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I need some help understanding firewalls.

I played around with Amazon EC2 and it seems to provide a firewall out-of-the-box. When I say firewall, to me that means the ability to block ports from being accessed from the outside world, or to only specific security groups.

I'm looking at a dedicated server hosting provider and they provide a hardware firewall for $50/month and it is limited to 10mbps. Can someone explain to me what kind of traffic this correlates to? Are these usually limited to the number of simultaneous connections also?

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up vote 6 down vote accepted

I've never seen a firewall option limited by the number of simultaneous connections, but the one and only way to find out for sure is to directly ask your hosting provider. Get it in writing, not just over the phone. And if you talk to them over the phone, ask the tech for his email address so you can send him a summary of the conversation and get a positive response from him that indeed, those topics and conclusions were discussed.

As for how fast is 10Mbps, let's do some simple maths:

  • 1 megabit is 131,072 bytes
  • Thus, 10 megabits is 1,310,720 bytes
  • 1,310,720 bytes is 10,240 kilobits
  • 10,240 kilobits is 1,280 kilobytes
  • 1,280 kilobytes is 1.25 megabytes

Is 1.25 megabytes per second acceptable? Only you can answer that. If you have a site that has any amount of rich content, it's going to get saturated pretty fast. However, some reverse proxies and caching magic and you might be able to handle it pretty well.

The question remains, what kind of site and content are you going to be delivering? Build it and test what kind of kb load an average pageload costs and then extrapolate to logical conclusions.

In my completely arbitrary opinion based on no facts about your site, 10Mbps seems pretty slim.

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Elaborate maths, still valid :-) – Joris Mar 6 '11 at 8:29

Depending on your skill and hosting provider, you can generally setup host based firewall/port filtering (iptables on Linux, Windows Firewall, etc) for no charge. You would choose a hardware firewall for an additional measure of protection, or to mitigate certain types of attacks. Generally one is not required (I prefer hardware firewall for Windows, and generally stick to software firewalls and disabling services for Linux. YMMV.)

If you go with a hardware firewall it should be matched to the bandwidth allocation and usage of the site. 10mb is reasonably large for a single server and a small to midsized site, depending on the site itself.

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10Mbps can serve a good amount of traffic but it depends on what you are serving. For example, I have standard MediaWiki serving up to 1 million pages/day that averages a net of only 6Mbps. If, however, I was hosting a file download or video site I would need probably 10 times that amount to serve the same number of users. If hosting a "standard" web site you can use cache/expires headers to greatly reduce the amount downloaded for repeat users.

When looking at your average transfer rate don't forget to consider what your peak rate needs to be. The exact amount will depend on the type of content you host and the type of users you attract. For example, I frequently see peak rates twice that of the average. This means if I only had a 10Mbps line I would saturate it easily during peak hours.

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wow, what kind of server does that take? – Blankman Mar 6 '11 at 17:04
It is actually spread out on 6 servers from a CPU/RAM and load balancing/availability standpoint. The net bandwidth to/from all the servers combined averages 6Mbps plus 1-2Mbps for internal server traffic. Technically it could be all run from one mid-high end machine relatively easily. – uesp Mar 6 '11 at 18:24
Another thing to consider for a dedicated server is the monthly bandwidth allowance. Typically it is a few TB a month with a relatively high per GB rate if you exceed it. A fully used 10Mbps connection is around 3TB a month. If you get a server with only 1TB/month but use 2-3TB you're going to be paying an arm and a leg for it. A 100Mbps connection is nice but the price to use the full 30TB of bandwidth a month won't be cheap. – uesp Mar 6 '11 at 18:30

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