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Learn How Network Congestion Management Affects Your Internet Use

Managing the network helps ensure fair use of the Internet by all Comcast customers.

Comcast is committed to providing the best online experience possible for all our customers, using reasonable network management practices that are consistent with industry standards. We invite our XFINITY Internet customers to review the Acceptable Use Policy. The following is intended to help clarify what we mean by network management.

Why Comcast Manages its Network

Comcast manages its network with one goal: to deliver the best possible broadband Internet experience to all of our customers. High-speed bandwidth and network resources are not unlimited. Managing the network is essential to promote the use and enjoyment of the Internet by all of our customers.

All Internet service providers need to manage their networks, and Comcast is no different. If we didn't, customers would be subject to the negative effects of spam, viruses, security attacks, network congestion and other degradations of service. By engaging in reasonable and responsible network management, Comcast can deliver the best possible broadband Internet experience.

How Comcast Manages its Network

Comcast uses various tools and techniques to manage the network, deliver service, and ensure compliance with the Acceptable Use Policy. Like the network, these tools are dynamic and change frequently. Network management activities may include identifying spam and preventing its delivery to customer email accounts, and detecting malicious Internet traffic and preventing the distribution of viruses or other harmful code or content.

Changes in Network Management Over Time

As the Internet and its related technologies continue to evolve, Comcast's network management tools will also keep pace so we can deliver an excellent, reliable and safe experience to all of our customers. We will provide updates here as well as other locations if we make significant changes to our network management techniques.

Comcast's Current Congestion Management Technique

If a certain area of the network nears a state of congestion, our congestion management technique will ensure that all customers have a fair share of network access. This technique will identify which customer accounts are using the greatest amounts of bandwidth, and their Internet traffic will be temporarily managed until the congestion period passes. Customers will still be able to do anything they want online, but they could experience longer times to download or upload files or slower web surfing.

Our technique does not manage congestion based on specific online activities, protocols or applications that a customer uses. Rather, it only focuses on the heaviest users in real time, so that congestion periods tend to be fleeting and sporadic.

It is important to note that the effect of this technique is temporary and has nothing to do with a customer’s aggregate monthly data usage. Rather, it’s dynamic and based on prevailing network conditions as well as a customer’s data usage over a very recent period of time.

Comcast will periodically update the congestion management system configuration to improve the efficacy of the platform but this will not impact specific online activities, protocols or applications that a customer uses.

Our congestion management system was disclosed in detail in 2008 to the Federal Communications Commission and this filing has since been disclosed in an Internet Engineering Task Force (IETF) document in RFC 6057.

Targets of Congestion Management

Our current technique is "protocol-agnostic," which means the system does not manage congestion based on the application(s) being used. It is also content neutral, and does not depend on the type of content that is generating traffic congestion. Simply put, congestion-managed traffic is not based on specific applications or content, but on current network conditions and recent amounts of data transferred by users.

Impacts on XFINITY Internet Service

Based on our experience, the large majority of our customers will notice no change in their Internet experience. In fact, we find that on average less than one percent of our high-speed Internet customers are affected by the congestion management approach. Our experience also shows that when the congestion management technique is applied to an individual user’s account, it is usually only for a very brief period of time.

Frequency of Congestion Management

Comcast has determined that select portions of the network tend to be congested only for small portions of the day, if at all.

We constantly monitor how user traffic is affected by this system and will make reasonably necessary adjustments to ensure that our XFINITY Internet customers enjoy a high-quality online experience. Comcast also routinely evaluates its overall network performance and periodically enhances its network by adding capacity to address congestion and other performance issues.

"Real World" Types of Bandwidth Consumption That Might be Considered Too Much

This answer depends on a number of factors, including overall usage, time of day, and the number of applications a customer might be running. First, the local network must be approaching a congested state for our technique to even look for traffic to manage. Assuming that is the case, customers’ accounts must exceed a certain percentage of their upstream or downstream bandwidth (both currently set at 70%) for longer than a certain period of time, currently set at 15 minutes.

A significant amount of normal Internet usage by our customers does not last that long. For example, most downloads would have completed within that time, and the majority of streaming and downloading will not exceed the threshold to be eligible for congestion management. And the majority of longer-running applications such as VoIP, video conferencing, and streaming video content (including HD streaming on most sites) will not exceed these thresholds either.

The point of the technique is to deliver the best online experience possible. Congestion management should help ensure that all customers get their fair share of bandwidth resources to enjoy all that the Internet has to offer, including surfing the web, reading email, downloading movies, watching streaming video, gaming, or listening to music.

Customer Notification and Services Affected

The congestion management technique applies to both commercial and residential services, as well as our XFINITY WiFi service.

We believe congestion notification should be an Internet standard and have been discussing this issue with technical bodies like the IETF. The Congestion Exposure (CONEX) working group at the IETF is currently considering this issue.

Congestion Management and High Usage Patterns

The two are completely separate and distinct. Our new congestion management technique is based on real-time Internet activity. The goal is to avoid congestion on our network that is caused by the heaviest users. The technique is different from the current AUP policy, which permits Comcast to consider usage as an indication of a security or related issue, requiring customer outreach to help address the issue. 

XFINITY Voice Services Affected by Our Congestion Management Technique

XFINITY Voice and Comcast Digital Voice are separate, facilities-based IP phone services that are not affected by this technique. This phone service also does not affect the last mile capacity for, or the performance of, the XFINITY Internet service.

Comcast customers who use VoIP providers that deliver calls over the public Internet who are also using a disproportionate amount of bandwidth during congestion management period may experience a degradation of call quality at times of network congestion. (It is important to note, however, that VoIP calling in and of itself does not use a significant amount of bandwidth). Furthermore, our experience with this technique does not indicate any significant change in the quality of VoIP calls, even for managed customer traffic during periods of congestion.

Congestion Management and XFINITY TV, Xfinity.com/tv, Streaming Video and Video Downloads

During periods of congestion, any customer who uses a disproportionate amount of bandwidth (no matter what type of content or online activity) may be affected by this technique. (It does not matter, for example, if the content is coming from a Comcast-owned site like XFINITY TV and xfinity.com/tv or not).

Our technique has no ability to determine the applications or protocols being used or the content, source or destination.

Types of Content Affected by Congestion Management

Comcast does not block P2P traffic or applications like BitTorrent, Gnutella, or others as part of its current network congestion management technique.

Comcast provides its customers with full access to all the lawful content, services, and applications that the Internet has to offer. However, we are committed to protecting customers from spam, phishing, and other harmful online activity. Comcast uses industry standard tools and generally accepted best practices to meet this customer commitment. In cases where these tools and policies identify certain online content as harmful and unwanted, this content is usually prevented from reaching customers. In other cases, these tools and policies may permit customers to identify certain content that is not clearly harmful or unwanted (such as bulk email or websites with questionable security ratings) and enable those customers to inspect the content further if they want to do so. To learn more about Comcast’s anti-spam and pro-network security efforts, please see What is Comcast Doing About Spam?

Other Network Security Practices

Comcast employs a number of practices to prevent unwanted communication like spam. We limit the number of login, SMTP, DNS, and DHCP transactions per second (at levels far above ‘normal’ rates) that customers can send to our servers in order to protect them from Denial of Service (DoS) attacks. (We do not disclose exact rate limits in order to maintain the effectiveness of these measures.) Please see Email - Limitations on Sending to learn more.

In order to further protect our customers, Comcast blocks a limited number of ports that are commonly used to send spam, launch malicious attacks, or steal a customer’s information. Comcast conducts several security initiatives, and offers security tools for our customers at our online security page. For more information, see List of Blocked Ports.

Attaching Devices to Our Network

Many devices are approved for use on our network. For a cable modem device to be approved for use on the network, it must pass CableLabs certification, UL certification, FCC certification, and Comcast device testing covering areas like DOCSIS performance and integration with Comcast’s network and systems.

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