Re: China’s Slow Transnational Network

Mon Mar 2 22:36:35 UTC 2020

Did you compare CERNET with commodity networks?  (My anecdotal observations
from a couple years ago suggest that Internet2 to CERNET is very good when
other paths are poor to unusable.)

--David Burns

On Mon, Mar 2, 2020 at 7:58 AM Pengxiong Zhu <pzhu011 at ucr.edu> wrote:

> Hi all,
>
> We are a group of researchers at University of California, Riverside who
> have been working on measuring the transnational network performance (and
> have previously asked questions on the mailing list). Our work has now led
> to a publication in Sigmetrics 2020 and we are eager to share some
> interesting findings.
>
> We find China's transnational networks have extremely poor performance
> when accessing foreign sites, where the throughput is often persistently
> low (e.g., for the majority of the daytime). Compared to other countries
> we measured including both developed and developing, China's transnational
> network performance is among the worst (comparable and even worse than some
> African countries).
>
> Measuring from more than 400 pairs of mainland China and foreign nodes
> over more than 53 days, our result shows when data transferring from
> foreign nodes to China, 79% of measured connections has throughput lower
> than the 1Mbps, sometimes it is even much lower. The slow speed occurs only
> during certain times and forms a diurnal pattern that resembles congestion
> (irrespective of network protocol and content), please see the following
> figure. The diurnal pattern is fairly stable, 80% to 95% of the
> transnational connections have a less than 3 hours standard deviation of
> the slowdown hours each day over the entire duration. However, the speed
> rises up from 1Mbps to 4Mbps in about half an hour.
>
>
> We are able to confirm that high packet loss rates and delays are incurred
> in the foreign-to-China direction only. Moreover, the end-to-end loss rate
> could rise up to 40% during the slow period, with ~15% on average.
>
> There are a few things noteworthy regarding the phenomenon. First of all,
> all traffic types are treated equally, HTTP(S), VPN, etc., which means it
> is discriminating or differentiating any specific kinds of traffic. Second,
> we found for 71% of connections, the bottleneck is located inside China
> (the second hop after entering China or further), which means that it is
> mostly unrelated to the transnational link itself (e.g., submarine cable).
> Yet we never observed any such domestic traffic slowdowns within China.
> Assuming this is due to congestion, it is unclear why the infrastructures
> within China that handles transnational traffic is not even capable to
> handle the capacity of transnational links, e.g., submarine cable, which
> maybe the most expensive investment themselves.
>
> Here is the link to our paper:
> https://www.cs.ucr.edu/~zhiyunq/pub/sigmetrics20_slowdown.pdf
>
> We appreciate any comments or feedback.
> --
>
> Best,
> Pengxiong Zhu
> Department of Computer Science and Engineering
> University of California, Riverside
>
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