ContentKeeper Knowledge Base

Word	Description
BOOTP	An acronym for Bootstrap Protocol. BOOTP uses IP or UDP Protocols. It allows a client machine to discover its own IP address, the address of a server host, and the name of a file to be loaded into memory and executed. The bootstrap operation can be thought of as consisting of two phases. The first phase, which could be labelled 'address determination and boot file selection'. After this address and filename information is obtained, control passes to the second phase of the bootstrap where a file transfer occurs. The file transfer will typically use the TFTP protocol, since it is intended that both phases reside in ROM on the client. However BOOTP could also work with other protocols such as SFTP or FTP.
Bridge	An adaptive Ethernet bridge is a device that passes data packets between multiple network segments that use the same communication protocols. An adaptive bridge passes one signal at a time. If a packet is destined for a computer within the senders own network segment, the adaptive bridge retains the packet within that segment. If a packet is destined for a segment different from the one where it originated then the bridge will forward the packet.
Buffer	A region of RAM reserved for use with data that is temporarily held while waiting to be transferred between two locations, such as between an application’s data area and an input / output device.
Caching Proxy Server	A server that sits between a client application, such as a Web browser, and an actual server. When a caching proxy server receives a request for a URL, it looks for the URL in its local cache. If found, it returns the document immediately, otherwise it retrieves it from the remote server, saves a copy in the cache and returns it to the requester. The cache will usually have an expiry algorithm, which flushes documents according to their age, size, and access history.
Control List	A list containing categorised URLs. In the content filtering process any URL that is browsed to is compared to this list and, if there is a match then the URL is processed in a predefined way. If there is not a match then the URL is not processed.
Control List Blocking	This refers to the process of blocking URLs based on entries in the local Control List.
DMZ	A De-Militarised Zone, or Secure Server Network (SSN). A DMZ is used by an organisation that wants to host Internet services without allowing unauthorized access to its private network. The DMZ sits between the Internet and an internal network's line of defence, usually a firewall. Typically, the DMZ contains devices accessible to Internet traffic, such as Web (HTTP) servers, FTP servers, SMTP (e-mail) servers and DNS servers.
Ethernet	Ethernet is a popular LAN technology that uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) between clients over a variety of cable types. Ethernet is passive which means that it requires no power source of it’s own, and thus does not fail unless the cable is physically cut or improperly terminated. Ethernet uses multiple communication protocols and can connect mixed computing environments, including NetWare, UNIX, Windows and Macintosh.
Firewall	A dedicated gateway server configured with special security criteria. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All traffic entering or leaving the intranet passes through the firewall, which examines each packet and blocks those that do not meet the specified security criteria.
Globally Reclassified URLs	URLs that have been reclassified and uploaded into the ContentKeeper Technologies Data Centre Database and subsequently made available to all ContentKeeper Clients worldwide.
GRE	Web Cache Co-ordination Protocol (WCCP) facilitates the link between Cisco IOS-enabled routers and cache engines. Through WCCP, cache engines can be clustered to provide scalability and resiliency. The protocol allows one or more proxies to register with a single router to receive (WCCP-GRE encapsulated) redirected traffic. It also allows one of the proxies, the designated proxy, to dictate to the router how redirected traffic is distributed across the array.
H.A.M	An electro-mechanical device that monitors the ContentKeeper Appliance to ensure Ethernet connectivity. The H.A.M. is configured to watch for a polling signal from the ContentKeeper Appliance at a predefined interval. Should this signal fail to be transmitted (an indication that the ContentKeeper Appliance has stopped), mechanical relays inside the H.A.M. will close and short circuit the ContentKeeper Adaptive Ethernet Bridge, effectively cutting the ContentKeeper Appliance out of the Ethernet circuit and allowing continued (unfiltered) Internet access.
High Availability Module	An electro-mechanical device that monitors the ContentKeeper Appliance to ensure Ethernet connectivity. The H.A.M. is configured to watch for a polling signal from the ContentKeeper Appliance at a predefined interval. Should this signal fail to be transmitted (an indication that the ContentKeeper Appliance has stopped), mechanical relays inside the H.A.M. will close and short circuit the ContentKeeper Adaptive Ethernet Bridge, effectively cutting the ContentKeeper Appliance out of the Ethernet circuit and allowing continued (unfiltered) Internet access.
Host	An addressable device attached to a computer network, also called a "node". A host can be a computer or some other device, such as a printer. Every host has a unique network address, sometimes called a Data Link Control (DLC) address or Media Access Control (MAC) address.
Hub	Hubs are connectivity devices that connect computers in a star topology. Hubs contain multiple ports for connecting to network components. If you use a hub, a break in the network does not affect the entire network; only the segment and the computer attached to that segment fail. A single data packet sent through a hub is transmitted to all ports on the hub.
ICAP	Internet Content Adaptation Protocol (ICAP) is a lightweight HTTP based protocol designed to off-load specific content to dedicated servers. ICAP is generally used in proxy servers to integrate with third party products like anti-virus software, malicious content scanners and URL filters.
ICMP	Internet Control Message Protocol. An extension to the Internet Protocol (IP) that allows for the generation of error messages, test packets, and informational messages related to IP. It is defined in STD 5, RFC 792.
Live Blocking	ContentKeeper will classify previously unexplored URLs immediately, as they are browsed to. If a newly classified URL is classified under a category that you have configured to block then any further attempts to browse to that URL will be blocked. Any newly classified URLs are uploaded into the ContentKeeper Technologies Data Centre Database and made available globally. Refer to Globally Reclassified URLs.
Locally Reclassified URLs	URLs that have been reclassified within the local Control List. These are only available to local clients. Refer to Control List.
Memory	RAM – Random Access Memory. A data storage device for which the order of access to different locations does not affect the speed of access. This is in contrast to, say, a hard disk or magnetic tape where it is very much quicker to access data sequentially because accessing a non-sequential location requires physical movement of the storage medium rather than just electronic switching. RAM is also known as volatile memory as any data stored in it is lost when power is turned off.
Node	An addressable device attached to a computer network, more often called a "host". A node can be a computer or some other device, such as a printer. Every node has a unique network address, sometimes called a Data Link Control (DLC) address or Media Access Control (MAC) address.
NTLM/Basic Authentication Module	The ContentKeeper NTLM/Basic Authentication Module supports BASIC and NTLM authentication for web browsers along with Windows domain integration. The module is based on a custmoised version of the Squid HTTP Caching Proxy Server and is used primarily to provide username resolution to ContentKeeper.
Ping	It is often believed that PING is an abbreviation for Packet Internet Groper, but Ping's author has stated that the name was originally contrived to match submariners' term for the sound of a returned sonar pulse. PING is a utility used to test connectivity to destination hosts by sending them one, or repeated, ICMP (Internet Control Message Protocol) echo requests and waiting for and displaying any replies. In its most basic form, a PING command may be issued as ping 192.9.200.32, where 192.9.200.32 is the IP address of the desired host.
Port	A logical channel or channel endpoint in a communications system. The Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) used on Ethernet use port numbers to distinguish between (de-multiplex) different logical channels on the same network interface on the same computer. Each application program has a unique port number associated with it, defined in /etc/services or the Network Information Services "services" database. Some protocols, e.g. telnet and HTTP have default ports but can use other ports as well. Refer to Ethernet.
Promiscuous Mode	A mode of operation associated with Ethernet cards, where a card accepts all packets, regardless of their destination address, as opposed to normal operation where a card will only accept packets destined for it.
Proxy	Caching Proxy Server – A server that sits between a client application, such as a Web browser, and an actual server. When a caching proxy server receives a request for a URL, it looks for the URL in its local cache. If found, it returns the document immediately, otherwise it retrieves it from the remote server, saves a copy in the cache and returns it to the requester. The cache will usually have an expiry algorithm, which flushes documents according to their age, size, and access history.
RAM	RAM – Random Access Memory. A data storage device for which the order of access to different locations does not affect the speed of access. This is in contrast to, say, a hard disk or magnetic tape where it is very much quicker to access data sequentially because accessing a non-sequential location requires physical movement of the storage medium rather than just electronic switching. RAM is also known as volatile memory as any data stored in it is lost when power is turned off.
Router	A router is a device that acts like a bridge or a switch but provides more functionality. In moving data between different network segments, routers examine a packet header to determine the best path for the packet to travel. A router knows the path to all of the segments on the network by accessing information stored in a routing table. Routers enable all users in a network to share a single connection to the Internet or a WAN. Refer to Bridge and Switch.
Switch	Switches are similar to bridges but offer a more direct connection between the source and destination computers. When a switch receives a data packet, it creates a separate internal connection, or segment, between any two of it’s ports and forwards the data packet to the appropriate port of the destination computer only, based on information in the data packets header. This insulates the connection from other ports and gives the source and destination computers access to the full bandwidth of a network. Refer to Bridge.
VLAN	Virtual Local Area Network. A logical grouping of two or more nodes which are not necessarily on the same physical network segment but which share the same IP network number. Computers connected to a VLAN behave as if they are connected to the same wire even though they may actually be in different physical locations.
WCCP	Web Cache Co-ordination Protocol (WCCP) facilitates the link between Cisco IOS-enabled routers and cache engines. Through WCCP, cache engines can be clustered to provide scalability and resiliency. The protocol allows one or more proxies to register with a single router to receive (WCCP-GRE encapsulated) redirected traffic. It also allows one of the proxies, the designated proxy, to dictate to the router how redirected traffic is distributed across the array.