2 research outputs found
Birkhoff-von-Neumann Switches with Deflection-Compensated Mechanism
Despite the high throughput and low complexity achieved by input scheduling
based on Birkhoff-von-Neumann (BvN) decomposition; the performance of the BvN
switch becomes less predictable when the input traffic is bursty. In this
paper, we propose a deflection-compensated BvN (D-BvN) switch architecture to
enhance the quasi-static scheduling based on BvN decomposition. The D-BvN
switches provide capacity guarantee for virtual circuits (VCs) and deflect
bursty traffic when overflow occurs. The deflection scheme is devised to offset
the excessive buffer requirement of each VC when input traffic is bursty. The
design of our conditional deflection mechanism is based on the fact that it is
unlikely that the traffic input to VCs is all bursty at the same time; most
likely some starving VCs have spare capacities when some other VCs are in the
overflow state. The proposed algorithm makes full use of the spare capacities
of those starving VCs to deflect the overflow traffic to other inputs and
provide bandwidth for the deflected traffic to re-access the desired VC. Our
analysis and simulation show that this deflection-compensated mechanism can
support BvN switches to achieve close to 100% throughput of offered load even
with bursty input traffic, and reduces the average end-to-end delay and delay
jitter. Also, our result indicates that the packet out-of-sequence probability
due to deflection of overflow traffic is negligible, thus only a small
re-sequencing buffer is needed at each output port
The Mathematical Parallels Between Packet Switching and Information Transmission
All communication networks comprise of transmission systems and switching
systems, even though they are usually treated as two separate issues.
Communication channels are generally disturbed by noise from various sources.
In circuit switched networks, reliable communication requires the
error-tolerant transmission of bits over noisy channels. In packet switched
networks, however, not only can bits be corrupted with noise, but resources
along connection paths are also subject to contention. Thus, quality of service
(QoS) is determined by buffer delays and packet losses. The theme of this paper
is to show that transmission noise and packet contention actually have similar
characteristics and can be tamed by comparable means to achieve reliable
communication, and a number of analogies between switching and transmission are
identified. The sampling theorem of bandlimited signals provides the
cornerstone of digital communication and signal processing. Recently, the
Birkhoff-von Neumann decomposition of traffic matrices has been widely applied
to packet switches. With respect to the complexity reduction of packet
switching, we show that the decomposition of a doubly stochastic traffic matrix
plays a similar role to that of the sampling theorem in digital transmission.
We conclude that packet switching systems are governed by mathematical laws
that are similar to those of digital transmission systems as envisioned by
Shannon in his seminal 1948 paper, A Mathematical Theory of Communication.Comment: 21 pages, 25 figures, Submitted to IEEE Transactions on Information
Theor