Network Computingwww.networkcomputing.com

Does QoS Deliver?

Posted by Mike DeMaria
September 01, 2003

Tags: Asset Management, Content Management, Data Center Infrastructure, Data Management and Storage, Data Networking & Management, Electronics, Fault Tolerance, Fault Tolerant Systems, HASH, Hardware and Infrastructure, Infrastructure, Load Balancing and Performance, Network Management and Monitoring, Networking, Networking and Telecom, Networks, Other, Root Cause Analysis, Software and Web Development, Systems Management and Monitoring, Traffic Management, WAN Optimization and Application Acceleration

Channel: Other, Networking & Mgmt, WAN & App Acceleration, Content Management

Getting Jittery

There are four major reasons for implementing QoS:

• Latency, the amount of time it takes for a packet to get from one place to another, may be caused by bandwidth saturation, lack of resources (CPU or RAM) on a network device, distance or type of connection. You can reduce latency only so much--there's no way to send a message and receive a reply via a satellite link in less than 500 ms, for example.

• Jitter refers to the variance in latency. Unless two nodes are on the same switch, latency will vary greatly from packet to packet. When network bandwidth is saturated, jitter increases. For applications such as file downloads or Web browsing, this is not usually a big deal. However, streaming video and VoIP suffer greatly from high jitter. QoS can be used to help even out jitter by giving streaming traffic a higher bandwidth priority. Another solution is to increase buffer size.

• Random packet loss, which occurs when networks or devices are oversaturated, causes clipping in streaming media, reset and dropped connections, and other transaction difficulties. Worse, dropped packets need to be retransmitted, compounding the problem. QoS methods can limit the amount of bandwidth a protocol or connection uses, thus preventing or limiting oversaturation.

Related Reading

More data-networking-management Insights