|Topics and issues|
Bandwidth throttling is the intentional slowing of internet service by an internet service provider. It is a reactive measure employed in communication networks in an apparent attempt 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 sysadmin 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.
Throttling can be used to actively limit a user's upload and download rates on programs such as video streaming, 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, and gain additional revenue by compelling users on to more expensive pricing schemes where bandwidth is not throttled.
- 1 Operation
- 2 Application
- 3 Network neutrality
- 4 Throttling vs. capping
- 5 Court cases
- 6 ISP bandwidth throttling
- 7 Metrics for ISP bandwidth throttling
- 8 Workarounds for bandwidth throttling
- 9 See also
- 10 References
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.
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. ISPs often employ deep packet inspection (DPI), which is widely available in routers or provided by special DPI equipment. Additionally, today’s networking equipment allows ISPs to collect statistics on ﬂow sizes at line speed, which can be used to mark large ﬂows for traffic shaping. Two ISPs, Cox and Comcast, have stated that they engage in this practice, where they limit users' bandwidth by up to 99%. Today most if not all Internet Service Providers throttle their users' bandwidth, with or without the user ever even realizing it. In the specific case of Comcast, an equipment vendor called Sandvine developed the network management technology that throttled P2P file transfers.
Those that could have their bandwidth throttled are typically someone who is constantly downloading and uploading torrents, or someone that just watches a lot of online videos. Many consider this as an unfair method of regulating the bandwidth because consumers not getting the required bandwidth even after paying the prices set by the ISPs. By throttling the people who are using so much bandwidth, the ISPs enable their regular users to have a better overall quality of service.
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.
Contrary to throttling, in order to use bandwidth when available, but prevent excess, each node in a proactive system should set an outgoing bandwidth cap that appropriately limits the total number of bytes sent per unit 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.
Comcast Corporation vs. FCC and U.S.
In 2007, Free Press and Public Knowledge, along with the Federal Communications Commission, filed a complaint against Comcast’s Internet service. Several subscribers claimed that the company was interfering with their use of peer-to-peer networking applications. The Commission stated that it had jurisdiction over Comcast’s network management practices and that it could resolve the dispute through negotiation rather than through rulemaking. The Commission believed that Comcast had “significantly impeded consumers’ ability to access the content and use the applications of their choice”, and that because Comcast “ha[d] several available options it could use to manage network traffic without discriminating” against peer-to-peer communications, its method of bandwidth management “contravene[d] . . . federal policy”. At this time, “Comcast had already agreed to adopt a new system for managing bandwidth demand, the Commission simply ordered it to make a set of disclosures describing the details of its new approach and the company’s progress toward implementing it.” Comcast complied with this Order but petitioned for a review and presented several objections.
ISP bandwidth throttling
In 2008, the Canadian Radio-television and Telecommunications Commission (CRTC) decided to allow Bell Canada to single out P2P traffic for bandwidth throttling between the hours of 4:30 pm to 2 am.
In 2009, the CRTC released a guideline for bandwidth throttling rules.
In 2011, following a major complaint by the Canadian Gamers Organization against Rogers for breaking the 2009 rules already in place, the CRTC created an addendum to their ITMP policy, allowing them to send the complaint to their Enforcements Division. The Canadian Gamers Organization in their submissions alluded to filing a complaint against Bell Canada. On December 20, 2011, Bell Canada announced they would end throttling by March 31, 2012 for their customers, as well as their wholesale customers. On February 4, 2012, in an effort to get out of trouble with the CRTC (which had continued its own testing and had found additional non-compliance and demanded immediate compliance), Rogers announced 50% of their customers would be throttle-free by June 2012, and 100% of their customers would be throttle-free by the end of 2012. Unfortunately for Rogers, this did not mollify the CRTC Enforcements Division.
ISPs in Canada that throttle bandwidth:
- Bell Canada: Yes
- Cogeco Cable: No
- MTS Allstream: Yes (between 4pm and midnight)
- Rogers Cable: Yes - to be phased out completely by end of 2012
- Saskatchewan Telecom: Yes
- Primus Telecom: No
- Shaw: Yes(25% of the traffic)
- Barrett Xplore: Yes, and also prioritizes VoIP
- TELUS: Yes(2% of the traffic)
- Bragg: Yes - The public statement was "Confidential".
- Teksavvy Cable: No
- Teksavvy DSL: No
- Teksavvy DSL MLPPP: No
- Talk Wireless Inc: Yes
In 2007, Comcast took steps to ease network congestion by interfering with peer-to-peer traffic. Specifically, it falsified packets of data that fooled users and their peer-to-peer programs into thinking they were transferring files. Comcast initially denied that it interfered with its subscribers’ uploads, but later admitted it. The FCC held a hearing and concluded that Comcast violated the principles of the Internet Policy Statement because Comcast’s “discriminatory and arbitrary practice unduly squelched the dynamic benefits of an open and accessible Internet and did not constitute reasonable network management.” The FCC also provided clear guidelines to any ISP wishing to engage in reasonable network management. The FCC suggested ways that Comcast could have achieved its goal of stopping network congestion, including capping the average user’s capacity and charging the most aggressive users overage fees, throttling back the connections of all high capacity users, or negotiating directly with the application providers and developing new technologies.
However, 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." 
In April 2011, the European Union launched an investigation into internet service providers’ methods for managing traffic on their networks. Some ISPs, for instance, restrict access to services such as Skype or the BBC iPlayer at peak times so that their users all receive an equal service. The EU's commissioner for the digital agenda, Neelie Kroes, said: "I am absolutely determined that everyone in the EU should have the chance to enjoy the benefits of an open and lawful internet, without hidden restrictions or slower speeds than they have been promised.” The Body of European Regulators for Electronic Communications (Berec) will examine the issues for the EU, and will ask both businesses and consumers for their views. The EU will publish the results of its investigation by the end of 2011.
This small South American country is an interesting case study in that it has a unique ISP for all non-wireless Internet connectivity (Antel) which enjoys a state-enforced monopoly. Consumers who want any flavor of internet connectivity other than wireless (i.e. ADSL or fiber, as Cable Internet is outlawed) have to buy it from Antel. Thus the company provides a peek into the probable behavior of market-economy ISPs if they didn't have to worry about competition or pro-consumer government regulation. Antel offers no truly unlimited data plans to consumers, all its plans are capped or throttled in some way. Capped plans typically go by the moniker of "flexible". Once the user reaches a first data cap (e.g. 5GB) they get billed for any additional data at a rate of approximately 5 u$s/GB. That "flexibility" continues until a second cap (e.g. 15GB) at which point the connection stops working entirely until the start of the next billing month. Throttled plans work in a slightly more forgiving way and typically go by the moniker "flat rate". With these plans when the user hits the data cap for the plan (e.g. 150GB for a 20Mbs fiber connection) the connection goes on but its speed gets throttled back (e.g. to 2Mbs, 10% of the advertised speed) until the start of the next billing month.
Metrics for ISP bandwidth throttling
Whether aimed at avoiding network congestion or at pushing users to upgrade to costlier Internet plans, the increasingly common capping and throttling practices of ISPs undoubtedly have an effect on the value proposition of the plans they offer. For consumers to be able to make an informed decision when choosing an Internet plan, ISPs should publish their capping and throttling practices with the necessary level of detail. While the net effect of some throttling and capping strategies can be hard to compare across ISPs, some basic metrics that are of interest for any kind of throttled/capped Internet connection are:
- Maximum monthly payload: This is the amount of data that an Internet connection would be able to carry in a hypothetical setting assuming no bottlenecks external to the ISP. In the example Antel 20Mbs fiber connection (see Uruguay above), the maximum monthly payload in that hypothetical setting would be reached by running the connection at 20Mbs for the first 150 GB, and at 2Mbs for the rest of the month. Thus the maximum monthly payload of that connection is 60,000 seconds * 2.5 MB/s + 2,532,000 seconds * 0.25 MB/s = 783 GB (about the size of a large laptop disk drive in 2013.)
- Maximum utilization percentage: This is the ratio of the maximum monthly payload of a throttled Internet connection to the maximum unthrottled monthly payload of the same connection. In the example Antel fiber 20Mbs connection the maximum unthrottled monthly payload of that connection is 2,592,000 seconds * 2.5 MB/s = 6,480 GB. Thus the maximum utilization percentage of that connection is 783 GB / 6,480 GB = 12%
- Throttling percentage: This represents how much the maximum monthly payload of an Internet connection gets reduced by the ISP's throttling policy. It is calculated simply as 1 - maximum utilization percentage. In the example Antel fiber 20Mbs connection it is 1 - 12% = 88%
- Equivalent connection bandwidth: This is the bandwidth of an unthrottled Internet connection whose maximum monthly payload is the same as the maximum monthly payload of the throttled connection in question. This can be calculated as unthrottled connection bandwidth * throttling percentage. In the example Antel fiber 20Mbs connection the equivalent connection bandwidth is 20 Mbs * 12% = 2.4 Mbs
- Cost per unit payload: The ultimate metric of throttling's effect on an Internet connection's potential value to a customer is the cost per GB (or TB in the case of fast connections) carried assuming perfect utilization of the connection. It is calculated by dividing the monthly cost of the connection by the maximum monthly payload. In the example Antel fiber 20 Mbs connection it would be u$s 36 / 0.783 TB = u$s 46 per TB. By comparison, if the same 20Mbs connection weren't throttled by the ISP it would have a cost per unit payload of u$s 36 / 6.48 TB = u$s 5.6 per TB
- Unthrottled connection cost: This is how much it would cost the customer to offset the effect of throttling by aggregating throttled Internet connections from the ISP. It is calculated by dividing the monthly cost of a throttled connection by the throttling percentage. In the example Antel fiber connection the cost of building an unthrottled 20Mbit/s fiber Internet connection by aggregating 20Mbit/s throttled ones would be u$s 36 / 12% = u$s 300 per month
Workarounds for bandwidth throttling
Although ISPs may actively throttle bandwidth, there are several known methods to bypass the throttling of a user's bandwidth, if the throttling is focused on a particular protocol. These methods include:
- Virtual Private Network (VPN) - Generally cost a monthly fee to rent, but offers users a secure connection where data cannot be intercepted.
- Force Encryption  - 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 relatively high monthly cost.
- SSH Tunneling - Tunneling protocol
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- Comcast vs. FCC & U.S., 08-1291 Chief Judge Tatel (U.S. Court of Appeals April 6, 2010).
- Nate Anderson (2009). "Canadian regulators allow P2P throttling". Retrieved April 3, 2011.
- CRTC (2009). "Telecom Regulatory Policy CRTC 2009-657". Retrieved April 21, 2012.
- CRTC (2011). "Internet traffic management practices – Guidelines for responding to complaints and enforcing framework compliance by Internet service providers". Retrieved April 21, 2012.
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- Peter Svensson (10/19/200). "Comcast blocks some Internet traffic". Associated Press. Archived from the original on 7 May 2011. Retrieved May 3, 2011.
- Declan McCullagh (8/1/2008). "FCC formally rules Comcast's throttling of BitTorrent was illegal". CNET News. Retrieved May 3, 2011.
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- Matt Warman (April 20, 2011). "EU launches net neutrality investigation". The Telegraph. Retrieved May 3, 2011.
- Only Cuba and Uruguay don't offer Internet access via cable modem (In Spanish)
- Telecommunications in Uruguay
- Planes de Internet - Antel
- Remisser. "Workarounds For Bandwidth Throttling". Retrieved April 26, 2011.
- "Optimize BitTorrent to outwit traffic shaping ISPs". Retrieved April 26, 2011.