en	Additive Increase, Multiplicative Decrease. A rate adaption algorithm used notably by TCP where a host additively increases its transmission rate when the network is not congested and multiplicatively decreases when congested is detected.

en	a transmission mode where an information is sent from one source to `one` receiver that belongs to a specified group

en	Application Programming Interface

en	ARP

en	The Address Resolution Protocol is a protocol used by IPv4 devices to obtain the datalink layer address that corresponds to an IPv4 address on the local area network. ARP is defined in :rfc:`826`

en	ARPANET

en	The Advanced Research Project Agency (ARPA) Network is a network that was built by network scientists in USA with funding from the ARPA of the US Ministry of Defense. ARPANET is considered as the grandfather of today's Internet.

en	The American Standard Code for Information Interchange (ASCII) is a character-encoding scheme that defines a binary representation for characters. The ASCII table contains both printable characters and control characters. ASCII characters were encoded in 7 bits and only contained the characters required to write text in English. Other character sets such as Unicode have been developed later to support all written languages.

en	ASN.1

en	The Abstract Syntax Notation One (ASN.1) was designed by ISO and ITU-T. It is a standard and flexible notation that can be used to describe data structures for representing, encoding, transmitting, and decoding data between applications. It was designed to be used in the Presentation layer of the OSI reference model but is now used in other protocols such as :term:`SNMP`.

en	ATM

en	Asynchronous Transfer Mode

en	BGP

en	The Border Gateway Protocol is the interdomain routing protocol used in the global Internet.

en	BNF

en	A Backus-Naur Form (BNF) is a formal way to describe a language by using syntactic and lexical rules. BNFs are frequently used to define programming languages, but also to define the messages exchanged between networked applications. :rfc:`5234` explains how a BNF must be written to specify an Internet protocol.

en	broadcast

en	a transmission mode where is same information is sent to all nodes in the network

en	CIDR

en	Classless Inter Domain Routing is the current address allocation architecture for IP version 4. It was defined in :rfc:`1518` and :rfc:`4632`.

en	dial-up line

en	A synonym for a regular telephone line, i.e. a line that can be used to dial any telephone number.

en	DNS

en	eBGP

en	An eBGP session is a BGP session between two directly connected routers that belong to two different Autonomous Systems. Also called an external BGP session.

en	EGP

en	Exterior Gateway Protocol. Synonym of interdomain routing protocol

en	EIGRP

en	The Enhanced Interior Gateway Routing Protocol (EIGRP) is a proprietary intradomain routing protocol that is often used in enterprise networks. EIGRP uses the DUAL algorithm described in [Garcia1993]_.

en	Ethernet

en	The most widely used LAN technology.

en	file transfer

en	A service that enables a user to send or receive a file from a distant server over the network. The File Transfer Protocol :term:`FTP` was a popular service. It has now been replaced by HTTP/HTTPs or more secure protocols such as the `SSH File Transfer Protocol <https://en.wikipedia.org/wiki/SSH_File_Transfer_Protocol>`_.

en	frame

en	a frame is the unit of information transfer in the datalink layer

en	Frame-Relay

en	ftp

en	The File Transfer Protocol defined in :rfc:`959` has been the `de facto` protocol to exchange files over the Internet before the widespread adoption of HTTP :rfc:`2616`.

en	FTP

en	The File Transfer Protocol is defined in :rfc:`959`

en	hosts.txt

en	The original file containing the list of all Internet hosts. This file has been deprecated, but Unix variants still maintain a local ``/etc/hosts`` containing mappings between names and IP addresses. See http://man7.org/linux/man-pages/man5/hosts.5.html for a description of the format of this file on Linux.

en	HTML

en	The HyperText Markup Language specifies the structure and the syntax of the documents that are exchanged on the world wide web. HTML is maintained by the `HTML working group <https://www.w3.org/html/wg/>`_ of the :term:`W3C`

en	HTTP

en	The HyperText Transport Protocol is defined in :rfc:`2616`

en	hub

en	A relay operating in the physical layer.

en	IANA

en	The Internet Assigned Numbers Authority (IANA) is responsible for the coordination of the DNS Root, IP addressing, and other Internet protocol resources

en	iBGP

en	An iBGP session is a BGP between two routers belonging to the same Autonomous System. Also called an internal BGP session.

en	ICANN

en	The Internet Corporation for Assigned Names and Numbers (ICANN) coordinates the allocation of domain names, IP addresses and AS numbers as well protocol parameters. It also coordinates the operation and the evolution of the DNS root name servers.

en	IETF

en	The Internet Engineering Task Force is a non-profit organization that develops the standards for the protocols used in the Internet. The IETF mainly covers the transport and network layers. Several application layer protocols are also standardized within the IETF. The work in the IETF is organized in working groups. Most of the work is performed by exchanging emails and there are three IETF meetings every year. Participation is open to anyone. See https://www.ietf.org

en	IGP

en	Interior Gateway Protocol. Synonym of intradomain routing protocol

en	IGRP

en	The Interior Gateway Routing Protocol (IGRP) is a proprietary intradomain routing protocol that uses distance vector. IGRP supports multiple metrics for each route but has been replaced by :term:`EIGRP`

en	IMAP

en	The Internet Message Access Protocol (IMAP), defined in :rfc:`3501`, is an application-level protocol that allows a client to access and manipulate the emails stored on a server. With IMAP, the email messages remain on the server and are not downloaded on the client.

en	Internet

en	a public internet, i.e. a network composed of different networks that are running :term:`IPv4` or :term:`IPv6`

en	internet

en	an internet is an internetwork, i.e. a network composed of different networks. The :term:`Internet`, with a capital `I` corresponds to the global network that we use today, but other internetworks have been used in the path.

en	inverse query

en	For DNS servers and resolvers, an inverse query is a query for the domain name that corresponds to a given IP address.

en	IP

en	Internet Protocol is the generic term for the network layer protocol in the TCP/IP protocol suite. IP version 4 is widely used but IP version 6 is being deployed globally.

en	IPv4

en	is the version 4 of the Internet Protocol, the connectionless network layer protocol used in most of the Internet today. IPv4 addresses are encoded as a 32 bits field.

en	IPv6

en	is the version 6 of the Internet Protocol, the connectionless network layer protocol which is intended to replace IPv4. IP version 6 addresses are encoded as a 128 bits field.

en	IS-IS

en	Intermediate System- Intermediate System. A link-state intradomain routing that was initially defined for the ISO CLNP protocol but was extended to support IP v4 and IP v6. IS-IS is often used in ISP networks. It is defined in [ISO10589]_

en	ISN

en	The Initial Sequence Number of a TCP connection is the sequence number chosen by the client ( resp. server) that is placed in the `SYN` (resp. `SYN+ACK`) segment during the establishment of the TCP connection.

en	ISO

en	The International Standardization Organization is an agency of the United Nations that is based in Geneva and develop standards on various topics. Within ISO, country representatives vote to approve or reject standards. Most of the work on the development of ISO standards is done in expert working groups. Additional information about ISO may be obtained from https://www.iso.org

en	ISO-3166

en	An :term:`ISO` standard that defines codes to represent countries and their subdivisions. See http://www.iso.org/iso/country_codes.htm

en	ISP

en	An Internet Service Provider, i.e. a network that provides Internet access to its clients.

en	ITU

en	The International Telecommunication Union is a United Nation's agency whose purpose is to develop standards for the telecommunication industry. It was initially created to standardize the basic telephone system but expanded later towards data networks. The work within ITU is mainly done by network specialists from the telecommunication industry (operators and vendors). See https://www.itu.int for more information

en	IXP

en	Internet eXchange Point. A location where routers belonging to different domains are attached to the same Local Area Network to establish peering sessions and exchange packets. See http://www.euro-ix.net/ or https://en.wikipedia.org/wiki/List_of_Internet_exchange_points_by_size for a partial list of IXPs.

en	LAN

en	Local Area Network

en	leased line

en	A telephone line that is permanently available between two endpoints.

en	MAN

en	Metropolitan Area Network

en	MIME

en	The Multipurpose Internet Mail Extensions (MIME) defined in :rfc:`2045` are a set of extensions to the format of email messages that allow to use non-ASCII characters inside mail messages. A MIME message can be composed of several different parts each having a different format.

en	MIME document

en	A MIME document is a document, encoded by using the :term:`MIME` format.

en	minicomputer

en	A minicomputer is a multi-user system that was typically used in the 1960s/1970s to serve departments. See the corresponding Wikipedia article for additional information : https://en.wikipedia.org/wiki/Minicomputer

en	modem

en	A modem (modulator-demodulator) is a device that encodes (resp. decodes) digital information by modulating (resp. demodulating) an analog signal. Modems are frequently used to transmit digital information over telephone lines and radio links. See https://en.wikipedia.org/wiki/Modem for a survey of various types of modems

en	MSS

en	A TCP option used by a TCP entity in SYN segments to indicate the Maximum Segment Size that it is able to receive.

en	multicast

en	a transmission mode where an information is sent efficiently to `all` the receivers that belong to a given group

en	nameserver

en	A server that implements the DNS protocol and can answer queries for names inside its own domain.

en	NAT

en	A Network Address Translator is a middlebox that translates IP packets.

en	NBMA

en	A Non Broadcast Mode Multiple Access Network is a subnetwork that supports multiple hosts/routers but does not provide an efficient way of sending broadcast frames to all devices attached to the subnetwork. ATM subnetworks are an example of NBMA networks.

en	network-byte order

en	Internet protocol allow to transport sequences of bytes. These sequences of bytes are sufficient to carry ASCII characters. The network-byte order refers to the Big-Endian encoding for 16 and 32 bits integer. See https://en.wikipedia.org/wiki/Endianness

en	NFS

en	The Network File System is defined in :rfc:`1094`

en	NTP

en	The Network Time Protocol is defined in :rfc:`1305`

en	OSI

en	Open Systems Interconnection. A set of networking standards developed by :term:`ISO` including the 7 layers OSI reference model.

en	Open Shortest Path First. A link-state intradomain routing protocol that is often used in enterprise and ISP networks. OSPF is defined in and :rfc:`2328` and :rfc:`5340`

en	packet

en	a packet is the unit of information transfer in the network layer

en	PBL

en	Problem-based learning is a teaching approach that relies on problems.

en	POP

en	The Post Office Protocol (POP), defined :rfc:`1939`, is an application-level protocol that allows a client to download email messages stored on a server.

en	remote login

en	A service that enables a user to connect to a distant server over the network. Telnet, defined in :rfc:`854` and the BSD rlogin services defined in :rfc:`1282` were popular in the past. They have been deprecated for security reasons and are now replaced by :term:`ssh`.

en	resolver

en	A server that implements the DNS protocol and can resolve queries. A resolver usually serves a set of clients (e.g. all hosts in campus or all clients of a given ISP). It sends DNS queries to nameservers everywhere on behalf of its clients and stores the received answers in its cache. A resolver must know the IP addresses of the root nameservers.

en	Routing Information Protocol. An intradomain routing protocol based on distance vectors that is sometimes used in enterprise networks. RIP is defined in :rfc:`2453`.

en	RIR

en	Regional Internet Registry. An organization that manages IP addresses and AS numbers on behalf of :term:`IANA`.

en	root nameserver

en	A name server that is responsible for the root of the domain names hierarchy. There are currently a dozen root nameservers and each DNS resolver See http://www.root-servers.org/ for more information about the operation of these root servers.

en	round-trip-time

en	The round-trip-time (RTT) is the delay between the transmission of a segment and the reception of the corresponding acknowledgment in a transport protocol.

en	router

en	A relay operating in the network layer.

en	RPC

en	Several types of remote procedure calls have been defined. The RPC mechanism defined in :rfc:`5531` is used by applications such as NFS

en	SDU (Service Data Unit)

en	a Service Data Unit is the unit information transferred between applications

en	segment

en	a segment is the unit of information transfer in the transport layer

en	SMTP

en	The Simple Mail Transfer Protocol is defined in :rfc:`821`

en	SNMP

en	The Simple Network Management Protocol is a management protocol defined for TCP/IP networks.

en	socket

en	A low-level API originally defined on Berkeley Unix to allow programmers to develop clients and servers.

en	spoofed packet

en	A packet is said to be spoofed when the sender of the packet has used as source address a different address than its own.

en	The Secure Shell (SSH) Transport Layer Protocol is defined in :rfc:`4253`

en	standard query

en	For DNS servers and resolvers, a standard query is a query for a `A` or a `AAAA` record. Such a query typically returns an IP address.

en	switch

en	A relay operating in the datalink layer.

en	SYN cookie

en	The SYN cookies is a technique used to compute the initial sequence number (ISN)

en	TCB

en	The Transmission Control Block is the set of variables that are maintained for each established TCP connection by a TCP implementation.

en	TCP

en	The Transmission Control Protocol is a protocol of the transport layer in the TCP/IP protocol suite that provides a reliable bytestream connection-oriented service on top of IP

en	TCP/IP

en	refers to the :term:`TCP` and :term:`IP` protocols

en	telnet

en	The telnet protocol is defined in :rfc:`854`

en	TLD

en	A Top-level domain name. There are two types of TLDs. The ccTLD are the TLD that correspond to a two letters :term:`ISO-3166` country code. The gTLD are the generic TLDs that are not assigned to a country.

en	TLS

en	Transport Layer Security, defined in :rfc:`5246` is a cryptographic protocol that is used to provide communication security for Internet applications. This protocol is used on top of the transport service but a detailed description is outside the scope of this book.

en	UDP

en	User Datagram Protocol is a protocol of the transport layer in the TCP/IP protocol suite that provides an unreliable connectionless service that includes a mechanism to detect corruption

en	unicast

en	a transmission mode where an information is sent from one source to one recipient

en	vnc

en	A networked application that allows to remotely access a computer's Graphical User Interface. See https://en.wikipedia.org/wiki/Virtual_Network_Computing

en	W3C

en	The world wide web consortium was created to standardize the protocols and mechanisms used in the world wide web. It is thus focused on a subset of the application layer. See https://www.w3.org

en	WAN

en	Wide Area Network

en	X.25

en	A wide area networking technology using virtual circuits that was deployed by telecommunication operators.

en	X11

en	The XWindow system and the associated protocols are defined in [SG1990]_

en	XML

en	The eXtensible Markup Language (XML) is a flexible text format derived from SGML. It was originally designed for the electronic publishing industry but is now used by a wide variety of applications that need to exchange structured data. The XML specifications are maintained by `several working groups <https://www.w3.org/XML/>`_ of the :term:`W3C`