P

A private SIP header field whose name starts with "P-". The ones in RFC 7315 were defined for use in networks specified by the 3GPP.

Plain language A private SIP header starting with "P-" for use in 3GPP networks.

Used in RFC 3427 RFC 4457 RFC 7315 RFC 9878

A multicast tunnel through a service provider backbone that carries multicast traffic for a Multicast VPN between provider routers.

Plain language A multicast tunnel through provider networks for multicast VPN.

Used in RFC 6513 RFC 6625 RFC 7900 RFC 7988 RFC 8534 RFC 8556 RFC 9026 RFC 10018

A point-to-multipoint Label Switched Path, a tree-shaped MPLS path with one root and many leaves. Traffic is copied only where the tree branches.

Plain language A tree-shaped MPLS path from one source to multiple destinations.

Used in RFC 5073 RFC 5671 RFC 6826 RFC 7117 RFC 7524 RFC 8306

Recording the packets that pass over a network link, usually saving them to a file. The saved packets can be examined later to debug problems.

Plain language Recording network packets to a file for later analysis.

Used in RFC 1761 RFC 5345 RFC 8618

The situation where a packet sent across a network never arrives. Fractional loss is the share of packets that go missing on a path.

Plain language Packets failing to reach their destination on a network.

Used in RFC 1363 RFC 2198 RFC 2330 RFC 2416 RFC 2448 RFC 2680 RFC 3042 RFC 3357 RFC 3393 RFC 3432 RFC 3763 RFC 4224 RFC 4362 RFC 4594 RFC 4629 RFC 5148 RFC 5166 RFC 5560 RFC 6349 RFC 6412 RFC 6414 RFC 6703 RFC 7002 RFC 7003 and 18 more

A technique where a decoder hides the gap left by a lost audio packet, instead of playing silence or a click.

Plain language Hiding lost audio packets with predicted data instead of silence.

Used in RFC 3357 RFC 3951 RFC 3952 RFC 6716 RFC 7294 RFC 8130 RFC 8817

Selecting a subset of the packets seen at an observation point, using sampling or filtering techniques, and reporting on only the selected ones.

Plain language Monitoring a subset of packets rather than all traffic.

Used in RFC 5473 RFC 5474 RFC 5475 RFC 5476 RFC 5477 RFC 6727 RFC 6728

The layer of the network stack that segments data into packets and chooses where packet boundaries fall. TCP and SCTP are examples.

Plain language The layer that segments data into packets at chosen boundaries.

Used in RFC 2250 RFC 4821 RFC 6190 RFC 8899

Extra = characters added to the end of base-encoded output so its length is a whole multiple of the encoding's block size (4 characters for Base64, 8 for Base32).

Plain language Extra characters appended to base-encoded data to reach a multiple block size.

Used in RFC 44 RFC 54 RFC 64 RFC 70 RFC 102 RFC 1014 RFC 1319 RFC 1321 RFC 1377 RFC 1423 RFC 1570 RFC 1829 RFC 1851 RFC 1974 RFC 2040 RFC 2406 RFC 2410 RFC 2419 RFC 2420 RFC 2451 RFC 2522 RFC 2841 RFC 3174 RFC 3182 and 63 more

A weakness where a decryptor reveals whether padding was valid, letting an attacker learn plaintext by trying guesses. Checking integrity before decrypting avoids it.

Plain language A weakness where padding validation reveals information enabling plaintext recovery.

Used in RFC 7457 RFC 9459

A radio transmission facility that receives and distributes pages to individual pagers using protocols like TAP/IXO or TME.

Used in RFC 1645 RFC 1861

Protocol for carrying Authentication for Network Access. It is a UDP-based protocol that carries EAP authentication between a client and an authentication agent.

Plain language A protocol for sending authentication credentials over a network.

Used in RFC 4016 RFC 5193 RFC 5609 RFC 6345

The Password Authentication Protocol. A PPP authentication protocol in which the peer sends a name and password. PPP gives it the Protocol value 0xC023.

Plain language A PPP protocol sending username and password for authentication.

Used in RFC 1331 RFC 1471 RFC 1472 RFC 1548 RFC 1661 RFC 1994 RFC 2138 RFC 2284 RFC 2341 RFC 2363 RFC 2364 RFC 2477 RFC 2607 RFC 2809 RFC 2989 RFC 3127 RFC 5281 RFC 8907

A block of H.264 settings, such as picture size, that applies to many slices. Sequence and picture parameter sets are sent separately from the slice data.

Plain language H.264 settings like image size sent separately to enable video decoding.

Used in RFC 3984 RFC 6184

The parent-side entity, such as a registry or registrar, that fetches a child's CDS, CDNSKEY or CSYNC records and updates the delegation based on them.

Plain language A parent-side system that fetches child records and updates delegations.

Used in RFC 7344 RFC 7477 RFC 9615 RFC 9975 RFC 10026

An acknowledgment that confirms some but not all of the data outstanding when fast recovery began, indicating additional packet losses.

Plain language An acknowledgment confirming some data while indicating other losses.

Used in RFC 2582 RFC 3782 RFC 6582

A transport option where some messages are sent with a delivery guarantee and others may be dropped instead of retransmitted. For SCTP it is defined in the PR-SCTP extension.

Plain language A transport option where some messages are guaranteed and others may be dropped.

Used in RFC 3758 RFC 5811 RFC 6084 RFC 6526 RFC 8850

An attack in which the attacker only reads packets off the network and does not write any. Password sniffing is an example.

Plain language An attacker reads network packets but does not send any, for example to capture passwords.

Used in RFC 3552 RFC 8164

An FTP mode in which the client sends PASV, the server replies with an address and port it is listening on, and the client opens the data connection to it. Without it the server connects back to the client.

Plain language In FTP, the client tells the server to listen on a port and the client connects to it for data transfer.

Used in RFC 614 RFC 959 RFC 1579 RFC 1639 RFC 2428 RFC 2577 RFC 4217 RFC 8321 RFC 8889 RFC 9341

A secret phrase used to encrypt a private key on disk, so that the key can be used only after the user types it.

Plain language A secret phrase that unlocks a private key stored on disk.

Used in RFC 1760 RFC 1938 RFC 2289 RFC 3112 RFC 3211 RFC 4252 RFC 6030 RFC 7613 RFC 7717 RFC 8110 RFC 8125 RFC 8265 RFC 8807 RFC 9580

A signed token that asserts a telephone identity in STIR. The authentication service creates it and carries it in a SIP Identity header field.

Plain language A digitally signed token in STIR that proves which telephone number is making a call.

Used in RFC 8224 RFC 8816 RFC 8946 RFC 9027 RFC 9118 RFC 9410 RFC 9475 RFC 9795 RFC 9888 RFC 9970

A value computed from a password that a server stores in place of the password itself. It lets the server check a login without holding the password.

Plain language A scrambled value derived from a password that a server keeps instead of the password itself.

Used in RFC 2945 RFC 5054

A cryptographic protocol that allows two parties to derive a shared secret key using a password, without revealing the password or the key to eavesdroppers.

Plain language A protocol where two parties create a shared secret using only a password, without revealing the password.

Used in RFC 5931 RFC 7664 RFC 8125 RFC 8492 RFC 9383 RFC 9588

Information attached to a route that describes its characteristics, origin, and selection metrics, used by BGP to choose the best path.

Used in RFC 1657 RFC 1771

Endpoint discovery of network path properties (latency, loss, bandwidth) and endpoint reaction to those properties that affects routing and data transfer decisions.

Used in RFC 9049 RFC 9217

A client that asks a Path Computation Element to compute one or more paths and receives the results, as defined in RFC 4655 and used by RFC 5440.

Plain language The program that asks a route-planning server to work out a path for it.

Used in RFC 5521 RFC 5541 RFC 5862 RFC 6457 RFC 7399 RFC 7449 RFC 7897 RFC 8233 RFC 8408 RFC 8413 RFC 8685 RFC 8745 RFC 9050 RFC 9862 RFC 9933

A network entity that computes a path or route from a network graph while applying constraints. Clients ask it for paths using PCEP.

Plain language A network device that calculates paths through a network while respecting constraints.

Used in RFC 4655 RFC 4657 RFC 4674 RFC 4726 RFC 5088 RFC 5089 RFC 5152 RFC 5441 RFC 5455 RFC 5468 RFC 5520 RFC 5521 RFC 5541 RFC 5553 RFC 5671 RFC 5817 RFC 5828 RFC 5862 RFC 5886 RFC 6163 RFC 6457 RFC 7025 RFC 7399 RFC 7449 and 46 more

A component that computes network paths on behalf of other nodes, using a database of the network's topology. It answers path requests from clients called PCCs.

Plain language A network component that calculates paths for other devices to use.

Used in RFC 5520 RFC 5623 RFC 5671 RFC 5817 RFC 5824 RFC 7062 RFC 7471 RFC 7579 RFC 7926 RFC 8306 RFC 8751 RFC 8779 RFC 9050 RFC 9689 RFC 9757 RFC 9862 RFC 9933 RFC 9960

Arranging for two connections to follow paths that share no links, nodes or risk groups. A single failure then cannot take both down.

Plain language Arranging two connections to use completely separate routes, so one failure does not block both.

Used in RFC 4054 RFC 5520 RFC 5521 RFC 8390 RFC 8800

A situation where a route server picks one best path for a prefix, but policy stops that path reaching a client. The client then gets no path, even though another valid path existed.

Used in RFC 5521 RFC 7947 RFC 7948

A token that stands in for a hidden path segment. Only the path computation element it names can turn it back into the real list of nodes and links.

Plain language A token representing a hidden portion of a route that only the path computation element can decode.

Used in RFC 5520 RFC 5521 RFC 5553 RFC 5623

The smallest MTU of all the links between a sender and a receiver. A datagram no bigger than the Path MTU can travel the whole way without being split up.

Plain language The smallest maximum packet size of all links between sender and receiver.

Used in RFC 1191 RFC 1752 RFC 1853 RFC 1883 RFC 1905 RFC 1981 RFC 2210 RFC 2215 RFC 2401 RFC 2473 RFC 2525 RFC 2745 RFC 2923 RFC 2960 RFC 2991 RFC 3124 RFC 3209 RFC 3542 RFC 4301 RFC 4347 RFC 4623 RFC 4821 RFC 4828 RFC 4907 and 44 more

The process by which a sender finds the largest packet that fits through every link on a route. In IPv6 it relies on ICMPv6 Packet Too Big messages, and the procedure is described in RFC 8201.

Plain language The process a sender uses to find the largest packet size that fits through every link on a route.

Used in RFC 792 RFC 1332 RFC 1435 RFC 1726 RFC 1826 RFC 1981 RFC 2003 RFC 2004 RFC 2067 RFC 2147 RFC 2176 RFC 2225 RFC 2414 RFC 2431 RFC 2463 RFC 2467 RFC 2473 RFC 2488 RFC 2492 RFC 2675 RFC 2784 RFC 2893 RFC 2923 RFC 2991 and 84 more

A measurable or observable characteristic of a path element, a subpath, or an entire path. Properties can describe performance (delay, loss), resources (cost, capacity), services (available protocols), or topology (disjointness, symmetry).

Plain language A characteristic of a network path such as delay, cost, available bandwidth or symmetry.

Used in RFC 9217 RFC 9473

A message sent to or from an on-path network element, which can be implicit (derived from unintended information visibility) or explicit (intentionally designed for a specific purpose).

Plain language A message sent to or from a router on the path, either deliberately designed or inadvertently revealed.

Used in RFC 5063 RFC 8558 RFC 9419

A QUIC check that an endpoint can really receive packets at a new address. One side sends a PATH_CHALLENGE frame and the other must answer with a matching PATH_RESPONSE.

Plain language A QUIC check where one side sends a challenge and the other must reply with a matching response.

Used in RFC 3280 RFC 4806 RFC 5061 RFC 5276 RFC 5937 RFC 6010 RFC 6480 RFC 6811 RFC 7353 RFC 8205 RFC 8206 RFC 8481 RFC 9000 RFC 9853

A routing protocol in which each route advertisement carries the full list of autonomous systems it has passed through. The list lets a router detect loops and apply policy to the whole path rather than just a distance.

Plain language A routing protocol where each route advertisement includes the list of networks it passed through.

Used in RFC 1322 RFC 1621 RFC 2545 RFC 3036 RFC 3219 RFC 4271 RFC 4273 RFC 4274 RFC 6836 RFC 6998 RFC 7132

Protection Against Wrapped Sequences. A TCP mechanism that uses the Timestamps option to discard old duplicate segments when sequence numbers wrap around on a fast connection.

Plain language A TCP mechanism using timestamps to discard old duplicate packets when sequence numbers wrap around.

Used in RFC 1323 RFC 2883 RFC 7323

A 7-bit field in the RTP header that says which format the payload holds, such as a particular audio codec, so the receiver knows how to decode it.

Plain language A field in RTP headers identifying the format of the audio or video data.

Used in RFC 1889 RFC 1890 RFC 2035 RFC 2038 RFC 2190 RFC 2198 RFC 2250 RFC 2305 RFC 2327 RFC 2431 RFC 2658 RFC 2733 RFC 2736 RFC 2793 RFC 2823 RFC 2862 RFC 3009 RFC 3016 RFC 3047 RFC 3108 RFC 3119 RFC 3190 RFC 3264 RFC 3389 and 86 more

Password-Based Key Derivation Function 2, which applies a hash function many times (the iteration count) to slow down attackers trying to guess the password.

Plain language A function that applies a hash many times to a password, making it slower and harder for attackers to guess.

Used in RFC 2898 RFC 5018 RFC 5959 RFC 8018 RFC 9579 RFC 10004

Password-Based Message Authentication Code 1, a scheme for using modern key derivation functions to compute message authentication codes from a password.

Plain language A scheme for computing authentication codes from a password using modern key derivation.

Used in RFC 9481 RFC 9579

An extension of the PCE role where the PCE not only computes paths but also directly downloads forwarding instructions to network routers, making it a central control point for the network's forwarding behavior.

Used in RFC 9050 RFC 9689

The Path Computation Element Communication Protocol, used between a client and a path computation element that calculates network paths. It is defined in RFC 5440.

Plain language The protocol by which network devices request path calculations from a path computation element.

Used in RFC 5520 RFC 5521 RFC 5541 RFC 5671 RFC 5862 RFC 6457 RFC 7399 RFC 7449 RFC 7897 RFC 8233 RFC 8253 RFC 8306 RFC 8408 RFC 8413 RFC 8623 RFC 8637 RFC 8685 RFC 8697 RFC 8745 RFC 8779 RFC 8800 RFC 9005 RFC 9050 RFC 9357 and 5 more

A protocol data unit: one message-sized chunk of a protocol, with defined fields, that is carried between two parties.

Plain language A protocol data unit: one complete message a protocol sends between two parties.

Used in RFC 1085 RFC 1157 RFC 1238 RFC 1240 RFC 1448 RFC 1483 RFC 1905 RFC 2571 RFC 2741 RFC 3410 RFC 3416 RFC 3719 RFC 5046

The ordered IPsec list that says which peers a node will accept, how each must authenticate, and which child SAs they may create. It is searched when a peer connects.

Used in RFC 5386 RFC 7619

A way of building a system in which the participants both use a service and provide it to each other, instead of all relying on one central server.

Plain language A system where participants both use a service and provide it to each other instead of relying on a central server.

Used in RFC 4981 RFC 5594 RFC 5632 RFC 5693 RFC 5694 RFC 6029 RFC 6392 RFC 6646 RFC 6875 RFC 6940 RFC 7285 RFC 7846 RFC 7890

A picture element, the smallest unit of a displayed image, which in a bitmap is a single dot that can be either black or white.

Plain language A picture element: the smallest single dot in a displayed image.

Used in RFC 798 RFC 804

A data structure in each forwarder that records which faces incoming requests arrived on, so replies can be forwarded back along the path they came from.

Plain language A router's record of which incoming ports received requests, used to forward replies back.

Used in RFC 8569 RFC 8793 RFC 9064 RFC 9139 RFC 9344 RFC 9531

Removing the top label at the second-to-last router on a path, so the final router receives the packet without that label.

Plain language Removing a label at the second-to-last router on a path so the final router sees the packet without it.

Used in RFC 3031 RFC 3270 RFC 5129 RFC 5695 RFC 6373 RFC 8287 RFC 8372 RFC 8661 RFC 8665 RFC 8667 RFC 8957

The forwarding treatment a network node applies to a packet based on its DSCP, such as priority queuing, drop precedence, or rate limiting.

Plain language The forwarding treatment a router applies to a packet based on its traffic class.

Used in RFC 2475 RFC 2836 RFC 3247 RFC 3289 RFC 5777 RFC 7657 RFC 9956

The externally visible forwarding treatment a differentiated-services node gives a behavior aggregate, such as best-effort or preferential queueing. It describes the result, not the algorithm used.

Plain language The forwarding treatment a router applies to a packet based on its traffic class marking.

Used in RFC 2474 RFC 2475 RFC 2597 RFC 2598 RFC 2697 RFC 2836 RFC 2859 RFC 2983 RFC 2996 RFC 2998 RFC 3086 RFC 3140 RFC 3175 RFC 3246 RFC 3247 RFC 3248 RFC 3260 RFC 3270 RFC 3287 RFC 3289 RFC 3290 RFC 3308 RFC 3644 RFC 3670 and 25 more

A way to write any byte inside a URI as a percent sign followed by two hexadecimal digits, for example %20 for a space. It is used for bytes outside the allowed character set and for reserved characters that must be treated as plain data.

Plain language A way to write unusual bytes in a URI as a percent sign followed by two hexadecimal digits.

Used in RFC 1630 RFC 1738 RFC 2017 RFC 2141 RFC 2184 RFC 2231 RFC 2254 RFC 2255 RFC 2368 RFC 2392 RFC 2396 RFC 3368 RFC 3966 RFC 3986 RFC 3987 RFC 4088 RFC 4151 RFC 4501 RFC 4516 RFC 4622 RFC 5023 RFC 5092 RFC 5122 RFC 5137 and 23 more

A property of key-establishment in which compromise of a session key or long-term private key after a session does not compromise earlier sessions. RFC 4251 notes that SSH Diffie-Hellman key exchanges provide it.

Plain language Property where compromise of current keys does not compromise earlier sessions.

Used in RFC 1984 RFC 2409 RFC 2412 RFC 2786 RFC 3268 RFC 3585 RFC 3830 RFC 4101 RFC 4251 RFC 4279 RFC 4430 RFC 4492 RFC 4650 RFC 5246 RFC 5479 RFC 5487 RFC 5489 RFC 5590 RFC 5683 RFC 5763 RFC 5931 RFC 5953 RFC 6124 RFC 6189 and 53 more

A property of a key agreement protocol where compromising the long-term secret key does not compromise the security of past session keys.

Plain language A security property where compromising a long-term key does not compromise past session keys.

Used in RFC 2409 RFC 5197 RFC 5479 RFC 6267 RFC 9048

A quantitative measure of performance for an IETF-specified protocol, or for an application carried over one. Examples include the DNS response time to resolve an address.

Plain language A measurable number showing how well a protocol or network is performing.

Used in RFC 1857 RFC 2330 RFC 3393 RFC 3593 RFC 3896 RFC 5560 RFC 6576 RFC 6776 RFC 8911 RFC 9341

An HTTP/1.1 connection that stays open after a response so further requests can reuse it. It is the default in HTTP/1.1; a Connection: close option ends it.

Plain language An HTTP connection that stays open after each response to allow more requests on the same connection.

Used in RFC 2068 RFC 2616 RFC 2818 RFC 3010 RFC 5923 RFC 6202 RFC 6712 RFC 7230 RFC 7766 RFC 8895 RFC 9112 RFC 9931

A name or number that refers to the same resource for as long as the resource exists, independent of the resource's physical location or the organization maintaining it.

Plain language A name that refers to the same resource permanently, regardless of where the resource moves.

Used in RFC 3121 RFC 6973 RFC 7818 RFC 8458 RFC 8574

Widespread surveillance of Internet communications at a scale that affects all users and services, as described in RFC 7258 as a threat to privacy on the Internet.

Plain language Large-scale surveillance of Internet traffic affecting all users.

Used in RFC 7536 RFC 7624 RFC 7819 RFC 8164 RFC 8165 RFC 8404 RFC 9446

Pretty Good Privacy, a system for encrypting data and creating digital signatures with public keys. Its output can be written as text so that it travels through email.

Used in RFC 1505 RFC 1844 RFC 2015 RFC 2316 RFC 2350 RFC 3156 RFC 4880

A Per-Hop Behavior group for which a common constraint is that ordering of at least those packets belonging to the same microflow must be preserved.

Plain language A group of forwarding behaviors where packets from the same conversation stay in order.

Used in RFC 3140 RFC 3260

The Presence Information Data Format, a basic XML format for presenting presence information about a presentity. Extensions add further elements to it.

Plain language The Presence Information Data Format: a basic XML format for sharing online status.

Used in RFC 3856 RFC 3859 RFC 3922 RFC 3953 RFC 4079 RFC 4479 RFC 4480 RFC 4481 RFC 4482 RFC 5263 RFC 6271

Presence Information Data Format Location Object; an XML-based standard format for conveying location information in SIP and other Internet protocols.

Plain language An XML format for conveying location information in SIP and other protocols.

Used in RFC 5139 RFC 5774 RFC 6225 RFC 6753 RFC 6881 RFC 7378 RFC 7852

A tool that sends an ICMP Echo Request to a host and waits for an Echo Reply, to check that it is reachable and to time the round trip.

Plain language A tool that sends a request to a host and waits for the reply to check reachability and latency.

Used in RFC 240 RFC 252 RFC 255 RFC 267 RFC 791 RFC 792 RFC 889 RFC 1470 RFC 1574 RFC 1575 RFC 1578 RFC 1739 RFC 2151 RFC 2463 RFC 2466 RFC 2681 RFC 2925 RFC 2991 RFC 3542 RFC 3763 RFC 4377 RFC 4379 RFC 4560 RFC 5085 and 44 more

Control frames (opcodes 0x9 and 0xA). A Ping asks if the other side is alive, and the receiver should answer with a Pong.

Plain language Control frames where Ping asks if the other side is alive and Pong replies yes.

Used in RFC 6455

A narrow opening in a firewall that permits one specific TCP or UDP session, whose ports are determined dynamically, to pass through.

Plain language A narrow opening in a firewall for one specific session whose ports are assigned dynamically.

Used in RFC 3303 RFC 3989 RFC 4540 RFC 5189 RFC 5596

The protocol used to invoke telephone services from an IP network. Version 1.0 of the PINT service protocol specifies a set of enhancements to SIP 2.0 and SDP, and was developed in the IETF PINT working group.

Plain language The agreed way for a computer on the Internet to ask the telephone network to do something with a call.

Used in RFC 2995 RFC 3136

The PINT server that relays received requests into a telephone system and receives acknowledgement of them. It appears to a SIP system as a User Agent Server, and to the PINT infrastructure it looks as if it represents a single user.

Plain language The server that takes a request from the Internet and hands it to the telephone network.

Used in RFC 2458 RFC 2848

A method of estimating how many bytes of data are currently outstanding in the network, used by the sender to limit its sending rate during loss recovery.

Used in RFC 3517 RFC 6675

Sending several requests over one connection without waiting for each reply. Responses may then return out of order and are matched to requests by an identifier.

Plain language Sending multiple requests over one connection without waiting for each reply.

Used in RFC 1203 RFC 1936 RFC 2033 RFC 2068 RFC 2326 RFC 2371 RFC 2449 RFC 2616 RFC 2920 RFC 3030 RFC 3207 RFC 3502 RFC 3656 RFC 3977 RFC 4037 RFC 4468 RFC 4644 RFC 4954 RFC 4991 RFC 4992 RFC 5161 RFC 5182 RFC 5734 RFC 6202 and 14 more

Proof Key for Code Exchange, defined in RFC 7636. The client sends a hashed secret with the authorization request and the original secret with the token request, so a stolen authorization code is useless to an attacker.

Plain language A method where the client hashes a secret with the authorization request and sends the original secret later.

Used in RFC 6749 RFC 7636 RFC 8252 RFC 8414 RFC 9126 RFC 9449 RFC 9700 RFC 10017 RFC 10027

Public key infrastructure. The CAs, certificates, policies and validation rules that let parties trust public keys.

Plain language Public key infrastructure: the certification authorities, certificates and policies for trusting public keys.

Used in RFC 1422 RFC 2312 RFC 2459 RFC 2510 RFC 2527 RFC 2528 RFC 2559 RFC 2560 RFC 2585 RFC 2587 RFC 2797 RFC 2986 RFC 3029 RFC 3161 RFC 3193 RFC 3280 RFC 3447 RFC 3647 RFC 3709 RFC 3739 RFC 3740 RFC 3820 RFC 4043 RFC 4059 and 114 more

Public Key Cryptography for Initial Authentication in Kerberos. It lets a client authenticate to the KDC with a certificate and private key instead of a password.

Plain language A way to authenticate to Kerberos using a certificate and private key instead of a password.

Used in RFC 6112 RFC 8062 RFC 8070

A TPM storage slot that holds a rolling hash of the measurements added to it.

Plain language A TPM storage slot that accumulates measurements and never erases them.

Used in RFC 9683 RFC 9684

In BRSKI, a prospective, unconfigured device that has an identity installed at the factory and is trying to join a network domain.

Plain language An unconfigured device with a factory-installed identity trying to join a network domain.

Used in RFC 8995 RFC 9031 RFC 9733

P-Multicast Service Interface: a conceptual interface a PE uses to send customer multicast traffic to all PEs in a VPN (inclusive) or to some of them (selective).

Plain language A multicast interface that a provider edge router uses to send customer multicast traffic to other routers.

Used in RFC 6513 RFC 6514 RFC 7988 RFC 8503 RFC 9572

Parallel NFS, a feature of NFSv4.1 that lets clients read and write data by means other than sending those operations to the server. The server manages the metadata.

Plain language Parallel NFS: a feature letting clients read and write file data directly from storage while a server manages metadata.

Used in RFC 5661 RFC 5663 RFC 5664 RFC 6688 RFC 8881 RFC 9561

The information a pNFS client uses to reach file data on storage devices. It names the protocol (the layout type) and the storage devices to use.

Plain language Information telling a pNFS client where file data is located on storage devices.

Used in RFC 8434 RFC 8435

The identifier of a node that has an MTP3 layer in an SS7 network. Each M2PA IP Signaling Point must have its own point code.

Plain language The identifier of a node that has an MTP3 layer in an SS7 telephone network.

Used in RFC 4165 RFC 4666

The router next to a failed link or node that detects the failure and moves traffic onto a pre-computed alternate path.

Plain language The router next to a failure that detects it and moves traffic to a backup path.

Used in RFC 4090 RFC 4561 RFC 6414 RFC 6894 RFC 7490 RFC 7715 RFC 7811 RFC 7812 RFC 8104 RFC 8271 RFC 8400 RFC 8537 RFC 8679 RFC 8796 RFC 9705 RFC 9855 RFC 9912

A physical location where an Internet Service Provider operates access servers that users can dial in to.

Plain language A physical location where an ISP operates access servers users can dial into.

Used in RFC 2477 RFC 3017

A label switched path with one ingress and several egress routers. It is built from multiple source-to-leaf sub-LSPs overlaid to form a tree.

Plain language A label switched path going from one entrance to multiple exits, shaped like a tree.

Used in RFC 4461 RFC 5862 RFC 7334 RFC 7338 RFC 7442 RFC 7524 RFC 8306 RFC 9573

An ATM virtual circuit from one sender to multiple receivers, established once and used to send the same data to all members.

Used in RFC 2022 RFC 2149 RFC 3038

A link with exactly two ends, such as a cable between two routers. No other devices share it.

Plain language A network link connecting exactly two devices with no other parties.

Used in RFC 1331 RFC 1547 RFC 1663 RFC 1974 RFC 1979 RFC 2118 RFC 5154 RFC 5303 RFC 6164 RFC 6653

A way of choosing measurement times at random, with a fixed average rate. It avoids lining up with regular patterns in the traffic and limits bias.

Plain language Selecting measurement times at random with a fixed average rate to avoid bias.

Used in RFC 2330 RFC 2679 RFC 2680 RFC 2681 RFC 3357 RFC 3393 RFC 3432 RFC 5814 RFC 7312 RFC 7680

Checking traffic against the description a flow supplied when it was set up, so that traffic beyond that description is handled separately from the traffic inside it.

Plain language Checking arriving traffic against the limit the sender promised, and treating the extra traffic differently.

Used in RFC 2211 RFC 2430 RFC 2638 RFC 4115 RFC 5777 RFC 7640

The server that makes policy decisions. In COPS it answers the requests that a policy enforcement point sends.

Plain language The server that makes yes-or-no decisions when asked by a policy enforcement point.

Used in RFC 2748 RFC 2749 RFC 2750 RFC 2753 RFC 2768 RFC 2904 RFC 2906 RFC 3084 RFC 3181 RFC 3182 RFC 3198 RFC 3313 RFC 3460 RFC 3520 RFC 3521 RFC 3571 RFC 3644 RFC 3703 RFC 3838 RFC 4097 RFC 4261 RFC 7149 RFC 9315

A network device (router, switch, access control device) that receives policies from a PDP and applies them to network traffic.

Plain language A network device that receives policies from a decision server and applies them to traffic.

Used in RFC 2748 RFC 2749 RFC 2750 RFC 2753 RFC 2872 RFC 3084 RFC 3181 RFC 3198 RFC 3313 RFC 3460 RFC 3483 RFC 3521 RFC 3571 RFC 3644 RFC 3703 RFC 3838 RFC 4097 RFC 4261 RFC 9315 RFC 10065

A physical router at the boundary of an administrative domain, responsible for forwarding transit traffic according to the domain's transit policies and participating in IDPR path setup.

Plain language A router at the edge of a network that controls whether traffic is allowed in or out.

Used in RFC 1102 RFC 1478

A structured database of configuration classes and instances that define policy to be downloaded to a network device, such as a router, to control its behavior.

Plain language A structured database of configuration rules downloaded to network devices to control behavior.

Used in RFC 3317 RFC 3318 RFC 3571 RFC 3780

A binding of an action to a condition that selects a set of packets. In MIDCOM each rule has exactly one action, either reserve or enable.

Plain language A binding of an action to a condition selecting packets, such as reserve or enable.

Used in RFC 2758 RFC 3060 RFC 3198 RFC 3460 RFC 3703 RFC 3838 RFC 4540 RFC 5189 RFC 5973 RFC 9315

A request-and-answer exchange in which one system flags a packet as a Poll and the other answers with a Final, used to confirm a parameter change or connectivity.

Plain language A request from one system and a response from the other confirming a parameter change.

Used in RFC 5880 RFC 8563

Repeatedly asking a system for its current data at intervals, rather than being told when something changes.

Plain language Repeatedly asking a system for current data at intervals instead of being notified.

Used in RFC 869 RFC 1857 RFC 8641

A single server instance that has registered itself as part of a server pool.

Plain language A single server registered as part of a server pool.

Used in RFC 3237 RFC 5351 RFC 5352 RFC 5354 RFC 5356

A logical name or identifier that points to a server pool, used by clients to refer to the pool without needing to know individual server addresses.

Plain language A logical name pointing to a server pool used by clients.

Used in RFC 3237 RFC 5351 RFC 5352 RFC 5355

The Post Office Protocol, version 3. A simple TCP protocol (port 110) that lets a mail client download messages from a maildrop on a server.

Plain language Post Office Protocol version 3: a protocol letting mail clients download messages from a server.

Used in RFC 1056 RFC 1081 RFC 1082 RFC 1176 RFC 1203 RFC 1225 RFC 1460 RFC 1725 RFC 1733 RFC 1734 RFC 1844 RFC 1939 RFC 1957 RFC 2195 RFC 2384 RFC 2444 RFC 2449 RFC 2532 RFC 2595 RFC 2683 RFC 3206 RFC 3249 RFC 3656 RFC 4409 and 12 more

A protocol in which a client asks a PCP server, such as a NAT or firewall, to create or manage mappings for its traffic. It is defined in RFC 6887.

Used in RFC 6886 RFC 7488 RFC 9895

A protocol, defined in RFC 6887, that lets a client ask a NAT or firewall to create and manage port mappings, for example through its MAP opcode.

Plain language A protocol letting clients ask a NAT or firewall to manage port mappings.

Used in RFC 7220 RFC 7225 RFC 7291 RFC 7393 RFC 7753

Carrying ordinary TCP connections through an SSH connection. Local forwarding opens a direct-tcpip channel, and remote forwarding is requested with tcpip-forward and delivered through forwarded-tcpip channels.

Plain language Carrying TCP connections through an SSH connection via encrypted tunnels.

Used in RFC 4254 RFC 6269 RFC 6346 RFC 6431 RFC 6886 RFC 6887 RFC 6970 RFC 7393 RFC 7843 RFC 8045 RFC 8455 RFC 9987

The mapping between a customer's port identifier (CPI) and the provider's internal port identifier (PPI). L1VPN discovery automates this mapping across all edge routers.

Used in RFC 5523 RFC 6285 RFC 6886

A 16-bit number in the TCP header that identifies an application service on a host, so many conversations can share the same pair of addresses.

Plain language A 16-bit number in the TCP header identifying an application service on a host.

Used in RFC 61 RFC 62 RFC 65 RFC 175 RFC 349 RFC 429 RFC 470 RFC 503 RFC 617 RFC 675 RFC 717 RFC 731 RFC 750 RFC 755 RFC 758 RFC 761 RFC 762 RFC 768 RFC 770 RFC 776 RFC 790 RFC 793 RFC 807 RFC 811 and 307 more

An identifier for a range of transport-layer ports assigned to one client. Together with a shared IPv4 address it identifies that client's lease.

Plain language An identifier for a range of ports assigned to one client sharing a public IPv4 address.

Used in RFC 7596 RFC 7599 RFC 7618

A value that identifies the set of transport ports assigned to one customer when several customers share a single IPv4 address. A PSID of k bits gives a sharing ratio of 2^k.

Plain language A value identifying which transport ports are assigned to one customer on a shared IPv4 address.

Used in RFC 7598 RFC 8658

An XML container that carries a symmetric key together with the metadata and policy needed to use it, so that keys can be moved between products from different vendors.

Plain language A standard XML file for handing a shared secret to a device, together with the rules for using it.

Used in RFC 6030 RFC 6031

Cryptographic algorithms designed to stay secure even against attackers who have large quantum computers.

Plain language Cryptographic algorithms designed to resist attacks from large quantum computers.

Used in RFC 8240 RFC 8778 RFC 8784 RFC 9370 RFC 9794 RFC 9814 RFC 9851 RFC 9881 RFC 9882 RFC 9909 RFC 9954 RFC 9964 RFC 9980

An extra secret shared in advance by two IKEv2 peers and mixed into key derivation. It keeps the derived keys safe even if a quantum computer breaks the Diffie-Hellman exchange.

Plain language An extra secret shared in advance that protects keys even if quantum computers break the key exchange.

Used in RFC 8784 RFC 9867

The process of collecting the configuration and status of an endpoint's hardware and software and evaluating it against a security compliance policy.

Plain language Checking a computer's hardware and software configuration against security requirements.

Used in RFC 5209 RFC 7171

A set of IPv4 addresses of routers that a tunneling host may use for router and prefix discovery. Each entry has its own refresh timer.

Plain language A list of routers a host may ask for directions with separate refresh timers for each.

Used in RFC 4214 RFC 5214

The Point-to-Point Protocol. A standard way to carry network-layer packets over a link between exactly two peers, with its own control protocols for setting up the link and each network protocol.

Plain language Point-to-Point Protocol: a standard way to carry network packets over a two-node link.

Used in RFC 1144 RFC 1172 RFC 1207 RFC 1220 RFC 1331 RFC 1332 RFC 1334 RFC 1376 RFC 1377 RFC 1378 RFC 1471 RFC 1472 RFC 1473 RFC 1474 RFC 1547 RFC 1548 RFC 1549 RFC 1552 RFC 1553 RFC 1570 RFC 1598 RFC 1618 RFC 1619 RFC 1634 and 144 more

PPP over Ethernet, a method of carrying PPP sessions inside Ethernet frames. It adds a discovery stage to find the peer and set up a session identifier.

Plain language PPP over Ethernet: a way to run dial-up-style authentication over an Ethernet cable.

Used in RFC 2516 RFC 3817 RFC 5578

Proof of knowledge of the client's key sent with the initial request, such as an encrypted timestamp. It stops the KDC handing out password-protected ciphertext to anyone who asks.

Plain language Proof of knowing the client's key sent with the initial request to prevent handing credentials to anyone.

Used in RFC 2060 RFC 4120 RFC 4556 RFC 4557 RFC 5247 RFC 5836 RFC 5873 RFC 6113 RFC 6252 RFC 6560 RFC 6697 RFC 6806 RFC 7268 RFC 8062 RFC 8070 RFC 8129 RFC 8437 RFC 8636 RFC 9588

A mechanism where routers mark packets before actual congestion occurs, signaling to edge routers that traffic is approaching capacity limits.

Plain language Routers marking packets before actual congestion to signal that traffic is approaching capacity.

Used in RFC 5559 RFC 5670 RFC 6660 RFC 6661 RFC 6662 RFC 7141 RFC 7417

A secret that both sides already hold before a handshake, either configured ahead of time or derived from an earlier connection. TLS 1.3 uses PSKs for resumption.

Plain language A secret both sides hold before a handshake, either configured ahead of time or from a prior connection.

Used in RFC 1244 RFC 2412 RFC 3562 RFC 3723 RFC 3788 RFC 3821 RFC 3830 RFC 4107 RFC 4109 RFC 4186 RFC 4279 RFC 4449 RFC 4563 RFC 4650 RFC 4738 RFC 4754 RFC 4764 RFC 4785 RFC 4851 RFC 4868 RFC 4895 RFC 5018 RFC 5054 RFC 5077 and 76 more

A preannouncement of a certificate that a CA submits to a log before issuing it. Signing one indicates the CA's binding intent to issue the matching certificate.

Plain language A preannouncement of a certificate that a CA submits to a log before issuing it.

Used in RFC 6962 RFC 9162

A framework from the IETF for the preparation, enforcement and comparison of internationalized strings in application protocols. It replaces stringprep for this purpose.

Plain language A framework for handling internationalized strings fairly by applying consistent preparation rules.

Used in RFC 6885 RFC 7622 RFC 8264 RFC 8265 RFC 8266

A time synchronization protocol specified in IEEE Std 1588-2008, which can provide synchronization as fine as nanoseconds. Clocks in a network use it to agree on the time.

Plain language A protocol for network clocks to synchronize to within nanoseconds.

Used in RFC 7273 RFC 8575

Taking resources away from an existing lower-priority reservation so that a higher-priority request can be admitted.

Plain language Taking resources from a lower-priority reservation to admit a higher-priority request.

Used in RFC 2787 RFC 3209 RFC 4128 RFC 4190 RFC 4412 RFC 4495 RFC 4829 RFC 5975 RFC 7412 RFC 8413

A rank that says how important a flow is compared with others competing to be admitted. A node that is full can use it to drop less important admitted flows and make room for a more important new one.

Plain language A rank determining how important a flow is relative to others competing for admission.

Used in RFC 2749 RFC 2751 RFC 3181 RFC 3209 RFC 4124

The leading bits of an address that identify a network, together with how many bits there are. In 192.168.99.0/24 the prefix is the first 24 bits.

Plain language The leading bits of an address identifying a network, written with the count such as /24.

Used in RFC 1519 RFC 1629 RFC 1771 RFC 1786 RFC 1787 RFC 1879 RFC 1887 RFC 1888 RFC 1930 RFC 1937 RFC 2072 RFC 2260 RFC 2280 RFC 2332 RFC 2342 RFC 2373 RFC 2439 RFC 2462 RFC 2546 RFC 2622 RFC 2725 RFC 2772 RFC 2827 RFC 2858 and 189 more

A set of bit patterns in which no pattern is the beginning of another, so a decoder can read a stream symbol by symbol without ambiguity. It is usually drawn as a binary tree with symbols on the leaves.

Plain language A set of bit patterns where no pattern begins another, allowing unambiguous decoding.

Used in RFC 1951 RFC 7932 RFC 9841

A DHCPv6 mechanism by which a service provider hands a router a block of IPv6 addresses to divide among its own networks.

Plain language A DHCPv6 mechanism where an ISP gives a router a block of IPv6 addresses to distribute.

Used in RFC 3769 RFC 3904 RFC 4057 RFC 4241 RFC 5558 RFC 5571 RFC 5720 RFC 6204 RFC 6276 RFC 6603 RFC 6653 RFC 6853 RFC 7084 RFC 7368 RFC 7788 RFC 7849 RFC 7955 RFC 8168 RFC 8415 RFC 8992 RFC 9096 RFC 9243 RFC 9762 RFC 9818 and 1 more

Part of an IPv6 Router Advertisement message that specifies a network prefix and its associated lifetime values, used by hosts to autoconfigure addresses.

Plain language Part of an IPv6 Router Advertisement specifying a network prefix and its lifetime.

Used in RFC 2462 RFC 4941 RFC 8978 RFC 8981 RFC 9762

The number of leading bits of an IP address that identify the network, written as a small number such as 24 or 32. The remaining bits identify hosts inside that network.

Plain language How many bits at the start of an address name the network. The rest of the address names the machine inside it.

Used in RFC 4098 RFC 6177 RFC 7421 RFC 8344

The shared secret that the key exchange produces in a TLS handshake. TLS then uses it to compute the master secret, from which the session keys are derived.

Plain language The shared secret produced by key exchange that becomes the basis for session keys.

Used in RFC 2246 RFC 4279 RFC 4492 RFC 6101 RFC 8422

Information about whether an entity is currently available for communication. In XMPP it is carried by the presence stanza and sent to everyone subscribed to it.

Plain language Information about whether an entity is currently available for communication.

Used in RFC 2778 RFC 2779 RFC 3343 RFC 3428 RFC 3680 RFC 3693 RFC 3856 RFC 3857 RFC 3858 RFC 3859 RFC 3860 RFC 3861 RFC 3862 RFC 3863 RFC 3903 RFC 3920 RFC 3922 RFC 3923 RFC 3953 RFC 3994 RFC 4079 RFC 4119 RFC 4235 RFC 4245 and 59 more

The server-side entity that stores a user's presence information and sends it to authorized subscribers in notifications.

Plain language A server that stores a user's online status and sends it to authorized subscribers.

Used in RFC 3856 RFC 5263

An approval by a user that lets another entity see whether the user is available. It persists across sessions until the contact unsubscribes or the user cancels it.

Plain language Permission allowing another entity to see whether a user is available.

Used in RFC 3921 RFC 6121

A pairing of an abstract syntax (what the data means) and a transfer syntax (how it is encoded on the wire). Multiple presentation contexts can be negotiated during connection setup.

Plain language An agreement between two systems about what kind of data they are sending and how it is encoded.

Used in RFC 1085 RFC 1698

An identifier that a server presents to a client inside its certificate. A certificate can hold several, and the client compares each reference identifier against them.

Used in RFC 6125 RFC 9525

The entity whose presence information is published and shared, such as a user. A presence user agent publishes on its behalf.

Plain language The entity whose presence information is published, such as a user.

Used in RFC 2778 RFC 3856 RFC 3859 RFC 3863 RFC 3953 RFC 4479 RFC 4480 RFC 4481 RFC 4482 RFC 5196 RFC 5263 RFC 5264 RFC 5344 RFC 5962

A mathematical group where the number of elements is a prime number. FROST uses prime-order groups to ensure that scalar multiplication and other operations have desirable cryptographic properties.

Used in RFC 9496 RFC 9591

A uniquely named client or service in Kerberos, identified by a realm and one or more name components, such as a user or a host service.

Plain language A uniquely named client or service in Kerberos, identified by a realm and name components.

Used in RFC 1510 RFC 1964 RFC 2078 RFC 2261 RFC 2623 RFC 2712 RFC 2743 RFC 2744 RFC 2778 RFC 2853 RFC 3007 RFC 3411 RFC 3744 RFC 4120 RFC 4430 RFC 4791 RFC 5178 RFC 5179 RFC 5397 RFC 5588 RFC 5590 RFC 5591 RFC 5592 RFC 6065 and 18 more

The 3-bit field in an IEEE 802.1Q VLAN tag that carries the priority of a frame. The RFC uses it to identify traffic that should receive the same treatment, and a value of zero is a valid priority.

Plain language A small number in the Ethernet tag that says how important the frame is.

Used in RFC 9892 RFC 9895

A design for secure electronic mail that uses public key certificates, as defined in RFC 1421 and RFC 1422. The directory was proposed as the place to hold those certificates.

Plain language A design for encrypted and signed electronic mail that relies on public key certificates to say who sent a message.

Used in RFC 1430 RFC 1505 RFC 7468

A logical role played by a network intermediary that performs privacy functions on messages, such as hiding identifying headers, which user agents cannot do themselves.

Used in RFC 3323 RFC 7044

An IP address from a block reserved for use inside organizations and not routed on the public Internet. RFC 1918 reserves 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.

Plain language An IP address from a reserved block used inside organizations and not routed on the public Internet.

Used in RFC 1335 RFC 1597 RFC 1627 RFC 1631 RFC 1687 RFC 1814 RFC 1918 RFC 2050 RFC 2101 RFC 2267 RFC 2663 RFC 2685 RFC 2735 RFC 2764 RFC 2767 RFC 2775 RFC 2993 RFC 3022 RFC 3024 RFC 3027 RFC 3056 RFC 3102 RFC 3103 RFC 3235 and 49 more

A number that IANA assigns to an organization so that it can be identified in protocol identifiers. Assignments can be requested from IANA.

Plain language A number IANA assigns to an organization for use in protocol identifiers.

Used in RFC 5792 RFC 6929 RFC 9039 RFC 9997

A trusted server in an identity-based encryption system that holds a master secret. After authenticating a user, it calculates and returns that user's private key.

Plain language A trusted server in identity-based encryption that authenticates users and calculates their private keys.

Used in RFC 5091 RFC 5408 RFC 5409 RFC 6539

A routing approach in which routers regularly exchange topology information so that routes to all destinations are already known when needed. This avoids waiting for a route discovery before sending data.

Plain language A routing approach where routers maintain current routes to all destinations in advance.

Used in RFC 3626 RFC 7181

In mDNS, the step before claiming a name in which a host sends three queries 250 ms apart asking whether anyone else already uses it. If none answers, it announces the name; if one does, it picks a different name.

Plain language Checking repeatedly before claiming a local network name to avoid conflicts.

Used in RFC 6762

A named definition in a grammar. In ABNF it has the form name = elements, and the name can then be used inside other rules.

Plain language A named definition in a grammar such as name = elements in ABNF.

Used in RFC 5234

A setting in which a network interface accepts all frames it can see on the medium, not only those addressed to it. Monitoring tools use it to silently watch traffic.

Plain language A network interface setting that accepts all frames on the medium, not just those addressed to it.

Used in RFC 1229 RFC 1470 RFC 3635

A demonstration, such as signing a value or decrypting one, that a requester controls the private key matching the public key it wants certified.

Plain language A demonstration such as signing or decrypting a value to prove control of a private key.

Used in RFC 2510 RFC 2797 RFC 2875 RFC 4210 RFC 4211 RFC 5272 RFC 6717 RFC 6955 RFC 7030 RFC 7800 RFC 8705 RFC 8747 RFC 9148 RFC 9200 RFC 9202 RFC 9203 RFC 9431 RFC 9483 RFC 9594 RFC 9810 RFC 9883 RFC 10002 RFC 10004

The entry-level standards-track maturity level: stable and reviewed, but not yet proven by interoperable implementations.

Plain language An entry-level standards-track maturity level: stable and reviewed but not yet proven by implementations.

Used in RFC 1100 RFC 1140 RFC 1160 RFC 1264 RFC 1410 RFC 1500 RFC 1540 RFC 1600 RFC 1602 RFC 1610 RFC 1780 RFC 1796 RFC 1880 RFC 2000 RFC 2005 RFC 2017 RFC 2026 RFC 2158 RFC 2160 RFC 2200 RFC 2221 RFC 2232 RFC 2241 RFC 2244 and 93 more

A credential handed to a peer for faster later authentication. It holds a shared secret, an opaque element the server can read, and optional extra information.

Plain language A credential given to a peer for faster later authentication.

Used in RFC 4851 RFC 5422 RFC 7170

One end-to-end path from the ingress to the egress of a recovery graph, along which packets can be forwarded to provide reliability through redundancy.

Used in RFC 9912 RFC 9914

The automatic transfer of traffic from a primary path to a backup path in response to a failure, degradation, or operator command.

Plain language Automatically transferring traffic from a failed primary path to a backup path.

Used in RFC 3386 RFC 3469 RFC 6372 RFC 6378 RFC 6689 RFC 7271 RFC 7347 RFC 8234

An article in the form a posting agent offers to an injecting agent. It may leave out some headers that the injecting agent will supply.

Used in RFC 5536 RFC 5537

A formal set of rules and procedures that govern how data is transmitted and received between systems on a network, such as TCP for reliable communication or IP for packet delivery.

Plain language A formal set of rules governing how data is transmitted and received between systems.

Used in RFC 1292 RFC 1310

The unit of message a protocol sends, made up of a header and usually some data. iSCSI uses the term for each message exchanged between initiator and target.

Plain language The message unit a protocol sends, consisting of a header and data.

Used in RFC 1441 RFC 1905 RFC 3720 RFC 5046

A feature or capability added to a protocol to provide new functionality while maintaining compatibility with the original protocol specification.

Plain language A feature added to a protocol to provide new functionality while maintaining compatibility.

Used in RFC 1785 RFC 7451 RFC 8170

A formal description in RMON of a network protocol, including its address format, how it is recognized on the wire, and which protocol types can appear inside it.

Used in RFC 2896 RFC 3919

A family of multicast routing protocols with Sparse Mode, Dense Mode and Bidirectional variants.

Plain language A family of multicast routing protocols for sending one message to many receivers efficiently.

Used in RFC 2105 RFC 2187 RFC 2375 RFC 2934 RFC 3973 RFC 4610 RFC 5186 RFC 5496 RFC 6037 RFC 6395 RFC 6754 RFC 6826 RFC 7246 RFC 7431 RFC 8059 RFC 9128 RFC 9436

A multicast routing protocol designed for networks where senders and receivers are sparsely distributed. PIM-SM uses a Rendezvous Point to discover sources and builds multicast distribution trees on demand.

Plain language A multicast routing protocol for networks where senders and receivers are spread out.

Used in RFC 2934 RFC 4602 RFC 4609 RFC 4610 RFC 5496 RFC 5565 RFC 5757 RFC 5796 RFC 7900

A family of multicast routing protocols whose version 2 messages share a common header with a version, a type, flag bits and a checksum.

Plain language A family of multicast routing protocols with common header structure.

Used in RFC 6513 RFC 7761 RFC 8736

The part of an FTP implementation that sends commands over the TELNET connection and receives replies from the server.

Used in RFC 765 RFC 928

A centrally maintained database that records assigned values for a protocol parameter and documents what each value means, ensuring consistent interpretation across all implementations.

Plain language A centrally maintained database recording assigned values for a protocol parameter.

Used in RFC 6220 RFC 8722

The implementation expectation for a protocol: required (all systems must implement), recommended (systems should implement), elective (optional), or not recommended (discouraged).

Plain language The implementation expectation for a protocol: required, recommended, elective or not recommended.

Used in RFC 901 RFC 1083

The two roles in RFC 6238. The prover (a hardware token or an authenticator app) generates the one-time password. The verifier (the authentication or validation server) recomputes it and checks that it matches.

Plain language The two roles where a prover generates a one-time password and a verifier checks it.

Used in RFC 2944 RFC 6238 RFC 9334 RFC 9683 RFC 9684 RFC 9783

An IEEE 802.1Q technology for wide-area Ethernet that adds fields such as a Backbone VLAN Identifier and a 24-bit Backbone Service Instance Identifier. It separates the service provider and customer identifier spaces.

Used in RFC 7080 RFC 7133

A device at the edge of a service provider's network that connects customer networks to the provider's core.

Plain language A device at the edge of a service provider's network connecting customer networks.

Used in RFC 3769 RFC 3916 RFC 3985 RFC 4026 RFC 4029 RFC 4031 RFC 4111 RFC 4553 RFC 4664 RFC 4665 RFC 4762 RFC 5085 RFC 5251 RFC 5824 RFC 5921 RFC 6074 RFC 6215 RFC 6310 RFC 6624 RFC 6658 RFC 6870 RFC 7023 RFC 7117 RFC 7152 and 14 more

A router at the edge of a service provider's network that attaches to customer sites and holds the per-customer VPN routing tables. It is often shortened to PE.

Plain language A router at the edge of a service provider's network connecting to customer sites.

Used in RFC 2547 RFC 4176 RFC 4381 RFC 4577 RFC 4798 RFC 6513 RFC 7582

A name chosen by an ALTO server for a group of IPv4 and IPv6 addresses in a network map. The same PID name can mean different address sets in different network maps.

Plain language A name an ALTO server assigns to a group of addresses in a network map.

Used in RFC 7285 RFC 8895 RFC 9240

Address space assigned to an end site that does not come from an ISP's allocation. It lets the site change providers without renumbering, but it cannot be aggregated into a provider's prefix.

Plain language Address space not from an ISP that lets a site change providers without renumbering.

Used in RFC 4984 RFC 5902 RFC 9284

A type of policy data that defines a configuration object, with attributes and rules for how instances of that class should be interpreted by a device.

Plain language A policy data type defining a configuration object and how instances should be interpreted.

Used in RFC 3159 RFC 3318

A consistent set of network configuration information (DNS servers, gateways, source prefixes) that belongs together and is used for making routing and connectivity decisions.

Plain language A consistent set of network configuration that belongs together for routing decisions.

Used in RFC 6418 RFC 7556 RFC 8043 RFC 8801

A server that sits between a client and an origin server and forwards requests on the client's behalf. In HTTP a proxy can demand its own authentication with status 407.

Plain language A server between a client and origin server that forwards requests on the client's behalf.

Used in RFC 1905 RFC 1919 RFC 1928 RFC 1929 RFC 1941 RFC 1961 RFC 2138 RFC 2186 RFC 2187 RFC 2193 RFC 2196 RFC 2221 RFC 2227 RFC 2273 RFC 2295 RFC 2571 RFC 2573 RFC 2576 RFC 2577 RFC 2594 RFC 2607 RFC 2617 RFC 2647 RFC 2663 and 145 more

A mobility scheme in which the network, rather than the device, handles movement. A Mobile Access Gateway signals to a Local Mobility Anchor on the device's behalf.

Plain language A mobility scheme where the network handles movement instead of the device.

Used in RFC 5149 RFC 5213 RFC 5779 RFC 5845 RFC 6097 RFC 6279 RFC 6463 RFC 6572 RFC 6757 RFC 7028 RFC 7156 RFC 7561 RFC 7847 RFC 8278

Packet Sampling, a protocol that extends IPFIX by transferring information on individual packets. A set of sampling and filtering techniques for IP packet selection is specified separately, based on the PSAMP Framework.

Plain language The IPFIX extension that reports on individual sampled packets rather than on whole flows.

Used in RFC 5475 RFC 6632

An emulated point-to-point connection over a packet switched network that allows two nodes to be interconnected with any L2 technology. It joins two provider edge devices.

Plain language An emulated point-to-point connection over a packet network using any L2 technology.

Used in RFC 3916 RFC 3985 RFC 4026 RFC 4665

A set of IPv6 header fields, including the source and destination addresses and the Next Header value, that is included when computing the ICMPv6 checksum but is not sent as part of the ICMPv6 message itself.

Plain language A set of IPv6 fields used in ICMPv6 checksum calculation but not sent in the message.

Used in RFC 64 RFC 768 RFC 1010 RFC 1180 RFC 1347 RFC 1883 RFC 2385 RFC 2463 RFC 2675 RFC 2682 RFC 3242 RFC 3545 RFC 3715 RFC 3828 RFC 4443 RFC 4504 RFC 4981 RFC 5925 RFC 6145 RFC 6235 RFC 6296 RFC 6935 RFC 6936 RFC 7276 and 9 more

A special HTTP/2 field whose name starts with a colon, such as :method or :status. It carries the information that HTTP/1.1 puts in the request line or status line.

Plain language A special HTTP/2 field starting with a colon such as :method carrying request-line information.

Used in RFC 7541 RFC 9113 RFC 9220 RFC 9292

A single nickname that stands for a whole edge group of RBridges, so remote RBridges see one source for the group instead of several.

Plain language A single nickname for an entire edge group so remote devices see one source.

Used in RFC 7781 RFC 8361

An algorithm that turns a short seed into a long sequence of numbers that look random. Ordinary ones are fully predictable once the state is known, so security uses need cryptographically strong generators started from a seed with enough entropy.

Plain language An algorithm turning a short seed into a long sequence of seemingly random numbers.

Used in RFC 1750 RFC 2437 RFC 2680 RFC 2777 RFC 2943 RFC 4056 RFC 4086 RFC 4122 RFC 4432 RFC 4537 RFC 4814 RFC 5083 RFC 5475 RFC 5832 RFC 6056 RFC 6436 RFC 6979 RFC 7022 RFC 7091 RFC 8419 RFC 8682 RFC 8778 RFC 8937 RFC 8954 and 4 more

A software imitation of a text terminal that lets a remote program behave as though a person were typing at a real screen and keyboard. An SSH client asks for one with the pty-req request.

Plain language Pseudo-terminal: a software terminal letting a remote program behave as if someone is at a keyboard.

Used in RFC 4254 RFC 8160

A virtual node that represents a shared LAN in link state routing, so that each router reports one adjacency to it instead of one to every neighbor.

Plain language A virtual node representing a shared LAN in link state routing.

Used in RFC 1142 RFC 3784 RFC 3787 RFC 5309 RFC 6138 RFC 6327 RFC 7177

An identifier used in place of a real identity. It is a unique bit string that can be used for authentication without revealing who the holder is.

Plain language An identifier used instead of a real identity for authentication without revealing identity.

Used in RFC 3693 RFC 4186 RFC 4187 RFC 6973 RFC 9048 RFC 9614

A keyed function whose output looks random. IKE uses a negotiated PRF to turn nonces and a shared secret into SKEYSEED and then into all other keys.

Plain language A keyed function whose output appears random, used in IKE for key derivation.

Used in RFC 2246 RFC 2412 RFC 2857 RFC 2898 RFC 3830 RFC 3961 RFC 4109 RFC 4306 RFC 4346 RFC 4357 RFC 4383 RFC 4401 RFC 4402 RFC 4418 RFC 4434 RFC 4615 RFC 5191 RFC 5288 RFC 5289 RFC 5295 RFC 5448 RFC 5705 RFC 5723 RFC 5869 and 21 more

An emulated connection carried across a packet network, here over MPLS. It is one kind of transport path that can be locked.

Plain language An emulated connection carried across a packet network over MPLS.

Used in RFC 3931 RFC 4349 RFC 4385 RFC 4446 RFC 4447 RFC 4448 RFC 4454 RFC 4553 RFC 4591 RFC 4618 RFC 4619 RFC 4623 RFC 4664 RFC 4667 RFC 4717 RFC 4719 RFC 4720 RFC 4761 RFC 4762 RFC 4842 RFC 4863 RFC 4901 RFC 5003 RFC 5085 and 87 more

A label sent by a TLS client, in the clear, that tells the server which pre-shared key it wants to use. Because the client chooses it, the server must treat it as untrusted input.

Used in RFC 7925 RFC 9813

The Public Switched Telephone Network, the circuit-switched telephone system. Gateways connect it to packet networks such as the Internet.

Plain language Public Switched Telephone Network: the traditional circuit-switched telephone system.

Used in RFC 2848 RFC 2995 RFC 3136 RFC 3191 RFC 3192 RFC 3372 RFC 3398 RFC 3666 RFC 3976 RFC 4190 RFC 4733 RFC 4734 RFC 7195 RFC 7875 RFC 8816

A DNS resource record that maps an IP address (in reverse format) to a hostname. PTR records enable reverse DNS lookups.

Plain language A DNS record mapping an IP address to a hostname in reverse format.

Used in RFC 1101 RFC 1912 RFC 2317 RFC 4183 RFC 4702 RFC 4704 RFC 5158 RFC 6763 RFC 7001 RFC 7534

A text string used in SGML and XML to globally name a DTD or external entity, as opposed to a system identifier which is local. Public identifiers are persistent, global names.

Used in RFC 3151 RFC 6461

A way of using a pair of keys: a private key kept secret and a public key shared freely. A signature made with the private key can be checked by anyone with the public key.

Plain language A system using a pair of keys where the private key is secret and the public key is shared.

Used in RFC 989 RFC 1040 RFC 1113 RFC 1114 RFC 1170 RFC 1186 RFC 1319 RFC 1321 RFC 1412 RFC 1421 RFC 1422 RFC 1423 RFC 1424 RFC 1507 RFC 1508 RFC 1636 RFC 1704 RFC 1750 RFC 1751 RFC 1824 RFC 1825 RFC 1828 RFC 1848 RFC 1852 and 339 more

The emergency call center that receives 911 or emergency calls and dispatches responders.

Plain language Public Safety Answering Point: the emergency call center answering 911-style calls.

Used in RFC 5012 RFC 5069 RFC 5222 RFC 5582 RFC 6443 RFC 6444 RFC 6451 RFC 6739 RFC 6881 RFC 7135 RFC 7378 RFC 7840 RFC 8147 RFC 8148 RFC 8876 RFC 9027

The call center that answers emergency calls and dispatches or forwards them to the right responders. It is abbreviated PSAP.

Plain language The call center answering emergency calls and dispatching responders.

Used in RFC 7406 RFC 7852

A domain controlled by a public registry, such as com, co.uk or pvt.k12.wy.us, under which anyone can register names. Browsers use a list of them to refuse cookies that claim to cover a whole suffix.

Plain language A domain controlled by a public registry such as .com or .co.uk.

Used in RFC 6265 RFC 8473 RFC 9091 RFC 9989

A repository directory containing all signed objects (certificates, CRLs, ROAs, manifests) published by a RPKI certification authority.

Plain language A repository containing all signed objects published by a RPKI certification authority.

Used in RFC 6481 RFC 6486 RFC 9286

A messaging pattern where receivers sign up for the data they want and a publisher pushes updates to them, instead of receivers asking repeatedly.

Plain language A messaging pattern where receivers subscribe for data and publishers push updates.

Used in RFC 3920 RFC 7922 RFC 7923 RFC 8600 RFC 9431 RFC 9437

A way of writing any Unicode string using only ASCII letters, digits and hyphens, defined as Bootstring with fixed parameters. It is used to store internationalized domain labels in the DNS.

Plain language A way to write Unicode strings using only ASCII letters, digits and hyphens.

Used in RFC 3490 RFC 3491 RFC 3492 RFC 3722 RFC 3743 RFC 3982 RFC 3987 RFC 4185 RFC 4290 RFC 4690 RFC 4713 RFC 4952 RFC 5137 RFC 5483 RFC 5890 RFC 5891 RFC 5892 RFC 5893 RFC 5894 RFC 5895 RFC 6055 RFC 6068 RFC 6365 RFC 6672 and 12 more

The address of the party that a message's headers say most recently introduced the message into the mail system, found by looking for the first usable Resent-Sender, Resent-From, Sender or From header. The word purported warns that the headers themselves may be false.

Plain language The address the message claims belongs to whoever last passed it on, worked out from the headers.

Used in RFC 4406 RFC 4407

A service that delivers push messages from application servers to user agents. It holds one connection to the device and passes events along as they arrive.

Plain language A service delivering push messages from application servers to user devices.

Used in RFC 8030 RFC 8291 RFC 8641