Some strands of the World Wide Web are getting a little tattered.
When
it comes to delivering data to users, the Web still works brilliantly.
But for other functions such as allowing users to move between wireless
networks or companies to shift traffic among servers, engineers are
forced to implement increasingly cumbersome tweaks.
In
part, that is a function of the Internet’s growth. What began as an
elegant method to transfer data among a small number of computers has
evolved into a massive makeshift system in which designers have added
workarounds on top of earlier layers of fixes.
Now,
a team of Princeton University researchers has released a plan to cut
through that tangle and provide a simple solution to many of the
problems involved with the Internet’s growing pains. Called Serval,
the system makes a small change to the way programs download and manage
data that could have a big impact on the future development of the Web.
“Smart
engineers are great at mastering complexity and hacking around it. But
with the current approach, everybody needs to reinvent the wheel,” said
Michael Freedman, an assistant professor of computer science who heads
the Serval development team. “Serval is something that will make things
easier to build and easier to manage without relying on these hacks.”
The
team has put together a small Princeton network to demonstrate Serval’s
function and is moving into testing the system in larger and more
complex deployments. Serval fixes problems by augmenting the role of one
of the foundations of the Internet—the IP address. The IP, or Internet
Protocol, address is the fundamental identifier for computers and other
devices on the Internet. It is critical both for transferring
information and for programs that use the data at its ultimate
destination.
One
way to think about this is to imagine the IP address is a street
address such as 1 Main St. When packets of information need to find
their way to your computer, they use the IP address. When the
information arrives, the IP address of the transmitting computer also
plays a role in allowing your computer to recognize information needed
for specific applications such as Firefox or QuickTime (there are a
number of other programs involved, but the IP address is one step in
allowing your computer to say ‘Oh, yes, this is the data I need to run
this YouTube video.’)
That
worked well in the early days of the Internet when users wanted to
connect to a specific computer. But now, people are not interested in
connecting to a single computer, they want to connect to services such
as Google or Wikipedia. Unfortunately, because the IP address is still
linked to specific machines, there is no easy way to do that.
The
problem is that the IP address cannot change without messing everything
up. Computer programs that rely on the IP address have no easy way to
adjust if the IP address changes, a possibility that is increasingly
common as mobile devices proliferate. Without a clever hack, the program
just stops.
“A
lot of applications can be rewritten to hide the fact that you break
your connection and re-establish it,” said Jennifer Rexford, the Gordon
Y.S. Wu Professor in Engineering who is also working on Serval. “But it
makes things unnecessarily complex and more expensive.”
Serval
does not replace the IP address, which continues to function as usual.
Instead, Serval works by adding another layer of information, called the
service access layer, to certain packets contained in a data stream.
Unlike the IP address, which identifies a specific computer, the service
access layer identifies a service such as Google or Facebook. So if the
IP address changes, the program does not stop because it receives the
functional information it needs from the service access layer.
This
makes it easier for users to watch a movie while their tablet computer
switches between a Wi-Fi stream and a cellular one. It also allows a
mobile device to use Wi-Fi and cellular service at the same time.
“The
Internet is increasingly a platform for connecting mobile users with
the cloud and the Internet was not designed to do that,” Rexford said.
“All the work that goes into shoehorning that into the old network
architecture is very difficult.”
Serval
also makes it much easier for Internet companies to shift traffic among
different servers. While not as immediately important to individual
users, this function could allow for drastic increases in efficiency for
Internet companies, and it could play an important role in the future
development of the Internet in general.
Remember
the 1 Main St. analogy? Big companies such as Google have expanded far
beyond an initial address such as 1 Main St. Now, the company has
thousands of servers, branch offices if you will, and Serval will allow
company managers to switch users among offices seamlessly or allow
subdivisions within individual offices to serve different users. To do
that now, the companies have to rely on expensive and hard-to-manage
workarounds. With Serval, it would be straightforward.
Gary
Berger, a lead engineer at Cisco Systems, said bringing greater
flexibility to the network is a goal that many organizations would
welcome. Although not affiliated with the development of Serval, Berger
is reviewing the project to see whether Cisco could perform some
in-house testing of the Serval system. Internet companies are looking at
a number of options, but Berger said that Serval offers a possible
solution to basic problems that are limiting the growth of the
InterneT—many of which can’t be easily solved by further patches.
“You
can’t solve all the problems by incrementally adding to the
architecture because it is fundamentally broken at a basic level,”
Berger said. “Serval helps us to think differently about the problem,
which will benefit everyone.”
One
advantage of Serval is that the system can be deployed incrementally
and does not require massive changes to current networks. For users who
do not use Serval, the additional data layer in packets will be
invisible and the IP address will remain as the identifier. In cases
where Serval is used, the researchers estimate that it will increase the
amount of time data takes to transit the Web by less than 1%.
Berger
said the Serval team has already addressed the issue of making
applications work with the service access layer rather than the IP
address alone. He said that was the most technically complex and the
most important part of Serval. But Berger noted there are still
questions that have to be answered regarding how Serval will function in
the broader context of the Internet, and what potential problems could
crop up if it were widely deployed.
Erik Nordström, a research scholar in the computer science department and the lead author of the team’s conference paper
on Serval, said the group has been meeting with Internet companies and
service providers to inform them of the system’s advantages. He said it
can be difficult to convince large organizations to make fundamental
changes, particularly when they already invested considerable sums into
the software that runs their systems.
“We’d
like to understand how we can make Serval more attractive for others to
adopt, especially when it comes to managing large-scale Web services,”
Nordström said.
Serval
was developed with support from the National Science Foundation, the
Defense Advanced Research Projects Agency, the Office of Naval Research
and Cisco Systems. The authors of the Serval paper were: Nordström,
David Shue, Prem Gopalan, Robert Kiefer, Matvey Arye, Steven Y. Ko,
Rexford and Freedman. All are with the Princeton School of Engineering
and Applied Science’s Department of Computer Science.
Nordström
said the Serval team would like to follow up with a wider deployment of
the system to understand engineering challenges at a larger scale and
in a more realistic environment.
He
said the next step will allow the team “to better understand practical
limitations and benefits of Serval, and also provide us with a complete
deployment strategy that we can present to interested parties.”
A copy of the most recent conference paper on Serval can be found here.
