Network Topologies

Shared Memory Architectures

System Bus

Communication pathway that allows various components within a computer system to communicate with each other.

• Serves as a central conduit through which data, instructions, and control signals are transmitted between the CPU (Central Processing Unit), memory, input/output devices, and other subsystems
• Multiple processors and cores of a single processor communicate through the system bus
• CS301: Topologies | Saylor Academy

Multistage Omega Network

• Most common multistage interconnects

• Stages lie in the middle while processors and memory modules are connected on the sides

• Calculations

  • Stages = $\log p$
  • Nodes = $\frac{p}{2}\times \log p$
  • Costs = $p\times \log p$

Distributed Memory Architectures

Linear Array

• Each node has two neighbours, connected to left and right.
• Movement can be done from left to right or right to left

K-d Meshes

• Each node has four neighbours
• Movement can be done to north, south, east or west

Hypercube

• Based on the mathematical concept of an n-dimensional hypercube
• Each node has $\log p$ neighbours
• The distance between any two neighbours is at most $\log p$
• d-dimensional hypercubes can be constructed by connecting corresponding nodes of multiple (d-1) dimensional hypercubes

Tree Based Network

• One path between any pair of nodes
• Linear Arrays are a special case of a tree based network

Fat Tree

• A node can communicate to the other node through the root node
• There exists higher traffic at the root node

Evaluation

Cost

• Number of links for communication

• Lower values are favourable

• Example

  • Cost of a Linear Array is $p-1$

Diameter

• Shortest distance between the two most farthest node in the network
• Lower values are favourable

Bisection Width

• Minimum number of wires required to cut / remove in order to divide the network into two equal parts
• Higher values are favourable

Arc Connectivity

• The minimum number of arcs / links that should be cut down in order to separate a single node from the network