E

The international standard for telephone numbering, administered by the ITU. It defines how country codes, area codes, and local numbers are structured.

Plain language The international standard for telephone numbering, administered by the ITU.

Used in RFC 3966 RFC 4725

An international public telephone number in the format defined by ITU Recommendation E.164. ENUM turns such numbers into domain names.

Plain language An international standard phone number format compatible worldwide.

Used in RFC 2916 RFC 3191 RFC 3192 RFC 3482 RFC 3761 RFC 3764 RFC 3824 RFC 3953 RFC 5503 RFC 6116 RFC 6461 RFC 8816

A telephone number in the international public numbering format defined by the ITU-T. ENUM writes it with a leading plus sign followed by digits.

Plain language A telephone number in the international public numbering format defined by ITU-T.

Used in RFC 982 RFC 3026 RFC 3761 RFC 4002 RFC 4238 RFC 4355 RFC 4414 RFC 4759 RFC 6116 RFC 7195

The Extensible Authentication Protocol. A framework for login methods such as passwords. IKEv2 can carry EAP messages to authenticate the initiator, alongside certificate-based authentication of the responder.

Plain language A standard framework for network authentication methods such as passwords.

Used in RFC 2284 RFC 2477 RFC 2607 RFC 2809 RFC 2869 RFC 2881 RFC 2989 RFC 3127 RFC 3169 RFC 3579 RFC 3580 RFC 3588 RFC 3748 RFC 3770 RFC 4016 RFC 4017 RFC 4058 RFC 4072 RFC 4137 RFC 4186 RFC 4187 RFC 4282 RFC 4284 RFC 4296 and 96 more

A SIP dialog created when a non-100 provisional response is sent to an initial dialog-initiating request. It stays in early state until a final response is sent.

Plain language A SIP session initiated when the server starts responding but before the call is answered or rejected.

Used in RFC 3311 RFC 3891 RFC 6228

Audio, video, or other media transmitted before a call is answered (before the called party sends a 200 OK response), such as ringing tones or announcements.

Plain language Audio, video or other content transmitted during a call setup before it is answered.

Used in RFC 3398 RFC 3666 RFC 3725 RFC 3959 RFC 3960 RFC 5009

Extended Binary Coded Decimal Interchange Code, a character encoding used on IBM systems that differs from ASCII.

Plain language A character encoding used on IBM systems that differs from the ASCII standard used elsewhere.

Used in RFC 183 RFC 452 RFC 466 RFC 1345 RFC 1576 RFC 4777

Elliptic Curve-based Certificateless Signatures for Identity-based Encryption. A digital signature scheme that works with identity-based keys and does not require certificates.

Plain language A digital signature method using identity-based keys instead of certificates.

Used in RFC 6509 RFC 7859

Elliptic Curve Diffie-Hellman with Ephemeral keys. Both sides use fresh elliptic curve key pairs for each exchange, so a later key leak does not expose past sessions.

Plain language Elliptic curve key agreement with fresh keys for each session to protect past sessions if keys leak.

Used in RFC 4492 RFC 5489 RFC 8422 RFC 9678

The Elliptic Curve Digital Signature Algorithm, a way to sign data with an elliptic curve private key so others can verify it with the public key.

Plain language A digital signature algorithm using elliptic curve mathematics that others can verify with the public key.

Used in RFC 3278 RFC 4050 RFC 4492 RFC 4754 RFC 5008 RFC 5430 RFC 5656 RFC 5754 RFC 5758 RFC 5759 RFC 6318 RFC 6380 RFC 6460 RFC 6637 RFC 7427 RFC 8247 RFC 8374 RFC 8422 RFC 8608 RFC 8624 RFC 8702 RFC 8725 RFC 8812 RFC 9966

ECN marking is the practice of setting the CE codepoint on an ECN-capable packet when a network device sees incipient congestion, instead of dropping the packet. The receiving endpoint reports the mark back to the sender, which then reduces its rate.

Plain language Writing a note on the packet that says the network is filling up, and passing the packet on.

Used in RFC 8087 RFC 8698 RFC 9599

A digital signature scheme from the EdDSA family, defined in RFC 8032, that uses 32-byte public keys and produces 64-byte signatures.

Plain language A digital signature scheme from RFC 8032 using 32-byte keys and producing 64-byte signatures.

Used in RFC 8037 RFC 8463 RFC 8624 RFC 9216 RFC 10049

The Edwards-curve Digital Signature Algorithm, a public-key signature scheme described in RFC 8032. It is used with curves such as Ed25519 and Ed448.

Plain language Edwards-curve Digital Signature Algorithm for signing data so recipients can verify authenticity.

Used in RFC 8037 RFC 8080 RFC 8410 RFC 8419 RFC 8422 RFC 8624

The Extension Mechanisms for DNS, version 0. A way to attach an OPT record to a DNS message to advertise UDP size, flags and options.

Plain language An extension mechanism for DNS that allows larger messages and extra options.

Used in RFC 6891 RFC 7314 RFC 8109 RFC 8499 RFC 8767 RFC 8906 RFC 9609

Extension Mechanisms for DNS. It allows larger DNS messages and carries extra flags such as the DO bit, which DNSSEC requires.

Plain language Extension Mechanisms for DNS version 0, enabling larger messages and extra flags like DNSSEC support.

Used in RFC 2671 RFC 2672 RFC 2673 RFC 3225 RFC 3226 RFC 3755 RFC 4033 RFC 4035 RFC 5001 RFC 5358 RFC 5395 RFC 5507 RFC 5625 RFC 5936 RFC 5966 RFC 6895 RFC 6975 RFC 7051 RFC 7720 RFC 7766 RFC 7828 RFC 7830 RFC 7871 RFC 7873 and 24 more

Exterior Gateway Protocol; a protocol for exchanging routing information between autonomous systems.

Used in RFC 890 RFC 1069 RFC 1118 RFC 1723

Using SIDs for BGP peers (PeerNode, PeerSet and Peer Adjacency SIDs) so that traffic can be steered out of a network through a chosen neighbor.

Plain language Using segment IDs for BGP neighbors to control which network exit a traffic flow uses.

Used in RFC 9086 RFC 9514

A LISP router at a receiving site that removes the outer header from encapsulated packets. In LISP multicast it also turns receivers' joins into joins toward the source site's ITR.

Used in RFC 6830 RFC 6831 RFC 6835 RFC 9299

A way for trading partners to exchange structured business transactions electronically, using agreed formats such as X12 or EDIFACT in place of paper documents.

Plain language Exchange of structured business transactions between computers using standard formats instead of paper.

Used in RFC 1767 RFC 2204 RFC 3335 RFC 4130 RFC 5402

Software that stores a person's billing, shipping and payment information and uses it to complete online forms automatically.

Plain language Software that stores payment and contact information for automatic form completion.

Used in RFC 3106 RFC 4112

A curve defined by an equation such as y^2 = x^3 + a*x + b. Its points can be added together, which gives a group used in public-key cryptography.

Plain language A mathematical curve defined by an equation like y^2 = x^3 + ax + b used in cryptography.

Used in RFC 4050 RFC 4754 RFC 5349 RFC 5639 RFC 5656 RFC 5832 RFC 6209 RFC 6380 RFC 6507 RFC 6508 RFC 6539 RFC 6932 RFC 6954 RFC 7027 RFC 7091 RFC 7664 RFC 7748 RFC 8121 RFC 8133 RFC 8731 RFC 8812 RFC 9140 RFC 9383 RFC 9385 and 1 more

A family of public-key cryptography methods based on elliptic curves. In TLS it is used for key exchange and digital signatures.

Plain language Public-key cryptography based on elliptic curve mathematics, used for key exchange and signatures.

Used in RFC 3279 RFC 3766 RFC 4492 RFC 4753 RFC 5289 RFC 5656 RFC 5753 RFC 5759 RFC 6090 RFC 6637 RFC 6954 RFC 7027 RFC 8422

A key agreement protocol based on elliptic curve mathematics where two parties each contribute a private key and derive a shared secret without transmitting it.

Plain language A key agreement protocol where two parties derive a shared secret using elliptic curve mathematics.

Used in RFC 3278 RFC 4492 RFC 5349 RFC 5656 RFC 6318 RFC 6380 RFC 6637 RFC 8037 RFC 8422

A set of points on an elliptic curve, together with a rule for combining points. Diffie-Hellman key exchange can be run in such a group instead of in modular exponentiation.

Plain language A set of points on an elliptic curve with operations that support key agreement protocols.

Used in RFC 4754 RFC 5114 RFC 5656 RFC 5903 RFC 6954

A domain name that owns no resource records itself but has subdomains that do. Such a name still exists.

Plain language A domain name with no resource records itself but with subdomains that do have records.

Used in RFC 4592 RFC 8020 RFC 9824

The Extended Master Session Key, a key derived by a key-generating EAP method alongside the MSK. It is reserved for deriving root keys and cannot leave the EAP server.

Plain language Extended Master Session Key derived by EAP methods for creating root keys, kept secure on the server.

Used in RFC 5749 RFC 6696 RFC 7029

Wrapping a complete network packet inside another packet to redirect it through a different path or network layer.

Plain language Wrapping a complete network packet inside another to redirect it through different networks.

Used in RFC 893 RFC 1022 RFC 1044 RFC 1088 RFC 1234 RFC 1241 RFC 1356 RFC 1454 RFC 1479 RFC 1702 RFC 1787 RFC 1853 RFC 1933 RFC 2003 RFC 2004 RFC 2157 RFC 2290 RFC 2334 RFC 2390 RFC 2473 RFC 2685 RFC 2784 RFC 2890 RFC 2895 and 25 more

A sequence of printable ASCII characters in a mail header that starts with =? and ends with ?=. It names a character set and an encoding and carries the text in encoded form.

Plain language A mail header sequence starting with =? and ending with ?= that carries text encoded in a specified character set.

Used in RFC 1522 RFC 2047 RFC 5825 RFC 6068 RFC 6532

The unit of data carried in a packet by a forward error correction scheme. It is either an original source symbol or a redundant repair symbol made from the source block.

Plain language A unit of data in a forward error correction stream, either original data or redundant repair data.

Used in RFC 5052 RFC 5053 RFC 5445 RFC 5775

A TLS extension, defined in RFC 9849, that encrypts the real ClientHello inside an outer ClientHello so that the server name and other fields are hidden from the network.

Plain language TLS extension that encrypts the outer ClientHello to hide the server name from network observers.

Used in RFC 9460 RFC 9761 RFC 9848 RFC 9849

The process of converting information into a form (ciphertext) that cannot be easily understood by unauthorized parties, using a mathematical algorithm and a key.

Plain language Converting information into ciphertext using a key so only authorized parties can read it.

Used in RFC 1022 RFC 1750 RFC 2040 RFC 2222 RFC 4422 RFC 5794 RFC 6562 RFC 7516 RFC 7568 RFC 7754 RFC 8164 RFC 8241

Short for encryption type in Kerberos. It names the cryptosystem used to protect a key or a message, such as the one used for a ticket session key.

Plain language The encryption method (such as AES) used to protect a key or message in Kerberos.

Used in RFC 4537 RFC 8429

Typically a device or service that holds a public-private key pair and manages a public key certificate for it. An identifier for the end entity is given as the subject of its certificate.

Used in RFC 8209 RFC 9483 RFC 9810 RFC 10004

A certificate that identifies the signer of a particular object rather than another certificate authority. In RPKI signed objects, one such certificate is embedded to validate the signature.

Plain language The certificate embedded in a signed object to validate the signature of the data.

Used in RFC 4945 RFC 6488

The argument that certain functions can only be performed correctly by the end systems themselves, so the network should just move datagrams and leave everything else to the fringes. It is described in Saltzer, Reed and Clark (1984) and cited in RFC 1958.

Plain language The design principle that network functions are best performed by endpoints rather than intermediate routers.

Used in RFC 817 RFC 1958 RFC 2316 RFC 2480 RFC 2775 RFC 2804 RFC 3102 RFC 3135 RFC 3155 RFC 3234 RFC 3238 RFC 3439 RFC 3724 RFC 3819 RFC 3837 RFC 3838 RFC 4189 RFC 4225 RFC 4924 RFC 6346 RFC 6574 RFC 8280 RFC 8557 RFC 8558 and 7 more

The ability for a packet to flow from any source to any destination with its contents and addressing unmodified by intermediate devices.

Plain language Ability for packets to flow from source to destination with contents and addressing unchanged.

Used in RFC 2956 RFC 5902

In LISP, an address that identifies an endpoint within a site. It is kept separate from the Routing Locators used on transit networks.

Plain language In LISP, an address identifying an endpoint's identity separate from its network location.

Used in RFC 6831 RFC 6833 RFC 6835 RFC 9301

A LISP identifier for an endpoint, used to say who it is rather than where it is attached to the network.

Plain language A LISP identifier for an endpoint that stays the same regardless of location.

Used in RFC 5558 RFC 5720 RFC 6830 RFC 7215 RFC 9300 RFC 9301 RFC 9303 RFC 10040

In LISP, the address that identifies what a computer is, its identity, independent of its location in the network.

Plain language The address that identifies what a computer is, independent of where it attaches to the network.

Used in RFC 1753 RFC 4838 RFC 5558 RFC 6139 RFC 6259 RFC 6260 RFC 6316 RFC 6830 RFC 6832 RFC 6836 RFC 6837 RFC 7834 RFC 7835 RFC 7954 RFC 7955 RFC 8060 RFC 8111 RFC 9299 RFC 9300 RFC 9735 RFC 9758 RFC 9962

A NAT behavior where an incoming packet is accepted for a mapping no matter who sent it. Some games and peer-to-peer applications need it to work through a NAT.

Used in RFC 6888 RFC 7857

A NAT behavior in which an internal address and port always get the same external address and port, no matter which external host they connect to.

Plain language NAT behavior where an internal address always maps to the same external address and port.

Used in RFC 4787 RFC 5128 RFC 5382 RFC 5597 RFC 7857

A device, or a component of a device, whose power use or energy use can be monitored or managed. It is identified by its physical index in the ENTITY-MIB.

Plain language A device or device component whose power consumption can be monitored or controlled.

Used in RFC 7460 RFC 7603

A node on an access network that applies filters to traffic from and to client devices. It lets only allowed traffic through until the client has been authorized.

Plain language A network device that filters traffic and blocks unauthorized access until the client is authenticated.

Used in RFC 4016 RFC 4058 RFC 5191 RFC 5193

A three-part code of the form class.subject.detail, such as 5.1.1, that gives a precise and translatable reason for the result of a mail operation.

Plain language A three-part code (like 5.1.1) that precisely identifies the reason for success or failure in mail operations.

Used in RFC 1894 RFC 2034 RFC 3463 RFC 3464 RFC 3886 RFC 5248 RFC 5429 RFC 6531

A 32-bit integer assigned by IANA that uniquely identifies an organization. Protocols use it to say whose vendor-specific data follows.

Plain language A 32-bit identifier assigned by IANA that uniquely identifies an organization for protocol use.

Used in RFC 1065 RFC 3925 RFC 7013 RFC 7470

A token, defined in RFC 9711, that carries claims about a device or other entity so that remote attestation messages can be conveyed in a standard format.

Plain language A standard token carrying claims about a device for remote attestation and verification.

Used in RFC 9782 RFC 9783

The content carried by an HTTP message, such as an HTML page. It follows the headers after a blank line and is described by entity headers like Content-Type and Content-Length.

Plain language The content of an HTTP message, such as a web page, following the headers.

Used in RFC 1945 RFC 2077

A measure of how unpredictable a secret value is, counted in bits. A value drawn evenly from 2^n possibilities has n bits, and an attacker must try about half of them. Min-entropy, which looks at the single most likely value, is the safest measure for security.

Plain language A measure of how unpredictable a value is, counted in bits.

Used in RFC 1750 RFC 2777 RFC 3211 RFC 3526 RFC 3562 RFC 3766 RFC 3797 RFC 4086 RFC 4467 RFC 4537 RFC 4552 RFC 4615 RFC 4738 RFC 5869 RFC 5959 RFC 6386 RFC 6391 RFC 7199 RFC 7447 RFC 7613 RFC 7636 RFC 8065 RFC 8086 RFC 8265 and 15 more

An extra MPLS label holding a hash of packet fields, computed once by the ingress router. Transit routers can use it for load-balancing without looking deeper into the packet.

Plain language An MPLS label holding a packet hash that allows load balancing without deep packet inspection.

Used in RFC 6790 RFC 7190 RFC 7325 RFC 8012 RFC 8372 RFC 8596 RFC 8662 RFC 9089

A buffer of bits that an operating system keeps for random numbers. New unpredictable events are strongly mixed in, random bytes are extracted by hashing it, and its state is often saved at shutdown and restored at start-up.

Plain language A buffer of random bits maintained by the operating system for generating unpredictable values.

Used in RFC 4086

The system that maps phone numbers (E.164 format) to internet addresses and other resources via DNS.

Plain language A system mapping phone numbers to Internet addresses and resources through DNS.

Used in RFC 3026 RFC 3372 RFC 3761 RFC 3764 RFC 3824 RFC 3953 RFC 4114 RFC 4238 RFC 4414 RFC 4415 RFC 4725 RFC 4759 RFC 4769 RFC 5067 RFC 5076 RFC 5333 RFC 5346 RFC 5483 RFC 6116 RFC 6118 RFC 7553

A registered label in the Services field of an ENUM NAPTR that says what kind of interaction the resulting URI supports, such as voice or sms.

Plain language A label in ENUM that identifies the service type the resulting URI supports, such as voice or SMS.

Used in RFC 3761 RFC 3762 RFC 3764 RFC 3953 RFC 4002 RFC 4143 RFC 4355 RFC 4415 RFC 4769 RFC 4969 RFC 4979 RFC 5028 RFC 5278 RFC 5333 RFC 5483 RFC 6116 RFC 6117 RFC 6118 RFC 6315 RFC 7553 RFC 7566

A CMS structure that encrypts message content for one or more recipients, providing confidentiality but not authentication or integrity without additional signatures.

Used in RFC 2633 RFC 3565 RFC 4108 RFC 4134 RFC 7193

A key pair generated for a single use and then discarded. Using one per message means a leaked long-term key does not reveal how that message key was made.

Plain language A key pair used for a single transaction then discarded to protect against compromise of long-term keys.

Used in RFC 2631 RFC 8037 RFC 8418 RFC 8731 RFC 9212 RFC 9528

A temporary port number picked for the lifetime of one connection or test, rather than a well-known port fixed in advance.

Plain language A temporary port number assigned for the duration of a single connection or test.

Used in RFC 6056 RFC 9109 RFC 9414 RFC 9946

Configuration or operational data that does not persist across a reboot or power cycle. A system cannot roll back to a previous ephemeral configuration state.

Plain language Configuration data that does not persist across a device restart.

Used in RFC 7921 RFC 8242

A generation or version of the group's shared secret. Each time someone joins or leaves, the group advances to a new epoch with a different secret.

Plain language A version of a group's shared secret; each time group membership changes a new epoch is created.

Used in RFC 4347 RFC 6019 RFC 6347 RFC 8877 RFC 9147 RFC 9420 RFC 9750

Routing that spreads traffic over several paths that have the same cost. It means a destination can have more than one primary next hop.

Plain language Routing that distributes traffic equally across several paths of the same cost.

Used in RFC 5640 RFC 6413 RFC 6754 RFC 6790 RFC 7174 RFC 7424 RFC 7431 RFC 7497 RFC 7510 RFC 7916 RFC 8012 RFC 8086 RFC 8279 RFC 8926 RFC 8939 RFC 8986 RFC 9098

Sharing traffic over several paths that are equally good, so that different packets between the same two points may take different routes.

Plain language Load balancing traffic across multiple equal-cost paths so packets from the same flow may take different routes.

Used in RFC 2642 RFC 2991 RFC 2992 RFC 4379 RFC 4385 RFC 4814 RFC 4928 RFC 6374 RFC 6391 RFC 6412 RFC 6437 RFC 6438 RFC 6576 RFC 6754 RFC 7325 RFC 7455 RFC 7490 RFC 7938 RFC 8372 RFC 8395 RFC 8469 RFC 8596 RFC 8611 RFC 8662 and 9 more

A code that turns k source symbols into n encoding symbols so that the original can be recovered even if some symbols are lost and the positions of the lost ones are known.

Plain language A coding scheme that creates redundant symbols from source data so the original recovers even if some symbols are lost.

Used in RFC 2887 RFC 3453 RFC 5510 RFC 6816 RFC 6865

A special short sequence of bytes that signals a change in how the bytes following it should be interpreted. In ISO-2022-JP, escape sequences switch between ASCII and Japanese character sets.

Plain language A special byte sequence signaling a change in how following bytes should be interpreted.

Used in RFC 1468 RFC 1922 RFC 2141 RFC 2253 RFC 4514 RFC 6868

Encapsulating Security Payload. The IPsec protocol that encrypts and authenticates packets. It is one of the two kinds of Child SA IKE sets up.

Plain language Encapsulating Security Payload, the IPsec protocol that encrypts and authenticates packets.

Used in RFC 1825 RFC 1826 RFC 1829 RFC 1851 RFC 2207 RFC 2356 RFC 2401 RFC 2402 RFC 2403 RFC 2404 RFC 2405 RFC 2406 RFC 2409 RFC 2410 RFC 2451 RFC 2473 RFC 2521 RFC 2522 RFC 2719 RFC 2857 RFC 2868 RFC 2890 RFC 2894 RFC 3015 and 111 more

A response header field holding an opaque validator for one version of a resource. Clients send it back in If-Match or If-None-Match to make a request conditional on the resource still being that version.

Plain language An opaque response header value identifying one version of a resource for conditional requests.

Used in RFC 2068 RFC 2227 RFC 2295 RFC 2617 RFC 3229 RFC 3903 RFC 4791 RFC 4825 RFC 4918 RFC 5023 RFC 5264 RFC 5789 RFC 5839 RFC 5874 RFC 5875 RFC 5989 RFC 6249 RFC 6352 RFC 6578 RFC 6638 RFC 7231 RFC 7232 RFC 7234 RFC 7252 and 17 more

A family of wired local-area network technologies. A frame carries a destination and source MAC address, an EtherType and the payload.

Plain language A family of wired local-area network technologies using MAC addressing.

Used in RFC 820 RFC 824 RFC 826 RFC 828 RFC 891 RFC 893 RFC 894 RFC 895 RFC 899 RFC 948 RFC 985 RFC 1027 RFC 1029 RFC 1042 RFC 1044 RFC 1054 RFC 1089 RFC 1112 RFC 1122 RFC 1180 RFC 1207 RFC 1220 RFC 1284 RFC 1340 and 162 more

The unit of data on an Ethernet: a destination address, a source address, a type field and a data field. RFC 894 puts one IP datagram in the data field and sets the type to 0x0800.

Plain language The unit of data on Ethernet, containing source and destination MAC addresses and the payload.

Used in RFC 893 RFC 894 RFC 895 RFC 1060 RFC 1516 RFC 1638 RFC 2020 RFC 2464 RFC 2516 RFC 2544 RFC 2665 RFC 2895 RFC 3252 RFC 3518 RFC 3635 RFC 3918 RFC 4188 RFC 4326 RFC 4448 RFC 4665 RFC 4719 RFC 4720 RFC 4762 RFC 4789 and 37 more

The set of links that connects one customer site to one or more provider edge devices in EVPN, identified by an Ethernet Segment Identifier.

Plain language The group of links connecting one customer site to provider edge devices in EVPN.

Used in RFC 7432 RFC 7623 RFC 8214 RFC 8365 RFC 9251 RFC 9291 RFC 9784 RFC 9785 RFC 9786

A way to carry Layer 2 Ethernet services across an IP/MPLS network, using BGP to distribute the MAC and service information that provider edges need.

Plain language BGP-based Layer 2 service that carries Ethernet traffic across IP/MPLS networks.

Used in RFC 7338 RFC 7734 RFC 8214 RFC 8365

A 16-bit field in an Ethernet frame that says which protocol is carried inside. IPv4 uses 0x0800, ARP uses 0x0806 and RARP uses 0x8035.

Plain language A 16-bit field in Ethernet frames identifying the protocol carried inside (such as IPv4).

Used in RFC 826 RFC 894 RFC 903 RFC 1188 RFC 1209 RFC 1294 RFC 1483 RFC 1700 RFC 1701 RFC 2067 RFC 2427 RFC 2464 RFC 2470 RFC 2516 RFC 2684 RFC 2734 RFC 2784 RFC 2834 RFC 2835 RFC 3032 RFC 3293 RFC 4023 RFC 4326 RFC 4392 and 25 more

A 64-bit Extended Unique Identifier specified by the IEEE for various layer-2 networks and IPv6 interface identifiers.

Plain language A 64-bit Extended Unique Identifier for layer-2 networks and IPv6 interface identifiers.

Used in RFC 2373 RFC 2374 RFC 2462 RFC 2464 RFC 2467 RFC 2497 RFC 3146 RFC 3513 RFC 4941 RFC 5342 RFC 5375 RFC 6775 RFC 7043 RFC 7421 RFC 8929 RFC 9039

A message that reports that an event has occurred, sent to whoever subscribed to it. It can be pushed to the recipient or held until the recipient fetches it.

Plain language A message reporting that an event occurred, sent to parties who subscribed to it.

Used in RFC 3995 RFC 3997 RFC 5277

A specification that fills in the details of the SIP event framework for one kind of event, such as its name, bodies and subscription duration.

Plain language A specification defining details of one type of SIP event, including event names and subscription duration.

Used in RFC 3265 RFC 3842 RFC 3856 RFC 4235 RFC 4575 RFC 4730 RFC 4826 RFC 5875 RFC 5989 RFC 6665

A named, continuously updating and chronologically ordered set of events on a publisher that receivers can subscribe to.

Plain language A named, continuously updating sequence of events available for subscription.

Used in RFC 5277 RFC 8639

A policy model where an event triggers evaluation of a condition, and if the condition is true, an action is executed. Example: Event = packet arrives, Condition = destination port is 445, Action = drop.

Plain language A policy model where an event triggers evaluation of a condition, and matching conditions execute an action.

Used in RFC 8328 RFC 8329

A structure defined by the Evidence Record Syntax that supports non-repudiation of the existence of data. It is kept up to date over time by re-protecting the data with newer keys and stronger algorithms.

Plain language A structure supporting non-repudiation of data existence over time, updated periodically with stronger security.

Used in RFC 4810 RFC 4998 RFC 5276 RFC 6283

Ethernet Virtual Private Network, a BGP-based way to carry Ethernet services across a provider network, defined in RFC 7432.

Plain language Ethernet Virtual Private Network, a BGP-based method for carrying Ethernet services across provider networks.

Used in RFC 6074 RFC 7152 RFC 7387 RFC 7439 RFC 7623 RFC 8214 RFC 8388 RFC 9047 RFC 9135 RFC 9136 RFC 9161 RFC 9251 RFC 9291 RFC 9572 RFC 9573 RFC 9574 RFC 9624 RFC 9744 RFC 9784 RFC 9785 RFC 9856 RFC 10018

A guarantee that a request is executed one time even if the client retries it. NFSv4.1 provides it through sessions, slots, sequence IDs and a reply cache.

Plain language A guarantee that retried requests execute only once through session tracking and reply caching.

Used in RFC 5661 RFC 8881

The hash H computed over both identification strings, both KEXINIT messages, the host key and the exchanged Diffie-Hellman values. The server signs it with its host key, and the first H of a connection also becomes the session identifier.

Plain language A hash computed from both parties' identification, messages and key exchange data, signed by the server.

Used in RFC 4253 RFC 4419 RFC 4432 RFC 4462 RFC 5656 RFC 8268 RFC 8731 RFC 8732 RFC 9037 RFC 9142

An IANA registration procedure in which a designated expert checks a request against stated criteria before it is accepted.

Plain language An IANA registration procedure where a designated expert reviews requests against stated criteria.

Used in RFC 3936 RFC 4520 RFC 5494 RFC 8137 RFC 9122 RFC 9519 RFC 9876

A two-way pairing between an IPv4 address and an IPv6 address configured in a translator, used instead of the translation prefix for matching addresses.

Plain language A configured list pairing IPv4 and IPv6 addresses in a translator instead of using a translation prefix.

Used in RFC 7755 RFC 7756 RFC 7757 RFC 8368

A mechanism for network devices to signal congestion to endpoints by marking packets instead of dropping them, using a 2-bit field in IP headers.

Plain language A network signal carried in IP packets to notify endpoints of congestion without dropping data.

Used in RFC 3042 RFC 3708 RFC 4163 RFC 4336 RFC 4342 RFC 4654 RFC 5166 RFC 5461 RFC 5562 RFC 5670 RFC 5690 RFC 6660 RFC 7125 RFC 7141 RFC 8084 RFC 8085 RFC 8087 RFC 8170 RFC 8257 RFC 8289 RFC 8311 RFC 8382 RFC 8698 RFC 8867 and 8 more

Two bits in the IP header that routers can use to signal congestion to endpoints without having to drop packets.

Plain language Two bits in IP headers that routers use to signal congestion without dropping packets.

Used in RFC 2914 RFC 3168 RFC 3360 RFC 3540 RFC 4340 RFC 4341 RFC 4591 RFC 4654 RFC 4774 RFC 5127 RFC 5129 RFC 5562 RFC 6040 RFC 6297 RFC 6660 RFC 6679 RFC 7141 RFC 7560 RFC 7713 RFC 7750 RFC 8033 RFC 8083 RFC 8290 RFC 8311 and 11 more

A path given as an ordered list of hops that signaling must follow, instead of leaving the choice to dynamic routing. Hops can be strict or loose.

Plain language A specified path as an ordered list of hops for signaling, instead of using dynamic routing.

Used in RFC 2430 RFC 3212 RFC 3213 RFC 3970 RFC 4920 RFC 5521 RFC 7392 RFC 8408 RFC 8779

An RSVP object carried in a Path message that lists the hops an LSP should take. Each hop can be strict or loose.

Plain language An RSVP object listing hops an LSP must follow, allowing strict or loose routing.

Used in RFC 3209 RFC 3477 RFC 4090 RFC 4208 RFC 5063 RFC 5151 RFC 5152 RFC 5520 RFC 5623 RFC 6383 RFC 6457 RFC 7570 RFC 7897 RFC 7898

Doubling a timer's value each time it expires without success, so repeated retries become less frequent. TCP does this to its retransmission timeout.

Plain language Progressively doubling retry timers to reduce the frequency of repeated attempts.

Used in RFC 1536 RFC 2730 RFC 2988 RFC 3203 RFC 4222 RFC 6298 RFC 7048 RFC 7252 RFC 7559 RFC 8253

The IMAP action that permanently removes messages marked with the deleted flag from a mailbox. Until then, a deleted message is only marked and can still be seen and unmarked.

Used in RFC 2180 RFC 4315 RFC 4549 RFC 5182 RFC 6851 RFC 9051

A BGP attribute that attaches additional tags to routes. In RFC 4360 each such community is 8 octets long, with a type and a sub-type.

Plain language A BGP attribute providing additional tags on routes, eight octets with type and subtype.

Used in RFC 4684 RFC 5701 RFC 7674 RFC 8534 RFC 9012 RFC 10005

An optional DNS message field that carries a numeric code giving more detail about why a query failed or was altered, such as Blocked, Censored or Filtered.

Used in RFC 8914 RFC 9276 RFC 9606

An X.509 certificate extension that specifies the purposes for which the certificate may be used, such as TLS server authentication or code signing.

Plain language An X.509 certificate extension specifying permitted uses such as TLS authentication or code signing.

Used in RFC 3770 RFC 4556 RFC 5924 RFC 6494 RFC 8550 RFC 9336 RFC 9480 RFC 9509 RFC 9809

An LDAPv3 mechanism for adding new request and response types, each identified by an object identifier. Password Modify is defined this way.

Plain language An LDAPv3 mechanism for adding new request and response types identified by object identifier.

Used in RFC 3062 RFC 3829 RFC 4531 RFC 4532

An Extended Sequence Number (ESN) is a 64-bit packet counter for an IPsec SA. Only the low-order 32 bits are sent in each packet, while both sides track the high-order bits locally.

Plain language A 64-bit IPsec packet counter where only the low 32 bits are sent but both sides track the full value.

Used in RFC 4302 RFC 4303 RFC 6776

An XML-based client-server protocol for provisioning and managing objects in a shared central repository, such as a domain registry.

Plain language An XML-based protocol for provisioning and managing domain names and other objects in a central registry.

Used in RFC 3732 RFC 3733 RFC 3735 RFC 3915 RFC 4114 RFC 4930 RFC 4931 RFC 4932 RFC 5076 RFC 5734 RFC 7848 RFC 8056 RFC 8334 RFC 8495 RFC 8544 RFC 8807 RFC 9038 RFC 9803 RFC 9873

An XML-based protocol that clients use to create and manage objects such as domain names in a shared central repository. Extensions add new kinds of data to its commands.

Plain language An XML-based protocol for clients to manage domain names and objects in a registry.

Used in RFC 5910 RFC 9022

An optional IPv6 header placed between the IPv6 header and the upper-layer header, found by following Next Header fields. Examples are Hop-by-Hop Options, Routing, Fragment and Destination Options.

Plain language Optional IPv6 headers between the main header and upper-layer header, such as options or routing.

Used in RFC 1710 RFC 1752 RFC 1883 RFC 1888 RFC 2292 RFC 2460 RFC 2473 RFC 2675 RFC 3025 RFC 3149 RFC 3542 RFC 3843 RFC 4064 RFC 4294 RFC 4552 RFC 4815 RFC 4917 RFC 4942 RFC 4964 RFC 5002 RFC 5094 RFC 5095 RFC 5096 RFC 5163 and 51 more

A protocol for exchanging network reachability information between autonomous systems (networks). EGP allows one network to learn what other networks another system can reach.

Plain language A protocol for exchanging reachability information between autonomous systems (separate networks).

Used in RFC 975 RFC 985 RFC 1133 RFC 3068

A pre-shared key established by some means other than an earlier TLS handshake, for example by configuration. It differs from a resumption PSK, which comes from a previous handshake.

Used in RFC 9257 RFC 9973