ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary - 19 Glossary Glossary PDU (Protocol Data Unit) - a unit of data specified in a layer protocol and consisting of proto- col control information and layer user data. Peak Cell Rate - at the PHY Layer SAP of a point-to-point VCC, the Peak Cell Rate Rpis the inverse of the minimum inter-arrival time T0 of the request to send an ATM-SDU. Peer Entities - entities within the same layer. PHY (Physical Layer) - the actual cards, wires, and/or fiber-optic cabling used to connect computers, routers, and switches. Physical Layer (PHY) Connection - an association established by the PHY between two or more ATM-entities. A PHY connection consists of the concatenation of PHY links in order to provide an end-to-end transfer capability to PHY SAPs. PLCP (Physical Layer Convergence Protocol) - a framing protocol that runs on top of the T1 or E1 framing protocol. PLM (Physical Layer Module) - interface card in the CellPath 300 that provides the logic to support the physical layer of the network link. A PLM has the actual physical port mounted on it. Various PLMs support various physical layers, such as OC-3c/STM1 or DS3. PLP (Packet Level Protocol) - Network layer protocol in the X.25 protocol stack. Sometimes called X.25 Level 3 or X.25 Protocol. See also X.25. PM (Protocol Module) - interface card in the CellPath 300 that provides the logic supporting the protocol layer of the network link. Various PMs support various protocols, such as ATM cell, Frame Relay, or CBR traffic. PMD (Physical Medium Dependent) - a sublayer concerned with the bit transfer between two network nodes. It deals with wave shapes, timing recovery, line coding, and electro-optic conversions for fiber based links. PNNI (Private Network Node Interface or Private Network-to-Network Interface) - a proto- col that defines the interaction of private ATM switches or groups of private ATM switches ping (Packet Internet Groper) - a program used to test reachability of destinations by send- ing them an ICMP echo request and waiting for a reply. Point-to-Multipoint Connection - a collection of associated ATM VC or VP links, with associ- ated endpoint nodes, with the following properties: 1. One ATM link, called the Root Link, serves as the root in a simple tree topology. When the Root node sends information, all of the remaining nodes on the connection, called Leaf nodes, receive copies of the information. 2. Each of the Leaf Nodes on the connection can send information directly to the Root Node. The Root Node cannot distinguish which Leaf is sending information without additional (higher layer) information. (See the following note for Phase 1.) 3. The Leaf Nodes cannot communicate directly to each other with this connection type. Glossary - 20 ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary Note: Phase 1 signalling does not support traffic sent from a Leaf to the Root. Point-to-Point Connection - a connection with only two endpoints. Point of Demarcation - the dividing line between a carrier and the customer premise that is governed by strict standards that define the characteristics of the equipment on each side of the demarcation. Equipment on one side of the point of demarcation is the responsibility of the customer. Equipment on the other side of the point of demarcation is the responsibility of the carrier. Policing - the function that ensures that a network device does not accept traffic that exceeds the configured bandwidth of a connection. Primitive - an abstract, implementation-independent interaction between a layer service user and a layer service provider. Priority - the parameter of ATM connections that determines the order in which they are reduced from the peak cell rate to the sustained cell rate in times of congestion. Connections with lower priority (4 is low, 1 is high) are reduced first. PROM (Programmable Read-Only Memory) - a chip-based information storage area that can be recorded by an operator but erased only through a physical process. Protocol - a set of rules and formats (semantic and syntactic) that determines the communica- tion behavior of layer entities in the performance of the layer functions. Protocol Control Information - the information exchanged between corresponding entities using a lower layer connection to coordinate their joint operation. Proxy - the process in which one system acts for another system to answer protocol requests. Proxy Agent - an agent that queries on behalf of the manager, used to monitor objects that are not directly manageable. PSN (Packet Switched Network) - a network designed to carry data in the form of packets. The packet and its format is internal to that network. PT (Payload Type) - bits 2…4 in the fourth byte of an ATM cell header. The PT indicates the type of information carried by the cell. At this time, values 0…3 are used to identify various types of user data, values 4 and 5 indicate management information, and values 6 and 7 are reserved for future use. PVC (Permanent Virtual Circuit (or Channel)) - a circuit or channel through an ATM net- work provisioned by a carrier between two endpoints; used for dedicated long-term informa- tion transport between locations. Q.2931 - Derived from Q.93B, the narrowband ISDN signalling protocol, an ITU standard describing the signalling protocol to be used by switched virtual circuits on ATM LANs. Real-Time Clock - a clock that maintains the time of day, in contrast to a clock that is used to time the electrical pulses on a circuit. ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary - 21 Glossary Glossary Relaying - a function of a layer by means of which a layer entity receives data from a corre- sponding entity and transmits it to another corresponding entity. RFCs (Requests For Comment) - IETF documents suggesting protocols and policies of the Internet, inviting comments as to the quality and validity of those policies. These comments are collected and analyzed by the IETF in order to finalize Internet standards. RFI (Radio Frequency Interference) - the unintentional transmission of radio signals. Com- puter equipment and wiring can both generate and receive RFI. RIP (Routing Information Protocol) - a distance vector-based protocol that provides a mea- sure of distance, or hops, from a transmitting workstation to a receiving workstation. RISC (Reduced Instruction Set Computer) - a generic name for CPUs that use a simpler instruction set than more traditional designs. Router - a device that forwards traffic between networks or subnetworks based on network layer information. RTS (Request To Send) - an RS-232 modem interface signal (sent from the DTE to the modem on pin 4) which indicates that the DTE has data to transmit. SBus - hardware interface for add-in boards in later-version Sun 3 workstations. SAP (Service Access Point) - the point at which an entity of a layer provides services to its LM entity or to an entity of the next higher layer. SAR (Segmentation And Reassembly) - the SAR accepts PDUs from the CS and divides them into very small segments (44 bytes long). If the CS-PDU is less than 44 bytes, it is padded to 44 with zeroes. A two-byte header and trailer are added to this basic segment. The header identifies the message type (beginning, end, continuation, or single) and contains sequence numbering and message identification. The trailer gives the SAR-PDU payload length, exclu- sive of pad, and contains a CRC check to ensure the SAR-PDU integrity. The result is a 48-byte PDU that fits into the payload field of an ATM cell. SC - CellPath 300 System Controller; paired with the Extension Module (EM). SCR (sustainable cell rate) - parameter defined by the ATM Forum for ATM traffic manage- ment. For VBR connections, SCR determines the long-term average cell rate that can be trans- mitted. SCSI (Small Computer Systems Interface) - a standard for a controller bus that connects disk drives and other devices to their controllers on a computer bus. It is typically used in small systems. SDLC (Synchronous Data Link Control) - IBM’s data link protocol used in SNA networks. SDU (Service Data Unit) - a unit of interface information whose identity is preserved from one end of a layer connection to the other. Glossary - 22 ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary SEAL (Simple and Efficient Adaptation Layer) - also called AAL 5, this ATM adaptation layer assumes that higher layer processes will provide error recovery, thereby simplifying the SAR portion of the adaptation layer. Using this AAL type packs all 48 bytes of an ATM cell information field with data. It also assumes that only one message is crossing the UNI at a time. That is, multiple end-users at one location cannot interleave messages on the same VC, but must queue them for sequential transmission. Segment - a single ATM link or group of interconnected ATM links of an ATM connection. Semipermanent Connection - a connection established via a service order or via network management. SES (Severely Errored Seconds) - a second during which more event errors have occurred than the SES threshold. SF (Superframe) - Common framing type used on T1 circuits. SF consists of 12 frames of 192 bits each, with the 193rd bit providing error checking and other functions. SF has been super- seded by ESF, but is still widely used. Also called D4 framing. See also ESF. SGMP (Simple Gateway Management Protocol) - the predecessor to SNMP. Shaping Descriptor - n ordered pairs of GCRA parameters (I,L) used to define the negotiated traffic shape of an APP connection. The traffic shape refers to the load-balancing of a network. In this context, load-balancing means configuring the data flows to maximize the efficiency of the network. SIR (Sustained Information Rate) - the long-term average data transmission rate across the User-to-Network Interface. SMDS (Switched Multimegabit Data Service) - a high-speed, datagram-based, public data network service expected to be widely used by telephone companies in their data networks. SMTP (Simple Mail Transfer Protocol) - the Internet electronic mail protocol used to transfer electronic mail between hosts. SNAP - SubNetwork Access Protocol SNMP (Simple Network Management Protocol) - the Internet standard protocol for manag- ing nodes on an IP network. snmpd - an SMNP agent for a given adapter card. SONET (Synchronous Optical Network) - a new and growing body of standards that defines all aspects of transporting and managing digital traffic over optical facilities in the public net- work. Source Traffic Descriptor - a set of traffic parameters belonging to the ATM Traffic Descrip- tor used during the connection set-up to capture the intrinsic traffic characteristics of the con- nection requested by the source. ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary - 23 Glossary Glossary Spanning Tree Protocol - provides loop-free topology in a network environment where there are redundant paths. SPANS (Simple Protocol for ATM Network Signalling) - FORE Systems’ proprietary signal- ling protocol used for establishing SVCs between FORE Systems equipment. SPARC (Scalable Processor Architecture Reduced instruction set Computer) - a power- ful workstation similar to a reduced-instruction-set-computing (RISC) workstation. SPE (Synchronous Payload Envelope) - the payload field plus a little overhead of a basic SONET signal. SPVC (Smart PVC) - a generic term for any communications medium which is permanently provisioned at the end points, but switched in the middle. In ATM, there are two kinds of SPVCs: smart permanent virtual path connections (SPVPCs) and smart permanent virtual channel connections (SPVCCs). Static Route - a route that is entered manually into the routing table. Statistical Multiplexing - a technique for allowing multiple channels and paths to share the same link, typified by the ability to give the bandwidth of a temporarily idle channel to another channel. STM (Synchronous Transfer Mode) - a transport and switching method that depends on information occurring in regular and fixed patterns with respect to a reference such as a frame pattern. STP (Shielded Twisted Pair) - two or more insulated wires that are twisted together and then wrapped in a cable with metallic braid or foil to prevent interference and offer noise-free transmissions. STS (Synchronous Transport Signal) - a SONET electrical signal rate. Sublayer - a logical subdivision of a layer. Super User - a login ID that allows unlimited access to the full range of a device’s functional- ity, including especially the ability to reconfigure the device and set passwords. SVC (Switched Virtual Circuit (or Channel)) - a channel established on demand by network signalling, used for information transport between two locations and lasting only for the duration of the transfer; the datacom equivalent of a dialed telephone call. Switched Connection - a connection established via signalling. Symmetric Connection - a connection with the same bandwidth value specified for both directions. Synchronous - signals that are sourced from the same timing reference and hence are identi- cal in frequency. Glossary - 24 ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary Systems Network Architecture (SNA) - a proprietary networking architecture used by IBM and IBM-compatible mainframe computers. T1 - a specification for a transmission line. The specification details the input and output char- acteristics and the bandwidth. T1 lines run at 1.544 Mbps and provide for 24 data channels. In common usage, the term “T1” is used interchangeably with “DS1.” T3 - a specification for a transmission line, the equivalent of 28 T1 lines. T3 lines run at 44.736 Mbps. In common usage, the term “T3” is used interchangeably with “DS3.” Tachometer - in ForeView, the tachometer shows the level of activity on a given port. The num- ber in the tachometer shows the value of a chosen parameter in percentage, with a colored bar providing a semi-logarithmic representation of that percentage. TAXI (Transparent Asynchronous Transmitter/Receiver Interface) - Encoding scheme used for FDDI LANs as well as for ATM; supports speeds of up to 100 Mbps over multimode fiber. TC (Transmission Convergence) - generates and receives transmission frames and is respon- sible for all overhead associated with the transmission frame. The TC sublayer packages cells into the transmission frame. TCP (Transmission Control Protocol) - a specification for software that bundles and unbun- dles sent and received data into packets, manages the transmission of packets on a network, and checks for errors. TCP/IP (Transmission Control Protocol/Internet Protocol) - a set of communications proto- cols that has evolved since the late 1970s, when it was first developed by the Department of Defense. Because programs supporting these protocols are available on so many different computer systems, they have become an excellent way to connect different types of computers over networks. TDM (Time Division Multiplexing) - a method of traditional digital multiplexing in which a signal occupies a fixed, repetitive time slot within a higher-rate signal. Telnet - a TCP/IP protocol that defines a client/server mechanism for emulating directly-con- nected terminal connections. Token Ring - a network access method in which the stations circulate a token. Stations with data to send must have the token to transmit their data. topology - a program that displays the topology of a FORE Systems ATM network. An updated topology can be periodically re-displayed by use of the interval command option. Traffic - the calls being sent and received over a communications network. Also, the packets that are sent on a data network. Trailer - the protocol control information located at the end of a PDU. ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary - 25 Glossary Glossary Transit Delay - the time difference between the instant at which the first bit of a PDU crosses one designated boundary, and the instant at which the last bit of the same PDU crosses a sec- ond designated boundary. trap - a program interrupt mechanism that automatically updates the state of the network to remote network management hosts. The SNMP agent on the switch supports these SNMP traps. UAS (Unavailable Seconds) - a measurement of signal quality. Unavailable seconds start accruing when ten consecutive severely errored seconds occur. UBR (Unspecified Bit Rate) - a type of traffic that is not considered time-critical (e.g., ARP messages, pure data), allocated whatever bandwidth is available at any given time. UBR traf- fic is given a “best effort” priority in an ATM network with no guarantee of successful trans- mission. UDP (User Datagram Protocol) - the TCP/IP transaction protocol used for applications such as remote network management and name-service access; this lets users assign a name, such as “RVAX*2,S,” to a physical or numbered address. Unassigned Cells - a generated cell identified by a standardized virtual path identifier (VPI) and virtual channel identifier (VCI) value, which does not carry information from an applica- tion using the ATM Layer service. UNI (User-to-Network Interface) - the physical and electrical demarcation point between the user and the public network service provider. UNI 3.0 - the User-to-Network Interface standard set forth by the ATM Forum that defines how private customer premise equipment interacts with private ATM switches. UPC (Usage Parameter Control) - the mechanism that ensures that traffic on a given connec- tion does not exceed the contracted bandwidth of the connection. UPC is responsible for polic- ing or enforcement. UPC is sometimes confused with congestion management, to which it is functionally related on the CellPath 300 (see congestion management). UTP (Unshielded Twisted Pair) - a cable that consists of two or more insulated conductors in which each pair of conductors are twisted around each other. There is no external protection and noise resistance comes solely from the twists. V.35 - ITU-T standard describing a synchronous, physical layer protocol used for communica- tions between a network access device and a packet network. V.35 is most commonly used in the United States and Europe, and is recommended for speeds up to 48 Kbps. VBR (Variable Bit Rate) - a type of traffic that, when sent over a network, is tolerant of delays and changes in the amount of bandwidth it is allocated (e.g., data applications). VC (Virtual Channel (or Circuit)) - a communications path between two nodes identified by label rather than fixed physical path. Glossary - 26 ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary VCC (Virtual Channel Connection) - a unidirectional concatenation of VCLs that extends between the points where the ATM service users access the ATM Layer. The points at which the ATM cell payload is passed to, or received from, the users of the ATM Layer (i.e., a higher layer or ATMM-entity) for processing signify the endpoints of a VCC. VCI (Virtual Channel Identifier) - the address or label of a VC; a value stored in a field in the ATM cell header that identifies an individual virtual channel to which the cell belongs. VCI values may be different for each data link hop of an ATM virtual connection. VCL (Virtual Channel Link) - a means of unidirectional transport of ATM cells between the point where a VCI value is assigned and the point where that value is translated or removed. VINES (Virtual Network Software) - Banyan’s network operating system based on UNIX and its protocols. Virtual Channel Switch - a network element that connects VCLs. It terminates VPCs and translates VCI values. The Virtual Channel Switch is directed by Control Plane functions and relays the cells of a VC. Virtual Connection - an endpoint-to-endpoint connection in an ATM network. A virtual con- nection can be either a virtual path or a virtual channel. Virtual Path Switch - a network element that connects VPLs, it translates VPI (not VCI) values and is directed by Control Plane functions. The Virtual Path Switch relays the cells of a Virtual Path. VPT (Virtual Path Terminator) - a system that unbundles the VCs of a VP for independent processing of each VC. VP (Virtual Path) - a unidirectional logical association or bundle of VCs. VPC (Virtual Path Connection) - a concatenation of VPLs between virtual path terminators (VPTs). VPCs are unidirectional. VPDN (Virtual Private Data Network) - a private data communications network built on pub- lic switching and transport facilities rather than dedicated leased facilities such as T1s. VPI (Virtual Path Identifier) - the address or label of a particular VP; a value stored in a field in the ATM cell header that identifies an individual virtual path to which the cell belongs. A virtual path may comprise multiple virtual channels. VPL (Virtual Path Link) - a means of unidirectional transport of ATM cells between the point where a VPI value is assigned and the point where that value is translated or removed. VPN (Virtual Private Network) - a private voice communications network built on public switching and transport facilities rather than dedicated leased facilities such as T1s. VT (Virtual Tributary) - a structure used to carry payloads such as DS1s that run at signifi- cantly lower rates than STS-1s. WAN (Wide-Area Network) - a network that covers a large geographic area. ForeRunner HE/200E/LE ATM Adapters for the PC User’s Manual Glossary - 27 Glossary Glossary Warm Start Trap - a CellPath 300 SNMP trap that indicates that SNMP alarm messages or agents have been enabled. Yellow Alarm - an alarm that occurs on a device when the signal from the device is not received at the far-end. X.21 - ITU-T standard for serial communications over synchronous digital lines. The X.21 pro- tocol is used primarily in Europe and Japan. X.25 - ITU-T standard that defines how connections between DTE and DCE are maintained for remote terminal access and computer communications in PDNs. X.25 specifies LAPB, a data link protocol, and PLP, a network layer protocol. Frame Relay has, to some degree, super- seded X.25. See also Frame Relay, LAPB, and PLP.

From:-

ForeRunner HE/200E/LE
ATM Adapters for the PC
User’s Manual
MANU0177-04 - Rev. A - February, 1999