A gateway is a network element that connects two different networks, even if they use different protocols. It allows communication by stripping off the old protocol and assigning a new protocol. There are two main types of gateways: transport gateways connect networks using different transport protocols, while application gateways can translate between application-layer formats. Gateways expand networks but have drawbacks like inability to filter noise, slower transmission due to protocol conversion, and increased cost.

2. GATEW
AY
AN INTRODUCTION

3. Definition…
 A gateway is a network element that acts as an entrance point to
another network. For example an access gateway is a gateway
between telephony network and other network such as internet.
 A gateway is generally a work station or server. It is a two-way path
between networks. It is used to connect different types of networks.
 Gateway is a work station by which we can make out connection
between external network and internal network.
 Gateway belongs to transport layer and application layer of the OSI
model.

4. Working…
 Gateways connect the two networks even if the protocols are
different. So protocol conversion is also done by gateways
 It simply stripped off the old protocol and assigns new protocol to
the packets, so it is also called protocol translator
 Gateways are the simple junctions between two network
architectures. They repackage and convert data going from one
environment to another so that one environment can understand the
other environments data
 A gateway links two systems which have different communication
protocols, different language and different architecture

5.  Gateways never filter out the data. So it passes bad packets too.
 Gateways are task specific. So they are dedicated to a particular
type of transfer. They often referred to by their particular task name.
 Example:- Windows NT server to SNA gateway.
 LANs may have component called gateways, which assists in
transferring from one LAN to another LAN.
 Because it takes it time for protocol conversion, it is little bit slower.

6. Types…
 Basically there are two types of gateways (1) Transport gateway and
(2) application gateway. The former is for transport layer and the
later is for application layer.
TRANSPORT GATEWAY
 Transport gateways connect two computers that use different
connection oriented transport protocol. It can copy the packets to
one connection to other, reformatting them as need be.
Application Gateway
 Application gateways understand the format and contents of the
data and translate messages from one form to another e.g. an e-mail
gateway could translate internet messages to an SMS messages on
mobile phone.
 So it identifies the actual meaning of data.

7. Benefits of GATEWAY…
 Used to expand the network.
 Gateway is a server so it provides some security.
 We can connect two different types of networks.
 Protocol conversion is done.
 Effectively handles the traffic problems.
 And also establishes connections between internal network and
external network.

8. Drawback of GATEWAY…
 Not an intelligent device. So noise prevention is not done.
 Never filter out the data
 Some what costly
 Protocol conversion is done so transmission rate is slower.
 Some what hard to handle.