Hello, and this is sunny, welcome back. Internet is a private network which is heavily protected by many different networking devices such as a router, firewall, proxy server, DMZ, honeynet, IPs, and IDs. This diagram is an overly simplified version of the reality. I try to pull these devices together in a reasonable order only for teaching and learning purposes. Today, my topic is proxy server.
A proxy server is a mediator between the external and internal networks, screening all incoming and outgoing traffic. A proxy server has at least 5 functions. 1) A proxy server acts as an agent on behalf of its clients. When clients make requests to a web server, for example, the proxy server uses its own IP address to replace his client's IP address. When the page is returned, the proxy server forwards it to the client. In this way, the proxy server hides the IP addresses of his clients. This function is called network address translation or NAT. This NAT function is more commonly performed by routers or firewalls.
A proxy server can act as a caching machine. For example, if a client wants the latest version of Firefox, the proxy first checks its cache. If it hasn't found it in its storage, it will download a copy from the Internet. Next time when the client asks for a copy of Firefox, the proxy server checks its cache and gives the copy directly from its cache. Thus, it reduces network traffic and improves network performance.
Proxy servers can control traffic both inbound and outbound. For example, if a company prohibits its employees from going to some social media sites like Facebook or YouTube during work hours, they can simply deploy a proxy server to control outbound traffic. This can be set up simply by blocking IP addresses of these social media sites. Proxy servers can keep track of all traffic, both outgoing and incoming. Last but not least, a proxy server can be set up to bypass the firewall. This function is very different from its normal setup. Suppose I'm sitting in my school office using my school's private network and I want to check my Facebook. But my school firewall blocks the Facebook site, so I cannot connect with my friends. I decide to buy a proxy server and install it in my garage. I work day and night to ensure it functions properly. Now, when I come back to my school office, I don't go to the Facebook site directly. Instead, I log on to my practice server in my garage and ask my proxy server to access Facebook. My proxy server connects to Facebook. As long as my school does not block my proxy server, I will have no problem checking my Facebook through my proxy. This method is called bypassing the firewall or climbing over the great wall. Keep in mind there are many types of proxy servers with many different functions. I hope this video is helpful to understand the basics. Thank you very much, and I'll see you next time.
Q: What is a proxy server?
A: A proxy server is a mediator between the external and internal networks, screening all incoming and outgoing traffic. It can hide the IP addresses of clients and has functions such as network address translation.
Q: How does a proxy server act as a caching machine?
A: A proxy server can store copies of requested content in its cache. When a client requests the same content again, the proxy server can provide it from its cache, reducing network traffic and improving performance.
Q: What are some functions of a proxy server?
A: Some functions of a proxy server include acting as an agent on behalf of clients, controlling traffic both inbound and outbound, and bypassing firewalls to access restricted sites.
