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DSL

Short for digital subscriber line, but is commonly used in reference to the asymmetric version of this

technology (ADSL) that allows data to be sent over existing copper telephone lines at data rates of from 1.5

to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data

(known as the upstream rate).

ADSL requires a special ADSL modem. ADSL is growing in popularity as more areas around the world

gain access.

DSLAM

DSL Access Multiplexor. The piece of equipment at the telephone company central office that provides the

ADSL signal.

Dynamic Host Configuration Protocol

DHCP. An Ethernet protocol specifying how a centralized DHCP server can assign network configuration

information to multiple DHCP clients. The assigned information includes IP addresses, DNS addresses, and

gateway (router) addresses.

EAP

Extensible Authentication Protocol is a general protocol for authentication that supports multiple

authentication methods.

EAP, an extension to PPP, supports such authentication methods as token cards, Kerberos, one-time

passwords, certificates, public key authentication and smart cards. In wireless communications using EAP, a

user requests connection to a WLAN through an AP, which then requests the identity of the user and

transmits that identity to an authentication server such as RADIUS. The server asks the AP for proof of

identity, which the AP gets from the user and then sends back to the server to complete the authentication.

EAP is defined by RFC 2284.

ESP

Encapsulating Security Payload.

ESSID

The Extended Service Set Identification (ESSID) is a thirty-two character (maximum) alphanumeric key

identifying the wireless local area network.

Gateway

A local device, usually a router, that connects hosts on a local network to other networks.

IETF

Internet Engineering Task Force. Working groups of the IETF propose standard protocols and procedures for

the Internet, which are published as RFCs (Request for Comment) at

www.ietf.org

.

An open international community of network designers, operators, vendors, and researchers concerned with

the evolution of the Internet architecture and the smooth operation of the Internet.

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IKE

Internet Key Exchange. An automated method for exchanging and managing encryption keys between two

VPN devices.

IP

Internet Protocol is the main internetworking protocol used in the Internet. Used in conjunction with the

Transfer Control Protocol (TCP) to form TCP/IP.

IP Address

A four-byte number uniquely defining each host on the Internet, usually written in dotted-decimal notation

with periods separating the bytes (for example, 134.177.244.57).

Ranges of addresses are assigned by Internic, an organization formed for this purpose.

IPSec

Internet Protocol Security. IPSec is a series of guidelines for securing private information transmitted over

public networks. IPSec is a VPN method providing a higher level of security than PPTP.

IPX

Short for Internetwork Packet Exchange, a networking protocol used by the Novell NetWare operating

systems.

Like UDP/IP, IPX is a datagram protocol used for connectionless communications. Higher-level protocols,

such as SPX and NCP, are used for additional error recovery services.

ISP

Internet service provider.

Internet Protocol

The main internetworking protocol used in the Internet. Used in conjunction with the Transfer Control

Protocol (TCP) to form TCP/IP.

LAN

A communications network serving users within a limited area, such as one floor of a building.

LDAP

A set of protocols for accessing information directories.

Lightweight Directory Access Protocol

LDAP. A set of protocols for accessing information directories.

LDAP is based on the standards contained within the X.500 standard, but is significantly simpler. And

unlike X.500, LDAP supports TCP/IP, which is necessary for any type of Internet access. Because it's a

simpler version of X.500, LDAP is sometimes called

X.500-lite.

local area network

LAN. A communications network serving users within a limited area, such as one floor of a building.

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A LAN typically connects multiple personal computers and shared network devices such as storage and

printers. Although many technologies exist to implement a LAN, Ethernet is the most common for

connecting personal computers.

MAC address

The Media Access Control address is a unique 48-bit hardware address assigned to every network interface

card. Usually written in the form 01:23:45:67:89:ab.

Mbps

Megabits per second.

MD5

MD5 creates digital signatures using a one-way hash function, meaning that it takes a message and converts

it into a fixed string of digits, also called a message digest.

When using a one-way hash function, one can compare a calculated message digest against the message

digest that is decrypted with a public key to verify that the message hasn't been tampered with. This

comparison is called a "hashcheck."

MDI/MDIX

In cable wiring, the concept of transmit and receive are from the perspective of the PC, which is wired as a

Media Dependant Interface (MDI). In MDI wiring, a PC transmits on pins 1 and 2. At the hub, switch,

router, or access point, the perspective is reversed, and the hub receives on pins 1 and 2. This wiring is

referred to as Media Dependant Interface - Crossover (MDI-X). See also AES.

Maximum Receive Unit

The size in bytes of the largest packet that can be sent or received.

Maximum Transmit Unit

The size in bytes of the largest packet that can be sent or received.

Most Significant Bit or Most Significant Byte

MSB. The portion of a number, address, or field that is farthest left when written as a single number in

conventional hexadecimal ordinary notation. The part of the number having the most value.

MRU

The size in bytes of the largest packet that can be sent or received.

MSB

MSB. The portion of a number, address, or field that is farthest left when written as a single number in

conventional hexadecimal ordinary notation. The part of the number having the most value.

MTU

The size in bytes of the largest packet that can be sent or received.

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NAT

A technique by which several hosts share a single IP address for access to the Internet.

NetBIOS

The Network Basic Input Output System is an application programming interface (API) for sharing services

and information on local-area networks (LANs).

Provides for communication between stations of a network where each station is given a name. These names

are alphanumeric names, up to 16 characters in length.

Network Address Translation

NAT. A technique by which several hosts share a single IP address for access to the Internet.

NIC

Network Interface Card. An adapter in a computer which provides connectivity to a network.

NID

Network Interface Device. The point of demarcation, where the telephone line comes into the house.

packet

A block of information sent over a network. A packet typically contains a source and destination network

address, some protocol and length information, a block of data, and a checksum.

Perfect Forward Secrecy

Perfect Forward Secrecy (PFS) provides additional security by means of a Diffie-Hellman shared secret

value. With PFS, if one key is compromised, previous and subsequent keys are secure because they are not

derived from previous keys.

PKIX

PKIX. The most widely used standard for defining digital certificates.

Point-to-Point Protocol

PPP. A protocol allowing a computer using TCP/IP to connect directly to the Internet.

PPP

A protocol allowing a computer using TCP/IP to connect directly to the Internet.

PPPoA

PPPoA. PPP over ATM is a protocol for connecting remote hosts to the Internet over an always-on

connection by simulating a dial-up connection.

PPPoE

PPPoE. PPP over Ethernet is a protocol for connecting remote hosts to the Internet over an always-on

connection by simulating a dial-up connection.

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PPP over ATM

PPPoA. PPP over ATM is a protocol for connecting remote hosts to the Internet over an always-on

connection by simulating a dial-up connection.

PPP over Ethernet

PPPoE. PPP over Ethernet is a protocol for connecting remote hosts to the Internet over an always-on

connection by simulating a dial-up connection.

PPTP

Point-to-Point Tunneling Protocol. A method for establishing a virtual private network (VPN) by embedding

Microsoft’s network protocol into Internet packets.

PSTN

Public Switched Telephone Network.

Public Key Infrastructure

PKIX. The most widely used standard for defining digital certificates.

X.509 is actually an ITU Recommendation, which means that it has not yet been officially defined or

approved. As a result, companies have implemented the standard in different ways. For example, both

Netscape

and Microsoft

use X.509 certificates to implement SSL in their Web servers and browsers. But an

X.509 Certificate generated by Netscape may not be readable by Microsoft products, and vice versa.

RADIUS

Short for Remote Authentication Dial-In User Service, RADIUS is an authentication system.

Using RADIUS, you must enter your user name and password before gaining access to a network. This

information is passed to a RADIUS server, which checks that the information is correct, and then authorizes

access. Though not an official standard, the RADIUS specification is maintained by a working group of the

IETF.

RFC

Request For Comment. Refers to documents published by the Internet Engineering Task Force (IETF)

proposing standard protocols and procedures for the Internet. RFCs can be found at

www.ietf.org

.

RIP

A protocol in which routers periodically exchange information with one another so that they can determine

minimum distance paths between sources and destinations.

router

A device that forwards data between networks. An IP router forwards data based on IP source and

destination addresses.

Routing Information Protocol

RIP. A protocol in which routers periodically exchange information with one another so that they can

determine minimum distance paths between sources and destinations.