TCP/IP Protocols

supernet mask

A 32-bit number that, when combined with a device's IP address, indicates the kind of network to which the device belongs.

TFTP (Trivial File Transfer Protocol)

A TCP/IP Application layer protocol that enables file transfers between computers. Unlike FTP, it relies on UDP at the Transport layer and does not require a user to log on to the remote host.

IGMP (Internet Group Management Protocol or Internet Group Multicast Protocol)

A TCP/IP protocol used to manage multicast transmissions. Routers use it to determine which nodes belong to a multicast group, and nodes use it to join or leave a multicast group.

PING (Packet Internet Groper)

A TCP/IP troubleshooting utility that can verify that TCP/IP is installed, bound to the NIC, configured correctly, and communicating with the network.

host

A TCP/IP utility that at its simplest returns either the IP address of a host if its host name is specified or its host name if its IP address is specified.

hostname

A TCP/IP utility used to show or modify a client's host name.

ARP (Address Resolution Protocol)

A core protocol in the TCP/IP suite that belongs in the Network layer of the OSI model. It obtains the MAC (physical) address of a host, or node, and then creates a local database that maps the MAC address to the host's IP (logical) address.

RARP (Reverse Address Resolution Protocol)

A core protocol in the TCP/IP suite that belongs in the Network layer of the OSI model. It relies on a its table to associate the IP (logical) address of a node with its MAC (physical) address.

ICMP (Internet Control Message Protocol)

A core protocol in the TCP/IP suite that notifies the sender that something has gone wrong in the transmission process and that packets were not delivered.

UDP (User Datagram Protocol)

A core protocol in the TCP/IP suite that sits in the Transport layer of the OSI model. It is a connectionless transport service.

ARP table

A database of records that maps MAC addresses to IP addresses.

PAT (Port Address Translation)

A form of address translation that uses TCP port numbers to distinguish each client's transmission, thus allowing multiple clients to share a limited number of Internet-recognized IP addresses.

core gateway

A gateway that operates on the Internet backbone.

domain

A group of computers that belong to the same organization and have part of their IP addresses in common.

DNS (Domain Name System or Domain Name Service)

A hierarchical way of tracking domain names and their addresses, devised in the mid-1980s. It does not rely on one file or even one server, but rather is distributed over several key computers across the Internet to prevent catastrophic failure if one or a few computers go down. It is a TCP/IP service that belongs to the Application layer of the OSI model.

socket

A logical address assigned to a specific process running on a computer.

ANDing

A logical process of combining bits. A bit with a value of 1 plus another bit with a value of 1 results in a 1. A bit with a value of 0 plus any other bit results in a 0.

IMAP (Internet Message Access Protocol)

A mail retrieval protocol that improves on the shortcomings of POP. It allows users to store messages on the mail server, rather than always having to download them to the local machine.

multicasting

A means of transmission in which one device sends data to a specific group of devices (not necessarily the entire network segment) in a point-to-multipoint fashion.

public network

A network that any user can access with no restrictions.

private network

A network whose access is restricted to only clients or machines with proper credentials.

TTL (Time to Live)

A number that indicates the maximum time that a datagram or packet can remain on the network before it is discarded.

subnet

A part of a network in which all nodes shares a network addressing component and a fixed amount of bandwidth.

NetBIOS

A protocol that runs in the Session and Transport layers of the OSI model and associates NetBIOS names with workstations.

static ARP table entry

A record in an ARP table that someone has manually entered using the ARP utility.

APIPA (Automatic Private IP Addressing)

A service available on computers running the Windows 98, Me, 2000, XP, Vista, Server 2003, or Server 2008 operating system that automatically assigns the computer's network interface an IP address from the range of 169.254.0.0 to 169.254.255.255 if an IP address hasn't been assigned to that interface.

NTP (Network Time Protocol)

A simple Application layer protocol in the TCP/IP suite used to synchronize the clocks of computers on a network. It depends on UDP for Transport layer services.

host name

A symbolic name that describes a TCP/IP device.

hop

A term used to describe each trip a unit of data takes from one connectivity device to another. Typically, it is used in the context of router-to-router communications.

Telnet

A terminal emulation protocol used to log on to remote hosts using the TCP/IP protocol. It resides in the Application layer of the OSI model.

host file

A text file that associates TCP/IP host names with IP addresses.

anycast address

A type of address specified in IPv6 that represents a group of interfaces, any one of which (and usually the first available of which) can accept a transmission.

supernet

A type of subnet that is created using bits that normally would be reserved for network class information—by moving the subnet boundary to the left.

route

A utility for viewing or modifying a host's routing table.

NNTP (Network News Transfer Protocol or Network News Transport Protocol)

An Application layer protocol in the TCP/IP suite that facilitates the exchange of newsgroup messages, or articles, between multiple servers and users.

DHCP (Dynamic Host Configuration Protocol)

An Application layer protocol in the TCP/IP suite that manages the dynamic distribution of IP addresses on a network.

BOOTP (Bootstrap Protocol)

An Application layer protocol in the TCP/IP suite that uses a central list of IP addresses and their associated devices' MAC addresses to assign IP addresses to clients dynamically. It was the precursor to DHCP.

POP (Post Office Protocol)

An Application layer protocol used to retrieve messages from a mail server. Messages previously stored on the mail server are downloaded to the client's workstation, and then deleted from the mail server.

FTP (File Transfer Protocol)

An Application layer protocol used to send and receive files via TCP/IP.

CIDR (Classless Interdomain Routing)

An IP addressing and subnetting method in which network and host information is manipulated without adhering to the limitations imposed by traditional network class distinctions.

classful addressing

An IP addressing convention that adheres to network class distinctions, in which the first 8 bits of a Class | A address, the first 16 bits of a Class B address, and the first 24 bits of a Class C address are used for network information.

SMTP (Simple Mail Transfer Protocol)

The Application layer TCP/IP subprotocol responsible for moving messages from one e-mail server to another.

IP datagram

The IP portion of a TCP/IP frame that acts as an envelope for data, holding information necessary for routers to transfer data between subnets.

Well Known Ports

The TCP/IP port numbers 0 to 1023

Registered Ports

The TCP/IP ports in the range of 1024 to 49,151. These ports are accessible to network users and processes that do not have special administrative privileges. Default assignments of these ports must be registered with IANA.

port number

The address on a host where an application makes itself available to incoming data.

extended network prefix

The combination of an IP address's network ID and subnet information.

IPv4 (IP version 4)

The current standard for IP addressing that specifies 32-bit addresses composed of four octets.

default gateway

The gateway that first interprets a device's outbound requests, and then interprets its inbound requests to and from other subnets.

switch

The letters or words added to a command that allow you to customize a utility's output. They are usually preceded by a hyphen or forward slash character.

hosts

The name of the host file used on UNIX, Linux, and Windows systems.

network ID

The portion of an IP address common to all nodes on the same network or subnet.

subnetting

The process of subdividing a single class of network into multiple, smaller networks.

routable

The protocols that can span more than one LAN because they carry Network layer and addressing information that can be interpreted by a router.

ping

To send an echo request signal from one node on a TCP/IP-based network to another

IPv6 (IP version 6)

it uses a newer, more efficient header in its packets and allows for 128-bit source and destination IP addresses.