QoS | Quality of Service

- Quality of Service is QoS
- QoS was not important before networks converged
- networks converged: constant small packet voice flow competes with burstly data flow, critical traffic must get priority, voice & video are time sensitive, brief outages not acceptable

- before implement QoS: burstly data flow (tried to grab as much bw as it could at any give time), first-com first served access (data rate available depend number of users accessing), mostly not time sensitive - delays ok, brief outages are survivable

- converged networks quality issues:
.lack of bandwidth: multiple flows compete for a limited amount of bandwidth (upgrade, forward important packets first, compress payload of layer 2 frame, compress ip packet headers)
.end-to-end delay (fixed & variable): packets have to traverse many network devices & links that add up to the overall delay
.variation of delay (jitter is delta): sometimes there is a lot of other traffic, which results in more delay
.packet loss: packets may have to be dropped when a link is congested