11110729
Active bridging
Active networks accelerate network evolution by permitting the network infrastructure to be programmable, on a per-user, per-packet, or other basis. This programmability must be balanced against the safety and security needs inherent in shared resources.This paper describes the design, implementation, and performance of a new type of network element, an Active Bridge. The active bridge can be reprogrammed "on the fly", with loadable modules called switchlets. To demonstrate the use of the active property, we incrementally extend what is initially a programmable buffered repeater with switchlets into a self-learning bridge, and then a bridge supporting spanning tree algorithms. To demonstrate the agility that active networking gives, we show how it is possible to upgrade a network from an "old" protocol to a "new" protocol on-the-fly. Moreover, we are able to take advantage of information unavailable to the implementors of either protocol to validate the new protocol and fall back to the old protocol if an error is detected. This shows that the Active Bridge can protect itself from some algorithmic failures in loadable modules.Our approach to safety and security favors static checking and prevention over dynamic checks when possible. We rely on strong type checking in the Caml language for the loadable module infrastructure, and achieve respectable performance. The prototype implementation on a Pentium-based HP Netserver LS running Linux with 100 Mbps Ethernet LANS achieves ttcp throughput of 16 Mbps between two PCs running Linux, compared with 76 Mbps unbridged. Measured frame rates are in the neighborhood of 1800 frames per second.
18179112
Balancing performance and flexibility with hardware support for network architectures
The goals of performance and flexibility are often at odds in the design of network systems. The tension is common enough to justify an architectural solution, rather than a set of context-specific solutions. The Programmable Protocol Processing Pipeline (P4) design uses programmable hardware to selectively accelerate protocol processing functions. A set of field-programmable gate arrays (FPGAs) and an associated library of network processing modules implemented in hardware are augmented with software support for function selection and composition, and applied to processing-intensive portions of a user-programmable protocol stack. The system is sufficiently flexible to support protocol stacks that are dynamically altered in reaction to changing network conditions or user needs.The P4 can be transparently inserted into a conventional protocol architecture, such as that of TCP/IP. This experimental demonstration shows that the P4's programmability can be used to significantly improve the performance of TCP/IP under operating conditions where the protocol would perform poorly without augmentation. Generalizing from these experiments, the P4 is shown to have many applications as an open platform for implementing adaptive and programmable networks, and has illustrated new security issues that arise in FPGA-based architectures.The P4 and closely-related systems, such as network processors, are attractive architectural solutions to balancing performance and flexibility.
30871480
Optimized Encodings of Fragments of Type Theory in First-Order Logic
106215
A stochastic integer programming approach to solving a synchronous optical network ring design problem
We develop stochastic integer programming techniques tailored toward solving a Synchronous Optical Network (SONET) ring design problem with uncertain demands. Our approach is based on an L-shaped algorithm, whose (integer) master program prescribes a candidate network design, and whose (continuous) subproblems relay information regarding potential shortage penalty costs to the ring design decisions. This naive implementation performs very poorly due to two major problems: (1) the weakness of the master problem relaxations, and (2) the limited information passed to the master problem by the optimality cuts. Accordingly, we enforce certain necessary conditions regarding shortage penalty contributions to the objective function within the master problem, along with a corresponding set of valid inequalities that improves the solvability of the master problem. We also show how a nonlinear reformulation of the model can be used to capture an exponential number of optimality cuts generated by the linear model. We augment these techniques with a powerful upper-bounding heuristic to further accelerate the convergence of the algorithm, and demonstrate the effectiveness of our methodologies on a test bed of randomly generated stochastic SONET instances. © 2004 Wiley Periodicals, Inc. NETWORKS, Vol. 44(1), 12–26 2004
952506
ID Modulation: Embedding Sensor Data in an RFID Timeseries
This paper reports the first use of ID Modulation to embed a bitstream representing sensor information in a standards-compliant Radio Frequency Identification (RFID) channel. Like other forms of information hiding, ID Modulation embeds a new, lower bit-rate channel in a pre-existing host channel, without requiring any changes to the protocols defining the host channel. Like most other forms of information hiding, the embedded data is represented as correlations introduced into the host channel data stream. Most previous applications of information hiding have emphasized either secrecy (as in steganography) or robustness to removal (as in watermarking). The benefit of information hiding that is most important for the application reported here is backward compatibility with pre-existing standards and hardware. It has allowed us to build a new communication layer (for transmitting sensor data) on top of current RFID infrastructure.
5406998
Security for Virtual Private Intranets
As telecommuting grows, businesses must consider security when extending their network environment to employees' homes. Researchers at the University of Pennsylvania have addressed the problem with smart cards, operating system modifications, and network authentication. We note the distinction between trust and integrity: trust is determined through the verification of components and the dependencies among them, while integrity demonstrates that components haven't been modified. Thus integrity checking in a trustworthy system is about preserving an established trust or trust relationship. Our solution to the challenge of isolating functional roles that may share a single hardware platform is called secure identity based lending (SIBL). SIBL provides multiple personalities by partitioning the hard drive into n+1 partitions, where n is the number of supported personalities. All personalities use the system partition for core operating system components and shared applications. Each of the personalities is also associated with one of the remaining partitions, which are encrypted using a symmetric algorithm.
13121681
A parallel algebra for object databases
The paper describes an algebra for use with parallel object databases, and in particular ODMG compliant databases with OQL. Although there have been many proposals for parallel relational database systems, there has been much less work on parallel object databases, and on parallel query processing for object databases. The parallel algebra presented in the paper is an extension of an existing physical algebra for OQL, and has an important role during query optimization, and for describing execution plans. The paper presents not only the algebra, but also its role in the architecture of a parallel database.