NX-590E Internet Interface
20
ETHERNET
A local-area network (LAN) architecture developed by Xerox Corporation in
cooperation with DEC and Intel in 1976. Ethernet uses a bus or star topology
and supports data transfer rates of 10Mbps. The Ethernet specification served
as the basis for the IEEE 802.3 standard, which specifies the physical and
lower software layers. Ethernet uses the CSMA/CD access method to handle
simultaneous demands. It is one of the most widely implemented LAN
standards.
A newer version of Ethernet, called 100Base-T (or Fast Ethernet) supports
data transfer rates of 100Mbps. And the newest version, Gigabit Ethernet
supports data rates of 1 gigabit (1,000 megabits) per second.
FIREWALL
A system designed to prevent unauthorized access to or from a private
network. Firewalls can be implemented in both hardware and software, or a
combination of both. Firewalls are frequently used to prevent unauthorized
Internet users from accessing private networks connected to the Internet,
especially intranets. All messages entering or leaving the intranet pass
through the firewall, which examines each message and blocks those that do
not meet the specified security criteria.
There are several types of firewall techniques:
Packet filter: Looks at each packet entering or leaving the network
and accepts or rejects it based on user-defined rules. Packet filtering is
fairly effective and transparent to users, but it is difficult to configure. In
addition, it is susceptible to IP spoofing.
Application gateway: Applies security mechanisms to specific
applications, such as FTP and Telnet servers. This is very effective,
but can impose performance degradation.
Circuit-level gateway: Applies security mechanisms when a TCP or
UDP connection is established. Once the connection has been made,
packets can flow between the hosts without further checking.
Proxy server: Intercepts all messages entering and leaving the
network. The proxy server effectively hides the true network
addresses.
In practice, many firewalls use two or more of these techniques in concert.
A firewall is considered a first line of defense in protecting private information.
For greater security, data can be encrypted.
GATEWAY
In networking, a combination of hardware and software that links two different
types of networks. Gateways between e-mail systems, for example, allow
users on different e-mail systems to exchange messages.
