A gateway is a network point that provides entrance into 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.
A firewall is a hardware or software installed to provide security to the private networks connected to the internet. They can be implemented in both hardware and software, or a combination of both. All data entering or leaving the Intranet passes through the firewall which allows only the data meeting the administrators’ rules to pass through it.
Packet Filtering Firewall:
This type of Firewall detects packets and block unnecessary packets and makes network traffic release.
Screening Router Firewalls:
It's a software base firewall available in Router provides only light filtering.
It's a firewall stored in server with an existing Operating System like Windows and UNIX.
Hardware base Firewall:
Its device like box allows strong security from public network. Mostly used by big networks.
Proxy server allows all clients to access Internet with different access limits. Proxy server has its own firewall which filters the all packet from web server.
Data encryption ensures data safety and very important for confidential or critical data. It protect data from being read, altered or forged while transmission.
Public key encryption use public and private key for encryption and decryption. In this mechanism, public key is used to encrypt messages and only the corresponding private key can be used to decrypt them. To encrypt a message, a sender has to know recipient’s public key.