Bandwidth throttling
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Bandwidth throttling is a reactive measure employed in communication networks to regulate network traffic and minimize bandwidth congestion. Bandwidth throttling can occur at different locations on the network. On a local area network (LAN), a web administrator may employ bandwidth throttling to help limit network congestion and server crashes. On a broader level, the Internet Service Provider may use bandwidth throttling to help reduce a user's usage of bandwidth that is supplied to the local network. This can be used to actively limit a user's upload and download rates on programs such as BitTorrent protocols and other file sharing applications, as well as even out the usage of the total bandwidth supplied across all users on the network. Bandwidth throttling is also often used in Internet applications, in order to spread a load over a wider network to reduce local network congestion, or over a number of servers to avoid overloading individual ones, and so reduce their risk of crashing.
Operation
A computer network typically consists of a number of servers, which host data and provide services to clients. The internet is a good example, in which web servers are used to host websites, providing information to a potentially very large number of client computers.
Clients will make requests to servers, which will respond by sending the required data. As there will typically be many clients per server, the data processing demand on a server will generally be considerably greater than on any individual client. And so servers are typically implemented using computers with high data capacity and processing power.
The traffic on such a network will vary over time, and there will be periods when client requests will peak, sometimes exceeding the capacity of parts of network and causing congestion, especially in parts of the network that form bottlenecks. This can cause data request failures, or in worst cases, server crashes.
In order to prevent such occurrences, a server administrator may implement bandwidth throttling to control the number of requests a server responds to within a specified period of time.
When a server using bandwidth throttling reaches the specified limit, it will offload new requests and not respond to them. Sometimes they may be added to a queue to be processed once the bandwidth use reaches an acceptable level, but at peak times the request rate can even exceed the capacities of such queues and requests have to be thrown away.
Application
A bandwidth intensive device, such as a server, might limit, or throttle, the rate at which it accepts data, in order to avoid overloading its processing capacity. This can be done both at the local network servers or at the ISP servers. Two ISP's, Cox and Comcast, have stated that they engage in this practice, where they limit users' bandwidth by up to 99%. [1] Today most if not all Internet Service Providers throttle their users bandwidth, with or without the user ever even realizing it. [2]
Network Neutrality
Net Neutrality is the guiding principle that preserves the free and open Internet. Net Neutrality means that Internet service providers may not discriminate between different kinds of content and applications online. It guarantees a level playing field for all Web sites and Internet technologies. With Net Neutrality, the network's only job is to move data -- not to choose which data to privilege with higher quality service.
Throttling vs. Capping
Bandwidth throttling works by limiting (throttling) the rate at which a bandwidth intensive device (a server) accepts data. If this limit is not in place, the device can overload its processing capacity.
Where as a bandwidth cap limits the transfer of a specified amount of data over a period of time. There are two types of bandwidth capping. A standard cap limits the bitrate or speed of data transfer on a broadband internet connection. Standard capping is used to prevent individuals from consuming the entire transmission capacity of the medium. A lowered cap reduces an individual user’s bandwidth cap as a defensive measure and/or as a punishment for heavy use of the medium’s bandwidth. Sometimes this happens without notifying the user.
The difference is that bandwidth throttling regulates a bandwidth intensive device (such as a server) by limiting how much data that device can accept or receive. Bandwidth capping on the other hand limits the total transfer capacity, upstream or downstream, of data over a medium.
ISP Bandwidth Throttling
United States
In 2008, Comcast amended their Acceptable Usage Policy and placed a specific 250 GB monthly cap in an attempt to constrain excessive bandwidth users. Comcast has also announced a new bandwidth-throttling plan. The scheme includes a two-class system of Priority-best-effort and best-effort where “sustained use of 70% of your up or downstream throughput triggers the BE state, at which point you'll find your traffic priority lowered until your usage drops to 50% of your provisioned upstream or downstream bandwidth for "a period of approximately 15 minutes." A throttled Comcast user being placed in a BE state "may or may not result in the user's traffic being delayed or, in extreme cases, dropped before PBE traffic is dropped." Comcast explained to the FCC that “If there is no congestion, packets from a user in a BE state should have little trouble getting on the bus when they arrive at the bus stop. If, on the other hand, there is congestion in a particular instance, the bus may become filled by packets in a PBE state before any BE packets can get on. In that situation, the BE packets would have to wait for the next bus that is not filled by PBE packets. “ [3]
Canada
In 2008, the Canadian Radio-television and Telecommunications Commission (CRTC) famously decided to allow Bell Canada to single out P2P traffic for bandwidth throttling between the hours of 4:30pm to 2am. [4]
ISP's in Canada that currently throttle bandwidth: [5]
- Bell Canada: Yes (only P2P between 4:30pm and 2am)
- Cogeco Cable: Yes
- MTS Allstream: No
- Rogers Cable: Confidential (but probably yes)
- Saskatchewan Telecom: No
- Primus Telecom: No
- Shaw: Yes
- Barrett Xplore: Yes, and also prioritizes VoIP
- TELUS: No
- Bragg: Confidential
Workarounds For Bandwidth Throttling
Although ISP's may actively throttle bandwidth, there are several known methods to bypass the throttling of a user's bandwidth. These methods include:<ref>Remisser. "Workarounds For Bandwidth Throttling". Retrieved April 26, 2011.
- Virtual Private Network (VPN) - Generally cost a monthly fee to rent, but offers users a secure connection where data cannot be intercepted.
- Force Encryption <ref>"Optimize BitTorrent to outwit traffic shaping ISPs". Retrieved April 26, 2011. - Free method that works for some users.
- Seedbox - A dedicated private server, usually hosted offshore, that offers high speed upstream and downstream rates and often storage for a relativly high monthly cost.
- SSH Tunneling - Tunneling Protocol
See also
References
- ^ Max Planck Institute (March 18th, 2008). "Glasnost: Results from tests for BitTorrent traffic blocking". Retrieved April 3, 2011.
{{cite web}}: Check date values in:|date=(help) - ^ netequalizer (March 21, 2009). "Is Your ISP Throttling Your Bandwidth?". Retrieved April 3, 2011.
- ^ Karl Bode (January 5, 2009). "New Comcast Throttling System 100% Online". Retrieved March 14, 2011.
- ^ Nate Anderson (2009). "Canadian regulators allow P2P throttling". Retrieved April 3, 2011.
- ^ Nate Anderson (2009). "How Canadian ISPs throttle the Internet". Retrieved April 3, 2011.
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