[e2e] Is a non-TCP solution dead?

[Injong Rhee]

Hi,

I just came back from industry after working for a wireless multimedia
software company for about two years; this company makes media servers, and
clients that run on wireless handsets -- the servers and clients run at the
end points. One thing I found in the field is lack of network transport. The
only thing available was TCP and UDP. But its performance on CDMA 2.5G/3G
(which is the network I have been working over) wasn't so great. It is
because of well-known problems with the losses not being indicative of
congestion.

So what we did was to develop our own flow control protocol that can run on
top of UDP. Its performance was simply "better" than TCP. We could not find
any alternative to this solution since all the existing/proposed solutions
(maybe I am not ignorant) require some changes in TCP and the
infrastructure -- I mean by "infrastructure" any changes that the wireless
service providers have to do such as changes in routers, link-level
mechanisms, base stations (BSC, BTS, PSDN), or any components in their OSS
networks. We couldn't ask our customers (wireless carriers) to do this nor
you can change TCP (since this requires some deals with Qualcomm -- you know
how that goes). So we changed our systems to support new protocols. Since we
had media servers and clients, this wasn't difficult.

Recently, I was talking to some folks here about the protocol. The first
response I get is the following: "Since the protocol requires change in the
server and also client, this is the same as changing infrastructure; so our
solution has deployment problems." Or "Since all the applications use TCP,
why not use TCP? Also if you need any change, all the changes must be at the
TCP sender. Otherwise you can't deploy your solution." Or "There are a lot
of work in modifying TCP for better performance on wireless networks; why
not use them?"

This view is too simplistic and I disagree with this. First all, the
wireless world is tightly controlled by wireless service providers. They
control applications that run on handsets, media servers, and even content
providers. In addition, it is often the case that software companies
(typically small startups) have to develop both servers and clients -- look
at mobile game companies. For these companies, modifying their servers and
clients to provide better network performance is not that difficult to do --
in fact, as long as this change brings in more revenue and edges over their
competitors, they are more than willing to do this. Also deploying new
updates to customer handsets are easy now because of BREW or J2ME (FYI, we
developed both solutions). For instance, in South Korea, a new release to
client software can be deployed to the entire network in the matter of days.

The wireless revolution is a new phenomena happening in the rest of the
world, but not in the US. The Far East (China, Japan, South Korea, Hong
Kong, Singapore, etc) exhibits a completely different market
trend/strategies from the US. I think it is incorrect to assume that every
practice we have done in the wired IP world (esp., in the US market) is
automatically applicable to the wireless world. It is a different world out
there.

Any comments?

Injong Rhee
rhee at csc.ncsu.edu
www.csc.ncsu.edu/faculty/rhee