Glossary
A
129 terms.
- A-label
The ASCII form of an internationalized domain name label, as used in the DNS. Every U-label has an equivalent A-label.
Like I'm five The plain-letters spelling of a name that is written with fancy letters.
Used in RFC 5890 RFC 5894 RFC 6531 RFC 8222 RFC 8399 RFC 8616 RFC 9598
- A6 record
A DNS resource record type from RFC 2874 that stores part of an IPv6 address plus a pointer to a prefix name. Chaining A6 records builds the full address.
Like I'm five A phone-book entry that holds only part of an address and points to another entry for the rest.
- AAA
Authentication, Authorization and Accounting: checking who a user is, deciding what that user may do, and recording what was used.
Like I'm five Checking who you are, deciding what you may do, and keeping count of what you used.
Used in RFC 2989 RFC 3127 RFC 3169 RFC 3539 RFC 3748 RFC 4006 RFC 4962 RFC 5637 RFC 5778 RFC 5779 RFC 6065 RFC 6159 RFC 6630 RFC 6677 RFC 6696 RFC 6733 RFC 7155 RFC 7156 RFC 7542 RFC 8907 RFC 9950
- AAA Server
A server that handles Authentication, Authorization and Accounting for network access. A home network may run several of them for redundancy.
Like I'm five The front desk that checks who you are, what you may do, and keeps count of what you used.
- AAAA record
A DNS resource record that maps a domain name to an IPv6 address.
Like I'm five A phone book entry that connects a name to a new-style internet address.
- ABNF
Augmented Backus-Naur Form, a compact notation used in RFCs to define exactly which strings are valid for a text format or protocol. Specified in RFC 5234.
Like I'm five A strict recipe for what a correctly written line looks like.
Used in RFC 822 RFC 1137 RFC 1766 RFC 1869 RFC 2122 RFC 2193 RFC 2234 RFC 2254 RFC 2255 RFC 2342 RFC 2396 RFC 2445 RFC 2530 RFC 2569 RFC 2609 RFC 2614 RFC 2648 RFC 2653 RFC 2738 RFC 2812 RFC 2822 RFC 2846 RFC 2849 RFC 2910 and 220 more
- Abstract Syntax
The logical definition of data, typically expressed in ASN.1 for OSI protocols. It describes the structure and meaning of the data independent of how it is transmitted.
Like I'm five The idea of what you are sending, like 'a person's name and age'.
- Abstract Syntax Notation One (ASN.1)
A formal language for defining data structures and message formats in a machine-readable, platform-independent way.
Like I'm five A standard way of writing down the structure of data so computers can understand and process it correctly.
- Abuse Reporting Format (ARF)
A message format for reporting abuse in the messaging infrastructure, designed so that reports can be generated and read automatically.
Like I'm five A standard form for telling someone about a problem with their mail, so computers can fill it in and read it.
- Access Category
One of four Wi-Fi priority classes for traffic: Voice, Video, Best-Effort and Background. Higher categories get quicker access to the radio channel.
Like I'm five Four lanes on a road, with the voice lane being the fastest.
- Access Concentrator
The server-side device in PPPoE that answers a host's discovery request and terminates its PPP session. A host may be able to reach more than one.
Like I'm five The provider's box that answers your computer and handles your login.
- Access Control
Mechanisms and policies that determine who is allowed to use a system or access specific data and resources, and who is not.
Like I'm five Rules about who is allowed to use what.
- Access control entry
One line of an access control list. It names a principal and a set of privileges that are either granted or denied to that principal.
Like I'm five One line on the guest list: a name and what that person may or may not do.
- Access control list
A list of identity and rights pairs attached to an object. It decides which users may read, change or administer that object.
Like I'm five A sign on a door that says who is allowed in and what they may do.
Used in RFC 2244 RFC 2820 RFC 3744 RFC 4314 RFC 4768 RFC 8076 RFC 8519 RFC 8520 RFC 8783 RFC 9133 RFC 9631 RFC 9899 RFC 10065
- Access Controller
The central device in a CAPWAP network that manages configuration, policy, and security for a group of wireless access points.
Like I'm five The central manager that controls all the access points.
Used in RFC 5413 RFC 5414 RFC 5415 RFC 5416 RFC 5833 RFC 5834 RFC 7494
- Access Node
Network equipment, usually at a central office or street cabinet, that terminates subscribers' access lines. For DSL lines it is called a DSLAM.
Like I'm five The box in the street cabinet where the phone lines from many homes come together.
- Access Point Name (APN)
In 3GPP networks, a logical name that a mobile device connects to. It maps to a gateway and says what services and IP connectivity (IPv4, IPv6 or IPv4v6) the device may use.
Like I'm five The name of the door your phone uses to get onto the network.
- Access Router
The router that directly serves a mobile node when connected to a network, providing IP connectivity and network services.
Like I'm five The Wi-Fi router or base station your phone talks to directly.
- Access token
In OAuth, a string issued by an authorization server that stands for permission granted to a client. The client presents it to a resource server instead of using the owner's password.
Like I'm five A pass you are given so you can use something without telling the secret password.
Used in RFC 2179 RFC 6749 RFC 6750 RFC 6819 RFC 7009 RFC 7521 RFC 7522 RFC 7523 RFC 7591 RFC 7628 RFC 7635 RFC 7636 RFC 7662 RFC 8252 RFC 8471 RFC 8495 RFC 8628 RFC 8693 RFC 8705 RFC 8707 RFC 8898 RFC 8959 RFC 9068 RFC 9200 and 22 more
- Access Unit
In MPEG, the smallest piece of a stream that has its own timing information. An audio frame or a video picture is an example.
Like I'm five One small piece of a song or video, like a single frame of a cartoon.
- Access-Challenge
A RADIUS reply that says the server needs more proof, such as a one-time code. The client prompts the user and sends a new Access-Request with the answer and the State attribute.
Like I'm five The office says "not yet, ask them this secret question first".
- ACE label
ASCII Compatible Encoding label. An ASCII-only domain label that begins with a special prefix and whose remainder is the Punycode form of a Unicode string.
Like I'm five A plain-letter version of a fancy-letter name, marked with a special beginning.
Used in RFC 3490 RFC 3491 RFC 3492 RFC 5890 RFC 5891 RFC 5893 RFC 5894 RFC 6055 RFC 9233 RFC 9549
- Ack Vector
A DCCP option that gives a run-length encoded history of which packets were received, received with an ECN mark, or not yet received. It lets a sender see exactly what was lost.
Like I'm five A short list that says which packets arrived and which did not.
- ACME
The Automated Certificate Management Environment, a protocol in which a client talks to a certificate authority's server to request and manage certificates automatically.
Like I'm five A way for computers to ask for and renew their ID cards without a person doing it.
- ACME challenge
A test a certificate authority sets so that an applicant can prove control of a domain name, such as http-01 or dns-01.
Like I'm five A small test only the real owner of a name could pass.
Used in RFC 8555 RFC 8657 RFC 8737 RFC 8738 RFC 8739 RFC 9060 RFC 9444 RFC 9447 RFC 9448 RFC 9799 RFC 9891
- Active measurement
A way of measuring a network by sending synthetic test traffic through it and observing what happens, rather than watching real user traffic.
Like I'm five Sending your own test packages through the mail to see how fast delivery is, instead of watching other people's mail.
- Active Queue Management
Techniques used by network devices to manage queue sizes and signal congestion early, before buffers overflow.
Like I'm five A method routers use to manage crowding before the queue gets full.
Used in RFC 2309 RFC 2481 RFC 3168 RFC 3289 RFC 3819 RFC 6077 RFC 7141 RFC 7567 RFC 8034 RFC 8087 RFC 8289 RFC 8311 RFC 9330 RFC 9331 RFC 9332 RFC 9599 RFC 9600 RFC 9743
- AD bit
Authentic Data. A DNS header bit set by a name server in a response to say that it considers all RRsets in the Answer and Authority sections authentic. It is only meaningful over a trusted channel.
Like I'm five A sticker on the envelope saying "already checked."
- Adaptation Layer
The protocol layer that sits between the convergence layer and individual network paths, handling encapsulation or security for each path.
Like I'm five The translator that talks to each network path in its own language.
- Adaptive Differential Pulse Code Modulation
An audio compression algorithm that reduces the data rate of a 64 kilobit-per-second PCM audio stream to 32 kilobits per second by encoding the differences between successive samples and adapting the quantization step.
Like I'm five A way to squeeze audio data to half its size without losing quality.
- Additional authenticated data
Data that is covered by an authentication tag but is not encrypted and is not part of the output, such as a packet header that must stay readable.
Like I'm five The address on an envelope: anyone can read it, but you can still tell if someone changed it.
- Address Aggregation
Grouping addresses with common prefixes into a single routing entry so routers can forward many addresses with one rule.
Like I'm five Grouping all mail for a city into one delivery region instead of handling each street separately.
Used in RFC 1287 RFC 1366 RFC 1454 RFC 1518 RFC 1887 RFC 2374 RFC 4852
- Address Class
In classful addressing, one of five predefined categories (A, B, C, D, E) that determined how many bits identified the network versus the local host. Class A provided the most host addresses, Class C the fewest.
Like I'm five A category that determined whether you got a huge network, a medium one, or a small one.
- Address family
A kind of network address, such as IPv4 or IPv6. A system may support one family or several.
Like I'm five The type of address, like a street address versus a phone number.
- Address Family Identifier
A numeric code used by BGP to identify the type of routing information being carried, such as IPv4 (1) or IPv6 (2).
Like I'm five A label that tells a router what kind of address a message is about.
- Address of Record
A SIP address that identifies a user, such as a SIP, SIPS or tel URI. A participant may have more than one.
Like I'm five The permanent address people use to reach you.
Used in RFC 3680 RFC 3764 RFC 4596 RFC 5627 RFC 7315 RFC 7865 RFC 7904 RFC 8224
- Address plus Port (A+P)
An approach to the IPv4 address shortage in which several hosts use the same IPv4 address and are told apart by non-overlapping sets of transport-layer ports.
Like I'm five Sharing one street address but each family uses its own range of door numbers.
- Address selection policy table
A table of prefixes, each with a precedence and a label, that an IPv6 host uses to choose among several source and destination addresses. RFC 6724 defines its default contents.
Like I'm five A scorecard that tells a computer which of its addresses to prefer.
- Adjacency
A relationship between two neighboring routers in an IS-IS network. An adjacency in the UP state means the neighbors are actively exchanging routing information.
Like I'm five A working connection between two routers that are neighbors on the same link.
Used in RFC 1247 RFC 1583 RFC 2178 RFC 3847 RFC 4444 RFC 5303 RFC 7177
- Administration Management Domain
In X.400, a network administered by a public service provider or large organization, identified as part of an X.400 O/R name.
Like I'm five A section of an X.400 address representing the email service provider.
- Administrative Domain
A network or set of networks operated and controlled by a single organization or authority.
Like I'm five One company's or provider's network that they manage themselves.
Used in RFC 1125 RFC 1136 RFC 1478 RFC 1479 RFC 3340 RFC 4375 RFC 8190
- Administrative group
A link attribute, also called a color, that is a bitmask used in traffic engineering. A set bit marks the link as belonging to the corresponding group.
Like I'm five A colored sticker on a road that tells the planner which roads to use or avoid.
- Administrative Management Domain
An organization or operator that is responsible for a part of the Internet mail system, and so for the domain names it uses. Also called an ADMD.
Like I'm five The people in charge of a set of mail servers and the names they use.
- Administrative scope
A boundary defined by network administrators that limits the reach of multicast traffic. Each scope has its own set of multicast addresses.
Like I'm five A boundary set by network administrators that keeps multicast traffic within a certain area, like a building or a company.
- Admission control
A check that decides whether a link has enough spare capacity to accept a new reservation, and refuses it if not.
Like I'm five Letting someone in only if there is still room.
Used in RFC 1633 RFC 2205 RFC 2211 RFC 2212 RFC 2688 RFC 2751 RFC 2814 RFC 2998 RFC 3175 RFC 3181 RFC 5127 RFC 5559 RFC 5974 RFC 6016 RFC 7256
- ADSL
Asymmetric Digital Subscriber Loop: a technology for carrying data over a telephone line, with a modem (ATU-C) at the central end and another (ATU-R) at the remote end.
Like I'm five A way to send internet over an ordinary phone wire.
- AEAD
Authenticated Encryption with Associated Data. A cipher mode that encrypts data and checks that it has not been changed in one step. All ciphers in TLS 1.3 are AEAD ciphers.
Like I'm five A sealed envelope that also shows if anyone has tampered with it.
Used in RFC 3610 RFC 4106 RFC 4253 RFC 4309 RFC 5083 RFC 5084 RFC 5116 RFC 5282 RFC 5288 RFC 5289 RFC 5487 RFC 5647 RFC 5669 RFC 6054 RFC 6209 RFC 6367 RFC 6460 RFC 6655 RFC 7165 RFC 7251 RFC 7253 RFC 7366 RFC 7457 RFC 7516 and 64 more
- AES
Advanced Encryption Standard, a symmetric encryption algorithm that scrambles data using a secret key. The key can be 128, 192, or 256 bits long.
Like I'm five A recipe for scrambling messages with a secret code key.
- AES counter mode
A way to use the AES block cipher as a stream cipher by encrypting successive counter values and XORing the result onto the data.
Like I'm five Using a lock to make a long random scribble, then mixing it with the message.
Used in RFC 3268 RFC 3610 RFC 3686 RFC 3711 RFC 3723 RFC 3830 RFC 4106 RFC 4305 RFC 4309 RFC 4344 RFC 4543 RFC 4656 RFC 4763 RFC 5083 RFC 5084 RFC 5116 RFC 5297 RFC 5529 RFC 5669 RFC 5930 RFC 6054 RFC 6188 RFC 6239 RFC 6786 and 7 more
- AES-GCM
Advanced Encryption Standard in Galois/Counter Mode; an encryption and authentication algorithm that both encrypts data and proves it has not been tampered with.
Like I'm five An encryption lock that also checks if someone tried to trick you by changing the message.
- AFTR
The Address Family Transition Router is the provider-side end of a Dual-Stack Lite IPv4-over-IPv6 tunnel. Customer equipment connects to it by name.
Like I'm five The helper at the provider's end that passes old-style traffic along for you.
- Alarm Indication Signal
A message sent downstream when a server layer fault is detected. It lets the layers above suppress their own alarms.
Like I'm five A message saying the trouble is further up the line, so you need not sound your own alarm.
- ALG (Application Level Gateway)
A helper on a NAT device that inspects and rewrites application payloads, such as FTP PORT commands, that carry IP addresses or ports inside the data.
Like I'm five A translator who also fixes addresses written inside the letter, not just on the envelope.
Used in RFC 2663 RFC 2993 RFC 3022 RFC 3234 RFC 3235 RFC 3424 RFC 4787 RFC 4924 RFC 4961 RFC 4966 RFC 5382 RFC 5597 RFC 6144 RFC 6269 RFC 6384 RFC 8725 RFC 8839 RFC 9864
- alg none
The
nonevalue of thealgheader, which makes an Unsecured JWT with no signature. Implementations must support it, but a verifier that accepts it when a signature was expected can be fooled by forged tokens.Like I'm five A note that says "no stamp needed", which is dangerous if you were expecting a stamp.
- Algorithm agility
The ability of a protocol to name the algorithm it uses, so that an algorithm can be replaced without redesigning the format.
Like I'm five Building a toolbox with a label on each tool, so you can swap one for a better one later.
- Algorithm substitution attack
An attack in which the attacker changes the algorithm, or its parameters, used in a signed or authenticated message so that verification gives a different result.
Like I'm five A cheater swaps the checking method for a weaker one that is easier to fool.
- ALPN
Application-Layer Protocol Negotiation, a TLS extension in which client and server agree on which protocol to speak inside the connection. HTTP/2 over TLS uses the identifier
h2.Like I'm five Picking which language to talk in while you are still shaking hands.
Used in RFC 7301 RFC 7443 RFC 7639 RFC 7838 RFC 8323 RFC 8447 RFC 8701 RFC 8737 RFC 8738 RFC 8744 RFC 8833 RFC 8915 RFC 9000 RFC 9001 RFC 9103 RFC 9112 RFC 9113 RFC 9114 RFC 9209 RFC 9250 RFC 9289 RFC 9325 RFC 9368 RFC 9369 and 10 more
- Alt-Svc
The Alternative Services mechanism, through which a server tells a client in an Alt-Svc header field or an HTTP/2 ALTSVC frame that the same service is also reachable another way. HTTP/3 uses the token h3, as in
Alt-Svc: h3=":443".Like I'm five A sign that says "you can also reach us through this other door."
Used in RFC 7838 RFC 8030 RFC 8336 RFC 9114 RFC 9369 RFC 9460 RFC 9848
- Alternate Marking
A passive measurement method that marks consecutive batches of packets so that packet loss, latency and jitter can be measured on live traffic.
Like I'm five Changing the color of a sticker on parcels every so often so helpers can count how many went missing.
Used in RFC 8889 RFC 9341 RFC 9342 RFC 9343 RFC 9779 RFC 9947
- Alternative Network Address Types (ANAT)
An SDP grouping semantic that lets a media stream offer multiple network addresses of different types (such as IPv4 and IPv6) as alternatives, with a preference order.
Like I'm five A way to say 'here are a few different ways to reach me', listed in order of preference.
- ALTO
Application-Layer Traffic Optimization; a protocol that helps applications choose which servers to use based on network topology and costs.
Like I'm five A system that tells programs which server is closest or cheapest to use.
Used in RFC 5693 RFC 7971 RFC 8189 RFC 8686 RFC 8896 RFC 9240 RFC 9439
Authority that is attached to a request automatically instead of being named in it. Cookies are an example: the browser adds them to every matching request, which is why cross-site request forgery works.
Like I'm five A key that is always in your pocket and gets used even when someone else tells you which door to open.
- Amplification attack
An attack in which a server turns one incoming request into many outgoing ones, so a single cheap message can flood a victim with much more traffic.
Like I'm five Like shouting into a megaphone that repeats you a hundred times at someone else.
- Ancillary Data
Data in an MPLS packet that goes with a Network Action. It may be input to the action or the result of it, and it can sit in the label stack or after it.
Like I'm five A little note attached to a package with the details for the special job.
- Anderson-Darling K-sample test
A statistical test that checks whether several samples of measurements plausibly come from the same underlying distribution. RFC 6808 uses it to compare delay results from different tools.
Like I'm five A way to check whether two piles of numbers look like they came from the same machine.
- Anonymity set
The group of servers whose externally visible TLS behavior is the same, so that a connection to one cannot be told apart from a connection to another. In ECH, the set is the names served under the same client-facing server and configuration.
Like I'm five A crowd of people all wearing the same hat, so you can't tell which one you are looking at.
Used in RFC 3693 RFC 6462 RFC 6973 RFC 7619 RFC 7937 RFC 8280 RFC 8932 RFC 9458 RFC 9576 RFC 9620 RFC 9848 RFC 9849
- Anonymous FTP
A way of offering files for public download over ftp, where visitors log in without an account of their own, so that anyone can fetch the files.
Like I'm five A public shelf of files that anyone may borrow from without a library card.
- Anti-clogging token
An unpredictable value sent by a server that the other side must send back. It shows the sender is an active participant and not part of a flooding attack.
Like I'm five A ticket you must hand back to prove you are really there.
- Any-Source Multicast
The classic multicast mode in which a receiver joins a group address G and receives traffic sent to that group by any source.
Like I'm five Tuning in to a channel and hearing whoever talks on it.
- Anycast
An address shared by a set of interfaces, usually on different nodes. A packet sent to it is delivered to the nearest one, as measured by routing.
Like I'm five Calling a help line and being connected to whichever agent is closest to you.
Used in RFC 1546 RFC 1621 RFC 1884 RFC 1888 RFC 2101 RFC 2373 RFC 2460 RFC 2501 RFC 2526 RFC 2775 RFC 2780 RFC 3068 RFC 3258 RFC 3446 RFC 3484 RFC 3513 RFC 3568 RFC 3618 RFC 3627 RFC 3775 RFC 3879 RFC 3956 RFC 3964 RFC 4007 and 84 more
- APOP
An optional POP3 login command. The client sends an MD5 digest of the server's one-time timestamp plus a shared secret instead of the password itself.
Like I'm five Showing the result of mixing your secret with today's number, instead of saying the secret out loud.
Used in RFC 1460 RFC 1725 RFC 1939 RFC 1957 RFC 2195 RFC 2384 RFC 2449 RFC 3206 RFC 6856
- AppleTalk
A protocol suite with an open peer-to-peer architecture that runs over a variety of transmission media. It can interoperate with the IP protocol suite through encapsulation.
Like I'm five Apple's old way for computers and printers to talk to each other.
- Application Data Unit (ADU)
A piece of data that can be processed out of order with respect to other pieces. It is the smallest unit of error recovery in an ALF design.
Like I'm five A piece of a story that still makes sense even if you never got the pieces before it.
- Application layer gateway
An intermediary that relays a particular application protocol, such as e-mail or FTP, between a private network and the outside, so that private hosts get the service without having IP connectivity to outside hosts.
Like I'm five A helper at the door who passes messages in and out for people who may not leave the building.
Used in RFC 1415 RFC 1530 RFC 1918 RFC 2101 RFC 2588 RFC 2775 RFC 2871 RFC 3027 RFC 3102 RFC 3103 RFC 3303 RFC 3665 RFC 3715 RFC 4028 RFC 4838 RFC 6875 RFC 7092 RFC 9944
- Application Server
A functional entity that hosts one or more communication application instances. It terminates SIP signaling from user agents and controls media servers to deliver services such as IVR or conferencing.
Like I'm five The computer that decides what should happen and tells the media server what to do.
- Application Server Process
A single process instance of an Application Server, for example a primary or backup controller. An Application Server is modeled at the gateway as an ordered list of these processes.
Like I'm five One worker on a team, where the team shares a single job.
- Application-limited
Describes a sender that sends less than the congestion or receiver window allows because the application has no more data ready. The RFC calls such senders rate-limited.
Like I'm five You are not going slow because the road is jammed, but because you have nothing more to carry.
- application/dns-message
The media type for a single DNS message in the RFC 1035 on-the-wire format, up to 65535 bytes, used as the body of DoH requests and responses.
Like I'm five The label on the envelope that says a DNS letter is inside.
Used in RFC 2540 RFC 2671 RFC 2931 RFC 3226 RFC 3597 RFC 4343 RFC 5936 RFC 6762 RFC 6895 RFC 7766 RFC 8467 RFC 8484 RFC 8618 RFC 9267 RFC 9619 RFC 9953
- APPN (Advanced Peer-to-Peer Networking)
An evolution of SNA that allows dynamic routing and peer-to-peer communication without a central hub, bringing more flexibility to SNA networks.
Like I'm five A way to make SNA networks smarter so any node can talk to any other node.
- Appointed Forwarder
In TRILL, the switch on a multi-access link that handles native frames for a given VLAN. It is chosen so that at most one switch does this per VLAN.
Like I'm five The one helper picked to handle one group of kids at the door.
- April Fools' RFC
A humorous RFC published on 1 April, a long-running tradition in the series. RFC 2324 and RFC 2325 are examples. They are written in the formal style of real specifications.
Like I'm five A joke rulebook that is published on April 1st.
Used in RFC 748 RFC 1097 RFC 1217 RFC 1924 RFC 1926 RFC 2100 RFC 2134 RFC 2321 RFC 2322 RFC 2324 RFC 2549 RFC 2795 RFC 3251 RFC 3252 RFC 4041 RFC 5241 RFC 5242 RFC 5513 RFC 6214 RFC 6217 RFC 7168 RFC 7169 RFC 7511 RFC 8136 and 8 more
- Area Border Router (ABR)
An OSPF router attached to more than one area, which summarizes routing information between them.
Like I'm five A gatekeeper standing between two districts.
Used in RFC 1131 RFC 1247 RFC 1253 RFC 1583 RFC 1584 RFC 1793 RFC 2178 RFC 2328 RFC 2740 RFC 3101 RFC 3509 RFC 4098 RFC 4105 RFC 4561 RFC 4577 RFC 4674 RFC 4920 RFC 5088 RFC 5130 RFC 5152 RFC 5185 RFC 5250 RFC 5283 RFC 5302 and 29 more
- Area Director
An IETF leader who oversees the working groups in one technical area and sits on the IESG. Area Directors are selected by the NomCom.
Like I'm five A leader who looks after several related clubs and helps run the whole organization.
- Area Leader
The elected representative router within a Level 1 area that generates and originates the proxy LSP on behalf of the entire area.
Like I'm five The one router in a region that is chosen to speak for the whole region.
- ARP
The Address Resolution Protocol. A host uses it to find the hardware address that goes with an IP address on the same network. RARP is its inverse.
Like I'm five Asking the room "who has this address?" so you know whose name tag to look for.
Used in RFC 824 RFC 826 RFC 828 RFC 831 RFC 891 RFC 893 RFC 894 RFC 903 RFC 906 RFC 917 RFC 919 RFC 922 RFC 925 RFC 948 RFC 961 RFC 985 RFC 990 RFC 1009 RFC 1027 RFC 1029 RFC 1042 RFC 1044 RFC 1051 RFC 1060 and 100 more
- ARP cache
The table in which a host stores the protocol-address to hardware-address pairings it has learned, so it does not have to broadcast a request for every packet.
Like I'm five A notebook of who sits where, so you only shout the question once.
Used in RFC 826 RFC 925 RFC 1329 RFC 1868 RFC 2176 RFC 2320 RFC 2390 RFC 2834 RFC 2835 RFC 4436 RFC 5227 RFC 8302 RFC 8344
- ARP spoofing
An attack in which a host sends forged ARP replies so that others store the wrong hardware address for an IP address, which can redirect traffic through the attacker. ARP has no authentication, so networks add protections such as Dynamic ARP Inspection.
Like I'm five A trickster who answers 'that's me!' when the name was not theirs, so the mail goes to them.
Used in RFC 826 RFC 2225 RFC 2390 RFC 2834 RFC 4036 RFC 4436 RFC 4732 RFC 6747 RFC 6941 RFC 6959 RFC 7039 RFC 7384 RFC 7454 RFC 7513 RFC 8171 RFC 8302 RFC 9047 RFC 9161
- ARPANET
The Advanced Research Projects Agency Network, the predecessor to the modern Internet, operational from 1969 to 1989.
Like I'm five The first big computer network that became the internet.
Used in RFC 63 RFC 78 RFC 151 RFC 281 RFC 283 RFC 306 RFC 333 RFC 342 RFC 344 RFC 353 RFC 362 RFC 366 RFC 439 RFC 441 RFC 443 RFC 604 RFC 608 RFC 846 RFC 851 RFC 1000 RFC 2555
- AS_PATH
The BGP path attribute listing the autonomous systems a route has traversed, as AS_SEQUENCE and AS_SET segments. A speaker adds its own AS number when it advertises a route to an external peer, and a router rejects a route whose AS_PATH already contains its own AS.
Like I'm five The list of countries a message crossed on its way here.
Used in RFC 1105 RFC 1164 RFC 1265 RFC 1267 RFC 1364 RFC 1772 RFC 1774 RFC 1965 RFC 2280 RFC 2439 RFC 2622 RFC 3065 RFC 3345 RFC 4271 RFC 4272 RFC 4760 RFC 4786 RFC 4893 RFC 5065 RFC 5575 RFC 6382 RFC 6396 RFC 6483 RFC 6793 and 15 more
- AS112
A loosely coordinated project that runs servers to answer reverse DNS queries for private-use IPv4 addresses. It keeps those junk queries away from the rest of the reverse DNS.
Like I'm five A set of helper desks that answer questions nobody else should be asked.
- ASCII armor
OpenPGP's printable encoding of binary data, made of base64 text plus a 24-bit CRC checksum, so that it survives channels that only carry text.
Like I'm five Dressing up secret bytes in plain letters so they can travel safely in an email.
- ASN.1
Abstract Syntax Notation One, a language for describing the structure of data independently of how it is written as bytes. Encoding rules such as BER and DER turn ASN.1 values into octets.
Like I'm five A way of drawing the shape of a form so everyone fills it in the same way.
Used in RFC 1014 RFC 1021 RFC 1022 RFC 1023 RFC 1024 RFC 1052 RFC 1065 RFC 1066 RFC 1076 RFC 1155 RFC 1156 RFC 1157 RFC 1189 RFC 1208 RFC 1212 RFC 1213 RFC 1214 RFC 1227 RFC 1229 RFC 1230 RFC 1231 RFC 1232 RFC 1233 RFC 1238 and 313 more
- Associated channel
A side channel that runs inside a pseudowire alongside the user data. It carries control and management messages, marked by a header whose first nibble is 0001b.
Like I'm five A small lane next to the main road for messages about the road itself.
- Association
SCTP's name for a connection between two endpoints. Unlike a TCP connection, it can span several IP addresses on each side and carry many streams.
Like I'm five The whole friendship between two computers, including every road and lane between them.
Used in RFC 700 RFC 2788 RFC 2960 RFC 3057 RFC 3257 RFC 3868 RFC 3873 RFC 4165 RFC 4895 RFC 4960 RFC 5043 RFC 5061 RFC 5203 RFC 5907 RFC 6458 RFC 6525 RFC 6526 RFC 6780 RFC 7551 RFC 8261 RFC 8303 RFC 8537 RFC 8540 RFC 8697 and 7 more
- Assurance graph
A set of subservices linked by dependencies that together represent what a service relies on. Agents report a health status and symptoms for each node in it.
Like I'm five A family tree of the parts a service needs, with a health mark on each part.
- Asynchronous Transfer Mode (ATM)
A switched network technology that transmits data in fixed-size cells and supports dynamic connection establishment with quality-of-service guarantees.
Like I'm five A network technology that lets you set up direct lines on demand with guaranteed performance.
Used in RFC 1937 RFC 2380 RFC 2381 RFC 2383 RFC 2417 RFC 2443 RFC 2520 RFC 2761 RFC 3033 RFC 3336 RFC 3337
- ATMARP
The ARP protocol extended to work over ATM, where a server maps IP addresses to ATM addresses. Its companion InATMARP asks the other end of a connection for its addresses.
Like I'm five A phone book for finding the ATM address that goes with an Internet address.
- Atom Feed
An XML document in the Atom Syndication Format that lists related items, called Entries. New and updated Entries come first, so clients can fetch just what changed.
Like I'm five A list of cards in a box, with the newest card on top.
- Atomic operation
An operation that reads, changes and writes a value as one indivisible step, so no other access can slip in between. Examples are fetch-and-add and compare-and-swap.
Like I'm five A change that happens all at once, so nobody can interrupt it halfway.
- Attachment Circuit
The Layer 2 link that connects a customer edge device to a provider edge device in a Layer 2 VPN.
Like I'm five The cable from your house to the provider's building.
Used in RFC 3916 RFC 3985 RFC 4448 RFC 4664 RFC 5085 RFC 5641 RFC 6073 RFC 6074 RFC 6310 RFC 6575 RFC 6870 RFC 7023 RFC 7387 RFC 8184 RFC 9744 RFC 9833 RFC 9834 RFC 9835 RFC 9836
- Attribute Certificate
A digitally signed structure that binds authorization information such as group membership, role, or clearance to an identity, without including a public key.
Like I'm five A certificate that says what you are allowed to do instead of who you are.
- Attribute fidelity
A client choice in IPP between printing a job exactly as requested or rejecting it, and letting the printer ignore or substitute unsupported settings so the job still prints.
Like I'm five Telling the printer either, do it exactly my way or not at all, or, just do your best.
- Attribute type
The name and type of a field in an LDAP entry, such as 'givenName', 'mail', or 'description'.
Like I'm five The name of a piece of information, like 'name' or 'email address'.
- Attribute Value Pair
A unit of data in Diameter made of a code that names the attribute and a value. Messages are built from a list of them.
Like I'm five A labeled box with one piece of information inside.
Used in RFC 2924 RFC 3931 RFC 4740 RFC 5191 RFC 5447 RFC 5777 RFC 5866 RFC 5872 RFC 6733 RFC 7156 RFC 7683 RFC 8583
- Attribute-Value Pair (AVP)
The basic unit of data in a Diameter message: a code, a type and a value. A grouped AVP contains other AVPs inside it.
Like I'm five A labeled slot in a form, with the label on the left and the answer on the right.
Used in RFC 2661 RFC 3308 RFC 3573 RFC 4072 RFC 5778 RFC 5779 RFC 6734 RFC 6735 RFC 7155 RFC 7423 RFC 7886 RFC 7944 RFC 7966 RFC 8506 RFC 9390
- Augmented PAKE
A password-authenticated key exchange protocol where the server stores a verifier (a derived value like g^password mod p) rather than the password itself, providing security even if the verifier is compromised.
Like I'm five The server keeps a scrambled version of your password instead of the password itself, so even if stolen, the thief cannot easily figure out the original password.
- Authenticated denial of existence
A signed proof that a name or record type does not exist, built in DNSSEC from NSEC records. It stops attackers from forging negative answers.
Like I'm five A sealed note proving there is no such page.
Used in RFC 2065 RFC 2535 RFC 3833 RFC 4035 RFC 4470 RFC 5155 RFC 6605 RFC 6840 RFC 8976 RFC 9276 RFC 9824
- Authenticated Encryption (AE)
An encryption algorithm that provides both confidentiality and authentication of the encrypted data, verifying that it has not been modified.
Like I'm five Encryption that also proves the message wasn't changed on the way.
- Authentication Domain Name
A domain name that a DNS client uses to authenticate a DNS resolver, by comparing it with the name in the resolver's certificate.
Like I'm five The name on a helper's ID badge that you check before you trust them.
- Authentication Header
An IP extension header that carries a cryptographic signature (Authentication Data) computed over the datagram to prove its origin and detect modifications.
Like I'm five A special label added to a packet containing a tamper-proof signature that proves who sent it.
- Authentication method
A named way of proving identity to an SSH server, such as publickey, password or hostbased. The server lists which methods may continue, and the client chooses.
Like I'm five One of the ways the doorkeeper lets you prove who you are.
Used in RFC 471 RFC 501 RFC 1124 RFC 1225 RFC 1244 RFC 1246 RFC 1334 RFC 1339 RFC 1411 RFC 1412 RFC 1445 RFC 1492 RFC 1508 RFC 1509 RFC 1511 RFC 1616 RFC 1635 RFC 1636 RFC 1734 RFC 1751 RFC 1828 RFC 1831 RFC 1856 RFC 1910 and 107 more
- Authentication scheme
In HTTP authentication, a token such as Basic, Digest or Bearer that names the method used to produce credentials. A challenge and the matching Authorization header both begin with the scheme name.
Like I'm five The name of the kind of ID you are showing.
Used in RFC 912 RFC 1447 RFC 1813 RFC 1852 RFC 2203 RFC 2245 RFC 2264 RFC 2425 RFC 2520 RFC 2617 RFC 2839 RFC 3206 RFC 3567 RFC 3651 RFC 4169 RFC 4189 RFC 4190 RFC 4742 RFC 5310 RFC 6094 RFC 7235 RFC 7236 RFC 7410 RFC 7481 and 20 more
- Authentication tag
A short value appended to a ciphertext that lets the receiver check that the data and associated data were not altered. If the tag does not match, the message is rejected.
Like I'm five A tamper-proof sticker that breaks if anyone changes the message.
- Authenticator
A small record containing the client's name and a current timestamp, encrypted with the session key from a ticket. It proves the sender holds the key and that the request is fresh.
Like I'm five A note you write with the current time using the secret code, to show it is really you and it is right now.
Used in RFC 1305 RFC 1334 RFC 1510 RFC 1994 RFC 2107 RFC 2264 RFC 2284 RFC 2403 RFC 2620 RFC 2759 RFC 2866 RFC 2869 RFC 2942 RFC 3059 RFC 3543 RFC 3580 RFC 3748 RFC 4017 RFC 4072 RFC 4120 RFC 4121 RFC 4137 RFC 4187 RFC 4218 and 24 more
A DNS name server that holds the real data for a zone, as opposed to one repeating what it has cached.
Like I'm five The office that really keeps the list, not someone repeating it.
Used in RFC 882 RFC 883 RFC 1033 RFC 1536 RFC 1996 RFC 2181 RFC 2182 RFC 2308 RFC 2870 RFC 3258 RFC 3655 RFC 4035 RFC 4074 RFC 4470 RFC 5358 RFC 5452 RFC 5936 RFC 6147 RFC 6303 RFC 6563 RFC 6761 RFC 7534 RFC 7706 RFC 7719 and 24 more
The optional part of a URI that follows the two slashes after the scheme. It has the form
[userinfo@]host[:port]and names the server or registry that governs the rest of the URI.Like I'm five The part of the address that says who is in charge of the place you are going.
Used in RFC 1808 RFC 2396 RFC 2732 RFC 3981 RFC 3986 RFC 4088 RFC 4151 RFC 5122 RFC 5538 RFC 6270 RFC 6920 RFC 8089 RFC 8820
The process of determining what a user, service, or device is allowed to do, based on identity, role, group membership, time, or other attributes.
Like I'm five Deciding what someone is allowed to do.
A short-lived credential that the authorization server gives the client after the owner approves. The client exchanges it for an access token at the token endpoint, so the token itself never passes through the user's browser.
Like I'm five A claim ticket you swap at the desk for the real pass.
Used in RFC 2904 RFC 3867 RFC 5733 RFC 6749 RFC 6819 RFC 7636 RFC 8252 RFC 8707 RFC 9126 RFC 9207 RFC 9560 RFC 9700 RFC 10006 RFC 10017
The identity a client asks to act as after it has authenticated. It may differ from the authentication identity tied to its credentials.
Like I'm five Who you are allowed to act as, which can be different from who you proved you are.
A secret value, such as a password, attached to an EPP object that a client must present to prove it may query or transfer that object.
Like I'm five A secret password that proves a card really belongs to you.
In OAuth, the server that authenticates the resource owner, obtains their approval, and issues access tokens to the client.
Like I'm five The office that gives out passes.
Used in RFC 6749 RFC 6750 RFC 6819 RFC 7009 RFC 7521 RFC 7522 RFC 7523 RFC 7591 RFC 7635 RFC 7636 RFC 7662 RFC 8053 RFC 8252 RFC 8414 RFC 8628 RFC 8693 RFC 8705 RFC 8707 RFC 8898 RFC 9068 RFC 9101 RFC 9126 RFC 9200 RFC 9201 and 17 more
- Autoconfiguration
The ability of a network node to automatically determine and assign its own configuration parameters without manual intervention, using mechanisms like DHCP, SLAAC, or self-generation of addresses.
Like I'm five A computer figuring out its network settings by itself without someone typing in numbers.
- Automatic Multicast Tunneling
AMT, defined in RFC 7450, carries multicast traffic over a unicast tunnel between a relay and a gateway so that it can cross network segments that cannot forward multicast.
Like I'm five Wrapping a broadcast in a private package so it can travel through a place that cannot carry broadcasts.
- Automatic repeat request
A reliability method in which the receiver reports what it got and the sender resends whatever is missing. A retransmission timer protects the process when feedback is lost.
Like I'm five If you do not hear back that something arrived, you send it again.
- Autonomic Control Plane
A secure, self-managing control plane that provides a protected channel for communication between autonomic nodes. It is established through a bootstrap process and serves as the foundation for ASA communication.
Like I'm five A private, secure channel used by autonomic agents to talk to each other.
- Autonomic Service Agent
Software running on an autonomic node that implements a specific autonomic function, either independently or as part of a distributed function.
Like I'm five A smart program on a device that makes that device self-managing.
Used in RFC 7575 RFC 8316 RFC 8990 RFC 8991 RFC 8993 RFC 9222
- Autonomous system
A routing domain under one administration, identified by an AS number, that exchanges routes with other such domains using BGP.
Like I'm five A group of roads run by one road company.
Used in RFC 820 RFC 827 RFC 888 RFC 890 RFC 904 RFC 911 RFC 923 RFC 975 RFC 985 RFC 990 RFC 1009 RFC 1020 RFC 1058 RFC 1059 RFC 1062 RFC 1069 RFC 1092 RFC 1093 RFC 1104 RFC 1105 RFC 1117 RFC 1118 RFC 1125 RFC 1126 and 334 more
- Autonomous System Border Router
A router at the boundary of an autonomous system that peers with routers in other autonomous systems using EBGP.
Like I'm five A router at the edge of one network that talks to other networks.