▪ Gateway
A gateway is a
network
point that acts as an entrance to another network. On the Internet, a
node
or
stopping point can be either a gateway node or a
host
(end-point) node. Both the computers of
Internet users and the computers that serve pages to users are host nodes. The computers that
control traffic within your company's network or at your local Internet service provider (
ISP
) are
gateway nodes. In the network for an
enterprise
, a computer
server
acting as a gateway node is
often also acting as a
proxy server
and a
firewall
server. A gateway is often associated with both a
router
, which knows where to direct a given
packet
of data that arrives at the gateway, and a
switch
,
which furnishes the actual path in and out of the gateway for a given packet.
• PPPOE
PPPoE (Point-to-Point Protocol over Ethernet) is a specification for connecting multiple computer
users on an
Ethernet local area network
to a remote site through common customer
premises equipment, which is the telephone company's term for a
modem
and similar devices.
PPPoE can be used to have an office or building-full of users share a common Digital Subscriber
Line (
DSL
),
cable modem
, or
wireless
connection to the Internet. PPPoE combines the Point-to-
Point Protocol (
PPP
), commonly used in dialup connections, with the Ethernet protocol, which
supports multiple users in a local area network. The PPP protocol information is encapsulated
within an Ethernet
frame
. PPPoE has the advantage that neither the telephone company nor the
Internet service provider (
ISP
) needs to provide any special support. Unlike dialup connections, DSL
and cable modem connections are "always on." Since a number of different users are sharing the
same physical connection to the remote service provider, a way is needed to keep track of which
user traffic should go to and which user should be billed. PPPoE provides for each user-remote
site session to learn each other's network addresses (during an initial exchange called "discovery").
Once a session is established between an individual user and the remote site (for example, an
Internet service provider), the session can be monitored for billing purposes. Many apartment
houses, hotels, and corporations are now providing shared Internet access over DSL lines using
Ethernet and PPPoE.
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