one host to another. Also, newsreader software can use NNTP to access the news database on a server host. One great advantage that NNTP has over UCP, which preceded NNTP for news transport, is that an NNTP host receiving multiple news feeds generally receives only one copy of each article.
A type of firewall NetCache must be aware of in order to forward requests through it to the Internet. That is, NetCache must be configured to send requests directly to the correct firewall IP address and port.
NT LAN Manager. A Windows NT authentication protocol; supported by NetCache.
A previously recorded media stream that users can request at a time most convenient to them. Users can rewind and fast-forward on-demand media streams. Also known as video-on-demand or VOD.
See also stream, live media stream, and streaming media.
Open Systems Interconnection (OSI) Reference architectural model. The OSI model contains seven layers that define the functions of communications protocols.
A remote location that provides network connectivity back to the core of the network for users within its service area. Service providers deploy POPs to give customers an entry point to their networks from their local loops.
See point of presence.
See routing policies.
See streaming media presentation.
Remote Authentication Dial-in User Service. RADIUS is a client-server protocol for accessing a directory service. A NetCache appliance can be configured to point to a RADIUS server for authentication of user requests.
The component of a news server that obtains the data that the news cache requests from a news storage device, such as a Network Appliance filer. When the news cache does not have requested news in its cache, it connects to the Reader server component of the news server, through NNTP. The Reader server might be on the same computer as other news server software components or it might be on a different computer.
An open standard for delivery of real-time media over the Internet. See also streaming media.
A feedback protocol that provides quality of service information to the streaming server. The RTCP feedback mechanism periodically describes the state of the network so that the streaming server and the client can negotiate the optimum bit rate for current network conditions. By default, RTCP uses UDP for transport.
A reverse proxy server (also referred to as an accelerator) handles requests on behalf of the origin server, acting as an extension of the origin server. A reverse proxy, unlike a forward proxy, services one or a few origin servers. Random servers cannot be accessed through a reverse proxy server. Clients use the reverse proxy to access all origin servers that the reverse proxy is servicing.
A reverse proxy server is usually operated by the same organization that operates the origin servers it services and it is located close to the origin server.
Rules that control what routes are accepted and what routes are advertised.
See Real-Time Transport Control Protocol.
See Real Time Streaming Protocol.
A protocol that is a standard method for secure, encrypted communication over the Internet. See also HTTPS.
A security product that enables you to administer a NetApp appliance in a nontrusted environment by creating a secure exchange between a client and the NetApp appliance using SSH and SSL protocols. Developed by Network Appliance.
A device that can balance requests over servers and hosts, such as NetCache appliances. SLBs are likely to provide strict load-balancing algorithms (such as least connections, weighted percentage, fastest connections, and round-robin) rather than to distribute requests based on IP address.
This device might also be referred to as a load-balancing router.
See WCCP service group.
One of two types of software on a NetCache appliance that restricts access to Web sites. It identifies the sites that contain content in various categories, maintains lists of those sites in control files, and restricts access accordingly.
The process of delivering a unique stream to multiple clients simultaneously. Splitting reduces the number of requests sent across the network to the streaming server. See also stream and streaming media.
A streaming media file being transmitted over a network. Streams are of two types, live media streams and on-demand media streams. See also live media stream, on-demand media stream, streaming media, and unique stream.
A NetCache appliance that caches content from one or more streaming servers that you identify. A streaming accelerator provides that content to clients that request it. To the outside world, the streaming accelerator is the streaming server. In contrast, when NetCache runs as a streaming media cache, it acts as an agent for the media player.
A term used to describe media files that begin playing while they are being transmitted over the network to the media player on the client computer. In contrast, conventional Web files must be downloaded entirely before the user can view them. Commonly requested types of streaming media are video and audio. Streaming media also includes interactive media, cartoon-like animations, panoramic data, and more.
A streaming media cache is a specially configured NetCache appliance that intercepts client requests for streaming media (RTSP, MMS, or both). When a streaming media cache is deployed between clients and a streaming media server, streaming requests that would otherwise have been sent directly to the streaming server are sent to the cache. For live streaming media presentations, bandwidth savings are realized when multiple clients request the same unique stream. NetCache caches on-demand media streams. See also splitting, streaming media, stream, and on-demand media stream.
Streaming media presentation is a general term used to describe the delivery of live or on-demand streaming media. Multiple unique streams can make up a streaming media presentation. See also stream, unique stream.
The configuration of one specific NetCache appliance to take over NetCache servicing functions of one other NetCache appliance in the event of failure.
In streaming media, the streaming server's process of dropping a consistent number of video or audio frames to try to make the data being delivered to the client more efficiently during playback.
See also streaming media.
The time limit on how long a copy of an object remains in the cache before NetCache verifies the object with the originating Web server.
In this model, the proxy-cache server cache is populated as a result of user requests. If the content a user requests is not in the proxy-cache server, the proxy-cache server obtains the requested content from the origin server and delivers it to the requesting users, and at the same time saves a copy of the object in its cache (if the content is cacheable). The content is then available for the next client that requests it. The cache, therefore, is populated only as a result of user request. This method can be thought of as the pull concept of content delivery.
Contrast this model with prefilling the cache, that is, pushing content to a NetCache appliance.
A firewall that NetCache can connect through without having to know the IP address of the firewall.
A method for providing access to NetCache appliances in which users do not have to manually configure Web browsers or media players for requests to be sent to the NetCache appliances. Transparent proxying is typically deployed with an L4 switch, and L7 switch, or a WCCP router. Less commonly, it is deployed with a policy-based router.
See Time To Live.
User Datagram Protocol. A connectionless network protocol that provides simple but unreliable transmission. An alternative to TCP that does not contain error checking.
One-to-one transmission in which each client opens a connection to a NetCache appliance to retrieve streaming content. In unicast streaming, NetCache receives a copy of the requested stream from a streaming server and sends a separate copy to each requesting client. See also multicast streaming.
A stream whose connection speed, media type, or thinning parameters are different from another stream that is part of the same streaming media presentation. See also stream and streaming media.
Uniform Resource Locator. To find a Web resource, you enter a name called a URL in the Location field of your Web browser, for example, http://www.netapp.com/.
A previously recorded media stream that users can request at a time most convenient to them. Users can rewind and fast-forward on-demand media streams. Also known as an on-demand stream. See also stream, live media stream, and streaming media.
A single virtual interface that is created from multiple physical interfaces by using the EtherChannel technology.
An architecture designed to allow bulk data transfer directly to or from application buffers. VI also allows applications to access VI-capable hardware directly without operating system intervention. See also VIF.
See video on-demand
A Cisco router running WCCP 2.0 software.
In WCCP, traffic redirection and distribution is based on logical WCCP service groups. A service group is a group of one or more routers and one or more proxy-cache servers that can work together in traffic redirection and distribution because they have been defined, through a service group definition, with the same settings.
A NetCache appliance that caches content from one or more Web servers that you identify. A Web accelerator provides that content to clients that request it. To the outside world, the Web accelerator is the Web server. In contrast, when NetCache runs as a Web cache, it acts as an agent for the browser.
A NetCache appliance configured as an intermediary server that accepts requests from clients and forwards them to a Web server or, if appropriate, services the requests from its own cache. A Web cache acts as an agent for the client browser. A NetCache appliance configured as a Web cache handles any or all of HTTP, FTP, Gopher, and Tunnel (for example, HTTPS and SSL) requests.
See DynaBLocator
A collective term for Microsoft's streaming audio and video technologies.
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Part No. 210-00372
File: glossary.htm
Last updated: 11/13/02 18:12:27