A path name that starts with a slash (/); specifies a file that can be found by starting at the root of the file system and traversing the file tree.

A specific date or time of day; specified in the following format: [dd-mmm-yyyy] [:hh:mm:ss:cc] .

The description of a data structure that is independent of host structures or codes.

The language used by ISO protocols for describing abstract syntax. Most notable use in TCP/IP is for Simple Network Management Protocol (SNMP). The rules of ASN.1 are independent of the encoding techniques used to represent them.

A character string with login information that validates connect or login at a remote host.

A list that defines the kinds of access to be granted or denied to users.

A set of privileges that determines what users can do.

See acknowledgment.

A type of message sent to indicate that a block of data arrived at its destination without error. A control bit (acknowledgment flag) in the TCP header indicates that the acknowledgment number field is significant for each segment in a packet.

See access control list.

See ancillary control process.

A port that is bound to a process.

A number or group of numbers that uniquely identifies a network node within its own network or internet. See also IP address and hardware address.

A 32-bit value used to identify which bits in an IP address correspond to the network and subnet portions of the address.

The process of relating an IP address to a hardware address, when both refer to the same device, for example, conversion of an IP address into the corresponding Ethernet, Token Ring, or FDDI hardware address. This may require broadcasting on a local network. See also Address Resolution Protocol.

The TCP/IP protocol that dynamically binds an IP address to a hardware address such as an Ethernet or FDDI address; limited to physical network systems that support broadcast packets that can be heard by all hosts on a single, physical network. See also proxy ARP.

The function that ensures that network systems are correctly identified at all times.

The authority, such as the American National Standards Institute (ANSI), responsible for assigning Network Interface layer addresses within an addressing domain.

A level in a hierarchy of Network Interface layer addresses.

A single connection to an adjacent node; collection of state information representing a node in the local node's routing databases.

A relationship formed between selected neighboring routers for the purpose of exchanging routing information. Not every pair of neighboring routers becomes adjacent.

An address that identifies a local subnet access point and a subnet address of an adjacent system.

The nodes with direct lines between them; can communicate without an intermediate system. For example, all nodes on an Ethernet LAN are adjacent to each other.

A group of hosts, routers, and networks operated and managed by a single organization. Routing within an administrative domain is based on a consistent technical plan. An administrative domain is viewed from the outside, for purposes of routing, as a cohesive entity, of which the internal structure is unimportant. Information passed by other administrative domains is trusted less than information from one's own administrative domain.

A field in the Router Discovery Protocol router advertisement message that indicates how long advertisement addresses are valid. A lifetime of zero indicates that one or more addresses are no longer valid.

A data packet that is discarded because it exceeded the maximum number of hops while being forwarded through the network.

A system that acts on behalf of another system. (1) Client/server model: Part of the system that initiates, prepares, and exchanges information preparation on behalf of a client or server application. (2) Network management: Portion of an entity that responds to management requests and/or preprogrammed trap.

The portion of an agent responsible for the agent's end of SNMP.

The instance of a connection between a client or director and a server or agent.

An address that specifies the information needed by a director to establish communications with the agent's management interface.

The attributes maintained by the agent. The attributes do not cross the internal management interface.

See throughput.

A name, usually easy to remember, that is translated from a different name, usually difficult to remember. Most often used as an optional alternate name for a host. See also host name.

An optional node name used by some or all nodes in an OpenVMS Cluster that allows them to be treated as one node.

The internet address notation that conveys the same information as the common notation, but consists of two parts: network and host.

The organization that coordinates U.S. standards in many areas, including computers and communications.

The standard character set that assigns an octal sequence to each letter, number, and selected control characters.

The process that acts as an interface between user software and an I/O driver. The process provides functions supplementary to those performed in the driver, such as file and directory management.

A convention of the File Transfer Protocol that allows a user who does not have explicit authorization to transfer files to and from a host without the need for an account and password. The user usually logs in with a generic user ID and an e-mail address as password.

See American National Standard Institute.

See Application Programming Interface.

A program that provides functionality for end users of systems.

The top-most layer in the Internet architecture model where the user interacts with an application such as Network File Service (NFS), File Transfer Protocol (FTP), and mail.

A part of a distributed application running on a single host.

A standardized set of routines that makes system functions available to programmers.

The structure of a system, a description of which can be used to recreate the system.

See address resolution protocol.

See American Standard Code for Information Interchange.

The numbers officially assigned as part of the Internet standards.

The method for dynamic allocation of bandwidth using a fixed-size packet (called a cell). Also known as fast packet.

The mode of transmission in which the time intervals between character transmissions differ. Each character is surrounded by start and stop bits to allow the receiving device to recognize the beginning and end of each character (also called start-stop transmission).

See asynchronous transfer mode.

The controllable or observable part of an entity; a variable that network managers and applications programmers can manipulate for optimal performance.

A named collection of attributes grouped together, such as all information relating to errors.

Verification of the identity of a person or process attempting to access a system.

The software that searches the proxy database for valid user and group identification for remote personal computer users and returns them to PC-NFS.

A name server is said to have authority for a zone. That is, the name server has complete information about a part of a domain space for which the name server is considered to be the authority. A name server may be the authority for one or more zones. Authority for a domain space may be delegated to one or more zones.

In response to an nslookup or a resolver query, an answer is an authoritative answer if a server queries the authority for the zone and returns the answer. A server returns a nonauthoritative answer when the server's answer comes from its own cache.

A group of independent computer systems that trust each other regarding routing and reachability information; members believe information provided by other members in preference to information received from systems that are not part of the confederation.

A collection of networks controlled by one administrative authority. The gateways within this system are expected to trust one another and to share and update routing information among themselves by any mutually agreeable protocol. A core gateway must also be designated to share routing information with other autonomous systems by means of an External Gateway Protocol. See also External Gateway Protocol.

A set of routers under a single technical administration, using an interior gateway protocol and common metrics to route packets within the AS, and using an exterior gateway protocol to route packets to other ASs. Since this classic definition was developed, it has become common for a single AS to use several interior gateway protocols and sometimes several sets of metrics within an AS.

The use of the term autonomous system stresses that even when multiple internal gateway protocols and metrics are used, the administration of an AS appears to other ASs to have a single coherent interior routing plan and presents a consistent picture of what networks are reachable through it. The AS is represented by a number between 1 and 65534, assigned by the Internet Assigned Numbers Authority.

The process of mounting NFS file systems on an as-needed basis. The NFS file system automatically unmounts after a period of inactivity on the file system. (The default is 5 minutes.) You specify file systems to be automounted in the automounts map file.

The Compaq TCP/IP Services for OpenVMS software that runs as a background process and listens for incoming requests for services. When it receives a request, it runs the appropriate server application; includes inetd, security, and logging options.

The proportion of time a specific piece of equipment, system, or network is usable, compared to the total time it is expected to be.

The primary connectivity mechanism of a hierarchical distributed system. Usually a high-speed high-performance network that links together other networks into an internetwork. All systems with connectivity to an intermediate system on the backbone will connect to each other. This does not prevent systems from setting up private arrangements with each other to bypass the backbone for reasons of cost, performance, or security.

In the UNIX environment, the default mount option is to retry remote mount requests in the foreground. If during a boot process, any server listed in /etc/fstab is not currently available, the local system will not finish booting until the server becomes available. With background mounting, a remote mount request is executed once in a foreground process. If the mount request fails, the request is retried in a background process. This allows the local system to continue the boot procedure without waiting for the server to become available.

(1) Technically: The difference, in Hertz (Hz), between the highest and lowest frequencies of a transmission channel. (2) Typically: The amount of data that can be sent through a communications circuit.

A characteristic of any network technology that uses a single carrier frequency and requires all stations attached to the network to participate in every transmission; only one communication channel is provided at a time. See also broadband.

See Bulletin Board System.

The implementation of a DNS server developed and distributed by the University of California at Berkeley. Host name and address lookup service for the Internet; implemented in a client/server model. The client software, referred to as the resolver, allows client systems to obtain host names and addresses from servers rather than from locally hosted databases.

The derivation of the original UNIX operating system developed by the Computer Systems Research Group of the Department of Electrical Engineering and Computer Science at the University of California at Berkeley. The Compaq UNIX operating system is based on the BSD version of UNIX.

A characteristic of network technologies that will attempt to deliver data but will not try to recover if there is an error such as a line failure. Internet protocols IP and UDP provide best-effort delivery service to application programs.

The Compaq TCP/IP Services for OpenVMS implementation of a network device driver. See also device driver.

See Border Gateway Protocol.

The format for storage or transmission of binary data in which the most significant bit (or byte) comes first. The reverse convention is called little endian.

A set of library routines compiled into a client application like telnet or ftp that formulates a query to ask a name server to look up name and address information.

The software that responds to queries from BIND resolvers for name and address lookups; can be local or distributed. See also cache server, forwarder server, primary server, and secondary server.

Defining a remote file system to be a part of the local OpenVMS file system.

The measure of the rate of data transmission.

A contiguous unit of user information grouped together for transmission, such as the user data within a packet, excluding the protocol overhead.

A database file that BIND servers use to determine their type, the zones for which they have authority, and the location of other BIND database files.

The mnemonic for Bootstrap protocol. The protocol used for booting diskless systems remotely to a network. See also remote boot.

A Compaq TCP/IP Services for OpenVMS database with entries for diskless network clients that depend on a boot server to download their operating system images.

The interautonomous system routing protocol used to exchange network reachability information between autonomous systems. BGP runs over TCP.

One of a class of exterior gateway protocols, described in more detail in the BGP section of UNIX reference page gated.proto(4).

A point in the network where traffic is delayed or blocked. Bottlenecks are the limiting factors in network performance.

An I/O function specifying a port number and IP address for the device socket to bind a port to a process.

See bits per second.

A device that connects two or more physical networks and then stores and forwards complete packets between them. A bridge can usually be made to filter packets (that is, to forward only certain traffic).

A characteristic of any network that multiplexes multiple, independent network carriers onto a single cable; usually using frequency division multiplexing. Broadband technology allows several networks to coexist on one single cable; traffic from one network does not interfere with traffic from another because the "conversations" happen on different frequencies.

A delivery system where a copy of a packet is sent simultaneously to many hosts; can be implemented with hardware (for example, as in Ethernet) or with software (for example, as in Cypress). See also multicast.

The address that designates all hosts on a physical network. The broadcast address contains a hostid of all ones.

A type of multicast addressing in which all nodes receive a message simultaneously.

A circuit on which multiple nodes are connected. A message can be transmitted to multiple receivers, and all nodes are adjacent.

An end node connected to the same broadcast circuit as the local node. See also adjacency.

An intermediate system (router) connected to the same broadcast circuit as the local node. See also adjacency.

A mask used to interpret the IP address as a broadcast address.

An incorrect packet broadcast on a network that causes most hosts to respond all at once, typically with wrong answers that start the process over again.

A bridge/router; a device that forwards messages between networks at both network and data link levels.

See Berkeley Software Distribution.

A message database where people can log in and leave broadcast messages for others grouped (typically) into topic groups.

A device or an area of memory used for temporary storage when transmitting data from one device to another. Compensates for a difference in rate of data flow or in time of occurrence of events. Used on routing nodes to temporarily store data that is to be forwarded from one node to another.

The number of buffers provided at one time by the network software to handle data. Level can be single or multiple. Single buffering tends to be less efficient than multibuffering but uses less memory on the local system. Multibuffering provides better performance, and a network can send or process several buffers of data in quick succession.

(1) A LAN topology in which all nodes connect to a single transmission medium. All nodes are equal, and all nodes hear all transmissions on the medium. Bus topologies are reliable because failure of a node does not affect the ability of other nodes to transmit and receive. (2) A flat, flexible cable consisting of many transmission lines or wires used to interconnect computer system components to provide communication paths for addresses, data, and control information.

A portion of a computer's RAM reserved to act as a temporary memory for items read from a disk. These items become instantly available to the user.

A BIND server that has no authority for any zone; acquires information in the process of resolving clients' queries and stores it in its cache. See also BIND server, forwarder server, primary server, and secondary server.

The main or official name for a host; other names for the same host are aliases. In a BIND configuration, you specify the canonical name in a CNAME record of the named.hosts file.

A BIND configuration logging statement phrase that specifies the different categories for which to log messages. Categories include: config, parser, queries, lame-servers, statistics, panic, update, ncache, xfer-in, xfer-out, db, eventlib, packet, cname, security, os, insist, maintenance, load, response-checks, and default.

A form of network management that manages from a single point in the network.

The data path between two or more stations, including the communications control capability of the associated stations.

A BIND configuration logging statement that specifies output methods, format options, and severity levels associated with a category of messages to be logged.

A computed value based on the contents of a packet. The value is sent with the packet when it is transmitted. The receiving host computes a new value based on the received data. If the originating and receiving values are the same, the receiver has a high degree of confidence that the data was received correctly.

A logical (virtual) link that provides a communications connection between adjacent nodes.

The name of an entity class. For example, node is the global entity class.

A computer system or process that requests a service of another computer service or process.

A model of interaction used in distributed processing products when a client process sends a request and waits for the results from a server process.

The combined hardware interrupt timer and software register that maintain system time. In many systems, the hardware timer sends interrupts to the operating system; at each interrupt, the operating system adds an increment to a software register that contains the time value.

An optional node name and address used by some or all nodes in an OpenVMS Cluster, allowing these nodes to be reachable on the network with the same address.

An environment that allows a system in a cluster to take on the responsibilities of a system that crashed or is otherwise unavailable. For example, you can configure a system to become a DHCP server when the primary DHCP server process crashes or when the system that the primary DHCP server is running on becomes unavailable.

The condition in which two data packets are transmitted over a medium at the same time, making both unintelligible.

The common way of expressing an Internet address. The 32-bit address uses four fields that are separated by periods; each field ranges from 0 to 255.

The physical medium connecting two systems.

A special-purpose standalone system dedicated to managing communications activities for other computer systems.

The process of joining two or more items together, as when input files are appended to a new output file.

The Compaq TCP/IP Services for OpenVMS database with SMTP, SNMP, and TIME specifications.

The condition in which a network or part of a network is overloaded and has insufficient communication resources for the volume of traffic.

A logical communication path between two processes that are using the TCP protocol. The communication path must exist before data can be sent in either direction. A three-way handshake occurs between the requesting and receiving process to establish a port through which the two processes communicate.

The model of interconnection that consists of three phases: establish connection, transfer data, and release connection. TCP is a connection-oriented protocol.

The model of interconnection in which communication takes place without first establishing a connection. UDP, IP, and IPX are connectionless protocols.

The degree to which network nodes are interconnected. Full connectivity means all nodes have links to every other node.

A data file on a Compaq OpenVMS NFS server with a UNIX directory structure and UNIX file attributes for a local, logical UNIX-style file system. Each UNIX regular file is stored as a separate data file. The directory data files in the container file contain the UNIX file names and a pointer to the corresponding OpenVMS Files-11 data file.

A logical UNIX-style file system that resides on a Files-11 formatted disk and is represented as a set of Files-11 files. See also container file.

The condition when two or more stations attempt to use the same channel at the same time.

The scheme of access control used by many networks. Control is distributed among the nodes of the network. Any node wanting to transmit can do so, accessing the network on a first-come, first-served basis. However, it is possible that two nodes are in contention, or start transmitting at the same time, in which case a collision occurs. Each node must then back off and retransmit after waiting a random period of time.

A group of small (256-byte) buffers dynamically allocated from nonpaged pool memory; stores information related to device sockets, internal control structures, IP addresses, Internet routes, and Internet packet headers.

Greenwich Mean Time.

An OSPF (Open Shortest Path First) protocol metric. See metric and OSPF.

The performance and error statistics kept for an entity by network management, such as lines and nodes.

See cyclic redundancy check.

An error detection scheme whereby a number is derived from a set of data before it is transmitted. Once transmitted, the receiving node recalculates the number and compares it to the value originally transmitted. If the numbers are different, some type of transmission error has occurred.

A process that executes in the background waiting for some event to occur.

A group of large (1792-byte) buffers that store data in the system space; transmit and receive operations service user processes by moving data to and from data clusters.

Used for encryption of message text and (with certain choices among a set of alternative algorithms) for computation of message integrity check (MIC) quantities.

A type of encryption scheme approved by the U.S. National Bureau of Standards.

A logical connection between two systems on the same circuit on which data integrity is maintained.

The layer in a network model that handles communication between physical hosts.

See octet.

The data blocks received that arrived too quickly to be processed by the receiver and were, therefore, lost.

A self-contained package of data carrying enough information to be routed from source to destination without reliance on earlier exchanges between source and destination or the transporting network.

The result of fragmenting a datagram. Fragments carry a portion of data from the larger original and a copy of the original datagram header. The header fragmentation fields are adjusted to indicate the fragment's relative position within the original datagram.

The time allowed for reassembly of a fragmented datagram.

The mode of delivery for a datagram which is delivered in such a way that the receiver can determine the boundaries of the datagram as it was entered by the source.

See Distributed Computing Environment.

See DIGITAL Command Language.

The routing process that determines the path, or route, along which a data packet travels to reach its destination; forwards packets on the lowest-cost path even if that one does not have the fewest hops. The path that the data takes through the network is transparent to users.

The process by which the transfer syntax representation of a data value is transformed into the local representation of that value.

A permanent connection between two hosts using an RS232 serial port. SLIP or PPP can be used for TCP/IP communication between the two hosts.

The route used to direct any data addressed to network host addresses for which no explicit route is specified.

A HELLO metric. Valid values are from 0 to 30000, inclusive. The value of 30000 is the maximum metric and means unreachable. See also metric and HELLO.

The access right that grants users the ability to remove data from the domain.

See data encryption key.

See Data Encryption Standard.

In OSPF, a designated router is a multiaccess network that has at least two attached routers. The designated router generates a link state advertisement for the multiaccess network and assists in running the protocol. The designated router is elected by the HELLO protocol.

The IP address that specifies where a datagram is to be sent; contains the network and host identifiers.

Any network or host.

A 2-octet value in the TCP and UDP header field that identifies the destination upper-level protocol for a packet's data.

The software associated with each physical device; serves as the interface between the operating system and the device controller.

The extension of the pseudodevice, used for communications; consists of the Internet pseudodevice and the socket. See also pseudodevice.

See Dynamic Host Configuration Protocol.

The sequence of message exchanges between open systems that represents a single association and the set of underlying connections.

A temporary (as opposed to dedicated) network connection established through a telephone line with a modem.

A host that responds to incoming PPP connection requests. A PPP server.

The command interface of the OpenVMS operating system.

The Compaq software product implemented on OpenVMS as an ancillary control process (ACP) and a network device driver (BG driver) with executive-level components and user applications that use TCP/IP protocols.

An EGP metric. See metric and EGP. Valid values are from 0 to 255 inclusive.

An architecture of standard programming interfaces, conventions, and server functions (for example, naming, distributed file system, remote procedure call) for transparently distributing applications across networks of heterogeneous computers.

A collection of several different data repositories that look like a single database to the user. The Domain Name System (DNS) is a distributed database.

A form of network management in which network managers and management software are dispersed across many systems.

The technology that enables the distribution throughout the network of computing power and storage facilities to user work areas, such as offices, laboratories, or machines on factory floors.

A collection of computer systems, tied together by communications networks for the purpose of sharing resources; end users do not need to be aware of the physical location of the shared resources.

See Domain Name System.

An organizational unit with administrative responsibility for naming networks or hosts. An internet domain name consists of a sequence of names (labels) separated by periods (dots); for example, tundra.mpk.ca.us.

The name used to refer to a fully qualified domain or subdomain. For example, in cat.food.iams.com, food.iams.com, iams.com, and .com are all domain names. Each name specifies a different domain level.

A distributed database system that allows TCP/IP applications to resolve a host name into a correct IP address.

See dotted-decimal notation.

The syntactic representation for a 32-bit integer that consists of four 8-bit numbers written in base 10 with periods (dots) separating them; used to represent IP addresses in the Internet, as in 192.67.67.20. Many Internet application programs accept dotted-decimal notation in place of destination machine names.

Transferring a copy of a system image from a load host to a target. Some systems, such as DEC WANrouter systems and Compaq DECserver terminal servers, automatically request a downline load of their image upon startup and reboot. One of the functions of a TFTP server.

The change in a clock's time rate over a specified period.

A measure, in Hertz per second, of how quickly the skew of a clock is changing. See also skew.

The automatic rerouting of traffic based on a sensing and analysis of current actual network conditions; not including cases of routing decisions taken on predefined information.

A superset of the BOOTP protocol that enables the automatic assignment of IP addresses to clients on networks from a pool of addresses. The IP address assignment and configuration occurs automatically whenever appropriate client systems (workstations and portable computers) attach to a network. The TCP/IP Services for OpenVMS implementation of DHCP is based on the JOIN product by Competitive Automation.

A type of routing where a host or router talks to adjacent routers to learn what networks each router is connected to. Subsequently, the kernel's routing tables are updated when the router learns new information. There are many routing protocols including Interior Gateway Protocols (RIP, OSPF) and Exterior Gateway Protocols (EGP and BGP).

A port number temporarily assigned to a client process for the duration of a session. When the client process terminates, the port number can be assigned to another process. The port number is usually from 1024 to 5000.

See Exterior Gateway Protocol.

The classification in Internet standards for optional protocols.

The service whereby a computer user can exchange messages with other computer users (or groups of users) by means of a communications network; one of the most popular uses of the Internet.

See electronic mail.

A technique used by layered protocols in which a layer adds header information to the protocol data unit (PDU) from the layer below. As an example, in Internet terminology, a packet would contain a header from the physical layer, followed by a header from the Network layer (IP), followed by a header from the Transport layer (TCP), followed by the application protocol data.

A process of encoding information so the meaning of its content is no longer immediately obvious to anyone who obtains a copy of it.

See end system.

A nonrouting system; can receive data packets addressed to it and send data packets to other systems on the same subnet but cannot relay, route, or forward data packets to other systems.

An individual, manageable piece of a network; has attributes that describe it, a name that identifies it, and an interface that supports management operations.

A collection of entities that share the same properties and have the same parent entity; each member of the class has a unique identifier within the class. Entity classes have class names.

An architecturally defined collection of entities. The entities in the group must have a common top entity and must all be of the same class.

A logical hierarchical tree structures of manageable entities in which child entities are below their parent entities. Children can be accessed only through their parents' agent.

An attribute that specifically identifies an entity. See also attribute group.

A label associated with some entities used to identify or locate them for management purposes.

The subgrouping of an entity that determines its relationship to other entities.

A baseband network medium. Commonly used to connect a local area network.

A measurable network-specific or system-specific occurrence for which a logging component maintains a record.

The classification in Internet standards for protocols that are developed as part of an ongoing research project not related to an operational service offering; not intended for operational use.

The Compaq TCP/IP Services for OpenVMS database with directory names that can be mounted from remote NFS clients.

A file in an exported directory or a subdirectory of an exported directory. See also exporting.

A file system that can be accessed by a remote system using the Network File System. The local system imports the remote file system. Both the remote and local system must be configured to grant and receive access to the file system.

Identifying a directory on an NFS server that can be remotely mounted by NFS clients.

A feature of OpenVMS Alpha Version 7.2 that allows the use of Windows-style file specifications. This feature provides greater flexibility for OpenVMS Alpha systems to store, manage and access files that have names similar to those in a Windows 95 or Windows NT environment.

Multiple LANs connected with data link relays or bridges.

The protocol that distributes routing information to the gateways that interconnect networks.

A class of routing protocols used to exchange routing information within an autonomous system.

One of a class of exterior gateway protocols.

See Fiber Distributed Data Interface.

The operation of two commands that allow a system manager to fetch a value from a data item or to store a value into a data item.

The high-speed (100 mb/s) networking standard based on fiber optics, established by the American National Standards Institute (ANSI); uses 1300 nanometer light wavelength. FDDI networks are limited to approximately 200 km in length, with repeaters every 2 km or less.

A uniquely named collection of information with shared managerial and structural properties.

The characteristic of a file, such as its size or creation date. The values of some file attributes may change during the lifetime of a file.

The information that is stored within a file and comprises its contents (as opposed to its attributes).

System-specific information that identifies a file on its storage system.

The host whose principal purpose is to store files and provide network access to them.

System-specific information that identifies a file on its storage system.

A method for recording, cataloging, and accessing files on a volume.

The protocol and software that permit a user on one host to access and transfer files to and from another host over a network. See also Trivial File Transfer Protocol.

The set of rules that govern the organization of the OpenVMS file system, external to the files themselves.

The utility that provides information about users on local and remote systems.

(1) The function of a receiving entity to limit the amount or rate of data that is sent by a transmitting entity. (2) The control of the rate at which hosts or gateways inject packets into a network or Internet, usually to avoid congestion. Flow control mechanisms can be implemented at various levels and allow communicating layers to match their data transfer and receive rates. Simplistic schemes, like ICMP source quench, simply ask the sender to cease transmission until congestion ends. More complex schemes vary the transmission rate continuously.

The name server that processes recursive requests that a slave server cannot resolve locally; has access to the Internet. See also BIND server, cache server, primary server, secondary server, and slave server.

The table that GATED uses internally to store routing information it learns from routing protocols is a routing table; also known as a routing information base, or RIB. The routing table is used to collect and store routes from various protocols.

The table in the kernel that controls the forwarding of packets is a forwarding table, also known as a forwarding information base, or FIB.

See fully qualified domain name.

A piece of a packet that results from a router dividing an IP datagram into smaller pieces for transmission across a network that cannot handle the original datagram size. Fragments use the same format as datagrams; fields in the IP header declare whether a datagram is a fragment and, if so, where the data in the fragment occurred in the original datagram. IP software at the receiving end must reassemble the fragments. See also maximum transmission unit.

The IP process of breaking up packets into smaller packets for transmission; allows a packet originating in a network that allows a large packet size to traverse a network that limits packets to a smaller size. The destination host reassembles the fragments. See also maximum transmission unit.

A Data Link layer packet that contains the header and trailer information required by the physical medium.

See File Transfer Protocol.

A circuit designed for transmission in both directions at the same time. Contrast with half-duplex circuit.

Data transmission in both directions at the same time. Contrast with half-duplex transmission.

The full site name of a system, such as scryber.enet.dec.com rather than just the host name of scryber.

A parameter in a $QIO system service call that defines the specific function of that $QIO.

A routing daemon that can be configured to route one or more of the following protocols: RIP, BGP, EGP, and OSPF.

A communications device or program that passes data between networks having similar functions but dissimilar implementations. The term router is now used in place of the original definition of gateway.

An intermediate destination by which packets are delivered to their ultimate destination.

A host address of another router that is directly reachable through an attached network. As with any host address it may be specified symbolically.

Another term for an access system.

See GATED.

See group identification.

One billion bits.

One billion bytes.

The identification code for a group of UNIX users.

A circuit designed for transmission in either direction, but only one direction at one time. Contrast with full-duplex circuit.

Data transmission in either direction, but only one direction at a time. Contrast with full-duplex transmission.

The exchange of connection information between two communicating entities; takes place to enable the successful completion of a connection. Used, for example, in establishing a TCP connection between client and server applications.

The address that identifies the connection device between the network controller of a host and the network cable. See also address.

A mechanism that allows you to assign more than one name to a file. Both the new name and the file being linked must be in the same file system. See also link.

The portion of a packet that precedes the actual data and contains control information such as source and destination address and error checking.

A technique used by PPP and SLIP protocols to reduce the number of bytes per frame when sending packets over a slow serial link. The use of header compression is negotiated between the client and servers processes to reduce the size of the IP and TCP headers.

A network consisting of different network protocols or different operating system software, such as OpenVMS and UNIX.

Routing based on domains. Interdomain routers are responsible only for getting data to the right domain and intradomain routers take responsibility for routing within the domain.

The number of connections between two hosts, based on the number of different routers needed to traverse the distance between the two hosts.

A term used in routing. Number of hosts separating a source and final destination (including the final destination) on a network.

A computer system that acts as a source or destination of network messages sometimes called node.

The IP address of any system. Usually specified in dotted-decimal notation. There are four values in the range from 0 to 255 inclusive, separated by dots (.). For example, 132.236.199.63 or 10.0.0.51. It can also be specified as an 8-digit hexadecimal string preceded by 0x. For example, 0x0a000043. In addition, if the options noresolv statement is not specified, this can be a symbolic host name. For example, gated.cornell.edu or nic.ddn.mil. The numeric forms are preferred over the symbolic form.

See host number.

The Compaq TCP/IP Services for OpenVMS database that is created by default; allows users to use host names; contains host names, IP addresses of the hosts, and any alias names for the hosts.

The name given to a network host. See also fully qualified domain name and alias.

The part of an IP address that identifies which host on the network is being addressed.

Also called Transport layer. The second-highest level in the Internet architecture model; provides end-to-end communication services, including mechanisms such as end-to-end reliability and network control. Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) reside in this layer.

See Internet Architecture Board.

The TELNET options that allow TELNET users to connect to hosts that support 3270 terminals.

See Internet Control Message Protocol.

Internet Engineering Task Force. A large international community of network designers, operators, vendors and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. Membership is open to everyone. See the http://www.ietf.org web site for more information.

See Interior Gateway Protocol.

The Internet Message Access Protocol. IMAP enables clients to access email messages and folders from an IMAP server and synchronize them locally. This enables a client to organize email messages and folders without continuous access to the server.

A UNIX internet daemon. A server process listens for client requests for specific services. When inetd receives a request for a service, it starts the appropriate server process.

The first sequence number used for sending or receiving on a connection.

A UNIX file structure used to address a file block. There is a unique inode allocated for each active file with a name made up of a device/i-number pair.

The boundary between two parts of a system across which communication can occur; may be defined through hardware or software.

The host address of an attached network interface. This is the address of a broadcast, nbma, or loopback interface, and the remote address of a point-to-point interface. As with any host address, it can be specified symbolically.

The connection between a router and one of its attached networks. A physical interface can be specified by a single IP address, domain name, or interface name (unless the network is an unnumbered point-to-point network). Multiple levels of reference in the configuration language allow the identification of interfaces by using wildcard, interface type name, or delete word address. Be careful using interface names because future versions might allow more than one address per interface. Dynamic interfaces can be added or deleted and indicated as up or down as well as changes to address, netmask, and metric parameters.

The protocol used to propagate network reachability and routing information within an autonomous system; RIP is among the most popular.

One of a class of routing protocols used to exchange routing information within an autonomous system.

A list of one or more interface names, including wildcard names (names without a number) and names that may specify more than one interface or address, or the token all-for-all interfaces.

An OSI system that performs Internet layer forwarding. A routing system receives data packets from a system on one subnet and passes them on to a system on another subnet; it receives data packets from a source end system, or from the previous intermediate system on the route, and passes them on to the destination end system, or to the next intermediate system on the route.

A shortened form of internetwork; a network of networks; interconnected TCP/IP networks that function as one large virtual network. Differs from the Internet by their lack of connectivity with the global Internet.

The worldwide network of networks and gateways that use the TCP/IP protocol suite and function as one virtual network; provides universal connectivity and three levels of network services: unreliable, connectionless packet delivery; reliable, full-duplex stream delivery; and application level services such as electronic mail that build on the first two. The Internet connects many universities, government research labs, military installations, and private businesses.

A four-layered communications model that consists of the following: Application layer, Transport layer, Internet layer, and Network Interface layer.

The technical body that oversees the development of the Internet suite of protocols (TCP/IP). It has a research task force and an engineering task force, each responsible for investigating a particular area.

A system that consists of a set of gateways, each of which can reach any other gateway in the same system using paths by means of gateways only in that system. The gateways of a system cooperatively maintain a routing database using an interior gateway protocol.

An extension to the Internet Protocol; used by gateways to communicate with the network software in hosts.

An IP header field that indicates the number of 32-bit words making up the Internet header.

The layer in the TCP/IP network model where data is transferred between hosts across networks. Also referred to as Network Interface layer.

See IP address.

A connectionless, best-effort, packet-switching protocol that resides in the Internet layer and has two major functions: internet addressing and fragmentation of messages.

A collection of many different computing systems which communicate with each other. The computing systems can include different hardware architectures, operating systems, and network technologies.

The ability of software and hardware on multiple machines from multiple vendors to communicate meaningfully.

The Internet Network Information Center; organization that provides the Internet community with registration, directory, database, and information services.

A data structure associated with the $QIO system service. The IOSB holds information about how the I/O request completes.

See Internet Protocol.

An address that identifies the connection between the network controller of a node using TCP/IP and the network cable. The 32-bit address is composed of two parts: network number and host number.

The basic unit of information passed across the Internet; contains source and destination addresses, the data, and fields that define the length of the datagram, the header checksum, and flags indicating whether the datagram can be (or has been) fragmented. An IP datagram is to the Internet what a hardware packet is to a physical network. See also datagram.

A configurable kernel option that controls whether a host forwards IP datagrams. Generally, hosts do not forward IP datagrams.

A protocol in which the protocol header follows the data.

A popular implementation of TCP/IP and associated protocols for amateur radio systems.

See kilobits per second.

The software that provides the standard API for application programs. Generally speaking, the kernel embodies the policy and structure of an operating system. In a narrower sense, the kernel provides a programmatic interface to any hardware resources available. In a UNIX system, the kernel is a program that contains the device drivers, the memory management routines, the scheduler, and system calls; always running while the system is operating.

The measure of data transmission rate.

See local area network.

(1) The grouping of related communication functions that provide a well-defined service to a client independently of the protocols and other means used to provide it. (2) A software protocol levels that make up network architectures; each layer performs certain functions for the layers above and below it.

A classification in Internet standards for protocols that are intended for use in limited circumstances; possibly because of their experimental state, specialized nature, limited functionality, or historic state.

The Compaq TCP/IP Services for OpenVMS remote printing services for UNIX and OpenVMS client hosts.

The maximum rate at which data can be reliably transmitted over a line; varies with the capability of the modem or hardware device that performs the transmitting.

A directory entry referring to a file; one file can have several links to it.

The format for storage or transmission of binary data in which the least significant byte comes first. The reverse convention is called big endian.

A TCP/IP Services component that provides configurable, calculated methods for distributing BIND services among systems in a cluster.

The address of a host within a subnet.

The host address of an attached interface. This is the address of a broadcast or loopback interface, and the local address of a point-to-point interface. As with any host address, it can be specified symbolically.

A self-contained group of computers and communications devices (such as modems, routers, servers, and repeaters) that offers a high-speed, reliable communications channel. LANs span a limited distance such as a building or group of buildings, but can be connected to wide area networks (WANs) with gateways. Contrast with wide area network (WAN).

Any data stored locally by a system.

A network directly attached to a host or gateway.

A node at which the user is located.

A subnet directly attached to a host or gateway.

An NFS component that allows an NFS client to lock portions of files that reside on an NFS server.

The ability of nodes to communicate.

A temporary connection between processes on source and destination nodes (or between two processes on the same node).

The upper portion of the Data Link layer that presents a uniform interface to the user of the data link service, usually the Internet layer.

A local node that is associated with a particular address and is treated as if it were a remote node. All traffic to the loop node is sent over the associated address; used for loopback testing.

A program that sends packets to a remote host on the Internet and looks for replies; works by means of the echoing facility provided by the ICMP protocol and is a way to determine if an Internet host is reachable from your host. See also packet internet groper.

See remote line printing or line printer daemon.

A mail gateway that forwards electronic mail between two or more networks while ensuring that the messages it forwards meet certain administrative criteria; specialized form of mail gateway that enforces an administrative policy with regard to what mail it forwards.

The Domain Name System resource record type indicating which host can handle mail for a particular domain or host.

The Compaq TCP/IP Services for OpenVMS implementation of a mail exchanger that allows hosts in a local network to forward mail to systems that might not be directly connected to the local network.

The part of an electronic mail delivery system that allows a message to be delivered to a list of addressees. Users send messages to one address (e.g., hacks@somehost.edu) and the mail exploder handles delivery to the individual mailboxes.

A host that connects two or more electronic mail systems (especially dissimilar mail systems on two different networks) and transfers messages between them.

A series of hosts used to direct electronic mail from one user to another.

A database used by the Simple Network Management Protocol (SNMP) to check network statistics and configurations. An SNMP management station can query a MIB or set it in an SNMP agent (for example, router). Standard, minimal MIBs have been defined (MIB I, MIB II), and vendors often have custom entries. In theory, any SNMP manager can talk to any SNMP agent with a properly defined MIB.

Data that can be accessed by a network management protocol; for, the database maintained by a gateway running SNMP.

The workstation of a network manager running SNMP.

A means of subdividing networks using address modification. A mask is a dotted quad specifying the bits of the destination that are significant. Except when used in a route filter, GATED supports only contiguous masks.

The number of significant bits in the mask.

The root of an OpenVMS file system on a particular physical device.

The name server that is the authority for a specific domain space. See also BIND server.

The largest possible unit of data that can be sent on a given physical medium. See also fragmentation.

See memory buffers.

The portions of memory that act as queues for data arriving at a port before the process is ready to claim that data.

A message block or a series of message blocks that constitute a logical grouping of information; each is delimited by communications control characters.

One of the units used to help a system determine the best route. Metrics may be based on hop count, routing delay, or an arbitrary value set by the administrator depending on the type of routing protocol. Routing metrics may influence the value of assigned internal preferences. See also preference.

See master file directory.

See Management Information Base.

See Management Information Base II.

Multipurpose Internet Mail Extensions; a specification for the transfer of nontext files with regular Internet e-mail.

A protection placed on a file.

A device that translates digital signals (electrical impulses) generated by a computer into analog signals (tones) that can be transmitted over telephone lines, and vice versa.

An NFS process that makes a remote directory available to local users.

A directory on an NFS client that is associated with a remote file system. The directory must exist before NFS can use it as a mount point.

See maximum transmission unit.

Physical networks that support the attachment of multiple (more than two) routers. Each pair of routers on such a network is assumed to be able to communicate directly.

A transmission of network traffic intended for multiple hosts (but not all connected hosts) within a network or internet.

An address that designates a subset of nodes that are all listening for packets destined to this address.

An addressing mode in which a data packet is targeted to a group of nodes that are of the same type, for example, all level 1 routers or all level 2 routers.

A host that has two or more hardware connections to a network; requires multiple IP addresses.

Using a single connection to carry several data streams and the mechanism for assigning these streams to that connection.

A circuit that connects multiple systems.

A network consisting of multiple processors.