Glossary
D
129 terms.
- DANE
DNS-Based Authentication of Named Entities. It lets a domain publish, in DNSSEC-signed DNS records, which certificates or keys its TLS servers use.
Like I'm five A way to write down in a tamper-proof address book which lock a place uses.
Used in RFC 6698 RFC 7672 RFC 8310 RFC 8460 RFC 8689 RFC 9102
- Data channel
A WebRTC channel for sending arbitrary application data between peers. It is built from a pair of SCTP streams that share the same stream identifier.
Like I'm five A private lane between two programs for passing any kind of message.
Used in RFC 1037 RFC 8831 RFC 8832 RFC 8850 RFC 8864 RFC 8865
- Data connection
A separate TCP connection that FTP opens to carry a file or a directory listing. By default the server uses the port one below its control port (port 20), and the user may choose other ports with PORT or PASV.
Like I'm five The second line you open only to carry the actual file.
Used in RFC 294 RFC 354 RFC 454 RFC 463 RFC 542 RFC 604 RFC 624 RFC 959 RFC 1579 RFC 1639 RFC 2228 RFC 2428 RFC 2577 RFC 3659 RFC 4217 RFC 7663
- Data Encrypting Key
A cryptographic key used to encrypt the plaintext of a message and to compute message integrity checks. A new DEK is generated for each message.
Like I'm five A key that locks up each message; each message gets a different one.
- Data Encryption Standard
DES is a symmetric cipher standardized in 1977, with a 56-bit key. It was widely used for decades but is now considered insecure against modern attacks.
Like I'm five An old code-lock system that uses only 56 bits, which is not enough anymore.
- Data Label
In TRILL, the label that scopes MAC address learning: either a VLAN or a Fine-Grained Label (FGL).
Like I'm five A tag saying which separate network a message belongs to.
- Data Link Switching
A protocol for bridging data link layer traffic (such as SNA and NetBIOS) over TCP/IP networks, used to connect legacy systems.
Like I'm five A bridge that carries old-style computer network traffic over modern Internet connections.
- Data Minimization
A privacy principle of limiting the amount of data disclosed to only what is absolutely necessary to complete a specific protocol exchange or service.
Like I'm five Only telling people information they truly need to know.
- Data model
A lower-level model of managed objects that includes the implementation and protocol-specific details needed to build and use them.
Like I'm five The detailed blueprint that tells builders exactly how to make it.
- Data Plane (Forwarding Plane)
The part of a network device that performs per-packet operations: receiving packets, looking up routes, and forwarding them to the correct output interface.
Like I'm five The hands that actually move the packets along.
- Datagram
A self-contained packet of data sent across a network with enough addressing information to be delivered on its own, without a connection set up beforehand.
Like I'm five A letter with the address on the envelope, sent on its own.
Used in RFC 59 RFC 60 RFC 68 RFC 71 RFC 240 RFC 252 RFC 255 RFC 267 RFC 270 RFC 298 RFC 303 RFC 306 RFC 321 RFC 335 RFC 342 RFC 344 RFC 353 RFC 362 RFC 366 RFC 515 RFC 528 RFC 618 RFC 662 RFC 677 and 254 more
- Datalanguage
A protocol for sending queries and results between programs over the network to access data stored in a remote database.
Like I'm five A language for asking a remote database questions over the network.
- Datastore
A conceptual place to store and access information. It might be implemented with files, a database, flash memory locations or a mix of these.
Like I'm five A place where a device keeps a full copy of its settings.
Used in RFC 6241 RFC 6244 RFC 7950 RFC 8040 RFC 8072 RFC 8342 RFC 8345 RFC 8346 RFC 8525 RFC 8526 RFC 8527
- DCCP
The Datagram Congestion Control Protocol, a transport protocol that delivers datagrams without guaranteeing delivery but with a choice of congestion control.
Like I'm five A road for messages that does not promise every message arrives but makes everyone slow down when it is crowded.
Used in RFC 4341 RFC 5238 RFC 5595 RFC 5762 RFC 6773 RFC 9897
- DDDS
The Dynamic Delegation Discovery System, an abstract algorithm that applies dynamically retrieved string transformation rules to an application-unique string until a terminal condition is reached.
Like I'm five A treasure hunt where each clue tells you how to find the next one.
- DDoS attack
A distributed denial-of-service attack, in which traffic from many sources is directed at a target to harm its availability or functionality.
Like I'm five A huge crowd all knocking on one shop door at once so real customers cannot get in.
Used in RFC 4948 RFC 8612 RFC 9066 RFC 9132 RFC 9244 RFC 9387
- De-jitter buffer
A receiver buffer that holds arriving packets for a short time before playing them out, so that variation in arrival times does not disturb real-time media.
Like I'm five A waiting area that lets late items catch up before they are used.
- De-skewing
Processing a biased or lopsided stream of bits, for example one that has too many ones, to make it closer to an even mix of zeros and ones. Simple methods are taking the parity of a run of bits and von Neumann's pair-dropping trick.
Like I'm five Fixing a coin that lands on heads too often so that heads and tails come out fair.
Used in RFC 4086
- Dead peer detection
An IKE mechanism by which a node concludes that its remote peer is dead or has rebooted. RFC 5660 lets such a conclusion break connection latches with that peer.
Like I'm five Checking whether the friend on the other end of the line is still there.
- Decoder refresh point
A bit string, sent in one or more RTP packets, that completely resets a media decoder to a known state. Examples include Intra pictures, IDR pictures and keyframes.
Like I'm five A clean start for the picture, so the viewer can stop relying on anything it missed.
- Deep Packet Inspection
Examination of the full content of network packets to identify traffic types and apply network policies. DPI can see the content of user communications and raises privacy concerns.
Like I'm five Looking inside every internet package to see exactly what's in it, which some people say is snooping.
- DEFLATE
A lossless compression method that other formats, such as zlib and gzip, use to store their compressed data.
Like I'm five A clever way of packing data smaller that other formats borrow.
- Delay-tolerant networking
A networking approach for links that are slow, intermittent or disrupted. Nodes pass data along as self-contained bundles using store-and-forward delivery.
Like I'm five A postal system for networks that are often broken, where each stop holds the parcel until the next road opens.
Used in RFC 4838 RFC 5050 RFC 6257 RFC 8884 RFC 9171 RFC 9173 RFC 9891
- Delegated credential
A short-lived credential, issued under a certificate holder's authority, that lets another server prove its identity in a TLS handshake without using the certificate's own private key.
Like I'm five A temporary pass that lets someone else vouch for you for a little while.
- Delegation
Handing responsibility for part of a name or number space to another party, who then manages the data for that part.
Like I'm five When one person hands a job to someone else who looks after it from then on.
Used in RFC 2317 RFC 2743 RFC 3010 RFC 3402 RFC 3530 RFC 5661 RFC 7530 RFC 8693 RFC 8751 RFC 8881 RFC 9754
- Delivery status notification
A message generated by a mail system to tell a sender whether a message was delivered or failed. It is often shortened to DSN.
Like I'm five A note sent back to say whether your letter arrived or not.
Used in RFC 1893 RFC 2532 RFC 2852 RFC 3459 RFC 3461 RFC 3463 RFC 3464 RFC 5429 RFC 6009 RFC 6522 RFC 6533 RFC 7505
- Delta encoding
Representing a new version of data as a set of differences from an older version, so only the changes need to be stored or sent.
Like I'm five Instead of sending a whole new page, you send only a list of what changed.
- Delta sampling
Sampling a value twice and using the difference between the two samples rather than the raw value. It is how counters, which only grow, are made meaningful.
Like I'm five Instead of asking how many cars have ever passed, you ask how many passed since the last time you looked.
- Delta time
The time between one event and the one before it, written in a compact form. In RTP MIDI each command's timestamp is built by adding up delta times.
Like I'm five How long to wait after the last thing before doing the next one.
- Demand circuit
A link that is brought up only when there is traffic to send and may be torn down when idle. OSPF suppresses periodic Hello packets on such links to avoid keeping them up.
Like I'm five A phone call you only make when you have something to say, so you do not pay while it is quiet.
- Demilitarized Zone
A subnet between a private network and the external internet, containing servers (like web and mail) that need to be accessible from outside.
Like I'm five A security buffer zone containing public-facing servers, like the front desk of a building, between the outside street and the private offices inside.
- Demultiplexing
Sorting arriving data to the right receiver, for example by looking at the first byte of a packet or the destination port.
Like I'm five Sorting the mail into the right mailbox when it arrives.
- Denial of Service (DoS)
An attack that floods a network or service with traffic to prevent legitimate users from accessing it.
Like I'm five Overwhelming a service with so many requests that real users cannot use it.
Used in RFC 1281 RFC 3552 RFC 3837 RFC 4732 RFC 5327 RFC 5713 RFC 5920 RFC 6045 RFC 6192 RFC 6274 RFC 6324 RFC 6398 RFC 6584 RFC 7999
- DER encoding
The Distinguished Encoding Rules, a strict form of BER in which every value has exactly one possible encoding. That uniqueness is needed when bytes are signed or hashed, so CMS requires signed and authenticated attributes to use it.
Like I'm five A rule that says there is only one correct way to write something down, so two people always write it identically.
Used in RFC 2025 RFC 2315 RFC 2437 RFC 2503 RFC 2585 RFC 2630 RFC 2943 RFC 2984 RFC 2985 RFC 2986 RFC 3125 RFC 3274 RFC 3279 RFC 3369 RFC 3560 RFC 3641 RFC 3657 RFC 3709 RFC 3779 RFC 3852 RFC 4010 RFC 4055 RFC 4108 RFC 4178 and 57 more
- Derivative work
A new work that is based on or includes all or part of an earlier work, such as a revised or adapted version of a document.
Like I'm five A new version of something that is built from the old one, like a remix of a song.
- Designated Expert
An expert selected by IANA to review specifications for IANA registries and make registration decisions without requiring a full RFC.
Like I'm five A person that IANA picks to review and approve new entries in the registry without needing a whole RFC.
Used in RFC 3864 RFC 5226 RFC 5727 RFC 6117 RFC 6118 RFC 7451 RFC 7595 RFC 8126 RFC 8726 RFC 9748
- Designated Forwarder
The one provider edge chosen to handle forwarding for a given segment or VLAN so that traffic is not duplicated or looped.
Like I'm five The one helper picked to do a job so that two helpers do not both do it.
Used in RFC 5015 RFC 7432 RFC 7734 RFC 7781 RFC 8584 RFC 9722 RFC 9784 RFC 9785 RFC 9786 RFC 9856
- Designated RBridge
The single RBridge elected on each link to choose the Designated VLAN and to appoint which RBridge forwards each VLAN's traffic.
Like I'm five The one RBridge on a street picked to be in charge of who does what.
- Designated Router (DR)
On a multi-access network such as Ethernet, the router elected to form adjacencies with all others and originate the network's Network-LSA, so not every pair of routers needs to synchronize.
Like I'm five The class monitor who collects everyone's news so students do not all have to talk to each other.
Used in RFC 1075 RFC 1131 RFC 1195 RFC 1245 RFC 1247 RFC 1252 RFC 1583 RFC 1584 RFC 1629 RFC 1793 RFC 2117 RFC 2178 RFC 2189 RFC 2328 RFC 2362 RFC 2642 RFC 2740 RFC 2934 RFC 3623 RFC 3630 RFC 4061 RFC 4062 RFC 4063 RFC 4201 and 39 more
- Detached payload
A signed payload that is not carried inside the signature object and is sent or stored separately. The signature still covers it, so the verifier needs both pieces.
Like I'm five The signed note travels in a different envelope from its signature, and you need both to check it.
- Detached signature
A digital signature stored in a separate file from the data it signs. The original file stays unchanged, so programs that read it are unaffected.
Like I'm five A signature kept on a separate card instead of written on the page itself.
- Detection Time
The period without receiving expected liveness packets after which a session is declared to have failed. The receiver works it out from the agreed interval and a multiplier.
Like I'm five How long you wait for a hello before you decide your friend is gone.
- Deterministic Networking
A service a network can offer to DetNet flows, giving them extremely low packet loss rates and an assured maximum end-to-end delivery latency.
Like I'm five A promise that your packets arrive on time and almost never get lost.
Used in RFC 8557 RFC 8578 RFC 8964 RFC 9016 RFC 9024 RFC 9025 RFC 9034 RFC 9055 RFC 9056 RFC 9550 RFC 9634
- DetNet
Deterministic Networking: carrying real-time unicast or multicast flows with extremely low packet loss and an assured maximum end-to-end delivery latency.
Like I'm five A network that promises messages show up on time and almost never get lost.
- Device fingerprinting
Identifying a device, or its software type and version, from small characteristic differences such as which protocol options it sends and in what order. It works even when no explicit identifier is present.
Like I'm five Recognizing someone by how they walk instead of by their name tag.
- Device under test
The switch, router or other piece of equipment being measured in a benchmark. It is usually abbreviated DUT.
Like I'm five The thing being tested, like the runner being timed in a race.
Used in RFC 2544 RFC 3918 RFC 6201 RFC 6412 RFC 7501 RFC 7502 RFC 8238 RFC 8456 RFC 9004 RFC 9411
- DHCP
The Dynamic Host Configuration Protocol. It leases IP addresses to clients and delivers options such as gateway and DNS servers. It grew out of BOOTP and is what most devices use today.
Like I'm five A friendly helper that lends your computer an address for a while and tells it where everything else is.
Used in RFC 903 RFC 950 RFC 951 RFC 1048 RFC 1084 RFC 1350 RFC 1395 RFC 1531 RFC 1533 RFC 1534 RFC 1541 RFC 1542 RFC 1628 RFC 1678 RFC 1787 RFC 1900 RFC 1931 RFC 2008 RFC 2071 RFC 2072 RFC 2131 RFC 2132 RFC 2136 RFC 2165 and 294 more
- DHCP binding
The record a DHCP server keeps that ties an address or delegated prefix to a client, together with related data such as lease times.
Like I'm five The server's note saying which device has which address.
- DHCP option
A tagged item of configuration carried in the variable-length options field of a DHCP message, such as the subnet mask, the router list or the lease time. Each option has a numeric code that says what it is.
Like I'm five One labelled line on a form, like "Door number: 3", that tells the computer one thing about the network.
Used in RFC 1048 RFC 1497 RFC 1533 RFC 1534 RFC 1541 RFC 2131 RFC 2132 RFC 2165 RFC 2241 RFC 2242 RFC 2489 RFC 2563 RFC 2610 RFC 2939 RFC 3004 RFC 3011 RFC 3046 RFC 3118 RFC 3203 RFC 3315 RFC 3319 RFC 3361 RFC 3396 RFC 3397 and 108 more
- DHCPv6
The Dynamic Host Configuration Protocol for IPv6. It allows IPv6 hosts to obtain network configuration information and addresses from servers on the network.
Like I'm five A helper that tells your computer its IPv6 address and where to find things on the internet.
- DHCPv6 Prefix Delegation
A mechanism in DHCPv6 that allows a server to delegate entire IPv6 address prefixes to clients, who can then use these prefixes for their own addressing or extend them to networks they manage.
Like I'm five A server hands out chunks of address space to devices instead of individual addresses.
- Diameter
A AAA protocol defined in RFC 3588. Clients such as network access servers send it requests, and a Diameter server answers them.
Like I'm five A way for helpers to ask a central office questions about who may do what.
Used in RFC 3127 RFC 4006 RFC 4072 RFC 4740 RFC 5447 RFC 5778 RFC 5779 RFC 5866 RFC 6159 RFC 6734 RFC 6735 RFC 6736 RFC 6942 RFC 7156 RFC 7423 RFC 7683 RFC 7944 RFC 7966 RFC 8506 RFC 8583 RFC 9390
- Dictionary attack
An attack that guesses a password by trying a long list of likely candidates and checking each against captured or stored data.
Like I'm five Trying one likely password after another until one works.
Used in RFC 2945 RFC 3767 RFC 4279 RFC 5018 RFC 5433 RFC 5802 RFC 5931 RFC 6124 RFC 6617 RFC 8146 RFC 9588
- DIF Block
The basic unit of DV stream data, exactly 80 bytes in size, containing either video, audio, timing, or metadata information.
Like I'm five An 80-byte chunk of video or audio data, the smallest piece DV is broken into.
- Differentiated Services
A QoS architecture (DiffServ) in which routers treat packets based on a service code point marked in the packet header, without maintaining per-flow state.
Like I'm five Apps mark packets with a priority level, and routers treat marked packets nicely without remembering individual apps.
- Diffie-Hellman
A way for two parties to arrive at the same shared secret over a public channel, so that an eavesdropper who sees everything cannot work it out.
Like I'm five A trick that lets two people end up with the same secret without ever saying it.
Used in RFC 1057 RFC 2025 RFC 2094 RFC 2356 RFC 2409 RFC 2412 RFC 2522 RFC 2523 RFC 2539 RFC 2630 RFC 2631 RFC 2636 RFC 2695 RFC 2785 RFC 2786 RFC 2847 RFC 2875 RFC 2930 RFC 2945 RFC 2946 RFC 3268 RFC 3279 RFC 3370 RFC 3526 and 133 more
- Diffserv
Differentiated Services, a QoS architecture that marks packets with priority levels and handles them according to their marking, without per-flow reservations.
Like I'm five A system where packets are labeled by importance, and the network gives faster service to more important packets.
- Digest authentication
An authentication method where a client proves knowledge of a password by hashing the password along with a server-provided nonce, avoiding transmission of the password itself.
Like I'm five Proving you know a secret by mixing it with a random question and showing the scrambled result, instead of showing the secret directly.
- Digit map
A dialing plan stored in a gateway that lists digit patterns to match. It lets the gateway report a complete dialed number at once instead of reporting every digit separately.
Like I'm five A list of phone number shapes so the gateway knows when someone has finished dialing.
- Digital envelope
Encrypted content packaged together with the content-encryption key, itself encrypted for one recipient. Opening it means decrypting the key first and then the content.
Like I'm five A locked box with a second tiny locked box inside holding the key to the big one.
- Digital signature
A value computed from some data with a private key, which anyone holding the matching public key can check. A valid signature shows the data has not changed since signing and that the holder of the private key produced it.
Like I'm five A seal only one person can make but anyone can check.
Used in RFC 1113 RFC 1114 RFC 1186 RFC 1319 RFC 1320 RFC 1321 RFC 1421 RFC 1422 RFC 1423 RFC 1424 RFC 1505 RFC 1507 RFC 1704 RFC 1805 RFC 1824 RFC 1826 RFC 1847 RFC 1848 RFC 1898 RFC 1984 RFC 1991 RFC 2015 RFC 2025 RFC 2065 and 448 more
- Dijkstra Algorithm
A graph search algorithm that finds the shortest path between a source and all other nodes by iteratively visiting the closest unvisited node and updating distance estimates.
Like I'm five A way to find the quickest route from one place to all other places by always going to the nearest unvisited stop next.
- Direct Data Placement
A way of moving a data payload straight into a pre-arranged region of the receiver's memory instead of passing it through intermediate message buffers.
Like I'm five Dropping a package right into the correct room instead of leaving it at the front door.
- Directed Acyclic Graph
A routing structure with no loops where edges point toward a root, used by RPL to organize LLN traffic flow.
Like I'm five A tree-like structure for routing that has no loops.
- Directory Agent
An SLP component that automatically gathers service advertisements from Service Agents so that User Agents can query them in one place.
Like I'm five A noticeboard where services pin up notes about themselves.
- Directory entry
A record in an LDAP directory representing a person, organization, or resource, stored as a set of attributes with values.
Like I'm five One person's or company's information in the address book.
- Directory Information Tree
The hierarchy of entries in an X.500 or LDAP directory. Each entry is found by a name made of its position in the tree.
Like I'm five A family tree of entries, where you find someone by following the branches down to them.
Used in RFC 1255 RFC 1279 RFC 1617 RFC 1943 RFC 2164 RFC 2251 RFC 2293 RFC 3672 RFC 4104 RFC 4512
- Directory Service
A service that maintains information about people, resources, or entities and allows clients to query and retrieve that information using a defined protocol.
Like I'm five A system where you can look up information about people or things.
Used in RFC 1558 RFC 1616 RFC 2345 RFC 2970 RFC 3712 RFC 4157
- Directory System Agent
A server that holds a portion of the directory tree and responds to directory queries (binds) from clients.
Like I'm five A server that keeps part of the address book and lets people look things up in it.
- Directory User Agent
An X.500 client component that allows users or applications to query and interact with Directory System Agents.
Like I'm five The program that lets you search the phone book by sending questions to a server.
- Directory User Agent (DUA)
A client application that users interact with to search and retrieve information from an X.500 directory.
Like I'm five A program that lets someone ask the phone book questions.
- Discontinuous transmission (DTX)
A technique where a sender reduces or stops sending packets during silence. The receiver fills the gaps, which saves bandwidth.
Like I'm five Not talking while nobody is speaking, so you do not waste words.
- Discovery domain
A named group that limits which entities are allowed to discover each other within a larger scope. An entity can belong to several domains.
Like I'm five A club list that says who is allowed to see whom.
- Discrete-Logarithm Cryptography
Cryptographic operations based on the difficulty of computing logarithms in finite groups. In these algorithms, exponentiation is performed modulo a large prime number (mod q).
Like I'm five Math based on big numbers and modular arithmetic.
- Disjunctive normal form
A way of writing a logical condition as an OR of AND lists. It is true when every item in at least one of the AND lists is true.
Like I'm five A yes-or-no question built from smaller groups, where any one group being all yes is enough.
- Diskless workstation
A computer with no local disk that loads its operating system over the network at boot. It must first learn its own network address from outside.
Like I'm five A computer with no memory of its own, so every morning it has to ask where it lives.
Used in RFC 903 RFC 906 RFC 917 RFC 950 RFC 951 RFC 1123 RFC 1350 RFC 1931 RFC 2603 RFC 4173
- Distance-vector routing
A routing approach in which each router tells its neighbours only the distance to every destination and picks the neighbour giving the smallest total. RIP is the classic example.
Like I'm five Each helper only tells friends how many steps away things are, never the whole map.
Used in RFC 891 RFC 975 RFC 1058 RFC 1075 RFC 1322 RFC 1387 RFC 1388 RFC 1476 RFC 1582 RFC 1722 RFC 1723 RFC 1762 RFC 1774 RFC 1923 RFC 2080 RFC 2081 RFC 2091 RFC 2174 RFC 2328 RFC 2453 RFC 3561 RFC 4822 RFC 6126 RFC 6550 and 14 more
- Distinguished name
An X.500 name that identifies something through a hierarchy of parts. In RFC 2872 it carries the application locator.
Like I'm five A full address that goes from big to small, like country, city and street.
Used in RFC 1107 RFC 1114 RFC 1214 RFC 1255 RFC 1309 RFC 1373 RFC 1430 RFC 1487 RFC 1567 RFC 1779 RFC 1781 RFC 1804 RFC 1823 RFC 1836 RFC 1837 RFC 1959 RFC 2247 RFC 2251 RFC 2252 RFC 2253 RFC 2255 RFC 2293 RFC 2314 RFC 2377 and 14 more
- Distributed Hash Table (DHT)
A data structure distributed across a network of peers that allows any peer to store and retrieve data by key without a central server.
Like I'm five A phone book spread across many computers so anyone can look up anyone else.
Used in RFC 4981 RFC 5694 RFC 5765 RFC 6029 RFC 6537 RFC 6940 RFC 7019 RFC 7374 RFC 7851 RFC 7890
- Distributed speech recognition
A design in which a device does the first signal processing of speech and sends a compact representation to a server. The server then finishes the recognition.
Like I'm five The phone does the first half of the listening and a bigger computer does the rest.
- Distribution tree
A loop-free tree of links over which a network sends multi-destination traffic, so that every interested switch receives a copy exactly once.
Like I'm five A branching route that lets one message reach many people without going in circles.
- DKIM
DomainKeys Identified Mail; the successor to DomainKeys, defined in RFC 4871, with improved design and wider deployment.
Like I'm five A newer, better version of the DomainKeys email signature system.
Used in RFC 4686 RFC 4870 RFC 6008 RFC 6541 RFC 6651 RFC 7070 RFC 7960 RFC 8058 RFC 8301 RFC 8463 RFC 8601 RFC 8617 RFC 9989
- DKIM selector
A label chosen by a signing domain that picks one of its DKIM keys. It appears in the
s=tag of a signature, and the public key is published atselector._domainkey.domain. Selectors let a domain run several keys and rotate them without interruption.Like I'm five The name of the particular stamp a sender used, so you know which picture in the public book to compare it with.
Used in RFC 4686 RFC 4871 RFC 5451 RFC 5585 RFC 5617 RFC 5672 RFC 5863 RFC 6376 RFC 6591 RFC 6651 RFC 7073 RFC 8301 RFC 8463 RFC 8616 RFC 8617 RFC 9091 RFC 9991
- DLCI
A Data Link Connection Identifier is the number that identifies a virtual circuit at a Frame Relay interface. It usually has only local meaning.
Like I'm five The number of the lane you are using on the road.
- DLEP
The Dynamic Link Exchange Protocol lets a radio or other modem tell its attached router about the state of a link. It is defined in RFC 8175 and can be extended.
Like I'm five A way for a radio box to tell the router how good the connection is right now.
- DMARC
Domain-based Message Authentication, Reporting, and Conformance, a mechanism that lets a domain owner publish a policy for mail that uses its domain and request reports about it.
Like I'm five A set of rules a school publishes saying what to do with letters that pretend to come from it, plus a request for reports.
- DNS
The Domain Name System, which maps names such as example.com to data such as IP addresses. Domain labels in the DNS are traditionally limited to 63 characters.
Like I'm five The internet's phone book that turns a name into an address.
Used in RFC 87 RFC 616 RFC 620 RFC 623 RFC 805 RFC 810 RFC 819 RFC 830 RFC 849 RFC 881 RFC 882 RFC 883 RFC 897 RFC 899 RFC 920 RFC 921 RFC 952 RFC 973 RFC 974 RFC 1001 RFC 1011 RFC 1026 RFC 1031 RFC 1032 and 601 more
- DNS over TLS (DoT)
Sending ordinary DNS messages inside a TLS-protected TCP connection, by default to port 853, so that the queries and answers cannot be read on the network path.
Like I'm five DNS questions asked inside a private tunnel so nobody can listen in.
Used in RFC 7766 RFC 7858 RFC 8094 RFC 8310 RFC 8467 RFC 8490 RFC 8765 RFC 8781 RFC 8932 RFC 9076 RFC 9103 RFC 9210 RFC 9250 RFC 9445 RFC 9461 RFC 9462 RFC 9463 RFC 9464 RFC 9527 RFC 9539 RFC 9606 RFC 9726 RFC 9852 RFC 9953
- DNS TXT record
A kind of DNS record that holds free-form text for a name. It is used for many things, including publishing DKIM public keys, where the text is a list of
tag=valuepairs.Like I'm five A little note pinned to a name in the internet's phone book.
Used in RFC 1183 RFC 1383 RFC 1464 RFC 4408 RFC 4871 RFC 5518 RFC 5585 RFC 5617 RFC 5782 RFC 5863 RFC 6376 RFC 6591 RFC 6651 RFC 6686 RFC 6762 RFC 6763 RFC 6764 RFC 7208 RFC 7489 RFC 7808 RFC 8301 RFC 8460 RFC 8461 RFC 8463 and 13 more
- DNS Whitelist
A DNS-based list of IP addresses or domain names with good reputation, used to identify legitimate email senders. The opposite of a blocklist.
Like I'm five A list of good email senders you can trust, checked the same way as blocklists.
- DNS64
A mechanism that synthesizes AAAA records from A records, so an IPv6-only host gets an IPv6 address to use for an IPv4-only name.
Like I'm five A phone book that makes up a new-style number for an old-style one.
Used in RFC 6146 RFC 6889 RFC 7050 RFC 7051 RFC 7269 RFC 8781 RFC 8880
- DNSKEY
The DNSSEC record that publishes a zone's public key so resolvers can verify signatures made with the matching private key.
Like I'm five The public stamp pattern you compare a seal against.
Used in RFC 3110 RFC 3445 RFC 3755 RFC 3757 RFC 4033 RFC 4034 RFC 4035 RFC 4310 RFC 4398 RFC 4470 RFC 4509 RFC 4986 RFC 5011 RFC 5702 RFC 5910 RFC 5933 RFC 6605 RFC 6725 RFC 6781 RFC 6840 RFC 6944 RFC 6975 RFC 7344 RFC 7583 and 19 more
- DNSSEC
The DNS Security Extensions: new record types and protocol changes that add digital signatures to DNS data, giving data origin authentication and integrity (but not confidentiality).
Like I'm five A system of wax seals for DNS answers, so you can tell nobody changed them.
Used in RFC 2065 RFC 2137 RFC 2181 RFC 2230 RFC 2308 RFC 2316 RFC 2535 RFC 2536 RFC 2540 RFC 2541 RFC 2672 RFC 2673 RFC 2826 RFC 2870 RFC 2874 RFC 2916 RFC 2931 RFC 3007 RFC 3008 RFC 3090 RFC 3110 RFC 3130 RFC 3191 RFC 3225 and 217 more
- DO bit
DNSSEC OK. A flag in the EDNS OPT pseudo-record of a query. When set, it tells the server the client understands DNSSEC and wants RRSIG, NSEC and DS records in the response.
Like I'm five A raised hand that says "I can read seals, please include them."
Used in RFC 4035
- DOCSIS
Data Over Cable Service Interface Specifications, the set of specifications that define how cable modems and the head-end equipment carry data over a cable television network.
Like I'm five The rulebook that lets your cable modem talk to the cable company over the same wire as TV.
- Document Shepherd
An experienced community member designated to shepherd a document through the final stages of review and into the IESG, ensuring quality and completeness.
Like I'm five An experienced person who guides a document through the final review process before it becomes a standard.
- Document Type Definition
A set of rules that defines the structure and syntax of valid XML documents, including which elements are allowed, their attributes, and how they can be nested.
Like I'm five A recipe that describes what the ingredients are and how they should be arranged in an XML document.
- DODAG
A Destination-Oriented Directed Acyclic Graph: a set of nodes and one-way links with no cycles, in which every path leads toward a single root.
Like I'm five Like a family tree turned upside down, where every branch eventually leads back to one trunk.
Used in RFC 6550 RFC 6552 RFC 8036 RFC 9010 RFC 9035 RFC 9854 RFC 9866 RFC 9914
- DoH (DNS over HTTPS)
A protocol that carries each DNS query and response as one HTTP exchange over an https URI, so TLS protects it. Defined in RFC 8484.
Like I'm five Asking the phone book for a number through the normal, private web connection instead of shouting it.
Used in RFC 8484 RFC 8932 RFC 9076 RFC 9230 RFC 9445 RFC 9458 RFC 9461 RFC 9462 RFC 9463 RFC 9464 RFC 9540 RFC 9606 RFC 9726 RFC 9761 RFC 9953
- Domain Identifier
A unique identifier assigned to an AppleTalk network to distinguish it from other networks on an AURP tunnel.
Like I'm five A label that says which AppleTalk network a message came from and is going to.
- Domain name space
The tree of names used by DNS. Each node has a label, and a domain name is the labels from a node up to the root, separated by dots.
Like I'm five An upside-down family tree where a name lists your branch all the way up to the top.
Used in RFC 799 RFC 805 RFC 819 RFC 830 RFC 882 RFC 897 RFC 920 RFC 921 RFC 952 RFC 976 RFC 1032 RFC 1034 RFC 1118 RFC 1124 RFC 1178 RFC 1206 RFC 1394 RFC 1480 RFC 1535 RFC 1591 RFC 1706 RFC 1714 RFC 1788 RFC 1811 and 55 more
- Domain of Interpretation
A specification that fills in algorithm choices, naming schemes, and payload formats for ISAKMP in a particular context, such as the Internet IP Security DOI for IPsec.
Like I'm five A rule book that says which secret codes are allowed to use with ISAKMP.
- Domain-Specific Part
The second major part of an NSAP address, allocated and interpreted by the authority identified by the IDI; contains the actual address within a domain.
Like I'm five The unique address number within the area that the IDI pointed to.
- Don't Fragment (DF) bit
A flag in the IP header. When it is set, a router must not split the datagram; if the datagram is too big for the next link the router throws it away and reports an error instead.
Like I'm five A sticker on a box that says, "Do not cut me up. If I do not fit, tell me."
Used in RFC 791 RFC 792 RFC 1191 RFC 2923 RFC 4149 RFC 4213 RFC 4413 RFC 4459 RFC 4787 RFC 4821 RFC 6145 RFC 6864 RFC 7915 RFC 9869
- DORA
The four-message DHCP exchange of Discover, Offer, Request and Acknowledge by which a client obtains an address and lease.
Like I'm five Four lines of a short chat: "Anyone?", "Here you go", "I'll take it", "It's yours."
Used in RFC 2131
- Dormant Mode
A power-saving state where a mobile host is no longer listening for packets but is still reachable by paging through a specialized protocol or link-layer mechanism.
Like I'm five When a phone is asleep but can still be woken up if someone tries to reach it.
- Dot-segments
The path segments
.(stay here) and..(go up one level). They are only meaningful in relative references and are removed during reference resolution.Like I'm five "Stay here" and "go up one folder" written as dots.
- Dot-stuffing
A way to send multi-line text that ends with a line holding a single dot. Any data line that begins with a dot gets an extra dot added by the sender, and the receiver removes it.
Like I'm five Doubling a dot at the start of a line so it is not mistaken for the signal that the message is over.
- DOTS
DDoS Open Threat Signaling, an architecture in which a DOTS client asks an upstream DOTS server to mitigate a distributed denial-of-service attack. It uses a signal channel and a data channel.
Like I'm five A way for a victim of a flood of junk traffic to call for help from a bigger network.
- Dotted decimal
A way of writing a 32-bit IPv4 address as four 8-bit values in decimal, separated by periods, such as 10.1.0.52.
Like I'm five Writing a long number as four small numbers with dots between them.
- Downgrade attack
An active attack that alters negotiation messages so that both sides end up using the weakest security option they both support.
Like I'm five A trick that makes two people agree to use the flimsiest lock.
Used in RFC 4178 RFC 4422 RFC 4509 RFC 4991 RFC 5021 RFC 7401 RFC 7457 RFC 7672 RFC 7696 RFC 8461 RFC 8996 RFC 9368 RFC 9848
- Draft Standard
A maturity level in RFC 2026 requiring two independent, interoperable implementations. RFC 6410 later removed it as a step for new advancement.
Like I'm five A well-tested version that two different teams have built and made work together.
Used in RFC 1100 RFC 1140 RFC 1160 RFC 1264 RFC 1266 RFC 1280 RFC 1410 RFC 1500 RFC 1540 RFC 1600 RFC 1602 RFC 1610 RFC 1773 RFC 1780 RFC 1796 RFC 1880 RFC 2000 RFC 2026 RFC 2200 RFC 2438 RFC 2499 RFC 2600 RFC 2700 RFC 2800 and 12 more
- DRIP Entity Tag (DET)
The name for a HHIT when it is used as an Unmanned Aircraft System Remote ID. It identifies a drone and points to the registry that holds its record.
Like I'm five The special ID tag a drone broadcasts.
- DS domain
A contiguous part of the Internet where a consistent set of differentiated services policies is administered together. Its edge is the DS boundary, where packets are classified and marked.
Like I'm five A neighborhood whose post offices all follow the same sticker rules.
- DS field
The 8-bit IP header octet (the IPv4 TOS octet or IPv6 Traffic Class octet) when read as defined in RFC 2474: a 6-bit DSCP followed by 2 currently unused bits.
Like I'm five The little sticker on the outside of a parcel that says how it should be handled.
Used in RFC 2474 RFC 2475 RFC 2780 RFC 2836 RFC 3086 RFC 5696 RFC 9892
- DS record
Delegation Signer. A record in a parent zone, at the delegation point, that holds a hash of a child zone's DNSKEY and so links the parent's signatures to the child's keys.
Like I'm five A note from the city office saying which stamp the neighborhood uses.
Used in RFC 3658 RFC 3755 RFC 4033 RFC 4034 RFC 4035 RFC 4509 RFC 4955 RFC 4956 RFC 4986 RFC 5011 RFC 5074 RFC 5155 RFC 5910 RFC 5933 RFC 6605 RFC 6781 RFC 6840 RFC 6841 RFC 6975 RFC 7344 RFC 7583 RFC 7646 RFC 8027 RFC 8078 and 16 more
- DSA
Directory Service Agent; a server implementing the X.500 directory protocol.
Like I'm five A librarian who knows where books are and helps you find them.
Used in RFC 1491 RFC 1564 RFC 1632 RFC 1803 RFC 2120 RFC 9500
- DSCP
Differentiated Services Codepoint: the 6-bit part of the DS field. Routers match the whole value, usually through a table, to pick a per-hop behavior. There are 64 possible values.
Like I'm five The part of the sticker that picks which pile your parcel goes in.
Used in RFC 1349 RFC 2474 RFC 2475 RFC 2584 RFC 2597 RFC 2697 RFC 2698 RFC 2724 RFC 2836 RFC 2873 RFC 2983 RFC 2996 RFC 2997 RFC 2998 RFC 3086 RFC 3140 RFC 3168 RFC 3175 RFC 3246 RFC 3270 RFC 3287 RFC 3289 RFC 3290 RFC 3308 and 106 more
- DSLAM
Digital Subscriber Line Access Multiplexer, the device at the central office that terminates many DSL lines. One such device can be managed by a single SNMP agent.
Like I'm five The phone company box that many home internet wires plug into.
- DTLS
Datagram Transport Layer Security, a version of TLS designed to protect datagram traffic such as UDP packets.
Like I'm five A lock for postcards-style messages, like TLS is for phone calls.
Used in RFC 5238 RFC 5415 RFC 5763 RFC 5764 RFC 5953 RFC 6012 RFC 6083 RFC 6084 RFC 6353 RFC 7252 RFC 7345 RFC 7350 RFC 7510 RFC 7879 RFC 7925 RFC 7978 RFC 7983 RFC 8086 RFC 8094 RFC 8261 RFC 8310 RFC 8827 RFC 8831 RFC 8832 and 14 more
- DTMF
Dual-tone multi-frequency signaling, the tones a phone keypad makes when a key is pressed. MSML can detect, collect and generate these digits.
Like I'm five The beeps your phone makes when you press its number buttons.
Used in RFC 1789 RFC 2806 RFC 2833 RFC 2846 RFC 4730 RFC 4733 RFC 5022 RFC 5552 RFC 5707 RFC 6231 RFC 6787 RFC 7195
- DTN Bundle
The protocol data unit in Delay-Tolerant Networking, containing a primary block, optional extension blocks including PHIB, and a payload.
Like I'm five A package in a delay-tolerant network, with headers and a payload.
- Dual-stack
A network node or service that supports both IPv4 and IPv6 simultaneously.
Like I'm five A machine that understands both old and new style internet addresses.
Used in RFC 2893 RFC 3089 RFC 3338 RFC 3795 RFC 3974 RFC 4038 RFC 4057 RFC 4213 RFC 4472 RFC 4477 RFC 4554 RFC 4852 RFC 4977 RFC 5454 RFC 6036 RFC 6127 RFC 6180 RFC 6312 RFC 6333 RFC 6342 RFC 6556 RFC 6589 RFC 6724 RFC 6908 and 8 more
- Dual-Stack Lite
A way to give customers IPv4 connectivity across an IPv6-only provider network, using an IPv4-in-IPv6 tunnel and a carrier-grade NAT.
Like I'm five A trick that lets old IPv4 traffic ride inside new IPv6 traffic.
- DUID
DHCPv6 Unique Identifier. A unique identifier assigned to each DHCPv6 client to distinguish it from other clients on the network.
Like I'm five A unique ID number that DHCPv6 gives to each device so the server knows which device is asking for an address.
Used in RFC 3315 RFC 4361 RFC 4477 RFC 4701 RFC 5460 RFC 7824 RFC 7844 RFC 7943 RFC 8371 RFC 8415 RFC 9243 RFC 9915
- Duplicate acknowledgment
An acknowledgment that repeats the same cumulative sequence number as an earlier one. A TCP receiver sends one whenever a segment arrives out of order.
Like I'm five It is the receiver saying again, 'I am still waiting for the same piece.'
- Duplicate Address Detection
A check, done with a Neighbor Solicitation sent from the unspecified address, that nobody else on the link already uses an address a node wants to configure. It is specified in the autoconfiguration RFC and uses Neighbor Discovery messages.
Like I'm five Asking the room “does anyone already have this name tag?” before you put it on.
Used in RFC 1971 RFC 2461 RFC 2462 RFC 2590 RFC 3572 RFC 3590 RFC 3627 RFC 3756 RFC 3775 RFC 3971 RFC 3972 RFC 4294 RFC 4429 RFC 4489 RFC 4861 RFC 4862 RFC 4890 RFC 4941 RFC 4968 RFC 5072 RFC 5121 RFC 5568 RFC 6059 RFC 6275 and 34 more
- Duplicate packet detection
A mechanism in which a router records recently processed packets and silently drops later copies. SMF supports identification-based and hash-based forms of it.
Like I'm five Remembering which notes you have already seen so you do not pass the same one twice.