Network Management Articles

Your Internet Service Performance

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At Comcast, we periodically review and revise our website to ensure that customers have the latest information about our services. We have revised our Internet service performance webpage to give customers the latest information to help them make informed choices. You can read more about the performance of our Internet service here.

Your Internet Service Performance

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Comcast provides residential customers with a variety of high-speed Internet plans from which to choose, with download speed tiers ranging from up to 5 megabits per second (" Mbps") to up to 300 Mbps (in select markets) and upload speeds ranging from up to 768 kilobits per second ("kbps") to up to 25 Mbps on our DOCSIS 3.0 and 3.1 cable networks. In select markets, we also offer a fiber-based service with symmetrical download and upload speeds up to 2 gigabits per second ("Gbps"). To see the plans currently available to you, please go to https://www.xfinity.com/learn/internet-service.

Comcast provisions its customers' modems and engineers its network with the goal of enabling customers to enjoy the speeds to which they subscribe. Comcast also provides minimum system recommendations for each of the speed tiers it offers, which can be found at https://www.xfinity.com/support/internet/requirements-to-run-xfinity-internet-service/. However, Comcast does not guarantee that a customer will achieve those speeds at all times. Comcast advertises its speeds as "up to" a specific level based on the tier of service to which a customer subscribes. As Comcast makes clear in its advertising and pricing information disclosures, "Actual speeds vary and are not guaranteed." The "actual" speed that a customer will experience while using the service depends upon a variety of conditions, many of which are beyond the control of Comcast as an Internet Service Provider ("ISP").

These conditions include:
  1. Performance of a customer's computer, including factors such as its age, processing capability, operating system, the number of applications running simultaneously, and the presence of any adware and viruses.
  2. Type of connection between a customer's computer and modem. For example, in-home wireless connections between the computer and the router or modem may be generally slower than wired connections. In-home wireless connections also may be subject to greater performance fluctuations, caused by factors like interference, attenuation, and congestion. Comcast recommends that customers confirm that their in-home wireless connections are able to support the speeds that Comcast's services deliver. Certain older in-home wireless connections and routers cannot perform at the speeds delivered by Comcast's higher speed tiers. Customers can purchase their modem and router at a retail outlet, or they can lease the necessary equipment from Comcast, though even wireless routers leased from Comcast are subject to some of the same limitations mentioned above.
  3. The distance and time it takes packets to travel between a customer's modem and their final destination on the Internet, or their point of origination and a customer's modem, including the number and quality of the networks of various operators in the transmission path. The Internet is a "network of networks." A customer's Internet traffic may traverse the networks of multiple providers before reaching its destination, and the capabilities of those networks, as well as the capacity of the facilities the edge provider (i.e., any provider of content, applications, or services over the Internet) has chosen to route its traffic to Comcast's network (and the interconnection capacity it has arranged), may affect the overall speed of an Internet connection.
  4. Congestion or high usage levels at the edge provider or destination. When you access an edge provider or particular destination that is being visited by others at the same time, you may experience a slower connection if the edge provider or destination does not have sufficient capacity to serve all of the visitors efficiently at the same time.
  5. Gating of speeds or access by the edge provider or destination. To control traffic or performance, many edge providers limit the speeds at which a visitor can download from their site. Those speed limitations will carry through to a customer's connection.
  6. The performance of the cable modem you have installed. Modem performance may degrade over time, and certain modems are not capable of handling higher speeds, such as DOCSIS 2.0 devices or early DOCSIS 3.0 devices. Comcast has a Device-to-Product Enforcement ("DPE") program to identify when customers may be using incompatible or old modem devices, whether leased or owned, and provides instructions on how to obtain new modems capable of receiving the speeds and features included with their service. Additionally, Comcast encourages its customers to promptly contact customer service if they have any concerns about their modem performance or speed capabilities. Please visit MyDeviceInfo for information regarding cable modems approved for use on Comcast's network and to determine which devices can support various speeds.

Speed

The Federal Communications Commission ("FCC") conducts an ongoing, rigorous study of the performance of the largest ISPs in the United States ("Measuring Broadband America"), including Comcast. The most recent report from this study can be found on the FCC's website. The FCC determined that Comcast's Xfinity Internet services deliver, on average, over 100 percent of their advertised downstream and upstream speeds during the busiest periods of the day, known as "peak" times, during sustained testing. Peak times are Monday through Friday from 7:00pm to 11:00pm local time.

Below are the median download and upload speeds by tier. Unless a speed tier is noted with an asterisk (*), the reported information comes from the latest FCC study. We are including the FCC's measurement of the 105 Mbps speed tier, which we no longer offer, on an interim basis until internal measurements of our 100 Mbps speed tier are completed, but we do not expect the results to differ significantly. Service tiers noted with an asterisk were not included in the FCC's study either because they are newer products with limited availability or they do not meet the study's reporting requirements. For these noted tiers, the information below is based on data compiled independently by Comcast using a largely similar testing methodology.

Download Speed Tier Measured Upload Speed Tier Measured
5* 5.95 Mbps 1 1.21 Mbps
10* 11.8 Mbps 1 1.21 Mbps
10* 11.8 Mbps 2 2.4 Mbps
25 28.90 Mbps 0.768 0.89 Mbps
50 57.56 Mbps 5 5.91 Mbps
75 85.38 Mbps 10 11.87 Mbps
105 110.81 Mbps 5 5.91 Mbps
150 151.65 Mbps 20 **
200* 212.2 10 11.5
250* 265.1 Mbps 25 29.7 Mbps
300* 318.2 Mbps 25 29.7 Mbps
*Based on independent measurements by Comcast **Not reported by Measuring Broadband America

Comcast's Xfinity Internet services also deliver over 100 percent of their advertised downstream and upstream speeds during periods of time when Internet usage is generally lighter, known as "off peak" times, during sustained testing. Below are the Comcast median speeds by tier during off peak times:

Download Speed Tier Measured Speed Upload Speed Tier Measured Speed
5* 5.95 Mpbs 1 1.21 Mpbs
10* 11.8 Mpbs 1 1.21 Mpbs
10* 11.8 Mpbs 2 2.4 Mpbs
25 29.36 Mpbs 0.768 0.90 Mpbs
50 58.59 Mpbs 5 5.93 Mpbs
75 88.61 Mpbs 10 11.89 Mpbs
105 120.05 Mpbs 5 5.93 Mpbs
150 168.29 Mpbs 20 **
200* 224.3 Mpbs 10 11.7 Mpbs
250* 292.5 Mpbs 25 29.9 Mpbs
300* 336.5 Mpbs 25 29.9 Mpbs
*Based on independent measurements by Comcast **Not reported by Measuring Broadband America

While individual experiences may vary, the FCC's tests have consistently confirmed the quality of Comcast's Xfinity Internet services.

You also can test your speeds yourself. Comcast offers its customers the ability to test the speeds that they are receiving on Comcast's network from the customer's computer to test sites located throughout Comcast's network. Simply go to http://speedtest.xfinity.com to test your connection. These tests are heavily dependent on several of the factors outlined above, especially the customer's in-home Wi-Fi network. Therefore, these tests do not necessarily reflect the performance of the Comcast network alone.

There are other speed tests that measure Internet performance. We have provided links to a few of these sites below for your reference. Please note, however, that all speed tests have limitations and flaws. Each of these tests measures limited aspects of an ISP's speed and therefore must be seen as a guide rather than definitive measurements of performance.

Latency

Latency is another measurement of Internet performance. Latency is the time delay in transmitting or receiving packets on a network. Latency is primarily a function of the distance between two points of transmission, but also can be affected by the number and quality of the network or networks used in transmission. Latency is typically measured in milliseconds, and generally has no significant impact on typical everyday Internet usage. As latency varies based on any number of factors, most importantly the distance between a customer's computer and the ultimate Internet destination, it is not possible to provide customers with a single figure that will define latency as part of a user experience. Comcast has no basis for saying what level of latency should be expected by any particular user at any particular time but notes that the measured results from Measuring Broadband America as to past performance are perhaps the closest one can come to identifying expectations of future performance as well.

Measuring Broadband America measures latency using packet tests that calculate the time it takes for packets to travel from a customer location to a target test node and back. Below are the Comcast median latency results by tier during peak times (as defined above), during sustained testing:

Speed Tier Latency
Down 5* 12.3 ms
Down 10* 16.4 ms
Down 25 20.90 ms
Down 50 25.20 ms
Down 75 18.74 ms
Down 105 23.98 ms
Down 150 19.20 ms
Down 200* 19.7 ms
Down 250* 24.3 ms
Down 300* 39.1 ms
*Based on independent measurements by Comcast

Below are the Comcast median latency results by tier during off peak times, during sustained testing:

Speed Tier Latency
Down 5* 11.7 ms
Down 10* 13.7 ms
Down 25 19.83 ms
Down 50 24.96 ms
Down 75 18.46 ms
Down 105 23.67 ms
Down 150 18.75 ms
Down 200* 20.2 ms
Down 250* 23.2 ms
Down 300* 37.3 ms
*Based on independent measurements by Comcast

These results do not define latency as part of a particular user experience because:

  1. The results include time spent traversing networks not controlled by Comcast;
  2. The geographic distance between any given user and the target node may vary greatly from those employed in Measuring Broadband America.

Customers can test the latency characteristics of their service at Xfinity Speed Test. Of course, this test also may reflect limitations in a customer's home network (especially Wi-Fi) and computers, and therefore will not necessarily reflect the performance of the Comcast network alone.

There are other latency tests available on the Internet. As previously explained, however, all tests have limitations and flaws, and therefore must be seen as a guide rather than definitive measurements of performance.

Packet Loss

Packet loss is a third measurement of Internet performance. Packet loss is the percentage of packets that are sent by the source but not received by the destination. This is sometimes due to congestion along the route but may also reflect an impairment in a customer's home network, including their Wi-Fi and coaxial cable network as well as the connection from the customer's home to the Comcast network. Customers should diagnose their home network for possible repair if packet loss is high. Packet loss is also a normal part of the Transmission Control Protocol (TCP), and signals to a sender to slow their sending rate to adjust to available bandwidth along a network path. As a result, a small amount of packet loss is expected and normal, but it is unlikely to directly affect the perceived quality of applications that request retransmission of lost packets, such as web browsing and email. In addition, measures to further reduce packet loss would require unacceptable increases in latency. However, packet loss may affect the perceived quality of applications that do not request retransmission of lost packets, such as VoIP phone calls and video chat. Nevertheless, packet losses of a few tenths of a percent are sufficiently small so that they are unlikely to significantly affect the perceived quality of these applications. The Internet's technical community continues to debate the merit and meaning of packet loss measurement. Comcast has no basis for saying what level of packet loss should be expected by any particular user at any particular time but notes that the measured results from Measuring Broadband America as to past performance are perhaps the closest one can come to identifying expectations of future performance as well.

Measuring Broadband America includes packet loss tests performed using packet tests that measure the time it takes those packets to travel from a customer location to a target test node and back. Packets not received back within three seconds of sending were treated as lost. Below are the Comcast average packet loss results by tier during peak times (as defined above), during sustained testing. Comcast currently does not have packet loss data for our 5, 10, 200, 250, and 300 Mbps services tiers. However, based on the MBA data, we expect packet loss to be in the range of 0.08% to 0.10%.

Speed Tier Packet Loss
Down 25 0.10%
Down 50 0.08%
Down 75 0.10%
Down 105 0.06%
Down 150 0.10%

Below are the Comcast average packet loss results by tier during off peak times, during sustained testing. Comcast currently does not have packet loss data for our 5, 10, 200, 250, and 300 Mbps services tiers. However, based on the MBA data, we expect packet loss to be in the range of 0.06% to 0.10%.

Speed Tier Packet Loss
Down 25 0.06%
Down 50 0.10%
Down 75 0.07%
Down 105 0.07%
Down 150 0.07%

Customers can test their packet loss by performing ping tests or other tests. As previously explained, however, all tests have limitations and flaws, and therefore must be seen as a guide rather than definitive measurements of performance. These tests are heavily dependent on several of the factors outlined above, especially the customer's in-home Wi-Fi network. Therefore, these tests do not necessarily reflect the performance of the Comcast network alone.

Xfinity WiFi

In addition to the residential or commercial Internet service that you enjoy at your home or office, Comcast provides its Internet subscribers with Xfinity WiFi, which allows Xfinity Internet subscribers to access the Internet when they are at one of the many Xfinity or Cable WiFi hotspots. Comcast engineers the underlying network to deliver high-performance access to the Internet. However, the performance you experience, once you connect to the hotspot, may vary based on any number of factors, such as the number of other subscribers trying to use the same hotspot at the same time, your computer or wireless device, your Wi-Fi receiving antenna, your distance from the hotspot router, attenuation from walls and foliage, and interference from other devices using the same spectrum, in addition to many of the factors already mentioned above. These Wi-Fi hotspots use spectrum that the FCC has allocated for "unlicensed" use, which means that our use of this spectrum is not protected from interference from other devices using the same spectrum in the same geographical area. This makes it inherently difficult to predict the kind of performance you can expect. Therefore, this service is provided solely on a "best efforts" basis.

Comcast Usage Meter Accuracy Report

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NetForecast completed a comprehensive study of Comcast's usage meter platform covering a 16-month period between January 2014 and April 2015. The report provides an overview of how our usage management platform works, methodology used to measure and validate accuracy, along with the overall performance rating. In short, NetForecast rates Comcast's usage meter accuracy as Excellent with an APDEX score of 0.94. The results of the study have been published on NetForecast's website.

Comcast Support for Mutually Agreed Norms for Routing Security

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The Internet Society (ISOC) has published Mutually Agreed Norms for Routing Security (MANRS), as a follow-up to their Routing Resilience Manifesto. Comcast joins ISOC and other network operators in calling for community action on this subject, and joining us to support this MANRS.

Primarily, adoption of the Mutually Agreed Norms for Routing Security requires that Internet Service Providers (ISPs) explicitly filter routing announcements received from their customer networks at the "prefix" level. Comcast has been employing this method for at least the past several years and expects neighboring networks to do the same.

Additionally, this calls for networks to take steps to prevent network spoofing, which is central to curtailing many amplification and/or distributed denial of service (DDoS) attacks. These attacks take advantage of the fact that some networks have not taken steps to prevent network address spoofing.

Comcast takes several steps to prevent network spoofing, and a list of FAQs on subject can be found here.

Finally, the Mutually Agreed Norms for Routing Security asks that ISPs maintain usable contact information and coordination capability for real-time troubleshooting between network operators, to which Comcast is also committed. We hope that other ISPs will adopt the guidance in the Mutually Agreed Norms for Routing Security in order that we may improve the stability and reliability of the Internet upon which we all depend.

The Routing Resilience Manifesto

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The Internet Society (ISOC) published a so-called Routing Resilience Manifesto. Comcast joins ISOC and other network operators in calling for community action on this subject, and joining us to support this Manifesto.

Primarily, adoption of the Routing Resilience Manifesto requires that Internet Service Providers (ISPs) filter routing announcements received from their customer networks explicitly at the prefix level. Comcast has been employing this method for at least the past several years and expects neighboring networks to do the same.

Additionally, the Routing Resilience Manifesto calls for networks to take steps to prevent network spoofing, which is central to curtailing many amplification and/or distributed denial of service (DDoS) attacks. These attacks take advantage of the fact that some networks have not taken steps to prevent network address spoofing. Comcast takes several steps to prevent network spoofing, and a list of FAQs on subject can be found here.

Finally, the Manifesto asks that ISPs maintain usable contact information and coordination capability for real-time troubleshooting between network operators, to which Comcast is also committed. We hope that other ISPs will adopt the guidance in the Routing Resilience Manifesto in order that we may improve the stability and reliability of the Internet upon which we all depend.

Comcast Usage Meter Accuracy Report

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NetForecast's independent assessment of Comcast's data usage meter confirms it to be accurate within +/-1% with an APDEX score of .98, which is described as excellent. The report provides an overview of how our usage management platform works, NetForecast's validation methodology, and the overall performance rating. We recently contracted with them to conduct the comprehensive study, and the results have been published on their website.

Updated Rules Regarding the Attachment of Devices to the Network

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On May 20, 2011, we first posted about these rules. Those rules have now been updated to reflect that IPv6 is now required, that DOCSIS 1.1 and 2.0 modems are now or soon will be in end-of-life status, and that we are preparing for DOCSIS 3.1 modems.

These rules pertain to the attachment of devices to our High-Speed Internet network by customers. You can find information concerning the devices approved for use on the network, and the tiers of our service that they are appropriate for at My Device Info. In order for a cable modem device to be approved for use on the network, it must pass CableLabs certification, UL certification, FCC certification, and Comcast DOCSIS certification testing. Comcast's current DOCSIS device testing requirements and the test scheduling process are described here.

Please also note that customers may purchase their own cable modem for use on the Comcast network. However, Comcast does not support all possible modems on its network because there may be compatibility issues with some devices. The Comcast Agreement for Residential Services (Sections 6(b)(1)-(3)) makes clear that a device must meet Comcast's minimum technical specifications in order to successfully install, access, operate or use a particular service. In addition to our full list of approved devices, a list of recommended retail devices can be found at My New Modem.

FAQs on Preventing Network Spoofing

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Background

Computers and other devices connected to the Internet use IP (Internet Protocol) addresses to establish end-to-end communications. Most devices use a single IP address, though some have several. Successful communication relies on both the source and destination addresses being encoded in packets sent between the systems to enable two-way interactions. Thus, your packet has the destination address, as well as the return (source) address, much like a letter.

Problems

Many network attacks make use of the ability to "spoof" or "forge" the source IP address in a packet. By using this forged source address, it can make it difficult or impossible to trace the source of an attack. In addition, this can be used to take down networks in large-scale Distributed Denial of Service (DDoS) attacks where many computers are told to send a response to the forged source address.

Unfortunately, the Internet's architecture does not prohibit source address spoofing by default; network operators are relied upon to do so.

Solutions

Since each device on the Internet should be assigned a given IP address, rules and configuration settings on the source network must be used to ensure that that device cannot send packets with a source address that was not assigned to it. Proper configuration and policy that effectively block IP spoofing go a long way to cutting down on the avenues available for abuse and attack on the network. This recommendation has been enshrined by the Internet engineering community as Best Current Practice #38, or BCP38 for short, and published by the IETF (Internet Engineering Task Force) in its Request For Comments (RFC) document series as RFC2827.

Comcast's Efforts to Prevent IP Address Spoofing

Comcast implements "source address filtering" or "source address validation" as a basic technique to prevent IP address filtering. As a result, we implement BCP38/RFC2827 in our network.

To do this in our subscriber network we use one of two techniques: a technique known as Unicast Reverse Path Forwarding (uRPF) verification, and implementation of DOCSIS Source Address Verification (SAV). Using these techniques our customers are prevented from sending traffic with spoofed IP addresses through their cable modems. uRPF is described in RFC3704 and SAV is described in Section 9.6 of the DOCSIS 3.0 standard's security specifications. Using these methods, customers are prevented from sending traffic with spoofed IP addresses through their cable modems.

Although Comcast does its best to prevent IP address spoofing, there are situations where applying uRPF checking is not feasible or practical. This includes services for some commercial customers that have multiple Internet service providers, known as multi-homing. In cases such as these, Comcast can and does provide guidance to such customers so that they can effectively implement uRPF or similar checking within their own networks. BCP84/RFC3704, elaborates further on these cases.

The Internet Community

Implementation of techniques to prevent IP address spoofing can be thought of as an "environmental benefit" for the Internet.

When implemented by Comcast or another network operator, these measures don't only or even primarily benefit that operator's customers. Rather, they benefit the broader community by plugging security holes in the Internet, and preventing more widespread DDoS attacks that leverage spoofing. The broader the uptake of these techniques, the greater the improvement overall and the safer we all become on the Internet.

The FCC Communications Security, Reliability, and Interoperability working group is also working to improve this in the U.S. The FCC's CSRIC has studied this issue in the past and continues to do so.

Since Comcast prevents IP address spoofing and supports BCP38, what benefits does this have for the rest of the Internet?

Our techniques help limit malicious traffic that could otherwise come from Xfinity Internet customers, destined to or targeted at other Internet networks or servers. As a result, any attack launched from a Comcast subscriber will have the true IP address of the subscriber's cable modem and as such can be rapidly traced back and mitigated. As such it is not possible to use a Comcast residential Internet customer as an originating source for distributed denial of service (DDoS) attacks that use IP address spoofing to conceal the addresses of computers used in those attacks, such as a recent DNS amplification attack against an anti-spam organization or a recent NTP amplification attack against a content delivery network (CDN).

Preventing Network Spoofing

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Recently, the Internet community has taken notice of NTP amplification attacks, as well as other attacks leveraging DNS, SNMP, and other protocols. These attacks take advantage of the fact that some networks have not taken steps to prevent network address spoofing. Since we have been asked what steps Comcast takes to prevent network spoofing, we have put together an FAQ on the subject.

In short, we use one of two techniques: Unicast Reverse Path Forwarding (uRPF) verification and DOCSIS Source Address Verification (SAV). Using these techniques our customers are prevented from sending traffic with spoofed IP addresses through their cable modems.

FAQs on preventing network spoofing.

Revision of Comcast's SNMP and SMTP Policies

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We've announced some changes our policies on Simple Network Management Protocol (SNMP) and Simple Mail Transport Protocol (SMTP), which will affect a very small portion of our customers. You can find more information in two blog posts. One is a general post about both issues, and the other is specific to SMTP. While the policy change was announced today, implementation will occur gradually.

Comcast to Replace Usage Cap With Improved Data Usage Management Approaches

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We've announced some important changes - there's more information on our blog and our FAQs for more information. We will be revising our Acceptable Use Policies in the near future.

Performance Info

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Your Internet 2go Service Performance

Comcast provides the Internet 2go service (the "Service") using state-of-the-art networks that are operated and managed by third parties that Comcast works with to provide access to the Service and to deliver the best possible mobile Internet experience to all customers. In light of the particular technical and operational circumstances regarding mobile wireless networks, however, no mobile wireless Internet Service Provider ("ISP") can guarantee a particular speed at all times to a customer. The "actual" speed that a customer will experience while using the Service depends upon a variety of conditions and factors, many of which are beyond Comcast's control. These conditions include:

  1. Performance of a customer's computer, including its age, processing capability, operating system, the number of applications running simultaneously, and the presence of any adware and viruses.
  2. Coverage and network signal quality, which can be affected by any number of factors outside the control of the network operator. For example, factors such as terrain and foliage, weather conditions, the presence and composition of buildings and other man-made objects, and the number of users simultaneously trying to connect to the network all can affect the performance that customers may experience at any moment in time.
  3. The distance packets travel (round trip time of packets) between a customer's computer and their final destination on the Internet, including the number and quality of the networks of various operators in the transmission path. The Internet is a "network of networks." A customer's Internet traffic may traverse the networks of multiple providers before reaching its destination, and the limitations of those networks will most likely affect the overall speed of that Internet connection.
  4. Congestion or high usage levels at the website or destination. When you access a site or particular destination that is being visited by others at the same time, you may experience a slower connection if the site or destination does not have sufficient capacity to serve all of the visitors efficiently at the same time.
  5. Gating of speeds or access by the website or destination. To control traffic or performance, many websites limit the speeds at which a visitor can download from their site. Those limitations will carry through to a customer's connection.
  6. The performance of the mobile broadband device you are using. Comcast provides you with the mobile broadband device to use with the service, but, like all electronic devices, this device is susceptible to degradation over time caused by any number of factors outside of Comcast's control. If the device is not working at its optimal levels, you may not experience the highest-quality performance.

Specific Speed and Latency Information

Service speed is one of the means by which customers and providers alike measure the performance of a broadband Internet connection. As discussed above, however, any number of factors can affect the speed of the service. Because third-party providers, not Comcast, operate and manage the Internet 2go networks, Comcast does not presently have accurate and reliable speed test data for the Internet 2go service. Comcast will update this section and post the speed test data from the third parties that operate and manage the Internet 2go network when that data becomes available to Comcast. However, you can test your speeds yourself. Comcast offers its customers the ability to test the speeds that they are receiving on Comcast's network - from the customer's computer to test sites located throughout Comcast's network. Simply go to http://speedtest.comcast.net to test your connection. These tests are heavily dependent on many of the factors outlined above, however, and therefore do not necessarily reflect the performance of the Internet 2go networks.

There are other speed tests that measure Internet performance. We have provided links to a few of these sites below for your reference. Please note, however, that all speed tests have biases and flaws. Each of these tests measures limited aspects of an ISP's speed and therefore must be seen as a guide rather than definitive measurements of performance.

Latency is another measurement of Internet performance. Latency is the time delay in transmitting or receiving packets on a network. Latency is primarily a function of the distance between two points of transmission, but also can be affected by the number and quality of the network or networks used in transmission. Latency is typically measured in milliseconds, and generally has no significant impact on typical everyday Internet usage such as reading an email, viewing a webpage, or downloading photos. As latency varies based on any number of factors, most importantly the distance between a customer's computer and the ultimate Internet destination, it is not possible to provide customers with a single figure that will define latency as part of a user experience. Because third-party providers, not Comcast, operate and manage the Internet 2go networks, Comcast does not presently have accurate and reliable latency data for the Internet 2go service. Comcast will update this section and post the latency data from the third parties that operate and manage the Internet 2go network when that data becomes available to Comcast.

When You're Roaming

From time to time, when you are outside the Internet 2go coverage area or otherwise unable to get a signal from the Service, you may be able to "roam" on another provider's network. Regardless of whether you are roaming or using the Comcast Internet 2go networks, many of the above-mentioned factors will affect the performance of the service. However, when you are roaming, Comcast has no control over the level of performance of the service you are receiving.

Network Management Trial

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The company announced in March 2008 that it will switch to a new network management technique by the end of the year for managing bandwidth use and congestion. This new technique does not look at particular protocols or applications. Instead, it will focus on the bandwidth consumption activity of individual customers who are contributing to congestion on Comcast's network. The technique measures only aggregate bandwidth consumption, not the protocol or content being used by customers.

The first step for using this new network management technique is to run a trial of the technology in a market of Comcast High-Speed Internet customers. The trial will allow Comcast to better understand how this technique works in a "real world" setting. It will also let the company try different settings and learn from trial results in order to fine tune this new technique so Comcast can deliver the best online experience possible for all of its customers.

Comcast is currently running trials of this network management technique in the areas of Chambersburg, PA, Warrenton, VA. We recently announced an expansion of our Network Management trial to Lake City, FL and East Orange, FL and Colorado Springs, CO.

How Does The New Network Management Technique Work?

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The new network management technique is designed to ensure, to the greatest extent possible, that all Comcast High-Speed Internet customers have fair and equal access to the Internet and to bandwidth resources. Without it, some customers would experience poor performance - for example, slow access to e-mail, sluggish web surfing, or low quality streaming audio and video - during periods of network congestion.

Most customers will notice little to no change in their Internet experience when the new network management technique is working to help deliver a consistent, excellent online experience. The new network management technique will result in delayed response times for Internet traffic only for those customers who are using more than their fair share of available Internet resources at the time. The network management technique manages those customers' Internet traffic until their usage falls below established bandwidth usage thresholds or until network congestion ends.

During this trial, Comcast will learn more about how this network management technique will affect customers. Comcast expects that network management will only affect a small percentage of users during periods of network congestion, while ensuring an excellent online experience for the vast majority of our users.

We will provide periodic updates on this webpage on our trials and our progress in transitioning to this new network management technique.

Network Management Update

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Comcast manages its network to ensure all of its customers have a great online experience every time they use our high-speed Internet services. The Internet is changing all of our lives and we want our customers to enjoy all that it has to offer - from up-to-date news and information, online shopping, communications tools, movies, streaming video, music, gaming and an array of online services that help us organize our digital assets. For more than a decade, Comcast has been at the forefront of bringing the Internet into millions of people's homes and has invested in a high-capacity fiber-optic network that is fast, safe, reliable and affordable.

Like any other Internet service provider, we manage our network for many reasons including growing, upgrading and optimizing the network; removing spam, viruses and malicious content; and managing network traffic congestion when it occurs. While congestion is not the normal state of any network, when it happens, just like being stuck in a traffic jam on the highway, it can be frustrating. So, Comcast actively manages congestion to minimize the impact of temporary broadband traffic jams.

Our new congestion management technique will only ever impact a tiny fraction of our customers who consume extraordinary amounts of bandwidth. Over the past several months, our real world consumer trials have shown that on average less than 1% of our customers would likely be impacted by this congestion management technique. Instead, the new technique actually helps ensure that all customers get their fair share of bandwidth.

What is the purpose of this new technique?

Comcast's broadband network, like many networks, is shared. Our customers share upstream and downstream bandwidth with their neighbors. Although the available bandwidth is substantial, so, too, is the demand. Thus, when a relatively small number of customers in a neighborhood place disproportionate demands on network bandwidth, they can heavily contribute to congestion that degrades their neighbors' Internet experience. The goal of Comcast's new congestion management practices will be to enable all users of network resources to access a fair share of that bandwidth and helps ensure a high-quality online experience for all of Comcast's broadband customers.

How will the new technique work?

The new congestion management practice works as follows:

If a certain area of the network nears a state of congestion, then it will identify which customer accounts, or modems, are using the greatest amounts of bandwidth, and the Internet traffic of these customer accounts will be temporarily managed. Customers will still be able to do anything they want to online, and many activities will be unaffected, but, in the event the network reaches levels of actual congestion, managed customers could experience longer times to download or upload files, surfing the Web may seem somewhat slower, and playing games online may seem somewhat sluggish. We manage those customer accounts that are using a disproportionate amount of network resources in order to maintain the online experience of all users on the network. This prevents the unusually high usage of a few customers to adversely affect the experience for others.

The new technique does not manage congestion based on the online activities, protocols or applications a customer uses. Rather it only focuses on the heaviest users in real time, so the periods of congestion could be very fleeting and sporadic.

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

The new technique could be referred to as "protocol-agnostic," which means it does not manage congestion based on the type of applications being used by customers. Instead, customer traffic is congestion-managed and is not based on their applications, but based on current network conditions and recent bytes transferred by users.

Our congestion management approach will change over time, as we continue to study and enhance our practices and as new technologies emerge. In the meantime, we will continue to invest in our network in accordance with our normal course of business operations, which includes splitting nodes to increase capacity and rolling out DOCSIS 3.0 technology that will increase the speed and capacity of our services. At the same time, we will continue to actively participate in industry-wide technical forums such as the Internet Engineering Task Force (IETF), where congestion management and other matters are under continuous review, development, and improvement.

Network Management Update

Published:

Today, Comcast provided additional information to the FCC about how we manage congestion on our network, including detailed information about the future congestion management techniques we announced in March. More information and copies of these filings are posted here.

At the outset, it's important to underscore that Comcast manages its network to ensure that all of its customers have a great online experience. The Internet is changing all of our lives and we want our customers to enjoy all that it has to offer - from up-to-date news and information, online shopping, communications tools, movies, streaming video, music, gaming and an array of online services that help us organize our digital assets. For more than a decade, Comcast has been at the forefront of bringing the Internet into millions of people's homes and has invested in a high-capacity fiber-optic network that is fast, safe, reliable and affordable.

Like any other Internet service provider, we manage our network for many reasons including growing, upgrading and optimizing the network; removing spam, viruses and malicious content; and managing network traffic congestion when it occurs. While congestion is not the normal state of any network, when it happens, just like being stuck in a traffic jam on the highway, it can be frustrating. So, Comcast actively manages congestion to minimize the impact of temporary broadband traffic jams.

As announced in March 2008, Comcast is transitioning to a new congestion management technique by the end of the year. While our new technique doesn't share anything in common with our old one, they do share one important aspect - very few customers will ever be impacted. Our real world consumer trials have shown that on average less than 1% of our customers will experience anything different. In fact, the new technique will actually help ensure that all customers get their fair share of bandwidth.

Included on this Web page are a number of helpful links and documents that you may find of interest:

  • A PDF document that describes this new technique in detail and was filed with the FCC on 9/19/08.
What have we been doing to prepare for this transition?

Before we describe the new technique in more detail, it's important to recap what we have been working on over the past several months. In March 2008, we announced that we would be migrating to a new network management technique for congestion before the end of the year. To get there, we also announced that we would be conducting a series of trials over the summer of different vendor equipment and techniques in Warrenton, VA, Chambersburg, PA, Colorado Springs, CO, Lake View, FL and East Orange, FL. During these trials, Comcast did not receive a single customer complaint that could be traced to this new congestion management practice, despite having publicized the trials and notifying customers involved in the trials via e-mail.

Who will be affected?

Based on consumer data collected from these trials, we found that on average less than 1% of our high-speed Internet customers are affected by this congestion management technique.

What is the purpose of this new network management technique?

Comcast's High-Speed Internet network is a shared network, which means that our customers share upstream and downstream bandwidth with their neighbors. Although the available bandwidth is substantial, so, too, is the demand. Thus, when a relatively small number of customers in a neighborhood place disproportionate demands on network bandwidth, they can heavily contribute to congestion that degrades their neighbors' Internet experience. The goal of Comcast's new congestion management practices will be to enable all users of network resources to access a fair share of that bandwidth, in the interest of ensuring a high-quality online experience for all of Comcast's broadband customers.

How will the new technique work?

The new network management practice works as follows:

If a certain area of the network nears a state of congestion, the technique will ensure that all customers have a fair share of access to the network. It will identify which customer accounts are using the greatest amounts of bandwidth and their Internet traffic will be temporarily managed until the period of congestion passes. Customers will still be able to do anything they want to online, and many activities will be unaffected, but managed customers could experience things like: longer times to download or upload files, surfing the Web may seem somewhat slower, or playing games online may seem somewhat sluggish.

The new technique does not manage congestion based on the online activities, protocols or applications a customer uses, rather it only focuses on the heaviest users in real time, so the periods of congestion could be very fleeting and sporadic.

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

Will the technique target P2P or other applications, or make decisions about the content of my traffic?

No, the new technique is "protocol-agnostic," which means that the system does not manage congestion based on the applications being used by customers. It is content neutral, so it does not depend on the type of content that is generating traffic congestion. Said another way, customer traffic is congestion-managed not based on their applications, but based on current network conditions and recent bytes transferred by users.

How will we communicate this change to our customers?

We will be proactively communicating the implementation of this new technique through direct customer contacts and updated consumer disclosures.

  • Our Acceptable Use Policy will be updated.
  • We will post new FAQs to our customer help sections.
  • We will send email notifications to our customers.
  • We will periodically update this Web page with additional information.
What's next?

Our congestion management approach will change over time, as we continue to study and enhance our practices and as new technologies emerge. In the meantime, we will continue to invest in our network in accordance with our normal course of business operations, which includes splitting nodes to increase capacity and rolling out DOCSIS 3.0 technology that will increase the speed and capacity of our services. At the same time, we will continue to actively participate in industry-wide technical forums such as the Internet Engineering Task Force (IETF), where congestion management and other matters are under continuous review, development, and improvement.

DNSSEC Deployment Completed, Domain Helper Deactivated

Published:

As noted here on our blog, we have signed all of our domain names and all customers are now using DNSSEC-validating resolvers. Comcast is the first large ISP in the North America to have fully implemented DNSSEC, as part of ongoing efforts to protect our customers with Constant Guard™ from Xfinity. In addition, Comcast Domain Helper has been turned off, as we noted here.

IPv6 Pilot Market Deployment Begins

Published:

Comcast has started our first pilot market deployment of IPv6. This first phase supports directly connected CPE, where a single computer is directly connected to a cable device. A subsequent phase will support home gateway devices. To learn more, check out the announcement and technical details on our blog.

Rules Regarding the Attachment of Devices to the Network

Published:

Does Comcast have rules regarding the attachment of devices to our High-Speed Internet network by customers?

Yes, and you can find information concerning the devices approved for use on the network, and the tiers of our service that they are appropriate for at https://mydeviceinfo.xfinity.com/. In order for a cable modem device to be approved for use on the network, it must pass CableLabs certification, UL certification, FCC certification, and Comcast DOCSIS certification testing. Comcast's current DOCSIS device testing requirements and the test scheduling process are described here.

Your Internet Service Speeds

Published:

Comcast provides residential and commercial customers with a variety of high speed Internet plans from which to choose, ranging from our Economy tier (with download speeds up to 1.5 megabits per second (" Mbps"), and upload speeds up to 384 kilobits per second ("kbps")) to our Extreme 105 tier (with download speeds up to 105 Mbps, and upload speeds to 10 Mbps). Comcast provisions its customers' modems and engineers its network to ensure that its customers can enjoy the speeds to which they subscribe. However, Comcast does not guarantee that a customer will actually achieve those speeds at all times. Without purchasing an expensive, dedicated Internet connection, no Internet service provider ("ISP") can guarantee a particular speed at all times to a customer. Comcast advertises its speeds as "up to" a specific level based on the tier of service to which a customer subscribes.

Read much more about this topic here.

Updated Network Management FAQs

Published:

Comcast created this site in 2008 to transparently disclose our network management practices, and we have updated it with relevant information since its inception. Today, we have updated our network management FAQs to describe and explain our current network management practices for our high-speed Internet services.

DNSSEC Rollout Begins

Published:

As noted on our blog, starting today we will begin migrating customers who have opted out of our Domain Helper service over to our production DNSSEC-validating servers. This will happen first in a selected part of our Virginia network, and will later expand to all markets in the following sixty days, at which point all of our customers who have opted out of Domain Helper will be migrated. After this has been completed, we will migrate the rest of our customers, which we anticipate will stretch into the early part of 2011. You may also want to check out our Constant Guard™ page.

Constant Guard™ Bot Detection and Notification National Rollout Begins

Published:

In October 2009, we announced the market trial of our new Constant Guard™ bot detection and notification system. The system was designed to detect bot activity and send customers a "Service Notice" when we believe their computer has been infected with a bot or other malware. Based on the success of the market trial, we have decided to rollout the bot detection and notification system to our entire network over the next few months. For additional information, feel free to visit our blog post or our Constant Guard™ page.

DNSSEC Update .ORG TLD Signed, All Comcast .ORG Domains Signed

Published:

Today in Brussels, the Public Interest Registry, operator of the .ORG Top Level Domain (TLD), announced that they have signed the .ORG TLD, enabling support for DNSSEC in that TLD. Coinciding with that announcement and joint testing we have performed with PIR, Comcast is pleased to sign all of our over 650 .ORG domains. This is an important milestone in our continuing work to deploy DNSSEC. You can find slides we will be presenting at two ICANN DNSSEC workshops tomorrow here and here.

Broadband Internet Technical Advisory Group Announced

Published:

Comcast, along with other leading high-tech companies, announced the formation of the Broadband Internet Technical Advisory Group, or 'BITAG' for short. The BITAG will focus on network management issues, among other topics. For more information, please see a post on our blog here.

DNSSEC Implementation Plans Announced

Published:

Comcast has been a leader in the testing of and advocation for the wide adoption of DNSSEC. Our leadership continues today with the announcement of a plan to implement DNSSEC validation in the DNS servers that our customers use by the end of 2011, as well as for signing of our authoritative domains, such as comcast.com, by the end of the first quarter of 2011. In addition, today we are making available DNSSEC-validating DNS servers for customers to use on a trial basis now.

IPv6 Technical Trials for 2010 Announced

Published:

Comcast has been a leader in IPv6 development for many years. Our leadership continues today with the announcement of a plan to conduct real, production-network trials of IPv6 technology this year. The transition from IPv4 addresses to IPv6 addresses is a necessity, as the available pool of IPv4 addresses will at some point be exhausted for all Internet users.

These trials will help Comcast to identify and solve any areas of difficulty involved in the transition to IPv6, and to determine what approach will be the easiest and most seamless to our customers. Comcast will continue to share what we learn with the Internet community, particularly with the IETF, for the benefit of other users of the Internet.

Customers who are interested in volunteering to participate in these IPv6 trials, can express their interest using the online form on the Comcast IPv6 Information Center website.

Data Usage Meter Pilot Market Deployment

Published:

Today we announced the start of a pilot market deployment of our data usage meter for our High-Speed Internet Service. This deployment begins today for customers in Portland, Oregon. We currently anticipate deploying this usage meter beyond the pilot market beginning in the first quarter of 2010. You can find FAQs here, and an independent analysis of the usage meter by NetForecast, Inc. here. Feel free to visit our customer support forums if you'd like to ask us more questions.

Comcast Participates in MIT Internet Traffic Analysis Study

Published:

The MIT Internet Traffic Analysis Study (MITAS) is a new research project at the MIT Computer Science and Artificial Intelligence laboratory (CSAIL). The goal of this project is to undertake novel empirical research of ISP traffic data. Data will be collected from at least six participating ISPs, including Comcast, and the project hopes to add more ISPs. Better data and collection methodologies are needed to inform the industry, the network research community, and policy discussions about appropriate technical and business approaches to traffic management.

Detailed traffic data will be collected from ISPs over time, enabling researchers to formulate empirically valid characterizations of both aggregate traffic patterns, as well as a traffic profile for the average users. It is important to note that no personally identifiable information about any participating ISPs' users will be used in this project.

Service Notice Trial Begins

Published:

Today we announced our new Constant Guard™ security program. We are also testing a feature of Constant Guard™ called a "Service Notice," designed to send customers a message when we believe their computer has been infected with a virus or other malware.

Prior to the start of this trial, we developed the a draft document with the Internet Engineering Task Force (IETF) regarding remediation of malicious bots, available for review and comment by the Internet community at http://tools.ietf.org/html/draft-oreirdan-mody-bot-remediation. In addition, for the same purposes, we have developed a draft document with the IETF which describes in detail how the Service Notice system works, available at https://datatracker.ietf.org/doc/draft-livingood-web-notification/.

Domain Helper National Rollout Begins

Published:

In July 2009, we announced our market trial of our new Domain Helper service, designed to help customers find Web sites they want when they mistype an address in the web browser's address bar. Based on the success of the market trial, we have decided to roll out the service to our entire network. Customers will receive an email explaining the service and how to opt-out shortly, but can certainly opt-out now as well. Please note that customers with statically-configured Comcast DNS servers are opted-out by default.

To find out how Domain Helper works, please click here.

Domain Helper Disclosure

Published:

Comcast is committed to transparency in our network practices. We have shared details and answered questions about our launch of the Domain Helper service, both in our blog, in popular web forums and in other documents. We have also worked to ensure that customers are aware of how they can quickly and easily opt-out if they so desire.

How Does Domain Helper Work?

Domain Helper works by redirecting a web user to a search portal when the user enters a non-existent domain name into the browser bar. In order to receive a redirect, the non-existent domain name must match the following pattern: www.SOME-INVALID-NAME.com

  • The entry must include "www" followed by a dot ("www.")
  • The entry must have a dot followed by a valid Top Level Domain ("TLD"), such as .com, .net, .org, or any other valid TLD
  • The name typed between "www." and ".com/net/org" must not exist among registered domain names

We will eventually phase in the following pattern matches to enhance this service in the future:

  • www.SOME-INVALID-NAME.cmm or www.SOME-INVALID-NAME
  • The entry must include "www" followed by a dot ("www.")
  • The entry must have an invalid TLD, such as .cmm, .ner, .orf, etc. (the first example), or it must have no TLD (the second example)
  • The name typed between "www." and the second dot (".") may or may not exist among registered domain names - in this case, the TLD is either invalid or missing.

Domain Helper Market Tests Begin

Published:

At Comcast, we are constantly looking to deliver a better high-speed Internet and online search experience. That is why we have begun market testing Domain Helper in selected areas to help customers find the Web sites they want when they mistype a Web address name in a Web browser's address bar. Those market areas are: Arizona, Colorado, New Mexico, Oregon, Texas, Utah, and Washington.

Some customers will not want the assistance of Domain Helper, so there is an easy way to opt-out of this when you receive the suggestion Web page (or by visiting the opt-out page now - note also that customers with statically-configured Comcast DNS servers are opted-out by default). We have also developed the first draft of a new best practices document with the IETF regarding these types of services, available for Internet community review and comment at http://tools.ietf.org/html/draft-livingood-dns-redirect-00.

We hope our customers find this to be a valuable tool.

Network Management Update

Published:

In March 2008, we announced that by the end of the year Comcast would switch to a new network management technique for managing congestion on Comcast's broadband network. Effective December 31, 2008, we have completed this transition, which is now part of our daily business operations for managing congestion on our network. The approach is designed to ensure, to the greatest extent possible, that all of our high-speed Internet customers have fair and equal access to the Internet and to bandwidth resources.

On these Web pages, we have provided information and FAQs about congestion management and we have posted copies of the documents we filed with the FCC that also describe it in great detail.

Read more about network management

Additional FAQs Posted on Security-Related Port Blocks

Published:

As part of continuing efforts to increase our transparency on our network management methods, we have updated and expanded our FAQs. We have recently published a new FAQ regarding the network ports which are blocked for security reasons, in order to protect our customers. It is available at here in our FAQs.

Network Management Update

Published:

Comcast is pleased to announce that we have successfully completed the trial of our new network management technique. We are now following through on our commitment to implement this new technique for managing network congestion across all areas of the country by the end of this year.

We will gradually transition to the new technique over the next few months and will conclude no later than December 31, 2008. The new technique is currently being used in the following areas: Minnesota, Indianapolis and Muncie, IN, Paducah, KY.

More questions? View our Network Management FAQs

IETF 73

Published:

IETF 73 will include P2P and network management-related topics, as a follow-up to the 72nd IETF meeting in July, 2008. The 73rd IETF meeting will take place in Minneapolis in November. We anticipate participating in a variety of working groups relevant to this topic, including Techniques for Advanced Networking Applications (TANA) and Application-Layer Traffic Optimization (ALTO) Birds of a Feather (BoF) meetings. In preparation for the ALTO BoF, where P4P-like mechanisms are being discussed, we have submitted in Internet Draft describing our recent P4P technical trial results, which is available here.

Network Management Update

Published:

Today, Comcast provided additional information to the FCC about how we manage congestion on our network, including detailed information about the future congestion management techniques we announced in March. More information and copies of these filings are posted here.

View full article.

Network Management Trial Expansion

Published:

We are expanding our previously announced network management trial to the areas of Colorado Springs, CO, East Orange, FL, and Lake City, FL. We expect to continue these trials for at least 30 days as we evolve the new protocol-agnostic network management technique.

These trials which started in March 2008 are ongoing in the previously-announced markets of Warrenton, VA, and Chambersburg, PA

View full article.

IETF 72

Published:

IETF 72 will include P2P and network management-related topics, as a follow-up to the IETF P2PI Workshop in May. The 72nd IETF meeting will take place next week in Dublin, Ireland. While some of this follow-up work will occur in regular IETF workgroup groups, most of it will take place in the Techniques for Advanced Networking Applications (TANA) and Application-Layer Traffic Optimization (ALTO) Birds of a Feather (BoF) meetings. Comcast is participating in IETF 72.

Network Management Trial Update

Published:

The company announced in March 2008 that it will switch to a new network management technique by the end of the year for managing bandwidth use and congestion. The new network management technique is designed to ensure, to the greatest extent possible, that all Comcast High-Speed Internet customers have fair and equal access to the Internet and to bandwidth resources.

View full article on the trial, or see details of how the technique works.