Packet - An ordered group of data and control signals transmitted through a network, as a subset of a larger message.
Packet Switching - A data transmission technique, which divides user information into discrete data envelopes called packets, and sends the information packet by packet.
Parity Bit - An additional non-information bit added to a group of bits to ensure that the total number of l bits in the character is even or odd.
Payload - The 48-byte segment of the ATM cell containing user data. Any adaptation of user data via the AAL will take place within the payload.
PBX (Private Branch Exchange) - A private telephone switching system, usually serving an organization, such as a business or a government agency, and is usually located on the customer’s premises.
PHY (Physical layer) - The bottom layer of the ATM protocol reference model, it is subdivided into two sublayers: Transmission Convergence (TC) and Physical Medium (PM). It provides ATM cell transmission over the physical interfaces that interconnect the ATM devices.
Physical Layer - Layer 1 of the OSI model. The layer concerned with electrical, mechanical, and handshaking procedures over the interface connecting a device to the transmission medium.
Policing - A method for verifying that the incoming VC complies with the user’s service contract.
PON (Passive Optical Network) - A high bandwidth, point-to-multipoint optical fiber network based on ATM, Ethernet or TDM. In this type of optical network, wavelengths of light are divided into timeslots so that each wavelength can be shared by a number of users. With PONs, a single fiber from the carrier’s exchange can service 16, 32 or more buildings through the use of both passive devices to split the optical signal, and PON protocols to control the sending and transmission of signals across the shared access facility.
PoP (Point of Presence) – An access point to the rest of the network.
Port - The physical interface to a computer, multiplexer, for connection of terminals and modems.
PPP (Point-to-Point Protocol) - Provides a standard means of encapsulating data packets sent over a single-channel WAN link. It is the standard WAN encapsulation protocol for the interoperability of bridges and routers over synchronous or asynchronous circuits.
Prioritization - Also called CoS (class of service), classifies traffic into categories such as high, medium, and low. The lower the priority, the more “drop eligible” is a packet. E-mail and Web traffic are often placed in the lowest categories. When the network gets busy, prioritization ensures critical or high-rated traffic is passed first, and packets from the lowest categories may be dropped.
Protocol - A formal set of conventions governing the formatting and relative timing of message exchange between two communicating systems.
Pseudowire - Point-to-point connections set up between pairs of Provider Edge routers. Their primary function is to emulate (typically layer 2) native services like ATM, Frame Relay, Ethernet, low-rate TDM, or SONET/SDH over an underlying common packet switched network (MPLS, IP, or L2TPv3) network core. To achieve this, each of these technologies is encapsulated into a common MPLS format. Pseudowires are defined by the IETF PWE3 (Pseudowire Edge to Edge Emulation) WG.
PSTN (Public Switched Telephone Network) - The telecommunications network commonly accessed by ordinary telephones, key systems, PBX trunks and data equipment.
Q
Q-in-Q - See MAC-in-MAC.
QoS (Quality of Service) - Refers to the capability of a network to provide better service to selected network traffic over various technologies, including Frame Relay, Asynchronous Transfer Mode (ATM), Ethernet and 802.1 networks.
R
RADIUS (Remote Authentication Dial-In User Service) - An authentication, authorization and accounting protocol for applications such as network access or IP mobility. Many network services require the presentation of security credentials (such as a username and password or security certificate) in order to connect to the network. Before access to the network is granted, this information is passed to a network access server (NAS) device over the link-layer protocol, then to a RADIUS server over the RADIUS protocol. The RADIUS server checks that the information is correct using authentication schemes like PAP, CHAP or EAP.
RADview - The RADview Graphical User Interface (GUI) is an SNMP-based management system enabling complete monitoring and control of LAN and WAN networks from a central management station. The system provides direct on-line supervision, configuration and diagnostics.
Redundancy/Redundant Card or Power - Backup components used to ensure uninterrupted operation of a system in case of a failure.
Router - An interconnection device that connects individual LANs. Unlike bridges, which logically connect at OSI layer 2, routers provide logical paths at OSI layer 3. Like bridges, remote sites can be connected using routers over dedicated or switched lines to create WANs.
Routing - The process of selecting the most efficient circuit path for a message.
RSVP (Resource reSerVation Protocol) - A protocol developed for supporting different QoS classes for IP applications.
S
SDH (Synchronous Data Hierarchy) - The European standard for using optical media as the physical transport for high speed long-haul networks.
SFP - The Small Form-factor Pluggable (SFP) is a compact optical transceiver used in telecom and datacom applications. It is a popular industry format supported by most fiber optic component vendors. The primary advantages of this approach are hot pluggability, field replacabilty, and mix and match optical reach and type. Using the SFP platform, RAD has engineered a "System on an SFP" for extension of Ethernet and LAN over E1/T1 and E3/T3 connections
SHDSL- SHDSL, (ITU-T G.991.2, Single-pair High-speed Digital Subscriber Line), is a standardized method of extending the range of copper telephone lines for broadband services. SHDSL technology is used to transport data symmetrically at rates of 192 kbps to 2.3 Mbps over 2-wire, or 384 kbps to 4.6 Mbps over 4-wire. The latest SHDSL standard is SHDSL.bis. Based on ITU-T G.991 and ETSI TS 101524, SHDSL.bis uses TC-PM 16 or TC-PAM 32 line coding and multi-pair bonding technology to reach transmission rates up to 5.69 Mbps on 1 pair (2-wire) for a rate up to 22.8 Mbps over 8-wire.
Single Mode - Describing an optical wave-guide or fiber that is designed to propagate light of only a single wavelength (typically 5-10 microns in diameter).
SLA (Service Level Agreement) - A formal negotiated agreement between customers and their service provider, or between service providers. It records the common understanding about services, priorities, responsibilities, guarantees, etc. with the main purpose to agree on the level of service. For example, it may specify the levels of availability, serviceability, performance, operation, or other attributes of the service like billing and even penalties in the case of violation of the SLA.
SME - Small to Medium-sized Enterprise or business.
SNMP (Simple Network Management Protocol) - The Internet standard protocol for managing nodes on an IP network.
SONET (Synchronous Optical Network) - A North American standard for using optical media as the physical transport for high-speed long-haul networks. SONET basic speeds start at 51.84 Mbps and go up to 2.5 Gbps.
SSH (Secure Shell) - A network protocol that allows data to be exchanged over a secure channel between two computers. Encryption provides confidentiality and integrity of data.
Glossary
