IP Videoconferencing Glossary

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C

Certified Firewalls: Since H.323-compliant applications use dynamically allocated sockets for audio, video and data channels, a firewall must be able to allow H.323 traffic through on an intelligent basis. The firewall must be either H.323-enabled with an H.323 proxy, or able to "snoop" to control channel to determine which dynamic sockets are in use for H.323 sessions, and allow traffic as long as the control channel is active. Both the Cisco PIX Firewall and Checkpoint Firewall-1 firewalls feature Set allow H.323 traffic through on an as-needed basis by "snooping" the control channel.

Click To Meet (CTM) Click To Meet^TM. A First Virtual Communications, Inc., product that combines a directory service for ISDN "H.320," ATM "H.321," and IP "H.323" endpoints in a multimedia environment.

CODEC: An acronym for COder/DECoder. In short, a codec is a piece of hardware or software that takes some signal (such as video or audio) and converts it to a format suitable for transportation using a specific set of protocols. Equipment on the receiving end must also use these same protocols. The H.323 standard is a collection of protocols designed to ensure compatibility between products of various manufacturers. Even though the term “codec” specifically refers to the hardware or software converter, the term has come to include the entire set of videoconferencing terminal equipment. Someone saying “codec” is most likely referring to a set of terminal equipment. The terms “videoconferencing terminal” and “codec” are used interchangeably.

CODEC ID:   This name can be descriptive such as a room name, BL-123, a location, Accounting Dept., or a person’s name.

D

DNS Name: The domain name system (DNS) is the way that Internet domain names are located and translated into Internet Protocol addresses. A domain name is a meaningful and easy-to-remember "handle" for an Internet address.

F

Firewall: A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks. (The term also implies the security policy that is used with the programs.) An enterprise with an intranet that allows its workers access to the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for controlling what outside resources its own users have access to.

Firewalls Frequently Asked Questions

Full Duplex: Sending data in both directions simultaneously "bidirectional" with a higher quality. In videoconferencing, full duplex will be much more natural and useable. Cheap speakerphones are half duplex, whereas more expensive ones are full duplex.

G

Gatekeeper: The gatekeeper is the brain of an H.323 network, performing essential control, administrative, and managerial functions. However, the gatekeeper does not route any data packets in a network. These continue to rely on standard network routing equipment. The primary purposes of a gatekeeper are address translation and zone administration using layer three of the OSI model.

Gateway: A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are gateway nodes. Can transcode or allow different protocols to talk to each other.

H

H.320: The ITU standard for videoconferencing over digital networks such as ISDN.

H.321:The ITU standard for adaptation of H.320 videoconferencing over digital networks such as B-ISDN.

H.323: The ITU standard for videoconferencing over packet switched networks such as LANs and the Internet.

H.323 ID: This name can be descriptive such as a room name, BL-123, a location, Accounting Dept., or a person’s name.

Half-Duplex: Transfers Data in both direction, but not simultaneously. Normal operation is alternate, one-way-at-a-time transmission.

Hub: Hub is a place of convergence where data arrives from one or more directions and is forwarded out in one or more other directions.

I

IP address: The IP address is usually expressed as four decimal numbers, each representing eight bits, separated by periods. This is sometimes known as the dot address and, more technically, as dotted quad notation. For Class A IP addresses, the numbers would represent "network.local.local.local"; for a Class C IP address, they would represent "network.network.network.local." The number version of the IP address can (and usually is) represented by a name or series of names called the domain name.

M

Multipoint Conference: The Multipoint Conference Unit (MCU) is an important part of any videoconferencing infrastructure, allowing three or more parties or persons to get together in a virtual meeting room.

N

NAT: Network Address Translation (NAT) is the translation of an Internet Protocol address (IP address) used within one network to a different IP address known within another network. One network is designated the inside network and the other is the outside. Typically, a company maps its local inside network addresses to one or more global outside IP addresses and unmaps the global IP addresses on incoming packets back into local IP addresses. This helps ensure security since each outgoing or incoming request must go through a translation process that also offers the opportunity to qualify or authenticate the request or match it to a previous request. NAT also conserves on the number of global IP addresses that a company needs and it lets the company use a single IP address in its communication with the world.

S

Switch : A switch is a network device that selects a path or circuit for sending a unit of data to its next destination.

Subnet Mask: The subnet mask is used to determine where the network number in an IP address ends and the node number in an IP address begins. A node is anything on a network that needs an IP address to communicate (a PC, server, router, etc).

T

Terminal Equipments

Room System
A room system is a vendor’s top of the line product designed to provide medium and large corporations, government, and educational institutions with custom room configurations. These systems are used in situations requiring high-quality video performance and extensive conferencing capabilities for applications such as distance learning, boardroom conferencing and high performance multi-site conferencing. Performance is based on providing IP data rates as fast as 2 Megabits per second. These systems typically support multiple video and audio inputs such as document cameras, computer video converters, and VCRs. Support for one to three video displays is also common. Complete systems may come with two or more 32” viewing monitors or can be used with larger projection systems. These systems can be permanently built into a room or set up as semi-mobile units that can be taken to another room if necessary. Some units even have built-in streaming services. The main advantages to these systems are video quality and built-in multipoint services.

Set-Top System
The term set-top system usually refers to a vendor’s mid-level product designed for small to medium sized conference rooms. This system can look just like the room system with monitors and carts, or it can be a smaller unit that sits on top of a monitor.  These systems typically will perform the same as the room systems at lower data rates; however, the set-top systems typically do not support data rates above 768K and do not have the built-in multipoint conference capability.  One advantage to the set-top solution is that products on the lower end of this pricing scale can give a user excellent conference room or classroom performance as long as they do not require the extra services or options offered by the room systems.

Desktop System
A desktop system, simply put, is a videoconferencing terminal, either hardware or software, that interacts directly with the personal computer on a desk. It is designed to be a one-person unit, making it unsuitable for a conference room environment; but it can be very useful for an office or classroom/lab-station solution. It will either connect through the USB port or will have a hardware card to be installed. The speed of the computer processor will directly affect performance. The advantage of such a unit is its low-cost focus on an individual user, with no special room or setup needed. Within minutes of installation, a user can talk face to face to someone using another desktop system or someone with a room system. The disadvantage to this type of system is that it is not designed for conference rooms.

Z

Zone Prefix: A prefix that identifies the addresses to be serviced by a given gatekeeper. Zone prefixes are typically area codes and serve the same purpose as the domain names in the H.323-ID address space.