Alibaba unveils congestion
control mechanism for ultra-
high-speed data centres
A
libaba Group has announced
a self-developed data traffic
control mechanism named HPCC,
standing for High Precision Congestion
Control. The technology will provide data
transmission with ultra-low latency, high
bandwidth and high stability. This is an
important milestone towards ultra-high-
speed data centres that are vital to unlock
the potential of AI and IoT.
Researchers from Alibaba have proven
through testbed experiments and large-
scale simulations that HPCC reacts faster
to available bandwidth and congestion
compared with other alternatives, while
maintaining close-to-zero queues. In the
simulations for under 50% traffic load,
tuning. The new HPCC is set to address
this gap.
The researchers found that the
fundamental cause of such limitations in
the existing solutions is the lack of fine-
grained network load information in legacy
networks. However, this status quo has
recently altered with the availability of new
In-band Network Telemetry (INT) features.
HPCC shortens flow completion times by
up to 95%, causing little congestion even
under large-scale incasts.
Faster hardware alone is not sufficient
to lead to ultra-high-speed networking in
www.intelligentdatacentres.com
From years of experience operating large-
scale and high-speed RDMA networks,
Alibaba reports several inherent
limitations in the existing congestion
control solutions available including
slow convergence, unavoidable packet
queueing and complicated parameter
Alibaba’s researchers have proposed HPCC
as it has the potential to leverage INT to
obtain link load information and controls
traffic with high levels of precision. By
addressing challenges such as delayed
INT information during congestion or
overreaction to INT information, HPCC
can quickly utilise free bandwidth to avoid
this issue and can maintain near-zero in-
network queues for ultra-low latency.
HPCC has the added advantage of needing
only three parameters to configure and is
also easy to deploy in hardware. ◊
Issue 08
51
The paper discusses how the performance
of modern data centre networks is essential
to the service quality of cloud and that
faster networking speed can significantly
improve the experience of cloud users.
Driven by the need for faster networks, the
silicon industry has successfully increased
the link speed in data centres from 1Gbps to
100Gbps in the past decade, a growth rate
that continues to outpace Moore’s Law.
data centres. An additional consideration
is that a higher link speed can also be
harmful to the network stability, because
congestion is more likely with faster
senders who are able to simultaneously
transfer data on the network. Congestion
is also harmful to the network latency
experienced by applications because of
queuing delays and potential packet loss.
In particular, new switching ASICs are
able to obtain fine-grained network load
information and use this to provide a
type of congestion control mechanism
that can deliver a steady and ultra-high-
speed network.