Question

For any multimedia applications, describe how Quality of Service (QoS) guarantees for available bandwidth, delay, jitter and loss rate with DiffServ and IntServ? Highlight the issues with suitable diagrams.

Answer 1

Typically traditional networks were designed to service

specific kind of traffic, like telecommunication networks

which carry voice or computer networks which transmit data and cable networks for video transfer. But today multiservice capacity of connection between two terminals as the most popular term for that is (bps). Throughput slightly differs from bandwidth as it stands for effective bandwidth that is provided by network.

Delay or latency: It specifies the time it takes for a packet

to leave source until reaching the destination. Applications and network devices can cause delay.

Jitter (delay variation): Jitter is an interval between

subsequent packets. It is occurred by network congestion, route alternation and etc.

Loss: It is amount of packets out of all that are not received at destination. The success of QOS depends on this factor.

Reliability: Some applications are sensitive to packet loss

such as real-time applications. Thus there must be some

mechanism either in application or network to minimize the packet loss, such as forward error correction (FEC).Availability and continuity of service: This parameter talks about the user satisfaction level of service. Some of the most important ones are:

Frame size: It is the size of image on the screen. The

bigger the frame size the more bandwidth it requires. QOS

can define the frame size.

Frame rate: It refers to frames per unit of time which sent

to network higher frame rate needs more bandwidth.

Image clarity: It is user perception of quality of received

image.

Audio clarity: It specifies the rate of audio recording or

emitting per unit of time. Higher audio quality demands

higher rate.

IntServ

This solution of QOS was developed by demand of

interactive applications. It performs QOS with the use of

resource reservation and admission control mechanisms.

IntServ relies on Resource Reservation Protocol (RSVP) to

request expected QOS requirement from network and reserve

bandwidth. If reservation attempt succeeds application can

begin the communication, if not application may reduce its essentials to meet the agreement with network. IntServ

assures network QOS metrics such as bandwidth, loss and delay so it can be named Hard QOS.

Strengths and shortcomings of IntServ:

Explicit admission control: It guarantees that actual

request resources will be dedicatedly delivered to the

applicant.

Application coordination: This mechanism ease the

communication by using dynamic port numbers to

answer the application request in case of request

denial application can lower its expectations and

resend the request.

Non-scalable architecture: Because of increasing

overhead of continuous signaling and controlling

flows due to RSVP stateful architecture, IntServ is

not suitable for enterprise networks.

All the devices along the path between end points

must be RSVP enabled to satisfy required QOS.