Online Journal Club for Networking Researchers

Posts Tagged ‘home broadband’

Independent Measurement of Broadband Provisioning Quality by SamKnows: A Step Towards Providers’ Accountability?

Posted by David Mayer on January 2, 2009

Some time ago on this blog we wrote about the lack of accountability in home broadband provisioning. We noted how difficult it is for a typical broadband customer to give evidence about poor service. One of the solutions to generate legally sound evidence we mentioned was to deploy hardware monitors attached to customer modems. This is exactly what SamKnows Limited have done, although the reasons behind their project are probably different. The project was partly backed up by Ofcom.

A report describing the project has been published by Sam Crawford here.  In this article, we briefly characterise the measurement scheme, pick out some interesting results and finally comment whether this scheme could be used to gather evidence about quality of broadband provisioning for individual users.

One of the objectives of Sam’s report is to enlighten the public about the myth that speed is by far the most important property of a broadband service. The results show that speed is only one of many properties which affect the quality of the service and that other properties can have larger effect on the quality as perceived by the user.

We at PaperPicker look at this project as an example of how Internet providers could be made accountable. A typical user can never find out, leave alone quantify, what is wrong with their connection. An ISP can always blame user’s equipment for the fault and it is extremely difficult for users to show evidence of poor service. A measurement scheme such as this is a real-world example of generating statistically and legally sound evidence.

What was done and how

At the heart of the scheme lie hardware monitoring units, installed at homes of volunteers and equipped with measurement routines. The monitoring units were deployed all over UK with the help of Ofcom. Over the course of 6 weeks in 2008 these units were generating multiple types of traffic, recording measurements and sending the results to SamKnows servers. The test included 223 devices and covered 12 UK-based Internet service providers (ISP).

What makes this project unique is the fact that the collected measurements are both independent of ISPs and statistically sound. The measurements are independent of ISPs because they do not require any cooperation from ISPs. Statistical confidence comes from the number of units deployed and the number of measurements carried out.

However, since SamKnows do not quite disclose the reasons for doing this project nor they specify how it is financed, one can have doubts over the independence. On the other hand, the project is backed up by Ofcom, the UK telecom regulator.

So how does it work?

A monitoring unit (Linksys WRT54GL with embedded Linux) is connected between user’s modem or router and user’s computers as shown in the figure below. The unit generates traffic only when the user’s equipment does not. A pre-programmed set of tests runs according to a given schedule and results are collected at SamKnows servers.




Metrics and results

Sam’s report presents and analyses a number of different measurements, but we will comment on a few selected ones in the following table.

Metric Result Comment
Latency Provider-average of about 40ms. did particular badly; at peak hours latency goes up by 180% compared to quiet hours, while the cross-provider average increases in peak hours by only 25%.
Loss Very small across providers (under 0.6%).  –
Response time of DNS queries Very good across providers (average of 46ms) with the exception of Be Unlimited which occasionally exceeded 4-times the average response time. The report shows how DNS query times affect web browsing even when latency is low.
DNS failures Very low with a failure rate average of 0.81%, apart from Be Unlimited at 2.82%. – 
Perception quality of VoIP Most providers achieved a score close to the theoretical maximum, with the exception of Virgin Media, despite its very small latency. Measurements show how jitter (the variance of delay) lowers the perception quality of VoIP. Virgin Media has excellent latency results but suffers low VoIP quality due to high jitter.
Speed as a percentage of implied line speed Most providers achieve 75%, but from a more detailed graph we see that both ADSL and Cable Virgin drop significantly in speed during peak hours. Implied line speed is defined as the maximum throughput achieved across all speed tests within a two day period.


Another interesting finding is the evidence of ISP performing traffic shaping for traffic at ports other than 80. This is because ISPs are trying to cap peer-to-peer protocols traffic and those use non-80 ports.
A small objection against the time averaging of results: Take the 75% line speed result. As such it may not reflect user’s satisfaction very well. For example, if for most of the day the speed is high but most users are not using the connection (they are not at home), and then evening brings a significant drop when many users are at home, the result may be 75% just because the speed ishigh for large part of the day.

So for example exhibits a 50% drop in implied line speed at peak hours. For a user who connects only in the evening (after work), this 50% drop would certainly translate into a larger drop in satisfaction than the three quarters suggested by the 75% time-averaged drop.

Would this scheme suffice to provide evidence of poor quality?

Although this measurement scheme was probably not developed with the aim of gathering evidence against ISPs, one could imagine it could be used in such way. Of course, only large-scale metrics could be reported, such as averages across large number of locations, metrics of commoly accessed DNS servers and such. A more granular evidence would require several monitoring devices per location (e.g., a street) and this might be financially unfeasible. Another issue would be the fact that the monitoring devices measure only when users are idle, while many faults occur when many users are using the service. And so while this is the first independent and statistically solid measurement scheme there is, its use as a monitor of quality for geographically clustered or individual users is limited.

The report certainly fulfills its premise by showing that connection speed has only a limited effect on user’s perception of quality and that the Internet experience is affected by many other factors which providers are in control of. Could this report serve as a hint to regulators that ISPs should enrich their contracts by other properties than mere speed?

Posted in accountability, congestion, Of Interest, QoS | Tagged: , , , | 8 Comments »

The Role of Accountability in Home Broadband Provisioning

Posted by David Mayer on August 31, 2008

As of July 2008, some 20 years after the first Internet Service Providers (ISP) were formed and some 50 years after packet switching was invented, the home broadband customer still has no guarantee of any quality parameter, no way of holding his ISP accountable for interruptions and low speed, no choice of quality and no way to fairly share resources with other customers in times of congestion.

Any home broadband customer will be familiar with the situation when something is wrong with their connection, be it unavailability, high data loss or failed name servers. Yet upon contacting the provider one is taken through a bemusing routine of resetting their PC, router, modem, and whatever else has buttons to press, the ISP rarely saying: “It is our fault, we’ll refund you.”

What exactly determines the quality of a broadband connection? All performance characteristics will depend on

  • Network dimensioning and management
  • Behaviour of other customers
  • Resource sharing mechanism in place
  • The rest of the Internet.

While the rest of the Internet is not in the operator’s powers and the behaviour of the users only partly, the network dimensioning and resource sharing facilitation certainly are. Let us now briefly describe what these issues encompass and how today’s operators implement them.

(The lack of) Resource sharing mechanisms

Resource sharing is a mechanism determining the division of network resources between the operator’s customers, especially in times of high demand and congestion. Certain resource sharing is facilitated by medium access protocols. For example, the DOCSIS protocol used in cable networks has extensive means of controlling the total usage of resources of every user at any time. Also the transport layer offers some resource sharing mechanism; TCP controls the rate of every connection but not the total rate of a user. Besides, it cares about resources along the end-to-end path rather than the resources in the operator’s network only.
The medium access protocols and even transport layer protocols are fully controllable by the operator who could use them to facilitate resource sharing.

So how do some of UK’s major broadband providers deal with fair sharing? Virgin Media cable broadband penalizes rough customers after they have committed a high-usage activity. The ISP will reduce the speed of the user’s connection for the duration of 5 hours after the customer exceeds a limit on the amount of data he transmits or receives in a given time interval.
This means that

  • The punishment becomes ineffective if the user is not interested in using the connection after the incident.
  • The punishment does not protect others at the time of congestion.

British Telecom employs a “Fair Usage Policy” according to which a customer’s bit rate will be “restricted” when the customer becomes a “heavy user”.

Please note that the cable standard DOCSIS offers excellent facilities when it comes to QoS. It has 6 quality classes and 8 priority levels. It has total control over upstream (hence can regulate TCP connections by regulating the protocol acknowledgments) and it can also schedule the downstream. The DOCSIS standard is well documented and a number of QoS-related research papers have been written on the topic, most of them focusing on real-world implementation.

Network dimensioning and management

It is the number of customers that largely determines the operator’s income. The infrastructure acquired to realise the sold service reduces profit. It is only natural that an operator tries to increase the former and reduce the latter, given that the service quality is hardly monitored at all and that it is extremely difficult for a customer to claim refunds for bad service. It is obvious that a network operator has great incentives not to support any initiative aimed to objectively measure the quality of the offered service.

It is not practical to infer an operator’s network management because the ISP is not obliged to disclose this information and even if it did, its effect on quality is non-trivial. What is left then is the pursuit of a mechanism which would hold the operator accountable for the service it provides, hence possibly motivating the provider to change their network management.

The rest of this article complains about the lack of accountability and presents 2 hypothetical strategies to increase the accountability.

Operator’s accountability

The mere availability of a data connection is the core of the sold service but it is the quality of broadband provisioning that determines the utility customers derive from it. Yet, it is extremely difficult to prove that a service has been inadequate at some point in time. It is practically impossible for a common user to show that there was for example a packet loss-rate of 40% for the duration of 50 minutes last Saturday afternoon and that it was not the customer’s fault.

Why is it that we can take a broken watch back to the shop and have our money refunded, we can even raise legally sound complaints about complex services such as consulting or insurance but it is almost impossible for a non-techy broadband user to show that something was wrong with their broadband service? What is it about Internet service which makes it so hard to complain about?

For one thing, Internet provisioning is a multi-dimensional service. It spans across several time-scales, across space, it has complex statistical properties and it is perceived subjectively (unlike the quality of electricity or gas). But take the complexity of water quality standards, for example.  They comprise over 50 quantitative parameters every liter of drinking water must satisfy. Yet, utility companies do satisfy these standards and the state usually takes care of their monitoring.

One can argue that an additional set of requirements on home broadband provisioning would increase the cost and in turn the price, having a negative effect on the service proliferation. But surely one can use the same argument in the case of water quality, car safety, and many other areas in which more stringent legal requirements clearly brought benefits far outweighing the cost.

Proving unsatisfactory quality

Part of the Consumer Law related to the provision of broadband is the Sale of Goods & Services Act. Under the Sale of Goods Act 1979 and The Supply of Goods and Services Act 1982 service providers must sell goods that are, among other things,

  • of satisfactory quality and
  • delivered as described.

Of course, satisfactory quality remains undefined and the service is described only vaguely. Furthermore, even if some well-defined quality was breached, there would not be an easy way for a customer to prove it.

Let’s now design a simple hypothetical accountability strategy for today’s home broadband service. The aim here is to create a piece of evidence immune to the operator suggesting that perhaps there was a fault on the customer’s side.

A) Massively deployed application-layer metering

There are 2 ways we can think of, both solid for a court room. Since judges operate on the basis of reasonable belief, we’ll employ some statistics: If a large number of customers at the same time experience, measure and document a bad connection, it is unlikely that this is due to all of them having misconfigured their firewalls or having their cables cut at the same time. Naturally, in several cases it could have been the customer’s fault, but it is beyond reasonable belief that a large group of customers of a particular operator erred at the same time. Hence an application running on the customer’s computer can be used to generate evidence about the service when put together with a large number of other data.

A basic version of this concept is already in place. There are Internet forums where users post their measurements, obtained often from the excellent Now if these measurements were made automatically and the results processed to extract geographical and spatial commonalities, that would be a big step towards holding the ISP accountable.

B) Certified hardware monitors attached to customer modems

This method would rely on a device connected between the modem and user equipment. This device, let’s call it a monitor, will have a certification from some regulatory body such as the UK Ofcom. Operators will be legally obliged to allow this device be connected to the modem they provide. Another party – a governmental organisation or a regulated private company – will collect data from these monitors and make them available to the public. Since monitors are standardized and cannot be modified by the customer, there need not be a large number of them in order to rule out the customer’s fault.

Similarly to the way TV and radio ratings are collected from several customers, so measurement data will be collected from several monitors in a given locality, as illustrated in the figure below.

Both strategies require a start-up investment and some low long-term funding. Most customer will also need incentives to participate in the strategy.


Broadband speeds continue to grow together with the necessity of Internet access and the demands of new applications. Advances on the physical and medium access layer are being adopted by the industry. Innovative Internet applications are booming. Yet the experience of any more-than-slightly advanced Internet users is marred by poor network management, failures, oversubscription and unfair usage. At the same time, the progress on the intermediate layers – IP, transport, management – seems to stagnate. Thousands of research papers on quality provisioning and resource allocation seem to have been written in vain.

Be it a lobby group, customer iniative or the government themselves who will push the idea of accountability into practice, we think it is the key for a better home Internet provisioning.

Posted in congestion, fairness, QoS | Tagged: , , | 1 Comment »