Explain the purpose of QoS on a TCP/IP network. Define the basic purpose of IP prece- dence, Type of Service, Diffserv, and Explicit Congestion Notification functionality. Give examples of how you might use QoS characteristics on your network.

Explanation:

1.The purpose of Quality of Service (QoS) is to scrutinize and control the data traffic on a network (LAN or WAN). It is an IP concept and uses tools that have existed since the early days of IP plus newer tools and protocols that are designed to aid the provision of defined predictable data transfer characteristics.

2.It defined a mechanism for assigning a priority to each IP packet as well as a mechanism to request specific treatment such as high throughput, high reliability or low latency. In practice, only the IP Precedence part of the field was ever used.IP Precedence. When the IP Precedence type of service is enabled and a device or application upstream of the switch sets the precedence bits in the ToS byte of IPv4 packet headers, the switch uses these precedence bits to determine the outbound port queue to which the packet is sent.

3.Differentiated services. ... Differentiated services or DiffServ is a computer networking architecture that specifies a simple and scalable mechanism for classifying and managing network traffic and providing quality of service (QoS) on modern IP networks.

4.The DiffServ framework is more scalable than IntServ because it handles flow aggregates and minimizes signaling, thus avoiding the complexity of per-flow soft states at each node.

5. DiffServ can, for example, be used to provide low-latency to critical network traffic such as voice or streaming media while providing simple best-effort service to non-critical services such as web traffic or file transfers.

DiffServ uses a 6-bit differentiated services code point (DSCP) in the 8-bit differentiated services field (DS field) in the IP header for packet classification purposes. The DS field replaces the outdated IPv4 TOS field.[1]

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