Guide to TCP/IP Ch. 1 Definitions

port number

A 16-bit number that identifies either a well-known application service or a dynamically assigned port number for a transitory sender-receiver exchange of data through TCP or UDP. Also referred to as a port address.

Point-to-Point Tunneling Protocol (PPTP)

A Layer 2 or TCP/IP Network Interface layer protocol that allows a client and a server to establish a SECURE, ENCRYPTED communications link for just about any kind of PPP traffic.

Point-to-Point Protocol (PPP)

A Layer 2 or TCP/IP Network Interface layer protocol that permits a client and a server to establish a communications link that can accommodate a variety of higher-layer protocols, including IP, AppleTalk, SNA, IPX/SPX, NetBEUI, and many others. Today's most widely used serial line protocol for making Internet connections.

multicast packet

A PACKET SENT TO A GROUP of devices, often multiple routers

local area network (LAN)

A SINGLE NETWORK CABLE SEGMENT, subnet, or logical network community that represents a COLLECTION OF MACHINES that can communicate with one another more or less directly (using MAC addresses).

registered port

A TCP or UDP port number in the range from 1024 to 65535 and associated with a SPECIFIC Application layer protocol or service.

Remote Monitoring (RMON)

A TCP/IP Application layer protocol designed to support REMOTE MONITORING AND MANAGEMENT of networking devices, such as hubs, servers, and routers.

network services

A TCP/IP term for protocol/service combination that operates at the Application layer in the model.

Network File System (NFS)

A TCP/IP-based, network-distributed file system that permits users to treat files and directories on machines elsewhere on a network as an extension of their local desktop file systems.

National Science Foundation (NSF)

A U.S. government agency charged with oversight and support for government-funded scientific research and development.

packet

A generic term for a PDU at any layer in a networking model. The term is properly applied to PDUs at Layer 3, or the TCP/IP Internet layer.

pcap

A generic term for protocol capture for a special network interface driver designed to permit capture of all network traffic I promiscuous mode while running

network interface controller (NIC)

A hardware device used to PERMIT a computer to ATTACH to and communicate with a LAN

protocol suite

A named family of networking protocols, such as TCP/IP, IPX/SPX, or NetBEUI, where each such family enables computers to communicate across a network.

packet-switched network

A network in which data packets may take any usable path between sender and receiver, where sender and receiver are identified by unique network addresses and there's no requirement that all packets follow the same path in transit (although they often do).

protocol

A precise set of standards that governs communications between computers on a network. Many protocols function in one or more layers of the OSI reference model.

IEEE 802

A project undertaken by the IEEE in 1980 that covers Physical and Data Link layers for networking technologies in general (802.1 and 802.2), plus specific networking technologies, such as Ethernet (802.3).

NSFNET

A public network operated by the National Science Foundation in the 1980 to support the Internet backbone

Internet Network Information Center (InterNIC)

A quasi-governmental agency that was responsible for assigned names and numbers on the Internet (this responsibility now falls on ICANN).

layer

A single component or facet in a networking model that HANDLES ON PARTICULAR ASPECT of network access or communications

protocol stack

A specific IMPLEMENTATION of a protocol suite on a computer, including a network interface, necessary drivers, and whatever protocol and service implementations are necessary to enable the computer to use a specific protocol suite to communicate across the network.

packet filter

A specific collection of inclusion or exclusion rules that is applied to a stream of network packets and determines what is captured (and what is ignored) from the original input stream.

Process layer

A synonym for the TCP/IP Application layer, where high-level protocols and services, such as FTP and Telnet, operate

pre-filter

A type of data filter applied to a raw input stream in a protocol analyzer that selects only packets that meet its criteria for capture and retention. Because it is applied before data is captured, it's called a pre-filter.

point-to-point transmission

A type of network communication in which pairs of devices establish a communications link to exchange data with one another; the most common type of connection used when communicating with an Internet service provider.

protocol number

An 8-bit numeric identifier associated with some specific TCP/IP protocol.

Proposed Standard

An INTERMEDIATE step for standards-level RFCs in which a DRAFT Standard goes through initial review, with two or more reference implementations to demonstrate interoperability between those implementations.

Historic Standard

An Internet RFC that was superseded by a newer, more current version.

Internet Standard

An RFC document that SPECIFIES THE RULES, structure, and behavior of a current Internet protocol or service. Also called a Standard RFC.

Institute of Electrical and Electronic Engineers (IEEE)

An international organization that sets standards for electrical and electronic equipment, including network interfaces and communications technologies.

peer layers

Analogous layers in the protocol stacks on a sender and a receiver; the receiving layer usually reverses whatever operations the sending layer performs.

network analysis

Another term for protocol analysis.

protocol data unit (PDU)

At any layer in a networking model, represents the PACKAGE FOR DATA at that layer, including a header, a payload, and in some cases, a trailer.

encapsulation

ENCLOSURE of data from an upper-layer protocol between a header and a trailer (the trailer is optional) for the current later to identify sender and receiver and, possibly, INCLUDE DATA INTEGRITY CHECK information

display filters

FILTERS that are applied to the packets that reside in a trace buffer, for the purpose of VIEWING ONLY THE PACKETS OF INTEREST.

Request for Comments (RFCs)

IETF standards documents that specify or describe best practices, provide information about the Internet, or specify an Internet protocol or service.

Physical layer

Layer 1 in the ISO/OSI Layer 1 in the ISO/OSI network reference model. The Physical layer is where CONNECTIONS, COMMUNICATIONS, and interfaces—hardware and SIGNALING requirements—are handled.

Data Link layer

Layer 2 of the ISO/OSI network reference model. Layer is responsible for enabling reliable transmission of data through the Physical layer at the sending end and for checking such reliability upon reception at the receiving end.

Network layer

Layer 3 of the ISO/OSI network reference model. Layer handles logical addresses associated with individual machines on a network by correlating human-readable names for such machines with unique, machine-readable numeric addresses. It uses addressing information to ROUTE A PDU FROM SENDER TO A RECEIVER when the source and destination do not reside on the same physical network segment.

Presentation layer

Layer 6 of the ISO/OSI reference model. Where generic network data formats are translated into platform-specific data formats for incoming data and vice versa for outgoing data. This is also the layer where optional encryption or compression services may be applied (or reversed).

Internetwork

Literally, a "network of networks," an internetwork is better understood as a collection of MULTIPLE INTERCONNECTED PHYSICAL NETWORKS that together behave as a single logical network (of which the Internet is the prime example).

alarm

NOTIFICATION of unusual network events or ERRORSon the network

promiscuous mode operation

Network interface card and driver operation used to capture broadcast packets, multicast packets, packets sent to other devices, and error packets.

oversized packets

Packets that EXCEED the MTU for the network and usually point to a problem with a NIC or its driver software.

Host

TCP/IP terminology for any computer with one or more valid TCP/IP addresses (hence, reachable on a TCP/IP-a based network). A host also can be a computer that offers TCP/IP services to clients.

Internet Society (ISOC)

The PARENT organization under which the rest of the Internet governing bodies fall. a user-oriented, public-access organization that solicits end-user participation and input to help set future Internet policy and direction.

Hypertext Transfer Protocol (HTTP)

The TCP/IP Application layer protocol and service that supports access to the World Wide Web.

Frame

The basic DATA LINK layer PDU for the ISO/OSI reference model.

maximum transmission unit (MTU)

The biggest single chunk of data that can be transferred across any particular type of network medium- for example, 1518 bytes is the MTU for conventional Ethernet

Internet Research Task Force (IRTF)

The forward-looking research and development arm of the Internet Society. The IRTF reports to the IAB for direction and governance.

Internet Protocol version 6 (IPv6)

The latest version of IP that's moving into global deployment and use (IPv4 remains the predominant TCP/IP version in use but will slowly be supplanted by IPv6).

media flow control

The management of data transmission rates between two devices across a local network medium that guarantees the receiver can accept and process input before it arrives from the sender.

Open Systems Interconnection (OSI)

The name of an open-standard internetworking initiative undertaken in the 1980s, primarily in Europe, and originially intended to supersede TCP/IP. Technical and political problems prevented this anticipated out from materializing, but the ISO/OSI reference model is a legacy of this effort.

ISO/OSI network reference model

The official name for the seven-layer network reference model used to describe how networks operate and behave.

Internet Corporation for Assigned Names and Numbers (ICANN)

The organization within the Internet Society responsible for proper assignment of all domain NAMES AND NUMBERS IP addresses for the global Internet. ICANN works with private companies called name registrars o manage domain names and with ISPs to manage assignment of number IP addresses.

Internet Architecture Board (IAB)

The organization within the Internet Society that governs the actions of both the IETF and the IRTF and has final approval authority for Internet Standards.

Internet Engineering Task Force (IETF)

The organization within the Internet Society that's responsible for all currently used Internet Standards, PROTOCOLS, and SERVICES as well as for MANAGING the development and maintenance of Internet Requests for Comments (RFCs).

Internet Protocol version 4 (IPv4)

The original version of IP that's still in widespread public use, although IPv6 is currently fully specified and moving into global deployment and use.

Header

The portion of a PDU that PRECEDES the actual content for the PDU and usually IDENTIFIES SENDER AND RECEIVER, protocols in use, and other information necessary to establish context for senders and receivers.

payload

The portion of a PDU that contains information intended for delivery to an application or to a higher-layer protocol depending on where in the stack the PDU is situation).

Internet Protocol (IP)

The primary Network layer protocol in the TCP/IP suite. IP MANAGES ROUTING AND DELIVERY FOR TRAFFIC on TCIP/IP- based networks.

reassembly

The process applied at the Transport layer in which messages segmented into multiple chunks for transmission across the network are PUT BACK TOGETHER in the proper order for delivery to an application on the receiving end. The IP Fragment Offset field (discussed in Chapter 3) is used to identify the order of the fragments for reassembly.

protocol analysis

The process of CAPTURING PACKETS off the network for the purpose of gathering communication STATISTICS, observing trends, and EXAMING communication sequences.

Fragmentation

The process of dividing a packet into multiple smaller packets to cross a link that supports an MTU than the link where the packet originated.

multiplexing

The process whereby multiple individual data streams from Application layer processes are joined together for transmission by a specific TCP/IP transport protocol through the IP protocol.

Acceptable Use Policy (AUP)

a FORMAL POLICY DOCUMENT that dictates what kinds of online behavior or system use are acceptable to the overall user community

congestion control

a TCP mechanism, also available from other protocols, that permits network hosts to exchange information about their ABILITY TO HANDLE TRAFFIC volumes and thereby causes senders to decrease or increase the frequency and size of their upcoming communications.

dynamically assigned port address

a TEMPRORARY TCP or UDP port number allocated to permit a client and server to exchange data with each other ONLY AS LONG AS THEIR CONNECTION REMAINS ACTIVE

divide and conquer

a computer design approach that consists of decomposing a big complex problem into a SERIES OF SMALLER, LESS COMPLEX, and interrelated problems, each of which can be solved more or less independently of the others.

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

a formal name for Ethernet's contention management approach "listen before attempting to send" (to make sure no later message tramples on an earlier one) and "listen while sending" (to make sure messages sent at roughly the same time don't collide with one another).

addressing

a method of ASSIGNING A UNIQUE SYMBOLIC name or numerical identifier to an individual network interface on a network segment to make every such interface uniquely identifiable (and addressable)

capture filter

a method used to IDENTIFY SPECIFIC PACKETS that should be CAPTURED into a trace buffer based on some packet characteristic, such as source or destination address

Ethernet

a network access protocol based on carrier sense, multiple access, and collision detection.

connectionless

a networking protocol that does not require network senders and receivers to exchange information about their availability or ability to communicate; also known as "BEST-EFFORT DELIVERY".

checkpoint

a point in time at which ALL SYSTEM STATE AND INFORMATION IS CAPTURED and saved so that, after a subsequent failure in systems or communications, operations CAN RESUME at that point in time, with NO FURTHER LOSS of data or information.

destination port number

a port address for incoming TCP/IP communication that INDENTIFIES A TARGET application or service process.

checksum

a special mathematical value that represents the contents of a message so precisely that any change in the contents will cause a change in the checksum-calculated before and after network transmission of data and then compare. If transmitted and calculated checksums agree, the assumption is that the data arrived unaltered.

Best Current Practice (BCP)

a specific type of Internet RFC document that outlines the best ways to design, implement, and maintain TCP/IP based networks

broadcast

a specific type of network transmission (and address) meant to be NOTICED AND READ BY ALL recipients on any cable segment where that transmission appears; a way of reaching all addresses on any network

Draft Standard

a standard RFC that has gone through the draft process, been approved, and for which two reference implementations must be shown to work together before it can move on to Internet Standard status.

application process

a system process that represents a specific type of network application of service

broadcast packet

a type of network transmission intended for DELIVERY TO ALL devices on the network. The Ethernet broadcast address is 0xFF-FF-FF-FF-FF-FF for IPv6 and 255.255.255.255 for IPv4

connection-oriented

a type of networking protocol that relies on explicit communications and negotiations between sender and receiver to manage delivery of data between the two parties.

anycast packet

an IPv6 MULTICAST method that permits multiple recipients to be designated for a SINGLE message, usually for a SINGLE cable segment or broadcast domain.

Advanced Research Projects Agency (ARPA)

an agency within the US Department of Defense that funded forward-thinking RESEARCH in computing technology.

Commercial Internet Exchange (CIX)

an early consortium of commercial Internet users that pioneered the extension of Internet use to E-COMMERCE and BUSINESS COMMUNICATIONS.

ARPANET

an experimental network, funded by ARPA, designed to test the feasibility of a platform neutral, long distance, robust, and reliable internetwork that provided the foundation for what we know today as the Internet.

cable segment

any single collection of network media and attached devices that fits on a single piece of network cable or within a single network device, such as a hub or, in a virtual equivalent, a local area network emulation environment on a switch

daemon

taken from James Clerk Maxwell's famous physics idea, a daemon is a computer process whose job is to "LISTEN" in on connection attempts for one of more specific network services and hand off all valid attempts to temporary connections known as sockets

data frame

the BASIC PDU at the DATA LINK LAYER, which represents what is transmitted or received as a pattern of bits on a network interface

Defense Information Systems Agency (DISA)

the DoD agency that took over operation of the Internet when ARPA surrendered its control in 1983

Centre Europeen de Reseache Nucleaire (CERN)

the European Organization for Nuclear Research, where Tim Berners-Lee invented protocols and services for the World Wide Web between 1989 and 1991

decode

the INTERPRETED VALUE of a PDU, or a field within a PDU, PERFORMED BY A PROTOCOL ANALYZER or similar software package.

data segment

the basic PDU for TCP at the TRANSPORT LAYER

datagram

the basic protocol data unit at the TCP/IP NETWORK ACCESS LAYER. Used by connectionless protocols at the Transport layer, adds a header to the PDU, supplied from whichever Application layer protocol or service uses a connectionless protocol, such as UDP; hence, UDP is also known as a datagram service.

Ethernet collision fragments

the garbled traffic on a network produced when two packets transmitted at about the same time collide, resulting in a hodgepodge of signals.

domain

the name of a FIRST-LEVEL ENTRY in the domain name hierarchy, such as cengage.com or whitehouse.gov

decoding

the process of interpreting the fields and contents of a packer and presenting the packet in a reliable format.

Application Layer

the uppermost layer of the ISO/OSI network reference model (and the TCP/IP model) where the INTERFACE between the protocol suite and ACTUAL APPLICATIONS resides

4.2BSD

the version of the Berkeley Software Distribution (BSD) and UNIX that was the first to include a TCP/IP implementation