56

Firewall

: Select this option can automatically detect and block Denial of Service

(DoS) attacks, such as Ping of Death, SYN Flood, Port Scan and Land Attack.

SPI

: Select this option to Enabled or Disabled the SPI feature.

(NOTE:

If you enable SPI, all traffics initiate from WAN would be blocked, including

DMZ, Virtual Server, and ACL WAN side)

Appendix A: Glossary

Address mask

A bit mask select bits from an Internet address for subnet addressing. The mask is 32

bits long and selects the network portion of the Internet address

and one or more bits of the local portion. Sometimes it called subnet mask.

AAL5

ATM Adaptation Layer - This layer maps higher layer user data into ATM cells,

making the data suitable for transport through the ATM network.

ADSL

Asymmetric digital subscriber line

ATM

Asynchronous Transfer Mode - A cell-based data transfer technique in which channel

demand determines packet allocation. ATM offers fast packet technology,

real time, and demand led switching for efficient use of network resources.

57

AWG

American Wire Gauge - The measurement of thickness of a wire

Bridge

A device connects two or more physical networks and forward packets between them.

Bridges can usually be made to filter packets, that is, to forward only certain traffic.

Related devices are repeaters which simply forward electrical signals from one cable

to the other and full-fledged routers which make routing decisions based on several

criteria.

Broadband

Characteristic of any network multiplexes independent network carriers onto a single

cable. Broadband technology allows several networks to coexist on one single cable;

traffic from one network does not interfere with traffic from another. Broadcast a

packet delivery system where a copy of a given packet is given to all hosts attached to

the network. Example: Ethernet.

CO

Central Office. Refers to equipment located at a Telco or service provider'

s office.

CPE

Customer Premises Equipment located in a user'

s premises

DHCP (Dynamic Host Configuration Protocol)

DHCP is software that automatically assigns IP addresses to client stations logging

onto a TCP/IP network. DHCP eliminates having to manually assign permanent IP

addresses to every device on your network. DHCP software typically runs in servers

and is also found in network devices such as Routers.

DMT

Discrete Multi-Tone frequency signal modulation

Downstream rate

The line rate for return messages or data transfers from the network machine to the

user'

s premises machine.

DSLAM

Digital Subscriber Line Access Multiplex

58

Dynamic IP Addresses

A dynamic IP address is an IP address that is automatically assigned to a client station

(computer, printer, etc.) in a TCP/IP network. Dynamic IP addresses are typically

assigned by a DHCP server, which can be a computer on the network or another piece

of hardware, such as the Router. A dynamic IP address

may change every time your computer connects to the network.

Encapsulation

The technique layer protocols in which a layer adds header information to the

protocol data unit (PDU) from the layer above. As an example, in Internet

terminology, a packet would contain a header from the physical layer, followed by a

header from the network layer (IP), followed by a header from the transport

layer (TCP), and followed by the application protocol data.

Ethernet

One of the most common local area network (LAN) wiring schemes, Ethernet has a

transmission rate of 10 Mbps.

FTP

File Transfer Protocol. The Internet protocol (and program) transfer files between

hosts.

Hop count

A measure of distance between two points on the Internet. It is equivalent to the

number of gateways that separate the source and destination.

HTML

Hypertext Markup Language - The page-coding language for the World Wide Web.

HTML browser

A browser used to traverse the Internet, such as Netscape or Microsoft Internet

Explorer.

http

Hypertext Transfer Protocol - The protocol carry world-wide-web (www) traffic

between a www browser computer and the www server being accessed.

59

ICMP

Internet Control Message Protocol - The protocol handle errors and control messages

at the IP layer. ICMP is actually part of the IP protocol.

Internet address

An IP address is assigned in blocks of numbers to user organizations accessing the

Internet. These addresses are established by the United States Department

of Defense'

s Network Information Center. Duplicate addresses can cause major

problems on the network, but the NIC trusts organizations to use individual

addresses responsibly. Each address is a 32-bit address in the form of x.x.x.x where x

is an eight- bit number from 0 to 255. There are three classes: A, B and C, depending

on how many computers on the site are likely to be connected.

Internet Protocol (IP)

The network layer protocol for the Internet protocol suite

IP address

The 32-bit address assigned to hosts that want to participate in a TCP/IP Internet.

ISP

Internet service provider - A company allows home and corporate users to connect to

the Internet.

MAC

Media Access Control Layer - A sub-layer of the Data Link Layer (Layer 2) of the

ISO OSI Model responsible for media control.

MIB

Management Information Base - A collection of objects can be accessed via a

network management protocol, such as SNMP and CMIP (Common Management

Information Protocol).

NAT

Network Address Translation - A proposal for IP address reuse, where the local IP

address is mapped to a globally unique address.

NVT

Network Virtual Terminal

60

PAP

Password Authentication Protocol

PORT

The abstraction used in Internet transport protocols to distinguish among multiple

simultaneous connections to a single destination host.

POTS

Plain Old Telephone Service - This is the term describe basic telephone service.

PPP

Point-to-Point-Protocol - The successor to SLIP, PPP provides router-to-router and

host-to-network connections over both synchronous and asynchronous circuits.

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.

Remote server

A network computer allows a user to log on to the network from a distant location.

RFC

Request for Comments - Refers to documents published by the Internet Engineering

Task Force (IETF) proposing standard protocols and procedures for the Internet. RFC

can be found at www.ietf.org.

Route

The path that network traffic takes from its source to its destination. The route a

datagram may follow can include many gateways and many physical networks.

In the Internet, each datagram is routed separately.

Router

A system is responsible for making decisions about which of several paths network

(or Internet) traffic will follow. To do this, it uses a routing protocol to

gain information about the network and algorithms to choose the best route based on

several criteria known as "routing metrics".

Routing Table