The Exokernel Operating System and Active Networks - Advanced Operating Systems and Kernel Applications - page 151

active networks.Active networks provide a means
to 1) easily integrate new technologies into the
network infrastructure, 2) optimize performance,
and 3) easily accommodate new services. Because
the Exokernel makes our example of active net-
working possible, the Exokernel must share in the
credit of giving rise to a solution to the problems
with networks as identified by DARPA.

proach has to be eliminated. Previously (section
3.4), we explained that it is not necessary to cus-
tomize an entire operating system. In fact, many
users may not even need to customize any of the
operating system. They may simply rely on the
services provided by the user level library. So, as
long as users are using the standard code found in
the user level library, they are all using the same
version of the operating system and therefore
the customer service issue becomes a non-issue.
It is only those users that decide to modify and
optimize the libraries that pose the problem to
customer service.
Presumably, users that are savvy enough to op-
timize their own code are probably savvy enough
to trouble-shoot the issues that may arise from
working with such a flexible operating system. In
reality, it might not even be individual users that
are optimizing their own code but rather software
manufacturers that customize a user-level library
so their product works faster on the extensible
operating system. If this were the case, then per-
haps there is no additional customer support issue
for users of the standard user level libraries, and
perhaps customer support issues that arise from
optimized user-level libraries should be handled
by the creators of the optimized code. So, if the
customer support issue is even an issue at all, it
becomes and issue for the optimizers of the user-
level libraries and not an issue for the engineers
of the extensible operating system. Thus, perhaps
an extensible operating system should be brought
to market and second-party software manufactur-
ers should accept the responsibility of customer
support if they choose to modify the standard
user libraries.
On the other hand, as was stated previously
“extensibility could actually help the customer
support issue” (Leschke, 2004). In so far as ex-
tensible operating systems are easier to fix, then
it should be easier to eliminate bugs and offer
the community a more solid, error-free operating
system. Since user level libraries can be replaced
independently of the kernel, providing updated and

analySiS and diScuSSion

In the following paragraphs, we present some of
the criticisms of the Exokernel Operating System
that have been offered by some of her detractors.
We address the criticisms and offer some of our
own. We offer further comments and reactions
as a way to stimulate more discussion about the
Exokernel Operating System.

customer-Support

We begin our commentary with a quote from Jeff
Mogul of Compaq Western Research Laboratory.
Mogul says, “Extensibility has its problems. For
example, it makes the customer-support issues
a lot more complicated, because you no longer
know which OS each of your customers is run-
ning” (Milojicic, 1999).
What Jeff Mogul seems to be pointing out
is that each extensible operating system can be
modified to the point of being unique. If each
extensible operating system is user-modified
and user-configured, then the challenge becomes
how to efficiently provide customer support for a
group of users if each user is essentially using a
different operating system. For example, if both
the file management system and the communica-
tion manager are uniquely modified, then trying
to solve the issues that arise from their interaction
could be very difficult.
Although providing customer support for an
extensible operating system might present new
challenges, it does not mean the extensible ap-