TCP and UDP,ICMP and IPSEC PROTOCOLS

TCP and UDP

TCP and UDP are used by applications. An application server typically listens at a fixed TCP or UDP port, while application clients typically use any of a wide range of ports—and as with other aspects of firewall rulesets, deny by default policies should be used for incoming TCP and UDP traffic.

Less stringent policies are generally used for outgoing TCP and UDP traffic because most organizations permit their users [..]

Architecture with Multiple Layers of Firewalls

There is no limitation on where a firewall can be placed in a network. While firewalls should be at the edge of a logical network boundary, creating an “inside” and “outside” on either side of the firewall, a network administrator may wish to have additional boundaries within the network and deploy additional firewalls to establish such boundaries.

The use of multiple layers of firewalls is quite common to provide defense-in-depth. For [..]

Intranet VPN

Many VPNs, of different companies, can be created on the same shared IP backbone infrastructure of a Service Provider. This is one of the reasons why VPNs are far less expensive for companiesthan full private networks based on a WAN infrastructure.

A complete VPN solution therefore incorporates encrypted tunneling, QoS,security, management, and provisioning capabilities, to create a reliable [..]