学校的网速相当的快，下载东西的速度一般可以达到500kb/s以上。但是学校为了保证大家都能用上高速通畅的网络，也对于连续下载大文件有一些限制措施。这条信息原本刊登在学校housing的网站上，但是不太好找，很多同学都不知道，所以转贴到这里。学校的housing甚至还提供了一个流量监控的widget供你下载。
学校并没有直接限制你的总流量。学校的policy是，你耗费的流浪的越多，网速就越慢。
Why Does RESnet Have a Bandwidth Policy?
Housing provides high-speed Internet access as a service to all of our residents. Unfortunately, all of the bandwidth used by that service costs a lot of money, and our hardware can only support so much traffic from everyone at any given time. If every student were to use all of the bandwidth available to them 24 hours a day, our network would become unusable. Furthermore, the bandwidth used by RESnet is only a piece of the bandwidth used by the entire University. This includes all residence halls, university teaching departments, university operation departments, and users.
To keep RESnet bandwidth from overwhelming the network, Housing has instituted a set of rate limits that gradually limit the connections of the highest-traffic users on RESnet, and keep the network working well for everyone. This allows us to efficiently use our limited bandwidth resources, and continue providing high-speed access to everyone.
Rate Limiting Definitions
Rate limiting is the system that is used on RESnet to regulate high-traffic users. The basic idea behind rate limiting is that the more traffic you generate, theslower your connection will become. Rate limiting was implemented as a way of allowing residents to download large files while still being allowed to use the Internet. If you start a http download and then cancel it, your “traffic account” will be charged with the full file size. Except in severe cases, Housing does notdisable connections for excessive traffic.
RESnet tracks traffic over a moving 24-hour period. What this means is that your limit class will be determined by the amount of traffic you have done in the past 24 hours. We currently have three limit classes that your connection can be placed in:
Unrestricted Class (10 Mb/s): All connections are in this class by default. Connections in this class are not artificially limited or throttled.
Restricted Class A (1 Mb/s download aggregate & 32 kb/s upload per flow): Connections will be limited when they reach a total of 2GB of traffic in the past 24 hours.
Restricted Class B (128 kb/s download aggregate & 128 kb/s upload aggregate): Connections will be further limited when they reach a total of 5GB of traffic in the past 24 hours.
Aggregate means that your bandwidth is shared among all of the connections in your Restricted Class.
Rate limit classes affect your computer only – your roommate(s) have separate traffic records and will not be rate limited if you go over your limits. Rate limits affect all of your traffic, both on-campus and off-campus. You may be disconnected or contacted if we feel you are abusing the bandwidth policy by changing your MAC address or if we see continually heavy traffic (ie. in Class B for days at a time, etc…)
Monitoring Your Bandwidth
To view your traffic over the past 24 hours, as well as information on what limit class you are in, you can visit this page. There are a few things about this page that merit explanation. First, the page reports both your input and output. Input is data coming from your computer, and output is data coming into your computer. Our rate limit thresholds are based on the total of these two traffics, which can be seen at the bottom of the page. This page reports your traffic inbytes. The limits of 2000MB and 5000MB are equal to 2,000,000,000 and 5,000,000,000 bytes, respectively. Flows are another way of representing web traffic. You will not be rate limited based on flows. Please note: if you download a file via http and then cancel it mid download you will see the full file size reflected on the traffic pages.
As you can see in the following picture, the computer has been ratelimited for heavy traffic. Numbers in red are highlighted because the ratio of input to output matches the ratios that are often seen when filesharing programs are in use. The computer moved from unrestricted, to class A, then into class B when the heavy traffic continued.
Only traffic between your computer and a computer off campus will be represented on this page. This means that traffic that does not leave campus will not be counted against your totals for rate limits. There is no absolute way to tell what traffic is considered on or off campus, but a good guideline is that most web addresses that end in “.uiuc.edu” are on campus.
If you want a more real-time count of your traffic, visithttp://flowstats.cites.uiuc.edu/cgi-bin/traffic.cgi. Note this count will always be lower than the number that determines your rate limit class.
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