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There are actually quite a lot of reverse proxy servers in use through large corporate networks performing a variety of purposes. However there are two distinct roles for which they are commonly used –
- replicating Content to geographically dispersed areas
- replicating content for load balancing
It’s a function that is not always considered for proxies, however content distribution is a logical function for any proxy server. In fact a reverse proxy server can even be used to establish multiple replica servers of a single master to diverse locations. Take for example if you have a multinational company with offices in countries all over the world.
It would be difficult for a single server with company wide data like templates, policies and procedures to server the entire company yet it is imperative that the integrity of any ‘copy’ is maintained. The reverse proxies could be set up in each branch server with a slightly different address, perhaps including location in name. These reverse proxies would pull their data from the master ensuring they were all identical.
This is quite an efficient use of the proxy in reducing bandwidth requirements across the network. However the reverse proxies must be configured to pull changes from the master very frequently in order to ensure any changes are replicated quickly. In fact it would be usually safer for the master server to push changes to the reverse proxies in order to ensure this.
The configuration can be complete by updating specific DNS entries in each zone. This would mean that you could resolve – www.master.com from all of the physical locations. That is to resolve london.master.com to point at the master server instead.
As mentioned the main issue is ensuring that changes are replicated efficiently and accurately. In fact replication is perhaps a little too advanced a term as really the proxies are merely caching information and updating them. So the master server has some modification to it’s content then it would push out the changes to any of the proxies online. So messages would be sent to the uk online proxy here, then to the asian proxy and so on.
THe other main use is of course load balancing for something like a heavily loaded web server. Any request received from a client will be distributed back to the multiple reverse proxies by using methods like DNS round robin. This ensure that the requests are spread out evenly and one of the reverse proxies doesn’t become overloaded with requests too. This often happened if static lists were used in rotation as the same proxy servers would be receiving the requests too frequently.
John Severn often sneaks off work to travel somewhere hot. After all he just needs to change ip address to United Kingdom and no-one will notice his emails are coming from the Costa del Sol next to a pool.