Glossary
B
80 terms.
- B2BUA
Back-to-back user agent. A SIP element that acts as a server toward one side and as a client toward the other, sitting in the call path as a PBX or session border controller does.
Like I'm five A go-between who takes your call and then makes a second call on your behalf.
Used in RFC 3261 RFC 3323 RFC 3325 RFC 3665 RFC 3725 RFC 4354 RFC 4964 RFC 5079 RFC 5318 RFC 5359 RFC 5362 RFC 5363 RFC 5365 RFC 5369 RFC 5370 RFC 5503 RFC 5606 RFC 5630 RFC 5707 RFC 5853 RFC 6086 RFC 6230 RFC 6442 RFC 6714 and 28 more
- Backbone area
OSPF Area 0 (0.0.0.0). Other areas connect to it, and traffic between areas passes through it.
Like I'm five The main hub that all the districts connect to.
Used in RFC 1131 RFC 1167 RFC 1247 RFC 1253 RFC 1583 RFC 1584 RFC 2178 RFC 2328 RFC 2370 RFC 3101 RFC 3509 RFC 4577 RFC 4750 RFC 4915 RFC 5088 RFC 5185 RFC 7524 RFC 9084
- Backhaul
The network connection from an edge node (such as a cellular base station or remote access point) back to the core network, typically using wired or wireless links like microwave radio.
Like I'm five The connection that carries traffic from a base station back to the main network.
- Backward compatibility
The ability of an extension to work correctly with older implementations that do not know about it, or to degrade gracefully when such implementations encounter it.
Like I'm five Old systems can still work even if they don't understand the new feature.
- BAD cache
An optional resolver cache of data that failed DNSSEC validation, kept with a small TTL so persistent failures do not trigger endless re-queries.
Like I'm five A list of answers that failed the seal check, so you stop asking again right away.
- Bandwidth Constraint
A configurable limit on how much bandwidth the Class-Types it applies to may reserve on a link. DS-TE allows up to 8 of them per link, named BC0 to BC7.
Like I'm five A limit on how much of the road a group of traffic may use.
- Bandwidth-delay product
The link's data rate multiplied by its round-trip time. It is the amount of data that can be in flight on a path at once, so a large value means a fast, long-distance path.
Like I'm five How much water fits in a pipe, based on how wide and how long it is.
Used in RFC 1072 RFC 1185 RFC 3135 RFC 3481 RFC 6077 RFC 7323 RFC 9438 RFC 9959
- Base16
Hexadecimal encoding, where each byte becomes two characters from 0-9 and A-F. It doubles the size of the data but is easy to read.
Like I'm five Writing every byte as two digit-and-letter characters so you can read it.
Used in RFC 3548 RFC 4425 RFC 4648 RFC 6920 RFC 7433 RFC 7434 RFC 8610 RFC 9741
- Base32
An encoding that writes data using 32 characters (A-Z and 2-7), five bits at a time, with = padding to a multiple of 8 characters. It avoids lowercase letters and easily confused digits.
Like I'm five A shorter alphabet for writing bytes down, with no lowercase letters to mix up.
Used in RFC 2938 RFC 3548 RFC 4648 RFC 5155 RFC 5801 RFC 9741
- Base64
An encoding that turns every 3 octets into 4 printable characters from a 64-character alphabet, padding with = at the end. It makes data about 33 percent larger.
Like I'm five Spelling anything using only 64 safe letters and symbols.
Used in RFC 1341 RFC 1342 RFC 1421 RFC 1489 RFC 1494 RFC 1521 RFC 1522 RFC 1544 RFC 1554 RFC 1555 RFC 1557 RFC 1641 RFC 1740 RFC 1767 RFC 1844 RFC 1847 RFC 1848 RFC 1864 RFC 1947 RFC 2015 RFC 2045 RFC 2047 RFC 2048 RFC 2049 and 124 more
- Base64 Encoding
An encoding scheme that represents binary data using only 64 printable ASCII characters (A-Z, a-z, 0-9, +, /), commonly used in MIME for safe transmission.
Like I'm five A way to write any data using only letters and numbers so it survives email systems.
- base64url
A URL-safe variant of Base64 from RFC 4648 using a different alphabet. DoH GET requests use it with the padding characters left out.
Like I'm five A way of writing any bytes using only letters, numbers and two symbols that are safe inside a web address.
Used in RFC 4648 RFC 6920 RFC 7493 RFC 7515 RFC 7516 RFC 7517 RFC 7518 RFC 7519 RFC 7520 RFC 7522 RFC 7636 RFC 7638 RFC 7797 RFC 7951 RFC 8037 RFC 8188 RFC 8225 RFC 8292 RFC 8428 RFC 8473 RFC 8474 RFC 8484 RFC 8555 RFC 8620 and 18 more
- BCP (Best Current Practice)
A subseries of RFCs recording community consensus on operational practice or IETF process, approved by the IESG after a Last-Call.
Like I'm five A written agreement about the best way to do something, rather than a technical gadget spec.
Used in RFC 1818 RFC 1915 RFC 2008 RFC 2014 RFC 2026 RFC 2028 RFC 2119 RFC 2148 RFC 2182 RFC 2219 RFC 2223 RFC 2277 RFC 2317 RFC 2360 RFC 2379 RFC 2505 RFC 2506 RFC 2606 RFC 2727 RFC 2827 RFC 2850 RFC 2870 RFC 2939 RFC 2978 and 130 more
- Bearer
A physical or logical link, wired or wireless, that connects a customer edge or site to a provider network. One or more attachment circuits may be hosted over the same bearer.
Like I'm five The actual cable or wireless link, which can carry several connections at once.
- Bearer token
A security token that works for whoever holds it. The server does not ask the holder to prove who they are or to show a secret key, so the token must be kept private and sent only over protected connections.
Like I'm five A ticket that lets in anyone who holds it, so you guard it.
Used in RFC 6749 RFC 6750 RFC 6819 RFC 7235 RFC 7519 RFC 7521 RFC 7522 RFC 7523 RFC 7591 RFC 7592 RFC 7628 RFC 7644 RFC 7662 RFC 7846 RFC 8030 RFC 8471 RFC 8473 RFC 8485 RFC 8495 RFC 8628 RFC 8693 RFC 8705 RFC 8707 RFC 8747 and 13 more
- BEEP
The Blocks Extensible Exchange Protocol, a framework in which peers exchange messages over numbered channels, each channel using a profile that defines its message types.
Like I'm five A way for two computers to hold several separate conversations over one connection, each with its own set of rules.
Used in RFC 3529 RFC 3620 RFC 3767 RFC 3983 RFC 4227 RFC 4744
- BEEP profile
A named definition of how an application protocol uses a BEEP channel. Each profile is identified by a URI.
Like I'm five The rulebook for one particular game played over a shared line, with its own name.
- Behavior Aggregate
All the packets crossing a link that need the same Diff-Serv behavior. They are marked with the same Diff-Serv code point at the edge of the domain.
Like I'm five A group of packets that all get the same kind of treatment.
- BER encoding
The Basic Encoding Rules, a standard way of turning ASN.1 data into bytes. X.500 directories use it, and LDAP can use it for attribute values when asked.
Like I'm five A strict way of packing information into bytes so any computer can unpack it the same way.
- Best Current Practice
A category of RFC documents that provide guidance and recommendations for internet operations, rather than specifying a protocol. Abbreviated BCP.
Like I'm five Guidelines on the best way to do something on the internet, like a how-to guide.
- Best-effort delivery
A service model in which the network tries to deliver each packet but promises neither delivery, order nor timing. IP works this way, which is why RFC 1149 can say that loss of a carrier can be tolerated.
Like I'm five The mail carrier will try hard, but may lose a letter and will not say sorry.
Used in RFC 768 RFC 791 RFC 1149 RFC 1633 RFC 1755 RFC 2205 RFC 2211 RFC 2212 RFC 2213 RFC 2331 RFC 2379 RFC 2380 RFC 2381 RFC 2501 RFC 2597 RFC 2688 RFC 2702 RFC 2736 RFC 2814 RFC 2815 RFC 2914 RFC 2998 RFC 3086 RFC 3366 and 12 more
- Best-effort service
A network service model that treats all packets equally and makes no guarantees about delivery, latency, or reliability; each packet is forwarded on a best-effort basis.
Like I'm five The network tries its best to deliver your data, but makes no promises about whether it will arrive or how fast.
- BFD discriminator
A number used to identify a Bidirectional Forwarding Detection session or reflector endpoint. In S-BFD, nodes must know the discriminators reserved by other nodes, and they must be unique within an administrative domain.
Like I'm five A number that says which exact checker you are talking to.
- BGP
Border Gateway Protocol: the exterior routing protocol that networks use to exchange reachability for prefixes. Version 4 carries prefix lengths and so supports CIDR.
Like I'm five The way big networks tell each other which neighborhoods they can reach.
Used in RFC 923 RFC 1093 RFC 1102 RFC 1105 RFC 1125 RFC 1163 RFC 1164 RFC 1222 RFC 1265 RFC 1266 RFC 1267 RFC 1268 RFC 1269 RFC 1299 RFC 1322 RFC 1364 RFC 1371 RFC 1380 RFC 1397 RFC 1403 RFC 1467 RFC 1476 RFC 1478 RFC 1482 and 474 more
- BGP Capability
An optional feature that a BGP speaker announces when a session starts. Each side learns what the other supports before using the feature.
Like I'm five A router saying 'here is what I can do' before the two start talking.
- BGP community
A label attached to a BGP route that routers can match in policy to decide how to accept, filter or distribute it.
Like I'm five A sticker on a route announcement that tells routers how to treat it.
Used in RFC 1998 RFC 3765 RFC 3882 RFC 4360 RFC 4384 RFC 7454 RFC 7611 RFC 7999 RFC 8092 RFC 8549 RFC 8642 RFC 9494
- BGP Confederation
A collection of autonomous systems that operates internally as multiple ASs but presents itself to external routers as a single AS, identified by a Confederation Identifier in the AS_PATH.
Like I'm five A group of routers that act like one network on the outside but have separate identities inside.
- BGP Extended Community
A tag attached to a BGP route announcement that carries extra information, such as flags. Its type and sub-type codes are tracked in IANA registries.
Like I'm five An extra sticker on a message that carries more information.
- BGP Link State
An extension of BGP, often shortened to BGP-LS, that carries link-state and traffic engineering information to external components such as controllers.
Like I'm five A way for routers to share their map with a central planner using a messaging system they already have.
- BGP Monitoring Protocol
A protocol that lets a router send copies of its BGP routing data to a monitoring station, so operators can watch routes without being a BGP peer.
Like I'm five A way for a router to tell a watcher what routes it knows.
- BGP-LS
Border Gateway Protocol - Link State, an extension that carries link-state topology information in BGP using Node, Link and Prefix NLRI types.
Like I'm five A way for routers to hand their network map to a planner.
- BGPsec
An extension to BGP in which routers digitally sign the routing announcements they send, so that receivers can verify them with public keys published in the RPKI.
Like I'm five A way for routers to sign their messages so others can tell they are real.
- Bidding-down attack
An attack in which a man-in-the-middle manipulates a negotiation so that both sides use a weaker mechanism than the strongest one they both support.
Like I'm five A trickster convinces two people to use the flimsy lock even though they both have a strong one.
- Bidirectional Forwarding Detection
A protocol that lets two routers detect a failure of the forwarding path between them. It is abbreviated BFD and defined in RFC 5880.
Like I'm five A quick back-and-forth check that tells two routers whether the road between them still works.
Used in RFC 5880 RFC 5994 RFC 6213 RFC 7487 RFC 7880 RFC 8562 RFC 8564 RFC 8971 RFC 9026 RFC 9127 RFC 9247 RFC 9314 RFC 9355 RFC 9468 RFC 9612 RFC 9634 RFC 9780 RFC 9978 RFC 9986
- Bidirectional Forwarding Detection
A lightweight protocol in which two neighbors exchange frequent packets to detect quickly that the path between them has failed.
Like I'm five Two neighbors keep waving at each other so that they notice quickly when one stops.
Used in RFC 5881 RFC 5884 RFC 6428 RFC 7175 RFC 7331 RFC 7419 RFC 7726 RFC 7885 RFC 8563 RFC 9186 RFC 9521 RFC 9764
- Bidirectional text
Text that mixes left-to-right and right-to-left content on the same line, such as Hebrew words mixed with English in a single sentence.
Like I'm five A sentence that has some words that read left-to-right and some that read right-to-left.
- BIER
Bit Index Explicit Replication, a multicast forwarding architecture that needs no explicit tree-building protocol and no per-tree multicast state in intermediate routers.
Like I'm five A way to send one message to many receivers by listing who should get it, instead of building a delivery map.
Used in RFC 8296 RFC 8444 RFC 8556 RFC 9272 RFC 9624 RFC 9793
- Big-endian
A way of writing a multi-byte number with the most significant byte first. It is also called network order.
Like I'm five Writing a number starting with the biggest part, like writing 1,200 as one thousand first.
Used in RFC 1014 RFC 1761 RFC 1832 RFC 3072 RFC 4194 RFC 4506 RFC 6234 RFC 8010
- Bilinear pairing
A mathematical map on elliptic curve points that is linear in both of its inputs and efficiently computable. It is believed hard to invert and underlies identity-based encryption schemes.
Like I'm five A special kind of math mixing that is easy to do one way and very hard to undo.
- Binding
The association between a mobile node's home address and its current care-of address, registered with a correspondent node to enable direct communication.
Like I'm five A note that says 'send mail for Alice to this new address while she is traveling'.
- Binding anchor
A layer-2 attribute, such as a switch port, that is tied to an IP address so a device can tell which attachment point may legitimately use that address as a source.
Like I'm five The seat number that goes with a name on the list.
- Binding cache
A table kept by home agents and correspondent nodes that maps a mobile node's home address to its current care-of address, along with how long the entry remains valid.
Like I'm five A notebook that says which hotel each traveling friend is staying at.
- Binding Cache Entry
A record maintained by a mobility anchor that maps a mobile node's home address to its current care-of address and associated forwarding tunnels.
Like I'm five The network's address book entry that remembers where your device is currently located.
- Binding SID
A SID bound to an SR Policy. A packet that arrives carrying it is steered into the policy, so the whole segment list is attached from one value.
Like I'm five A shortcut ticket that stands for a whole list of stops.
- Binding Update
A message sent by a mobile node to its home agent to register or refresh its current location (care-of address).
Like I'm five A message the phone sends to say 'I am here now at this network'.
Used in RFC 3963 RFC 4260 RFC 4487 RFC 5149 RFC 5555 RFC 5648
- Birds of a Feather (BOF)
A session at an IETF meeting used to explore whether an issue merits a working group. It allows market research and technical brainstorming.
Like I'm five A trial meeting to see whether enough people care about an idea to start a team.
- Birthday attack
An attack that exploits the birthday paradox: when many identical queries are outstanding, a forged reply only has to match any one of them. This raises its chance of success.
Like I'm five With lots of locks to try, you only need your key to fit one of them.
- Bit Index Forwarding Table
The table a BIER router uses to forward BIER packets. It is derived from the unicast forwarding table by adding BIER-specific information.
Like I'm five The router's cheat sheet for where to send each BIER packet next.
- Bit mask
A string of bits in which each bit position stands for one item or option. A bit set to 1 selects that item, and a bit set to 0 leaves it out.
Like I'm five A row of on-off switches where each switch stands for one choice.
- Bit-String Label
A DNS label type that compactly holds a sequence of up to 256 One-Bit Labels, so records can be stored at any bit boundary.
Like I'm five A single DNS label that holds a whole row of 0s and 1s.
- Bit-stuffing
Inserting an extra bit into a data stream so that data is not mistaken for a control sequence. In PPP with HDLC-like framing, a 0 bit goes after five contiguous 1 bits.
Like I'm five Adding a spacer so a piece of data cannot look like a stop sign.
- Black-hole
A routing failure in which packets for a destination are sent towards a router that has no working route for them, so they are lost instead of delivered.
Like I'm five A road that leads nowhere, so everything sent down it disappears.
- Blind signature
A digital signature on data that the signer does not see, created by using cryptographic blinding to encrypt the data before signing and then removing the encryption from the signature.
Like I'm five Signing something sealed in an envelope so you cannot read what you are signing.
- Blob
A chunk of immutable binary data, such as an attachment, referred to by an id. The id stands only for the bytes, not for a file name or content type.
Like I'm five A sealed package you can point to by number, without caring what is written on the outside.
- Block cipher
An encryption algorithm that works on fixed-size blocks of data using a secret key. Camellia is an example.
Like I'm five A scrambler that handles a message one chunk at a time.
Used in RFC 2268 RFC 2451 RFC 2994 RFC 3713 RFC 4196 RFC 4269 RFC 4312 RFC 5529 RFC 5669 RFC 5794 RFC 5830 RFC 5932 RFC 7253 RFC 7321 RFC 7801 RFC 8891
- Block-wise transfer
A CoAP mechanism that splits a large message into numbered blocks, each sent and acknowledged separately, so that no single packet is too big for the network.
Like I'm five Sending a big parcel as several small boxes, one after another.
- BNF
Backus-Naur Form, an older notation for describing the grammar of a language using named rules. ABNF is a modified version of it.
Like I'm five An old way of writing the rules of a language as a list of named patterns.
Used in RFC 31 RFC 138 RFC 493 RFC 561 RFC 645 RFC 680 RFC 1459 RFC 1630 RFC 1738 RFC 1857 RFC 2088 RFC 2156 RFC 2234 RFC 2360 RFC 4234 RFC 4506 RFC 5234 RFC 5511 RFC 6510
- BOOTP
The Bootstrap Protocol. Built on UDP and IP, it lets a client learn its IP address and a boot file from a server, and requests can be relayed across routers.
Like I'm five A better version of shouting for your address that can be heard in other buildings.
Used in RFC 903 RFC 950 RFC 951 RFC 1048 RFC 1060 RFC 1084 RFC 1123 RFC 1256 RFC 1350 RFC 1395 RFC 1497 RFC 1531 RFC 1532 RFC 1533 RFC 1534 RFC 1541 RFC 1542 RFC 2131 RFC 2132 RFC 2226 RFC 2827 RFC 3011 RFC 3074 RFC 3527 and 5 more
- Bootstrap
The start-up process of a computer, from power-on to a running operating system. Network bootstrapping adds steps: find an address, then fetch a boot image from a server.
Like I'm five The first small steps a computer takes to wake up and get dressed.
Used in RFC 903 RFC 906 RFC 950 RFC 951 RFC 1123 RFC 1350 RFC 4108 RFC 4578 RFC 5030 RFC 5637 RFC 5694 RFC 5859 RFC 5884 RFC 5970 RFC 6080 RFC 6610 RFC 6611 RFC 6696 RFC 7484 RFC 7890 RFC 8366 RFC 8521 RFC 8572 RFC 8576 and 5 more
- Bootstrap Router
A PIM router elected from among Candidate-BSRs. It collects the Candidate-RP advertisements and distributes the resulting group-to-RP mappings in Bootstrap messages.
Like I'm five The router that wins an election and then tells everyone which helper handles which group.
- Bootstring
A general algorithm that lets a string of basic code points uniquely and reversibly represent any string of code points from a larger set. Punycode is one setting of its parameters.
Like I'm five A recipe for turning any message into one that uses only a small set of symbols.
- Border router
A router that exchanges routing information with other domains using exterior routing protocols like BGP or IDRP, typically at the edge of a network domain.
Like I'm five A router at the edge of a network that talks to the outside world about how to find different destinations.
- Botnet
A collection of compromised machines running software robots under a common command and control infrastructure. Their owners are often unaware of them.
Like I'm five A crowd of hijacked computers that all take orders from one bad guy.
- Boundary Node
A boundary node is a router at the edge of a domain: an area border router between IGP areas, or an AS border router between Autonomous Systems.
Like I'm five A gate where one region of the network meets the next.
- Brainpool Curves
A set of standardized elliptic curve groups generated in a verifiably pseudo-random way and compliant with ISO, ANSI, NIST, and SEC standards, offering an alternative to NIST curves.
Like I'm five A family of math curves made carefully to be trustworthy and follow international standards.
- Bridge
A device that passes packets through with the data field unmodified, usually from one Ethernet segment to another or from Ethernet to token ring.
Like I'm five A connector that hands messages from one network to another without changing them.
- Bridge Protocol Data Unit (BPDU)
A message sent by bridges to exchange spanning tree information, used to elect the root bridge and compute tree topology.
Like I'm five Messages bridges send each other to figure out the tree shape.
- Broadcast
A message sent to every host on a network segment at once. On Ethernet the destination is the all-ones address FF:FF:FF:FF:FF:FF. Routers normally do not forward link-layer broadcasts.
Like I'm five Shouting in a room so everyone in it hears you, but not people in other rooms.
Used in RFC 824 RFC 826 RFC 828 RFC 894 RFC 903 RFC 906 RFC 917 RFC 919 RFC 922 RFC 925 RFC 947 RFC 950 RFC 951 RFC 966 RFC 985 RFC 1001 RFC 1042 RFC 1044 RFC 1057 RFC 1058 RFC 1062 RFC 1070 RFC 1088 RFC 1112 and 110 more
- Broadcast Domain
A network segment where all devices can reach each other with a broadcast frame at the data link layer. Routers separate broadcast domains.
Like I'm five All the devices that hear a broadcast message sent from one device.
- Brute-force attack
An attack that tries every possible key until the right one is found. Its cost grows with the number of possible keys, so each added key bit doubles the work.
Like I'm five Trying every key on the ring until one opens the door.
- Buffer Overflow
A condition where more data arrives than the available memory space can hold, causing data loss or system errors.
Like I'm five When too much stuff arrives at once and the storage space runs out.
- Bufferbloat
A condition where large buffers in network equipment cause excessive queueing delay and poor latency, even when the link has available bandwidth.
Like I'm five When a network device has huge buffers, it lets packets pile up for a long time before rejecting any, making everything feel slow and sluggish.
Used in RFC 7295 RFC 7928 RFC 8034 RFC 8289 RFC 8290 RFC 8337 RFC 9743
- Bundle
In Multi-link PPP, a collection of multiple connections grouped together and reassembled into a single stream at the bundle head.
Like I'm five The combined group of phone lines being used together.
Used in RFC 2701 RFC 4838 RFC 5050 RFC 6927 RFC 9171 RFC 9174
- BUNDLE group
A set of SDP media sections that share a single transport and one set of transport attributes. All RTP-based media in the group belong to one RTP session.
Like I'm five Several streams that agree to travel together on one road.
- Bundle Protocol
The application-layer protocol of Delay-Tolerant Networking. It builds a store-and-forward overlay network that moves messages called bundles.
Like I'm five A way to pass parcels from stop to stop, holding each one until the next road is open.
- Bundled link
A kind of TE link that binds the traffic of a group of one or more TE links into a single subinterface. Its traffic counters are cumulative for everything it binds.
Like I'm five Several roads joined and treated as one big road.
- Bypass tunnel
A pre-built backup LSP that carries traffic around a failed link or node and rejoins the protected path further along.
Like I'm five A ready-made detour road around a blocked section.
- Byte order mark
The character U+FEFF placed at the start of text. Its encoded bytes can signal which Unicode encoding the text uses.
Like I'm five A little sign at the front of a note that says which alphabet it uses.
- Byte stream
The service TCP offers applications: an ordered sequence of bytes with no message boundaries. TCP may split or combine the bytes into segments however it likes.
Like I'm five Water flowing through a pipe: you pour it in and it comes out the other end in the same order, with no marks on it.
Used in RFC 107 RFC 176 RFC 285 RFC 793 RFC 1005 RFC 1006 RFC 1007 RFC 1013 RFC 1057 RFC 1952 RFC 2126 RFC 2398 RFC 2781 RFC 5044 RFC 8673 RFC 8922 RFC 9407 RFC 9621 RFC 9622
- Byte-stuffing
A trick for multi-line replies: a line that begins with the termination period gets an extra period put in front, and the receiver removes it, so a data line is never mistaken for the end marker.
Like I'm five If a story line starts with a full stop, add a second one so nobody thinks the story ended.
Used in RFC 891 RFC 935 RFC 1055 RFC 1331 RFC 1662 RFC 1939 RFC 2171 RFC 2615 RFC 2687 RFC 2688 RFC 4425 RFC 4814