4.1 Output Queueing / Shared Buffer (U.Crete, CS-534)

CS-534: Packet Switch Architecture
Spring 2003

Department of Computer Science
© University of Crete, Greece

4.1 The Output Queueing / Shared Buffer Family

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Switch Queueing Architectures

Conceptual Derivation/Taxonomy of Queueing Architectures: subrectangles inside a crossbar

Output Queueing: The Reference Arcitecture

Shared Buffer: Top Performance at Low Cost for small N

Buffer Space Requirements:

When the incoming traffic consists of fixed-size packets from independent, identically distributed (i.i.d.) Bernoulli processes, with uniformly-distributed destination (output) ports, analysis and simulation have yielded the results plotted below. Primary source: M. Hluchyj, M. Karol: "Queueing in High-Performance Packet Switching", IEEE Journal on Sel. Areas in Commun. (JSAC), vol. 6, no. 9, Dec. 1988, pp. 1587-1597 (© copyright IEEE).

Attention: results derived for i.i.d. Bernoulli (non-bursty) arrivals, with uniformly-distributed destinations (no overloaded hot-spots), are only useful for gaining a rough, first insight into the behavior of systems, but are often not representative of the real behavior of systems under real traffic!...

Output queueing buffer size for very large N

Output queueing buffer size for various N and load 0.8 and 0.9 Shared buffering buffer size for various N and load 0.8 and 0.9

Buffer space requirements comparison for shared buffering versus output queueing

Crosspoint (Distributed) Queueing

Block-Crosspoint Queueing: Distributed Shared Buffers

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