Subject: AVoIP Glossary of Terms (v2)
Access Layer: Switch layer in the Cisco three-layer model through which users and devices gain access to the network.
AES-128: A specification for electronic data encryption developed by the U.S. National Institute of Standards and Technology.
Application Layer (OSI Model): Top layer of the OSI model responsible for communicating directly with the software interface.
Bandwidth: The rate at which data is transferred over a network, measured in bits per second.
Broadcast: A one-to-many transmission method, from a single host, to all receiving hosts within a specific broadcast domain.
Broadcast Domain: A domain in which broadcasted traffic will be forwarded to all ports. For example, all ports on a hub and a switch exist on the same broadcast domain. Routers break up broadcast domains by port.
Capped Variable Bitrate (CVBR): A method of encoding where a limit is placed on bandwidth usage.
The system can encode below that bandwidth but never exceed it.
Chrominance Subsampling: The process of reducing chrominance information but keeping luminance information. This causes a reduction in bandwidth, often with little to no impact on the video quality.
Cisco Three Layer Hierarchical Model: A three-layer network architecture used by Cisco to define enterprise networks. The three layers are: access, distribution, and core.
Collapsed Core Model: A simplified Cisco network architecture model that merges the core and distribution layers into a single layer.
Collision Domain: A domain in which network traffic has the potential for colliding and subsequently interrupting data transmission. For example, all ports on a hub exist on the same collision domain.
All ports on a switch or router create their own collision domain.
Color Space Conversion: The process of separating chrominance and luminance in an RGB signal during a RGB-to-YUV conversion. This process is also used during a YUV-to-RGB conversion.
Core Layer: Switch layer in the Cisco three-layer model that is responsible for routing traffic as quickly and efficiently as possible.
Data Link Layer (OSI Model): Layer 2 of the seven-layer OSI model that uses MAC (Media Access Control) addresses to route traffic on the local network.
Discrete Cosine Transform: Uses a series of cosine functions to express data in the frequency domain.
Discrete Wavelet Transform: Uses a series of frequencies and locations to represent data in the frequency domain.
Distribution Layer: The smart layer in the Cisco three-layer model that provides routing and filtering of traffic from the access layer.
Dynamic Host Configuration Protocol (DHCP): A means of automatically assigning IP addresses, subnet masks, gateway addresses and DNS server addresses to new hosts on a network.
Ethernet II Frame: Uses both source and destination MAC addresses for sending information within a local network.
Frame: The protocol data unit (PDU) of the data link layer.
Forward Error Correction (FEC)/SMPTE 2022-5: A real-time error correction method used for video and audio streaming applications. Information is transmitted alongside the standard video payload to rebuild packets on the other side in case of a packet loss.
H.264/MPEG 4 AVC: A type of intra/inter-frame compression that uses discrete cosine transforms. Common characteristics are low bit rates, lossy visual quality, and high latency (160 ms or greater).
H.265/HEVC: A type of intra/inter-frame compression that uses discrete cosine transforms.
This compression is similar to H.264/MPEG 4 AVC except with improved compression for larger resolutions, enabling efficient compression of 4K signals.
IGMP Querier: Switch that is managing the list of IGMP groups. This switch is responsible for adding/removing devices from IGMP groups as needed.
IGMP Snooping: The ability of a switch to inspect IGMP messages and determine whether to forward or block multicast traffic from connected switch ports.
Inter-Frame Compression: A compression which only compresses the parts of an image that have changed since the last frame.
Internet Group Management Protocol (IGMP): A layer 3 (network layer) protocol that manages subscriptions to multicast groups.
Internet Protocol (IP): A protocol that examines source and destination IP addresses, and determines the best path from source to destination.
Intra-Frame Compression: A compression which compresses each individual video frame separately and completely.
IP Address: A unique 32-bit address, written in dot-decimal notation, that is assigned to each device on a network.
JPEG 2000: A type of intra-frame compression that utilizes wavelet transforms. Common characteristics are medium latency (20 – 30 ms), visually lossless quality, and medium-sized bitrates (below 1 Gbps).
Latency: The time interval between data transmission and receipt.
Layer 2 Switch: A switch that operates primarily at layer 2 (data-link layer) of the OSI model. This switch works well as an access switch or as a standalone switch in a small business environment.
Layer 3 Switch: A switch that operates primarily at layer 3 (network layer) of the OSI model. This switch works well in multicast environments due to its support of layer 3 protocols like IGMP. Layer 3 switches also work well as a core or distribution switch in enterprise networks.
Local Area Networks (LAN): Networks that are scalable from a few devices to potentially thousands. However, as the name implies, these networks are usually contained to a single location.
Lossless Compression: A type of compression where the signal is lightly compressed and no information is lost in the process. A version of the original signal can be completely reconstructed at the receiving host.
Lossy Compression: A type of compression where the signal is compressed partially past the point of recovery at the end. Some information is lost, resulting in degradation of the original signal at the receiving host.
MAC Address: Media Access Control Address. Each device on a network is assigned a unique 48-bit MAC address.
Multicast: A one-to-many transmission method, from a single host, to all receiving hosts within a specific broadcast domain. The receiving hosts must be subscribed to the multicast group.
Multicast Address: Class D IP addresses from 220.127.116.11 through 18.104.22.168. It is important to note that the address range between 22.214.171.124 and 126.96.36.199 is reserved for other functions in a multicast network. These addresses should not be used in an OmniStream system.
Network: A collection of devices, such as computers, smartphones, tablets, and printers that can communicate with one another.
Network Layer (OSI Model): Uses IP Addresses to route traffic to different IP networks.
Open Systems Interconnection (OSI) Model: A seven-layer model developed by the International Organization for Standardization (ISO) defining how devices should communicate on a network.
Packet: The protocol data unit (PDU) of the network layer.
Physical Layer (OSI Model): A communication path between devices to send and receive bits over physical connections.
Presentation Layer (OSI Model): Layer of the OSI model that acts as a translator for any data passing through. This layer is responsible for data encryption or compression.
Protocol Data Units (PDU): Units of measure for data used, at different levels, by the OSI model.
Quality of Service (QoS): A method of managing network traffic priority.
Real Time Transport Control Protocol (RTCP): Provides Quality-of-Service (QoS) statistics as well as control information to help manage the RTP stream.
Real Time Transport Protocol (RTP): An application layer protocol for sending audio and video over a network. The common standard for most AV-over-IP solutions. Timestamps and sequence numbers are also added to “best-effort” UDP segments.
Repeater: A device that amplifies a signal to reach a greater distance than defined by the original hardware or device. This device functions as a hub with only two ports.
Router: Routes traffic to different IP networks using IP addresses. See also Layer 3 Switch.
Segment: The protocol data unit (PDU) of the transport layer.
Session Layer (OSI Model): Responsible for managing sessions of user data being transmitted at the same time, such as various tabs on a web browser.
Subnet: Splits up broadcast domains by partitioning networks into smaller groups of hosts.
Subnet Mask: A 32-bit address, written in dot-decimal notation, that defines which bits are being used as a subnet.
Switch: Routes traffic anywhere on a local network using MAC Addresses. See also Layer 2 Switch.
Transport Control Protocol (TCP): A connection-oriented transport protocol with error-checking, making it a highly-reliable protocol.
Transport Layer (OSI Model): Responsible for segmenting data and then reassembling it at the endpoint. The Transport Layer also establishes end-to-end communication between transmitting and receiving hosts.
Unicast: A one-to-one transmission method, from a single host to a single receiving host, within a specific broadcast domain.
User Datagram Protocol (UDP): A connectionless transport protocol with “best-effort” delivery and no error-correction.
VC-2/Dirac Pro: A type of inter-frame compression that utilize wavelet transforms. Common characteristics are low latency (9 ms), visually lossless quality, and medium sized bitrates (below 1 Gbps).
Virtual Local Area Networks (VLAN): A logical version of a LAN. Hardware is segmented logically using software to create multiple networks on a single switch or network.
Visually Lossless Compression (VLC): Although this type of compression causes some information to be lost, the difference is negligible to the human eye.
Wide Area Networks (WAN): Networks that span large geographical areas such as a university campus, a country, or even the world.
Article ID: KB01149