QoS and Congestion Flashcards
Monitoring the system for QoS
Determine where and when congestion occurs. Pass info to where action can be taken. Adjust system operation to correct problem.
QoS Skip
use Label Switching or MPLS for good QoS, Integrated services, or Differentiated services.
A flow
Stream of packets from source to destination
Why do we need flow
Due to bandwidth, jitter and delay
Retransmissions
used to restore lost data partially
When an application can enhance network service
Network requirements are less demanding than application requirements
Buffering packets at receiver
Reduce jitter
Jitter
Variations in delay or packet arrival times. Easily noticed on audio or video.
Why can video sustain lost frames
they go unnoticed if they aren’t in abundance
Networks support different categories of QoS
Constant bitrate, Realtime variable bitrate, Non realtime variable bitrate, Available bitrate.
Guarantee high QoS
design a network with enough capacity for traffic. Overprovisioning and expensive. Low latency and no loss. Best performance.
A network with less requirements can still match this using QoS techniques
Issues to address to help QoS
What application requires from a network. How to control traffic entering network. How to make resource reservations at router. If extra traffic can be accommodated safely on network.
Load shedding
removes excess load
Link Bandwidth
Network must apportion bandwidth between different flows.
Queue Space
Defines which packets should be dropped
When too much traffic is offered
congestion sets in and performance degrades sharply.