netflix太强大了 整个控制internet速度# PDA - 掌中宝
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New Study From M-Lab Sheds Light On Widespread Harm Caused By Netflix
Routing Decisions
On Tuesday, M-Lab released a new study on the impact of network
interconnection on consumer Internet performance. The report entitled “ISP
Interconnection and its Impact on Consumer Internet Performance“, details
findings based on the speed test results collected by its test servers for
various ISPs throughout the country over a roughly two-year period. For
those not familiar with M-Lab, they provide the largest collection of open
Internet performance data used by the FCC, amongst others, for the Measuring
Broadband America program.
M-Lab data shows that around May 2013, suddenly and simultaneously
throughout the country, speed test results for many ISPs (AT&T, Comcast,
CenturyLink, Time Warner Cable, and Verizon) experienced a sudden and
significant decline in performance to a specific set of transit providers (
Cogent, Level 3 and XO). Just as suddenly around March 2014 the performance
returns to normal for most of these same ISPs. Coincidentally, a few other
ISPs who Netflix had negotiated direct Open Connect connections (Cablevision
and Cox) did not experience similar decline in performance. The data
presented in the study confirms what myself and others have surmised about
Netflix being ultimately responsible for the dramatic, simultaneous decline
in Netflix performance for all non-Open Connect ISPs.
If you look at the M-Lab measured history of the congestion, you will notice
that these timelines line up very closely with Netflix’s migration from
3rd party CDNs onto their own Open Connect platform. The performance impact
also matches closely with ISPs that did not agree to provide Netflix with
Free Peering while other ISPs that agreed did not experience a performance
impact.
96C2FD9F-3407-42DE-B9A0-C7C2971F9D40Looking at Figure 1 from the report (
below), we can see that performance suddenly degrades for three of the four
major broadband companies in the NY metro area according to an M-Lab test
server housed on Cogent’s network in NYC around May 2013 and then
performance suddenly improves for all three around March 2014. This tight
coordination of impact for multiple ISPs simultaneously suggests that the
cause was not something done by the ISPs, but rather by another entity. (
Note: I added the heading and arrows to the chart)
36F74188-CE96-4A91-899F-AD8E14F61624What entity might be responsible? Well,
figure 2 shows us that the fourth broadband ISP in the NY metro area testing
on the M-Lab server on Cogent’s network, Cablevision (the only one of the
four with a direct connection to Netflix’s Open Connect CDN) did not
experience the same sudden drop/rise in performance over their link to
Cogent.
image002
Finally, M-Lab’s report also helpfully includes performance results for all
four broadband ISPs in NY from a test server located on a different
backbone connection (one that was not providing transit service to Netflix)
showing no sudden performance changes for any ISP.
image003
The report also shows that direct interconnection agreements between Comcast
/Netflix increased performance for other ISPs. Unless there were performance
issues further upstream of the interconnection, there should have been no
impact on the interconnection agreement between Comcast/Netflix on other ISP
networks. And according to M-Lab’s findings, performance issues on ISPs
networks were not due to technical issues but rather the business deals
between ISPs. They say, “we were able to conclude that in many cases
degradation was not the result of major infrastructure failures at any
specific point in a network, but rather connected with the business
relationships between ISPs“.
While some may want to take this report as a smoking gun that ISPs are
causing congestion, they may forget, not understand, or purposely leave out,
the fact that large content providers control the delivery of their traffic
and can AVOID congestion. A recent MIT study “Measuring Internet
congestion: A preliminary report” pointed out the fact that the ISPs
singled out in this report have multiple alternative paths to reach them.
The report states that, “Congestion at interconnection points does not
appear to be widespread. Apart from specific issues such as Netflix traffic,
our measurements reveal only occasional points of congestion where ISPs
interconnect. We typically see two or three links congested for a given ISP,
perhaps for one or two hours a day, which is not surprising in even a well-
engineered network, since traffic growth continues in general, and new
capacity must be added from time to time as paths become overloaded.”
Most agree that when Netflix, again, moved their traffic off of these newly
congested paths to direct connections, performance improved both for Netflix
services as well as other services impacted by this new congestion. What is
puzzling however is the timing of this improvement. If you look at the
graph above you will notice that all ISPs improved simultaneously in Feb
2014. This is the exact same time that Netflix and Comcast migrated traffic
to their direct connection. While it is understandable that Comcast would
improve, no one has explained how a Comcast direct connection would improve
AT&T, Verizon, and Time Warner unless there were additional problems between
the Netflix server and their transit ISPs themselves. When Netflix moved
this traffic their congestion within their transit ISPs improved other
destinations.
What M-Labs is trying to do is good for the Internet, but they need to
expose more of the end-to-end problem. If they truly want to understand
Internet congestion and user experience, they need to not only focus on
interconnect, but they also should expand their measurement to the quality
of transit ISPs and acknowledge the choices content sources make when
delivering traffic to their customers. For example, a measurement can
identify if there are material differences between a variety of OTT sources
such as Amazon Prime, Netflix, Hulu and YouTube on a given ISP. If Amazon
Prime HD video quality was excellent, but another source was poor, it would
be interesting to determine why that’s occurring, and what options the
content provider has to improve their services.
While many were quick to blame ISPs for problems consumers were having with
their Netflix streaming experience, we’ve now have a lot of data in the
market showing that the choices Netflix made directly impacted the quality
of their video and other services as well. Between this new M-Lab data, the
interconnection findings published by David Clark at MIT/CAIDA, this data,
and a recently published research report that says Netflix is using calls
for greater net neutrality to drive down the prices they pay, it’s now
clear just how much control Netflix really has over the quality of video
they deliver.
Routing Decisions
On Tuesday, M-Lab released a new study on the impact of network
interconnection on consumer Internet performance. The report entitled “ISP
Interconnection and its Impact on Consumer Internet Performance“, details
findings based on the speed test results collected by its test servers for
various ISPs throughout the country over a roughly two-year period. For
those not familiar with M-Lab, they provide the largest collection of open
Internet performance data used by the FCC, amongst others, for the Measuring
Broadband America program.
M-Lab data shows that around May 2013, suddenly and simultaneously
throughout the country, speed test results for many ISPs (AT&T, Comcast,
CenturyLink, Time Warner Cable, and Verizon) experienced a sudden and
significant decline in performance to a specific set of transit providers (
Cogent, Level 3 and XO). Just as suddenly around March 2014 the performance
returns to normal for most of these same ISPs. Coincidentally, a few other
ISPs who Netflix had negotiated direct Open Connect connections (Cablevision
and Cox) did not experience similar decline in performance. The data
presented in the study confirms what myself and others have surmised about
Netflix being ultimately responsible for the dramatic, simultaneous decline
in Netflix performance for all non-Open Connect ISPs.
If you look at the M-Lab measured history of the congestion, you will notice
that these timelines line up very closely with Netflix’s migration from
3rd party CDNs onto their own Open Connect platform. The performance impact
also matches closely with ISPs that did not agree to provide Netflix with
Free Peering while other ISPs that agreed did not experience a performance
impact.
96C2FD9F-3407-42DE-B9A0-C7C2971F9D40Looking at Figure 1 from the report (
below), we can see that performance suddenly degrades for three of the four
major broadband companies in the NY metro area according to an M-Lab test
server housed on Cogent’s network in NYC around May 2013 and then
performance suddenly improves for all three around March 2014. This tight
coordination of impact for multiple ISPs simultaneously suggests that the
cause was not something done by the ISPs, but rather by another entity. (
Note: I added the heading and arrows to the chart)
36F74188-CE96-4A91-899F-AD8E14F61624What entity might be responsible? Well,
figure 2 shows us that the fourth broadband ISP in the NY metro area testing
on the M-Lab server on Cogent’s network, Cablevision (the only one of the
four with a direct connection to Netflix’s Open Connect CDN) did not
experience the same sudden drop/rise in performance over their link to
Cogent.
image002
Finally, M-Lab’s report also helpfully includes performance results for all
four broadband ISPs in NY from a test server located on a different
backbone connection (one that was not providing transit service to Netflix)
showing no sudden performance changes for any ISP.
image003
The report also shows that direct interconnection agreements between Comcast
/Netflix increased performance for other ISPs. Unless there were performance
issues further upstream of the interconnection, there should have been no
impact on the interconnection agreement between Comcast/Netflix on other ISP
networks. And according to M-Lab’s findings, performance issues on ISPs
networks were not due to technical issues but rather the business deals
between ISPs. They say, “we were able to conclude that in many cases
degradation was not the result of major infrastructure failures at any
specific point in a network, but rather connected with the business
relationships between ISPs“.
While some may want to take this report as a smoking gun that ISPs are
causing congestion, they may forget, not understand, or purposely leave out,
the fact that large content providers control the delivery of their traffic
and can AVOID congestion. A recent MIT study “Measuring Internet
congestion: A preliminary report” pointed out the fact that the ISPs
singled out in this report have multiple alternative paths to reach them.
The report states that, “Congestion at interconnection points does not
appear to be widespread. Apart from specific issues such as Netflix traffic,
our measurements reveal only occasional points of congestion where ISPs
interconnect. We typically see two or three links congested for a given ISP,
perhaps for one or two hours a day, which is not surprising in even a well-
engineered network, since traffic growth continues in general, and new
capacity must be added from time to time as paths become overloaded.”
Most agree that when Netflix, again, moved their traffic off of these newly
congested paths to direct connections, performance improved both for Netflix
services as well as other services impacted by this new congestion. What is
puzzling however is the timing of this improvement. If you look at the
graph above you will notice that all ISPs improved simultaneously in Feb
2014. This is the exact same time that Netflix and Comcast migrated traffic
to their direct connection. While it is understandable that Comcast would
improve, no one has explained how a Comcast direct connection would improve
AT&T, Verizon, and Time Warner unless there were additional problems between
the Netflix server and their transit ISPs themselves. When Netflix moved
this traffic their congestion within their transit ISPs improved other
destinations.
What M-Labs is trying to do is good for the Internet, but they need to
expose more of the end-to-end problem. If they truly want to understand
Internet congestion and user experience, they need to not only focus on
interconnect, but they also should expand their measurement to the quality
of transit ISPs and acknowledge the choices content sources make when
delivering traffic to their customers. For example, a measurement can
identify if there are material differences between a variety of OTT sources
such as Amazon Prime, Netflix, Hulu and YouTube on a given ISP. If Amazon
Prime HD video quality was excellent, but another source was poor, it would
be interesting to determine why that’s occurring, and what options the
content provider has to improve their services.
While many were quick to blame ISPs for problems consumers were having with
their Netflix streaming experience, we’ve now have a lot of data in the
market showing that the choices Netflix made directly impacted the quality
of their video and other services as well. Between this new M-Lab data, the
interconnection findings published by David Clark at MIT/CAIDA, this data,
and a recently published research report that says Netflix is using calls
for greater net neutrality to drive down the prices they pay, it’s now
clear just how much control Netflix really has over the quality of video
they deliver.
