Glossary
F
86 terms.
- Facsimile
A technology for transmitting documents over telephone lines, reproducing them on paper at the receiving end. G3-facsimile is a standardized group of devices defined for use on standard telephone networks.
Plain language A technology for transmitting paper documents over phone lines and reproducing them remotely.
Used in RFC 804 RFC 809 RFC 1528 RFC 1530 RFC 2306 RFC 2879 RFC 3949 RFC 3965 RFC 4734
- Failover
Switching to a backup server or connection when the primary one stops responding, so service continues.
Plain language Switching to a backup server or connection when the primary one fails.
Used in RFC 3539 RFC 3991 RFC 4233 RFC 5351 RFC 6027 RFC 6414 RFC 6733 RFC 7031
- False accept
A comparison result that wrongly treats two different strings as the same. In authentication it can let someone in under another person's name.
- Fast handover
A set of mobility extensions that reduce the delay when a mobile node moves between access routers. The previous router passes context to the new router ahead of or just after the move.
Plain language Mobility extensions that reduce delay when a mobile device moves between access routers.
- Fast Recovery
The part of TCP congestion control that reduces the congestion window after packet loss is detected, using feedback from returning acknowledgments to decide when to send more data.
Plain language TCP congestion control that reduces the window after packet loss and resumes sending based on acknowledgments.
- Fast Reroute
Precomputing a backup path so traffic can switch to it immediately when a link or node fails, instead of waiting for the network to recompute routes.
Plain language Precomputed backup paths that traffic switches to immediately when a link fails.
Used in RFC 5714 RFC 5824 RFC 6414 RFC 6894 RFC 7325 RFC 7431 RFC 7473 RFC 7490 RFC 7812 RFC 7855 RFC 8271 RFC 8320 RFC 8333 RFC 8355 RFC 8424 RFC 8537 RFC 9087 RFC 9855
- Fast Retransmit
A TCP algorithm that resends a segment after three duplicate ACKs arrive, instead of waiting for the retransmission timeout to expire.
Plain language TCP mechanism resending a segment after three duplicate acknowledgments instead of waiting for timeout.
Used in RFC 2416 RFC 2581 RFC 2757 RFC 2883 RFC 3042 RFC 3155 RFC 3708 RFC 5681 RFC 5827
- Fat Tree
A folded spine-and-leaf network topology, also called a Clos, that may have several Points of Delivery and one or more Top of Fabric planes. RIFT is designed for such networks.
Plain language A folded spine-and-leaf network topology with multiple points of delivery.
- Fate sharing
Keeping the state of a conversation only in the endpoints, so it can be lost only if an endpoint itself fails. RFC 1958 uses this to explain why datagrams are better than classical virtual circuits.
Plain language Keeping conversation state only in endpoints so it is lost only if an endpoint fails.
Used in RFC 1144 RFC 1958 RFC 2775 RFC 3234 RFC 3439 RFC 3724 RFC 5505 RFC 5534 RFC 5659 RFC 5860 RFC 5880 RFC 5882 RFC 5921 RFC 6182 RFC 6371 RFC 6372 RFC 6897 RFC 7211 RFC 7276 RFC 7926 RFC 8800 RFC 9455 RFC 9516 RFC 10014
- FDDI (Fiber Distributed Data Interface)
A high-speed local area network standard using fiber-optic cables in a token-passing ring topology, providing speeds of 100 Mbps.
Plain language Fiber Distributed Data Interface, a high-speed local-area network using fiber-optic cables in a ring topology.
Used in RFC 1103 RFC 1188 RFC 1285 RFC 1329 RFC 1390 RFC 1512 RFC 2019 RFC 2467 RFC 2816
- Feasibility condition
A test a router applies to a received route update. The update is accepted only if it can be shown that accepting it cannot cause a routing loop.
Plain language A test validating that accepting a route update will not cause a routing loop.
- Feature Interaction
Unexpected or ambiguous behavior that arises when two or more telephone features are combined, such as 'call forwarding on busy' combined with 'call waiting.'
Plain language Unexpected behavior when two or more telephone features are combined together.
- Feature tag
A name that identifies one feature of a device or resource, such as the SIP methods it supports. In SIP, feature tags are carried as Contact header field parameters.
Plain language A name identifying one capability of a device or resource, such as supported SIP methods.
Used in RFC 3840 RFC 3841 RFC 4508 RFC 4596 RFC 5359 RFC 7826
- Federated authentication
An arrangement in which several servers accept the same credential, so a client does not need a separate login for each one. Examples named include OAuth, OpenID, SAML and CA-based certificates.
Plain language An arrangement where servers accept the same credential from multiple identity providers.
- Federation
A group of independent organizations that have agreed to trust each other's identity information using a common standard like SAML.
Plain language A group of independent organizations trusting each other's identity using a common standard.
- Feedback implosion
The flood of replies that can overwhelm a sender and the network when a large group of receivers all send feedback at the same time.
Plain language A flood of simultaneous replies that overwhelms a sender and network.
- Feedback loop
An arrangement in which a mailbox provider sends reports about mail to a sender or other party who has asked for them. Such arrangements are usually set up by private agreement.
- Feedback suppression
A way to keep many receivers from all answering at once. Each waits a random time and stays silent if it hears that someone else already sent the same request.
Plain language Technique preventing multiple receivers from sending identical responses simultaneously.
- Feistel cipher
A cipher built from repeated rounds in which half of the data is combined with the output of a round function applied to the other half. ARIA uses a 3-round Feistel cipher inside its key schedule.
Plain language A cipher design using repeated rounds where half the data is combined with a function of the other half.
- Feistel network
A cipher design that splits a block into two halves and repeats rounds in which one half is XORed with a function of the other half and a subkey. The same structure can be run backwards to decrypt.
Plain language A cipher architecture where one half is XORed with a function of the other half in each round.
- Fencing
The process by which a metadata server stops storage devices from processing I/O from a specific client to a specific file. It is used when a layout is revoked.
Plain language Preventing a specific client from accessing a particular file by stopping the storage device.
- Fibre Channel
A family of protocols used for high-speed storage networking, typically in Storage Area Networks (SANs).
Plain language A family of high-speed protocols for storage networking, typically in Storage Area Networks.
Used in RFC 2625 RFC 3821 RFC 3822 RFC 3831 RFC 4044 RFC 4171 RFC 4172 RFC 4338 RFC 4369 RFC 4439 RFC 4595 RFC 4625 RFC 4626 RFC 5324 RFC 6847
- File handle
An opaque value chosen by an NFS server to identify a file or directory. In NFSv4.0 it can be at most 128 bytes long.
Plain language An opaque identifier assigned by an NFS server to identify a file or directory.
- Filehandle
An opaque, server-assigned identifier for a file or directory. Clients store and send it back but must not interpret its contents.
Plain language A server-assigned identifier for a file that clients use but must not interpret.
Used in RFC 2055 RFC 2224 RFC 3010 RFC 3530 RFC 7530 RFC 7863 RFC 8881
- Fileset
A set of files together with the directory tree that contains them. It is the basic unit of data management in a federated file system.
Plain language A collection of files with their directory tree, treated as one unit in a federated file system.
- Filtering Database
A table maintained by a bridge that maps learned MAC addresses to the ports on which they were seen, used to decide which port to forward each incoming frame to.
Plain language A bridge's table mapping learned MAC addresses to ports for forwarding decisions.
- Fine-grained label
A 24-bit data label for TRILL Data packets, made of a 12-bit high part and a 12-bit low part. It allows far more isolated groups of traffic than the 4K VLAN IDs of the base protocol.
- Fingerprint
A short value computed by hashing a piece of data, used to identify that data without sending all of it. If the data changes, the fingerprint changes too.
Plain language A short value computed by hashing data, changing if the data is modified.
Used in RFC 4819 RFC 6091 RFC 6594 RFC 6973 RFC 7924 RFC 8827
- Finite field
A mathematical structure used in network coding where addition and multiplication are defined with a limited set of elements, enabling efficient computation on computers.
Plain language A mathematical set with limited elements where addition and multiplication wrap around.
- Finite State Entropy
An entropy codec based on Asymmetric Numeral Systems that uses a state value to track position in a probability distribution table, enabling efficient compression of symbols with non-uniform frequencies.
Plain language An entropy codec using state values to track position in probability distribution tables.
- Finite-state machine
A model with a fixed set of states, where events such as receiving a packet or a timeout cause actions and a move to a new state. PPP uses one to negotiate options.
Plain language A model with fixed states where events trigger actions and transitions.
Used in RFC 689 RFC 904 RFC 908 RFC 916 RFC 934 RFC 963 RFC 964 RFC 998 RFC 1267 RFC 1307 RFC 1331 RFC 1434 RFC 1541 RFC 1548 RFC 1661 RFC 1771 RFC 1934 RFC 1987 RFC 2281 RFC 2360 RFC 2490 RFC 2814 RFC 2909 RFC 3083 and 50 more
- Firewall
A gate between two networks that limits which machines on one side may contact machines on the other.
Plain language A security gate between networks controlling which machines may communicate across it.
Used in RFC 1281 RFC 1636 RFC 1678 RFC 1775 RFC 1825 RFC 1928 RFC 2196 RFC 2316 RFC 2356 RFC 2647 RFC 2678 RFC 2979 RFC 3303 RFC 3514 RFC 3620 RFC 3997 RFC 4540 RFC 4732 RFC 5596 RFC 5902 RFC 5973 RFC 6392 RFC 6887 RFC 7045 and 5 more
- First Come First Served
An IANA allocation procedure where values are assigned to requesters in the order the requests are received, without review, as long as they meet basic requirements.
Plain language An IANA allocation procedure assigning values in request order without review.
- First Well Known Rule
The rule that the application defines, rather than the database, to produce the first valid key from the application unique string.
Plain language The rule that gives the first key, defined by the application itself.
- Five-tuple
The five values that identify one transport-protocol instance: protocol, source address, source port, destination address and destination port.
Plain language Five values identifying a transport connection: protocol, source/destination addresses and ports.
Used in RFC 2693 RFC 5766 RFC 6056 RFC 7675 RFC 8016 RFC 8290 RFC 8859
- Flag Day
A scheduled or unscheduled event in which a system or network is changed suddenly, typically requiring a service outage or planned downtime.
Plain language A scheduled event when a system changes suddenly, often requiring service outage.
- Flash crowd
A sudden, large spike in demand for content, such as when a major live event begins and many users attempt to stream it simultaneously, overwhelming normal capacity.
- Flash renumbering
An event where a prefix in use on a network suddenly becomes invalid and is replaced by a new prefix, without the planned phase-out of the old one.
Plain language Sudden replacement of a network prefix without planned transition.
- Flexible Algorithm
A way for a link-state protocol to compute paths for a custom topology, chosen by rules such as link colors, alongside the default computation. It is described in RFC 9350.
Plain language A link-state routing computation using custom topology rules alongside default routing.
Used in RFC 9352 RFC 9502 RFC 9843 RFC 9917 RFC 9933 RFC 10041
- FlightSize
The amount of data that a TCP sender has sent but that has not yet been cumulatively acknowledged, in other words the volume of data in flight on the network. RFC 6675 defines it as an instantaneous measure.
Plain language The amount of sent data that has not been acknowledged yet.
- Floating time
A DATE-TIME with no Z suffix and no TZID, which means the same wall-clock time in whatever zone the viewer is in.
Plain language A DATE-TIME without timezone, representing the same wall-clock time in any zone.
- Flooding
The network behavior of sending a packet to all switches in a VLAN when the destination MAC address is unknown or the destination is a broadcast address.
Plain language Sending a packet to all switches in a VLAN when the destination address is unknown.
Used in RFC 1142 RFC 1459 RFC 1765 RFC 2178 RFC 2334 RFC 2642 RFC 2973 RFC 5148 RFC 7067 RFC 7357 RFC 8171
- Flooding scope
The set of routers or circuits that a link state PDU is flooded to. IS-IS originally had area (Level 1) and Level 2 subdomain scopes.
Plain language The set of routers or circuits receiving a link state update in IS-IS.
- Floor chair
The moderator of a conference, who can send decisions about floor requests to the floor control server. A chair is also a floor participant and is identified by its own user identifier.
Plain language The moderator who decides who gets to speak.
- Floor control
A mechanism that gives applications or users safe, mutually exclusive or shared access to a resource in a conference. A floor is the temporary permission to use that resource.
Plain language A mechanism controlling exclusive or shared access to resources in a conference.
Used in RFC 4376 RFC 4582 RFC 5018 RFC 5239 RFC 6501 RFC 8855
- Flow
A sequence of packets with a common source, destination, and purpose, such as all packets in a TCP connection or UDP stream.
Plain language A sequence of packets with common source, destination and purpose.
Used in RFC 1241 RFC 1272 RFC 2123 RFC 2386 RFC 2430 RFC 2723 RFC 2992 RFC 5471 RFC 5473 RFC 5795 RFC 6089 RFC 7011 RFC 7297 RFC 7424 RFC 7425 RFC 9341 RFC 9342 RFC 9634
- Flow aggregation
Combining many flow records into fewer records that share common properties such as a time interval or a reduced Flow Key. It is used for data reduction and analysis.
- Flow binding
A Mobile IPv6 binding that directs the traffic of a particular flow to one of the mobile node's addresses rather than to its home address. The flow is described by a traffic selector, which lists the header values that traffic must have to match.
Plain language A rule that sends one kind of traffic to one of a device's addresses instead of to its home address.
- Flow cache
A stateful data structure in intermediate devices that remembers the classification (encrypted vs. ESP-NULL) of each IPsec security association, so heuristics need only run once per flow.
Plain language A stateful structure in network devices caching IPsec security association classifications.
- Flow control
A way for a receiver to limit how much data a sender may send before it must wait. HTTP/2 uses credit-based windows, per stream and for the whole connection, topped up with WINDOW_UPDATE frames.
Plain language A receiver mechanism limiting sender throughput to prevent buffer overflow.
Used in RFC 33 RFC 36 RFC 47 RFC 54 RFC 55 RFC 59 RFC 62 RFC 68 RFC 71 RFC 102 RFC 107 RFC 132 RFC 210 RFC 442 RFC 449 RFC 467 RFC 492 RFC 626 RFC 632 RFC 635 RFC 647 RFC 675 RFC 714 RFC 793 and 69 more
- Flow Identifier
A field in the packet header that identifies which flow the packet belongs to, allowing routers to associate the packet with pre-installed state about its service requirements and routing.
Plain language A packet header field identifying which flow the packet belongs to for routing.
- Flow Key
The set of packet fields used to decide which flow a packet belongs to. Packets that share the same key values are counted as one flow.
Plain language The set of packet fields determining which flow a packet belongs to.
- Flow label
A 20-bit IPv6 header field that a source can set to mark packets of one flow so routers can handle them together. Zero means no flow.
Plain language A 20-bit IPv6 field marking packets of one flow for router handling.
Used in RFC 1752 RFC 1809 RFC 1883 RFC 1953 RFC 2170 RFC 2460 RFC 2491 RFC 3595 RFC 3697 RFC 4149 RFC 4413 RFC 5548 RFC 5673 RFC 5979 RFC 5982 RFC 6088 RFC 6282 RFC 6294 RFC 6391 RFC 6436 RFC 6437 RFC 6438 RFC 6674 RFC 6936 and 17 more
- Flow Record
A record in IPFIX that holds measured values about a single traffic flow, such as its packet count, as exported by a device.
Plain language An IPFIX record holding measured values about a single traffic flow.
Used in RFC 3954 RFC 3955 RFC 4948 RFC 5101 RFC 5472 RFC 5473 RFC 5475 RFC 5476 RFC 6183 RFC 6313 RFC 7011 RFC 9951
- Flow Specification
A BGP-distributed rule that describes a traffic flow, such as by protocol or port, so that BGP speakers can filter it. It is defined in RFC 8955.
Plain language A BGP-distributed rule describing traffic flows for filtering or special handling.
Used in RFC 1363 RFC 1819 RFC 6003 RFC 8955 RFC 9117 RFC 9168
- Flowspec
The part of an RSVP reservation request that describes the quality of service wanted. It is used to configure the packet scheduler and is opaque to RSVP itself.
Plain language The RSVP reservation request part describing desired quality of service.
- Focus
The SIP user agent identified by a conference URI that makes sure all users in the conference can communicate with each other. It also knows the conference state and serves it to subscribers.
Plain language The SIP endpoint ensuring all users in a conference can communicate.
Used in RFC 3911 RFC 4508 RFC 4575 RFC 4579 RFC 5366 RFC 5589
- Footprint
In CDNI, a description of the clients or locations a downstream CDN can serve. It is expressed as footprint objects that each carry a type and a value.
Plain language In CDNI, a description of clients or locations a downstream CDN can serve.
- ForCES
Forwarding and Control Element Separation, an IETF approach in which the control elements of a network device configure and manage separate forwarding elements using a standard protocol.
Plain language Forwarding and Control Element Separation, where control and data planes use a standard protocol.
- Foreign agent
A router on the network a mobile node is visiting that offers it a care-of address and helps deliver tunneled packets to it.
Plain language A router on a visited network offering care-of address and helping deliver tunneled packets.
Used in RFC 1688 RFC 2002 RFC 2006 RFC 2290 RFC 2356 RFC 2794 RFC 3024 RFC 3115 RFC 3344 RFC 3519 RFC 3543 RFC 3957 RFC 4004 RFC 4093 RFC 4636 RFC 4721 RFC 4857 RFC 5177 RFC 5944 RFC 6098 RFC 6245
- Forking
What a SIP proxy does when it forwards one incoming request to several remote destinations at the same time.
Plain language A SIP proxy forwarding one request to multiple destinations simultaneously.
- Format Prefix
The leading bits of an IPv6 address that indicate the type of address and its allocation purpose, used for routing and address classification.
- Forward error correction
Adding repair data to a stream so that a receiver can rebuild lost packets without asking the sender to resend them.
Plain language Adding repair data to a stream for receivers to rebuild lost packets without retransmission.
Used in RFC 2354 RFC 2488 RFC 2728 RFC 2733 RFC 2736 RFC 2887 RFC 3048 RFC 3208 RFC 3451 RFC 3452 RFC 3453 RFC 3591 RFC 3819 RFC 4348 RFC 4352 RFC 4837 RFC 4867 RFC 5052 RFC 5053 RFC 5109 RFC 5170 RFC 5401 RFC 5445 RFC 5510 and 24 more
- Forwarder
A name server that other resolvers use to look up names for them, often because it has better access to the Internet or a larger shared cache.
Plain language A name server that resolves queries for other resolvers, often with larger cache access.
Used in RFC 799 RFC 823 RFC 1668 RFC 2117 RFC 2308 RFC 2845 RFC 3654 RFC 5625 RFC 6074 RFC 7121 RFC 7871 RFC 7945 RFC 8945 RFC 9269 RFC 9273 RFC 9462 RFC 9466 RFC 9499 RFC 9507 RFC 9508 RFC 9531 RFC 9631
- Forwarding adjacency
A label switched path that is advertised in the routing protocol as if it were a link, so that other paths can be routed over it.
Plain language A label switched path advertised as a link for other paths to use.
Used in RFC 3477 RFC 3480 RFC 3945 RFC 4206 RFC 6001 RFC 6107
- Forwarding Element (FE)
A component in a ForCES network element responsible for data-plane functions such as packet forwarding and queuing.
Plain language The component in ForCES responsible for packet forwarding and queuing.
Used in RFC 3746 RFC 5810 RFC 5812 RFC 6041 RFC 6369 RFC 6956 RFC 7121 RFC 7729 RFC 8013
- Forwarding Equivalence Class
A group of packets that are forwarded the same way, such as all packets headed to one address prefix. In LDP a label is bound to a FEC.
Plain language Forwarding Equivalence Class, a group of packets forwarded the same way and sharing one label.
Used in RFC 3036 RFC 4756 RFC 5445 RFC 5775 RFC 5919 RFC 6424 RFC 6681 RFC 6829 RFC 7473 RFC 7552
- Forwarding Equivalence Class
A group of packets that are forwarded the same way and so share one label. Label switching binds labels to these classes.
Plain language A group of packets forwarded identically and sharing one label.
Used in RFC 3031 RFC 3034 RFC 3035 RFC 3036 RFC 3037 RFC 3063 RFC 3215 RFC 3478 RFC 3988 RFC 4182 RFC 4378 RFC 4379 RFC 4447 RFC 5036 RFC 5283 RFC 5331 RFC 5695 RFC 5884 RFC 5918 RFC 5919 RFC 6178 RFC 6388 RFC 6424 RFC 6425 and 18 more
- Forwarding Information Base
A table on a router that maps destination addresses to outgoing interfaces and next hops, used to forward packets.
Plain language Forwarding Information Base, a router's table mapping destination addresses to outgoing interfaces.
Used in RFC 2105 RFC 4098 RFC 6976 RFC 7920 RFC 7938 RFC 8541
- Forwarding Information Base
The table a forwarder uses to decide where to send a request. In CCNx it maps name prefixes to next hops, local applications or caches.
Plain language A forwarder's table mapping name prefixes to next hops.
Used in RFC 1812 RFC 3222 RFC 4098 RFC 5715 RFC 6412 RFC 7922 RFC 8569 RFC 9344 RFC 9531
- Forwarding plane
The part of a network device that handles the data path, doing per-packet processing and forwarding. It is often built from ASICs or network processors.
Plain language The part of a device handling per-packet processing and forwarding.
- Fountain code
An error-correcting code where the sender can generate as many encoded symbols as needed from the source data. A receiver can rebuild the data from any sufficiently large set of them.
Plain language An error-correcting code where the sender generates many symbols for receivers to rebuild data.
- Four-tuple
The four values that identify a TCP connection: the local and remote IP addresses and the local and remote port numbers.
Plain language Four values identifying a TCP connection: local/remote addresses and port numbers.
- Fragment identifier
The part of a URI after a hash sign that names a piece of, or a point within, an object. Its meaning is defined by the application or content type, not by the URI syntax.
Plain language The part of a URI after # that names a piece or point within an object.
Used in RFC 1630 RFC 1808 RFC 2396 RFC 7111 RFC 8118 RFC 8820
- Fragment offset
The IPv4 header field, 13 bits wide, that says where a fragment's data belongs in the original datagram, counted in units of 8 octets.
Plain language An IPv4 header field indicating where a fragment's data belongs in the original datagram.
Used in RFC 791 RFC 1858 RFC 2435 RFC 3128 RFC 3514 RFC 4036 RFC 5371 RFC 5722 RFC 6864 RFC 6946 RFC 7112 RFC 7113 RFC 7610 RFC 7739
- Frame
The unit WebSocket sends on the wire: a short header (flags, opcode, length, optional masking key) followed by payload data. A message may be split across several frames.
Plain language A WebSocket unit with header and payload, where messages may span multiple frames.
Used in RFC 935 RFC 1134 RFC 1242 RFC 1286 RFC 1331 RFC 1490 RFC 1525 RFC 1548 RFC 1605 RFC 1623 RFC 1662 RFC 2029 RFC 2032 RFC 2038 RFC 2043 RFC 2171 RFC 2175 RFC 2285 RFC 2496 RFC 2665 RFC 2823 RFC 2878 RFC 2889 RFC 2955 and 17 more
- Frame (HTTP/2)
The smallest unit of HTTP/2 communication: a 9-byte header (length, type, flags, stream identifier) followed by a payload. Types include DATA, HEADERS, SETTINGS and WINDOW_UPDATE.
Plain language Smallest HTTP/2 unit with 9-byte header and payload, types include DATA and HEADERS.
- Frame Check Sequence
A checksum appended to a frame by Ethernet to detect whether it has been corrupted in transmission.
Plain language An Ethernet checksum detecting transmission corruption.
Used in RFC 1284 RFC 1331 RFC 1398 RFC 1549 RFC 1570 RFC 1662 RFC 2175 RFC 2615 RFC 2684 RFC 3518 RFC 3635 RFC 4349 RFC 4719 RFC 4720
- Frame Relay
A packet-switched network service that moves variable-length frames between attached stations over virtual circuits.
Plain language A packet-switched service moving variable-length frames over virtual circuits.
Used in RFC 1294 RFC 1356 RFC 1483 RFC 1586 RFC 1634 RFC 1973 RFC 2105 RFC 2115 RFC 2390 RFC 2590 RFC 3034 RFC 3133 RFC 3292 RFC 3985 RFC 4115 RFC 4591 RFC 6310
- Frame-block
The time-synchronized set of audio frames in a multi-channel session. In an N-channel session it holds N frames, one per channel, all covering the same time period.
Plain language Time-synchronized audio frames for all channels in a multi-channel session.
- Free-busy
Information about which periods a calendar user is free or busy, without revealing the details of the events. In iCalendar it is carried in a VFREEBUSY component.
- Frequency slot
The range of optical frequency allocated to one channel on a flexible grid. It is unavailable to other channels on that link.
Plain language The optical frequency range allocated to one channel on a flexible grid.
- Front-end processor
A small computer placed between a host and a network that handles network protocol work on the host's behalf. The host then deals only with a simpler interface to the front end.
Plain language A small computer handling network protocol work on behalf of a host.
- FTP
The File Transfer Protocol. It uses one TCP connection for commands and replies and separate data connections to move files between hosts.
Plain language File Transfer Protocol, using one control connection and separate data connections for file transfer.
Used in RFC 48 RFC 87 RFC 114 RFC 133 RFC 141 RFC 146 RFC 172 RFC 180 RFC 238 RFC 265 RFC 269 RFC 278 RFC 281 RFC 283 RFC 294 RFC 310 RFC 327 RFC 354 RFC 360 RFC 385 RFC 407 RFC 409 RFC 412 RFC 414 and 148 more
A three-digit number that starts every FTP server reply. The first digit tells the client what happened: 1 means started, 2 success, 3 more input needed, 4 temporary failure and 5 permanent failure.
Plain language A three-digit number starting every FTP server reply indicating outcome.
Used in RFC 463 RFC 607 RFC 614 RFC 624 RFC 630 RFC 640 RFC 686 RFC 691 RFC 959 RFC 1846 RFC 4217 RFC 7151 RFC 7504
- Fully qualified domain name
The full name of a system, rather than just its hostname. For example, venera is a hostname and venera.isi.edu is an FQDN.
Plain language The full name of a system (like venera.isi.edu) rather than just its hostname.
Used in RFC 3646 RFC 4701 RFC 4702 RFC 4703 RFC 4704 RFC 4848 RFC 5518 RFC 6334 RFC 7022 RFC 7227 RFC 7819