Speaking and Writing Homework How Corporate Firewalls Work

1. How Corporate Firewalls Work
Bastion host
Proxy server
Access router
Protocol

2. An exterior screening router(also called an access router), are
located at customer sites such as branch offices that do not
need hierarchical routing of their own. Typically, they are optimized
for low cost.
An exterior screening router

3. Protocol
In computing, a protocol is a set of rules which is used
by computers to communicate with each other across a network.
A protocol is a convention or standard that controls or
enables the connection, communication, and data transfer between
computing endpoints. In its simplest form, a protocol can be
defined as the rules governing the syntax, semantics, and
synchronization of communication. Protocols may be implemented
by hardware, software, or a combination of the two. At the
lowest level, a protocol defines the behavior of a hardware connection.

4. A bastion host is a special purpose computer on a network specifically designed
and configured to withstand attacks. The computer generally hosts a single
application, for example a proxy server, and all other services are removed
or limited to reduce the threat to the computer. It is hardened in this manner
primarily due to its location and purpose, which is either on the outside of the
firewall or in the DMZ and usually involves access from untrusted networks
or computers.
Bastion host

5. A proxy server is a server that acts as a go-between for requests from clients
seeking resources from other servers. A client connects to the proxy server,
requesting some service, such as a file, connection, web page, or other resource,
available from a different server. The proxy server evaluates the request according
to its filtering rules. For example, it may filter traffic by IP address or protocol.
Proxy server

6. References
http://en.wikipedia.org/wiki/
http://images.google.co.jp/