China’s Slow Transnational Network

Pengxiong Zhu pzhu011 at ucr.edu
Mon Mar 2 05:00:05 UTC 2020


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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