HomePortal 3801HGV Gateway User Guide

Glossary

Term

 

Description

NAT (Network Address

Enables a LAN to use one set of IP addresses for internal traffic and a second set of

Translation)

IP addresses for external traffic. This feature is used by the system so an end user

 

can have an internal computer network in their home, with all its computers using

 

internal IP addresses, using only one routable IP address, which accesses the

 

outside (Internet).

PAT (Port Address Translation)

Allows hosts on a LAN to communicate with the rest of a network (such as the

 

Internet) without revealing their own private IP address. All outbound packets have

 

their IP address translated to the router’s external IP address. Replies come back to

 

the router, which then translates them back into the private IP address of the original

 

host for final delivery.

PPP (Point-to-Point Protocol)

A protocol that allows a computer to access the Internet using a dial-up phone line

 

and a high-speed modem. This can be accomplished over Ethernet (PPPoE), or over

 

Asynchronous Transfer Mode (ATM; PPPoA).

PPPoA (Point-to-Point Protocol

A specification for connecting multiple computer users on an Ethernet LAN to a

over ATM)

remote site through common customer premises equipment (such as a modem).

 

PPPoA combines the Point-to-Point Protocol (PPP), commonly used in dialup

 

connections, with the ATM (Asynchronous Transfer Mode) protocol, which supports

 

multiple users in a LAN.

PPPoE (Point-to-Point Protocol

A specification for connecting multiple computer users on an Ethernet LAN to a

over Ethernet)

remote site through common customer premises equipment (such as a modem).

 

PPPoE combines the Point-to-Point Protocol (PPP), commonly used in dialup

 

connections, with the Ethernet protocol, which supports multiple users in a LAN.

Protocol Timeout

The amount of time (in seconds) during which a connection in the specified range

 

remains open when there is no data transfer. After a connection has been established

 

on a given port, the sender and receiver usually determine when the session is

 

finished and the connection is closed. However, if the connection is left open and data

 

transfer stops, the system must eventually close the connection and reclaim the

 

resources in order to protect your network. In some cases, the system might close the

 

application during normal operation (for example, if there is a long pause between

 

data transfer). If this is the case, lengthening the timeout may help.

PVC (permanent virtual circuit)

A virtual circuit that is permanently available. Used to establish connections between

 

hosts that communicate frequently.

Router

The central switching device in a packet-switched computer network that directs and

 

controls the flow of data through the network.

Subnet Mask

The IP addressing system allows subnetworks or “interchanges” to be created, and

 

devices numbers or “extensions” to be established within these subnetworks. These

 

numbers are created using a mathematical device called a subnet mask. A subnet

 

mask, like the IP address, is a set of four numbers in dotted decimal notation. Subnet

 

masks typically take three forms:

 

255.0.0.0

 

255.255.0.0

 

255.255.255.0

The number 255 “masks” out the corresponding number of the IP address, resulting in IP address numbers that are valid for the network. For example, an IP address of

123.45.67.89and a subnet mask of 255.255.255.0 results in a sub network number of

123.45.67.0and a device number of 89.

The subnet mask used for the network typically corresponds to the class of IP address assigned, as shown in the following table:

IP Address

Dotted-

Ranges

Decimal

Corresponding

Class

Notation

Subnet Mask

Class A

1.xxx.xxx.xxx to

255.0.0.0

 

126.xxx.xxx.xxx

 

Class B

128.0.xxx.xxx to

255.255.0.0

 

191.255.xxx.xxx

 

Class C

192.0.0.xxx to

255.255.255.0

 

223.255.255.xx

 

 

x

 

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