TACS is one
of the leading top consultancies in the field of Fixed or Mobile
Access and Core Transport Network Systems, Communication
Networks Traffic Engineering, Communication Networks Optimization
consultants are the first inventors of fixed or mobile packet radio
structures in the world for 2G, 3G, 4G, 5G and 6G wireless systems.
Restoration-Aware Traffic Engineering
Bending light for
Wide area networks (WANs),
the global backbones and workhorses of today's Internet that connect
billions of computers over continents and oceans, are the foundation
of modern online services. As COVID-19 has placed a vital reliance
on online services, today's networks are struggling to deliver high
bandwidth and availability imposed by emerging workloads related to
machine learning, video calls, and health care.
To connect WANs over hundreds of miles, fiber optic cables that
transmit data using light are threaded throughout our neighborhoods,
made of incredibly thin strands of glass or plastic known as optical
fibers. While they're extremely fast, they're not always reliable:
they can easily break from weather, thunder storms, accidents, and
even animals. These tears can cause severe and expensive damage,
resulting in 911 service outages, lost connectivity to the Internet,
and inability to use smartphone apps.
Scientists from MIT's Computer Science and Artificial Intelligence
Laboratory (CSAIL) recently came up with a way to preserve the
network when the fiber is down and reduce cost. Their system, called
"ARROW," reconfigures the optical light from a damaged fiber to
healthy ones, while using an online algorithm to proactively plan
for potential fiber cuts ahead of time, based on real-time Internet
ARROW is built on the crossroads of two different approaches:
"failure-aware traffic engineering (TE)", a technique that steers
traffic to where the bandwidth resources are during fiber cuts, and
"wavelength reconfiguration," which restores failed bandwidth
resources by reconfiguring the light.
Though this combination is powerful, the problem is mathematically
difficult to solve because of its NP-hardness in computational
The team created a novel algorithm that can essentially create "LotteryTickets"
as an abstraction for the "wavelength reconfiguration problem" on
optical fibers and only feed essential information into the "traffic
engineering problem." This works alongside their "optical
restoration method" which moves the light from the cut fiber to
"surrogate'' healthy fibers to restore the network connectivity. The
system also takes real-time traffic into account to optimize for
maximum network throughput.
Using large-scale simulations and a testbed, ARROW could carry
2x-2.4x more traffic without having to deploy new fibers, while
maintaining the network highly reliable.
"ARROW can be used to improve service availability, and enhance the
resiliency of the Internet infrastructure against fiber cuts. It
renovates the way we think about the relationship between failures
and network management—previously failures were deterministic
events, where failure meant failure, and there was no way around it
except over-provisioning the network," says MIT postdoc Zhizhen
Zhong, the lead author on a new paper about ARROW. "With ARROW, some
failures can be eliminated or partially restored, and this changes
the way we think about network management and traffic engineering,
opening up opportunities for rethinking traffic engineering systems,
risk assessment systems, and emerging applications too."
The design of today's network infrastructures, both in datacenters
and in wide-area networks, still follow the "telephony model" where
network engineers treat the physical layer of networks as a static
black box with no reconfigurability.
As a result, the network infrastructure is equipped to carry the
worst-case traffic demand under all possible failure scenarios,
making it inefficient and costly. Yet, modern networks have elastic
applications that could benefit from a dynamically reconfigurable
physical layer, to enable high throughput, low latency, and seamless
recovery from failures, which ARROW helps enable.
In traditional systems, network engineers decide in advance how much
capacity to provide in the physical layer of the network. It might
seem impossible to change the topology of a network without
physically changing the cables, but since optical waves can be
redirected using tiny mirrors, they're capable of quick changes: no
rewiring required. This is a realm where the network is no longer a
static entity but a dynamic structure of interconnections that may
change depending on the workload.
Imagine a hypothetical subway system where some trains might fail
once in a while. The subway control unit wants to plan how to
distribute the passengers to alternative routes while considering
all possible trains and traffic on them. Using ARROW, then, when a
train fails, the control unit just announces to the passengers the
best alternative routes to minimize their travel time and avoid
"My long-term goal is to make large-scale computer networks more
efficient, and ultimately develop smart networks that adapt to the
data and application," says MIT professor Manya Ghobadi, who
supervised the work. "Having a reconfigurable optical topology
revolutionizes the way we think of a network, as performing this
research requires breaking orthodoxies established for many years in
To deploy ARROW in real-world wide-area networks, the team has been
collaborating with Facebook and hopes to work with other large-scale
service providers. "The research provides the initial insight into
the benefits of reconfiguration. The substantial potential in
reliability improvement is attractive to network management in
production backbone." says Ying Zhang, a software engineer manager
in Facebook who collaborates on this research.
"We are excited that there would be many practical challenges ahead
to bring ARROW from research lab ideas to real world systems that
serve billions of people, and possibly reduce the number of service
interruptions that we experience today, such as less news reports on
how fiber cuts affect Internet connectivity," says Zhong. "We hope
that ARROW could make our Internet more resilient to failures with
Zhong wrote the paper alongside MIT professor Manya Ghobadi, MIT
graduate student Alaa Khaddaj, Jonathan Leach, Ying Zhang, and
Yiting Xia of Facebook. They will present the research on ARROW at
ACM's SIGCOMM conference.
The work was led by MIT and is being evaluated for deployment at