Hello and welcome to this presentation about
leveraging the ZeroRTT Convert protocol to
improve Wi-Fi and cellular convergence.
Behind this long title, there is an experiment I
would like to describe.
But first, I will start by describing why we
wanted to do this experiment, simply by
showing the current and future situation.
I will also present which technologies are
available today to solve the problem.
Then I will be able to briefly expose the main
results we got before making some conclusions.
For technical reasons, it is not possible for me
to know the background of the origins.
I hope you don't mind if I spend a bit more time
explaining the current situations, issues
mobile operators have and the different
technologies available today to solve that.
Feel free to get a coffee if you already know all
of that, but at least, and I hope, everybody
should be able to understand the second part.
It is not difficult to believe the traffic on
cellular networks is increasing.
According to this report from Ericsson, it will
continue to grow over the years.
Already today, the cellular traffic is
significant.
For a third of the operators here on the graph,
the averaged data usage per reported SIM per
month is already above 10 gigs.
A simple solution to cope with this increase of
traffic for the operators is to improve
the network, to avoid any saturation of course.
Yes, but the average revenue of these operators
is not growing.
Despite the pandemic we got, I don't know if you
remember, people were forced to stay
home to save the world.
Anyway, despite the exceptional situation in 2020,
the global cellular traffic this
year increased but not the revenue.
If we have to reduce the cost, then another
solution is to use the existing fixed
infrastructure.
Indeed, millions of Wi-Fi hotspots are already
available in many different places.
You might have heard about solutions like Phon or
Eduroam, or simply your operator's
hotspot, also called Free Wi-Fi.
Many operators have already deployed their own
hotspot solution just for their clients.
But today, the wireless broadband alliance,
supported by many different network operators
in the world, is looking at a global solution
under the name of Open Roaming.
Operators would share resources in order to
relieve cellular traffic congestion.
But there are drawbacks.
As an end user, would you be ready to be
disconnected when switching from one network to
another?
Or potentially switch to more limited networks?
Did you not already disconnect your device from a
Wi-Fi access point because a cellular
network was better at that time?
A solution to that problem would then be to use
multiple networks at the same time.
Multipath TCP can help you there.
MPTCP is an extension to TCP and it's
standardized in the RHC 8684.
To describe MPTCP, we can do that in one sentence.
It allows to exchange data for a single
connection over different paths, simultaneously
or not.
Instead of having one connection limited to one
path, the same connection can go over
multiple paths.
In other words, you can then have more redundancies.
But you can also have more bandwidths and more
many things like supporting handover
and mobility use case, like here switching from
one weak network to another, where all
the signals are quite valuable.
But this extension to TCP needs to be supported
by both the client and the server.
On the client side, some smartphones already
support it, like the one from Apple since
2013, but also some others from Samsung, LG and
more, even if it's restricted to some
applications.
As shown on the MPTCP.io website, on the server
side, the support is not very significant
for the moment, for various reasons we are
actively working on it.
But wait, again, there is a solution.
A TCP proxy can be used at operators' network to
bring MPTCP support.
But what kind of proxy should we use?
Here we are interested by a new protocol, 0RTT
TCP convert protocol.
It eases the deployment of TCP extensions like MPTCP.
Technically, it uses TCP fast open, with fallback
support of course, to carry information about
the end server.
Note that the client and server proxies can
exchange additional data in the three-way
handshake, for example, to support an additional
authentication path.
If we compare the flow to initiate the connection,
it is a lot shorter than solutions like Socks
Vify using Coria with their Giga LTE.
In the end, all the solutions I presented here,
combining MPTCP with the 0RTT convert,
is already part of the future 5G.
Indeed, in the 3GPP release 16, an ATSSS function
is defined.
ATSSS stands for Access Traffic Steering Switching
Splitting.
And it combines our two technologies to play a
key role in managing data traffic between
3GPP, so 5G, 4G, and other networks, and non-3GPP
networks like Wi-Fi or private networks.
Enough with the introduction.
Let's have a look at our experiments and at the
main results we extracted from them.
From a high-level viewpoint, we have a smartphone
connected to two networks.
The first one is a DSL network connected via Wi-Fi.
It is a home network, unfortunately limited to 10Mbps.
I say "unfortunately" because it is my home
connection.
The other network is a public LTE network, giving
more than 20Gbps, but it is variable.
A 0RTT convert server is deployed on the internet,
and the phone is simply playing live video
streams from Twitch.
Specifically, the smartphone is a Xiaomi Pocophone
F1 with a modified kernel to have MPCP support.
A modified version of ThreadOsup supporting the 0RTT
TCP convert protocol is installed.
Please note that all the material has been open-source,
and a nice guide is available
on the TSRS website.
For the TCP proxy server side, we took a server
called HAG used for hybrid networks.
It follows broadband foreign standards and
supports 10,000 users with 10Gbps throughput
and 300,000 connections per server.
Of course, here it has been modified to support
the 0RTT convert protocol.
For this experiment, it has been deployed in the
cloud close by at Amazon.
Regarding the results, we can focus here on two
scenarios.
For the first one, the goal is to support handovers.
Here we are disconnected from the Wi-Fi access
point between the two green lines.
When we are connected to the fixed network and
the Wi-Fi, we use it in priority.
Here the DSL network can cope with the request
speed so the traffic is fully offloaded to
the fixed network, excellent for the operators.
Here in the second scenario, the DSL network is
not enough to watch a 4K live stream.
We can clearly see on the graph before and after
the green lines that the cellular network
is used in a second priority.
The main point here is that it is used in
addition to provide enough bandwidth to play
the 4K live stream without delays.
It then helps to improve the user experience
while still minimizing its utilization.
That's good for the end user.
It is already time for conclusion.
This proof of concept shows that the future ATS-SS
already works.
On one hand, it helps mobile operators to reduce
their mobile traffic while also helping
to improve the end user experience.
MPCP and the ZeroRTT convert can play a role in
Wi-Fi and cellular convergence today in
4G networks and tomorrow in all 5G networks tend
to the ATS-SS.
If you have any questions, please share that with
me.
But you can also contact me by email or Twitter.