1 / 7

Available Bandwidth Measurement

Available Bandwidth Measurement. and the Obstacles to Overcome Accurate Measurement. Definitions. Available Bandwidth (AB): The rate a which packets can be sent through the network. AB is limited by two factors: Bottleneck : The minimum rate we can send packets (static)

abeni
Download Presentation

Available Bandwidth Measurement

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Available Bandwidth Measurement and the Obstacles to Overcome Accurate Measurement

  2. Definitions • Available Bandwidth (AB): The rate a which packets can be sent through the network. AB is limited by two factors: • Bottleneck: The minimum rate we can send packets (static) • Congestion: The amount of competing traffic (dynamic) • Throughput: Amount of data actually received

  3. Common Tools for Measuring AB • Pathchar: Estimates physical bandwidth of hop-to-hop links • Pathload: Estimates AB • Netest: Measures end-to-end achievable throughput and AB, also analyzes cross traffic • bprobe/cprobe/tccp: Measure achievable throughput • Ping: First & simplest, measures round trip time

  4. AB Measurement Difficulties • Packet dispersions techniques can be intrusive to a system • Traffic congestion in the network can cause packets to be lost and false measurements • Network bandwidth has become faster than system I/O

  5. More Complex Limitations • System Interrupts • System interrupt flooding • Interrupt coalescence • System Time Resolution • Packets come in faster that the system can time stamp them • System Calls • Overhead time required to do them

  6. Measurement Algorithms & Limitations • Variable Packet Size (VPS) • Use size and hop differential methods to estimate physical bandwidth • Accuracy limited by cross traffic • Packet Pair Dispersion (PPD) • Separation between packets remains after bottleneck • Accuracy limited by cross traffic, no interrupt coalescing • Packet Train • Can determine amount of cross traffic • Measures hop-by-hop link capacity beyond bottleneck (each routers bandwidth)

  7. Future Issue • Network speeds are growing faster than CPU clock speeds and memory speeds • Host will become the bottleneck

More Related